Kang Jungseog, Chen Yue, Zhao Yingming, Yu Hongtao
Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9041, USA.
Proc Natl Acad Sci U S A. 2007 Dec 18;104(51):20232-7. doi: 10.1073/pnas.0710519105. Epub 2007 Dec 14.
The spindle checkpoint ensures the accuracy of chromosome segregation during mitosis. The protein serine/threonine kinase, Mps1, is a critical component of the spindle checkpoint in human cells and regulates the kinetochore localization of key checkpoint proteins. The kinase activity of Mps1 is required for the spindle checkpoint, but how Mps1 is activated during mitosis is unclear. Here, we show that the endogenous Mps1 in mitotic HeLa cells is phosphorylated on T676, a residue in the activation loop. This phosphorylation event on Mps1 is required for its kinase activity in vitro and for spindle checkpoint signaling in vivo. T676 phosphorylation of Mps1 increases during mitosis and can occur through intermolecular/trans autophosphorylation. Induced dimerization of Mps1 is sufficient to activate its kinase activity in cells. We speculate that the kinetochore localization of Mps1 raises its local concentration, leading to its activation during mitosis through more efficient trans autophosphorylation.
纺锤体检查点确保有丝分裂期间染色体分离的准确性。蛋白丝氨酸/苏氨酸激酶Mps1是人类细胞中纺锤体检查点的关键组成部分,并调节关键检查点蛋白在动粒上的定位。纺锤体检查点需要Mps1的激酶活性,但Mps1在有丝分裂期间如何被激活尚不清楚。在这里,我们表明有丝分裂期HeLa细胞中的内源性Mps1在T676(激活环中的一个残基)处被磷酸化。Mps1上的这一磷酸化事件在体外对其激酶活性以及在体内对纺锤体检查点信号传导都是必需的。Mps1的T676磷酸化在有丝分裂期间增加,并且可以通过分子间/反式自磷酸化发生。诱导Mps1二聚化足以在细胞中激活其激酶活性。我们推测Mps1在动粒上的定位提高了其局部浓度,导致其在有丝分裂期间通过更有效的反式自磷酸化而被激活。