摘要:
The influence of base pair size and shape on the fidelity of DNA polymerase-mediated extension past lesion-containing mispairs was examined. Primer extension analysis was performed with synthetic nucleo-sides paired opposite the pro-mutagenic DNA lesion O-6-benzylguanine (O-6-BnG). These data,indicate that the error prone DNA polymerase IV (Dpo4) inefficiently extended past the larger Peri:O-6-BnG base pair, and in contrast, error free extension was observed for the smaller BIM:O-6-BnG base pair. Steady-state kinetic analysis, revealed that Dpo4 catalytic efficiency was strongly influenced by the primer:template base pair. Compared to the C:G pair, a 1.9- and 79 000-fold reduction in Dpo4 efficiency was observed for terminal C:O-6-BnG and BIM:G base pairs respectively. These results demonstrate the impact of geometrical size and shape on polymerase-mediated mispair extension.