Recurrent mismatch binding by MutS mobile clamps on DNA localizes repair complexes nearby
Recurrent mismatch binding by MutS mobile clamps on DNA localizes repair complexes nearby
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DOI：
10.1073/pnas.1918517117
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发表时间：
2020-07-28
影响因子：
11.1
通讯作者：
Weninger, Keith R.
中科院分区：
文献类型：
--
作者：
Hao, Pengyu;LeBlanc, Sharonda J.;Weninger, Keith R.
DNA错配修复（MMR）是基因组的守护者，当MutS识别错配并招募MutL在含错误的链上产生切口时，MMR起作用，允许切除和DNA再合成。主要的MMR模型证实，在错配识别后，ATP将MutS转化为不再识别错配的水解独立的扩散性移动的钳。关于识别后MutS移动的钳及其与MutL的相互作用知之甚少。已经提出了两种不同的框架：一种是MutS-MutL复合物在DNA上保持移动的，另一种是MutL阻止MutS移动。在这里，我们使用单分子FRET跟踪MutS的识别后状态和MutL对其性质的影响。与目前的想法相反，我们发现在最初的移动的钳形成事件之后，MutS经历了频繁的错配再结合和移动的钳重组的循环而不释放DNA。值得注意的是，需要ATP水解来改变MutS的构象，使得它可以再次识别错配而不是绕过它;因此，ATP水解允许MutS移动的夹重新结合错配。此外，与MutL的相互作用既可以在形成移动的钳的途中在错配处捕获MutS，又可以停止DNA上的移动的钳的移动。MutS的频繁重新结合的错配，这增加了其在错配附近的停留时间，加上MutL的捕获MutS的能力，应该增加的概率，MutS-MutL MMR起始复合物定位附近的错配。
DNA mismatch repair (MMR), the guardian of the genome, com-mences when MutS identifies a mismatch and recruits MutL to nick the error-containing strand, allowing excision and DNA resynthe-sis. Dominant MMR models posit that after mismatch recognition, ATP converts MutS to a hydrolysis-independent, diffusive mobile clamp that no longer recognizes the mismatch. Little is known about the postrecognition MutS mobile clamp and its interactions with MutL. Two disparate frameworks have been proposed: One in which MutS-MutL complexes remain mobile on the DNA, and one in which MutL stops MutS movement. Here we use single-molecule FRET to follow the postrecognition states of MutS and the impact of MutL on its properties. In contrast to current think-ing, we find that after the initial mobile clamp formation event, MutS undergoes frequent cycles of mismatch rebinding and mobile clamp reformation without releasing DNA. Notably, ATP hy-drolysis is required to alter the conformation of MutS such that it can recognize the mismatch again instead of bypassing it; thus, ATP hydrolysis licenses the MutS mobile clamp to rebind the mismatch. Moreover, interaction with MutL can both trap MutS at the mismatch en route to mobile clamp formation and stop movement of the mobile clamp on DNA. MutS's frequent rebinding of the mismatch, which increases its residence time in the vicinity of the mismatch, coupled with MutL's ability to trap MutS, should increase the prob-ability that MutS-MutL MMR initiation complexes localize near the mismatch.