HIGH-AFFINITY INTERACTION OF MAMMALIAN DNA TOPOISOMERASE-I WITH SHORTSINGLE-STRANDED AND DOUBLE-STRANDED OLIGONUCLEOTIDES

The interaction of DNA topoisomerase I (topo I) with a set of single- and double-stranded oligonucleotides containing 5-27 mononucleotides w as investigated, All single- and double-stranded oligonucleotides were found to inhibit competitively the supercoiled DNA relaxation reactio n catalyzed by topo I, The enzyme affinity for specific sequence penta nucleotides of the scissile (GACTT, K-i = 2 mu M) and non-cleaved chai n (AAGTC, K-i = 110 mu M) is about 2-4 orders of magnitude higher than that for non-specific oligonucleotides, This specific sequence affini ty increases in several cases: lengthening of single-stranded oligonuc leotides, formation of stable duplexes between complementary oligonucl eotides and preincubation of the enzyme with ligands before addition o f supercoiled DNA, We assume that oligonucleotides having a high affin ity to the enzyme can offer a unique opportunity for rational design o f topoisomerase-targeting drugs.