title: Hda-mediated inactivation of the DnaA protein and dnaA gene autoregulation act in concert to ensure homeostatic maintenance of the Escherichia coli chromosome.
abstract: Initiation of DNA replication in Eschericia coli requires the ATP-bound form of the DnaA protein. The conversion of DnaA-ATP to DnaA-ADP is facilitated by a complex of DnaA, Hda (homologous to DnaA), and DNA-loaded beta-clamp proteins in a process termed RIDA (regulatory inactivation of DnaA). Hda-deficient cells initiate replication at each origin mainly once per cell cycle, and the rare reinitiation events never coincide with the end of the origin sequestration period. Therefore, RIDA is not the predominant mechanism to prevent immediate reinitiation from oriC. The cellular level of Hda correlated directly with dnaA gene expression such that Hda deficiency led to reduced dnaA gene expression, and overproduction of Hda led to DnaA overproduction. Hda-deficient cells were very sensitive to variations in the cellular level of DnaA, and DnaA overproduction led to uncontrolled initiation of replication from oriC, causing severe growth retardation or cell death. Based on these observations, we propose that both RIDA and dnaA gene autoregulation are required as homeostatic mechanisms to ensure that initiation of replication occurs at the same time relative to cell mass in each cell cycle.
authors.affiliation: Department of Life Sciences and Chemistry, Roskilde University, Denmark.
authors.forename: Leise
authors.initials: L
authors.lastname: Riber
authors.forename: Jan A
authors.initials: JA
authors.lastname: Olsson
authors.forename: Rasmus B
authors.initials: RB
authors.lastname: Jensen
authors.forename: Ole
authors.initials: O
authors.lastname: Skovgaard
authors.forename: Santanu
authors.initials: S
authors.lastname: Dasgupta
authors.forename: Martin G
authors.initials: MG
authors.lastname: Marinus
authors.forename: Anders
authors.initials: A
authors.lastname: Løbner-Olesen
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death; D002876:Chromosomes, Bacterial; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006706:Homeostasis; D018741:Replication Origin; D015534:Trans-Activators
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; D015534:Trans-Activators; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C435211:Hda protein, E coli