Cmentowski Verena, Musacchio Andrea
Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund 44227, Germany.
Centre for Medical Biotechnology, Faculty of Biology, University of Duisburg-Essen, Essen 45141, Germany.
Sci Adv. 2025 Sep 12;11(37):eady6890. doi: 10.1126/sciadv.ady6890.
The kinetochore corona, a polymeric fibrous structure, facilitates chromosome biorientation and mitotic checkpoint signaling during mitosis. How its main building block, the ROD-Zwilch-ZW10 (RZZ) complex, assembles on the outer kinetochore remains poorly understood. Harnessing corona biochemical reconstitutions and cell biology, we reveal that the paralogous spindle assembly checkpoint (SAC) proteins BUB1 and BUBR1 promote nonredundant branches of corona assembly. MPS1 kinase-dependent kinetochore docking of BUB1 and subsequent recruitment of BUBR1 initiates assembly. Disrupting the first branch by depleting CENP-E, a kinesin that links BUBR1 to RZZ, uncovered a second assembly pathway mediated by a direct interaction between BUB1 and ROD. Discovery of a direct interaction with the RZZ explains how the SAC protein MAD1 fits this corona assembly scheme. Our findings solve the long-standing puzzle of corona assembly and demonstrate the intimate interweaving of chromosome biorientation and checkpoint signaling.
动粒冠是一种聚合纤维结构，在有丝分裂过程中促进染色体双定向和有丝分裂检查点信号传导。其主要组成部分，即ROD-Zwilch-ZW10（RZZ）复合体，如何在外动粒上组装仍知之甚少。利用冠生化重建和细胞生物学方法，我们发现同源的纺锤体组装检查点（SAC）蛋白BUB1和BUBR1促进了冠组装的非冗余分支。BUB1的MPS1激酶依赖性动粒对接以及随后BUBR1的招募启动了组装。通过耗尽CENP-E（一种将BUBR1与RZZ连接起来的驱动蛋白）破坏第一条组装途径，发现了由BUB1与ROD之间的直接相互作用介导的第二条组装途径。与RZZ直接相互作用的发现解释了SAC蛋白MAD1如何适应这种冠组装模式。我们的发现解决了长期存在的冠组装难题，并证明了染色体双定向和检查点信号传导的紧密交织。
