Tying synaptonemal complex initiation to the formation and programmed repair of DNA double-strand breaks
Tying synaptonemal complex initiation to the formation and programmed repair of DNA double-strand breaks
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DOI：
10.1073/pnas.0400843101
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发表时间：
2004-03-30
影响因子：
11.1
通讯作者：
Keeney, S
中科院分区：
文献类型：
--
作者：
Henderson, KA;Keeney, S
在减数分裂期间，同源染色体重组并在突触复合体（SC）内沿其长度紧密地相对。部分原因是，在许多生物体中，Spo11既需要产生启动重组的双链断裂（dsb），也需要促进正常SC的形成，因此很明显，这两个过程是密切相关的。这种连锁的分子性质尚不清楚，但有人提出SC的形成是在正在进行的重组位点局部启动的，特别是在最终产生交叉的位点子集上。为了验证这一假设，我们进一步研究了酿酒酵母中DSBs和SC形成之间的关系。在一系列不同DSB频率的spo11错义突变体中监测sc。阻断DSB形成的等位基因使SC表型与缺失突变难以区分，部分功能丧失突变与逐渐加重的DSB缺陷导致SC形成的相应缺陷。这些结果强烈地将SC的形成与Spo11催化活性本身联系起来。当Spo11活性降低时，被认为代表SC起始位点的染色体上Zip3复合物的数量也会减少，但以一种明显的非线性方式：次形Spo11等位基因在DSB形成过程中比Zip3复合物形成过程中造成更大的缺陷。Zip3的非线性响应与交叉重组产物的响应非常相似。Zip3聚焦、SC形成和交叉之间的定量关系强烈暗示交叉指定的重组中间体是SC起始的位点。
During meiosis, homologous chromosomes recombine and become closely apposed along their lengths within the synaptonemal complex (SC). In part because Spo11 is required both to make the double-strand breaks (DSBs) that initiate recombination and to promote normal SC formation in many organisms, it is clear that these two processes are intimately coupled. The molecular nature of this linkage is not well understood, but it has been proposed that SC formation initiates locally at the sites of ongoing recombination and in particular at the subset of sites that will eventually give rise to crossovers. To test this hypothesis, we examined further the relationship between DSBs and SC formation in Saccharomyces cerevisiae. SCs were monitored in a series of spo11 missense mutants with varying DSB frequencies. Alleles that blocked DSB formation gave SC phenotypes indistinguishable from a deletion mutant, and partial loss-of-function mutations with progressively more severe DSB defects caused corresponding defects in SC formation. These results strongly correlate SC formation with Spo11 catalytic activity per se. Numbers of Zip3 complexes on chromosomes, thought to represent the sites of SC initiation, also declined when Spo11 activity decreased, but in a markedly nonlinear fashion: hypomorphic spo11 alleles caused larger defects in DSB formation than in Zip3 complex formation. This nonlinear response of Zip3 closely paralleled the response of crossover recombination products. The quantitative relationship between Zip3 foci, SC formation, and crossing over strongly implicates crossover-designated recombination intermediates as the sites of SC initiation.