Chromosome Dynamics in Bacillus subtilis

项目摘要 这项提案的重点是了解细菌染色体动力学的基本性质： 细菌染色体在细胞周期和分化过程中的重构和分离？怎么样 染色体组织和分离与DNA复制有关？顺式作用的作用是什么 元素和反式作用因素在这些过程中牵连？错误分离的DNA是如何易位的 在胞质分裂后变成合适的女儿这些最基本的生物学问题已经被证明 部分由于功能冗余和缺乏定量测定，我们建议研究 在模式革兰氏阳性细菌枯草芽孢杆菌中染色体的组织和分离。的 在这种生物体中进行遗传、生物化学和细胞学分析的容易性使其成为一种 研究染色体动力学的理想系统。我们将使用下一代 我们已经开发了分子和细胞生物学工具以及定量分析来研究染色体 在孢子形成和营养细胞周期中。 作为一个概念和实验框架，细菌中染色体分离的过程可以 分为三个步骤。i）新复制的原点朝向细胞极点重新定位。（二）妹妹 染色体被重塑和分离，随后是细胞分裂。iii）存在于细胞中的未分离的DNA 在胞质分裂时，分裂平面穿过隔膜进入适当的子细胞。 这个动态过程在每个细胞周期中以极高的保真度执行。在本提案中，我们将 研究这三个步骤的分子基础我们建议： 1)确定染色体分配蛋白ParB如何与其同源的parS位点结合，募集SMC 冷凝复杂的起源，以及如何起源本地化SMC压实和组织 染色体 2)确定SpoIIIE易位酶如何在分裂到隔膜中运输未分离的DNA。 3)调查如何复制启动和起源分离后进入孢子形成链接。

PROJECT SUMMARY This proposal is focused on understanding fundamental properties of bacterial chromosome dynamics: How is the bacterial chromosome remodeled and segregated during the cell cycle and differentiation? How is chromosome organization and segregation linked to DNA replication? What are the roles of the cis-acting elements and trans-acting factors implicated in these processes? How is mis-segregated DNA translocated into the appropriate daughter after cytokinesis? These most basic biological questions have proven remarkably intractable, in part, due to functional redundancy and the lack of quantitative assays. We propose to study the organization and segregation of the chromosome in the model gram-positive bacterium Bacillus subtilis. The ease with which genetic, biochemical and cytological analysis can be carried out in this organism makes it an ideal system to study chromosome dynamics. We will address these questions using the next generation of molecular and cell biological tools and quantitative assays that we have developed to study the chromosome during spore-formation and the vegetative cell cycle. As a conceptual and experimental framework, the process of chromosome segregation in bacteria can be divided into three steps. i) The newly replicated origins are re-positioned towards the cell poles. ii) The sister chromosomes are remodeled and segregated followed by cell division. iii) Unsegregated DNA present at the division plane at the time of cytokinesis is translocated across the septum into the appropriate daughter cell. This dynamic process is executed in every cell cycle with extremely high fidelity. In this proposal we will investigate the molecular underpinnings of all three steps. We propose to: 1) Determine how the chromosomal partitioning protein ParB bound to its cognate parS sites recruits the SMC condensation complex to the origin and how origin-localized SMC compacts and organizes the chromosome. 2) Determine how the SpoIIIE translocase functions at the division to septum to transport unsegregated DNA. 3) Investigate how replication initiation and origin segregation are linked upon entry into sporulation.