Temporal and Spatial Control of B subtilis cytokinesis

描述（由申请人提供）：细胞如何决定何时何地分裂仍然是现代生物学最大的谜团之一。在空间上，严格规范分割，保证间隔的准确定位。在时间上，分裂与DNA复制和染色体分离相协调。从细菌到酵母菌再到人类，细胞分裂都是由细胞骨架蛋白环的形成引发的。这个环确定了分隔隔膜的位置，并作为分隔装置组装的框架。在细菌中，这个环是由必需的类微管蛋白GTPase FtsZ组成的。本研究的重点是土壤细菌枯草芽孢杆菌FtsZ环形成的调控网络。确定分裂位点和FtsZ环形成与细胞周期耦合的因素尚不清楚。因此，理解细菌分裂的时空调控需要识别细胞和分子机制，这些机制刺激FtsZ环在细胞周期提示下在中间细胞形成，并抑制FtsZ环在所有其他位点的形成。EzrA是一种有助于限制FtsZ环在中间细胞形成的因子，通过经典的遗传筛选被确定。初步的生化数据表明，EzrA直接与FtsZ相互作用，抑制FtsZ聚合物的不稳定形成环。这项提议有三个主要目标。第一，表征以斯拉防止异位FtsZ环形成的分子机制。第二，克隆并鉴定由wee2鉴定的基因，wee2是一种使细胞分裂与生长分离的突变，导致形成小细胞，许多细胞的大小不到野生型枯草芽孢杆菌的25%。第三，扩大遗传筛选，以确定(i)促进细胞中间FtsZ环形成的其他因素，（ii）将FtsZ环形成与细胞周期结合，以及（iii）抑制不适当位置的FtsZ环形成。作为细菌细胞分裂机制的重要组成部分，FtsZ和控制其活性的因素有望成为开发新抗生素的潜在靶点。此外，这项工作不仅可以阐明细菌细胞分裂，还可以阐明所有生物基本的细胞分裂方面。了解通常控制细胞分裂的分子机制将有助于确定为什么它们在肿瘤发生过程中失败，导致癌细胞的异常分裂和快速增殖特征。

DESCRIPTION (provided by applicant): How cells determine when and where to divide remains one of the great mysteries of modern biology. Spatially, division is tightly regulated to ensure the accurate positioning of septa. Temporally, division is coordinated with DNA replication and chromosome segregation. From bacteria to yeast to humans, cell division is initiated by the formation of a ring of a cytoskeletal protein at the nascent division site. This ring establishes the location of the division septum and serves as a framework for assembly of the division apparatus. In bacteria this ring is composed of the essential tubulin-like GTPase FtsZ. This proposal focuses on the regulatory networks that govern FtsZ ring formation in the soil bacterium B. subtilis. The factors that establish the division site and couple FtsZ ring formation to the cell cycle remain unknown. Comprehending the spatial and temporal regulation of bacterial division thus requires the identification of the cellular and molecular mechanisms that stimulate FtsZ ring formation at midcell in response to cell cycle cues and inhibit FtsZ ring formation at all other sites. EzrA, a factor that helps restrict FtsZ ring formation to midcell, was identified through classical genetic screens. Preliminary biochemical data suggest that EzrA interacts directly with FtsZ to inhibit ring formation by destabilization of FtsZ polymers. This proposal has three major goals. One, to characterize the molecular mechanism by which EzrA prevents ectopic FtsZ ring formation. Two, to clone and to characterize the gene identified by wee2, a mutation that uncouples cell division from growth, leading to the formation of small cells, many less than 25% the size of wild type B. subtilis. Three, to extend genetic screens to identify additional factors that (i) promote FtsZ ring formation at midcell, (ii) couple FtsZ ring formation to the cell cycle, and (iii) inhibit FtsZ ring formation at inappropriate sites. As essential components of the bacterial cell division machinery, FtsZ and the factors governing its activity hold promise as potential targets for the development of new antibiotics. Furthermore, this work should illuminate not only bacterial cell division, but also aspects of cytokinesis fundamental to all organisms. Understanding the molecular mechanisms that normally control cell division will help identify why they fail during oncogenesis, leading to the aberrant divisions and rapid proliferation characteristic of cancer cells.