Abe Yasuhito, Takeuchi Takashi, Kagawa-Miki Lisa, Ueda Norifumi, Shigemoto Kazuhiro, Yasukawa Masaki, Kito Katsumi
Department of Molecular Pathology, Ehime University Postgraduate School of Medicine, Toh-on, Ehime 791-0295, Japan.
J Mol Biol. 2007 Jul 6;370(2):231-45. doi: 10.1016/j.jmb.2007.04.067. Epub 2007 May 3.
A MAPKK-like mitotic kinase, TOPK, implies the formation of mitotic spindles and spindle midzone and accomplishing cytokinesis, however, its underlying mechanism remains unclear. A microtubule bundling protein, PRC1, plays a pivotal role in the formation of mitotic spindles and spindle midzone. Because of their functional resemblance, we attempted to clarify the links between these two molecules. TOPK supported mitotic advance via the cdk1/cyclin B1-dependent phosphorylation of PRC1. TOPK induced the phosphorylation of PRC1 at T481 in vivo, however, TOPK did not phosphorylate PRC1 in vitro. TOPK induced the phosphorylation of PRC1 at T481 only when the cdk1/cyclin B1 existed simultaneously in vitro. Both the enzymatic activity of TOPK and association competence of TOPK with PRC1 were mandatory for this phosphorylation. TOPK binds to cdk1/cyclin B1, microtubules and PRC1 via its unique region near the C terminus. TOPK co-localized closely with cdk1 throughout the cell cycle in vivo. Collectively, these data indicate that TOPK, which makes a kinase-substrate complex with cdk1/cyclin B1 and PRC1 on microtubules during mitosis, enhances the cdk1/cyclin B1-dependent phosphorylation of PRC1 and thereby strongly promotes cytokinesis.
一种类丝裂原活化蛋白激酶激酶（MAPKK）的有丝分裂激酶TOPK，参与有丝分裂纺锤体和纺锤体中间区的形成以及胞质分裂的完成，然而，其潜在机制仍不清楚。一种微管成束蛋白PRC1，在有丝分裂纺锤体和纺锤体中间区的形成中起关键作用。由于它们在功能上的相似性，我们试图阐明这两种分子之间的联系。TOPK通过对PRC1的cdk1/细胞周期蛋白B1依赖性磷酸化来支持有丝分裂进程。TOPK在体内诱导PRC1的T481位点磷酸化，然而，TOPK在体外不能使PRC1磷酸化。只有当cdk1/细胞周期蛋白B1同时存在于体外时，TOPK才能诱导PRC1的T481位点磷酸化。TOPK的酶活性和TOPK与PRC1的结合能力对于这种磷酸化都是必需的。TOPK通过其靠近C端的独特区域与cdk1/细胞周期蛋白B1、微管和PRC1结合。在体内，TOPK在整个细胞周期中都与cdk1紧密共定位。总的来说，这些数据表明，在有丝分裂期间，TOPK在微管上与cdk1/细胞周期蛋白B1和PRC1形成激酶-底物复合物，增强了cdk1/细胞周期蛋白B1依赖性的PRC1磷酸化，从而有力地促进了胞质分裂。
