Functional overlap between Sgs1-Top3 and the Mms4-Mus81 endonuclease
Functional overlap between Sgs1-Top3 and the Mms4-Mus81 endonuclease
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DOI：
10.1101/gad.932201
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发表时间：
2001-10-15
影响因子：
10.5
通讯作者：
Brill, SJ
中科院分区：
文献类型：
--
作者：
Kaliraman, V;Mullen, JR;Brill, SJ
RecQ DNA解旋酶、人BLM和酵母Sgs 1与拓扑异构酶III（Top3）形成复合物。并且被认为在DNA复制过程中起作用，以重新启动由于DNA损伤或拓扑压力而暂停的叉。我们之前已经表明，缺乏SGS 1或TOP 3的酵母细胞需要MMS 4和MUS 81才能生存。在这里，我们表明，Mms 4和Mus 81形成异二聚体结构特异性内切核酸酶，切割分支的DNA。这两个亚基都是最佳表达、底物结合和核酸酶活性所必需的。Mms 4和Mus 81是与核苷酸切除修复（NER）所需的Rad 1-Rad 10（XPF/ERCC 1）内切核酸酶相关的保守蛋白。然而，Mms 4-Mus 81内切核酸酶对分支双链体DNA和复制叉底物的活性是简单Y型的25倍，简单Y型是NER复合物的优选底物。我们还提出了遗传数据，表明一个新的作用MMS 4-Mus 81减数分裂重组。我们的研究结果表明，停滞的复制叉MMS 4-Mus 81裂解的基板，特别是在没有SGS 1或BLM。通过同源重组修复这种双链断裂（DSB）可能是BLM-/-细胞中姐妹染色单体交换（SCE）水平升高的原因。
The RecQ DNA helicases, human BLM and yeast Sgs1, form a complex with topoisomerase III (Top3). and are thought to act during DNA replication to restart forks that have paused due to DNA damage or topological stress. We have shown previously that yeast cells lacking SGS1 or TOP3 require MMS4 and MUS81 for viability. Here we show that Mms4 and Mus81 form a heterodimeric structure-specific endonuclease that cleaves branched DNA. Both subunits are required for optimal expression, substrate binding, and nuclease activity. Mms4 and Mus81 are conserved proteins related to the Rad1-Rad10 (XPF/ERCC1) endonuclease required for nucleotide excision repair (NER). However, the Mms4-Mus81 endonuclease is 25 times more active on branched duplex DNA and replication fork substrates than simple Y-forms, the preferred substrate for the NER complexes. We also present genetic data that indicate a novel role for Mms4-Mus81 in meiotic recombination. Our results suggest that stalled replication forks are substrates for Mms4-Mus81 cleavage-particularly in the absence of Sgs1 or BLM. Repair of this double-strand break (DSB) by homologous recombination may be responsible for the elevated levels of sister chromatid exchange (SCE) found in BLM-/- cells.