title: Suppressors of DnaA(ATP) imposed overinitiation in Escherichia coli.
abstract: Chromosome replication in Escherichia coli is limited by the supply of DnaA associated with ATP. Cells deficient in RIDA (Regulatory Inactivation of DnaA) due to a deletion of the hda gene accumulate suppressor mutations (hsm) to counteract the overinitiation caused by an elevated DnaA(ATP) level. Eight spontaneous hda suppressor mutations were identified by whole-genome sequencing, and three of these were analysed further. Two mutations (hsm-2 and hsm-4) mapped in the dnaA gene and led to a reduced ability to initiate replication from oriC. One mutation (hsm-1) mapped to the seqA promoter and increased the SeqA protein level in the cell. hsm-1 cells had prolonged origin sequestration, reduced DnaA protein level and reduced DnaA-Reactivating Sequence (DARS)-mediated rejuvenation of DnaA(ADP) to DnaA(ATP) , all of which could contribute to the suppression of RIDA deficiency. Despite of these defects hsm-1 cells were quite similar to wild type with respect to cell cycle parameters. We speculate that since SeqA binding sites might overlap with DnaA binding sites spread throughout the chromosome, excess SeqA could interfere with DnaA titration and thereby increase free DnaA level. Thus, in spite of reduction in total DnaA, the amount of DnaA molecules available for initiation may not be reduced.
authors.affiliation: Department of Science, Systems and Models, Roskilde University, Building 18.1, 4000 Roskilde, Denmark.
authors.forename: Godefroid
authors.initials: G
authors.lastname: Charbon
authors.forename: Leise
authors.initials: L
authors.lastname: Riber
authors.forename: Malene
authors.initials: M
authors.lastname: Cohen
authors.forename: Ole
authors.initials: O
authors.lastname: Skovgaard
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Fujimitsu
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Katayama
authors.forename: Anders
authors.initials: A
authors.lastname: Løbner-Olesen
mesh_terms: D000244:Adenosine Diphosphate / Q000032:analysis; D000255:Adenosine Triphosphate / Q000032:analysis; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002876:Chromosomes, Bacterial; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D013489:Suppression, Genetic
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; C089746:SeqA protein, E coli; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate