The Werner Syndrome Helicase/Exonuclease (WRN) Disrupts and Degrades D-Loops in Vitro†
Identifieur interne : 001A53 ( Istex/Corpus ); précédent : 001A52; suivant : 001A54The Werner Syndrome Helicase/Exonuclease (WRN) Disrupts and Degrades D-Loops in Vitro†
Auteurs : David K. Orren ; Shaji Theodore ; Amrita MachweSource :
- Biochemistry [ 0006-2960 ] ; 2002.
Abstract
The loss of function of WRN, a DNA helicase and exonuclease, causes the premature aging disease Werner syndrome. A hallmark feature of cells lacking WRN is genomic instability typified by elevated illegitimate recombination events and accelerated loss of telomeric sequences. In this study, the activities of WRN were examined on a displacement loop (D-loop) DNA substrate that mimics an intermediate formed during the strand invasion step of many recombinational processes. Our results indicate that this model substrate is specifically bound by WRN and efficiently disrupted by its helicase activity. In addition, the 3‘ end of the inserted strand of this D-loop structure is readily attacked by the 3‘→5‘ exonuclease function of WRN. These results indicate that D-loop structures are favored sites for WRN action. Thus, WRN may participate in DNA metabolic processes that utilize these structures, such as recombination and telomere maintenance pathways.
Url:
DOI: 10.1021/bi0266986
Links to Exploration step
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<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title>The Werner Syndrome Helicase/Exonuclease (WRN) Disrupts and Degrades D-Loops in Vitro†</title><author><name sortKey="Orren, David K" sort="Orren, David K" uniqKey="Orren D" first="David K." last="Orren">David K. Orren</name><affiliation><mods:affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</mods:affiliation></affiliation><affiliation><mods:affiliation> To whom correspondence should be addressed. Telephone: 859-323-3612. Fax: 859-323-1059. E-mail: dkorre2@pop.uky.edu.</mods:affiliation></affiliation></author><author><name sortKey="Theodore, Shaji" sort="Theodore, Shaji" uniqKey="Theodore S" first="Shaji" last="Theodore">Shaji Theodore</name><affiliation><mods:affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</mods:affiliation></affiliation></author><author><name sortKey="Machwe, Amrita" sort="Machwe, Amrita" uniqKey="Machwe A" first="Amrita" last="Machwe">Amrita Machwe</name><affiliation><mods:affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:D06E0453D1A3D13C6BD2799B983FF0D18FE29E94</idno><date when="2002" year="2002">2002</date><idno type="doi">10.1021/bi0266986</idno><idno type="url">https://api.istex.fr/ark:/67375/TPS-SBXVLNJ0-C/fulltext.pdf</idno><idno type="wicri:Area/Istex/Corpus">001A53</idno><idno type="wicri:explorRef" wicri:stream="Istex" wicri:step="Corpus" wicri:corpus="ISTEX">001A53</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a" type="main">The Werner Syndrome Helicase/Exonuclease (WRN) Disrupts and Degrades
D-Loops in Vitro<ref type="bib" target="#bi0266986AF2"><hi rend="superscript">†</hi></ref></title><author><name sortKey="Orren, David K" sort="Orren, David K" uniqKey="Orren D" first="David K." last="Orren">David K. Orren</name><affiliation><mods:affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</mods:affiliation></affiliation><affiliation><mods:affiliation> To whom correspondence should be addressed. Telephone: 859-323-3612. Fax: 859-323-1059. E-mail: dkorre2@pop.uky.edu.</mods:affiliation></affiliation></author><author><name sortKey="Theodore, Shaji" sort="Theodore, Shaji" uniqKey="Theodore S" first="Shaji" last="Theodore">Shaji Theodore</name><affiliation><mods:affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</mods:affiliation></affiliation></author><author><name sortKey="Machwe, Amrita" sort="Machwe, Amrita" uniqKey="Machwe A" first="Amrita" last="Machwe">Amrita Machwe</name><affiliation><mods:affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j" type="main">Biochemistry</title><title level="j" type="abbrev">Biochemistry</title><idno type="ISSN">0006-2960</idno><idno type="eISSN">1520-4995</idno><imprint><publisher>American Chemical Society</publisher><date type="e-published">2002</date><date type="published">2002</date><biblScope unit="vol">41</biblScope><biblScope unit="issue">46</biblScope><biblScope unit="page" from="13483">13483</biblScope><biblScope unit="page" to="13488">13488</biblScope></imprint><idno type="ISSN">0006-2960</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0006-2960</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract">The loss of function of WRN, a DNA helicase and exonuclease, causes the premature aging disease Werner syndrome. A hallmark feature of cells lacking WRN is genomic instability typified by elevated illegitimate recombination events and accelerated loss of telomeric sequences. In this study, the activities of WRN were examined on a displacement loop (D-loop) DNA substrate that mimics an intermediate formed during the strand invasion step of many recombinational processes. Our results indicate that this model substrate is specifically bound by WRN and efficiently disrupted by its helicase activity. In addition, the 3‘ end of the inserted strand of this D-loop structure is readily attacked by the 3‘→5‘ exonuclease function of WRN. These results indicate that D-loop structures are favored sites for WRN action. Thus, WRN may participate in DNA metabolic processes that utilize these structures, such as recombination and telomere maintenance pathways.</div></front></TEI><istex><corpusName>acs</corpusName><keywords><teeft><json:string>exonuclease</json:string><json:string>helicase</json:string><json:string>fmol</json:string><json:string>recombination</json:string><json:string>dnase</json:string><json:string>telomere</json:string><json:string>bubble substrate</json:string><json:string>pathway</json:string><json:string>flap</json:string><json:string>exonuclease activity</json:string><json:string>oligomer</json:string><json:string>emsa</json:string><json:string>duplex</json:string><json:string>recq</json:string><json:string>oligomers</json:string><json:string>unwinding</json:string><json:string>helicase activity</json:string><json:string>assay</json:string><json:string>biochemistry</json:string><json:string>phenotype</json:string><json:string>experimental procedure</json:string><json:string>syndrome</json:string><json:string>exonuclease assay</json:string><json:string>nucleic acid</json:string><json:string>substrate fmol</json:string><json:string>hypersensitive site</json:string><json:string>werner syndrome</json:string><json:string>telomeric</json:string><json:string>datum</json:string><json:string>telomeric sequence</json:string><json:string>early step</json:string><json:string>model substrate</json:string><json:string>exonuclease domain</json:string><json:string>unwinding assay</json:string><json:string>strand exit</json:string><json:string>many recombination pathway</json:string><json:string>werner syndrome protein</json:string><json:string>syndrome protein</json:string><json:string>strand</json:string></teeft></keywords><author><json:item><name>ORREN David K.</name><affiliations><json:string>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</json:string><json:string>To whom correspondence should be addressed. 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In this study, the activities of WRN were examined on a displacement loop (D-loop) DNA substrate that mimics an intermediate formed during the strand invasion step of many recombinational processes. Our results indicate that this model substrate is specifically bound by WRN and efficiently disrupted by its helicase activity. In addition, the 3‘ end of the inserted strand of this D-loop structure is readily attacked by the 3‘→5‘ exonuclease function of WRN. These results indicate that D-loop structures are favored sites for WRN action. 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D-Loops in Vitro<ref type="bib" target="#bi0266986AF2"><hi rend="superscript">†</hi></ref></title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher>American Chemical Society</publisher><availability><licence>Copyright © 2002 American Chemical Society</licence><p>American Chemical Society</p></availability><date type="published">2002</date><date type="Copyright" when="2002">2002</date></publicationStmt><notesStmt><note type="content-type" source="rapid-communication" scheme="https://content-type.data.istex.fr/ark:/67375/XTP-S9SX2MFS-0">brief-communication</note><note type="publication-type" scheme="https://publication-type.data.istex.fr/ark:/67375/JMC-0GLKJH51-B">journal</note></notesStmt><sourceDesc><biblStruct><analytic><title level="a" type="main">The Werner Syndrome Helicase/Exonuclease (WRN) Disrupts and Degrades
D-Loops in Vitro<ref type="bib" target="#bi0266986AF2"><hi rend="superscript">†</hi></ref></title><author xml:id="author-0000" role="corresp"><persName><surname>Orren</surname><forename type="first">David K.</forename></persName><affiliation><orgName type="institution">Graduate Center for Toxicology</orgName><orgName type="institution">University of Kentucky</orgName><address><addrLine>Lexington</addrLine><addrLine>Kentucky 40536</addrLine></address></affiliation><affiliation role="corresp"> To whom correspondence should be addressed. Telephone: 859-323-3612. Fax: 859-323-1059. E-mail: dkorre2@pop.uky.edu.</affiliation></author><author xml:id="author-0001"><persName><surname>Theodore</surname><forename type="first">Shaji</forename></persName><affiliation><orgName type="institution">Graduate Center for Toxicology</orgName><orgName type="institution">University of Kentucky</orgName><address><addrLine>Lexington</addrLine><addrLine>Kentucky 40536</addrLine></address></affiliation></author><author xml:id="author-0002"><persName><surname>Machwe</surname><forename type="first">Amrita</forename></persName><affiliation><orgName type="institution">Graduate Center for Toxicology</orgName><orgName type="institution">University of Kentucky</orgName><address><addrLine>Lexington</addrLine><addrLine>Kentucky 40536</addrLine></address></affiliation></author><idno type="istex">D06E0453D1A3D13C6BD2799B983FF0D18FE29E94</idno><idno type="ark">ark:/67375/TPS-SBXVLNJ0-C</idno><idno type="DOI">10.1021/bi0266986</idno></analytic><monogr><title level="j" type="main">Biochemistry</title><title level="j" type="abbrev">Biochemistry</title><idno type="acspubs">bi</idno><idno type="coden">bichaw</idno><idno type="pISSN">0006-2960</idno><idno type="eISSN">1520-4995</idno><imprint><publisher>American Chemical Society</publisher><date type="e-published">2002</date><date type="published">2002</date><biblScope unit="vol">41</biblScope><biblScope unit="issue">46</biblScope><biblScope unit="page" from="13483">13483</biblScope><biblScope unit="page" to="13488">13488</biblScope></imprint></monogr></biblStruct></sourceDesc></fileDesc><encodingDesc><schemaRef type="ODD" url="https://xml-schema.delivery.istex.fr/tei-istex.odd"></schemaRef><appInfo><application ident="pub2tei" version="1.0.41" when="2020-04-06"><label>pub2TEI-ISTEX</label><desc>A set of style sheets for converting XML documents encoded in various scientific publisher formats into a common TEI format.
<ref target="http://www.tei-c.org/">We use TEI</ref></desc></application></appInfo></encodingDesc><profileDesc><abstract><p>The loss of function of WRN, a DNA helicase and exonuclease, causes the premature aging
disease Werner syndrome. A hallmark feature of cells lacking WRN is genomic instability typified by
elevated illegitimate recombination events and accelerated loss of telomeric sequences. In this study, the
activities of WRN were examined on a displacement loop (D-loop) DNA substrate that mimics an
intermediate formed during the strand invasion step of many recombinational processes. Our results indicate
that this model substrate is specifically bound by WRN and efficiently disrupted by its helicase activity.
In addition, the 3‘ end of the inserted strand of this D-loop structure is readily attacked by the 3‘→5‘
exonuclease function of WRN. These results indicate that D-loop structures are favored sites for WRN
action. Thus, WRN may participate in DNA metabolic processes that utilize these structures, such as
recombination and telomere maintenance pathways.
</p></abstract><textClass ana="subject"><keywords scheme="document-type-name"><term>Accelerated Publication</term></keywords></textClass><langUsage><language ident="en"></language></langUsage></profileDesc><revisionDesc><change when="2020-04-06" who="#istex" xml:id="pub2tei">formatting</change></revisionDesc></teiHeader></istex:fulltextTEI></fulltext><metadata><istex:metadataXml wicri:clean="corpus acs not found" wicri:toSee="no header"><istex:xmlDeclaration>version="1.0" encoding="UTF-8"</istex:xmlDeclaration><istex:document><article article-type="rapid-communication" specific-use="acs2jats-1.1.23" dtd-version="1.1d1"><front><journal-meta><journal-id journal-id-type="acspubs">bi</journal-id><journal-id journal-id-type="coden">bichaw</journal-id><journal-title-group><journal-title>Biochemistry</journal-title><abbrev-journal-title>Biochemistry</abbrev-journal-title></journal-title-group><issn pub-type="ppub">0006-2960</issn><issn pub-type="epub">1520-4995</issn><publisher><publisher-name>American Chemical Society</publisher-name></publisher><self-uri>pubs.acs.org/biochemistry</self-uri></journal-meta><article-meta><article-id pub-id-type="doi">10.1021/bi0266986</article-id><article-categories><subj-group subj-group-type="document-type-name"><subject>Accelerated Publication</subject></subj-group></article-categories><title-group><article-title>The Werner Syndrome Helicase/Exonuclease (WRN) Disrupts and Degrades
D-Loops in Vitro<xref rid="bi0266986AF2"><sup>†</sup></xref></article-title></title-group><contrib-group><contrib contrib-type="author" corresp="yes"><name name-style="western"><surname>Orren</surname><given-names>David K.</given-names></name><xref rid="bi0266986AF1">*</xref></contrib><contrib contrib-type="author"><name name-style="western"><surname>Theodore</surname><given-names>Shaji</given-names></name></contrib><contrib contrib-type="author"><name name-style="western"><surname>Machwe</surname><given-names>Amrita</given-names></name></contrib><aff>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536
</aff></contrib-group><author-notes><corresp id="bi0266986AF1">
To whom correspondence should be addressed. Telephone: 859-323-3612. Fax: 859-323-1059. E-mail: dkorre2@pop.uky.edu.</corresp></author-notes><pub-date pub-type="epub"><day>22</day><month>10</month><year>2002</year></pub-date><pub-date pub-type="ppub"><day>19</day><month>11</month><year>2002</year></pub-date><volume>41</volume><issue>46</issue><fpage>13483</fpage><lpage>13488</lpage><history><date date-type="received"><day>21</day><month>08</month><year>2002</year></date><date date-type="rev-recd"><day>25</day><month>09</month><year>2002</year></date><date date-type="asap"><day>22</day><month>10</month><year>2002</year></date><date date-type="issue-pub"><day>19</day><month>11</month><year>2002</year></date></history><permissions><copyright-statement>Copyright © 2002 American Chemical Society</copyright-statement><copyright-year>2002</copyright-year><copyright-holder>American Chemical Society</copyright-holder></permissions><abstract><p>The loss of function of WRN, a DNA helicase and exonuclease, causes the premature aging
disease Werner syndrome. A hallmark feature of cells lacking WRN is genomic instability typified by
elevated illegitimate recombination events and accelerated loss of telomeric sequences. In this study, the
activities of WRN were examined on a displacement loop (D-loop) DNA substrate that mimics an
intermediate formed during the strand invasion step of many recombinational processes. Our results indicate
that this model substrate is specifically bound by WRN and efficiently disrupted by its helicase activity.
In addition, the 3‘ end of the inserted strand of this D-loop structure is readily attacked by the 3‘→5‘
exonuclease function of WRN. These results indicate that D-loop structures are favored sites for WRN
action. Thus, WRN may participate in DNA metabolic processes that utilize these structures, such as
recombination and telomere maintenance pathways.
</p></abstract><custom-meta-group><custom-meta><meta-name>document-id-old-9</meta-name><meta-value>bi0266986</meta-value></custom-meta></custom-meta-group></article-meta><notes id="bi0266986AF2"><label>†</label><p>
This work was supported in part by funds provided by Grant NS-008900 from the Ellison Medical Foundation and Grant 85-001-13-IRG from the American Cancer Society (to D.K.O.).</p></notes></front><body><sec id="d7e123"><title></title><p>Werner syndrome (WS)<xref rid="bi0266986b00001" ref-type="bibr"></xref> is an autosomal recessive disease
characterized by early onset and increased frequency of age-related maladies including atherosclerosis, cataracts, and
cancer (reviewed in refs <italic toggle="yes">1 </italic>and<italic toggle="yes"> 2</italic>). Cells derived from WS
patients display genomic instability typified by increased
deletions, insertions, and translocations (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00003" ref-type="bibr"></xref>, <xref rid="bi0266986b00004" ref-type="bibr"></xref></named-content></italic>) as well as
accelerated shortening of telomeric sequences (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00005" ref-type="bibr"></xref>, <xref rid="bi0266986b00006" ref-type="bibr"></xref></named-content></italic>). Amazingly, the accelerated aging phenotype of WS is caused by
defects in a single gene, known as <italic toggle="yes">WRN</italic>, that encodes a
protein with homology to the RecQ family of nucleic acid
helicases (<italic toggle="yes"><xref rid="bi0266986b00007" ref-type="bibr"></xref></italic>). In general, RecQ helicase deficiencies result
in increased illegitimate recombination events, suggesting
roles for these proteins in normal recombination or perhaps
anti-recombinogenic pathways (<italic toggle="yes"><xref rid="bi0266986b00008" ref-type="bibr"></xref></italic>).
</p><p>Purified WRN protein has been shown to have DNA-dependent ATPase and unwinding (3‘ → 5‘ directionality)
activities consistent with its RecQ classification (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00009" ref-type="bibr"></xref>, <xref rid="bi0266986b00010" ref-type="bibr"></xref></named-content></italic>). WRN
helicase acts on a variety of DNA structures but seems to
be directed preferentially to junctions between single- and
double-stranded DNA (<italic toggle="yes"><xref rid="bi0266986b00011" ref-type="bibr"></xref></italic>). However, WRN also harbors a
3‘→5‘ exonuclease activity unique among the five human
RecQ members (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00012" ref-type="bibr"></xref>, <xref rid="bi0266986b00013" ref-type="bibr"></xref></named-content></italic>). Interestingly, all of the mutations
described in WS patients truncate WRN prior to its C-terminal nuclear localization signal and likely result in the
inability of mutant proteins to even enter the nucleus (<italic toggle="yes"><xref rid="bi0266986b00001" ref-type="bibr"></xref></italic>).
Thus, the WS syndrome phenotype may be due to loss of
both helicase and exonuclease activities.
</p><p>An early step in many recombination pathways is invasion
of single-stranded DNA (frequently containing a 3‘ end) into
a homologous duplex to form a displacement loop (D-loop)
structure (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00014" ref-type="bibr"></xref>, <xref rid="bi0266986b00015" ref-type="bibr"></xref></named-content></italic>). Within the D-loop structure, the junctions
between single- and double-stranded DNA and the available
3‘ end are potential sites for WRN helicase and exonuclease
activities, respectively. To address this possibility, we
examined the DNA binding and catalytic activities of WRN
on a specially constructed D-loop substrate. Importantly,
D-loop structures are specifically and stably bound with high
affinity by WRN and efficiently disrupted by WRN helicase
activity. Moreover, the invading strand in the D-loop is
readily attacked and degraded from its 3‘ end by the
exonuclease activity of WRN. Our results are consistent with
a role for WRN in processing of D-loop intermediates that
arise during DNA metabolism.
</p></sec><sec id="d7e181"><title>Experimental Procedures</title><p><italic toggle="yes">WRN Purification. </italic>Both wild-type and mutant WRN
proteins used in this study were overproduced and purified
as previously described (<italic toggle="yes"><xref rid="bi0266986b00016" ref-type="bibr"></xref></italic>). The WRN-E84A mutant has a
glutamate to alanine mutation at amino acid 84 in the
exonuclease domain. This mutation abolishes exonuclease
activity, but helicase activity is retained (<italic toggle="yes"><xref rid="bi0266986b00017" ref-type="bibr"></xref></italic>).
</p><p><italic toggle="yes">DNA Substrates</italic>. Oligonucleotides were purchased from
Integrated DNA Technologies (Coralville, IA) and Operon
(Alameda, CA). In 5‘ to 3‘ orientation, oligonucleotide
sequences were FD80 (
AGCTCCTAGGGTTACAAGCTTCACTAGGGTTGTCCTTAGGGTTAGGGTTAGGGTTACCTACACATGTAGGGTTGATCAGC), DL80-D (AGCTCCTAGGGTTACAAGCTTCACTAGGGTTGTCCAGTCACAGTCAGAGTCACA GTCCTACACATGTAGGGTTGATCAGC), DL80-P (GCTGATCAACCCTACATGTGTAGGTAACCCTAACCCTAACCCTAAGGACAACCCTAGTGAAGCTTGTAACCCTAGGAGCT), INV5‘A15 (AAAAAAAAAAAAAAATTAGGGTTAGGGTTAGGGTTA),
INV (TTAGGGTTAGGGTTAGGGTTA), and INV3‘A15
(TTAGGGTTAGGGTTAGGGTTAAAAAAAAAAA AAAAA). For exonuclease assays, some substrates were constructed with DL80-P and DL80-D oligomers containing PO<sub>4</sub>
groups at the 3‘ ends. Phosphorothioate linkage was introduced between the 5‘ end and 5‘ penultimate nucleotides of
all the above oligonucleotides to prevent the 5‘→3‘ nuclease
activity of a minor contaminant present in some WRN
preparations. Where indicated, oligonucleotides were radiolabeled at their 5‘ terminus with [γ-<sup>32</sup>P]ATP (3000 Ci/mmol),
and T4 polynucleotide kinase, 3‘-phosphatase free (Roche
Molecular Biochemicals, Indianapolis, IN), and unincorporated radionucleotides were removed using standard methods.
A 2-fold excess of unlabeled FD80 or DL80-D was annealed
to labeled DL80-P to form fully duplex or bubble substrates,
respectively, by heating at 90 °C for 5 min and slow cooling
to 25 °C. Duplex and bubble substrates were separated from
excess single-stranded oligomers by native polyacrylamide
(12%) gel electrophoresis (PAGE), recovered using a gel
extraction kit (Qiagen, Valencia, CA), and stored in 10 mM
Tris-HCl, pH 8.0 at 4 °C. To form D-loop substrates,
equimolar amounts of oligonucleotide INV5‘A15, INV, or
INV3‘A15 (unlabeled or labeled as described above) were
annealed to the bubble substrate by heating the mixture to
70 °C for 15 min and slowly cooling to 25 °C. Correct
annealing of the substrates was confirmed by individual
digestions with the restriction enzymes <italic toggle="yes">Hin</italic>dIII, <italic toggle="yes">Bfa</italic>I, and
<italic toggle="yes">Nsp</italic>I followed by inspection of DNA products after PAGE.
</p><p><italic toggle="yes">DNA Unwinding Assay.</italic> For unwinding assays, the bubble
substrate constructed with labeled DL80-P oligomer was used
with or without an annealed, labeled INV5‘A15, INV, or
INV3‘A15 oligomer. Bubble and D-loop substrates (0.25−1.0 fmol) were incubated with WRN-E84A (0.38−12 fmol)
in WRN buffer [40 mM Tris-HCl (pH 8.0), 4 mM MgCl<sub>2</sub>,
0.1 mg/mL bovine serum albumin, and 5 mM dithiothreitol]
for 15 min at 37 °C in the presence of ATP (1 mM).
Reactions were stopped with one-sixth volume of helicase
stop dye [30% glycerol, 50 mM EDTA, 0.9% SDS, 0.25%
bromphenol blue (BPB), and 0.25% xylene cyanol (XC)].
The DNA products were then separated by 8% PAGE. Gels
were vacuum-dried and analyzed using a Storm 860 Phosphorimager and ImageQuant software (Molecular Dynamics,
Sunnyvale, CA). Quantitation of D-loop unwinding was
determined by comparing amounts of labeled INV5‘A15 or
INV oligomer displaced with total amounts of the same
oligomer present in the untreated D-loop.
</p><p><italic toggle="yes">Exonuclease Assay.</italic> For the exonuclease assay, the DL80-P
and DL80-D oligomers had 3‘-PO<sub>4</sub> modifications, and both
DL80-P and INV5‘A15 (36 nt) oligomers were labeled.
D-loop substrates (1.2 fmol) were incubated for 1 h at 37
°C with wild-type WRN (1−8 fmol) or WRN-E84A (5−45
fmol) in WRN buffer without ATP. Reactions were stopped
with equal volumes of formamide dyes (95% formamide,
20 mM EDTA, 0.1% BPB, and 0.1% XC). DNA products
were heat-denatured, run on denaturing 14% PAGE, and
analyzed as above.
</p><p><italic toggle="yes">Electrophoretic Mobility Shift Assay (EMSA).</italic> DNA substrates for EMSA were constructed using labeled DL80-P
with unlabeled FD80 or DL80-D and annealing unlabeled
INV5‘A15 when needed to form the D-loop substrate. Fully
duplex, bubble, and D-loop substrates (0.6 fmol) were
incubated 30 min at 4 °C with wild-type WRN (9−90 fmol)
in WRN buffer plus 0.1% Nonidet P-40 and ATPγS (1 mM).
After addition of one-sixth volume of native dye (30%
glycerol, 0.25% BPB, and 0.25% XC), DNA and DNA−protein complexes were separated at 4 °C by 4% PAGE and
analyzed as above. Binding was quantitated by comparing
the amount of unbound DNA with the total DNA in the
reaction (% DNA<sub>bound</sub> = [(DNA<sub>total</sub> − DNA<sub>unbound</sub>)/DNA<sub>total</sub>]
× 100).
</p><p><italic toggle="yes">DNase I Footprinting.</italic> Bubble and D-loop substrates for
DNase I footprinting analysis were as described for the
exonuclease assay, except the D-loop substrate was made
with unlabeled INV5‘A15 oligomer. DNA substrates (2.4
fmol) were incubated with wild-type WRN (3−36 fmol) in
WRN buffer plus ATPγS (1 mM) for 30 min at 4 °C,
followed by 10 min at 4 °C with DNase I (1 unit). Reactions
were stopped and treated as for the exonuclease assay.
Nucleotide size markers were created as described previously
(<italic toggle="yes"><xref rid="bi0266986b00017" ref-type="bibr"></xref></italic>). The binding affinity of WRN to bubble and D-loop
substrates was compared by measuring (via phosphorimaging
analysis) the disappearance of specific bands from the DNase
I digestion pattern with increasing WRN concentration.
</p></sec><sec id="d7e253"><title>Results</title><p>An early step in many recombination pathways is invasion
of a single-stranded DNA with a 3‘ end into a homologous
duplex to form a D-loop structure (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00014" ref-type="bibr"></xref>, <xref rid="bi0266986b00015" ref-type="bibr"></xref></named-content></italic>). To investigate a
potential role for WRN in metabolism of these structures, a
model substrate was constructed by first annealing partially
complementary 80 nt oligomers to form a duplex with a 21
nt bubble and then annealing a third (invading) strand to
form a D-loop at the site of the bubble (Figure <xref rid="bi0266986f00001"></xref>A).
Formation of the proposed D-loop structure was confirmed
by its retarded migration on nondenaturing gels and the
complete cleavage of the 35 and 24 bp arms by restriction
endonucleases (Figure <xref rid="bi0266986f00001"></xref>B).
<fig id="bi0266986f00001" position="float" orientation="portrait"><label>1</label><caption><p>D-loop substrate structure. (A) Sequence and structure of the D-loop substrate. The partially complementary DL80-P (paired) and DL80-D (displaced) oligomer sequences are in bold and the INV5‘A15 (invading) oligomer is in lightly shaded type, with lengths of the duplex arms and D-loop region noted. Selected restriction enzyme recognition sequences and their incision sites are denoted by dashed boxes and arrowheads [solid for those sites utilized in (B)], respectively. As evidenced by DNase I footprinting (see Figure <xref rid="bi0266986f00002"></xref>C), the region of WRN binding to the DL80-P strand of this substrate is indicated by right angle brackets (solid and dashed lines denoting observed and putative areas of binding, respectively), and the associated DNase I hypersensitive sites are designated by arrows. (B) D-loop substrate structure analysis. After complete annealing, the D-loop substrate was digested by<italic toggle="yes">Nsp</italic>I, <italic toggle="yes">Bfa</italic>I, or <italic toggle="yes">Hin</italic>dIII, and products were separated by
8% PAGE along with unrestricted (UR) D-loop and bubble substrates. The positions of the D-loop, the bubble substrate, and the <italic toggle="yes">Nsp</italic>I
fragment are denoted at the left, with positions of radiolabels indicated by asterisks.</p></caption><graphic xlink:href="bi0266986f00001.tif" position="float" orientation="portrait"></graphic></fig></p><p>First, WRN binding to the D-loop substrate was examined
by EMSA and DNase I protection assays. By EMSA, WRN
binds to the D-loop substrate with higher affinity (more than
2-fold at limiting WRN concentration) than to the comparable
bubble substrate without the inserted strand (Figure <xref rid="bi0266986f00002"></xref>A,B).
These DNA−protein complexes contain WRN, as they are
supershifted by WRN-specific antibodies (data not shown).
Using this EMSA method, WRN does not detectably bind
to a fully duplex substrate (Figure <xref rid="bi0266986f00002"></xref>A) or to substrates
containing simple forks, 3‘ or 5‘ single-stranded overhangs,
and only single-stranded DNA (data not shown). These data
indicate that WRN binds strongly and specifically to the
bubble and D-loop structures with no detectable affinity for
sequences within the substrate. DNase I protection assays
were used to pinpoint the region of the substrate that was
bound by WRN. WRN protected part of one strand (DL80-P) that formed the duplex part of the D-loop structure and
elicited multiple DNase I hypersensitive sites on the 35 bp
arm 4−8 nt from the D-loop junction (Figure <xref rid="bi0266986f00002"></xref>C). The WRN
footprint and associated DNase I hypersensitive sites on the
DL80-P strand of the D-loop substrate are mapped on the
substrate diagram (see Figure <xref rid="bi0266986f00001"></xref>A). When compared to the
bubble substrate, the protected area on the D-loop substrate
is smaller (10−20 nt) and shifted toward the 35 bp arm
(Figure <xref rid="bi0266986f00002"></xref>C). These data suggest that WRN binds, at least in
part, to the point where the invading strand exits the D-loop
structure, although we cannot rule out the possibility that
WRN might also bind to the displaced (DL80-D) strand.
Over a limiting range of WRN concentration (6−18 fmol),
a higher percentage of D-loop than bubble substrate was
bound by WRN, as assessed by disappearance of specific
bands (indicated by asterisks) from the DNase I digestion
pattern. Thus, both EMSA and footprinting assays suggest
that D-loop structures are preferred even over bubble
structures previously shown to be high-affinity substrates for
WRN binding (<italic toggle="yes"><xref rid="bi0266986b00017" ref-type="bibr"></xref></italic>).
<fig id="bi0266986f00002" position="float" orientation="portrait"><label>2</label><caption><p>High-affinity WRN binding to the D-loop substrate. (A) DNA and DNA−protein complexes of wild-type WRN (15−90 fmol) with the D-loop, bubble, or duplex substrate were prepared and analyzed by EMSA as described in Experimental Procedures. The positions of WRN−DNA complexes and bubble and D-loop substrates are denoted. (B) Graphic representation of WRN binding to D-loop (·) and bubble (▪) substrates, generated by EMSA [as visualized in (A)]. The amount of DNA substrate bound was determined from disappearance of the free DNA band. Data points are the mean of two independent experiments, except for values at 9 fmol of WRN. (C) Wild-type WRN (3−36 fmol) binding to D-loop (left) and bubble (right) substrates (both labeled on the DL80-P “paired” oligomer) analyzed by DNase I footprinting as described in Experimental Procedures. The lengths and positions of nucleotide markers are noted, as are the bounds of bubble and D-loop regions (curved bracket) and WRN “footprints” (right-angle brackets). Arrows mark DNase I hypersensitive sites caused by WRN binding to the D-loop substrate. Asterisks denote bands used to assess the relative binding of WRN to D-loop and bubble substrates.</p></caption><graphic xlink:href="bi0266986f00002.tif" position="float" orientation="portrait"></graphic></fig></p><p>WRN has both DNA unwinding and 3‘→5‘ exonuclease
activities; either (or both) could potentially disrupt D-loop
structures. To specifically examine unwinding, assays were
carried out with WRN-E84A mutant protein that lacks
exonuclease but retains helicase activity (<italic toggle="yes"><xref rid="bi0266986b00017" ref-type="bibr"></xref></italic>). WRN-E84A
was able to efficiently displace the invading strand of our
substrate, converting the D-loop into a bubble (Figure <xref rid="bi0266986f00003"></xref>A)
in a reaction requiring ATP hydrolysis. The bubble structure
was not unwound here, although much higher WRN concentrations (>60 fmol) can unwind these structures (<italic toggle="yes"><xref rid="bi0266986b00017" ref-type="bibr"></xref></italic>).
Since WRN does bind single-stranded DNA (<italic toggle="yes"><xref rid="bi0266986b00016" ref-type="bibr"></xref></italic>), the 5‘
single-stranded flap of the invading strand could be mediating
unwinding. To address this possibility, another D-loop
substrate was formed with the invading strand not having a
5‘ flap, i.e, in which all 21 nt are paired with the DL80-P
strand. WRN-E84A disrupted this substrate without the 5‘
flap at least as well as the original D-loop substrate (Figure
<xref rid="bi0266986f00003"></xref>B,C), indicating that a 5‘ flap on the invading strand plays
no part in WRN-mediated disruption of D-loops. Another
D-loop substrate with a 3‘ single-stranded flap on the inserted
strand was similarly disrupted (data not shown). Significant
levels of unwinding occur at WRN concentrations that are
nearly equimolar to the DNA substrate, attesting to the
extreme efficiency of this reaction. These results indicate
that the D-loop structure itself mediates the heightened
substrate binding and displacement of the invading strand
by WRN helicase.
<fig id="bi0266986f00003" position="float" orientation="portrait"><label>3</label><caption><p>WRN-catalyzed unwinding of the D-loop substrate. (A) Reactions containing the bubble (labeled on the DL80-P oligomer) or D-loop (labeled on DL80-P and INV5‘A15 oligomers) substrate (1 fmol) with or without exonuclease-deficient WRN-E84A (12 fmol) were analyzed for unwinding as described in Experimental Procedures. The positions of the D-loop, the bubble substrate, and DL80-P (80 nt) and INV5‘A15 (36 nt) oligomers are denoted. (▴) substrates denatured by heating. (B) D-loop substrates (0.25 fmol) were constructed using labeled DL80-P with either labeled INV5‘A15 (D-loop + 5‘ flap) or labeled INV (D-loop − 5‘ flap) oligomer and then subjected to the unwinding assay using WRN-E84A (0.38−3 fmol) as described in Experimental Procedures. The positions of the D-loop containing a 5‘ flap, bubble substrate, and INV5‘A15 (36 nt) and G21 (21 nt) oligomers are denoted at the left, with the D-loop without the 5‘ flap noted at the right. (C) Quantitation of data presented in (B), comparing the amount of unwinding of the D-loop with (▪) and without a 5‘ flap (·).</p></caption><graphic xlink:href="bi0266986f00003.tif" position="float" orientation="portrait"></graphic></fig></p><p>The invading strand of D-loop structures may have a 3‘
end that could be a putative target for the 3‘→5‘ exonuclease
activity of WRN. Likewise, the inserted strand of our D-loop
substrate has a 3‘ end in a comparable orientation. However,
unlike physiological D-loop structures, our model substrate
has two additional 3‘ ends on each duplex arm (see Figure
<xref rid="bi0266986f00001"></xref>A) that might be attacked by WRN exonuclease. Indeed,
the blunt ends of bubble substrates (without an inserted
strand) are efficiently digested by WRN exonuclease (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00017" ref-type="bibr"></xref>,
<xref rid="bi0266986b00018" ref-type="bibr"></xref></named-content></italic>). To avoid digestion at these sites, substrate was assembled with both 80-mers modified with PO<sub>4</sub> at the 3‘ end,
while the invading, radiolabeled 36-mer contained the normal
3‘-OH group. Importantly, DNA strands ending in 3‘-PO<sub>4</sub>
groups are highly resistant to WRN exonuclease activity.<xref rid="bi0266986b00002" ref-type="bibr"></xref>
Thus, this substrate can be used to examine WRN exonuclease activity specifically on the 3‘ end of the invading
strand. Exonuclease assays were carried out in the absence
of ATP to prevent WRN helicase activity. Wild-type WRN
did not detectably degrade the labeled DL80-P strand (80
nt) (Figure <xref rid="bi0266986f00004"></xref>), confirming that its 3‘-PO<sub>4</sub> end prevents
exonuclease attack. In sharp contrast, the invading strand
(36 nt) was digested from its 3‘ end in a stepwise fashion
(Figure <xref rid="bi0266986f00004"></xref>, left). This activity is inherent to WRN, as WRN-E84A exonuclease mutant does not degrade this substrate
(Figure <xref rid="bi0266986f00004"></xref>, right). Thus, in the context of a D-loop, the 3‘
end of the invading strand can be efficiently recognized and
degraded by WRN exonuclease. Notably, both helicase and
exonuclease activities are manifested on this D-loop substrate
over roughly the same range of WRN concentration (compare
Figures <xref rid="bi0266986f00003"></xref> and <xref rid="bi0266986f00004"></xref>), suggesting that the binding affinity of WRN
may underlie the heightened efficiency of each activity.
<fig id="bi0266986f00004" position="float" orientation="portrait"><label>4</label><caption><p>WRN exonuclease activity on the D-loop substrate. The D-loop substrate was constructed by annealing labeled INV5‘A15 (containing the standard 3‘-OH group) into the bubble substrate constructed from DL80-D and labeled DL80-P, both containing 3‘-PO<sub>4</sub> ends. This substrate was incubated with either wild-type WRN
(left, 1−8 fmol) or WRN-E84A (right, 5−45 fmol) in the absence
of ATP to prevent unwinding, and DNA products were analyzed
as described in Experimental Procedures. The positions of undigested DL80-P (80 nt) and INV5‘A15 (36 nt) oligomers are denoted.
</p></caption><graphic xlink:href="bi0266986f00004.tif" position="float" orientation="portrait"></graphic></fig></p></sec><sec id="d7e353"><title>Discussion</title><p>The genomic instability phenotypes of WS and other RecQ
helicase-deficient conditions are suggestive of defective
recombination or anti-recombination pathways (<italic toggle="yes"><xref rid="bi0266986b00008" ref-type="bibr"></xref></italic>). A potential role for WRN in such pathways was assessed by
examining its DNA binding, unwinding, and exonuclease
activities on a D-loop substrate that approximates the
structure formed during the strand invasion step of many
recombination pathways. Our results indicate that WRN
binds with high affinity to this substrate specifically in the
region of the D-loop. This level of binding appears to be
conferred by the structure of the D-loop, as WRN has lower
affinity for bubble substrate without the inserted strand and
no detectable affinity for a fully duplex DNA. The manner
in which WRN binds to the D-loop substrate is markedly
different than WRN binding to the same substrate without
the inserted strand. When compared with the footprint of
WRN on the bubble substrate, the D-loop footprint is more
compact, with strong DNase I hypersensitive sites on the 35
bp duplex arm just 3‘ to the D-loop structure on the DL80-P
strand. The position of the footprint indicates that WRN binds
(at least in part) near the junction where the invading strand
exits the duplex. Both WRN helicase and exonuclease acted
very efficiently on the D-loop substrate. The helicase activity
of WRN easily dislodged the invading strand from the rest
of the substrate, regardless of whether it contained a single-stranded flap 5‘ or 3‘ to the region of insertion. The efficient
disruption of our D-loop substrate indicates that WRN
translocation along single-stranded DNA 3‘ to the duplex to
be unwound is not required, consistent with a recent report
(<italic toggle="yes"><xref rid="bi0266986b00011" ref-type="bibr"></xref></italic>) that WRN helicase may be targeted directly to junctions
between single- and double-stranded DNA. However, stable
binding to simple forked structures (as determined by EMSA)
has not been demonstrated without the use of protein−DNA
cross-linking agents, suggesting that D-loop structures form
a much more stable binding site for WRN. Finally, the 3‘→5‘
exonuclease activity of WRN recognizes the 3‘ end of the
invading strand of the D-loop and digests it efficiently,
distributively, and independently of ATP binding, ATP
hydrolysis, and DNA unwinding. Intriguingly, this 3‘ end,
near the forked region at the proximal side of the 24 bp arm
(see Figure <xref rid="bi0266986f00001"></xref>A), is very accessible to WRN's exonuclease
domain. Taken together, our assays suggest that WRN may
be spatially oriented on this D-loop substrate with its
exonuclease domain positioned at the 3‘ end of the invading
strand and the helicase domain at the junction where the
invading strand exits the duplex. Although here we examined
WRN helicase and exonuclease activities separately for ease
of interpretation, their combined action might be expected
to further enhance disruption of D-loops and similar structures. However, it is also possible that either helicase or
exonuclease activity may predominate in specific situations.
</p><p>These results are consistent with the notion that D-loop
structures might be particularly susceptible to the catalytic
activities of WRN in vivo. Strand invasion and D-loop
formation is an early step in recombination pathways, and
many recombinational D-loops are believed to be formed
by invasion of 3‘ single-stranded overhangs into homologous
duplex DNA (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00014" ref-type="bibr"></xref>, <xref rid="bi0266986b00015" ref-type="bibr"></xref></named-content></italic>). In such a structure, the 3‘ end within
the D-loop may also serve as a primer for DNA polymerases.
The ability of WRN to disrupt and degrade D-loops may
indicate a function in recombination or anti-recombination
pathways. By way of its unwinding and/or exonuclease
activities, WRN could serve to reverse D-loop formation and
inhibit recombination. Conversely, once a recombination
intermediate is formed, the helicase activity of WRN may
facilitate Holliday structure branch migration as reported
previously (<italic toggle="yes"><xref rid="bi0266986b00019" ref-type="bibr"></xref></italic>). Defects in WRN and other RecQ helicases
result in illegitimate and hyper-recombination phenotypes
(<italic toggle="yes">1</italic>,<italic toggle="yes"> 2</italic>,<italic toggle="yes"> 8</italic>), consistent with possible roles of these proteins in
suppressing recombination, perhaps through disruption of
D-loop intermediates. In this regard, BLM, the human RecQ
member deficient in Bloom syndrome, also binds and
disrupts D-loop structures (<italic toggle="yes"><xref rid="bi0266986b00020" ref-type="bibr"></xref></italic>).
</p><p>Recent studies have indicated that D-loop structures occur
in telomeric regions (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00021" ref-type="bibr"></xref>, <xref rid="bi0266986b00022" ref-type="bibr"></xref></named-content></italic>), potentially serving either to
sequester and protect the linear ends of chromosomes (<italic toggle="yes"><xref rid="bi0266986b00023" ref-type="bibr"></xref></italic>)
or to facilitate telomere elongation by the ALT (alternative
lengthening of telomeres) recombinational pathway (<italic toggle="yes"><xref rid="bi0266986b00024" ref-type="bibr"></xref></italic>).
Accelerated telomere shortening is also a key part of the
genomic instability phenotype of WS, suggesting a role for
WRN in telomere metabolism (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00005" ref-type="bibr"></xref>, <xref rid="bi0266986b00006" ref-type="bibr"></xref></named-content></italic>). In support of this
notion, WRN interacts functionally and physically with Ku
(<italic toggle="yes"><xref rid="bi0266986b00025" ref-type="bibr"></xref></italic>), a heterodimeric complex that is, in part, associated with
telomeres (<italic toggle="yes"><xref rid="bi0266986b00026" ref-type="bibr"></xref></italic>). WRN also colocalizes with telomeric factors
in cells utilizing the ALT pathway (<italic toggle="yes"><xref rid="bi0266986b00027" ref-type="bibr"></xref></italic>), suggesting a specific
role for WRN in telomere lengthening by recombination. As
mentioned above, the WRN branch migrates Holliday
junctions and may also facilitate recombination by unwinding
unusual structures formed by repetitive telomeric sequences
prior to or during strand exchange and branch migration
steps. In this regard, WRN unwinds branched and G-quartet
structures constructed from DNA containing telomeric
repeats (<italic toggle="yes"><named-content content-type="bibref-group"><xref rid="bi0266986b00028" ref-type="bibr"></xref>, <xref rid="bi0266986b00029" ref-type="bibr"></xref></named-content></italic>). We speculate that the accelerated loss of
telomeric sequences in WRN-deficient cells may be due to
an inability to process telomeric D-loop or other related
structures. Thus, the complete genomic instability phenotype
observed in WS may be related to the inability to process
D-loops formed during telomere metabolism and/or recombination, although further investigation is needed to support
this hypothesis.
</p></sec></body><back><ack><title>Acknowledgments</title><p>The authors thank Liren Xiao for expert technical assistance and Dr. Zhigang Wang for critical reading of the
manuscript.
</p></ack><ref-list><title>References</title><ref id="bi0266986b00001"><element-citation publication-type="journal"><name name-style="western"><surname>Oshima</surname><given-names>J.</given-names></name><article-title>The Werner syndrome protein: an update</article-title><source>BioEssays</source><year>2000</year><volume>22</volume><fpage>894</fpage><lpage>901</lpage><pub-id pub-id-type="doi">10.1002/1521-1878(200010)22:10%3C894::AID-BIES4%3E3.0.CO;2-B</pub-id></element-citation></ref><ref id="bi0266986b00002"><element-citation publication-type="journal"><name name-style="western"><surname>Furuichi</surname><given-names>Y.</given-names></name><article-title>Premature aging and predisposition to cancers caused by mutations in RecQ family helicases</article-title><source>Ann. N.Y. Acad. Sci.</source><year>2001</year><volume>928</volume><fpage>121</fpage><lpage>131</lpage></element-citation></ref><ref id="bi0266986b00003"><element-citation publication-type="journal"><name name-style="western"><surname>Fukuchi</surname><given-names>K.</given-names></name><name name-style="western"><surname>Martin</surname><given-names>G. M.</given-names></name><name name-style="western"><surname>Monnat</surname><given-names>R. J.</given-names></name><article-title>Mutator phenotype of Werner syndrome is characterized by extensive deletions</article-title><source>Proc. Natl. Acad. Sci. U.S.A.</source><year>1989</year><volume>86</volume><fpage>5893</fpage><lpage>5897</lpage><pub-id pub-id-type="doi">10.1073/pnas.86.15.5893</pub-id></element-citation></ref><ref id="bi0266986b00004"><element-citation publication-type="journal"><name name-style="western"><surname>Stefanini</surname><given-names>M.</given-names></name><name name-style="western"><surname>Scappaticci</surname><given-names>S.</given-names></name><name name-style="western"><surname>Lagomarsini</surname><given-names>P.</given-names></name><name name-style="western"><surname>Borroni</surname><given-names>G.</given-names></name><name name-style="western"><surname>Berardesca</surname><given-names>E.</given-names></name><name name-style="western"><surname>Nuzzo</surname><given-names>F.</given-names></name><article-title>Chromosome instability in lymphocytes from a patient with Werner's syndrome is not associated with DNA repair defects</article-title><source>Mutat. Res.</source><year>1989</year><volume>219</volume><fpage>179</fpage><lpage>185</lpage></element-citation></ref><ref id="bi0266986b00005"><element-citation publication-type="journal"><name name-style="western"><surname>Schulz</surname><given-names>V. P.</given-names></name><name name-style="western"><surname>Zakian</surname><given-names>V. A.</given-names></name><name name-style="western"><surname>Ogburn</surname><given-names>C. E.</given-names></name><name name-style="western"><surname>McKay</surname><given-names>J.</given-names></name><name name-style="western"><surname>Jarzebowicz</surname><given-names>A. A.</given-names></name><name name-style="western"><surname>Edland</surname><given-names>S. D.</given-names></name><name name-style="western"><surname>Martin</surname><given-names>G. M.</given-names></name><article-title>Accelerated loss of telomeric repeats may not explain accelerated replicative decline of Werner syndrome cells</article-title><source>Hum. Genet.</source><year>1996</year><volume>97</volume><fpage>750</fpage><lpage>754</lpage><pub-id pub-id-type="doi">10.1007/BF02346184</pub-id></element-citation></ref><ref id="bi0266986b00006"><element-citation publication-type="journal"><name name-style="western"><surname>Tahara</surname><given-names>H.</given-names></name><name name-style="western"><surname>Tokutake</surname><given-names>Y.</given-names></name><name name-style="western"><surname>Maeda</surname><given-names>S.</given-names></name><name name-style="western"><surname>Kataoka</surname><given-names>H.</given-names></name><name name-style="western"><surname>Watanabe</surname><given-names>T.</given-names></name><name name-style="western"><surname>Satoh</surname><given-names>M.</given-names></name><name name-style="western"><surname>Matsumoto</surname><given-names>T.</given-names></name><name name-style="western"><surname>Sugawara</surname><given-names>M.</given-names></name><name name-style="western"><surname>Ide</surname><given-names>T.</given-names></name><name name-style="western"><surname>Goto</surname><given-names>M.</given-names></name><name name-style="western"><surname>Furuichi</surname><given-names>Y.</given-names></name><name name-style="western"><surname>Sugimoto</surname><given-names>M.</given-names></name><article-title>Abnormal telomere dynamics of B-lymphoblastoid cell strains from Werner's syndrome patients transformed by Epstein-Barr virus</article-title><source>Oncogene</source><year>1997</year><volume>15</volume><fpage>1911</fpage><lpage>1920</lpage><pub-id pub-id-type="doi">10.1038/sj.onc.1201377</pub-id></element-citation></ref><ref id="bi0266986b00007"><element-citation publication-type="journal"><name name-style="western"><surname>Yu</surname><given-names>C. E.</given-names></name><name name-style="western"><surname>Oshima</surname><given-names>J.</given-names></name><name name-style="western"><surname>Fu</surname><given-names>Y. H.</given-names></name><name name-style="western"><surname>Hisama</surname><given-names>F.</given-names></name><name name-style="western"><surname>Wijsman</surname><given-names>E. M.</given-names></name><name name-style="western"><surname>Alisch</surname><given-names>R.</given-names></name><name name-style="western"><surname>Matthews</surname><given-names>S.</given-names></name><name name-style="western"><surname>Nakura</surname><given-names>J.</given-names></name><name name-style="western"><surname>Miki</surname><given-names>T.</given-names></name><name name-style="western"><surname>Ouais</surname><given-names>S.</given-names></name><name name-style="western"><surname>Martin</surname><given-names>G. M.</given-names></name><name name-style="western"><surname>Mulligan</surname><given-names>J.</given-names></name><name name-style="western"><surname>Schellenberg</surname><given-names>G. D.</given-names></name><article-title>Positional cloning of the Werner ‘s syndrome gene</article-title><source>Science</source><year>1996</year><volume>272</volume><fpage>258</fpage><lpage>262</lpage><pub-id pub-id-type="doi">10.1126/science.272.5259.258</pub-id></element-citation></ref><ref id="bi0266986b00008"><element-citation publication-type="journal"><name name-style="western"><surname>Karow</surname><given-names>J. K.</given-names></name><name name-style="western"><surname>Wu</surname><given-names>L.</given-names></name><name name-style="western"><surname>Hickson</surname><given-names>I. D.</given-names></name><article-title>RecQ family helicases: roles in cancer and aging</article-title><source>Curr. Opin. Genet. Dev.</source><year>2000</year><volume>10</volume><fpage>32</fpage><lpage>38</lpage><pub-id pub-id-type="doi">10.1016/S0959-437X(99)00039-8</pub-id></element-citation></ref><ref id="bi0266986b00009"><element-citation publication-type="journal"><name name-style="western"><surname>Shen</surname><given-names>J. C.</given-names></name><name name-style="western"><surname>Gray</surname><given-names>M. D.</given-names></name><name name-style="western"><surname>Oshima</surname><given-names>J.</given-names></name><name name-style="western"><surname>Loeb</surname><given-names>L. A.</given-names></name><article-title>Characterization of Werner syndrome protein DNA helicase activity: directionality, substrate dependence, and stimulation by replication protein A</article-title><source>Nucleic Acids Res.</source><year>1998</year><volume>26</volume><fpage>2879</fpage><lpage>2885</lpage><pub-id pub-id-type="doi">10.1093/nar/26.12.2879</pub-id></element-citation></ref><ref id="bi0266986b00010"><element-citation publication-type="journal"><name name-style="western"><surname>Brosh</surname><given-names>R. M.</given-names><suffix>Jr.</suffix></name><name name-style="western"><surname>Orren</surname><given-names>D. K.</given-names></name><name name-style="western"><surname>Nehlin</surname><given-names>J. O.</given-names></name><name name-style="western"><surname>Ravn</surname><given-names>P. H.</given-names></name><name name-style="western"><surname>Kenny</surname><given-names>M. K.</given-names></name><name name-style="western"><surname>Machwe</surname><given-names>A.</given-names></name><name name-style="western"><surname>Bohr</surname><given-names>V. A.</given-names></name><article-title>Functional and physical interaction between WRN helicase and human replication protein A</article-title><source>J. Biol. Chem.</source><year>1999</year><volume>274</volume><fpage>18341</fpage><lpage>18350</lpage><pub-id pub-id-type="doi">10.1074/jbc.274.26.18341</pub-id></element-citation></ref><ref id="bi0266986b00011"><element-citation publication-type="journal"><name name-style="western"><surname>Brosh</surname><given-names>R. M.</given-names></name><name name-style="western"><surname>Waheed</surname><given-names>J.</given-names></name><name name-style="western"><surname>Sommers</surname><given-names>J. A.</given-names></name><article-title>Biochemical characterization of the DNA substrate specificity of Werner syndrome helicase</article-title><source>J. Biol. Chem.</source><year>2002</year><volume>277</volume><fpage>23236</fpage><lpage>23245</lpage><pub-id pub-id-type="doi">10.1074/jbc.M111446200</pub-id></element-citation></ref><ref id="bi0266986b00012"><element-citation publication-type="journal"><name name-style="western"><surname>Huang</surname><given-names>S.</given-names></name><name name-style="western"><surname>Li</surname><given-names>B.</given-names></name><name name-style="western"><surname>Gray</surname><given-names>M. D.</given-names></name><name name-style="western"><surname>Oshima</surname><given-names>J.</given-names></name><name name-style="western"><surname>Mian</surname><given-names>I. S.</given-names></name><name name-style="western"><surname>Campisi</surname><given-names>J.</given-names></name><article-title>The premature aging syndrome protein, WRN, is a 3‘→5‘ exonuclease</article-title><source>Nat. Genet.</source><year>1998</year><volume>20</volume><fpage>114</fpage><lpage>116</lpage><pub-id pub-id-type="doi">10.1038/2410</pub-id></element-citation></ref><ref id="bi0266986b00013"><element-citation publication-type="journal"><name name-style="western"><surname>Shen</surname><given-names>J. C.</given-names></name><name name-style="western"><surname>Gray</surname><given-names>M. D.</given-names></name><name name-style="western"><surname>Oshima</surname><given-names>J.</given-names></name><name name-style="western"><surname>Kamath-Loeb</surname><given-names>A. S.</given-names></name><name name-style="western"><surname>Fry</surname><given-names>M.</given-names></name><name name-style="western"><surname>Loeb</surname><given-names>L. A.</given-names></name><article-title>Werner syndrome protein. I. DNA helicase and exonuclease reside on the same polypeptide</article-title><source>J. Biol. Chem.</source><year>1998</year><volume>273</volume><fpage>34145</fpage><lpage>34150</lpage><pub-id pub-id-type="doi">10.1074/jbc.273.51.34145</pub-id></element-citation></ref><ref id="bi0266986b00014"><element-citation publication-type="journal"><name name-style="western"><surname>Haber</surname><given-names>J. E.</given-names></name><article-title>DNA recombination: the replication connection</article-title><source>Trends Biochem. Sci.</source><year>1999</year><volume>24</volume><fpage>271</fpage><lpage>275</lpage><pub-id pub-id-type="doi">10.1016/S0968-0004(99)01413-9</pub-id></element-citation></ref><ref id="bi0266986b00015"><element-citation publication-type="journal"><name name-style="western"><surname>Kowalczykowski</surname><given-names>S. C.</given-names></name><article-title>Initiation of genetic recombination and recombination-dependent replication</article-title><source>Trends Biochem. Sci.</source><year>2000</year><volume>25</volume><fpage>156</fpage><lpage>165</lpage><pub-id pub-id-type="doi">10.1016/S0968-0004(00)01569-3</pub-id></element-citation></ref><ref id="bi0266986b00016"><element-citation publication-type="journal"><name name-style="western"><surname>Orren</surname><given-names>D. K.</given-names></name><name name-style="western"><surname>Brosh</surname><given-names>R. M.</given-names></name><name name-style="western"><surname>Nehlin</surname><given-names>J. O.</given-names></name><name name-style="western"><surname>Machwe</surname><given-names>A.</given-names></name><name name-style="western"><surname>Gray</surname><given-names>M. D.</given-names></name><name name-style="western"><surname>Bohr</surname><given-names>V. A.</given-names></name><article-title>Enzymatic and DNA binding properties of purified WRN protein: high affinity binding to single-stranded DNA but not to DNA damage induced by 4NQO</article-title><source>Nucleic Acids Res.</source><year>1999</year><volume>27</volume><fpage>3557</fpage><lpage>3566</lpage><pub-id pub-id-type="doi">10.1093/nar/27.17.3557</pub-id></element-citation></ref><ref id="bi0266986b00017"><element-citation publication-type="journal"><name name-style="western"><surname>Machwe</surname><given-names>A.</given-names></name><name name-style="western"><surname>Xiao</surname><given-names>L.</given-names></name><name name-style="western"><surname>Theodore</surname><given-names>S.</given-names></name><name name-style="western"><surname>Orren</surname><given-names>D. K.</given-names></name><article-title>DNase I footprinting and enhanced exonuclease function of the bipartite Werner syndrome protein (WRN) bound to partially melted duplex DNA</article-title><source>J. Biol. Chem.</source><year>2002</year><volume>277</volume><fpage>4492</fpage><lpage>4504</lpage><pub-id pub-id-type="doi">10.1074/jbc.M108880200</pub-id></element-citation></ref><ref id="bi0266986b00018"><element-citation publication-type="journal"><name name-style="western"><surname>Shen</surname><given-names>J. C.</given-names></name><name name-style="western"><surname>Loeb</surname><given-names>L. A.</given-names></name><article-title>Werner syndrome exonuclease catalyzes structure-dependent degradation of DNA</article-title><source>Nucleic Acids Res.</source><year>2000</year><volume>28</volume><fpage>3260</fpage><lpage>3268</lpage><pub-id pub-id-type="doi">10.1093/nar/28.17.3260</pub-id></element-citation></ref><ref id="bi0266986b00019"><element-citation publication-type="journal"><name name-style="western"><surname>Constantinou</surname><given-names>A.</given-names></name><name name-style="western"><surname>Tarsounas</surname><given-names>M.</given-names></name><name name-style="western"><surname>Karow</surname><given-names>J. K.</given-names></name><name name-style="western"><surname>Brosh</surname><given-names>R. M.</given-names></name><name name-style="western"><surname>Bohr</surname><given-names>V. A.</given-names></name><name name-style="western"><surname>Hickson</surname><given-names>I. D.</given-names></name><name name-style="western"><surname>West</surname><given-names>S. C.</given-names></name><article-title>Werner's syndrome protein (WRN) migrates Holliday junctions and co-localizes with RPA upon replication arrest</article-title><source>EMBO Rep.</source><year>2000</year><volume>1</volume><fpage>80</fpage><lpage>84</lpage><pub-id pub-id-type="doi">10.1093/embo-reports/kvd004</pub-id></element-citation></ref><ref id="bi0266986b00020"><element-citation publication-type="journal"><name name-style="western"><surname>Van Brabant</surname><given-names>A. J.</given-names></name><name name-style="western"><surname>Ye</surname><given-names>T.</given-names></name><name name-style="western"><surname>Sanz</surname><given-names>M.</given-names></name><name name-style="western"><surname>German</surname><given-names>J. L.</given-names></name><name name-style="western"><surname>Ellis</surname><given-names>N. A.</given-names></name><name name-style="western"><surname>Holloman</surname><given-names>W. K.</given-names></name><article-title>Binding and melting of D-loops by the Bloom syndrome helicase</article-title><source>Biochemistry</source><year>2000</year><volume>39</volume><fpage>14617</fpage><lpage>14625</lpage><pub-id pub-id-type="doi">10.1021/bi0018640</pub-id></element-citation></ref><ref id="bi0266986b00021"><element-citation publication-type="journal"><name name-style="western"><surname>Griffith</surname><given-names>J. D.</given-names></name><name name-style="western"><surname>Comeau</surname><given-names>L.</given-names></name><name name-style="western"><surname>Rosenfield</surname><given-names>S.</given-names></name><name name-style="western"><surname>Stansel</surname><given-names>R. M.</given-names></name><name name-style="western"><surname>Bianchi</surname><given-names>A.</given-names></name><name name-style="western"><surname>Moss</surname><given-names>H.</given-names></name><name name-style="western"><surname>de Lange</surname><given-names>T.</given-names></name><article-title>Mammalian telomeres end in a large duplex loop</article-title><source>Cell</source><year>1999</year><volume>97</volume><fpage>503</fpage><lpage>514</lpage><pub-id pub-id-type="doi">10.1016/S0092-8674(00)80760-6</pub-id></element-citation></ref><ref id="bi0266986b00022"><element-citation publication-type="journal"><name name-style="western"><surname>Murti</surname><given-names>K. G.</given-names></name><name name-style="western"><surname>Prescott</surname><given-names>D. M.</given-names></name><article-title>Telomeres of polytene chromosomes in a ciliated protozoan terminate in duplex DNA loops</article-title><source>Proc. Natl. Acad. Sci. U.S.A.</source><year>1999</year><volume>96</volume><fpage>14436</fpage><lpage>14439</lpage><pub-id pub-id-type="doi">10.1073/pnas.96.25.14436</pub-id></element-citation></ref><ref id="bi0266986b00023"><element-citation publication-type="journal"><name name-style="western"><surname>de Lange</surname><given-names>T.</given-names></name><article-title>Protection of mammalian telomeres</article-title><source>Oncogene</source><year>2002</year><volume>21</volume><fpage>532</fpage><lpage>540</lpage><pub-id pub-id-type="doi">10.1038/sj.onc.1205080</pub-id></element-citation></ref><ref id="bi0266986b00024"><element-citation publication-type="journal"><name name-style="western"><surname>Lundblad</surname><given-names>V.</given-names></name><article-title>Telomere maintenance without telomerase</article-title><source>Oncogene</source><year>2002</year><volume>21</volume><fpage>522</fpage><lpage>531</lpage><pub-id pub-id-type="doi">10.1038/sj.onc.1205079</pub-id></element-citation></ref><ref id="bi0266986b00025"><element-citation publication-type="journal"><name name-style="western"><surname>Cooper</surname><given-names>M. C.</given-names></name><name name-style="western"><surname>Machwe</surname><given-names>A.</given-names></name><name name-style="western"><surname>Orren</surname><given-names>D. K.</given-names></name><name name-style="western"><surname>Brosh</surname><given-names>R. M.</given-names></name><name name-style="western"><surname>Ramsden</surname><given-names>D.</given-names></name><name name-style="western"><surname>Bohr</surname><given-names>V. A.</given-names></name><article-title>Ku complex interacts with and stimulates the Werner protein</article-title><source>Genes Dev.</source><year>2000</year><volume>14</volume><fpage>907</fpage><lpage>912</lpage></element-citation></ref><ref id="bi0266986b00026"><element-citation publication-type="journal"><name name-style="western"><surname>Hsu</surname><given-names>H. L.</given-names></name><name name-style="western"><surname>Gilley</surname><given-names>D.</given-names></name><name name-style="western"><surname>Blackburn</surname><given-names>E. H.</given-names></name><name name-style="western"><surname>Chen</surname><given-names>D. J.</given-names></name><article-title>Ku is associated with the telomere in mammals</article-title><source>Proc. Natl. Acad. Sci. U.S.A.</source><year>1999</year><volume>96</volume><fpage>12454</fpage><lpage>12458</lpage><pub-id pub-id-type="doi">10.1073/pnas.96.22.12454</pub-id></element-citation></ref><ref id="bi0266986b00027"><mixed-citation><name name-style="western"><surname>Johnson</surname><given-names>F. B.</given-names></name>, <name name-style="western"><surname>Marciniak</surname><given-names>R. A.</given-names></name>, <name name-style="western"><surname>McVey</surname><given-names>M.</given-names></name>, <name name-style="western"><surname>Stewart</surname><given-names>S. A.</given-names></name>, <name name-style="western"><surname>Hahn</surname><given-names>W. C.</given-names></name> <name name-style="western"><surname>and Guarente</surname><given-names>L.</given-names></name> (2001) The <italic toggle="yes">Saccharomyces cerevisiae</italic> WRN homologue Sgs1p participates in telomere maintenance in cells lacking telomerase, <italic toggle="yes">EMBO J.</italic> <italic toggle="yes">20</italic>, 905−913.<pub-id pub-id-type="doi">10.1093/emboj/20.4.905</pub-id></mixed-citation></ref><ref id="bi0266986b00028"><element-citation publication-type="journal"><name name-style="western"><surname>Ohsugi</surname><given-names>I.</given-names></name><name name-style="western"><surname>Tokutake</surname><given-names>Y.</given-names></name><name name-style="western"><surname>Suzuki</surname><given-names>N.</given-names></name><name name-style="western"><surname>Ide</surname><given-names>T.</given-names></name><name name-style="western"><surname>Sugimoto</surname><given-names>M.</given-names></name><name name-style="western"><surname>Furuichi</surname><given-names>Y.</given-names></name><article-title>Telomere repeat DNA forms a large noncovalent complex with unique cohesive properties which is dissociated by Werner syndrome DNA helicase in the presence of replication protein A</article-title><source>Nucleic Acids Res.</source><year>2000</year><volume>28</volume><fpage>3642</fpage><lpage>3648</lpage><pub-id pub-id-type="doi">10.1093/nar/28.18.3642</pub-id></element-citation></ref><ref id="bi0266986b00029"><element-citation publication-type="journal"><name name-style="western"><surname>Mohaghegh</surname><given-names>P.</given-names></name><name name-style="western"><surname>Karow</surname><given-names>J. K.</given-names></name><name name-style="western"><surname>Brosh</surname><given-names>R. M.</given-names></name><name name-style="western"><surname>Bohr</surname><given-names>V. A.</given-names></name><name name-style="western"><surname>Hickson</surname><given-names>I. D.</given-names></name><article-title>The Bloom's and Werner's syndrome proteins are DNA structure-specific helicases</article-title><source>Nucleic Acids Res.</source><year>2001</year><volume>29</volume><fpage>2843</fpage><lpage>2849</lpage><pub-id pub-id-type="doi">10.1093/nar/29.13.2843</pub-id></element-citation></ref><ref id="bi0266986n00001"><mixed-citation><comment>Abbreviations: WS, Werner syndrome; nt, nucleotides; PAGE, polyacrylamide gel electrophoresis; BPB, bromphenol blue; XC, xylene cyanol; EMSA, electrophoretic mobility shift assay; ATPγS, adenosine 5‘-<italic toggle="yes">O</italic>-(3-thiotriphosphate); DNase I, bovine pancreatic deoxyribonuclease I; bp, base pairs.</comment></mixed-citation></ref><ref id="bi0266986n00002"><mixed-citation><comment>A. Machwe and D. K. Orren, unpublished experiments.</comment></mixed-citation></ref></ref-list></back></article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo><title>The Werner Syndrome Helicase/Exonuclease (WRN) Disrupts and Degrades D-Loops in Vitro†</title></titleInfo><titleInfo contentType="CDATA"><title>The Werner Syndrome Helicase/Exonuclease (WRN) Disrupts and Degrades D-Loops in Vitro†</title></titleInfo><name type="personal" displayLabel="corresp"><namePart type="family">ORREN</namePart><namePart type="given">David K.</namePart><affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</affiliation><affiliation> To whom correspondence should be addressed. Telephone: 859-323-3612. Fax: 859-323-1059. E-mail: dkorre2@pop.uky.edu.</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="family">THEODORE</namePart><namePart type="given">Shaji</namePart><affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="family">MACHWE</namePart><namePart type="given">Amrita</namePart><affiliation>Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="other" displayLabel="rapid-communication" authority="ISTEX" authorityURI="https://content-type.data.istex.fr" valueURI="https://content-type.data.istex.fr/ark:/67375/XTP-7474895G-0">other</genre><originInfo><publisher>American Chemical Society</publisher><dateCreated encoding="w3cdtf">2002-10-22</dateCreated><dateIssued encoding="w3cdtf">2002-11-19</dateIssued><copyrightDate encoding="w3cdtf">2002</copyrightDate></originInfo><note type="footnote" ID="bi0266986AF2"> This work was supported in part by funds provided by Grant NS-008900 from the Ellison Medical Foundation and Grant 85-001-13-IRG from the American Cancer Society (to D.K.O.).</note><language><languageTerm type="code" authority="iso639-2b">eng</languageTerm><languageTerm type="code" authority="rfc3066">en</languageTerm></language><abstract>The loss of function of WRN, a DNA helicase and exonuclease, causes the premature aging disease Werner syndrome. A hallmark feature of cells lacking WRN is genomic instability typified by elevated illegitimate recombination events and accelerated loss of telomeric sequences. In this study, the activities of WRN were examined on a displacement loop (D-loop) DNA substrate that mimics an intermediate formed during the strand invasion step of many recombinational processes. Our results indicate that this model substrate is specifically bound by WRN and efficiently disrupted by its helicase activity. In addition, the 3‘ end of the inserted strand of this D-loop structure is readily attacked by the 3‘→5‘ exonuclease function of WRN. These results indicate that D-loop structures are favored sites for WRN action. Thus, WRN may participate in DNA metabolic processes that utilize these structures, such as recombination and telomere maintenance pathways.</abstract><note type="footnote" ID="bi0266986AF2"> This work was supported in part by funds provided by Grant NS-008900 from the Ellison Medical Foundation and Grant 85-001-13-IRG from the American Cancer Society (to D.K.O.).</note><relatedItem type="host"><titleInfo><title>Biochemistry</title></titleInfo><titleInfo type="abbreviated"><title>Biochemistry</title></titleInfo><genre type="journal" authority="ISTEX" authorityURI="https://publication-type.data.istex.fr" valueURI="https://publication-type.data.istex.fr/ark:/67375/JMC-0GLKJH51-B">journal</genre><identifier type="ISSN">0006-2960</identifier><identifier type="eISSN">1520-4995</identifier><identifier type="acspubs">bi</identifier><identifier type="coden">BICHAW</identifier><identifier type="uri">pubs.acs.org/biochemistry</identifier><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>41</number></detail><detail type="issue"><caption>no.</caption><number>46</number></detail><extent unit="pages"><start>13483</start><end>13488</end></extent></part></relatedItem><relatedItem type="references" ID="bi0266986b00001" displayLabel="bibbi0266986b00001"><titleInfo><title>The Werner syndrome protein: an update</title></titleInfo><titleInfo contentType="CDATA"><title>The Werner syndrome protein: an update</title></titleInfo><name type="personal"><namePart type="family">OSHIMA</namePart><namePart type="given">J.</namePart></name><relatedItem type="host"><titleInfo><title>BioEssays</title></titleInfo><genre>journal</genre><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>22</number></detail><extent unit="pages"><start>894</start><end>901</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00002" displayLabel="bibbi0266986b00002"><titleInfo><title>Premature aging and predisposition to cancers caused by mutations in RecQ family helicases</title></titleInfo><titleInfo contentType="CDATA"><title>Premature aging and predisposition to cancers caused by mutations in RecQ family helicases</title></titleInfo><name type="personal"><namePart type="family">FURUICHI</namePart><namePart type="given">Y.</namePart></name><relatedItem type="host"><titleInfo><title>Ann. N.Y. Acad. Sci.</title></titleInfo><genre>journal</genre><part><date>2001</date><detail type="volume"><caption>vol.</caption><number>928</number></detail><extent unit="pages"><start>121</start><end>131</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00003" displayLabel="bibbi0266986b00003"><titleInfo><title>Mutator phenotype of Werner syndrome is characterized by extensive deletions</title></titleInfo><titleInfo contentType="CDATA"><title>Mutator phenotype of Werner syndrome is characterized by extensive deletions</title></titleInfo><name type="personal"><namePart type="family">FUKUCHI</namePart><namePart type="given">K.</namePart></name><name type="personal"><namePart type="family">MARTIN</namePart><namePart type="given">G. M.</namePart></name><name type="personal"><namePart type="family">MONNAT</namePart><namePart type="given">R. J.</namePart></name><relatedItem type="host"><titleInfo><title>Proc. Natl. Acad. Sci. U.S.A.</title></titleInfo><genre>journal</genre><part><date>1989</date><detail type="volume"><caption>vol.</caption><number>86</number></detail><extent unit="pages"><start>5893</start><end>5897</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00004" displayLabel="bibbi0266986b00004"><titleInfo><title>Chromosome instability in lymphocytes from a patient with Werner's syndrome is not associated with DNA repair defects</title></titleInfo><titleInfo contentType="CDATA"><title>Chromosome instability in lymphocytes from a patient with Werner's syndrome is not associated with DNA repair defects</title></titleInfo><name type="personal"><namePart type="family">STEFANINI</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">SCAPPATICCI</namePart><namePart type="given">S.</namePart></name><name type="personal"><namePart type="family">LAGOMARSINI</namePart><namePart type="given">P.</namePart></name><name type="personal"><namePart type="family">BORRONI</namePart><namePart type="given">G.</namePart></name><name type="personal"><namePart type="family">BERARDESCA</namePart><namePart type="given">E.</namePart></name><name type="personal"><namePart type="family">NUZZO</namePart><namePart type="given">F.</namePart></name><relatedItem type="host"><titleInfo><title>Mutat. Res.</title></titleInfo><genre>journal</genre><part><date>1989</date><detail type="volume"><caption>vol.</caption><number>219</number></detail><extent unit="pages"><start>179</start><end>185</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00005" displayLabel="bibbi0266986b00005"><titleInfo><title>Accelerated loss of telomeric repeats may not explain accelerated replicative decline of Werner syndrome cells</title></titleInfo><titleInfo contentType="CDATA"><title>Accelerated loss of telomeric repeats may not explain accelerated replicative decline of Werner syndrome cells</title></titleInfo><name type="personal"><namePart type="family">SCHULZ</namePart><namePart type="given">V. P.</namePart></name><name type="personal"><namePart type="family">ZAKIAN</namePart><namePart type="given">V. A.</namePart></name><name type="personal"><namePart type="family">OGBURN</namePart><namePart type="given">C. E.</namePart></name><name type="personal"><namePart type="family">MCKAY</namePart><namePart type="given">J.</namePart></name><name type="personal"><namePart type="family">JARZEBOWICZ</namePart><namePart type="given">A. A.</namePart></name><name type="personal"><namePart type="family">EDLAND</namePart><namePart type="given">S. D.</namePart></name><name type="personal"><namePart type="family">MARTIN</namePart><namePart type="given">G. M.</namePart></name><relatedItem type="host"><titleInfo><title>Hum. Genet.</title></titleInfo><genre>journal</genre><part><date>1996</date><detail type="volume"><caption>vol.</caption><number>97</number></detail><extent unit="pages"><start>750</start><end>754</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00006" displayLabel="bibbi0266986b00006"><titleInfo><title>Abnormal telomere dynamics of B-lymphoblastoid cell strains from Werner's syndrome patients transformed by Epstein-Barr virus</title></titleInfo><titleInfo contentType="CDATA"><title>Abnormal telomere dynamics of B-lymphoblastoid cell strains from Werner's syndrome patients transformed by Epstein-Barr virus</title></titleInfo><name type="personal"><namePart type="family">TAHARA</namePart><namePart type="given">H.</namePart></name><name type="personal"><namePart type="family">TOKUTAKE</namePart><namePart type="given">Y.</namePart></name><name type="personal"><namePart type="family">MAEDA</namePart><namePart type="given">S.</namePart></name><name type="personal"><namePart type="family">KATAOKA</namePart><namePart type="given">H.</namePart></name><name type="personal"><namePart type="family">WATANABE</namePart><namePart type="given">T.</namePart></name><name type="personal"><namePart type="family">SATOH</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">MATSUMOTO</namePart><namePart type="given">T.</namePart></name><name type="personal"><namePart type="family">SUGAWARA</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">IDE</namePart><namePart type="given">T.</namePart></name><name type="personal"><namePart type="family">GOTO</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">FURUICHI</namePart><namePart type="given">Y.</namePart></name><name type="personal"><namePart type="family">SUGIMOTO</namePart><namePart type="given">M.</namePart></name><relatedItem type="host"><titleInfo><title>Oncogene</title></titleInfo><genre>journal</genre><part><date>1997</date><detail type="volume"><caption>vol.</caption><number>15</number></detail><extent unit="pages"><start>1911</start><end>1920</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00007" displayLabel="bibbi0266986b00007"><titleInfo><title>Positional cloning of the Werner ‘s syndrome gene</title></titleInfo><titleInfo contentType="CDATA"><title>Positional cloning of the Werner ‘s syndrome gene</title></titleInfo><name type="personal"><namePart type="family">YU</namePart><namePart type="given">C. E.</namePart></name><name type="personal"><namePart type="family">OSHIMA</namePart><namePart type="given">J.</namePart></name><name type="personal"><namePart type="family">FU</namePart><namePart type="given">Y. H.</namePart></name><name type="personal"><namePart type="family">HISAMA</namePart><namePart type="given">F.</namePart></name><name type="personal"><namePart type="family">WIJSMAN</namePart><namePart type="given">E. M.</namePart></name><name type="personal"><namePart type="family">ALISCH</namePart><namePart type="given">R.</namePart></name><name type="personal"><namePart type="family">MATTHEWS</namePart><namePart type="given">S.</namePart></name><name type="personal"><namePart type="family">NAKURA</namePart><namePart type="given">J.</namePart></name><name type="personal"><namePart type="family">MIKI</namePart><namePart type="given">T.</namePart></name><name type="personal"><namePart type="family">OUAIS</namePart><namePart type="given">S.</namePart></name><name type="personal"><namePart type="family">MARTIN</namePart><namePart type="given">G. M.</namePart></name><name type="personal"><namePart type="family">MULLIGAN</namePart><namePart type="given">J.</namePart></name><name type="personal"><namePart type="family">SCHELLENBERG</namePart><namePart type="given">G. D.</namePart></name><relatedItem type="host"><titleInfo><title>Science</title></titleInfo><genre>journal</genre><part><date>1996</date><detail type="volume"><caption>vol.</caption><number>272</number></detail><extent unit="pages"><start>258</start><end>262</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00008" displayLabel="bibbi0266986b00008"><titleInfo><title>RecQ family helicases: roles in cancer and aging</title></titleInfo><titleInfo contentType="CDATA"><title>RecQ family helicases: roles in cancer and aging</title></titleInfo><name type="personal"><namePart type="family">KAROW</namePart><namePart type="given">J. K.</namePart></name><name type="personal"><namePart type="family">WU</namePart><namePart type="given">L.</namePart></name><name type="personal"><namePart type="family">HICKSON</namePart><namePart type="given">I. D.</namePart></name><relatedItem type="host"><titleInfo><title>Curr. Opin. Genet. Dev.</title></titleInfo><genre>journal</genre><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>10</number></detail><extent unit="pages"><start>32</start><end>38</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00009" displayLabel="bibbi0266986b00009"><titleInfo><title>Characterization of Werner syndrome protein DNA helicase activity: directionality, substrate dependence, and stimulation by replication protein A</title></titleInfo><titleInfo contentType="CDATA"><title>Characterization of Werner syndrome protein DNA helicase activity: directionality, substrate dependence, and stimulation by replication protein A</title></titleInfo><name type="personal"><namePart type="family">SHEN</namePart><namePart type="given">J. C.</namePart></name><name type="personal"><namePart type="family">GRAY</namePart><namePart type="given">M. D.</namePart></name><name type="personal"><namePart type="family">OSHIMA</namePart><namePart type="given">J.</namePart></name><name type="personal"><namePart type="family">LOEB</namePart><namePart type="given">L. A.</namePart></name><relatedItem type="host"><titleInfo><title>Nucleic Acids Res.</title></titleInfo><genre>journal</genre><part><date>1998</date><detail type="volume"><caption>vol.</caption><number>26</number></detail><extent unit="pages"><start>2879</start><end>2885</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00010" displayLabel="bibbi0266986b00010"><titleInfo><title>Functional and physical interaction between WRN helicase and human replication protein A</title></titleInfo><titleInfo contentType="CDATA"><title>Functional and physical interaction between WRN helicase and human replication protein A</title></titleInfo><name type="personal"><namePart type="family">BROSH</namePart><namePart type="given">R. M.</namePart></name><name type="personal"><namePart type="family">ORREN</namePart><namePart type="given">D. K.</namePart></name><name type="personal"><namePart type="family">NEHLIN</namePart><namePart type="given">J. O.</namePart></name><name type="personal"><namePart type="family">RAVN</namePart><namePart type="given">P. H.</namePart></name><name type="personal"><namePart type="family">KENNY</namePart><namePart type="given">M. K.</namePart></name><name type="personal"><namePart type="family">MACHWE</namePart><namePart type="given">A.</namePart></name><name type="personal"><namePart type="family">BOHR</namePart><namePart type="given">V. A.</namePart></name><relatedItem type="host"><titleInfo><title>J. Biol. Chem.</title></titleInfo><genre>journal</genre><part><date>1999</date><detail type="volume"><caption>vol.</caption><number>274</number></detail><extent unit="pages"><start>18341</start><end>18350</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00011" displayLabel="bibbi0266986b00011"><titleInfo><title>Biochemical characterization of the DNA substrate specificity of Werner syndrome helicase</title></titleInfo><titleInfo contentType="CDATA"><title>Biochemical characterization of the DNA substrate specificity of Werner syndrome helicase</title></titleInfo><name type="personal"><namePart type="family">BROSH</namePart><namePart type="given">R. M.</namePart></name><name type="personal"><namePart type="family">WAHEED</namePart><namePart type="given">J.</namePart></name><name type="personal"><namePart type="family">SOMMERS</namePart><namePart type="given">J. A.</namePart></name><relatedItem type="host"><titleInfo><title>J. Biol. Chem.</title></titleInfo><genre>journal</genre><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>277</number></detail><extent unit="pages"><start>23236</start><end>23245</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00012" displayLabel="bibbi0266986b00012"><titleInfo><title>The premature aging syndrome protein, WRN, is a 3‘→5‘ exonuclease</title></titleInfo><titleInfo contentType="CDATA"><title>The premature aging syndrome protein, WRN, is a 3‘→5‘ exonuclease</title></titleInfo><name type="personal"><namePart type="family">HUANG</namePart><namePart type="given">S.</namePart></name><name type="personal"><namePart type="family">LI</namePart><namePart type="given">B.</namePart></name><name type="personal"><namePart type="family">GRAY</namePart><namePart type="given">M. D.</namePart></name><name type="personal"><namePart type="family">OSHIMA</namePart><namePart type="given">J.</namePart></name><name type="personal"><namePart type="family">MIAN</namePart><namePart type="given">I. S.</namePart></name><name type="personal"><namePart type="family">CAMPISI</namePart><namePart type="given">J.</namePart></name><relatedItem type="host"><titleInfo><title>Nat. Genet.</title></titleInfo><genre>journal</genre><part><date>1998</date><detail type="volume"><caption>vol.</caption><number>20</number></detail><extent unit="pages"><start>114</start><end>116</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00013" displayLabel="bibbi0266986b00013"><titleInfo><title>Werner syndrome protein. I. DNA helicase and exonuclease reside on the same polypeptide</title></titleInfo><titleInfo contentType="CDATA"><title>Werner syndrome protein. I. DNA helicase and exonuclease reside on the same polypeptide</title></titleInfo><name type="personal"><namePart type="family">SHEN</namePart><namePart type="given">J. C.</namePart></name><name type="personal"><namePart type="family">GRAY</namePart><namePart type="given">M. D.</namePart></name><name type="personal"><namePart type="family">OSHIMA</namePart><namePart type="given">J.</namePart></name><name type="personal"><namePart type="family">KAMATH-LOEB</namePart><namePart type="given">A. S.</namePart></name><name type="personal"><namePart type="family">FRY</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">LOEB</namePart><namePart type="given">L. A.</namePart></name><relatedItem type="host"><titleInfo><title>J. Biol. Chem.</title></titleInfo><genre>journal</genre><part><date>1998</date><detail type="volume"><caption>vol.</caption><number>273</number></detail><extent unit="pages"><start>34145</start><end>34150</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00014" displayLabel="bibbi0266986b00014"><titleInfo><title>DNA recombination: the replication connection</title></titleInfo><titleInfo contentType="CDATA"><title>DNA recombination: the replication connection</title></titleInfo><name type="personal"><namePart type="family">HABER</namePart><namePart type="given">J. E.</namePart></name><relatedItem type="host"><titleInfo><title>Trends Biochem. Sci.</title></titleInfo><genre>journal</genre><part><date>1999</date><detail type="volume"><caption>vol.</caption><number>24</number></detail><extent unit="pages"><start>271</start><end>275</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00015" displayLabel="bibbi0266986b00015"><titleInfo><title>Initiation of genetic recombination and recombination-dependent replication</title></titleInfo><titleInfo contentType="CDATA"><title>Initiation of genetic recombination and recombination-dependent replication</title></titleInfo><name type="personal"><namePart type="family">KOWALCZYKOWSKI</namePart><namePart type="given">S. C.</namePart></name><relatedItem type="host"><titleInfo><title>Trends Biochem. Sci.</title></titleInfo><genre>journal</genre><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>25</number></detail><extent unit="pages"><start>156</start><end>165</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00016" displayLabel="bibbi0266986b00016"><titleInfo><title>Enzymatic and DNA binding properties of purified WRN protein: high affinity binding to single-stranded DNA but not to DNA damage induced by 4NQO</title></titleInfo><titleInfo contentType="CDATA"><title>Enzymatic and DNA binding properties of purified WRN protein: high affinity binding to single-stranded DNA but not to DNA damage induced by 4NQO</title></titleInfo><name type="personal"><namePart type="family">ORREN</namePart><namePart type="given">D. K.</namePart></name><name type="personal"><namePart type="family">BROSH</namePart><namePart type="given">R. M.</namePart></name><name type="personal"><namePart type="family">NEHLIN</namePart><namePart type="given">J. O.</namePart></name><name type="personal"><namePart type="family">MACHWE</namePart><namePart type="given">A.</namePart></name><name type="personal"><namePart type="family">GRAY</namePart><namePart type="given">M. D.</namePart></name><name type="personal"><namePart type="family">BOHR</namePart><namePart type="given">V. A.</namePart></name><relatedItem type="host"><titleInfo><title>Nucleic Acids Res.</title></titleInfo><genre>journal</genre><part><date>1999</date><detail type="volume"><caption>vol.</caption><number>27</number></detail><extent unit="pages"><start>3557</start><end>3566</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00017" displayLabel="bibbi0266986b00017"><titleInfo><title>DNase I footprinting and enhanced exonuclease function of the bipartite Werner syndrome protein (WRN) bound to partially melted duplex DNA</title></titleInfo><titleInfo contentType="CDATA"><title>DNase I footprinting and enhanced exonuclease function of the bipartite Werner syndrome protein (WRN) bound to partially melted duplex DNA</title></titleInfo><name type="personal"><namePart type="family">MACHWE</namePart><namePart type="given">A.</namePart></name><name type="personal"><namePart type="family">XIAO</namePart><namePart type="given">L.</namePart></name><name type="personal"><namePart type="family">THEODORE</namePart><namePart type="given">S.</namePart></name><name type="personal"><namePart type="family">ORREN</namePart><namePart type="given">D. K.</namePart></name><relatedItem type="host"><titleInfo><title>J. Biol. Chem.</title></titleInfo><genre>journal</genre><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>277</number></detail><extent unit="pages"><start>4492</start><end>4504</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00018" displayLabel="bibbi0266986b00018"><titleInfo><title>Werner syndrome exonuclease catalyzes structure-dependent degradation of DNA</title></titleInfo><titleInfo contentType="CDATA"><title>Werner syndrome exonuclease catalyzes structure-dependent degradation of DNA</title></titleInfo><name type="personal"><namePart type="family">SHEN</namePart><namePart type="given">J. C.</namePart></name><name type="personal"><namePart type="family">LOEB</namePart><namePart type="given">L. A.</namePart></name><relatedItem type="host"><titleInfo><title>Nucleic Acids Res.</title></titleInfo><genre>journal</genre><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>28</number></detail><extent unit="pages"><start>3260</start><end>3268</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00019" displayLabel="bibbi0266986b00019"><titleInfo><title>Werner's syndrome protein (WRN) migrates Holliday junctions and co-localizes with RPA upon replication arrest</title></titleInfo><titleInfo contentType="CDATA"><title>Werner's syndrome protein (WRN) migrates Holliday junctions and co-localizes with RPA upon replication arrest</title></titleInfo><name type="personal"><namePart type="family">CONSTANTINOU</namePart><namePart type="given">A.</namePart></name><name type="personal"><namePart type="family">TARSOUNAS</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">KAROW</namePart><namePart type="given">J. K.</namePart></name><name type="personal"><namePart type="family">BROSH</namePart><namePart type="given">R. M.</namePart></name><name type="personal"><namePart type="family">BOHR</namePart><namePart type="given">V. A.</namePart></name><name type="personal"><namePart type="family">HICKSON</namePart><namePart type="given">I. D.</namePart></name><name type="personal"><namePart type="family">WEST</namePart><namePart type="given">S. C.</namePart></name><relatedItem type="host"><titleInfo><title>EMBO Rep.</title></titleInfo><genre>journal</genre><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>1</number></detail><extent unit="pages"><start>80</start><end>84</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00020" displayLabel="bibbi0266986b00020"><titleInfo><title>Binding and melting of D-loops by the Bloom syndrome helicase</title></titleInfo><titleInfo contentType="CDATA"><title>Binding and melting of D-loops by the Bloom syndrome helicase</title></titleInfo><name type="personal"><namePart type="family">VAN BRABANT</namePart><namePart type="given">A. J.</namePart></name><name type="personal"><namePart type="family">YE</namePart><namePart type="given">T.</namePart></name><name type="personal"><namePart type="family">SANZ</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">GERMAN</namePart><namePart type="given">J. L.</namePart></name><name type="personal"><namePart type="family">ELLIS</namePart><namePart type="given">N. A.</namePart></name><name type="personal"><namePart type="family">HOLLOMAN</namePart><namePart type="given">W. K.</namePart></name><relatedItem type="host"><titleInfo><title>Biochemistry</title></titleInfo><genre>journal</genre><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>39</number></detail><extent unit="pages"><start>14617</start><end>14625</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00021" displayLabel="bibbi0266986b00021"><titleInfo><title>Mammalian telomeres end in a large duplex loop</title></titleInfo><titleInfo contentType="CDATA"><title>Mammalian telomeres end in a large duplex loop</title></titleInfo><name type="personal"><namePart type="family">GRIFFITH</namePart><namePart type="given">J. D.</namePart></name><name type="personal"><namePart type="family">COMEAU</namePart><namePart type="given">L.</namePart></name><name type="personal"><namePart type="family">ROSENFIELD</namePart><namePart type="given">S.</namePart></name><name type="personal"><namePart type="family">STANSEL</namePart><namePart type="given">R. M.</namePart></name><name type="personal"><namePart type="family">BIANCHI</namePart><namePart type="given">A.</namePart></name><name type="personal"><namePart type="family">MOSS</namePart><namePart type="given">H.</namePart></name><name type="personal"><namePart type="family">DE LANGE</namePart><namePart type="given">T.</namePart></name><relatedItem type="host"><titleInfo><title>Cell</title></titleInfo><genre>journal</genre><part><date>1999</date><detail type="volume"><caption>vol.</caption><number>97</number></detail><extent unit="pages"><start>503</start><end>514</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00022" displayLabel="bibbi0266986b00022"><titleInfo><title>Telomeres of polytene chromosomes in a ciliated protozoan terminate in duplex DNA loops</title></titleInfo><titleInfo contentType="CDATA"><title>Telomeres of polytene chromosomes in a ciliated protozoan terminate in duplex DNA loops</title></titleInfo><name type="personal"><namePart type="family">MURTI</namePart><namePart type="given">K. G.</namePart></name><name type="personal"><namePart type="family">PRESCOTT</namePart><namePart type="given">D. M.</namePart></name><relatedItem type="host"><titleInfo><title>Proc. Natl. Acad. Sci. U.S.A.</title></titleInfo><genre>journal</genre><part><date>1999</date><detail type="volume"><caption>vol.</caption><number>96</number></detail><extent unit="pages"><start>14436</start><end>14439</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00023" displayLabel="bibbi0266986b00023"><titleInfo><title>Protection of mammalian telomeres</title></titleInfo><titleInfo contentType="CDATA"><title>Protection of mammalian telomeres</title></titleInfo><name type="personal"><namePart type="family">DE LANGE</namePart><namePart type="given">T.</namePart></name><relatedItem type="host"><titleInfo><title>Oncogene</title></titleInfo><genre>journal</genre><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>21</number></detail><extent unit="pages"><start>532</start><end>540</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00024" displayLabel="bibbi0266986b00024"><titleInfo><title>Telomere maintenance without telomerase</title></titleInfo><titleInfo contentType="CDATA"><title>Telomere maintenance without telomerase</title></titleInfo><name type="personal"><namePart type="family">LUNDBLAD</namePart><namePart type="given">V.</namePart></name><relatedItem type="host"><titleInfo><title>Oncogene</title></titleInfo><genre>journal</genre><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>21</number></detail><extent unit="pages"><start>522</start><end>531</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00025" displayLabel="bibbi0266986b00025"><titleInfo><title>Ku complex interacts with and stimulates the Werner protein</title></titleInfo><titleInfo contentType="CDATA"><title>Ku complex interacts with and stimulates the Werner protein</title></titleInfo><name type="personal"><namePart type="family">COOPER</namePart><namePart type="given">M. C.</namePart></name><name type="personal"><namePart type="family">MACHWE</namePart><namePart type="given">A.</namePart></name><name type="personal"><namePart type="family">ORREN</namePart><namePart type="given">D. K.</namePart></name><name type="personal"><namePart type="family">BROSH</namePart><namePart type="given">R. M.</namePart></name><name type="personal"><namePart type="family">RAMSDEN</namePart><namePart type="given">D.</namePart></name><name type="personal"><namePart type="family">BOHR</namePart><namePart type="given">V. A.</namePart></name><relatedItem type="host"><titleInfo><title>Genes Dev.</title></titleInfo><genre>journal</genre><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>14</number></detail><extent unit="pages"><start>907</start><end>912</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00026" displayLabel="bibbi0266986b00026"><titleInfo><title>Ku is associated with the telomere in mammals</title></titleInfo><titleInfo contentType="CDATA"><title>Ku is associated with the telomere in mammals</title></titleInfo><name type="personal"><namePart type="family">HSU</namePart><namePart type="given">H. L.</namePart></name><name type="personal"><namePart type="family">GILLEY</namePart><namePart type="given">D.</namePart></name><name type="personal"><namePart type="family">BLACKBURN</namePart><namePart type="given">E. H.</namePart></name><name type="personal"><namePart type="family">CHEN</namePart><namePart type="given">D. J.</namePart></name><relatedItem type="host"><titleInfo><title>Proc. Natl. Acad. Sci. U.S.A.</title></titleInfo><genre>journal</genre><part><date>1999</date><detail type="volume"><caption>vol.</caption><number>96</number></detail><extent unit="pages"><start>12454</start><end>12458</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00027" displayLabel="bibbi0266986b00027"><name type="personal"><namePart type="family">JOHNSON</namePart><namePart type="given">F. B.</namePart></name><name type="personal"><namePart type="family">MARCINIAK</namePart><namePart type="given">R. A.</namePart></name><name type="personal"><namePart type="family">MCVEY</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">STEWART</namePart><namePart type="given">S. A.</namePart></name><name type="personal"><namePart type="family">HAHN</namePart><namePart type="given">W. C.</namePart></name><name type="personal"><namePart type="family">AND GUARENTE</namePart><namePart type="given">L.</namePart></name><titleInfo><title>Saccharomyces cerevisiae</title></titleInfo><note type="content-in-line">JohnsonF. B., MarciniakR. A., McVeyM., StewartS. A., HahnW. C. and GuarenteL. (2001) The Saccharomyces cerevisiae WRN homologue Sgs1p participates in telomere maintenance in cells lacking telomerase, EMBO J. 20, 905−913.10.1093/emboj/20.4.905</note><identifier type="doi">10.1093/emboj/20.4.905</identifier></relatedItem><relatedItem type="references" ID="bi0266986b00028" displayLabel="bibbi0266986b00028"><titleInfo><title>Telomere repeat DNA forms a large noncovalent complex with unique cohesive properties which is dissociated by Werner syndrome DNA helicase in the presence of replication protein A</title></titleInfo><titleInfo contentType="CDATA"><title>Telomere repeat DNA forms a large noncovalent complex with unique cohesive properties which is dissociated by Werner syndrome DNA helicase in the presence of replication protein A</title></titleInfo><name type="personal"><namePart type="family">OHSUGI</namePart><namePart type="given">I.</namePart></name><name type="personal"><namePart type="family">TOKUTAKE</namePart><namePart type="given">Y.</namePart></name><name type="personal"><namePart type="family">SUZUKI</namePart><namePart type="given">N.</namePart></name><name type="personal"><namePart type="family">IDE</namePart><namePart type="given">T.</namePart></name><name type="personal"><namePart type="family">SUGIMOTO</namePart><namePart type="given">M.</namePart></name><name type="personal"><namePart type="family">FURUICHI</namePart><namePart type="given">Y.</namePart></name><relatedItem type="host"><titleInfo><title>Nucleic Acids Res.</title></titleInfo><genre>journal</genre><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>28</number></detail><extent unit="pages"><start>3642</start><end>3648</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986b00029" displayLabel="bibbi0266986b00029"><titleInfo><title>The Bloom's and Werner's syndrome proteins are DNA structure-specific helicases</title></titleInfo><titleInfo contentType="CDATA"><title>The Bloom's and Werner's syndrome proteins are DNA structure-specific helicases</title></titleInfo><name type="personal"><namePart type="family">MOHAGHEGH</namePart><namePart type="given">P.</namePart></name><name type="personal"><namePart type="family">KAROW</namePart><namePart type="given">J. K.</namePart></name><name type="personal"><namePart type="family">BROSH</namePart><namePart type="given">R. M.</namePart></name><name type="personal"><namePart type="family">BOHR</namePart><namePart type="given">V. A.</namePart></name><name type="personal"><namePart type="family">HICKSON</namePart><namePart type="given">I. D.</namePart></name><relatedItem type="host"><titleInfo><title>Nucleic Acids Res.</title></titleInfo><genre>journal</genre><part><date>2001</date><detail type="volume"><caption>vol.</caption><number>29</number></detail><extent unit="pages"><start>2843</start><end>2849</end></extent></part></relatedItem></relatedItem><relatedItem type="references" ID="bi0266986n00001" displayLabel="bibbi0266986n00001"><titleInfo><title>Abbreviations: WS, Werner syndrome; nt, nucleotides; PAGE, polyacrylamide gel electrophoresis; BPB, bromphenol blue; XC, xylene cyanol; EMSA, electrophoretic mobility shift assay; ATPγS, adenosine 5‘-O-(3-thiotriphosphate); DNase I, bovine pancreatic deoxyribonuclease I; bp, base pairs.</title></titleInfo><note type="content-in-line">Abbreviations: WS, Werner syndrome; nt, nucleotides; PAGE, polyacrylamide gel electrophoresis; BPB, bromphenol blue; XC, xylene cyanol; EMSA, electrophoretic mobility shift assay; ATPγS, adenosine 5‘-O-(3-thiotriphosphate); DNase I, bovine pancreatic deoxyribonuclease I; bp, base pairs.</note></relatedItem><relatedItem type="references" ID="bi0266986n00002" displayLabel="bibbi0266986n00002"><titleInfo><title>A. Machwe and D. K. Orren, unpublished experiments.</title></titleInfo><note type="content-in-line">A. Machwe and D. K. Orren, unpublished experiments.</note></relatedItem><identifier type="istex">D06E0453D1A3D13C6BD2799B983FF0D18FE29E94</identifier><identifier type="ark">ark:/67375/TPS-SBXVLNJ0-C</identifier><identifier type="DOI">10.1021/bi0266986</identifier><accessCondition type="use and reproduction" contentType="restricted">Copyright © 2002 American Chemical Society</accessCondition><recordInfo><recordContentSource authority="ISTEX" authorityURI="https://loaded-corpus.data.istex.fr" valueURI="https://loaded-corpus.data.istex.fr/ark:/67375/XBH-X5HBJWF8-J">acs</recordContentSource><recordOrigin>Converted from (version 1.2.10) to MODS version 3.6.</recordOrigin><recordCreationDate encoding="w3cdtf">2020-04-10</recordCreationDate></recordInfo></mods><json:item><extension>json</extension><original>false</original><mimetype>application/json</mimetype><uri>https://api.istex.fr/ark:/67375/TPS-SBXVLNJ0-C/record.json</uri></json:item></metadata><annexes><json:item><extension>tiff</extension><original>true</original><mimetype>image/tiff</mimetype><uri>https://api.istex.fr/document/D06E0453D1A3D13C6BD2799B983FF0D18FE29E94/annexes/tiff</uri></json:item></annexes><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
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