Department of Biochemistry and Molecular Biology, Graduate School and Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Biol Chem. 2012 Feb 24;287(9):6275-83. doi: 10.1074/jbc.M111.318295. Epub 2012 Jan 5.
In mammalian cells Cdk2 activity during the G(1)-S transition is mainly controlled by p27(KIP1). Although the amount and subcellular localization of p27 influence Cdk2 activity, how Cdk2 activity is regulated during this phase transition still remains virtually unknown. Here we report an entirely new mechanism for this regulation. Cdc6 the AAA+ ATPase, known to assemble prereplicative complexes on chromosomal replication origins and activate p21(CIP1)-bound Cdk2, also activated p27-bound Cdk2 in its ATPase and cyclin binding motif-dependent manner but only after the p27 bound to the Cdk2 was phosphorylated at the C terminus. ROCK, which mediates a signal for cell anchorage to the extracellular matrix and activates the mTORC1 cascade as well as controls cytoskeleton assembly, was partly responsible for C-terminal phosphorylation of the p27. In vitro reconstitution demonstrated ROCK (Rho-associated kinase)-mediated phosphorylation of Cdk2-bound p27 at the C terminus and subsequent activation of the Cdk2 by Cdc6.
在哺乳动物细胞中，G1-S 期转换过程中的 Cdk2 活性主要受 p27(KIP1)控制。尽管 p27 的数量和亚细胞定位会影响 Cdk2 活性，但在这个相变过程中 Cdk2 活性是如何被调节的仍然知之甚少。在这里，我们报道了一个全新的调控机制。Cdc6 是一种 AAA+ATP 酶，已知它在染色体复制起点组装前复制复合物，并激活 p21(CIP1)结合的 Cdk2，但只有在 p27 结合到 Cdk2 后，其 C 端被磷酸化时，Cdc6 才能以其 ATP 酶和细胞周期蛋白结合基序依赖的方式激活 p27 结合的 Cdk2。ROCK（Rho 相关蛋白激酶）介导细胞与细胞外基质的锚定信号，并激活 mTORC1 级联反应以及控制细胞骨架组装，部分负责 p27 的 C 端磷酸化。体外重建实验表明，ROCK 介导 Cdk2 结合的 p27 在 C 端磷酸化，随后 Cdc6 激活 Cdk2。
