Heinzle Christian, Höfler Anna, Yu Jun, Heid Peter, Kremer Nora, Schunk Rebecca, Stengel Florian, Bange Tanja, Boland Andreas, Mayer Thomas U
Department of Biology, University of Konstanz, Konstanz, Germany.
Konstanz Research School Chemical Biology, University of Konstanz, Konstanz, Germany.
Nat Commun. 2025 Jan 20;16(1):853. doi: 10.1038/s41467-024-55669-x.
Phosphorylation of substrates by cyclin-dependent kinases (CDKs) is the driving force of cell cycle progression. Several CDK-activating cyclins are involved, yet how they contribute to substrate specificity is still poorly understood. Here, we discover that a positively charged pocket in cyclin B1, which is exclusively conserved within B-type cyclins and binds phosphorylated serine- or threonine-residues, is essential for correct execution of mitosis. HeLa cells expressing pocket mutant cyclin B1 are strongly delayed in anaphase onset due to multiple defects in mitotic spindle function and timely activation of the E3 ligase APC/C. Pocket integrity is essential for APC/C phosphorylation particularly at non-consensus CDK1 sites and full in vitro ubiquitylation activity. Our results support a model in which cyclin B1's pocket facilitates sequential substrate phosphorylations involving initial priming events that assist subsequent pocket-dependent phosphorylations even at non-consensus CDK1 motifs.
细胞周期蛋白依赖性激酶（CDK）对底物的磷酸化作用是细胞周期进程的驱动力。虽然有几种CDK激活型细胞周期蛋白参与其中，但它们如何决定底物特异性仍知之甚少。在此，我们发现细胞周期蛋白B1中的一个带正电荷的口袋结构，该结构仅在B型细胞周期蛋白中保守，并能结合磷酸化的丝氨酸或苏氨酸残基，对有丝分裂的正确执行至关重要。表达口袋突变型细胞周期蛋白B1的HeLa细胞在后期起始时严重延迟，这是由于有丝分裂纺锤体功能的多个缺陷以及E3连接酶APC/C的及时激活所致。口袋完整性对于APC/C磷酸化至关重要，特别是在非一致性CDK1位点，以及完整的体外泛素化活性。我们的结果支持这样一个模型，即细胞周期蛋白B1的口袋促进了底物的顺序磷酸化，包括初始引发事件，这些事件有助于后续口袋依赖性磷酸化，即使在非一致性CDK1基序处也是如此。
