Developmental Control of DNA Replication in Caulobacter

描述(申请人提供)：我们的目标是确定在细菌细胞周期的进程中控制DNA复制和染色体分离的信号和调节蛋白。新月芽孢杆菌具有明确的细胞周期，包括时间和空间受限的分化事件。这种细菌特别适合于分析染色体复制和分离的控制，因为培养物很容易同步，有明显的G1-S转变，在一个特定的细胞类型中每个细胞周期只发生一次复制，不对称分裂产生具有不同形态特征和复制能力的可分离后代。3767个基因的注释基因组序列已经完成，我们已经生成了用于全基因组转录网络分析的DNA微阵列。在Caulbacter中，双组分信号转导蛋白家族的成员在细胞周期控制的许多方面发挥着关键作用。除了作为复制启动的抑制因子外，CtrA反应调节因子还控制着553个基因中30%的表达，这些基因的表达受到细胞周期的控制。在G1-S转变过程中表达的与DNA复制有关的基因群不在CtrA控制的基因之列。我们现在将确定控制这些G1-S转换基因的关键调控因素。在另一种水平的调控中，复制的起点被限制在复制开始时复制体组装的细胞极点。我们将确定起源动态定位到细胞极点的机制，以及SMC[染色体结构维持]蛋白在染色体凝聚和分离中的作用。最后，我们已经证明，新复制的DNA保持在半甲基化状态，直到细胞周期结束。我们将确定染色体甲基化状态在细胞周期调控基因表达和染色体分离中的作用。

DESCRIPTION (provided by applicant): Our goal is to identify the signals and regulatory proteins that control DNA replication and chromosome segregation during the progression of a bacterial cell cycle. Caulobacter crescentus has a well-defined cell cycle which includes temporally and spatially constrained differentiation events. This bacterium is particularly well suited for an analysis of the control of chromosome replication and partition because cultures are easily synchronized and have a distinct G1-S transition, replication occurs in a specific cell type only once per cell cycle, and an asymmetric division yields separable progeny with different morphological features and replicative abilities. The annotated genome sequence of 3767 genes has been completed and we have generated DNA microarrays for the analysis of full genome transcription networks. In Caulobacter, members of the two-component signal transduction family of proteins play critical roles in many aspects of cell cycle control. In addition to serving as a repressor of replication initiation, the CtrA response regulator controls the expression of 30% of the 553 genes whose expression is under cell cycle control. Groups of genes involved in DNA replication that are expressed during the G1 -S transition are not among those controlled by CtrA. We will now identify the key regulatory factors that control these G1-S transition genes. At another level of regulation, the origin of replication is confined to the cell pole where the replisome assembles at the start of replication. We will determine the mechanisms by which the origin is dynamically localized to the cell pole, and the role of the SMC [Structural Maintenance of Chromosomes] protein in chromosome condensation and segregation. Finally, we have shown that newly replicated DNA remains in the hemi-methylated state until the end of the cell cycle. We will determine the role of the chromosome methylation state on cell cycle-regulated gene expression and chromosome segregation.