Cell Cycle Regluation in Caulobacter crescentus

描述(由申请人提供)：细胞周期的适当的空间和时间调节对所有生物的生存和增殖至关重要。为了确保稳定、有序的细胞周期进程，细胞使用复杂的遗传电路。这类电路的架构、运行和设计原则仍然知之甚少。新月芽孢杆菌为研究遗传回路和阐明细胞周期调控的基本分子机制提供了一个实验上容易掌握的系统。在Crescentus中，细胞周期是由主调控子CtrA活动的周期性起伏驱动的。活性CtrA直接调控近100个基因的表达，其中许多基因协调细胞分裂。CTRA还直接与复制起点结合并使其沉默。因此，细胞周期进程需要CtrA活动的振荡--它必须从细胞中清除以允许DNA复制，但必须积累以驱动细胞分裂。控制CtrA的遗传回路的轮廓已经到位，但还没有完全解释CtrA活动的动态。监管的其他组成部分和水平必须存在。这个项目的目标是定义控制CtrA活性的完整分子电路，从而确保细胞周期的有序进行。为此，我们将：(I)绘制调控CtrA磷酸化和去磷酸化的途径；(Ii)阐明细胞如何控制CtrA的亚细胞定位和活性；(Iii)研究多个转录反馈环如何协作来精确控制CtrA的诱导动力学；以及(Iv)确定和表征调节CtrA活性的其他因素。这些研究将有助于揭示细胞如何使用多种调节模式来成功地驾驭其细胞周期。此外，这项工作将有助于揭示基因电路的一般设计和操作原理，这些原理是整个生物学调控过程的基础。最后，更好地了解细菌如何调节细胞周期可能有助于指导新抗生素的开发，这是一个日益与公共健康相关的问题。

DESCRIPTION (provided by applicant): Proper spatial and temporal regulation of the cell cycle is crucial to the survival and proliferation of all organisms. To ensure stable, orderly cell cycle progression, cells employ complex genetic circuits. The architecture, operation, and design principles of such circuits remain only poorly understood. The bacterium Caulobacter crescentus provides an experimentally tractable system for studying genetic circuits and for elucidating fundamental molecular mechanisms of cell cycle regulation. In C. crescentus the cell cycle is driven by the periodic rise and fall in activity of a master regulator, CtrA. Active CtrA directly regulates the expression of nearly 100 genes, many of which coordinate cell division. CtrA also directly binds to and silences the origin of replication. Cell cycle progression therefore requires oscillations in CtrA activity - it must be cleared from the cell to permit DNA replication, but must accumulate to drive cell division. The outline of a genetic circuit controlling CtrA is in place, but does not yet fully account for the dynamics of CtrA activity. Additional components and levels of regulation must exist. The goal of this project is to define the complete molecular circuitry that controls CtrA activity and hence ensures orderly progression through the cell cycle. To this end, we will: (i) map the pathways that regulate phosphorylation and dephosphorylation of CtrA, (ii) elucidate how cells control the sub-cellular localization and activity of CckA, the primary phosphodonor for CtrA (iii) examine how multiple transcriptional feedback loops collaborate to precisely control the induction dynamics of CtrA, and (iv) identify and characterize additional factors that regulate CtrA activity. These studies will help to unveil how cells use multiple modes of regulation to successfully navigate their cell cycle. In addition, this work will help to reveal the general design and operating principles of genetic circuits, which underlie regulatory processes throughout biology. Finally, a better understanding of how bacteria regulate the cell cycle may help guide the development of new antibiotics, a problem of increasing public-health relevance.