Assembly of RecA-like recombinases: Distinct roles for mediator proteins in mitosis and meiosis
Assembly of RecA-like recombinases: Distinct roles for mediator proteins in mitosis and meiosis
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DOI：
10.1073/pnas.121046198
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发表时间：
2001-07-17
影响因子：
11.1
通讯作者：
Bishop, DK
中科院分区：
文献类型：
--
作者：
Gasior, SL;Olivares, H;Bishop, DK
来自噬菌体T4、大肠杆菌、酵母和高等真核生物的重组酶RecA家族的成员作为组装在单链DNA（ssDNA）束上的高阶寡聚体在重组中起作用。生物化学研究表明，重组酶的组装涉及辅助因子。这些研究已经确定了一类称为重组介体蛋白的蛋白质，其通过促进重组酶在ssDNA结合蛋白（ssb）结合的ssDNA片段上的组装而起作用。在没有介体的情况下，ssb通过与重组酶竞争DNA结合位点来抑制重组反应。在这里，我们简要回顾介导的重组酶组装和目前的新的体内实验结果。在酿酒酵母中的免疫双染色实验表明，Rad 51，真核重组酶，可以组装在或附近的网站含有SSB（复制蛋白A，RPA）在DNA损伤的反应，与需要的调解活动。相应地，介体基因突变体显示缺陷Rad 51组装后DNA darhage和减数分裂过程中，虽然组装的要求是不同的，在这两种情况下。在减数分裂中，Rad 52和Rad 55/57都是必需的，而Rad 52或Rad 55/57足以促进Rad 51在辐射的有丝分裂细胞中的组装。Rad 52在30 ℃而不是20 ℃下促进正常量的Rad 51组装，说明了Rad 55无效突变体的冷敏感性。最后，我们表明Rad 51的组装在S期而不是在G（1）期被辐射诱导，这与Rad 51在修复DNA复制过程中发生的自发损伤中的作用一致。
Members of the RecA family of recombinases from bacteriophage T4, Escherichia coli, yeast, and higher eukaryotes function in recombination as higher-order oligomers assembled on tracts of single-strand DNA (ssDNA). Biochemical studies have shown that assembly of recombinase involves accessory factors. These studies have identified a class of proteins, called recombination mediator proteins, that act by promoting assembly of recombinase on ssDNA tracts that are bound by ssDNA-binding protein (ssb). In the absence of mediators, ssb inhibits recombination reactions by competing with recombinase for DNA-binding sites. Here we briefly review mediated recombinase assembly and present results of new in vivo experiments. Immuno-double-staining experiments in Saccharomyces cerevisiae suggest that Rad51, the eukaryotic recombinase, can assemble at or near sites containing ssb (replication protein A, RPA) during the response to DNA damage, consistent with a need for mediator activity. Correspondingly, mediator gene mutants display defects in Rad51 assembly after DNA darhage and during meiosis, although the requirements for assembly are distinct in the two cases. In meiosis, both Rad52 and Rad55/57 are required, whereas either Rad52 or Rad55/57 is sufficient to promote assembly of Rad51 in irradiated mitotic cells. Rad52 promotes normal amounts of Rad51 assembly in the absence of Rad55 at 30 degreesC but not 20 degreesC, accounting for the cold sensitivity of rad55 null mutants, Finally, we show that assembly of Rad51 is induced by radiation during S phase but not during G(1), consistent with the role of Rad51 in repairing the spontaneous damage that occurs during DNA replication.