CYTOKINESIS IN DICTYOSTELIUM--A MOLECULAR ANALYSIS

细胞生物学中最基本的过程之一是分裂 一个母细胞变成两个子细胞，结果是忠实的 把细胞质和遗传物质分成两个相等的部分。 虽然这种胞质分裂的过程明显涉及到收缩 肌动蛋白和肌球蛋白，它们以一种 收缩环，在分子水平上几乎什么都不知道 关于围绕这一过程的任何关键问题。其中有多少是 肌动蛋白和肌球蛋白集中在分裂细胞的沟槽区域？ 这些蛋白质是如何知道集中在正确的位置的？ 在细胞周期中的正确时间和地点？具体内容是什么？ 收缩环的分子结构？是什么打开了 收缩事件以及是什么终止了它？是什么限制了 起皱的过程？收缩环是如何避开的？ 在胞质分裂的最后阶段，以免抑制必要的 膜融合事件产生两个独立的子细胞？什么 如果有的话，表面上的牵引力在细胞分裂中起作用 流程呢？这些只是许多需要解决的问题中的一部分 用分子术语来回答。解决长期事业的关键 这个问题是对模式体系的明智选择。网柄网柄菌属 Discoideum是一种选择模型，因为它的行为特征 有丝分裂和胞质分裂与哺乳动物细胞极为相似。 然而，它是一个简单得多的真核细胞，只有1% 哺乳动物细胞的基因组大小。此外，它只有一份副本 基因，它是单倍体，分子遗传学的方法已经很好地工作了 而同源重组是非常有效的。此外，a 关于胞质分裂中的关键角色--肌球蛋白的丰富信息 分子，已经可以使用了。这项建议代表了一项长期的 致力于研究细胞质分裂的分子细节。把关键放在 为实现这一长期目标奠定基础，详细描述 当细胞进入有丝分裂并继续进行时肌球蛋白的动态重新定位 通过胞质分裂将被完成。结构/功能 肌球蛋白在胞质分裂中的作用 将会被检查。识别其他关键基因的目标是 将致力于参与和分离所有必要的蛋白质。 最后，网柄苔藓种群中胞质分裂的同步性 将尝试进行生化研究的细胞。

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.