Department of Biochemistry, University of Oxford, Oxford, UK.
Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
J Cell Biol. 2019 Apr 1;218(4):1108-1117. doi: 10.1083/jcb.201808015. Epub 2019 Jan 23.
Cyclin B-dependent kinase (CDK1-CCNB1) promotes entry into mitosis. Additionally, it inhibits mitotic exit by activating the spindle checkpoint. This latter role is mediated through phosphorylation of the checkpoint kinase MPS1 and other spindle checkpoint proteins. We find that CDK1-CCNB1 localizes to unattached kinetochores and like MPS1 is lost from these structures upon microtubule attachment. This suggests that CDK1-CCNB1 is an integral component and not only an upstream regulator of the spindle checkpoint pathway. Complementary proteomic and cell biological analysis demonstrate that the spindle checkpoint protein MAD1 is one of the major components of CCNB1 complexes, and that CCNB1 is recruited to unattached kinetochores in an MPS1-dependent fashion through interaction with the first 100 amino acids of MAD1. This MPS1 and MAD1-dependent pool of CDK1-CCNB1 creates a positive feedback loop necessary for timely recruitment of MPS1 to kinetochores during mitotic entry and for sustained spindle checkpoint arrest. CDK1-CCNB1 is therefore an integral component of the spindle checkpoint, ensuring the fidelity of mitosis.
周期蛋白依赖性激酶 (CDK1-CCNB1) 促进有丝分裂的进入。此外，它通过激活纺锤体检查点来抑制有丝分裂退出。后一种作用是通过磷酸化检查点激酶 MPS1 和其他纺锤体检查点蛋白来介导的。我们发现 CDK1-CCNB1 定位于未连接的动粒上，并且像 MPS1 一样，在微管附着时从这些结构中丢失。这表明 CDK1-CCNB1 是纺锤体检查点途径的一个组成部分，而不仅仅是其上游调节剂。互补的蛋白质组学和细胞生物学分析表明，纺锤体检查点蛋白 MAD1 是 CCNB1 复合物的主要成分之一，并且 CCNB1 通过与 MAD1 的前 100 个氨基酸相互作用，以 MPS1 依赖性的方式被招募到未连接的动粒上。这个 MPS1 和 MAD1 依赖性的 CDK1-CCNB1 池为有丝分裂进入时 MPS1 及时被招募到动粒以及持续的纺锤体检查点停滞创造了一个正反馈回路。因此，CDK1-CCNB1 是纺锤体检查点的一个组成部分，确保了有丝分裂的保真度。
