The CENP-F-like proteins HCP-1 and HCP-2 target CLASP to kinetochores to mediate chromosome segregation
The CENP-F-like proteins HCP-1 and HCP-2 target CLASP to kinetochores to mediate chromosome segregation
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DOI：
10.1016/j.cub.2005.03.018
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发表时间：
2005-04-26
期刊：
影响因子：
9.2
通讯作者：
Desai, A
中科院分区：
文献类型：
--
作者：
Cheeseman, IM;MacLeod, I;Desai, A
在染色体分离过程中，动点与纺锤体微管形成动态连接。在脊椎动物中，这些附着需要一些外部动粒蛋白的活性，包括CENP-F[1，2]和广泛保守的微管相关蛋白CLAP[3]。在这里，我们研究了秀丽线虫中两个冗余的CENP-F样蛋白hcp-1/2和CLASP(CLS-2)之间的功能关系。HCP-1/2和CLAP(CLS-2)以几乎相同的动力学曲线瞬时定位于线虫有丝分裂着丝点，生化纯化表明它们也存在物理联系。在hcp-1/2缺失的胚胎中，CLASP(CLS-2)不再定位于染色体，而CLASP(CLS-2)缺失不能阻止hcp-1/2靶向。与定位依赖和生化关联一致，hcp-1/2或CLASP(CLS-2)的缺失导致了以姐妹染色单体双向定位失败为特征的有丝分裂染色体分离的几乎相同的缺陷。在1细胞胚胎中，这种表型可以通过破坏将纺锤体两极分开的星体力而部分被抑制，这表明当染色体-纺锤体附着受到向极力作用时，双向需要CLASP(CLS-2)。我们的结果证明，hcp-1/2的关键作用是将CLAP(CLS-2)靶向动粒，并支持最近提出的模型，即CLASP功能促进动粒结合微管的聚合[4]。
During chromosome segregation, kinetochores form dynamic connections with spindle microtubules. In vertebrates, these attachments require the activities of a number of outer kinetochore proteins, including CENP-F [1, 2] and the widely conserved microtubule-associated protein CLASP [3]. Here, we investigate the functional relationship between HCP-1/2, two redundant CENP-F-like proteins, and CLASP(CLS-2) in Caenorhabditis elegans. HCP-1/2 and CLASP(CLS-2) localize transiently to mitotic C. elegans kinetochores with nearly identical kinetic profiles, and biochemical purifications demonstrate that they also associate physically. In embryos depleted of HCP-1/2, CLASP(CLS-2) no longer localizes to chromosomes, whereas CLASP(CLS-2) depletion does not prevent HCP-1/2 targeting. Consistent with the localization dependency and biochemical association, depletion of HCP-1/2 or CLASP(CLS-2) resulted in virtually identical defects in mitotic chromosome segregation characterized by a failure of sister-chromatid biorientation. This phenotype could be partially suppressed by disrupting the astral forces that pull spindle poles apart in the 1 cell embryo, indicating that CLASP(CLS-2) is required for biorientation when chromosome-spindle attachments are subjected to poleward force. Our results establish that the key role of HCP-1/2 is to target CLASP(CLS-2) to kinetochores, and they support the recently proposed model that CLASP functions to promote the polymerization of kinetochore bound microtubules [4].