Institute of Technology, University of Tartu, Tartu 50411, Estonia.
Mol Cell. 2011 Jun 10;42(5):610-23. doi: 10.1016/j.molcel.2011.05.016.
Cdk specificity is determined by the intrinsic selectivity of the active site and by substrate docking sites on the cyclin subunit. There is a long-standing debate about the relative importance of these factors in the timing of Cdk1 substrate phosphorylation. We analyzed major budding yeast cyclins (the G1/S-cyclin Cln2, S-cyclin Clb5, G2/M-cyclin Clb3, and M-cyclin Clb2) and found that the activity of Cdk1 toward the consensus motif increased gradually in the sequence Cln2-Clb5-Clb3-Clb2, in parallel with cell cycle progression. Further, we identified a docking element that compensates for the weak intrinsic specificity of Cln2 toward G1-specific targets. In addition, Cln2-Cdk1 showed distinct consensus site specificity, suggesting that cyclins do not merely activate Cdk1 but also modulate its active-site specificity. Finally, we identified several Cln2-, Clb3-, and Clb2-specific Cdk1 targets. We propose that robust timing and ordering of cell cycle events depend on gradual changes in the substrate specificity of Cdk1.
Cdk 的特异性取决于其活性位点的固有选择性以及细胞周期蛋白亚基上的底物结合位点。长期以来，人们一直争论这些因素在 Cdk1 底物磷酸化的时间控制中的相对重要性。我们分析了主要的酵母细胞周期蛋白（G1/S 期细胞周期蛋白 Cln2、S 期细胞周期蛋白 Clb5、G2/M 期细胞周期蛋白 Clb3 和 M 期细胞周期蛋白 Clb2），发现 Cdk1 对共识基序的活性在 Cln2-Clb5-Clb3-Clb2 序列中逐渐增加，与细胞周期进程平行。此外，我们确定了一个对接元件，该元件补偿了 Cln2 对 G1 特异性靶标较弱的固有特异性。此外，Cln2-Cdk1 表现出明显的共识基序特异性，这表明细胞周期蛋白不仅激活 Cdk1，还调节其活性位点特异性。最后，我们确定了几个 Cln2、Clb3 和 Clb2 特异性的 Cdk1 靶标。我们提出，细胞周期事件的稳健定时和有序性取决于 Cdk1 底物特异性的逐渐变化。
