USE OF PSORALEN-MODIFIED OLIGONUCLEOTIDES TO TRAP 3-STRANDED RECA-DNA COMPLEXES AND REPAIR OF THESE CROSS-LINKED COMPLEXES BY ABC EXCINUCLEASE

  • 15 October 1988
    • journal article
    • research article
    • Vol. 263  (29) , 15110-15117
Abstract
A series of site-specifically cross-linked, three-stranded complexes has been prepared using the RecA protein, form I (covalently closed and negatively supercoilied) pUC19 plasmid, and eight psoralen-monoadducted oligonucleotides betwen 30 and 107 residues in length. Complexes formed much less efficiently if linearized pUC19 was used as the duplex substrate. Quantitative analysis indicates that although RecA is able to utilize a 30-mer in its homologous pairing reaction, incorporation at 50% efficiency requires a single-stranded at least 50 residues long. These three-stranded complexes have been used to study the action mechanism for cross-link repair by ABC excinuclease, and the results are consistent with the recent model of Van Houten, B., Gamper, H., Holbrook, S. R., Hearst, J. E., and Sancar, A. (1986b) Proc. Natl. Acad. Sci. U.S.A. 83, 8077-8081.