title: DnaA-ATP acts as a molecular switch to control levels of ribonucleotide reductase expression in Escherichia coli.
abstract: Ribonucleotide reductase (RNR) is the bottleneck enzyme in the synthesis of dNTPs required for DNA replication. In order to avoid the mutagenic effects of imbalances in dNTPs the amount and activity of RNR enzyme in the cell is tightly regulated. RNR expression from the nrdAB operon is thus coupled to coincide with the initiation of DNA replication. However, the mechanism for the co-ordination of gene transcription and DNA replication remains to be elucidated. The timing and synchrony of DNA replication initiation in Escherichia coli is controlled in part by the binding of the DnaA protein to the origin of replication. DnaA is also a transcription factor of the nrdAB operon and could thus be the link between these two processes. Here we show that RNA polymerase can form a stable transcription initiation complex at the nrdAB promoter by direct interaction with the far upstream sites required for the timing of expression as a function of DNA replication. In addition, we show that the binding of DnaA on the promoter can either activate or repress transcription as a function of its concentration and its nucleotide-bound state. However, transcription regulation by DnaA does not significantly affect the timing of expression of RNR from the nrdAB operon.
authors.affiliation: LBPA, UMR 8113 du CNRS, ENS Cachan, 61 Avenue du Président Wilson, 94235 Cachan, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Olliver
authors.forename: Chiara
authors.initials: C
authors.lastname: Saggioro
authors.forename: John
authors.initials: J
authors.lastname: Herrick
authors.forename: Bianca
authors.initials: B
authors.lastname: Sclavi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D018983:DNA Footprinting; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis*; D015964:Gene Expression Regulation, Bacterial; D008954:Models, Biological; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012262:Ribonucleoside Diphosphate Reductase / Q000096:biosynthesis*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; D000255:Adenosine Triphosphate; C449642:NrdA protein, E coli; D012262:Ribonucleoside Diphosphate Reductase