The MutSα-proliferating cell nuclear antigen interaction in human DNA mismatch repair
The MutSα-proliferating cell nuclear antigen interaction in human DNA mismatch repair
复制标题
DOI：
10.1074/jbc.m800606200
复制
发表时间：
2008-05-09
影响因子：
4.8
通讯作者：
Modrich, Paul
中科院分区：
文献类型：
--
作者：
Iyer, Ravi R.;Pohlhaus, Timothy J.;Modrich, Paul
我们研究了人 MutS α 中心点增殖细胞核抗原 (PCNA) 复合物在错配修复中的相互作用参数、构象和功能意义。在异源双链 DNA 不存在或存在的情况下，这两种蛋白质以 1:1 化学计量关联，K-D 为 0.7 μM。 PCNA 不会影响 MutS α 对错配的亲和力，错配结合的 MutS α 会结合 PCNA。小角度 X 射线散射研究已经确定了复合物的分子参数，这些参数与伸长构象一致，其中两种蛋白质以端对端方式以不涉及延伸的非结构化系链的方式关联，如针对酵母 MutS α 和 PCNA 所提出的那样（Shell, S. S.、Putnam, C. D. 和 Kolodner, R. D. (2007) Mol. Cell 26, 565 578）。缺乏 PCNA 相互作用基序的 MutS α 变体在 3'-或 5'-定向错配引发的切除中具有功能，但在 5'-定向错配修复中显示出部分缺陷。这一发现与 MutS α PCNA 相互作用基序失活所赋予的适度突变性一致，并表明复制夹与其他修复蛋白的相互作用解释了 PCNA 在 MutS α 依赖性错配修复中的重要作用。
We have examined the interaction parameters, conformation, and functional significance of the human MutS alpha center dot proliferating cell nuclear antigen ( PCNA) complex in mismatch repair. The two proteins associate with a 1: 1 stoichiometry and a K-D of 0.7 mu M in the absence or presence of heteroduplex DNA. PCNA does not influence the affinity of MutS alpha for a mismatch, and mismatch-bound MutS alpha binds PCNA. Small angle x-ray scattering studies have established the molecular parameters of the complex, which are consistent with an elongated conformation in which the two proteins associate in an end-to-end fashion in a manner that does not involve an extended unstructured tether, as has been proposed for yeast MutS alpha and PCNA ( Shell, S. S., Putnam, C. D., and Kolodner, R. D. (2007) Mol. Cell 26, 565 578). MutS alpha variants lacking the PCNA interaction motif are functional in 3 '- or 5 '- directed mismatch- provoked excision, but display a partial defect in 5 '- directed mismatch repair. This finding is consistent with the modest mutability conferred by inactivation of the MutS alpha PCNA interaction motif and suggests that interaction of the replication clamp with other repair protein(s) accounts for the essential role of PCNA in MutS alpha-dependent mismatch repair.