CYTOKINESIS IN DICTYOSTELIUM--A MOLECULAR ANALYSIS

细胞生物学中最基本的过程之一就是分裂 一个母细胞分裂成两个子细胞， 将细胞质和遗传物质分成相等的两部分。 虽然这种胞质分裂过程明显涉及到收缩细胞， 蛋白质肌动蛋白和肌球蛋白，积累在沟作为一个 收缩环，实际上在分子水平上什么都不知道 关于这个过程的任何关键问题。 有多少 肌动蛋白和肌球蛋白集中在分裂细胞的沟区？ 这些蛋白质是怎么知道要集中在 在细胞周期中的正确时间和地点？ 详细的是什么 收缩环的分子结构 是什么打开了 收缩事件，什么终止了它？ 是什么限制了 开沟过程 收缩环是如何避开 在胞质分裂的最后阶段， 膜融合事件产生两个独立的子细胞？ 什么 表面牵引力在细胞分裂中是否发挥作用（如果有的话） 流程？ 这些只是需要解决的许多问题中的一部分 用分子术语来回答。 解决长期事业的关键 这个问题是一个模型系统的明智选择。Dictyostelium 盘状突是一种选择模式，因为它的行为特征 在有丝分裂和胞质分裂期间与哺乳动物细胞极其相似。 然而，它是一种简单得多的真核细胞，只有1%的 哺乳动物细胞的基因组大小。 此外，它具有单一副本 基因，它是单倍体，分子遗传学方法已经很好地工作， 同源重组非常有效。 另外还有按 大量关于胞质分裂中关键角色肌球蛋白的信息 分子，已经可用。 这一提议代表了一个长期的 致力于研究细胞质分裂的分子细节。奠定关键 为实现这一长期目标奠定基础， 当细胞进入有丝分裂并继续进行时肌球蛋白的动态再定位 通过胞质分裂将完成。 结构/功能 肌球蛋白在胞质分裂中的作用 将被审查。 确定其他关键基因的目标是 将继续研究所涉及的和分离所有必需蛋白质的方法。 最后，网骨藻种群胞质分裂的同步化 将尝试用于生物化学研究的细胞。

One of the most fundamental processes in cell biology is the division of a mother cell into two daughter cells, resulting in the faithful partitioning of the cytoplasm and genetic material into two equal parts. While this process of cytokinesis clearly involves the contractile proteins actin and myosin, which accumulate in the furrow as a contractile ring, virtually nothing is understood at the molecular level about any of the key issues surrounding this process. How much of the actin and myosin concentrates in the furrow region of the dividing cell? How do these proteins know to concentrate there at exactly the right place and at the right time in the cell cycle? What is the detailed molecular architecture of the contractile ring? What turns on the contractile event and what terminates it? What limits the velocity of the furrowing process? How does the contractile ring get out of the way in the final stages of cytokinesis so as not to inhibit the necessary membrane fusion event to yield two independent daughter cells? What role, if any, does traction on a surface play in the cell division process? These are just some of the many questions that need to be answered in molecular terms. Key to a long term undertaking to solve this problem is the judicious choice of a model system. Dictyostelium discoideum is a model of choice because it's behavioral characteristics during mitosis and cytokinesis are extremely similar to mammalian cells. It is, however, a much simpler eukaryotic cell with only 1 percent of the genome size of a mammalian cell. Furthermore, it has single copy genes, it is haploid, molecular genetic approaches have been well worked out, and homologous recombination is very efficient. In addition, a wealth of information about a key player in cytokinesis, the myosin molecule, is already available. This proposal represents a long-term commitment to study cytokinesis in molecular detail. To lay crucial groundwork towards this long-term goal, detailed characterization of the dynamic relocalization of myosin as cells enter mitosis and proceed through cytokinesis will be accomplished. The structure/function relationships of myosin in regard to its in vivo role in cytokinesis will be examined. The goal of identifying other key genes that are involved and isolating all of the essential proteins will be pursued. Finally, synchronization of cytokinesis in populations of Dictyostelium cells for biochemical studies will be attempted.