The rad51-K191R ATPase-defective mutant is impaired for presynaptic filament formation
The rad51-K191R ATPase-defective mutant is impaired for presynaptic filament formation
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DOI：
10.1128/mcb.00599-06
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发表时间：
2006-12-01
影响因子：
5.3
通讯作者：
Symington, Lorraine S.
中科院分区：
文献类型：
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作者：
Fung, Cindy W.;Fortin, Gary S.;Symington, Lorraine S.
Rad 51在单链DNA上聚合形成的核蛋白丝对于同源配对和链交换是必不可少的。Rad 51核蛋白丝的形成和链交换需要ATP结合，但体外这些功能不需要ATP水解。以前的研究表明，酵母菌株表达rad 51-K191 R等位基因是敏感的电离辐射，这表明在体内ATP水解的重要作用。Rad 51-K191 R的募集到双链断裂在体内是有缺陷的，并且这种表型可以通过消除Srs 2解旋酶（Rad 51细丝形成的拮抗剂）来抑制。Rad 51-K191 R菌株的表型也被Rad 54的过表达抑制。在体外，Rad 51-K191 R蛋白表现出与DNA结合的轻微减少，与突触前纤维形成的缺陷一致。然而，rad 51-K191 R突变在杂合二倍体中占主导地位，表明该缺陷不仅仅是由于对DNA的亲和力降低。我们认为Rad 51-K191 R蛋白要么形成改变的细丝，要么在周转中有缺陷，导致可用于DNA结合的游离蛋白质池减少。
The nucleoprotein filament formed by Rad51 polymerization on single-stranded DNA is essential for homologous pairing and strand exchange. ATP binding is required for Rad51 nucleoprotein filament formation and strand exchange, but ATP hydrolysis is not required for these functions in vitro. Previous studies have shown that a yeast strain expressing the rad51-K191R allele is sensitive to ionizing radiation, suggesting an important role for ATP hydrolysis in vivo. The recruitment of Rad51-K191R to double-strand breaks is defective in vivo, and this phenotype can be suppressed by elimination of the Srs2 helicase, an antagonist of Rad51 filament formation. The phenotype of the rad51-K191R strain is also suppressed by overexpression of Rad54. In vitro, the Rad51-K191R protein exhibits a slight decrease in binding to DNA, consistent with the defect in presynaptic filament formation. However, the rad51-K191R mutation is dominant in heterozygous diploids, indicating that the defect is not due simply to reduced affinity for DNA. We suggest the Rad51-K191R protein either forms an altered filament or is defective in turnover, resulting in a reduced pool of free protein available for DNA binding.