GENERATION OF ASYMMETRY DURING CAULOBACTER DEVELOPMENT

茎杆菌发育过程中不对称性的产生

• 批准号: 2185612
• 负责人: JAMES W GOBER
• 金额: $ 12.89万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-08-01 至 1997-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2185612
• 关键词: Caulobacter; DNA binding protein; DNA directed RNA polymerase; DNA replication; bacterial genetics; bacterial proteins; cell cycle; cellular polarity; flagellum; gene expression; genetic promoter element; genetic regulatory element; genetic transcription; immunoelectron microscopy; immunofluorescence technique; nucleic acid structure; synchronous cell division; transcription factor

The bacterium, Caulobacter crescentus expresses a polarity during its cell cycle, that is generated by a simple developmental program. Cell division yields morphologically and biochemically dissimilar daughter cells; a swarmer cell that possesses a single polar flagellum and a non-motile stalked cell. This asymmetric cell division is analogous to those that occur during development of other organisms such as Drosophila, yeast and the nematode. The asymmetry that yields unique progeny cells in Caulobacter is expressed in the predivisional cell. Polarity is established by the localized biogenesis of a flagellum and the chemotaxis apparatus at the incipient swarmer cell pole. The newly replicated chromosomes at each pole of the predivisional cell also differ with respect to their sedimentation coefficient, and their ability to initiate replication once cell division is completed. Caulobacter possesses a fully accessible system of genetic analysis. In addition, synchronized cultures are easy to obtain and experimentally manipulate. This has permitted the direct molecular analysis of a fundamental problem in developmental biology; the generation of asymmetry. The nature of the morphogenetic changes exhibited by the Caulobacter cell cycle also allows the analysis of the regulation of temporally controlled gene expression and the molecular basis of positional information. The expression of positional information in Caulobacter appears to derive from at least two different mechanisms: proteins are localized to a specific site in the predivisional cell, and in some cases, the mRNA encoding localized proteins is sequestered to one of the predivisional cell poles. For a subset of flagellar genes, positional information is generated through localized transcription in one pole of the cell. Thus, newly replicated chromosomes in the predivisional cell, not only differ in their the ability to initiate DNA replication, but also in their program of gene expression: Our overall research goals are to define the mechanisms by which this differential, global programming of the Caulobacter chromosome is accomplished. The spatially expressed flagellar promoters all require sigma54-containing RNA polymerase for transcription. In addition, they possess similar cis-regulatory elements, an enhancer sequence which is a binding site for a protein called Rf-1 and a binding site for the DNA bending protein, Integration Host Factor (IHF). Therefore, it is probably through a common mechanism that localized transcription of these promoters is accomplished. To accomplish our research goals, we will define the mechanisms of both temporal and spatial transcriptional activation of locally expressed flagellar promoters, using a both a biochemical and genetic approach. We will also assay the intracellular location of the trans-acting factors that arc important for transcription of these promoters. Finally, we will investigate the role IHF and higher-order DNA structure have in influencing both the temporal and spatial program of flagellar gene expression.

细菌，花椰菜新月形在其细胞中表达极性 循环，这是由简单的开发程序生成的。 细胞分裂 在形态和生化上产生不同的子细胞；一个 具有单个极性鞭毛和非运动的蜂窝细胞 跟踪细胞。 这种不对称的细胞分裂类似于 发生在果蝇，酵母和其他生物的开发期间 线虫。 产生独特后代细胞的不对称性 花椰菜在预分离细胞中表达。 极性是 通过鞭毛和趋化性的局部生物发生建立 处于初期蜂窝细胞杆的设备。 新复制 前细胞的每个极点处的染色体也随着尊重而有所不同 达到他们的沉积系数，以及他们发起的能力 复制一旦细胞分裂完成。 花椰菜完全拥有 可访问的遗传分析系统。 另外，同步文化 易于获取和实验操作。 这允许 对发展中基本问题的直接分子分析 生物学;不对称的产生。 形态发生的性质 花椰菜细胞周期所表现出的变化也可以分析 时间控制基因表达和分子的调节 位置信息的基础。 位置信息的表达 在Caulobacter中，似乎至少来自两种不同的机制： 蛋白质位于前元细胞中的特定部位，并在 在某些情况下，编码局部蛋白质的mRNA被隔离为一种 前细胞两极。 对于鞭毛基因的子集，位置 信息是通过局部转录生成的 细胞。 因此，在预先细胞中新复制的染色体，而不是 他们启动DNA复制的能力只有不同，但也 他们的基因表达计划：我们的总体研究目标是定义 这种差异化的全球编程的机制 花椰菜染色体已完成。 空间表达的鞭毛 启动子都需要含SigMA54的RNA聚合酶进行转录。 此外，它们具有相似的顺式调节元素，增强剂 序列是称为RF-1和结合的蛋白质的结合位点 DNA弯曲蛋白，整合宿主因子（IHF）的位点。 因此，可能是通过一种共同的机制来定位的 这些启动子的转录已完成。 完成我们的 研究目标，我们将定义时间和空间的机制 使用本地表达的鞭毛启动子的转录激活 一种生化和遗传方法。 我们还将分析 跨性别因子的细胞内位置对 这些启动子的转录。 最后，我们将调查角色 IHF和高阶DNA结构都在影响时代 和鞭毛基因表达的空间程序。