Phosphorylation of the Caulobacter Cell Cycle Regulator CtrA by Two Essential Kinases

月牙根杆菌以两种不同的细胞类型存在，即运动的群集细胞和静止的跟踪细胞。每次茎状杆菌分裂，每一种类型的细胞都会产生一个，这一过程被称为不对称细胞分裂。群集细胞不能进行染色体复制和细胞分裂。为了分裂，集群细胞必须首先分化成可以启动染色体复制的跟踪细胞。非对称细胞分裂和一种细胞类型向另一种细胞类型的分化是所有高等生物发育的基本过程，而Caulobacter提供了一个相对简单的模型系统来详细研究它们。被称为双组分蛋白的信号转导蛋白网络协调复杂的茎状杆菌生命周期。Ryan实验室的研究重点是CtrA，这是一种通过影响多个基因的转录来调节细胞周期的双组分蛋白质。CtrA必须是活跃的，以促进参与细胞分裂的基因的转录，但在细胞周期的早期，CtrA必须是不活跃的，因为它也阻断了染色体复制的起始。该项目的目标是确定CckA和DivL这两种必需激酶如何在细胞周期的正确时间通过磷酸化激活CtrA。这个项目的教育部分是本科生的暑期实验课程，每个学生将破坏一个以前未研究过的Caulobacter基因，并描述由此产生的突变表型。学生将学习分子生物学和遗传学的基本技术，同时在微生物学方面做出原创性贡献。

The bacterium Caulobacter crescentus exists as two distinct cell types, motile swarmer cells and stationary stalked cells. Each time Caulobacter divides, one cell of each type is produced, in a process called asymmetric cell division. The swarmer cell is incapable of chromosome replication and cell division. In order to divide, the swarmer cell must first differentiate into a stalked cell that can initiate chromosome replication. Asymmetric cell division and differentiation of one cell type into another are fundamental processes in the development of all higher organisms, and Caulobacter provides a relatively simple model system in which to study them in detail. A network of signal transduction proteins called two-component proteins orchestrates the complex Caulobacter life cycle. Research in the Ryan lab focuses on CtrA, a two-component protein that regulates the cell cycle by affecting the transcription of multiple genes. CtrA must be active to promote the transcription of genes involved in cell division, but earlier in the cell cycle CtrA must be inactive, because it also blocks the initiation of chromosome replication. The goal of this project is to determine how two essential kinases, CckA and DivL, activate CtrA by phosphorylation only at the correct times during the cell cycle. The educational component of this project is a summer laboratory course for undergraduates in which each student will disrupt a previously unstudied Caulobacter gene and characterize the resulting mutant phenotype. Students will learn basic techniques in molecular biology and genetics while making original contributions in microbiology.