Department of Biochemistry, Duke University School of Medicine, Durham, NC, USA.
Base4, Durham, NC, USA.
Nat Chem Biol. 2023 Jul;19(7):900-910. doi: 10.1038/s41589-023-01306-5. Epub 2023 Apr 24.
Replicative errors contribute to the genetic diversity needed for evolution but in high frequency can lead to genomic instability. Here, we show that DNA dynamics determine the frequency of misincorporating the A•G mismatch, and altered dynamics explain the high frequency of 8-oxoguanine (8OG) A•8OG misincorporation. NMR measurements revealed that A•G (population (pop.) of >91%) transiently forms sparsely populated and short-lived A•G (pop. of ~2% and k = k + k of ~137 s) and A•G (pop. of ~6% and k of ~2,200 s) Hoogsteen conformations. 8OG redistributed the ensemble, rendering A•8OG the dominant state. A kinetic model in which A•G is misincorporated quantitatively predicted the dA•dGTP misincorporation kinetics by human polymerase β, the pH dependence of misincorporation and the impact of the 8OG lesion. Thus, 8OG increases replicative errors relative to G because oxidation of guanine redistributes the ensemble in favor of the mutagenic A•8OG Hoogsteen state, which exists transiently and in low abundance in the A•G mismatch.
复制错误有助于进化所需的遗传多样性，但在高频下可能导致基因组不稳定。在这里，我们表明 DNA 动力学决定了误掺入 A•G 错配的频率，并且动力学的改变解释了 8-氧鸟嘌呤（8OG）A•8OG 误掺入的高频。NMR 测量显示，A•G（群体（pop.）大于 91%）瞬时形成稀疏且短暂的 A•G（pop. 约 2%，k=k+k 约 137s）和 A•G（pop. 约 6%，k 约 2200s）Hoogsteen 构象。8OG 重新分配了整体，使 A•8OG 成为主要状态。一个动力学模型表明，A•G 被定量误掺入，这定量预测了人类聚合酶β的 dA•dGTP 误掺入动力学、误掺入的 pH 依赖性以及 8OG 损伤的影响。因此，8OG 相对于 G 增加了复制错误，因为鸟嘌呤的氧化使整体向有利于具有诱变作用的 A•8OG Hoogsteen 状态重新分布，而 A•G 错配中的这种状态是短暂的且丰度低。
