TEMPORAL AND SPATIAL CONTROL OF BACTERIAL CYTOKINESIS

描述(申请人提供)：细胞如何决定何时何地分裂是现代生物学的重大问题之一。在空间上，分割受到严格的监管，以确保隔膜的准确定位。在时间上，分裂与细胞生长、DNA复制和染色体分离相协调，以确保子代细胞具有合适的大小和完整的基因组。在从人类到细菌的有机体中，细胞通过在新生的分裂部位形成细胞骨架蛋白环来启动分裂。在细菌中，这个环由基本的微管蛋白样GTP酶FtsZ组成。细菌主要通过调节FtsZ组装动态的因素的协同作用来实现对分裂的精确控制。因此，要想了解细菌分裂的空间和时间规律，就需要识别和表征调节FtsZ组装的因素。虽然我们已经开始了解阻止FtsZ在异常亚细胞位置组装并维持FtsZ环完整性的因素，但对协调FtsZ环形成与细胞生长和细胞周期的机制知之甚少。这项建议有三个主要目标：第一，剖析控制UGTP和OpgH活性的营养依赖机制，这是一种分裂抑制剂，分别导致枯草杆菌和大肠杆菌中细胞大小的生长速度依赖性增加；第二，识别和表征负责大肠杆菌细胞大小稳态的调控电路的其他组件；第三，通过使用遗传学、生物化学和超分辨显微镜的综合方法，评估FtsZ的非结构C-末端结构域--FtsZ与其调节蛋白之间相互作用的主要部位--对细胞动环的组装和完整性的贡献。这个项目还应该有助于阐明更广泛的科学重要性问题。FtsZ和影响其活性的因子是细菌细胞分裂机制的重要组成部分，因此是开发新抗生素的有吸引力的目标。此外，对大肠杆菌和枯草杆菌这两种高度分化的模式生物细胞分裂的时空控制因素进行了比较分析， 承诺揭示生命所有领域基本的细胞周期调控的潜在方面。最后，了解正常情况下控制细胞分裂的分子机制应该有助于确定为什么这些机制在肿瘤发生过程中失败，并导致癌症的异常分裂和快速细胞增殖特征。

DESCRIPTION (provided by applicant): How cells determine when and where to divide is one of the great questions in modern biology. Spatially, division is tightly regulated to ensure th accurate positioning of septa. Temporally, division is coordinated with cell growth, DNA replication, and chromosome segregation to ensure that daughter cells are the appropriate size and have complete genomes. In organisms from humans to bacteria, cells initiate division by the formation of a cytoskeletal protein ring at the nascent division site. In bacteria this ring is composed of the essential tubulin-like GTPase FtsZ. Bacteria achieve precise control over division primarily through the concerted actions of factors that modulate FtsZ assembly dynamics. Comprehending the spatial and temporal regulation of bacterial division, thus, requires the identification and characterization of factors that modulate FtsZ assembly. While we have begun to understand the factors responsible for preventing FtsZ assembly at aberrant subcellular locations and for maintaining integrity of the FtsZ ring, much less is known about the mechanisms responsible for coordinating FtsZ ring formation with cell growth and the cell cycle. This proposal has three primary objectives: first, to dissect the nutrient-dependent mechanisms governing the activity of UgtP and OpgH, division inhibitors that contribute to growth rate-dependent increases in cell size in B. subtilis and E. coli respectively; second, to identify and characterize additional components of the regulatory circuit responsible for E. coli cell size homeostasis; and, third, to assess the contribution of FtsZ's unstructured C-terminal domain -- a primary site of interaction between FtsZ and its modulatory proteins -- to the assembly and integrity of the cytokinetic ring via an integrated approach employing genetics, biochemistry, and superresolution microscopy. This project should also help shed light upon questions of broader scientific importance. FtsZ and the factors governing its activity are essential components of the bacterial cell division machinery and are therefore attractive targets for the development of new antibiotics. Furthermore, comparative analysis of the factors responsible for the spatial and temporal control of cell division in E. coli and B. subtilis, two highly divergent model organisms, promises to reveal underlying aspects of cell cycle regulation fundamental to all domains of life. Finally, understanding the molecular mechanisms that normally control cell division should help identify why these mechanisms fail during oncogenesis, and lead to the aberrant divisions and rapid cell proliferation characteristic of cancer.