Department of Molecular Oncology, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan.
Sci Rep. 2017 Aug 18;7(1):8794. doi: 10.1038/s41598-017-09114-3.
For faithful chromosome segregation, the formation of stable kinetochore-microtubule attachment and its monitoring by the spindle assembly checkpoint (SAC) are coordinately regulated by mechanisms that are currently ill-defined. Here, we show that polo-like kinase 1 (Plk1), which is instrumental in forming stable kinetochore-microtubule attachments, is also involved in the maintenance of SAC activity by binding to Bub1, but not by binding to CLASP2 or CLIP-170. The effect of Plk1 on the SAC was found to be mediated through phosphorylation of Mps1, an essential kinase for the SAC, as well as through phosphorylation of the MELT repeats in Knl1. Bub1 acts as a platform for assembling other SAC components on the phosphorylated MELT repeats. We propose that Bub1-bound Plk1 is important for the maintenance of SAC activity by supporting Bub1 localization to kinetochores in prometaphase, a time when the kinetochore Mps1 level is reduced, until the formation of stable kinetochore-microtubule attachment is completed. Our study reveals an intricate mechanism for coordinating the formation of stable kinetochore-microtubule attachment and SAC activity.
为了实现染色体的忠实分离，稳定的动粒-微管附着的形成及其通过纺锤体组装检查点（SAC）的监测，是由目前尚未明确的机制协调调节的。在这里，我们发现，在形成稳定的动粒-微管附着中起重要作用的极激酶 1（Plk1），通过与 Bub1 结合，而不是与 CLASP2 或 CLIP-170 结合，也参与 SAC 活性的维持。发现 Plk1 对 SAC 的影响是通过对 SAC 的必需激酶 Mps1 的磷酸化以及对 Knl1 的 MELT 重复序列的磷酸化来介导的。Bub1 作为一个平台，用于将其他 SAC 组件组装到磷酸化的 MELT 重复序列上。我们提出，Bub1 结合的 Plk1 对于维持 SAC 活性很重要，它支持 Bub1 在有丝分裂前期向动粒的定位，此时动粒 Mps1 水平降低，直到稳定的动粒-微管附着的形成完成。我们的研究揭示了协调稳定的动粒-微管附着和 SAC 活性形成的复杂机制。
