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需的细胞骨架机制：细胞质分裂和纺锤体解体。该提议建立在三个系列的新发现之上。首先，在出芽酵母中，我们发现了Polo激酶（Cdc5）控制细胞分裂的机制。在有丝分裂后期，Cdc5/Polo将小g蛋白Rho1（人RhoA）的鸟嘌呤核苷酸交换因子（GEFs）靶向到分裂位点。gef反过来招募小g蛋白Rho1。Rho1的靶向和激活对于在所有真核生物中收缩肌动蛋白环（CAR）组装所需的肌动蛋白成核体形成蛋白的招募至关重要。类似的机制最近被证明可以解释人类polo样激酶在人类细胞中CAR组装中的作用。其次，我们有未发表的证据表明酵母双胍蛋白Bni1受一种涉及调节蛋白水解的新机制的调节。第三，我们已经定义了主轴拆卸的关键调节器的生化特性。Kip3是Kinesin 8蛋白家族的一员，既是一种正端定向MT马达，也是一种正端特异性MT解聚合酶。我们定义了调节Kip3解聚合酶活性的新机制，这可能是控制有丝分裂后期纺锤体动力学的核心。我们现在提出了以下实验：(1)确定Rho1靶向分裂位点的机制和有丝分裂退出过程中控制Rho1全局激活的机制；(2)明确调控双胍降解的机制和生物学作用；(3)描述新的Kip3/Kinesin 8调控机制，并确定其在纺锤体拆卸和微管动力学中的作用。这项研究与癌症生物学有关，因为已知细胞分裂失败会促进肿瘤的发生。公共卫生相关性：该提案将定义介导有丝分裂退出所需的细胞骨架变化的机制：细胞质分裂和有丝分裂纺锤体的解体。该结果将与癌症生物学相关，因为已知异常的细胞分裂会促进肿瘤的发生。

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 Second, we have unpublished evidence that the yeast formin Bni1 is regulated by a novel mechanism involving regulated proteolysis.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.