The alarmone (p)ppGpp mediates physiological-responsive control at the sigma 54-dependent Po promoter.
Transcription from the Pseudomonas-derived sigma 54-dependent Po promoter of the dmp operon is mediated by the aromatic-responsive regulator DmpR. However, physiological control is superimposed on this regulatory system causing silencing of the DmpR-mediated transcriptional response in rich media until the transition between exponential and stationary phase is reached. Here, the positive role of the nutritional alarmone (p)ppGpp in DmpR regulation of the Po promoter has been identified and investigated in vivo. Overproduction of (p)ppGpp in a Pseudomonas reporter system was found to allow an immediate transcriptional response under normally non-permissive conditions. Conversely (p)ppGpp-deficient Escherichia coli strains were found to be severely defective in DmpR-mediated transcription, demonstrating the requirement for this metabolic signal. A subset of mutations in the beta, beta' and sigma 70 subunits of RNA polymerase, which confer prototrophy on ppGpp0 E. coli, was also found to restore specific DmpR-mediated transcription from Po, suggesting that the metabolic signal is mediated directly through the sigma 54-RNA polymerase. These data provide a direct mechanistic link between the physiological status of the cell and expression from sigma 54 promoters.
Sze
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Department of Cell and Molecular Biology, Umeå University, Sweden.
Shingler
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D001426:Bacterial Proteins / Q000378:metabolism; D015153:Blotting, Western; D003470:Culture Media; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D006158:Guanosine Pentaphosphate / Q000378:metabolism*; D006159:Guanosine Tetraphosphate / Q000378:metabolism*; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011549:Pseudomonas / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000235:genetics*; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D003470:Culture Media; D004268:DNA-Binding Proteins; C080133:DmpR protein, Pseudomonas; D029968:Escherichia coli Proteins; D012808:Sigma Factor; D015534:Trans-Activators; C497751:rpoN protein, E coli; D006159:Guanosine Tetraphosphate; D006158:Guanosine Pentaphosphate; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54