Molecular mechanisms regulating cell cycle progression in Caulobacter crescentus

新月柄杆菌细胞周期进程的分子机制

• 批准号: 7613616
• 负责人: Lisa M. Bowers
• 金额: $ 4.72万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7613616
• 关键词: Agriculture; Anti-Bacterial Agents; Antibiotics; Antibodies; Aspartate; Bacteria; Bacteriophages; Binding; Bioinformatics; Biological Models; Biological Warfare; Biology; Biomedical Engineering; Biosensing Techniques; Caulobacter; Caulobacter crescentus; Cell Cycle; Cell Cycle Progression; Cell Cycle Regulation; Cell Survival; Cell division; Cells; Cellular biology; Chimeric Proteins; Complex; Comprehension; Coupled; DNA biosynthesis; Defect; Drug Delivery Systems; Essential Genes; Eukaryotic Cell; Flagella; Genes; Genetic; Genetic Transcription; Genome; Hand; Histidine; Hybrids; In Vitro; Label; Life; Life Cycle Stages; Location; Logic; Molecular; Monitor; Morphology; Mutation; Names; Orthologous Gene; Pathway interactions; Phenotype; Phosphoric Monoester Hydrolases; Phosphorylation; Phosphotransferases; Physiologic pulse; Prokaryotic Cells; Property; Proteins; Proteobacteria; Reaction; Replication Origin; Role; Shapes; Signal Transduction; Site; Source; Surface; Time; Water; Work; cell motility; chromosome replication; daughter cell; drug discovery; in vivo; insight; loss of function; mutant; promoter; protein-histidine kinase; public health relevance; reconstitution; response; small molecule; transcription factor

DESCRIPTION (provided by applicant): A fundamental question in biology is how one cell divides to yield two progeny with different identities. Like eukaryotic cells, bacteria undergo complex life cycles and often produce daughter cells with distinct shapes and properties. In this work, Caulobacter crescentus is used as a model system for the study of asymmetry coupled to the division cycle. In this bacterium, each division produces two morphologically distinct daughter cells, a non-motile cell with a stalk that attaches to surfaces and a motile swarmer cell with a flagellum that propels it through the water. The stalked cell immediately begins a new round of chromosome replication and division, but the swarmer cell is unable to initiate DMA replication until it differentiates into a stalked cell. This complex cell division cycle is orchestrated by a network of two-component signal transduction proteins. The response regulator CtrA is a transcription factor that controls the expression of many cell cycle- regulated genes but also blocks DNA replication by binding to the origin of replication. CtrA activity is required for cell viability but it must be temporarily eliminated in stalked cells to permit the initiation of chromosome replication. CtrA activity is indirectly opposed by the essential response regulator DivK. Phosphorylated DivK results in a decrease in CtrA activity, which ultimately allows chromosome replication in the stalked cell. Thus, phosphorylation of DivK is essential for viability. DivK is known to be activated by the histidine kinase (HK) DivJ but because DivJ is dispensible, DivK must be phosphorylated by another HK or small molecule phosphodonor in Caulobacter. We propose a whole-genome approach to identify other HKs that could participate in DivK phosphorylation. Specifically, we aim to delete the gene for each of the 59 non-essential HKs in combination with a divJ deletion. This approach has yielded a likely candidate which we have tentatively named DivM other candidates must still be ruled out. We also aim to characterize the terminal phenotype of cells lacking both DivJ and DivM, determine the location and activity of DivM during the cell cycle, and elucidate the phosphorylation pathway from DivM to DivK. PUBLIC HEALTH RELEVANCE: The work proposed here is integral to achieving a complete understanding of the regulatory cascade leading to cell-cycle progression and differentiation in Caulobacter. Comprehension of the regulatory cascade could have far-reaching implications because many of the mechanisms discovered in Caulobacter are conserved among other species with important roles in agriculture, biowarfare, biosensing, and bioengineering. In addition, elucidating the basic mechanisms involved in bacterial cell cycle progression will generate key insights into prokaryotic cell biology, which will in turn help to identify new targets for antibacterial drug discovery.

描述（申请人提供）：生物学中的一个基本问题是一个细胞如何分裂产生两个具有不同身份的后代。像真核细胞一样，细菌经历复杂的生命周期，经常产生具有不同形状和特性的子细胞。在这项工作中，用新月形茎杆菌作为模型系统来研究与分裂周期耦合的不对称性。在这种细菌中，每次分裂都会产生两个形态不同的子细胞，一个是非运动细胞，它的茎附着在表面上，另一个是运动细胞，它的鞭毛推动它在水中游动。被跟踪的细胞立即开始新一轮的染色体复制和分裂，但是集群细胞在分化成被跟踪的细胞之前无法启动DMA复制。这种复杂的细胞分裂周期是由双组分信号转导蛋白网络精心策划的。反应调节因子CtrA是一种转录因子，它控制许多细胞周期调节基因的表达，但也通过与复制起点结合来阻止DNA复制。CtrA活性是细胞生存所必需的，但它必须在跟踪细胞中暂时消除，以允许染色体复制的开始。CtrA活性受到基本反应调节因子DivK的间接反对。磷酸化的DivK导致CtrA活性降低，这最终允许在跟踪细胞中进行染色体复制。因此，DivK的磷酸化对生存能力至关重要。DivK已知由组氨酸激酶（HK） DivJ激活，但由于DivJ是不可缺少的，DivK必须由另一个HK或小分子磷酸供体在茎状杆菌中磷酸化。我们提出了一种全基因组方法来鉴定可能参与DivK磷酸化的其他hk。具体来说，我们的目标是删除59个非必需hk中的每一个基因，同时删除divJ。这种方法产生了一个可能的候选者，我们暂时将其命名为DivM，其他候选者仍然必须排除。我们还旨在描述缺乏DivJ和DivM的细胞的终端表型，确定DivM在细胞周期中的位置和活性，并阐明从DivM到DivK的磷酸化途径。公共卫生相关性：本文提出的工作对于全面了解导致茎状杆菌细胞周期进展和分化的调控级联是不可或缺的。由于在Caulobacter中发现的许多机制在其他物种中保守，在农业、生物战、生物传感和生物工程中发挥重要作用，因此对调控级联的理解可能具有深远的意义。此外，阐明细菌细胞周期进程的基本机制将产生对原核细胞生物学的关键见解，这将有助于确定抗菌药物发现的新靶点。