Translesion synthesis across abasic lesions by human B-family and Y-family DNA polymerases alpha, delta, eta, iota, kappa, and REV1.

摘要

Abasic (apurinic/apyrimidinic, AP) sites are the most common DNA lesions formed in cells, induce severe blocks to DNA replication, and are highly mutagenic. Human Y-family translesion DNA polymerases (pols) such as pols eta, iota, kappa, and REV1 have been suggested to play roles in replicative bypass across many DNA lesions where B-family replicative pols stall, but their individual catalytic functions in AP site bypass are not well understood. In this study, oligonucleotides containing a synthetic abasic lesion (tetrahydrofuran analogue) were compared for catalytic efficiency and base selectivity with human Y-family pols eta, iota, kappa, and REV1 and B-family pols alpha and delta. Pol eta and pol delta/proliferating cell nuclear antigen (PCNA) copied past AP sites quite effectively and generated products ranging from one-base to full-length extension. Pol iota and REV1 readily incorporated one base opposite AP sites but then stopped. Pols kappa and alpha were severely blocked at AP sites. Pol eta preferentially inserted T and A; pol iota inserted T, G, and A; pol kappa inserted C and A; REV1 preferentially inserted C opposite AP sites. The B-family pols alpha and delta/PCNA preferentially inserted A (85% and 58%, respectively) consonant with the A-rule hypothesis. Pols eta and delta/PCNA were much more efficient in next-base extension, preferably from A positioned opposite an AP site, than pol kappa. These results suggest that AP sites might be bypassed with moderate efficiency by single B- and Y-family pols or combinations, possibly by REV1 and pols iota, eta, and delta/PCNA at the insertion step opposite the lesion and by pols eta and delta/PCNA at the subsequent extension step. The patterns of the base preferences of human B-family and Y-family pols in both insertion and extension are pertinent to some of the mutagenesis events induced by AP lesions in human cells.