Investigation of chromosome dynamics in bacteria

与含有分裂染色体的有丝分裂机制的真核细胞相比，原核生物如何将它们的DNA分离成未来的子细胞尚不清楚。在染色体凝聚和分离的关键球员是SMC蛋白。我们已经证明，与真核细胞一样，SMC对于B中的染色体分离是必需的。枯草杆菌。我们已经确定了两种蛋白质，ScpA和ScpB是保守的原核生物，并与SMC形成三元复合物。荧光显微镜显示SMC复合物以动态细胞周期依赖性方式定位，并且主要存在于靠近细胞极的特定位点内。额外的数据表明，从这些网站的SMC复合物积极拉向相反的细胞两极的姐妹染色体。我们已经纯化了所有3种蛋白质和SMC的不同部分，并表明ScpA和ScpB与SMC头部结构域结合，而SMC以环状结构包含DNA，这提出了一种新的DNA缩合机制，需要进一步阐明。我们还发现，修复DNA双链断裂所需的几种蛋白质在损伤诱导后动态地和瞬时地被募集到DNA上的特定位点，但以不同的方式。进一步的分析将提供关于其功能和相互依存性的详细见解。

In contrast to eukaryotic cells that contain a mitotic machinery to separate chromosomes it is unclear how prokaryotes segregate their DNA into future daughter cells. Key players in chromosome condensation and segregation are SMC proteins. We have shown that likewise to eukaryotic cells SMC is essential for chromosome segregation in B. subtilis. We have identified two proteins, ScpA and ScpB that are conserved in prokaryotes and that form a ternary complex with SMC. Fluorescence microscopy has shown that the SMC complex localizes in a dynamic cell cycle dependent manner and is mostly present within specific sites close to the cell poles. Additional data suggest that from these sites the SMC complex actively pulls the sister chromosomes towards opposite cell poles. We have purified all 3 proteins and distinct parts of SMC and have shown that ScpA and ScpB bind to the SMC head domains, while SMC embraces DNA as a ring-like structure, which presents a novel DNA condensation mechanism that needs to be further elucidated. We have also found that several proteins required for repair of DNA double strand breaks are dynamically and transiently recruited to specific sites on the DNA after damage induction but in a differential fashion. Further analysis will provide detailed insight in their function and interdependence.