Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
Elife. 2020 Sep 1;9:e59885. doi: 10.7554/eLife.59885.
APC/C-mediated proteolysis of cyclin B and securin promotes anaphase entry, inactivating CDK1 and permitting chromosome segregation, respectively. Reduction of CDK1 activity relieves inhibition of the CDK1-counteracting phosphatases PP1 and PP2A-B55, allowing wide-spread dephosphorylation of substrates. Meanwhile, continued APC/C activity promotes proteolysis of other mitotic regulators. Together, these activities orchestrate a complex series of events during mitotic exit. However, the relative importance of regulated proteolysis and dephosphorylation in dictating the order and timing of these events remains unclear. Using high temporal-resolution proteomics, we compare the relative extent of proteolysis and protein dephosphorylation. This reveals highly-selective rapid proteolysis of cyclin B, securin and geminin at the metaphase-anaphase transition, followed by slow proteolysis of other substrates. Dephosphorylation requires APC/C-dependent destruction of cyclin B and was resolved into PP1-dependent categories with unique sequence motifs. We conclude that dephosphorylation initiated by selective proteolysis of cyclin B drives the bulk of changes observed during mitotic exit.
APC/C 介导的细胞周期蛋白 B 和 securin 的蛋白水解促进了有丝分裂后期的进入，分别使 CDK1 失活并允许染色体分离。降低 CDK1 活性解除了 CDK1 拮抗磷酸酶 PP1 和 PP2A-B55 的抑制，允许广泛去磷酸化底物。同时，持续的 APC/C 活性促进其他有丝分裂调节剂的蛋白水解。这些活动共同协调了有丝分裂退出过程中的一系列复杂事件。然而，调控蛋白水解和去磷酸化在决定这些事件的顺序和时间方面的相对重要性尚不清楚。使用高时间分辨率蛋白质组学，我们比较了蛋白水解和蛋白去磷酸化的相对程度。这表明在中期-后期过渡时，细胞周期蛋白 B、securin 和 geminin 发生高度选择性的快速蛋白水解，随后是其他底物的缓慢蛋白水解。去磷酸化需要 APC/C 依赖性的细胞周期蛋白 B 破坏，并分为具有独特序列模体的 PP1 依赖性类别。我们得出结论，细胞周期蛋白 B 的选择性蛋白水解引发的去磷酸化驱动了有丝分裂退出过程中观察到的大部分变化。
