Regulation of initiation of replication in bacteria

点击翻译按钮获取中文摘要

All cells must ensure that initiation of replication occurs only once per cell cycle, and that it is tightly linked to the physiological state of the cell. Alterations in initiation control lead to slow growth, cell death and to carcinogenesis. In all bacteria investigated so far, the highly conserved protein DnaA controls initiation of replication. DnaA is a sequence specific DNA-binding ATPase that is homologous to eukaryotic Orc proteins, which are also crucial for initiation control. Understanding of what triggers DnaA to unwind origin regions and load the replication machinery is a key question in biology, yet unresolved. We have recently been able to visualize GFP-DnaA and to follow its binding to replication origins and to the replisome in live cells. We have found a novel mechanism for replication control: after initiation of replication, DnaA is tethered to the replisome via YabA, and is spatially sequestered from the origins that are moved away from the replisome, thus preventing reinitiation. We will now address the question of what regulates DnaA activity at origin regions: a) analysis of the localization and effect of mutant forms of GFP-DnaA, b) effect of a novel regulator, Soj, on DnaA in vivo and in vitro, c) the identification of novel DnaA binding partners, and d) a suppressor screen for the bypass of a dominant negative dnaA allele.