MSH-MLH complexes formed at a DNA mismatch are disrupted by the PCNA sliding clamp
MSH-MLH complexes formed at a DNA mismatch are disrupted by the PCNA sliding clamp
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DOI：
10.1006/jmbi.2001.4467
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发表时间：
2001-03-09
影响因子：
5.6
通讯作者：
Alani, E
中科院分区：
文献类型：
--
作者：
Bowers, J;Tran, PT;Alani, E
在酿酒酵母中，错配修复(MMR)是由异二聚体MutS同源(MSH)复合体与包括单核苷酸错配和环插入/缺失错配在内的错配结合而启动的。在体外实验中，如果存在ATP，MSH2-MSH6异二聚体的错配结合特异性就被消除了。然而，将MutL同系物复合体MLH1-PMS1加入到含有MSH2-MSH6、ATP和不匹配底物的结合反应中，会形成稳定的三元复合体。该络合物的稳定性表明它代表着MMR中的中间体，随后被其他MMR因子作用。为了支持这一观点，我们发现复制过程因子增殖细胞核抗原在DNA重新合成之前的步骤(S)在MMR中起关键作用，它破坏了预先形成的三元复合体。这些观察结合链霉亲和素末端阻断的错配底物进行的实验表明，增殖细胞核抗原与在DNA错配上形成的MSH-MLH复合体相互作用。(C)2001年学术出版社。
In the yeast Saccharomyces cerevisiae, mismatch repair (MMR) is initiated by the binding of heterodimeric MutS homolog (MSH) complexes to mismatches that include single nucleotide and loop insertion/deletion mispairs. In in vitro experiments, the mismatch binding specificity of the MSH2-MSH6 heterodimer is eliminated if ATP is present. However, addition of the MutL homolog complex MLH1-PMS1 to binding reactions containing MSH2-MSH6, ATP, and mismatched substrate results in the formation of a stable ternary complex. The stability of this complex suggests that it represents an intermediate in MMR that is subsequently acted upon by other MMR factors. In support of this idea, we found that the replication processivity factor proliferating cell nuclear antigen (PCNA), which plays a critical role in MMR at step(s) prior to DNA resynthesis, disrupted preformed ternary complexes. These observations, in conjunction with experiments performed with streptavidin end-blocked mismatch substrates, suggested that PCNA interacts with an MSH-MLH complex formed on DNA mispairs. (C) 2001 Academic Press.