Department of Pathology, Institute of Systems Biomedicine, School of Basic Medical Sciences, Beijing Key Laboratory of Systems Biology, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, P.R. China.
Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, P.R. China.
Sci Rep. 2017 May 9;7(1):1630. doi: 10.1038/s41598-017-01915-w.
EG5 (KIF11) is a member of the kinesin-like protein family involved in centrosome separation and bipolar spindle formation. When a cell enters mitosis, CDK1 phosphorylates EG5 at Thr926 and promotes EG5 localization on the mitotic spindle which drives bipolar spindle formation. EG5 provides power for spindle movement and thus controls the dynamics of spindle assembly. However, little is known about EG5 regulation or how EG5 detaches from the spindle upon mitotic exit. In this study we identify EG5 as a novel substrate of PP2A phosphatase, and we show that the PP2A/B55α complex plays an important role in mitotic exit by a mechanism involving EG5. The PP2A/B55α complex physically associates with the EG5 C-terminal tail domain and dephosphorylates EG5 at Thr926 that enables mitotic exit. Conversely PP2A knockdown cells show a high level of phospho-EG5 in late metaphase, which is associated with a delay in mitotic exit. These phenotypic features are similar to those induced by EG5/T926D transfection that mimics phosphorylated EG5 status. Our results argue that PP2A controls mitotic exit through EG5 dephosphorylation. Lack of PP2A leads to abnormal EG5 activation, resulting in delay of mitotic exit.
EG5（KIF11）是参与中心体分离和双极纺锤体形成的驱动蛋白样蛋白家族的成员。当细胞进入有丝分裂时，CDK1 将 EG5 在 Thr926 处磷酸化，并促进 EG5 定位到有丝分裂纺锤体上，从而驱动双极纺锤体的形成。EG5 为纺锤体运动提供动力，从而控制纺锤体组装的动力学。然而，EG5 的调节机制或 EG5 如何在有丝分裂退出时从纺锤体上脱离仍知之甚少。在这项研究中，我们确定 EG5 是 PP2A 磷酸酶的一种新型底物，并且我们表明，PP2A/B55α 复合物通过涉及 EG5 的机制在有丝分裂退出中发挥重要作用。PP2A/B55α 复合物与 EG5 C 端尾部结构域物理结合，并使 EG5 在 Thr926 处去磷酸化，从而使有丝分裂退出。相反，PP2A 敲低细胞在后期中期表现出高水平的磷酸化 EG5，这与有丝分裂退出延迟有关。这些表型特征与模拟磷酸化 EG5 状态的 EG5/T926D 转染诱导的特征相似。我们的结果表明，PP2A 通过 EG5 去磷酸化控制有丝分裂退出。缺乏 PP2A 会导致 EG5 异常激活，从而导致有丝分裂退出延迟。
