Titration of DnaA protein by oriC DnaA-boxes increases dnaA gene expression in Escherichia coli.
Binding of the DnaA protein to its binding sites, the DnaA-boxes (TTATCCACA), was measured by a simple physiological approach. The presence of extra DnaA-boxes in growing cells leads to a derepression of dnaA gene expression, measured as beta-galactosidase activity of a dnaA-lacZ fusion polypeptide. Different DnaA-boxes caused different degrees of derepression indicating that the DnaA protein requires sequences in addition to the DnaA-box for efficient binding. The DnaA-boxes in oriC might act cooperatively in binding of the DnaA protein. The derepressed levels of DnaA protein obtained in a strain carrying an oriC+-pBR322 chimera were very high and sufficient to activate oriC on the chimeric plasmid, which was maintained at a copy number more than three times that of pBR322.
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D005796:Genes; D005798:Genes, Bacterial; D010957:Plasmids; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
D001426:Bacterial Proteins