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Suppressors of DnaA ATP imposed overinitiation in Escherichia coli
Author(s) -
Charbon Godefroid,
Riber Leise,
Cohen Malene,
Skovgaard Ole,
Fujimitsu Kazuyuki,
Katayama Tsutomu,
LøbnerOlesen Anders
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07493.x
Subject(s) - dnaa , biology , escherichia coli , mutation , genetics , gene , microbiology and biotechnology , dna replication , origin of replication
Summary 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.