The Mechanism and Regulation of Cytokinesis in Yeast

描述(申请人提供)：有丝分裂细胞分裂是真核生物生长和发展的基础。导致后代细胞胞质分离的细胞分裂的最后一个关键步骤是被称为胞质分裂的过程。动物细胞和酵母中的胞质分裂需要由肌动球蛋白为基础的收缩环驱动的膜收缩，并在细胞分裂部位定向插入膜。成功的细胞分裂依赖于这些细胞运动事件与染色体分离的空间和时间协调。我们一直使用萌芽酵母酿酒酵母作为模型来研究细胞质分裂所需的复杂的结构和调控步骤。我们已经证明，在萌芽酵母中，收缩环的组装发生在两个暂时分离的阶段，在此期间，肌球蛋白-II和肌动蛋白细丝组装成连接母细胞和子细胞的芽颈周围的环。在胞质分裂开始时，这个环的收缩由有丝分裂退出网络调节。胞质分裂前后，胞外途径也被导向芽颈，初步结果表明这一事件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是如何在G1/S转变时被招募到细胞分裂的部位，以及肌动蛋白细丝是如何在后期的收缩环中组装的。其次，我们将尝试确定有丝分裂退出网络在触发胞质分裂开始中的分子靶点(S)。最后，我们将研究在有丝分裂过程中胞外途径是如何导向细胞分裂部位的。实验方法涉及遗传、生化和显微成像技术的组合。由于酵母和动物细胞的细胞周期调控途径和细胞分裂部位的结构成分相似，我们的研究可能为真核生物中控制胞质分裂的保守机制提供有价值的见解。

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.