Regulation of Differentiation in Caulobacter

描述（由申请人提供）：本提案的目标是定义控制细菌细胞周期的调节机制，并了解这些机制如何在一个综合系统中起作用。我们已经证明，对新月形茎杆菌细胞周期的控制包括离散的转录模式，控制蛋白水解事件，在细胞周期的特定时间清除细胞中的关键调节蛋白，以及协调细胞周期调节活性的极性磷酸化信号蛋白的动态定位。一个由三种全球调控因子（CtrA, GcrA, DnaA）控制的转录网络在时间和空间上的振荡已被证明可以调节大约200个基因的时间表达。这种转录网络影响并受细胞亚细胞组织及其在细胞周期中的进行性变化的影响。细胞分裂前的细胞区隔化是子细胞特异性蛋白水解事件差异激活的关键信号。负责及时降解CtrA全局调节因子的CIpXP蛋白酶必须定位于具有CtrA底物的细胞极点才能发挥此功能。此外，CIpXP定位的时间由瞬时定位的CckA组氨酸激酶的信号传导控制，CckA组氨酸激酶也在细胞周期的正确时间介导CtrA的激活，从而创建一个强大的转录网络。我们将专注于识别负责蛋白质定位的因素和在细胞周期进程中起基本作用的蛋白质水解机制的动态调节，以及识别有助于和整合细胞周期调节网络的因素。此外，由于自由生物体必须随时适应不断变化的环境，因此了解这种调节回路不仅在最佳条件下如何工作，而且在细胞受到挑战时如何重新编程是至关重要的；以及当条件再次有利时，它又是如何重新开始的。我们将深入探讨个体调控机制，同时确定它们如何在时间和空间上运作的综合系统中发挥作用，以执行活细胞的功能。

DESCRIPTION (provided by applicant): The goal of this proposal is to define the regulatory mechanisms that control the bacterial cell cycle and to understand how these mechanisms function within an integrated system. We have shown that the control of the Caulobacter crescentus cell cycle incorporates discrete transcription patterns, controlled proteolytic events that clear the cell of critical regulatory proteins at defined times in the cell cycle, and dynamic localization of polar phospho- signaling proteins that orchestrates the activity of cell cycle regulators. A transcriptional network governed by three global regulators (CtrA, GcrA, DnaA) that oscillate out of phase temporally and spatially has been shown to regulate the temporal expression of approximately 200 genes. This transcriptional network influences and is influenced by the subcellular organization of the cell and its progressive changes during the cell cycle. Cellular compartmentalization preceding cell division is a critical signal for the differential activation of specific proteolytic events in the daughter cells. The CIpXP protease, responsible for the timely degradation of the CtrA global regulator, must be localized at the cell pole with its CtrA substrate for this function. Further, the timing of CIpXP localization is controlled by signaling from the transiently localized CckA histidine kinase that also mediates the activation of CtrA at the correct time in the cell cycle, thus creating a robust transcriptional network. We will focus on identifying the factors responsible for protein localization and the dynamic regulation of the proteolytic mechanisms that play a fundamental role in cell cycle progression, and identifying the factors that contribute to and integrate cell cycle regulatory networks. In addition, because free living organisms must readily adapt to a changing environment, it is critical to understand how this regulatory circuitry works not only under optimal conditions, but also how it is re-programmed when the cell is challenged; and how, when conditions are favorable again, it begins anew. We will explore individual regulatory mechanisms in depth while determining how they function in an integrated system that operates in time and space to carry out the functions of a living cell.