Effect of phosphorothioate substitutions on DNA cleavage by Escherichia coli DNA topoisomerase I

Camille J. Roche, Yuk Ching Tse-Dinh

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

To evaluate the structural influence of the DNA phosphate backbone on the activity of Escherichia coli DNA topoisomerase I, modified forms of oligonucleotide dA7 were synthesized with a chiral phosphorothioate replacing the non-bridging oxygens at each position along the backbone. A deoxy-iodo-uracil replaced the 5′-base to crosslink the oligonucleotides by ultraviolet (UV) and assess binding affinity. At the scissile phosphate there was little effect on the cleavage rate. At the +1 phosphate, the rectus phosphorus (Rp)-thio-substitution reduced the rate of cleavage by a factor of 10. At the +3 and -2 positions from the scissile bond, the Rp-isomer was cleaved at a faster rate than the sinister phosphorus (Sp)-isomer. The results demonstrate the importance of backbone contacts between DNA substrate and E. coli topoisomerase I.

Original languageEnglish (US)
Pages (from-to)175-180
Number of pages6
JournalInternational Journal of Biological Macromolecules
Volume29
Issue number3
DOIs
StatePublished - Oct 22 2001

Keywords

  • DNA cleavage
  • Phosphorothioate
  • Topoisomerase I

ASJC Scopus subject areas

  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Economics and Econometrics
  • Energy(all)

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