Meiotic chromosome structures constrain and respond to designation of crossover sites.
Meiotic chromosome structures constrain and respond to designation of crossover sites.
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同源染色体之间的交叉（CO）重组事件是形成交叉所必需的，交叉是同源染色体之间的临时连接，以确保它们在减数分裂I时正确分离。尽管需要CO和作为减数分裂重组起始事件的过量双链DNA断裂（DSB），但大多数生物体在每个染色体对上产生的CO很少。此外，CO倾向于抑制同一对染色体上附近其他CO的形成，这是一种鲜为人知的现象，称为CO干扰。在这里，我们表明，联会复合体（SC），减数分裂特定的结构，组装对齐同源染色体之间，既约束，并改变了CO重组事件。利用秀丽隐杆线虫中CO位点的细胞学标记，我们证明了SC中心区蛋白（SYPs）的部分耗尽减弱了CO干扰，提高了CO并减少了干扰操作的有效距离，表明SYPs限制了CO。此外，我们发现CO与染色体轴长度局部增加0.4-0.5 μm相关。我们建议，减数分裂CO调节作为一个自我限制的系统中，减数分裂染色体结构建立一个环境，促进CO的形成，这反过来又改变染色体结构，以抑制其他CO在其他网站。
Crossover (CO) recombination events between homologous chromosomes are required to form chiasmata, temporary connections between homologs that ensure their proper segregation at meiosis I. Despite this requirement for COs and an excess of the double-strand DNA breaks (DSBs) that are the initiating events for meiotic recombination, most organisms make very few COs per chromosome pair. Moreover, COs tend to inhibit the formation of other COs nearby on the same chromosome pair, a poorly understood phenomenon known as CO interference. Here we show that the synaptonemal complex (SC), a meiosis-specific structure that assembles between aligned homologous chromosomes, both constrains and is altered by CO recombination events. Utilizing a cytological marker of CO sites in Caenorhabditis elegans, we demonstrate that partial depletion of the SC central region proteins (SYPs) attenuates CO interference, elevating COs and reducing the effective distance over which interference operates, indicating that SYPs limit COs. Moreover, we show that COs are associated with a local 0.4-0.5 μm increase in chromosome axis length. We propose that meiotic CO regulation operates as a self-limiting system in which meiotic chromosome structures establish an environment that promotes CO formation, which in turn alters chromosome structure to inhibit other COs at additional sites.
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