Human DNA‐topoisomerase I activity is affected by bis‐netropsin's binding to DNA minor groove

SUMMARY Bis-netropsins (bis-Nts) are known to be efficient inhibitors of human DNA topoisomerase (topo) I with a higher antitumor activity than netropsin. New sequence-specific derivatives of bis-Nts were used for modulation of topo I-mediated DNA cleavage with and without camptothecin (CPT). Relation between the bis-Nts binding sites and topo I cleavage sites has been analyzed with the plasmid DNA constructs generated by insertion of synthetic oligonucleotides containing various topo I-cleavage and bis-Nt-binding sites. These constructs offer an opportunity to study minor groove binders effects on the topo I reaction on DNA. Three major effects: (i) bis-Nt - mediated disappearance of some of the topo I cleavage sites; (ii) enhancement of some other sites, and, (iii) generation of new cleavage sites, have been found and analyzed. These effects demonstrate that bis-Nts drastically change the topo Imediated DNA cleavage.