State Key Laboratory of Molecular Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
Key Laboratory of Molecular and Cellular Systems Biology, Tianjin Normal University, Tianjin, China.
J Mol Cell Biol. 2018 Aug 1;10(4):358-370. doi: 10.1093/jmcb/mjy033.
The chromokinesin Kif4A controls proper chromosome condensation, congression/alignment, and cytokinesis to ensure faithful genetic inheritance. Here, we report that Cdk phosphorylation of human Kif4A at T1161 licenses Kif4A chromosomal localization, which, in turn, controls Kif4A early mitotic function. Phosphorylated Kif4A (Kif4AWT) or Cdk phospho-mimetic Kif4A mutant (Kif4ATE) associated with chromosomes and condensin I (non-SMC subunit CAP-G and core subunit SMC2) to regulate chromosome condensation, spindle morphology, and chromosome congression/alignment in early mitosis. In contrast, Cdk non-phosphorylatable Kif4A mutant (Kif4ATA) could neither localize on chromosomes nor associate with CAP-G and SMC2. Furthermore, Kif4ATA could not rescue defective chromosome condensation, spindle morphology, or chromosome congression/alignment in cells depleted of endogenous Kif4A, which activated a mitotic checkpoint and delayed early mitotic progression. However, targeting Kif4ATA to chromosomes by fusion of Kif4ATA with Histone H1 resulted in restoration of chromosome and spindle functions of Kif4A, similar to Kif4AWT and Kif4ATE, in cells depleted of endogenous Kif4A. Thus, our results demonstrate that Cdk phosphorylation-licensed chromosomal localization of Kif4A plays a critical role in regulating early mitotic functions of Kif4A that are important for early mitotic progression.
动力蛋白 Kif4A 通过控制染色体的恰当凝聚、聚集/排列和胞质分裂，来确保遗传物质的准确传递。在这里，我们报道了 Cdk 对人源 Kif4A 的 T1161 位苏氨酸进行磷酸化修饰，从而赋予 Kif4A 染色体定位的能力，而后者反过来又控制着 Kif4A 的有丝分裂早期功能。磷酸化的 Kif4A（Kif4AWT）或 Cdk 磷酸模拟突变体 Kif4A（Kif4ATE）与染色体和凝聚素 I（非 SMC 亚基 CAP-G 和核心亚基 SMC2）结合，从而调控染色体的凝聚、纺锤体形态和有丝分裂早期的染色体聚集/排列。相比之下，Cdk 非磷酸化的 Kif4A 突变体（Kif4ATA）既不能定位于染色体上，也不能与 CAP-G 和 SMC2 结合。此外，Kif4ATA 既不能拯救内源性 Kif4A 缺失导致的染色体凝聚、纺锤体形态或染色体聚集/排列缺陷，也不能激活有丝分裂检查点并延迟有丝分裂早期进程。然而，通过将 Kif4ATA 与组蛋白 H1 融合，将 Kif4ATA 靶向染色体，可恢复内源性 Kif4A 缺失细胞中 Kif4A 的染色体和纺锤体功能，其效果与 Kif4AWT 和 Kif4ATE 相似。因此，我们的研究结果表明，Cdk 磷酸化赋予 Kif4A 的染色体定位在调节 Kif4A 的有丝分裂早期功能方面发挥着关键作用，而这些功能对于有丝分裂早期进程至关重要。
