Liu Sikai, Yuan Xiao, Gui Ping, Liu Ran, Durojaye Olanrewaju, Hill Donald L, Fu Chuanhai, Yao Xuebiao, Dou Zhen, Liu Xing
MOE Key Laboratory for Cellular Dynamics and The First Affiliated Hospital, School of Life Sciences, University of Science and Technology of China, Hefei, China.
CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China.
EMBO Rep. 2022 Jun 7;23(6):e54171. doi: 10.15252/embr.202154171. Epub 2022 Apr 5.
Accurate mitotic progression relies on the dynamic phosphorylation of multiple substrates by key mitotic kinases. Cyclin-dependent kinase 1 is a master kinase that coordinates mitotic progression and requires its regulatory subunit Cyclin B to ensure full kinase activity and substrate specificity. The function of Cyclin B2, which is a closely related family member of Cyclin B1, remains largely elusive. Here, we show that Mad2 promotes the kinetochore localization of Cyclin B2 and that their interaction at the kinetochores guides accurate chromosome segregation. Our biochemical analyses have characterized the Mad2-Cyclin B2 interaction and delineated a novel Mad2-interacting motif (MIM) on Cyclin B2. The functional importance of the Cyclin B2-Mad2 interaction was demonstrated by real-time imaging in which MIM-deficient mutant Cyclin B2 failed to rescue the chromosomal segregation defects. Taken together, we have delineated a previously undefined function of Cyclin B2 at the kinetochore and have established, in human cells, a mechanism of action by which Mad2 contributes to the spindle checkpoint.
精确的有丝分裂进程依赖于关键有丝分裂激酶对多种底物的动态磷酸化作用。细胞周期蛋白依赖性激酶1是一种主导激酶，它协调有丝分裂进程，并需要其调节亚基细胞周期蛋白B来确保充分的激酶活性和底物特异性。细胞周期蛋白B2是细胞周期蛋白B1的密切相关家族成员，其功能在很大程度上仍不清楚。在这里，我们表明Mad2促进细胞周期蛋白B2在动粒的定位，并且它们在动粒处的相互作用指导精确的染色体分离。我们的生化分析已经表征了Mad2与细胞周期蛋白B2的相互作用，并在细胞周期蛋白B2上描绘了一个新的Mad2相互作用基序（MIM）。通过实时成像证明了细胞周期蛋白B2-Mad2相互作用的功能重要性，其中MIM缺陷型突变体细胞周期蛋白B2未能挽救染色体分离缺陷。综上所述，我们已经描绘了细胞周期蛋白B2在动粒上以前未定义的功能，并在人类细胞中建立了Mad2促进纺锤体检查点的作用机制。
