Parnell Emily J, Jenson Erin, Miller Matthew P
Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
bioRxiv. 2023 Nov 7:2023.11.07.566082. doi: 10.1101/2023.11.07.566082.
Accurate chromosome segregation relies on kinetochores carrying out multiple functions, including establishing and maintaining microtubule attachments, forming precise bioriented attachments between sister chromatids, and activating the spindle assembly checkpoint. Central to these processes is the highly conserved Ndc80 complex. This kinetochore subcomplex interacts directly with microtubules, but also serves as a critical platform for recruiting kinetochore-associated factors and as a key substrate for error correction kinases. The precise manner in which these kinetochore factors interact, and regulate each other's function, remains unknown - considerably hindering our understanding of how Ndc80 complex-dependent processes function together to orchestrate accurate chromosome segregation. Here, we aimed to uncover the role of Nuf2's CH domain, a component of the Ndc80 complex, in ensuring accurate chromosome segregation. Through extensive mutational analysis, we identified a conserved "interaction hub" comprising two segments in Nuf2's CH domain, forming the binding site for Mps1 within the yeast Ndc80 complex. Intriguingly, the interaction between Mps1 and the Ndc80 complex seems to be subject to regulation by competitive binding with other factors. Mutants disrupting this interaction hub exhibit defects in spindle assembly checkpoint function and severe chromosome segregation errors. Significantly, specifically restoring Mps1-Ndc80 complex association rescues these defects. Our findings shed light on the intricate regulation of Ndc80 complex-dependent functions and highlight the essential role of Mps1 in kinetochore biorientation and accurate chromosome segregation.
准确的染色体分离依赖于动粒执行多种功能,包括建立和维持微管附着、在姐妹染色单体之间形成精确的双定向附着以及激活纺锤体组装检查点。这些过程的核心是高度保守的Ndc80复合体。这个动粒亚复合体直接与微管相互作用,但也作为招募动粒相关因子的关键平台以及纠错激酶的关键底物。这些动粒因子相互作用以及调节彼此功能的精确方式仍然未知,这极大地阻碍了我们对依赖Ndc80复合体的过程如何协同作用以协调准确的染色体分离的理解。在这里,我们旨在揭示Ndc80复合体的一个组成部分Nuf2的CH结构域在确保准确的染色体分离中的作用。通过广泛的突变分析,我们在Nuf2的CH结构域中鉴定出一个由两个片段组成的保守“相互作用枢纽”,它形成了酵母Ndc80复合体中Mps1的结合位点。有趣的是,Mps1与Ndc80复合体之间的相互作用似乎受到与其他因子竞争性结合的调节。破坏这个相互作用枢纽的突变体在纺锤体组装检查点功能方面表现出缺陷以及严重的染色体分离错误。重要的是,特异性恢复Mps1与Ndc80复合体的结合可挽救这些缺陷。我们的研究结果揭示了Ndc80复合体依赖性功能的复杂调节,并突出了Mps1在动粒双定向和准确的染色体分离中的重要作用。