title: Silencing of the Escherichia coli bgl operon by RpoS requires Crl.
abstract: Silencing of the Escherichia coli bgl operon is mediated by histone-like protein H-NS and affected by other pleiotropic regulators, including sigma factor RpoS. Silencing is relieved and the bgl operon is activated in hns mutants and by mutations that map in the vicinity of the bgl promoter. However, the expression level of activated bgl operon derivatives varies with the strain background. Here it is shown that the repression of the bgl operon by RpoS requires Crl. Crl is a protein that is necessary for the RpoS-dependent expression of the csgBA operon and that enhances the expression of other RpoS-dependent genes. In a Crl-negative strain RpoS had no effect on the bgl operon. The crl gene maps close to the proBA locus in the lac operon region and is deleted in many commonly used E. coli strains. Crl may therefore account for some of the observed strain-dependent variations of bgl operon expression levels and effects of pleiotropic regulators on bgl operon regulation.
authors.affiliation: Institut für Genetik, Universität zu Köln, Weyertal 121, 50931 Köln, Germany1.
authors.forename: Karin
authors.initials: K
authors.lastname: Schnetz
mesh_terms: D001426:Bacterial Proteins; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D020868:Gene Silencing; D017930:Genes, Reporter; D007763:Lac Operon; D009154:Mutation; D009876:Operon; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012808:Sigma Factor; D015534:Trans-Activators
chemical_list: D001426:Bacterial Proteins; C103411:BglJ protein, E coli; D029968:Escherichia coli Proteins; D012808:Sigma Factor; D015534:Trans-Activators; C489688:csgA protein, E coli; C069567:sigma factor KatF protein, Bacteria; C077481:Crl protein, Bacteria