Qi Wei, Tang Zhanyun, Yu Hongtao
Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA.
Mol Biol Cell. 2006 Aug;17(8):3705-16. doi: 10.1091/mbc.e06-03-0240. Epub 2006 Jun 7.
Polo-like kinase 1 (Plk1) is required for the generation of the tension-sensing 3F3/2 kinetochore epitope and facilitates kinetochore localization of Mad2 and other spindle checkpoint proteins. Here, we investigate the mechanism by which Plk1 itself is recruited to kinetochores. We show that Plk1 binds to budding uninhibited by benzimidazole 1 (Bub1) in mitotic human cells. The Plk1-Bub1 interaction requires the polo-box domain (PBD) of Plk1 and is enhanced by cyclin-dependent kinase 1 (Cdk1)-mediated phosphorylation of Bub1 at T609. The PBD-dependent binding of Plk1 to Bub1 facilitates phosphorylation of Bub1 by Plk1 in vitro. Depletion of Bub1 in HeLa cells by RNA interference (RNAi) diminishes the kinetochore localization of Plk1. Ectopic expression of the wild-type Bub1, but not the Bub1-T609A mutant, in Bub1-RNAi cells restores the kinetochore localization of Plk1. Our results suggest that phosphorylation of Bub1 at T609 by Cdk1 creates a docking site for the PBD of Plk1 and facilitates the kinetochore recruitment of Plk1.
Polo样激酶1（Plk1）是产生张力感应性3F3/2动粒表位所必需的，并促进Mad2和其他纺锤体检查点蛋白在动粒上的定位。在此，我们研究Plk1自身被招募到动粒的机制。我们发现在有丝分裂的人类细胞中，Plk1与苯并咪唑1未抑制的出芽蛋白（Bub1）结合。Plk1与Bub1的相互作用需要Plk1的polo框结构域（PBD），并且在T609位点由细胞周期蛋白依赖性激酶1（Cdk1）介导的Bub1磷酸化可增强这种相互作用。Plk1与Bub1的PBD依赖性结合在体外促进了Plk1对Bub1的磷酸化。通过RNA干扰（RNAi）使HeLa细胞中的Bub1缺失会减少Plk1在动粒上的定位。在Bub1-RNAi细胞中异位表达野生型Bub1，而不是Bub1-T609A突变体，可恢复Plk1在动粒上的定位。我们的结果表明，Cdk1在T609位点对Bub1的磷酸化产生了一个用于Plk1的PBD的对接位点，并促进了Plk1向动粒的募集。
