We have developed a technique for cross-linking DNA binding proteins to DNA using psoralen furanside monoadducts as photoaffinity probes and a continuous-wave argon ion laser (366 nm) as a light source. Several DNA binding proteins (T7 RNA polymerase, UvrB, single-stranded DNA binding protein of Escherichia coli, T4 gp32, and RecA of E. coli) are shown to cross-link to single-stranded psoralen monoadducted DNA oligos differing in length and sequence. Increasing fluences of laser light on a fixed ratio of DNA/protein resulted in an increase in the yield of cross-links. Titration experiments were carried out to measure the apparent cross-linking constant (KappXL) for T7 RNA polymerase or UvrB to a monoadducted 24 mer DNA. The estimated values for the apparent cross-linking constant were in the range of (2-3) x 10(-7) M for both T7 RNA polymerase and UvrB. The efficiency of cross-linking was investigated as a function of the length of adducted DNA and also as a fraction of the total noncovalent binding of proteins of psoralenated DNAs. The results showed that in the cases of T7 RNA polymerase and UvrB cross-linking was more efficient with short oligos (8 and 19 mers) as compared to longer oligos (50 mer). A tryptic peptide of T7 RNA polymerase that was conjugated to a psoralen furanside monoadducted 12 mer DNA was isolated by high-performance liquid chromatography. Mass spectrometry and amino acid composition of this peptide revealed that it originated from a region between residues 558 and 608 of the primary structure of T7 RNA polymerase. Two other peptides cross-linked to oligos were also purified. Repeated attempts to perform Edman sequencing of the peptide-DNA conjugates failed. Overall evidence indicates that photo-cross-linking of furanside monoadducts occurred at multiple sites on the proteins. We have shown that T7 RNA polymerase molecules in a ternary complex arrested at the furanside monoadduct can be cross-linked to the DNA templates with laser light. Evidence suggests that the arrested polymerase molecules existed in multiple conformations on the DNA template. This method of transcriptional cross-linking offers a new method for preparing highly stable elongation complexes for further studies.

EXPLOR_STEP=$WICRI_ROOT/Sante/explor/MersV1/Data/Ncbi/Merge

HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 002A02 | SxmlIndent | more

HfdSelect -h $EXPLOR_AREA/Data/Ncbi/Merge/biblio.hfd -nk 002A02 | SxmlIndent | more

{{Explor lien
   |wiki=    Sante
   |area=    MersV1
   |flux=    Ncbi
   |étape=   Merge
   |type=    RBID
   |clé=     pubmed:8504073
   |texte=   Laser-induced protein-DNA cross-links via psoralen furanside monoadducts.
}}

HfdIndexSelect -h $EXPLOR_AREA/Data/Ncbi/Merge/RBID.i   -Sk "pubmed:8504073" \
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