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

• Published in: Journal of the American Chemical Society 2019-03, Vol.141 (11), p.4584-4596
• Main Authors: Koag, Myong-Chul, Jung, Hunmin, Lee, Seongmin
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b08551

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 β and η replicating across oxoA and structural studies of polβ incorporating dTTP/dGTP opposite oxoA. While polη 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. Polη and polβ 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 polβ 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.