Small Rad51 and Dmc1 Complexes Often Co-occupy Both Ends of a Meiotic DNA Double Strand Break.
Small Rad51 and Dmc1 Complexes Often Co-occupy Both Ends of a Meiotic DNA Double Strand Break.
复制标题
DOI：
10.1371/journal.pgen.1005653
复制
发表时间：
2015-12
期刊：
影响因子：
4.5
通讯作者：
Bishop DK
中科院分区：
文献类型：
--
作者：
Brown MS;Grubb J;Zhang A;Rust MJ;Bishop DK
真核细胞RecA样蛋白Rad 51和Dmc 1在减数分裂过程中通过修复程序性DNA双链断裂（DSB）促进同源染色体之间的重组。以前的研究表明，Rad 51和Dmc 1形成部分重叠的共焦点。在这里，我们展示了这些Rad 51-Dmc 1共焦点通常成对排列，间隔距离高达400 nm。当DSB显著减少或当链交换或突触被阻断时，成对的共灶仍然普遍存在。超分辨率dSTORM显微镜显示，通过常规光学显微镜观察到的单个焦点通常由两个或更多个子结构组成。这些数据支持一个模型，其中由单个DSB形成的两个ssDNA束彼此分开的距离高达400 nm，两个束通常由一个或多个短（约100 nt）Rad 51细丝和一个或多个短Dmc 1细丝结合。在减数分裂过程中，一种特殊形式的染色体分离确保配子只包含一个亲本染色体的拷贝。要准确分离母本和父本染色体，首先需要它们成对连接。同源重组形成了这些必要的连接。同源染色体之间的连接是通过形成然后修复DNA双链断裂来实现的。Rad 51和Dmc 1是结构上相关的酶，它们通过在断裂位点结合DNA形成复合物，然后通过搜索和侵入同源染色体上相应的未断裂DNA序列来促进断裂修复。在本文中，我们描述了重组复合物结构的几个特点。我们提供的证据表明：1。Rad 51和Dmc 1都加载到单个DSB的两端，说明DSB两端的已知活性; 2. DSB的两端可以分开高达0.4微米的距离; 3. Rad 51和Dmc 1复合物仅占据DNA的小片段（约100个碱基）; 4.多个短的Rad 51和Dmc 1复合物可以占据单个DSB末端。
The Eukaryotic RecA-like proteins Rad51 and Dmc1 cooperate during meiosis to promote recombination between homologous chromosomes by repairing programmed DNA double strand breaks (DSBs). Previous studies showed that Rad51 and Dmc1 form partially overlapping co-foci. Here we show these Rad51-Dmc1 co-foci are often arranged in pairs separated by distances of up to 400 nm. Paired co-foci remain prevalent when DSBs are dramatically reduced or when strand exchange or synapsis is blocked. Super-resolution dSTORM microscopy reveals that individual foci observed by conventional light microscopy are often composed of two or more substructures. The data support a model in which the two tracts of ssDNA formed by a single DSB separate from one another by distances of up to 400 nm, with both tracts often bound by one or more short (about 100 nt) Rad51 filaments and also by one or more short Dmc1 filaments. During meiosis, a specialized form of chromosome segregation ensures that gametes contain only one copy of the parental chromosome complement. Accurate segregation of maternal and paternal chromosomes requires them to first become connected in pairs. Homologous recombination forms these needed connections. Connections between homolog chromosomes are made by forming and then repairing DNA double strand breaks. Rad51 and Dmc1 are structurally related enzymes that form complexes by binding DNA at sites of breaks, where they then function to promote break repair by searching for and invading corresponding unbroken DNA sequences on a homologous chromosome. In this paper, we describe several features of the recombination complex structure. We provide evidence that: 1. both Rad51 and Dmc1 load onto both ends of a single DSB, accounting for the known activity of both ends of a DSB; 2. the two ends of a DSB can separate by distances of up to 0.4 microns; 3. Rad51 and Dmc1 complexes only occupy small segments of DNA (about 100 bases); 4. multiple short Rad51 and Dmc1 complexes can occupy a single DSB end.