The 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发育的基础。导致子代细胞细胞质分离的细胞分裂的最后一个关键步骤是细胞质分裂。动物细胞和酵母的细胞质分裂需要由基于肌动球蛋白的收缩环驱动的膜收缩，并在细胞切割部位靶向膜插入。成功的细胞分裂取决于这些细胞动力学事件与染色体分离的时空协调。我们一直以出芽酵母酿酒酵母（Saccharomyces cerevisiae）为模型来研究细胞分裂所需的复杂结构和调控步骤。我们已经证明，出芽酵母收缩环的组装发生在两个暂时分开的阶段，在这个阶段，肌凝蛋白- ii和肌动蛋白丝在芽颈周围组装成一个连接母细胞和子细胞的环。这个环在细胞分裂开始时的收缩是由有丝分裂出口网络调节的。胞外通路在胞质分裂前后也指向芽颈，初步结果表明这一事件是胞质分裂所必需的。

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.