Centrosomal proteins in the regulation of spindle bipolarity and ciliogenesis

纺锤体两极的建立是染色体正确分离和有丝分裂进程的关键。哺乳动物Polo-like kinase1(Plk1)被认为在这一过程中发挥核心作用。然而，Plk1如何参与这一事件仍不清楚。在这里，我们证明了在两个不同的位点上，γ-Turc招募蛋白Nedd1/GCP-WD上依赖于Cdc2的磷酸化提供了时间和空间线索，通过依赖磷酸化的与Plk1的Polo-box结构域的相互作用，及时地将Plk1的功能带入中心体和纺锤体。在中心体，Plk1与Nedd1的C末端磷酸化基序相互作用，使后者磷酸化，这一步骤对基于中心体的微管成核是重要的。紧接着，Plk1还沿着纺锤体与N端磷酸化的Nedd1基序相互作用，并磷酸化Augmin亚基Hice1，以促进基于微管的微管成核。Plk1失去Nedd1介导的Hice1磷酸化导致Augmin与微管的相互作用减弱，伽马微管蛋白募集到纺锤体，最终导致正常的双极纺锤体形成和染色体分离的缺陷。综上所述，这里提供的数据展示了中心体和纺锤体上的两个不同的Plk1-Nedd1相互作用如何被破译为不同的生化和细胞结果，以实现正常的双极纺锤体形成和有丝分裂进程的潜在机制。

Establishment of spindle bipolarity is pivotal for proper chromosome segregation and mitotic progression. Mammalian polo-like kinase 1 (Plk1) has been thought to play a central role in this process. However, how Plk1 contributes to this event remains unknown. Here we demonstrated that Cdc2-dependent phosphorylation on a gamma-TuRC recruitment protein, Nedd1/GCP-WD, at two distinct sites provides both temporal and spatial cues to timely bring about Plk1 functions to the centrosomes and spindles via phosphorylation-dependent interaction with the polo-box domain of Plk1. At centrosomes, Plk1 interacted with a C-terminal phosphorylated motif of Nedd1 to phosphorylate the latter, a step suggested to be important for centrosome-based microtubule nucleation. Immediately following this event, Plk1 also interacted with an N-terminal phosphorylated motif of Nedd1 along the spindles and phosphorylated an Augmin subunit, Hice1, to promote microtubule-based microtubule nucleation. Loss of Nedd1-mediated Hice1 phosphorylation by Plk1 resulted in impaired Augmin interaction with microtubules and diminished gamma-tubulin recruitment to the spindles that ultimately led to defects in proper bipolar spindle formation and chromosome segregation. Taken together, the data provided here demonstrate the underlying mechanisms of how the two distinct Plk1-Nedd1 interactions at the centrosomes and spindles are deciphered into different biochemical and cellular outcomes to achieve normal bipolar spindle formation and mitotic progression.