Regulation of Cytokinesis in Fission Yeast

描述（由申请人提供）：这个项目的长期目标是了解细胞分裂是如何被调节的，细胞分裂是如何与其他有丝分裂事件协调的，如果细胞分裂延迟，细胞是如何延迟细胞周期的进一步进展的。在分裂酵母S. pombe中，一个被称为SIN的保守信号网络在后期结束时触发细胞质分裂的开始。这个网络的适当调节对于协调细胞和核分裂以维持基因组的稳定性至关重要。只有在染色体分离后，SIN才必须被激活，它的活性必须保持到细胞质分裂完成，而细胞质分裂完成后，该途径必须被灭活。在这里提出的研究中，我们将尝试在分子水平上定义SIN调节中的每个步骤是如何完成的。此外，我们将尝试确定SIN在促进细胞分裂中起关键作用的靶标。高细胞周期蛋白依赖性激酶（Cdk）活性在早期有丝分裂抑制过早的SIN激活，直到染色体在后期分离。在Specific Aim 1中，我们将测试这种抑制是否通过Cdk对SIN成分的直接磷酸化起作用，特别是Sid2p、Cdc7p和cdc11p。细胞分裂所需的SIN靶点尚不清楚。我们将在Specific Aim 2中通过使用基于候选的方法来鉴定体内细胞分裂所需的Sid2p底物来解决这个问题。我们已经证明，在细胞质分裂过程中，SIN不仅促进细胞质分裂，而且还抑制间期细胞骨架重排，从而协调细胞质分裂的完成与下一个细胞周期的开始。在Specific Aim 3中，我们将确定SIN抑制间期极性的分子机制，以及这种抑制对细胞分裂成功完成的功能意义。一旦SIN被激活，它的活性保持到细胞质分裂完成，一旦细胞质分裂完成，SIN就失去活性。在specific Aim 4中，我们将研究Etd1p蛋白如何促进SIN信号传导，以及Etd1p的破坏是否是在细胞分裂完成后使SIN失活的信号。几种SIN蛋白的同源物在动物细胞中起肿瘤抑制作用。由于细胞分裂的基本机制在酵母和人类之间高度保守，我们期望对SIN蛋白之间精确分子相互作用的表征将有助于阐明它们的哺乳动物同源物如何抑制肿瘤形成。

DESCRIPTION (provided by applicant): The long term goal of this project is to understand how cytokinesis is regulated, how cytokinesis is coordinated with other mitotic events, and how cells delay further cell cycle progression if cytokinesis is delayed. A conserved signaling network called the SIN in the fission yeast S. pombe functions to trigger initiation of cytokinesis at the end of anaphase. Proper regulation of this network is crucial for coordinating cell and nuclear division to maintain genomic stability. The SIN must be activated only once chromosomes have been segregated, its activity must be maintained until cytokinesis is complete, and the pathway must be inactivated once cytokinesis is finished. In the studies proposed here, we will try to define at a molecular level how each of these steps in SIN regulation is accomplished. In addition, we will attempt to identify targets of the SIN crucial for its role in promoting cytokinesis. High cyclin dependent kinase (Cdk) activity in early mitosis inhibits premature SIN activation until chromosomes have segregated in anaphase. In Specific Aim 1, we will test whether this inhibition works through direct Cdk phosphorylation of SIN components, in particular Sid2p, Cdc7p, and Cdc11 p. Targets of the SIN required for cell division are not known. We will address this in Specific Aim 2 by using a candidate based approach to identify Sid2p substrates required for cell division in vivo. We have shown that during cytokinesis, the SIN acts not just to promote cytokinesis, but also to inhibit interphase cytoskeletal rearrangements, thereby coordinating completion of cytokinesis with initiation of the next cell cycle. In Specific Aim 3, we will determine the molecular mechanism by which the SIN inhibits interphase polarity, and the functional significance this inhibition has on successful completion of cytokinesis. Once the SIN is activated, its activity is maintained until cytokinesis is complete, and the SIN is inactivated once cytokinesis is completed. In Specifc Aim 4, we will examine how the Etd1p protein promotes SIN signaling, and whether destruction of Etd1p is the signal to inactivate the SIN upon completion of cytokinesis. Homologs of several SIN proteins in animal cells function as tumor suppressors. Because the basic mechanisms of cell division are highly conserved between yeast and humans, we expect characterization of the precise molecular interactions between SIN proteins will help elucidate how their mammalian homologs act to inhibit tumor formation.