Analysis of fission yeast chromosome architecture in meiotic prophase

在有丝分裂细胞周期中，姐妹染色单体的调节凝聚和分离是由有丝分裂粘附素复合体实现的，当进入减数分裂时，这种有丝分裂粘附素复合体被编排减数分裂特异染色体事件的减数分裂粘附素复合体所取代。减数分裂粘附素Rec8是姐妹染色单体凝聚和同源重组所必需的。通过直接测量裂殖酵母活细胞中的染色体紧密性，我们发现在减数分裂前期，粘附素在染色体紧密性中还有一个额外的作用。在缺乏Rec8的情况下，与野生型细胞相比，染色体松动了2倍，而粘附素相关蛋白Pds5的丢失导致了依赖于Rec8的过度紧凑。在没有Rec8或Pds5的情况下，同源配对和重组都是有缺陷的。PDS5还显示了在维持姐妹染色单体凝聚力和减少染色体分离方面的作用。在没有Pds5的情况下，Rec8在染色体上的结合减少，这表明Pds5调节了Rec8与减数分裂染色体的结合。因此，粘附素调节了全球染色质结构的根本变化，促进了正确的减数分裂进程。

During the mitotic cell cycle the regulated cohesion and segregation of sister chromatids is achieved by the mitotic cohesin complex, and upon entering meiosis, this mitotic cohesin complex is replaced by the meiotic cohesin complex which choreographs the meiosis-specific chromosomal events. The meiotic cohesin, Rec8, is required for sister chromatid cohesion and homologous recombination. By directly measuring chromosome compaction in living cells of the fission yeast Schizosaccharomyces pombe, we found an additional role for cohesin in the compaction of chromosomes during meiotic prophase. In the absence of Rec8, chromosomes were loosened 2 fold when compared with wild-type cells, while the loss of the cohesin-associated protein, Pds5, resulted in Rec8-dependent over-compaction. Both homologous pairing and recombination were defective in the absence of either Rec8 or Pds5. Pds5 also demonstrated a role in maintaining sister chromatid cohesion and in reductional chromosome segregation. In the absence of Pds5, the Rec8 binding on chromosome was decreased, indicating that Pds5 modulate the association of Rec8 with meiotic chromosomes. Thus, the cohesins mediate fundamental changes in global chromatin structure that promote correct meiotic progression.