title: The histone-like nucleoid structuring protein H-NS represses the Escherichia coli bgl operon downstream of the promoter.
abstract: Specificity of repression by the histone-like nucleoid structuring protein and pleiotropic regulator, H-NS, is exceptionally high in case of the Escherichia coli bgl (beta-glucoside) operon. Here we present evidence that H-NS represses the operon at two levels. The binding of H-NS to an upstream silencer results in an approximately threefold repression of the catabolite gene regulator protein (CRP) dependent bgl promoter. In addition, H-NS binds to a silencer region located approximately 600-700 base pairs downstream of the promoter, within the coding region of first gene, bglG, resulting in a approximately sevenfold further decrease of expression. Repression by H-NS at the downstream silencer requires termination factor Rho and is reduced by translation of the bglG mRNA, but is independent of the promoter. This suggests that H-NS induces polarity of transcription by acting as a roadblock to the elongating RNA polymerase. The control of the bgl operon by H-NS at two levels results in a highly specific repression.
authors.affiliation: Institute for Genetics, University Cologne,Weyertal 121, 50931 Cologne, Germany.
authors.forename: Sudhanshu
authors.initials: S
authors.lastname: Dole
authors.forename: V
authors.initials: V
authors.lastname: Nagarajavel
authors.forename: Karin
authors.initials: K
authors.lastname: Schnetz
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005960:Glucosides / Q000235:genetics* / Q000378:metabolism; D008957:Models, Genetic; D009876:Operon; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D005960:Glucosides; C031908:H-NS protein, bacteria