title: Regulation of the fimB promoter: a case of differential regulation by ppGpp and DksA in vivo.
abstract: The expression of type 1 fimbriae is dependent on the intracellular levels of ppGpp through stimulation of fimB transcription. Here we show that in contrast to the previously described decreased fimbriation observed in a ppGpp-deficient strain, DksA deficiency results in a hyperfimbriated state. In vivo assays show that the effect of DksA deficiency on the type 1 fimbriae occurs at the phase variation level because of elevated transcription from the fimB P2 promoter. In contrast, our in vitro transcription studies demonstrate that ppGpp and DksA can stimulate transcription from the fimB P2 promoter both independently and codependently. We provide evidences that the apparently contradictory results from the in vivo and in vitro transcriptional studies are at least in part a consequence of the increased association of the anti-pausing factors (GreA and GreB) to the RNA polymerase in the absence of DksA in vivo.
authors.affiliation: Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Aberg
authors.forename: Victoria
authors.initials: V
authors.lastname: Shingler
authors.forename: Carlos
authors.initials: C
authors.lastname: Balsalobre
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006159:Guanosine Tetraphosphate / Q000378:metabolism; D019426:Integrases / Q000235:genetics*; D008954:Models, Biological; D008957:Models, Genetic; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics; D012808:Sigma Factor / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C079668:GreA protein, E coli; C079667:GreB protein, E coli; C031908:H-NS protein, bacteria; C106638:HisG protein, bacteria; D009004:Monosaccharide Transport Proteins; C477082:NanR protein, E coli; D012097:Repressor Proteins; D012808:Sigma Factor; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; C090751:dksA protein, E coli; C081956:fimB protein, E coli; C067862:nagC protein, E coli; C069567:sigma factor KatF protein, Bacteria; D006159:Guanosine Tetraphosphate; D019426:Integrases