Cell Cycle Control of the Cytoskeleton

描述(由申请人提供)：本提案侧重于正常有丝分裂退出所必需的细胞骨架机制：胞质分裂和纺锤体分解。该提案建立在三个系列新奇发现的基础上。首先，在萌芽酵母中，我们发现了Polo激酶(CDC5)控制胞质分裂的机制。在有丝分裂晚期，CDC5/Polo将小G蛋白Rho1(人RhoA)的鸟核苷酸交换因子(GEF)靶向分裂位点。GEF反过来招募小G蛋白Rho1。Rho1的靶向和激活对于所有真核生物中装配收缩肌动蛋白环(CAR)所需的肌动蛋白核因子福尔马林的募集是必不可少的。最近，类似的机制也被用来解释人类Polo-like激酶在人类细胞CAR组装中的作用。其次，我们有未发表的证据表明，酵母Forin Bni1受到一种新的机制的调控，涉及到受调控的蛋白分解。第三，我们定义了纺锤体拆卸的关键调节因子的生化特性。Kip3是激动素8家族中的一员，既是正端导向的MT马达，又是正端特异性的MT解聚酶。我们定义了调节Kip3解聚酶活性的新机制，这可能是在有丝分裂后期控制纺锤体动力学的中心。我们现在建议进行以下实验：(1)确定Rho1靶向分裂位点的机制以及在有丝分裂退出时控制全局Rho1激活的机制；(2)定义受调控的Forin降解的机制和生物学作用；(3)表征新的Kip3/Kinesin 8调控机制，并确定它们在纺锤体拆解和微管动力学中的作用。这项拟议的研究与癌症生物学有关，因为细胞质分裂失败已知会促进肿瘤的发生。与公共卫生相关：该提案将定义调节有丝分裂退出所必需的细胞骨架变化的机制：有丝分裂纺锤体的胞质分裂和拆解。这一结果将与癌症生物学相关，因为已知异常胞质分裂促进肿瘤发生。

DESCRIPTION (provided by applicant): This proposal focuses on cytoskeletal mechanisms necessary for normal mitotic exit: cytokinesis and spindle disassembly. The proposal builds on three series of novel findings. First, in budding yeast we discovered a mechanism by which the Polo kinase (Cdc5) controls cytokinesis. In late mitosis, Cdc5/Polo targets guanine nucleotide exchange factors (GEFs) for the small G-protein Rho1 (human RhoA) to the division site. The GEFs, in turn, recruit the small G-protein Rho1. Rho1 targeting and activation are essential for the recruitment of formins, actin nucleators required for contractile actin ring (CAR) assembly in all eukaryotes. Similar mechanisms were recently shown to explain the role of human Polo-like kinase in CAR assembly in human cells. Second, we have unpublished evidence that the yeast formin Bni1 is regulated by a novel mechanism involving regulated proteolysis. Third, we have defined the biochemical properties of a key regulator of spindle disassembly. Kip3, a member of the Kinesin 8 family of proteins, is both a plus end directed MT motor and a plus end-specific MT depolymerase. We defined new mechanisms regulating the Kip3 depolymerase activity which may be central to controlling spindle dynamics during late mitosis. We now propose experiments to (1) define the mechanism of Rho1 targeting to the division site and the mechanism controlling global Rho1 activation during mitotic exit; (2) Define the mechanisms and biological role of regulated formin degradation; (3) Characterize novel Kip3/Kinesin 8 regulatory mechanisms and define their role in spindle disassembly and microtubule dynamics. The proposed research is relevant to cancer biology because cytokinesis failure is known to promote tumorigenesis. PUBLIC HEALTH RELEVANCE: This proposal will define mechanisms that mediate changes in the cytoskeleton necessary for mitotic exit: cytokinesis and disassembly of the mitotic spindle. The results will be relevant to cancer biology because abnormal cytokinesis is known to promote tumorigenesis.