Chiasmata promote monopolar attachment of sister chromatids and their co-segregation toward the proper pole during meiosis I.
Chiasmata promote monopolar attachment of sister chromatids and their co-segregation toward the proper pole during meiosis I.
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Chiasmata促进姐妹染色单体的单极附着及其在减数分裂时的共隔离。
DOI：
10.1371/journal.pgen.1001329
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发表时间：
2011-03
期刊：
影响因子：
4.5
通讯作者：
Yamamoto A
中科院分区：
文献类型：
--
作者：
Hirose Y;Suzuki R;Ohba T;Hinohara Y;Matsuhara H;Yoshida M;Itabashi Y;Murakami H;Yamamoto A
交叉是在一对同源染色体之间通过交叉重组形成的结构，并且在减数分裂期间物理地连接同源染色体。在减数分裂Ⅰ中，交叉对于同源染色体与纺锤体两极的连接（双极连接）以及随后的分离是必不可少的。然而，在减数分裂过程中交叉的整体功能尚未完全了解。在这里，我们表明，交叉也发挥了至关重要的作用，在附件中的姐妹染色单体相同的纺锤体极，并在他们的共同分离在减数分裂I在分裂酵母。对缺乏交叉和内聚蛋白保护剂Sgo 1的细胞的分析表明，交叉的缺失导致分裂后期姐妹染色单体的频繁双极附着。此外，对不同类型的交叉和非交叉细胞，包括那些缺乏DNA复制检查点因子Mrc 1或减数分裂着丝粒蛋白Moa 1的细胞中的着丝粒动力学的高时间分辨率分析显示了以下三个结果：（i）在后期前阶段，姐妹染色单体的双极附着发生而与交叉形成无关;（ii）交叉有助于消除后期前的双极附着;（iii）当双极附着在后期期间保持时，交叉在向极染色体拉动期间产生朝向适当极的偏向，这导致适当的染色体分离。基于这些结果，我们提出，交叉在选择适当的附件中起着关键作用，并提供了一个备份机制，促进正确的染色体分离时，不适当的附件仍然在后期I。配子通过一种特殊的细胞分裂方式形成，称为减数分裂。在减数分裂过程中，两次核分裂相继发生;第一次分裂仅特异于减数分裂，因为同源染色体彼此分离。同源染色体分离需要同源染色体通过在重组位点形成的称为交叉的结构的物理联合。这种关联被认为有助于同源染色体与纺锤体的正确连接，导致它们的正确分离。在这项研究中，我们研究了交叉在第一次分裂的裂殖酵母染色体动力学和分离分析在几个不同的突变体缺乏交叉的功能。我们发现，除了适当的同源染色体的纺锤体附着，交叉有助于适当的纺锤体附着的复制染色体比以前认为的更多。此外，即使染色体不正确地附着在纺锤体上，交叉最终也会导致正确的染色体分离。我们的研究结果加强了同源染色体的物理协会在正确的纺锤体连接的染色体的意义，并揭示了一个以前未被识别的，交叉依赖的机制，确保正确的染色体分离。
The chiasma is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis. Chiasmata are essential for the attachment of the homologous chromosomes to opposite spindle poles (bipolar attachment) and their subsequent segregation to the opposite poles during meiosis I. However, the overall function of chiasmata during meiosis is not fully understood. Here, we show that chiasmata also play a crucial role in the attachment of sister chromatids to the same spindle pole and in their co-segregation during meiosis I in fission yeast. Analysis of cells lacking chiasmata and the cohesin protector Sgo1 showed that loss of chiasmata causes frequent bipolar attachment of sister chromatids during anaphase. Furthermore, high time-resolution analysis of centromere dynamics in various types of chiasmate and achiasmate cells, including those lacking the DNA replication checkpoint factor Mrc1 or the meiotic centromere protein Moa1, showed the following three outcomes: (i) during the pre-anaphase stage, the bipolar attachment of sister chromatids occurs irrespective of chiasma formation; (ii) the chiasma contributes to the elimination of the pre-anaphase bipolar attachment; and (iii) when the bipolar attachment remains during anaphase, the chiasmata generate a bias toward the proper pole during poleward chromosome pulling that results in appropriate chromosome segregation. Based on these results, we propose that chiasmata play a pivotal role in the selection of proper attachments and provide a backup mechanism that promotes correct chromosome segregation when improper attachments remain during anaphase I. Gametes form through a special type of cell division called meiosis. During meiosis, two nuclear divisions take place successively; the first division is specific only to meiosis, in that homologous chromosomes segregate from each other. Homologous chromosome segregation requires physical association of the homologous chromosomes by a structure called chiasma that forms at the site of recombination. This association is thought to contribute to proper attachment of homologous chromosomes to the spindle, leading to their proper segregation. In this study, we examined the functions of chiasmata during the first division in fission yeast by analyzing chromosome dynamics and segregation in several different mutants lacking chiasmata. We found that, in addition to proper spindle attachment of homologous chromosomes, chiasmata contribute to proper spindle attachment of replicated chromosomes more substantially than previously had been thought. In addition, even when chromosomes are improperly attached to the spindle, chiasmata eventually cause proper chromosome segregation. Our findings reinforce the significance of the physical association of homologous chromosomes in proper spindle attachment of chromosomes and have unveiled a previously unidentified, chiasma-dependent mechanism that ensures proper chromosome segregation.
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