Prevo Bram, Cheerambathur Dhanya K, Earnshaw William C, Desai Arshad
Ludwig Institute for Cancer Research, La Jolla, California 92093, USA.
Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, Scotland, UK.
bioRxiv. 2023 Mar 24:2023.03.23.534015. doi: 10.1101/2023.03.23.534015.
Multiple microtubule-directed activities concentrate on chromosomes during mitosis to ensure their accurate distribution to daughter cells. These activities include couplers and dynamics regulators localized at the kinetochore, the specialized microtubule interface built on centromeric chromatin, as well as motor proteins recruited to kinetochores and to mitotic chromatin. Here, we describe an reconstruction approach in which the effect of removing the major microtubule-directed activities on mitotic chromosomes is compared to the selective presence of individual activities. This approach revealed that the kinetochore dynein module, comprised of the minus end-directed motor cytoplasmic dynein and its kinetochore-specific adapters, is sufficient to biorient chromosomes and to remodel outer kinetochore composition following microtubule attachment; by contrast, the kinetochore dynein module is unable to support chromosome congression. The chromosome-autonomous action of kinetochore dynein, in the absence of the other major microtubule-directed factors on chromosomes, rotates and orients a substantial proportion of chromosomes such that their sister chromatids attach to opposite spindle poles. In tight coupling with orientation, the kinetochore dynein module drives removal of outermost kinetochore components, including the dynein motor itself and spindle checkpoint activators. The removal is independent of the other major microtubule-directed activities and kinetochore-localized protein phosphatase 1, suggesting that it is intrinsic to the kinetochore dynein module. These observations indicate that the kinetochore dynein module has the ability coordinate chromosome biorientation with attachment state-sensitive remodeling of the outer kinetochore that facilitates cell cycle progression.
在有丝分裂期间，多种微管导向活动集中于染色体上，以确保它们准确分配到子细胞中。这些活动包括定位于动粒的偶联蛋白和动力学调节剂，动粒是建立在着丝粒染色质上的特殊微管界面，以及募集到动粒和有丝分裂染色质上的运动蛋白。在这里，我们描述了一种重建方法，即将去除主要微管导向活动对有丝分裂染色体的影响与个别活动的选择性存在进行比较。该方法表明，由负端定向运动蛋白胞质动力蛋白及其动粒特异性衔接蛋白组成的动粒动力蛋白模块足以使染色体双定向，并在微管附着后重塑动粒外层组成；相比之下，动粒动力蛋白模块无法支持染色体向赤道板汇聚。在染色体上不存在其他主要微管导向因子的情况下，动粒动力蛋白的染色体自主作用会旋转并使相当一部分染色体定向，从而使其姐妹染色单体附着于相反的纺锤体极。与定向紧密耦合的是，动粒动力蛋白模块驱动去除最外层的动粒成分，包括动力蛋白本身和纺锤体检查点激活剂。这种去除独立于其他主要的微管导向活动和定位于动粒的蛋白磷酸酶1，表明这是动粒动力蛋白模块所固有的。这些观察结果表明，动粒动力蛋白模块有能力将染色体双定向与动粒外层的附着状态敏感重塑相协调，从而促进细胞周期进程。
