Sigma S-dependent growth-phase induction of the csgBA promoter in Escherichia coli can be achieved in vivo by sigma 70 in the absence of the nucleoid-associated protein H-NS.
The stationary-phase-specific sigma factor sigma S (RpoS/KatF) is required for Escherichia coli to induce expression of fibronectin-binding curli organelles upon reaching stationary phase. We show that the csgA gene which encodes the curlin subunit protein belongs to a dicistronic operon, csgBA. The transcriptional start site of csgBA was determined and an AT-rich up-stream activating sequence (UAS) required for transcriptional activation was identified. The pcsgBA promoter is not specific for sigma S since the same promoter sequence can be used by E sigma 70 in vivo in a strain lacking nucleoid-associated protein H-NS and sigma S. Transcription remained growth-phase induced and dependent upon the UAS in such a double mutant. Furthermore, we demonstrate that an additional operon, hdeAB, which is also dependent upon sigma S for transcription, can be transcribed by E sigma 70 in vivo in the absence of H-NS by utilizing the phdeAB promoter. Two other genes known to be under the control of sigma S for expression, bolA and katE, remained transcriptionally silent in the absence of H-NS. It is suggested that a subset of E. coli promoters can be recognized by both E sigma S and E sigma 70 in vivo but H-NS interacting with these sequences prevents formation of successful transcription-initiation complexes with E sigma 70.
Arnqvist
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A
Department of Microbiology, Umeå University, Sweden.
Olsén
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A
Normark
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S
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000502:physiology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D001483:Base Sequence; D002374:Catalase / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000502:physiology*; D012321:DNA-Directed RNA Polymerases / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000502:physiology*
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D012808:Sigma Factor; C489688:csgA protein, E coli; C084501:hdeA protein, E coli; C084502:hdeB protein, E coli; C069567:sigma factor KatF protein, Bacteria; C077481:Crl protein, Bacteria; D002374:Catalase; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases