In Vitro Bypass of Thymidine Glycol by DNA Polymerase ? Forms Sequence-Dependent Frameshift Mutations.

ABSTRACT: Unrepaired DNA lesions block replication and threaten genomic stability. Several specialized translesion polymerases, including polymerase ? (Pol ?), contribute to replicative bypass of these lesions. The role of Pol ? in double-strand break repair is well-understood, but its contribution to translesion synthesis is much less so. We describe the action of Pol ? on templates containing thymidine glycol (Tg), a major cytotoxic, oxidative DNA lesion that blocks DNA replication. Unrepaired Tg lesions are bypassed in human cells by specialized translesion polymerases by one of two distinct pathways: high-fidelity bypass by the combined action of Pol ? and Pol ? or weakly mutagenic bypass by Pol ?. Here we report that in vitro bypass of Tg by Pol ? results in frameshift mutations (deletions) in a sequence-dependent fashion. Steady-state kinetic analysis indicated that one- and two-nucleotide deletions are formed 9- and 6-fold more efficiently, respectively, than correct, full-length bypass products. Sequencing of in vitro bypass products revealed that bypass preference decreased in the following order on a template where all three outcomes were possible: two-nucleotide deletion > correct bypass > one-nucleotide deletion. These results suggest that bypass of Tg by Pol ? results in mutations opposite the lesion, as well as frameshift mutations.

SUBMITTER: Laverty DJ 

PROVIDER: S-EPMC5743609 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature