sigma factor selectivity of Escherichia coli RNA polymerase: role for CRP, IHF and lrp transcription factors.
osmY is a stationary phase-induced and osmotically regulated gene in Escherichia coli that requires the stationary phase RNA polymerase (Esigma(S)) for in vivo expression. We show here that the major RNA polymerase, Esigma(70), also transcribes osmY in vitro and, depending on genetic background, even in vivo. The cAMP receptor protein (CRP) bound to cAMP, the leucine-responsive regulatory protein (Lrp) and the integration host factor (IHF) inhibit transcription initiation at the osmY promoter. The binding site for CRP is centred at -12.5 from the transcription start site, whereas Lrp covers the whole promoter region. The site for IHF maps in the -90 region. By mobility shift assay, permanganate reactivity and in vitro transcription experiments, we show that repression is much stronger with Esigma(70) than with Esigma(S) holoenzyme. We conclude that CRP, Lrp and IHF inhibit open complex formation more efficiently with Esigma(70) than with Esigma(S). This different ability of the two holoenzymes to interact productively with promoters once assembled in complex nucleoprotein structures may be a crucial factor in generating sigma(S) selectivity in vivo.
Colland
F
F
Institut Pasteur, Unité de Physicochimie des Macromolécules Biologiques (URA 1773 du CNRS), 75724 Paris, Cedex 15, France.
Barth
M
M
Hengge-Aronis
R
R
Kolb
A
A
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics*; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D034982:Integration Host Factors; D051756:Leucine-Responsive Regulatory Protein; D008969:Molecular Sequence Data; D033902:Periplasmic Binding Proteins; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012808:Sigma Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D034982:Integration Host Factors; C497278:Lrp protein, E coli; D033902:Periplasmic Binding Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C069567:sigma factor KatF protein, Bacteria; D051756:Leucine-Responsive Regulatory Protein; C074783:osmY protein, E coli; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases