title: Bordetella pertussis risA, but not risS, is required for maximal expression of Bvg-repressed genes.
abstract: Expression of virulence determinants by Bordetella pertussis, the primary etiological agent of whooping cough, is regulated by the BvgAS two-component regulatory system. The role of a second two-component regulatory system, encoded by risAS, in this process is not defined. Here, we show that mutation of B. pertussis risA does not affect Bvg-activated genes or proteins. However, mutation of risA resulted in greatly diminished expression of Bvg-repressed antigens and decreased transcription of Bvg-repressed genes. In contrast, mutation of risS had no effect on the expression of Bvg-regulated molecules. Mutation of risA also resulted in decreased bacterial invasion in a HeLa cell model. However, decreased invasion could not be attributed to the decreased expression of Bvg-repressed products, suggesting that mutation of risA may affect the expression of a variety of genes. Unlike the risAS operons in B. parapertussis and B. bronchiseptica, B. pertussis risS is a pseudogene that encodes a truncated RisS sensor. Deletion of the intact part of the B. pertussis risS gene does not affect the expression of risA-dependent, Bvg-repressed genes. These observations suggest that RisA activation occurs through cross-regulation by a heterologous system.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Alberta, 1-69 Medical Sciences Bldg., Edmonton, Alberta T6G 2H7, Canada. trevor.stenson@ualberta.ca
authors.forename: Trevor H
authors.initials: TH
authors.lastname: Stenson
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Allen
authors.forename: Jehan A
authors.initials: JA
authors.lastname: Al-Meer
authors.forename: Duncan
authors.initials: D
authors.lastname: Maskell
authors.forename: Mark S
authors.initials: MS
authors.lastname: Peppler
mesh_terms: D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001886:Bordetella pertussis / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D009097:Multienzyme Complexes / Q000235:genetics; D009876:Operon; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D012097:Repressor Proteins / Q000502:physiology*; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C069776:BvgB protein, Bordetella pertussis; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; C114918:RisA protein, Bordetella; D014157:Transcription Factors; C080662:bvgS protein, Bordetella pertussis; C057843:envZ protein, E coli