The efficiency and fidelity of translesion synthesis past cisplatin and oxaliplatin GpG adducts by human DNA polymerase beta

DNA polymerase beta (pol beta) is the only mammalian DNA polymerase identif ied to date that can catalyze extensive bypass of platinum-DNA adducts in v itro. Previous studies suggest that DNA synthesis by pol beta is distributi ve on primed single-stranded DNA and processive on gapped DNA, The data pre sented in this paper provide an analysis of translesion synthesis past cisp latin- and oxaliplatin-DNA adducts by pol beta functioning in both distribu tive and processive modes using primer extension and steady-state kinetic e xperiments. Translesion synthesis past Pt-DNA adducts was greater with gapp ed DNA templates than with single-stranded DNA templates. In the processive mode pol beta did not discriminate between cisplatin and oxaliplatin adduc ts, while in the distributive mode it displayed about 2-fold increased abil ity for translesion synthesis past oxaliplatin compared with cisplatin addu cts. The differentiation between cisplatin and oxaliplatin adducts resulted from a K-m-mediated increase in the efficiency of dCTP incorporation acros s from the 3'-G of oxaliplatin-GG adducts. Rates of misincorporation across platinated guanines determined by the steady-state kinetic assay were high er in reactions with primed single-stranded templates than with gapped DNA and a slight increase in the misincorporation of dTTP across from the 3'-G was found for oxaliplatin compared with cisplatin adducts.