Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo, Japan; Division of Functional Genomics, Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, Himeji, Japan.
Division of Experimental Pathology, Cancer Institute of the Japanese Foundation for Cancer Research, Tokyo, Japan.
Curr Biol. 2021 Apr 26;31(8):1581-1591.e3. doi: 10.1016/j.cub.2021.01.062. Epub 2021 Mar 1.
The spindle-assembly checkpoint facilitates mitotic fidelity by delaying anaphase onset in response to microtubule vacancy at kinetochores. Following microtubule attachment, kinetochores receive microtubule-derived force, which causes kinetochores to undergo repetitive cycles of deformation; this phenomenon is referred to as kinetochore stretching. The nature of the forces and the relevance relating this deformation are not well understood. Here, we show that kinetochore stretching occurs within a framework of single end-on attached kinetochores, irrespective of microtubule poleward pulling force. An experimental method to conditionally interfere with the stretching allowed us to determine that kinetochore stretching comprises an essential process of checkpoint silencing by promoting PP1 phosphatase recruitment after the establishment of end-on attachments and removal of the majority of checkpoint-activating kinase Mps1 from kinetochores. Remarkably, we found that a lower frequency of kinetochore stretching largely correlates with a prolonged metaphase in cancer cell lines with chromosomal instability. Perturbation of kinetochore stretching and checkpoint silencing in chromosomally stable cells produced anaphase bridges, which can be alleviated by reducing chromosome-loaded cohesin. These observations indicate that kinetochore stretching-mediated checkpoint silencing provides an unanticipated etiology underlying chromosomal instability and underscores the importance of a rapid metaphase-to-anaphase transition in sustaining mitotic fidelity.
纺锤体组装检查点通过响应动粒处微管空位延迟后期起始来促进有丝分裂保真度。微管附着后，动粒会受到微管衍生的力，这会导致动粒反复变形；这种现象被称为动粒拉伸。力的性质和这种变形的相关性尚不清楚。在这里，我们表明，无论微管向极拉动的力如何，动粒拉伸都是在单端附着的动粒框架内发生的。一种条件干扰拉伸的实验方法使我们能够确定，动粒拉伸包括通过在端对端附着建立后促进 PP1 磷酸酶的募集以及从动粒中去除大部分检查点激活激酶 Mps1 来沉默检查点的一个基本过程。值得注意的是，我们发现，较低频率的动粒拉伸在染色体不稳定的癌细胞系中与中期延长有很大的相关性。在染色体稳定的细胞中，动粒拉伸和检查点沉默的扰乱会产生后期桥，这可以通过减少染色体负载的黏连蛋白来缓解。这些观察结果表明，动粒拉伸介导的检查点沉默为染色体不稳定提供了一种意想不到的病因，并强调了快速从中期到后期过渡在维持有丝分裂保真度方面的重要性。
