REGULATION OF DIFFERENTIATION IN CAULOBACTER

我们的目标是了解构成细胞的机制。 差异化。这一过程的一个例子是不对称 细胞成分在分裂前的分布导致 具有不同特性的子代细胞的发生。这个表达方式 不对称性是正常发育中的一个关键事件。一个主要的地标 杆状杆菌的不对称性是鞭毛的局部生物发生 位于分裂前细胞一端的趋化器。这个 构建鞭毛所需的基因在一种调控的 在细胞周期中的指定时间启动的层次结构。这个 拟议的研究有三个主要目标。第一个是识别 时间可控发作的机制 鞭毛调节层级的表达。要做到这一点，我们将 确定启动子、调控序列和反式作用因子 控制层次结构中初始基因的时间表达， 并分离和鉴定影响其表达或 时机到了。在这种情况下，我们已经证明了编码sigma54的rpoN是 对于所有极地分化事件都是必需的。RpoN的转录 是临时控制的，并且是 鞭毛层级。我们将研究rpoN表达的控制和 它的全球功能。第二个目标是基于我们最近的 趋化蛋白定位于细胞极点的观察 大肠埃希氏菌和铜绿假单胞菌。我们将确定是否有 导致趋化和趋化的极地定位的一般机制 鞭毛蛋白及其在形态发生过程中的后续蛋白分解。 第三个目标是确定结构基因的顺序 表达对于极地鞭毛的组装是必不可少的。 可能细胞是由分子机器组成的，比如 趋化装置、细胞分裂装置和极性复合体 用于鞭毛组装，形成空间分离的功能 蛋白质组。事实上，细菌细胞看起来相当 高度有条理，而且有很多关于 蛋白质和蛋白质的极性、位置信息和靶向 在一个相对简单的细胞中，完全服从于 基因和生化操作。

Our goal is to understand the mechanisms that underlie cellular differentiation. An example of this process is the asymmetric distribution of cellular components prior to division that leads to the genesis of progeny cells with different characteristics. This expression of asymmetry is a crucial event in normal development. A major landmark of asymmetry in Caulobacter is the localized biogenesis of a flagellum and the chemotaxis apparatus at one pole of the predivisional cell. The genes required to build the flagellum are ordered in a regulatory hierarchy that is initiated at a defined time in the cell cycle. The proposed research has three main objectives. The first is to identify the mechanisms responsible for the temporally controlled onset of expression of the flagellar regulatory hierarchy. To do this we will identify the promoter, regulatory sequences and trans-acting factors that control the temporal expression of the initial genes in the hierarchy, and isolate and characterize mutants that affect their expression or timing. In this context, we have shown that rpoN, encoding sigma54, is required for all polar differentiation events. The transcription of rpoN is temporally controlled and required for subsequent steps in the flagellar hierarchy. We will examine the control of rpoN expression and its global function. The second objective is based on our recent observations that chemotaxis proteins are localized at the cell pole in e. coli as well as in Caulobacter. We will determine if there are general mechanisms that lead to polar localization of the chemotaxis and flagella proteins and their subsequent proteolysis during morphogenesis. The third objective is to determine if the order of structural gene expression is essential for the assembly of the polar flagellum. It may be that the cell is composed of 'molecular machines', such as the chemotaxis apparatus, the cell division apparatus, and a polar complex used for flagellar assembly, that form spatially segregated functional groups of proteins. The bacterial cell appears, in fact, to be quite highly organized, and much is to be learned about the mechanisms of polarity, positional information, and targeting of proteins and protein complexes, in a relatively simple cell that is completely amenable to genetic and biochemical manipulation.