Mechanism and Regulation of Cytokinesis in Yeast

描述（由申请人提供）：有丝分裂细胞分裂是真核生物生长和发育的基础。细胞分裂的最后一个关键步骤是细胞质分裂，导致子代细胞的细胞质分离。动物细胞和酵母中的胞质分裂需要由基于肌动球蛋白的收缩环驱动的膜收缩和在细胞分裂位点处的靶向膜插入。成功的细胞分裂依赖于这些细胞动力学事件与染色体分离的空间和时间协调。我们一直使用芽殖酵母酿酒酵母作为模型来研究胞质分裂所需的复杂结构和调控步骤。我们已经表明，在芽殖酵母中的收缩环的组装发生在两个时间上独立的阶段，在此期间，肌球蛋白-II和肌动蛋白丝组装成一个环周围的芽颈连接母细胞和子细胞。在胞质分裂开始时，这个环的收缩受有丝分裂出口网络的调节。胞吐途径也在胞质分裂的时候指向芽颈，初步结果表明，这是胞质分裂所必需的。 提出了三个具体目标。首先，我们将进一步研究肌球蛋白-II是如何招募到G1/S转换的细胞分裂的网站，以及肌动蛋白丝是如何组装在收缩环在后期。第二，我们将尝试确定有丝分裂出口网络中触发胞质分裂开始的分子靶点。最后，我们将探讨如何外排途径是针对细胞分裂网站在有丝分裂。实验方法涉及遗传学，生物化学和显微镜成像技术的组合。由于酵母和动物细胞之间的细胞周期调控途径和细胞分裂位点的结构组分是相似的，我们的研究可能会提供有价值的见解，在真核生物中控制胞质分裂的保守机制。

DESCRIPTION (provided by applicant): Mitotic cell division is fundamental to the growth and development of eukaryotic organisms. The final crucial step in cell division that results in cytoplasmic separation of progeny cells is a process known as cytokinesis. Cytokinesis in animal cells and yeast require membrane constriction driven by an actomyosin-based contractile ring and targeted membrane insertion at the site of cell cleavage. Successful cell division depends on spatial and temporal coordination of these cytokinetic events with chromosome segregation. We have been using the budding yeast Saccharomyces cerevisiae as the model to study the intricate structural and regulatory steps required for cytokinesis. We have shown that assembly of the contractile ring in budding yeast occurs in two temporally separate stages during which myosin-II and actin filaments assemble into a ring around the bud neck connecting the mother and daughter cells. Contraction of this ring at the onset of cytokinesis is regulated by the mitotic exit network. The exocytic pathway is also directed to the bud neck around the time of cytokinesis, and preliminary results suggest that this event is required for cytokinesis. Three specific aims are proposed. First, we will further investigate how myosin-II is recruited to the site of cell division at the G1/S transition and how actin filaments are assembled in the contractile ring during anaphase. Second, we will try to identify the molecular target(s) of the mitotic exit network in triggering the onset of cytokinesis. Finally, we will investigate how the exocytic pathway is directed toward cell division site during mitosis. The experimental approach involves a combination of genetic, biochemical, and microscopy imaging techniques. Because the cell cycle regulatory pathways and the structural components of the cell division site are similar between yeast and animal cells, our study is likely to provide valuable insights into the conserved mechanisms that control cytokinesis in eukaryotes.