Maciejowski John, Drechsler Hauke, Grundner-Culemann Kathrin, Ballister Edward R, Rodriguez-Rodriguez Jose-Antonio, Rodriguez-Bravo Veronica, Jones Mathew J K, Foley Emily, Lampson Michael A, Daub Henrik, McAinsh Andrew D, Jallepalli Prasad V
Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Louis V. Gerstner, Jr. Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
Centre for Mechanochemical Cell Biology, Division of Biomedical Science, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK.
Dev Cell. 2017 Apr 24;41(2):143-156.e6. doi: 10.1016/j.devcel.2017.03.025.
The spindle assembly checkpoint kinase Mps1 not only inhibits anaphase but also corrects erroneous attachments that could lead to missegregation and aneuploidy. However, Mps1's error correction-relevant substrates are unknown. Using a chemically tuned kinetochore-targeting assay, we show that Mps1 destabilizes microtubule attachments (K fibers) epistatically to Aurora B, the other major error-correcting kinase. Through quantitative proteomics, we identify multiple sites of Mps1-regulated phosphorylation at the outer kinetochore. Substrate modification was microtubule sensitive and opposed by PP2A-B56 phosphatases that stabilize chromosome-spindle attachment. Consistently, Mps1 inhibition rescued K-fiber stability after depleting PP2A-B56. We also identify the Ska complex as a key effector of Mps1 at the kinetochore-microtubule interface, as mutations that mimic constitutive phosphorylation destabilized K fibers in vivo and reduced the efficiency of the Ska complex's conversion from lattice diffusion to end-coupled microtubule binding in vitro. Our results reveal how Mps1 dynamically modifies kinetochores to correct improper attachments and ensure faithful chromosome segregation.
纺锤体组装检查点激酶Mps1不仅能抑制后期，还能纠正可能导致错误分离和非整倍体的错误连接。然而，与Mps1错误校正相关的底物尚不清楚。通过一种化学调控的着丝粒靶向分析，我们发现Mps1在功能上先于另一种主要的错误校正激酶Aurora B，使微管连接（动粒纤维）不稳定。通过定量蛋白质组学，我们在着丝粒外侧鉴定出多个受Mps1调控的磷酸化位点。底物修饰对微管敏感，并受到稳定染色体-纺锤体连接的PP2A-B56磷酸酶的抑制。一致地，在耗尽PP2A-B56后，抑制Mps1可挽救动粒纤维的稳定性。我们还确定Ska复合体是Mps1在着丝粒-微管界面的关键效应器，因为模拟组成型磷酸化的突变在体内使动粒纤维不稳定，并降低了Ska复合体在体外从晶格扩散转变为端耦合微管结合的效率。我们的结果揭示了Mps1如何动态修饰着丝粒以纠正不正确的连接并确保染色体的准确分离。
