Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523.
Wellcome Trust Centre for Cell Biology, University of Edinburgh, EH9 3BF Edinburgh, UK.
Mol Biol Cell. 2020 Jul 1;31(14):1453-1473. doi: 10.1091/mbc.E20-05-0286. Epub 2020 May 13.
The conserved kinetochore-associated NDC80 complex (composed of Hec1/Ndc80, Nuf2, Spc24, and Spc25) has well-documented roles in mitosis including 1) connecting mitotic chromosomes to spindle microtubules to establish force-transducing kinetochore-microtubule attachments and 2) regulating the binding strength between kinetochores and microtubules such that correct attachments are stabilized and erroneous attachments are released. Although the NDC80 complex plays a central role in forming and regulating attachments to microtubules, additional factors support these processes as well, including the spindle and kinetochore-associated (Ska) complex. Multiple lines of evidence suggest that Ska complexes strengthen attachments by increasing the ability of NDC80 complexes to bind microtubules, especially to depolymerizing microtubule plus ends, but how this is accomplished remains unclear. Using cell-based and in vitro assays, we demonstrate that the Hec1 tail domain is dispensable for Ska complex recruitment to kinetochores and for generation of kinetochore-microtubule attachments in human cells. We further demonstrate that Hec1 tail phosphorylation regulates kinetochore-microtubule attachment stability independently of the Ska complex. Finally, we map the location of the Ska complex in cells to a region near the coiled-coil domain of the NDC80 complex and demonstrate that this region is required for Ska complex recruitment to the NDC80 complex--microtubule interface.
保守的着丝粒相关 NDC80 复合物(由 Hec1/Ndc80、Nuf2、Spc24 和 Spc25 组成)在有丝分裂中具有明确的作用,包括 1)将有丝分裂染色体连接到纺锤体微管上,以建立力传递的着丝粒-微管附着;2)调节着丝粒和微管之间的结合强度,以使正确的附着稳定,错误的附着释放。尽管 NDC80 复合物在形成和调节微管附着中发挥着核心作用,但其他因素也支持这些过程,包括纺锤体和着丝粒相关(Ska)复合物。多条证据表明,Ska 复合物通过增加 NDC80 复合物结合微管的能力,特别是结合微管去聚合端的能力,来增强附着,但具体如何实现这一过程仍不清楚。我们通过基于细胞的和体外测定,证明 Hec1 尾部结构域对于 Ska 复合物向着丝粒的募集以及在人类细胞中产生着丝粒-微管附着是可有可无的。我们进一步证明,Hec1 尾部磷酸化可独立于 Ska 复合物调节着丝粒-微管附着的稳定性。最后,我们将 Ska 复合物在细胞中的位置映射到 NDC80 复合物的卷曲螺旋结构域附近,并证明该区域是 Ska 复合物募集到 NDC80 复合物-微管界面所必需的。