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Mechanism of mitotic exit in budding yeast

芽殖酵母有丝分裂退出机制

基本信息

批准号：
7886112
负责人：
RAYMOND J DESHAIES
金额：
$ 9.02万
依托单位：
CALIFORNIA INSTITUTE OF TECHNOLOGY
依托单位国家：
美国
项目类别：
财政年份：
2009
资助国家：
美国
起止时间：
2009-07-20 至 2010-03-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): All eukaryotic cells must exit mitosis to divide. Exit from mitosis is achieved by inactivation of the same mitotic cyclin/cyclin-dependent kinase (CDK) enzyme that drives cells into mitosis. Mitotic cyclin/CDK is down-regulated at the end of mitosis by two different mechanisms in budding yeast: induction of the CDK inhibitor Sic1 by Swi5 and the turnover of mitotic cyclin promoted by Hctl (aka Cdhl) and the anaphasepromoting complex-cyclosome (APC) ubiquitin ligase. Early in mitosis, mitotic cyclin/CDK keeps its antagonists at bay by attaching inhibitory phosphates on Swi5 and Hctl. During anaphase-telophase, the protein phosphatase Cdc14 enables the exit from mitosis by reversing these inhibitory phosphorylations. A watershed event in the exit from mitosis is the activation of Cdc14, which is achieved by its release from the nucleolar anchor protein Net1. Thus, a key to understanding how cells exit mitosis is to understand how Cdc14 is mobilized from the nucleolus at the end of mitosis. This mobilization involves two signaling pathways: the Cdc Fourteen Early Anaphase Release (FEAR) network and the Mitotic Exit Network (MEN). The FEAR network instigates the transient release of Cdc14 from the nucleolus during early anaphase, whereas the MEN somehow transforms this brief nuclear furlough into a more sustained dispersal of Cdc14 throughout the cell that is able to drive exit from mitosis. The goal of the 3 specific aims described in this application is to understand how the FEAR network and the MEN bring about the activation of Cdc14. In the first aim we will seek to determine how the FEAR network and phosphorylation of Net1 by mitotic cyclin/CDK collaborate to bring about FEAR. In the second aim we will address the hypothesis that a key function of the MEN is to alter the nucleocytoplasmic distribution of Cdc14 released from the nucleolus through the action of the FEAR network. In the third aim, we will seek proteins that serve as substrates of the MEN component Dbf2 to understand how this protein kinase brings about sustained dispersal of Cdc14 throughout the cell. Given the conservation of the FEAR network and MEN proteins, the work described here has excellent potential to shed insight into the growth and division of normal and cancerous human cells, and thereby highlight new candidate targets for anti-cancer drugs. Our work may also provide a useful paradigm for understanding how other pathways that employ reversible nucleolar sequestra - such as the ARF-Mdm2- p53 circuit - are regulated.

描述（由申请人提供）：所有真核细胞必须退出有丝分裂才能分裂。退出有丝分裂是通过灭活驱动细胞进入有丝分裂的相同的有丝分裂细胞周期蛋白/细胞周期蛋白依赖性激酶（CDK）酶来实现的。在芽殖酵母中，有丝分裂周期蛋白/CDK在有丝分裂结束时通过两种不同的机制下调：Swi 5诱导CDK抑制剂Sic 1和Hctl（aka Cdhl）和后期促进复合体-环体（APC）泛素连接酶促进有丝分裂周期蛋白的周转。在有丝分裂早期，有丝分裂细胞周期蛋白/CDK通过在Swi 5和Hctl上附着抑制性磷酸盐来阻止其拮抗剂。在后期-末期，蛋白磷酸酶Cdc 14能够通过逆转这些抑制性磷酸化而退出有丝分裂。退出有丝分裂的分水岭事件是Cdc 14的激活，这是通过其从核仁锚蛋白Net 1释放来实现的。因此，了解细胞如何退出有丝分裂的关键是了解Cdc 14如何在有丝分裂结束时从核仁中动员出来。这种动员涉及两个信号通路：Cdc 14早期后期释放（FEAR）网络和有丝分裂退出网络（MEN）。FEAR网络在后期早期从核仁中瞬时释放Cdc 14，而MEN以某种方式将这种短暂的核休假转化为Cdc 14在整个细胞中更持续的分散，从而能够驱动有丝分裂。本申请中描述的3个具体目标的目的是了解FEAR网络和MEN如何激活Cdc 14。在第一个目标中，我们将试图确定FEAR网络和Net 1的有丝分裂细胞周期蛋白/CDK磷酸化如何合作，以实现FEAR。在第二个目标中，我们将解决的假设，MEN的一个关键功能是改变Cdc 14的核质分布从核仁释放通过行动的恐惧网络。在第三个目标中，我们将寻找作为MEN组分Dbf 2底物的蛋白质，以了解这种蛋白激酶如何使Cdc 14在整个细胞中持续分散。鉴于FEAR网络和MEN蛋白的保守性，本文所述的工作具有很好的潜力，可以深入了解正常和癌性人类细胞的生长和分裂，从而突出抗癌药物的新候选靶点。我们的工作也可能提供一个有用的范例，了解其他途径，采用可逆的核仁螯合物-如ARF-Mdm 2- p53电路-是如何调节。