Promoter domain mediates guanosine tetraphosphate activation of the histidine operon.
We have analyzed the effects of the "alarmone" guanosine 5'-diphosphate 3'-diphosphate (ppGpp) on regulation of the Salmonella typhimurium histidine operon in vitro. Expression of the wild-type promoter, measured in a DNA-dependent transcription-translation system, was strongly dependent on ppGpp; addition of ppGpp stimulated his expression 22-fold with plasmid DNA templates. Oligonucleotide-directed, site-specific mutations that increase the homology of the -10 hexamer to the consensus sequence of the E sigma 70 promoters dramatically increased his expression in the absence of ppGpp and reduced the stimulation to less than a factor of 2. A deletion mutation that alters the sequence between the -10 hexamer and the start point of transcription, generated by BAL-31 nuclease, affected ppGpp regulation in a similar manner. We propose that the -10 hexamer sequence and the adjacent downstream region are both important in regulating transcription by ppGpp. Mechanisms to account for activation and repression of transcription by ppGpp are discussed.
D004269:DNA, Bacterial / Q000235:genetics; D004278:DNA, Superhelical / Q000235:genetics; D005786:Gene Expression Regulation; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006159:Guanosine Tetraphosphate / Q000494:pharmacology*; D006639:Histidine / Q000235:genetics*; D009876:Operon; D011401:Promoter Regions, Genetic; D012486:Salmonella typhimurium / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects
D004269:DNA, Bacterial; D004278:DNA, Superhelical; D006150:Guanine Nucleotides; D006159:Guanosine Tetraphosphate; D006639:Histidine