title: LeuO antagonizes H-NS and StpA-dependent repression in Salmonella enterica ompS1.
abstract: The ompS1 gene encodes a quiescent porin in Salmonella enterica. We analysed the effects of H-NS and StpA, a paralogue of H-NS, on ompS1 expression. In an hns single mutant expression was derepressed but did not reach the maximum level. Expression in an stpA single mutant showed the same low repressed level as the wild type. In contrast, in an hns stpA background, OmpS1 became abundant in the outer membrane. The expression of ompS1 was positively regulated by LeuO, a LysR-type quiescent regulator that has been involved in pathogenesis. Upon induction of the cloned leuO gene into the wild type, ompS1 was completely derepressed and the OmpS1 porin was detected in the outer membrane. LeuO activated the P1 promoter in an OmpR-dependent manner and P2 in the absence of OmpR. LeuO bound upstream of the regulatory region of ompS1 overlapping with one nucleation site of H-NS and StpA. Our results are thus consistent with a model where H-NS binds at a nucleation site and LeuO displaces H-NS and StpA.
authors: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62260 México.
authors: Miguel Angel
authors: MA
authors: De la Cruz
authors: Marcos
authors: M
authors: Fernández-Mora
authors: Carmen
authors: C
authors: Guadarrama
authors: Mario Alberto
authors: MA
authors: Flores-Valdez
authors: Víctor H
authors: VH
authors: Bustamante
authors: Alejandra
authors: A
authors: Vázquez
authors: Edmundo
authors: E
authors: Calva
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D018983:DNA Footprinting / Q000379:methods; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D008954:Models, Biological; D009154:Mutation; D018272:Porins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D019779:Salmonella enterica / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D018272:Porins; D003850:Deoxyribonuclease I