ABSTRACT

RepoMan is a chromosome-associated scaffold protein that integrates signaling of multiple kinases and phosphatases to coordinate spindle-kinetochore interactions, chromosome (de)condensation and nuclear envelope (dis)assembly during mitosis. Another key mitotic event is the assembly of a microtubule-based spindle, which involves redundant pathways emanating from the centrosomes, microtubules and chromosomes. Here we describe a novel mitotic function of RepoMan in regulating chromosome-dependent microtubule assembly. At limiting concentrations of microtubule-destabilizing agents, RepoMan-depleted cells showed enhanced chromosome clustering. This clustering was completely dependent on the partial inhibition of microtubule growth originating from the chromosome-dependent pathway. We also demonstrated that RepoMan interacts with prime regulators of the chromosome-dependent spindle assembly such as NuSAP1, NuMA, and TPX2. In addition, RepoMan was required to enable or maintain phosphorylation of NuSAP1 at CDK sites, thereby enabling activation of NuSAP1 through dissociation of inhibitory importin β/7. Our data identify RepoMan as an enhancer of microtubule assembly at chromosomes.

摘要

RepoMan 是一种染色体相关支架蛋白，可整合多种激酶和磷酸酶的信号传导，以协调有丝分裂过程中纺锤体-着丝粒相互作用、染色体（解）缩合和核膜（解）组装。另一个关键的有丝分裂事件是基于微管的纺锤体的组装，其中涉及从中心体、微管和染色体发出的冗余途径。在这里，我们描述了 RepoMan 在调节染色体依赖性微管组装中的一种新的有丝分裂功能。在微管不稳定剂的限制浓度下，RepoMan 耗尽的细胞显示出增强的染色体聚类。这种聚类完全依赖于对源自染色体依赖性途径的微管生长的部分抑制。我们还证明了 RepoMan 与染色体依赖性纺锤体组装的主要调节因子（例如 NuSAP1、NuMA 和 TPX2）相互作用。此外，RepoMan 需要启用或维持 NuSAP1 在 CDK 位点的磷酸化，从而通过抑制性输入蛋白 β/7 的解离来激活 NuSAP1。我们的数据表明 RepoMan 是染色体微管组装的增强剂。