Nucleotides with Altered Hydrogen Bonding Capacities Impede Human DNA Polymerase η by Reducing Synthesis in the Presence of the Major Cisplatin DNA Adduct

Human DNA polymerase eta (hPol eta) contributes to anticancer drug resistance by catalyzing the replicative bypass of DNA adducts formed by the widely used chemotherapeutic agent cis-diamminedichloroplatinum (cisplatin). A chemical basis for overcoming bypass-associated resistance requires greater knowledge of how small molecules influence the hPol eta-catalyzed bypass of DNA adducts. In this study, we demonstrated how synthetic nucleoside triphosphates act as hPol eta substrates and characterized their influence on hPol eta-mediated DNA synthesis over unmodified and platinated DNA. The single nucleotide incorporation efficiency of the altered nucleotides varied by more than 10-fold and the higher incorporation rates appeared to be attributable to the presence of an additional hydrogen bond between incoming dNTP and templating base. Finally, full-length DNA synthesis in the presence of increasing concentrations of synthetic nucleotides reduced the amount of DNA product independent of the template, representing the first example of hPol eta inhibition in the presence of a platinated DNA template.