title: The RpoS sigma factor relieves H-NS-mediated transcriptional repression of csgA, the subunit gene of fibronectin-binding curli in Escherichia coli.
abstract: Curli encoded by the curlin subunit gene, csgA, are fibronectin- and laminin-binding fibres expressed by many natural Escherichia coli and E. coli K-12 strains in response to low temperature, low osmolarity and stationary-phase growth conditions. Curli expression is dependent on RpoS, a sigma factor that controls many stationary phase-inducible genes. Many commonly used K-12 strains carry an amber mutation in rpoS. Strains able to form curli carry an amber suppressor whereas curli-negative E. coli K-12 strains, in general, are sup0. Introduction of SupD, SupE, or supF suppressors into sup0 strains resulted in expression of temperature-regulated curli. In curli-deficient, RpoS- E. coli K-12 strains, csgA is transcriptionally activated by mutations in hns, which encodes the histone-like protein H-NS. Curli expression, fibronectin binding, and csgA transcription remain temperature- and osmoregulated in such double mutants. Our data suggest that RpoS+ strains, and hence curli-proficient strains of E. coli K-12, are relieved for the transcriptional repression mediated by the H-NS protein upon accumulating RpoS as cells reach stationary phase.
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110-1093.
authors.forename: A
authors.initials: A
authors.lastname: Olsén
authors.forename: A
authors.initials: A
authors.lastname: Arnqvist
authors.forename: M
authors.initials: M
authors.lastname: Hammar
authors.forename: S
authors.initials: S
authors.lastname: Sukupolvi
authors.forename: S
authors.initials: S
authors.lastname: Normark
mesh_terms: D000595:Amino Acid Sequence; D001422:Bacterial Adhesion / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000648:ultrastructure; D004927:Escherichia coli Infections / Q000235:genetics; D029968:Escherichia coli Proteins; D005353:Fibronectins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D014644:Genetic Variation; D007797:Laminin / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D012808:Sigma Factor / Q000378:metabolism; D013489:Suppression, Genetic; D014158:Transcription, Genetic; D014882:Water-Electrolyte Balance
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D005353:Fibronectins; C031908:H-NS protein, bacteria; D007797:Laminin; D012808:Sigma Factor; C489688:csgA protein, E coli; C069567:sigma factor KatF protein, Bacteria; C077481:Crl protein, Bacteria