PDF(Pubmed)
Abstract：
The 16-subunit Constitutive Centromere-associated Network (CCAN)-based inner kinetochore is well-known for connecting centromeric chromatin to the spindle-binding outer kinetochore. Here, we report a non-canonical role for the inner kinetochore in directly regulating sister-chromatid cohesion at centromeres. We provide biochemical, X-ray crystal structure, and intracellular ectopic localization evidence that the inner kinetochore directly binds cohesin, a ring-shaped multi-subunit complex that holds sister chromatids together from S-phase until anaphase onset. This interaction is mediated by binding of the 5-subunit CENP-OPQUR sub-complex of CCAN to the Scc1-SA2 sub-complex of cohesin. Mutation in the CENP-U subunit of the CENP-OPQUR complex that abolishes its binding to the composite interface between Scc1 and SA2 weakens centromeric cohesion, leading to premature separation of sister chromatids during delayed metaphase. We further show that CENP-U competes with the cohesin release factor Wapl for binding the interface of Scc1-SA2, and that the cohesion-protecting role for CENP-U can be bypassed by depleting Wapl. Taken together, this study reveals an inner kinetochore-bound pool of cohesin, which strengthens centromeric sister-chromatid cohesion to resist metaphase spindle pulling forces.
摘要：
众所周知，基于16亚基的组成型着丝粒相关网络（CCAN）的内部动粒将着丝粒染色质连接到纺锤体结合的外部动粒。这里,我们报告了内部动粒在直接调节着丝粒上的姐妹染色单体内聚力中的非规范作用。我们提供生化，X射线晶体结构,和细胞内异位定位证据表明内部动粒直接结合粘附素，一种环状多亚基复合物，将姐妹染色单体从S期保持在一起，直到后期开始。这种相互作用是通过将CCAN的5亚基CENP-OPQUR亚复合物与粘附蛋白的Scc1-SA2亚复合物结合来介导的。CENP-OPQUR复合物的CENP-U亚基的突变消除了其与Scc1和SA2之间的复合界面的结合，从而削弱了着丝粒的内聚力，导致姐妹染色单体在延迟中期过早分离。我们进一步表明，CENP-U与粘附素释放因子Wapl竞争结合Scc1-SA2的界面，并且可以通过耗尽Wapl来绕过CENP-U的内聚保护作用。一起来看,这项研究揭示了一个内在体结合的粘附蛋白池，增强了着丝粒姐妹染色单体的内聚力，以抵抗中期纺锤体的拉力。
