Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03766, USA.
EMBO J. 2010 Oct 20;29(20):3531-43. doi: 10.1038/emboj.2010.230. Epub 2010 Sep 17.
Accurate chromosome segregation during mitosis requires precise coordination of various processes, such as chromosome alignment, maturation of proper kinetochore-microtubule (kMT) attachments, correction of erroneous attachments, and silencing of the spindle assembly checkpoint (SAC). How these fundamental aspects of mitosis are coordinately and temporally regulated is poorly understood. In this study, we show that the temporal regulation of kMT attachments by CLASP1, astrin and Kif2b is central to mitotic progression and chromosome segregation fidelity. In early mitosis, a Kif2b-CLASP1 complex is recruited to kinetochores to promote chromosome movement, kMT turnover, correction of attachment errors, and maintenance of SAC signalling. However, during metaphase, this complex is replaced by an astrin-CLASP1 complex, which promotes kMT stability, chromosome alignment, and silencing of the SAC. We show that these two complexes are differentially recruited to kinetochores and are mutually exclusive. We also show that other kinetochore proteins, such as Kif18a, affect kMT attachments and chromosome movement through these proteins. Thus, CLASP1-astrin-Kif2b complex act as a central switch at kinetochores that defines mitotic progression and promotes fidelity by temporally regulating kMT attachments.
有丝分裂过程中染色体的精确分离需要各种过程的精确协调,例如染色体的排列、适当的动粒-微管(kMT)连接的成熟、错误连接的纠正以及纺锤体组装检查点(SAC)的沉默。这些有丝分裂的基本方面是如何协调和时间调节的还知之甚少。在这项研究中,我们表明 CLASP1、astrin 和 Kif2b 对 kMT 连接的时间调节对于有丝分裂的进展和染色体分离的保真度至关重要。在早期有丝分裂中,Kif2b-CLASP1 复合物被招募到动粒上,以促进染色体运动、kMT 周转率、连接错误的纠正以及 SAC 信号的维持。然而,在中期,该复合物被 astrin-CLASP1 复合物取代,该复合物促进 kMT 的稳定性、染色体的排列和 SAC 的沉默。我们表明,这两种复合物以不同的方式被招募到动粒上,并且是相互排斥的。我们还表明,其他动粒蛋白,如 Kif18a,通过这些蛋白影响 kMT 连接和染色体运动。因此,CLASP1-astrin-Kif2b 复合物作为动粒上的中央开关,定义了有丝分裂的进展,并通过时间调节 kMT 连接来促进保真度。