Mutagenic Replication of the Major Oxidative Adenine Lesion 7,8-Dihydro-8-oxoadenine by Human DNA Polymerases.

ABSTRACT: Reactive oxygen species attack DNA to produce 7,8-dihyro-8-oxoguanine (oxoG) and 7,8-dihydro-8-oxoadenine (oxoA) as major lesions. The structural basis for the mutagenicity of oxoG, which induces G to T mutations, is well understood. However, the structural basis for the mutagenic potential of oxoA, which induces A to C mutations, remains poorly understood. To gain insight into oxoA-induced mutagenesis, we conducted kinetic studies of human DNA polymerases ? and ? replicating across oxoA and structural studies of pol? incorporating dTTP/dGTP opposite oxoA. While pol? readily bypassed oxoA, it incorporated dGTP opposite oxoA with a catalytic specificity comparable to that of correct insertion, underscoring the promutagenic nature of the major oxidative adenine lesion. Pol? and pol? incorporated dGTP opposite oxoA ?170-fold and ?100-fold more efficiently than that opposite dA, respectively, indicating that the 8-oxo moiety greatly facilitated error-prone replication. Crystal structures of pol? showed that, when paired with an incoming dTTP, the templating oxoA adopted an anti conformation and formed Watson-Crick base pair. When paired with dGTP, oxoA adopted a syn conformation and formed a Hoogsteen base pair with Watson-Crick-like geometry, highlighting the dual-coding potential of oxoA. The templating oxoA was stabilized by Lys280-mediated stacking and hydrogen bonds. Overall, these results provide insight into the mutagenic potential and dual-coding nature of the major oxidative adenine lesion.

SUBMITTER: Koag MC 

PROVIDER: S-EPMC6657779 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature