Chromosome Synapsis Alleviates Mek1-Dependent Suppression of Meiotic DNA Repair.
Chromosome Synapsis Alleviates Mek1-Dependent Suppression of Meiotic DNA Repair.
复制标题
染色体突触减轻了MEK1依赖性抑制减数分裂DNA修复。
DOI：
10.1371/journal.pbio.1002369
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发表时间：
2016-02
期刊：
影响因子：
9.8
通讯作者：
Hochwagen A
中科院分区：
文献类型：
--
作者：
Subramanian VV;MacQueen AJ;Vader G;Shinohara M;Sanchez A;Borde V;Shinohara A;Hochwagen A
忠实的减数分裂染色体分离和生育需要同源染色体之间的减数分裂重组，而不是同样可用的姐妹染色单体，在酿酒酵母中的偏见取决于减数分裂激酶，Mek 1。Mek 1被认为通过特异性抑制姐妹定向修复来介导修复模板偏倚。相反，我们发现，当Mek 1持续紧密配对（突触）同源物，DNA修复严重延迟，这表明Mek 1抑制任何近端修复模板。因此，Mek 1被排除在野生型细胞中的突触同源物之外。排除需要AAA+-ATP酶Pch 2，并直接耦合到联会复合体组装。阶段特异性耗竭实验进一步证明，在突触同源物的背景下，DNA修复需要Rad 54，一种被Mek 1抑制的修复因子。这些数据表明，姐妹模板是区别于同源物，主要是通过其更接近抑制Mek 1活性。我们建议，一旦配对或突触并列同源物，排除Mek 1是必要的，以避免抑制所有模板和加速修复进程。在酵母中的实验表明，联会复合体的一个功能是使染色体结合的Mek 1激酶失活，从而促进完全配对的减数分裂染色体上的DNA修复，并有助于促进同源染色体之间的重组。减数分裂中的染色体分离错误可能导致不育、胎儿丢失或出生缺陷。为了避免减数分裂染色体分离错误，在先前未连接的同源染色体之间建立重组介导的连锁。这样的重组事件起始于DNA中的断裂，但是这些断裂如何优先使用远端同源染色体而不是物理上更接近的相似序列的姐妹染色单体来修复还不清楚。芽殖酵母中减数分裂修复模板偏向性依赖于Mek 1的功能，Mek 1是一种减数分裂特异性蛋白激酶。先前的模型表明，Mek 1活性通过抑制与姐妹染色单体的修复而产生修复模板偏倚。我们发现Mek 1定位于减数分裂染色体上，直到同源配对并紧密对齐。去除Mek 1需要在减数分裂染色体之间组装一个保守的拉链样结构，称为联会复合体。DNA断裂修复延迟突变体中，Mek 1坚持密切对齐的同源物。这些发现表明，持续的Mek 1活性可以抑制所有模板的修复，联会复合体的功能之一是从染色体中去除这种活性。我们的研究结果建立在以前的模型，提出Mek 1活性创建一个局部区域的修复抑制，通常避免了空间上遥远的同源染色体，以促进修复模板的偏见。
Faithful meiotic chromosome segregation and fertility require meiotic recombination between homologous chromosomes rather than the equally available sister chromatid, a bias that in Saccharomyces cerevisiae depends on the meiotic kinase, Mek1. Mek1 is thought to mediate repair template bias by specifically suppressing sister-directed repair. Instead, we found that when Mek1 persists on closely paired (synapsed) homologues, DNA repair is severely delayed, suggesting that Mek1 suppresses any proximal repair template. Accordingly, Mek1 is excluded from synapsed homologues in wild-type cells. Exclusion requires the AAA+-ATPase Pch2 and is directly coupled to synaptonemal complex assembly. Stage-specific depletion experiments further demonstrate that DNA repair in the context of synapsed homologues requires Rad54, a repair factor inhibited by Mek1. These data indicate that the sister template is distinguished from the homologue primarily by its closer proximity to inhibitory Mek1 activity. We propose that once pairing or synapsis juxtaposes homologues, exclusion of Mek1 is necessary to avoid suppression of all templates and accelerate repair progression. Experiments in yeast indicate that one function of the synaptonemal complex is to disable chromosome-bound Mek1 kinase, thereby promoting DNA repair on fully paired meiotic chromosomes and helping to favor recombination between homologues over sister chromatids. Chromosome segregation errors during meiosis may cause infertility, fetal loss, or birth defects. To avoid meiotic chromosome segregation errors, recombination-mediated linkages are established between previously unattached homologous chromosomes. Such recombination events initiate with breaks in the DNA, but how these breaks are preferentially repaired using the distal homologous chromosome, rather than the physically more proximal sister chromatid of similar sequence, is not well understood. Meiotic repair-template bias in the budding yeast depends on the function of Mek1, a meiosis-specific protein kinase. Previous models suggested that Mek1 activity creates repair-template bias by suppressing repair with the sister chromatid. We found that Mek1 localizes on meiotic chromosomes until the homologues pair and closely align. Removal of Mek1 requires the assembly of a conserved zipper-like structure between meiotic chromosomes, known as the synaptonemal complex. DNA break repair is delayed in mutants in which Mek1 persists on closely aligned homologues. These findings suggest that persistent Mek1 activity can suppress repair from all templates, and that one function of the synaptonemal complex is to remove this activity from chromosomes. Our findings build on previous models to propose that Mek1 activity creates a local zone of repair suppression that is normally avoided by the spatially distant homologous chromosome to promote repair-template bias.