The Yeast Initiator tRNAMet can Act as an Elongator tRNAMet In Vivo
Identifieur interne : 004607 ( Main/Exploration ); précédent : 004606; suivant : 004608The Yeast Initiator tRNAMet can Act as an Elongator tRNAMet In Vivo
Auteurs : Stefan U. Ström [Suède] ; Ulrich Von Pawel-Rammingen [Suède] ; Anders S. Byström [Suède]Source :
- Journal of Molecular Biology [ 0022-2836 ] ; 1993.
English descriptors
Abstract
Abstract: Saccharomyces cerevisiae uses two different methionine accepting tRNAs during protein synthesis. One, tRNAMeti, is used exclusively during the initiation of translation whereas the other, tRNAMetm, is used during the elongation of translation. To study the unique features of each methionine tRNA species, we constructed yeast strains with null alleles of the five elongator methionine tRNA (EMT) genes and strains with null alleles of the four initiator methionine tRNA (IMT) genes, respectively. Consequently, growth of these strains was dependent either on a tRNAMetm or a tRNAMeti, respectively, encoded from a plasmid-derived gene. For both null mutants, the plasmid carrying the wild-type gene can be selected against and exchanged for another plasmid derived EMT or IMT gene (wild-type or mutant). A high gene dosage of the wild-type IMT gene could restore growth to the elongator-depleted strain. However, wild-type EMT genes in a high gene dosage never restored growth of the initiator depleted strain. Thus, the elongator tRNAMet is much more restricted to participate in the initiation of translation than the initiator tRNAMet is restricted to participate in the elongation process. Using the two null mutants, we have identified tRNAMetm mutants, which show reduced elongator activity, and tRNAMeti mutants, with improved elongator activity in the elongator depleted strain. Also, tRNAMetm mutants that function as an initiator tRNA in the initiator depleted strain were identified. From this mutant analysis, we showed that the conserved U/rT at position 54 of the elongator tRNAMet is an important determinant for an elongator tRNA. The most important determinant for an initiator was shown to be the acceptor stem and especially the conserved A1 · U72 base-pair. Mutant tRNAs, with reduced activity in either process, were investigated for enhanced activity during overproduction of the α and β-subunits of the eukaryotic initiation factor 2 (eIF-2) or the eukaryotic elongation factor 1α (eEF-1α). The data suggest that the U/rT of the elongator at position 54 is important for eEF-1α recognition and that the acceptor stem of the initiator is important for eIF-2 recognition.
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DOI: 10.1006/jmbi.1993.1483
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Byström</name><affiliation wicri:level="1"><country xml:lang="fr">Suède</country><wicri:regionArea>Department of Microbiology University of Umeå S-901 87 Umeå</wicri:regionArea></affiliation></author></analytic><monogr></monogr><series><title level="j">Journal of Molecular Biology</title><title level="j" type="abbrev">YJMBI</title><idno type="ISSN">0022-2836</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="1993">1993</date><biblScope unit="volume">233</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="43">43</biblScope><biblScope unit="page" to="58">58</biblScope></imprint><idno type="ISSN">0022-2836</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0022-2836</idno></seriesStmt></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>yeast elongator tRNAMet genes; tRNAMeti; tRNAMetm; elongator/initiator tRNA discrimination; tRNA mutants</term></keywords></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Abstract: Saccharomyces cerevisiae uses two different methionine accepting tRNAs during protein synthesis. One, tRNAMeti, is used exclusively during the initiation of translation whereas the other, tRNAMetm, is used during the elongation of translation. To study the unique features of each methionine tRNA species, we constructed yeast strains with null alleles of the five elongator methionine tRNA (EMT) genes and strains with null alleles of the four initiator methionine tRNA (IMT) genes, respectively. Consequently, growth of these strains was dependent either on a tRNAMetm or a tRNAMeti, respectively, encoded from a plasmid-derived gene. For both null mutants, the plasmid carrying the wild-type gene can be selected against and exchanged for another plasmid derived EMT or IMT gene (wild-type or mutant). A high gene dosage of the wild-type IMT gene could restore growth to the elongator-depleted strain. However, wild-type EMT genes in a high gene dosage never restored growth of the initiator depleted strain. Thus, the elongator tRNAMet is much more restricted to participate in the initiation of translation than the initiator tRNAMet is restricted to participate in the elongation process. Using the two null mutants, we have identified tRNAMetm mutants, which show reduced elongator activity, and tRNAMeti mutants, with improved elongator activity in the elongator depleted strain. Also, tRNAMetm mutants that function as an initiator tRNA in the initiator depleted strain were identified. From this mutant analysis, we showed that the conserved U/rT at position 54 of the elongator tRNAMet is an important determinant for an elongator tRNA. The most important determinant for an initiator was shown to be the acceptor stem and especially the conserved A1 · U72 base-pair. Mutant tRNAs, with reduced activity in either process, were investigated for enhanced activity during overproduction of the α and β-subunits of the eukaryotic initiation factor 2 (eIF-2) or the eukaryotic elongation factor 1α (eEF-1α). The data suggest that the U/rT of the elongator at position 54 is important for eEF-1α recognition and that the acceptor stem of the initiator is important for eIF-2 recognition.</div></front></TEI><affiliations><list><country><li>Suède</li></country></list><tree><country name="Suède"><noRegion><name sortKey=" Strom, Stefan U" sort=" Strom, Stefan U" uniqKey=" Strom S" first="Stefan U." last=" Ström">Stefan U. Ström</name></noRegion><name sortKey="Bystrom, Anders S" sort="Bystrom, Anders S" uniqKey="Bystrom A" first="Anders S." last="Byström">Anders S. Byström</name><name sortKey="Von Pawel Rammingen, Ulrich" sort="Von Pawel Rammingen, Ulrich" uniqKey="Von Pawel Rammingen U" first="Ulrich" last="Von Pawel-Rammingen">Ulrich Von Pawel-Rammingen</name></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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