Sae2 is an endonuclease that processes hairpin DNA cooperatively with the Mre11/Rad50/Xrs2 complex
Sae2 is an endonuclease that processes hairpin DNA cooperatively with the Mre11/Rad50/Xrs2 complex
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DOI：
10.1016/j.molcel.2007.11.001
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发表时间：
2007-11-30
期刊：
影响因子：
16
通讯作者：
Paull, Tanya T.
中科院分区：
文献类型：
--
作者：
Lengsfeld, Bettina M.;Rattray, Alison J.;Paull, Tanya T.
所有生物体中的Mre 11/Rad 50复合物都具有修复DNA双链断裂的功能。在芽殖酵母中，遗传学证据表明Sae 2蛋白对于Mre 11/Rac 50复合物处理发夹DNA中间体和减数分裂双链断裂是必不可少的，但这种功能关系的生化基础尚不清楚。在这里，我们证明，重组Sae 2结合DNA，并表现出单链DNA上的核酸内切酶活性的独立的Mre 11/Rad 50复合物，但发夹DNA结构的切割合作Mre 11/Rad 50或Mre 11/Rad 50/Xrs 2的存在下。发夹结构不是在顶端被Sae 2加工，而是在邻近发夹的单链DNA区域。Sae 2的截短和错义突变体在体外抑制这种核酸内切酶活性，并且在体内不能补充Delta Sae 2菌株的减数分裂和涉及发夹中间体的重组，这表明Sae 2的催化活性对其生物学功能很重要。
Mre11/Rad50 complexes in all organisms function in the repair of DNA double-strand breaks. In budding yeast, genetic evidence suggests that the Sae2 protein is essential for the processing of hairpin DNA intermediates and meiotic double-strand breaks by Mre11/Rac50 complexes, but the biochemical basis of this functional relationship is not known. Here we demonstrate that recombinant Sae2 binds DNA and exhibits endonuclease activity on single-stranded DNA independently of Mre11/Rad50 complexes, but hairpin DNA structures are cleaved cooperatively in the presence of Mre11/Rad50 or Mre11/Rad50/Xrs2. Hairpin structures are not processed at the tip by Sae2 but rather at single-stranded DNA regions adjacent to the hairpin. Truncation and missense mutants of Sae2 inactivate this endonuclease activity in vitro and fail to complement Delta sae2 strains in vivo for meiosis and recombination involving hairpin intermediates, suggesting that the catalytic activities of Sae2 are important for its biological functions.