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

新月柄杆菌（Caulobacter crescentus）存在两种不同的细胞类型，运动的游动细胞和静止的柄细胞。每一次柄杆菌分裂，每种类型的一个细胞产生，在一个过程中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，群集细胞必须首先分化成可以启动染色体复制的有柄细胞。不对称的细胞分裂和一种细胞类型分化成另一种细胞类型是所有高等生物发育的基本过程，柄杆菌提供了一个相对简单的模型系统来详细研究它们。称为双组分蛋白质的信号转导蛋白质网络协调复杂的柄杆菌生命周期。Ryan实验室的研究重点是CtrA，这是一种双组分蛋白质，通过影响多个基因的转录来调节细胞周期。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必须是无活性的，因为它也阻断了染色体复制的起始。该项目的目标是确定两种必需激酶CckA和DivL如何仅在细胞周期的正确时间通过磷酸化激活CtrA。该项目的教育部分是本科生的暑期实验室课程，每个学生将破坏以前未研究的柄杆菌基因，并表征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.