MPS1/Mph1 phosphorylates the kinetochore protein KNL1/Spc7 to recruit SAC components
MPS1/Mph1 phosphorylates the kinetochore protein KNL1/Spc7 to recruit SAC components
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DOI：
10.1038/ncb2515
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发表时间：
2012-07-01
影响因子：
21.3
通讯作者：
Watanabe, Yoshinori
中科院分区：
文献类型：
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作者：
Yamagishi, Yuya;Yang, Ching-Hui;Watanabe, Yoshinori
所有生物体的基因组稳定性取决于染色体与子细胞的精确分配。纺锤体组装检查点（SAC）检测未附着的着丝点并防止过早进入后期，从而确保在有丝分裂期间所有染色体都附着在相反的纺锤体极点（双向）上(1)。MPS1是一种进化上保守的蛋白激酶，是SAC和染色体双向定位所必需的（2-4）。然而，其主要的细胞基质仍然难以捉摸。我们发现，裂变酵母Mph1 （MPS1同源物）磷酸化了熔融重复序列上的着丝粒蛋白Spc7 （KNL1/Blinkin同源物）。这种磷酸化促进了体外与Bub1-Bub3复合物的结合，这是基于着丝酶的SAC激活（Mad1-Mad2-Mad3定位）和染色体排列所必需的。因此，不可磷酸化的spc7-12A突变消除了Bub1-Bub3的着丝点靶向，而磷酸化模拟的spc7-12E突变迫使它们在整个细胞周期中定位于着丝点，即使在没有Mph1的情况下。因此，MPS1/Mph1激酶位于未附着的着丝点上，最初会产生一个标记，这对SAC激活和染色体双向定位至关重要。这种机制似乎在人类细胞中是保守的。
The genomic stability of all organisms depends on the precise partition of chromosomes to daughter cells. The spindle assembly checkpoint (SAC) senses unattached kinetochores and prevents premature entry to anaphase, thus ensuring that all chromosomes attach to opposite spindle poles (bi-orientation) during mitosis(1). MPS1 is an evolutionarily conserved protein kinase required for the SAC and chromosome bi-orientation(2-4). Yet, its primary cellular substrate has remained elusive. We show that fission yeast Mph1 (MPS1 homologue) phosphorylates the kinetochore protein Spc7 (KNL1/Blinkin homologue) at the MELT repeat sequences. This phosphorylation promotes the-in vitro binding to the Bub1-Bub3 complex, which is required for kinetochore-based SAC activation (Mad1-Mad2-Mad3 localization) and chromosome alignment. Accordingly, a non-phosphorylatable spc7-12A mutation abolishes kinetochore targeting of Bub1-Bub3, whereas a phospho-mimetic spc7-12E mutation forces them to localize at kinetochores throughout the entire cell cycle, even in the absence of Mph1. Thus, MPS1/Mph1 kinase locating at the unattached kinetochores initially creates a mark, which is crucial for SAC activation and chromosome bi-orientation. This mechanism seems to be conserved in human cells.