title: Listeria monocytogenes sigmaB modulates PrfA-mediated virulence factor expression.
abstract: Listeria monocytogenes sigma(B) and positive regulatory factor A (PrfA) are pleiotropic transcriptional regulators that coregulate a subset of virulence genes. A positive regulatory role for sigma(B) in prfA transcription has been well established; therefore, observations of increased virulence gene expression and hemolytic activity in a DeltasigB strain initially appeared paradoxical. To test the hypothesis that L. monocytogenes sigma(B) contributes to a regulatory network critical for appropriate repression as well as induction of virulence gene expression, genome-wide transcript profiling and follow-up quantitative reverse transcriptase PCR (qRT-PCR), reporter fusion, and phenotypic experiments were conducted using L. monocytogenes prfA*, prfA* DeltasigB, DeltaprfA, and DeltaprfA DeltasigB strains. Genome-wide transcript profiling and qRT-PCR showed that in the presence of active PrfA (PrfA*), sigma(B) is responsible for reduced expression of the PrfA regulon. sigma(B)-dependent modulation of PrfA regulon expression reduced the cytotoxic effects of a PrfA* strain in HepG2 cells, highlighting the functional importance of regulatory interactions between PrfA and sigma(B). The emerging model of the role of sigma(B) in regulating overall PrfA activity includes a switch from transcriptional activation at the P2(prfA) promoter (e.g., in extracellular bacteria when PrfA activity is low) to posttranscriptional downregulation of PrfA regulon expression (e.g., in intracellular bacteria when PrfA activity is high).
authors.affiliation: Department of Food Science, Cornell University, 405 Stocking Hall, Ithaca, NY 14853, USA. tmb224@cornell.edu
authors.forename: Juliane
authors.initials: J
authors.lastname: Ollinger
authors.forename: Barbara
authors.initials: B
authors.lastname: Bowen
authors.forename: Martin
authors.initials: M
authors.lastname: Wiedmann
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Boor
authors.forename: Teresa M
authors.initials: TM
authors.lastname: Bergholz
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D017353:Gene Deletion; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000382:microbiology; D006801:Humans; D008089:Listeria monocytogenes / Q000235:genetics / Q000472:pathogenicity*; D008954:Models, Biological; D010454:Peptide Termination Factors / Q000502:physiology*; D018085:Regulon; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*; D014774:Virulence; D037521:Virulence Factors / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D010454:Peptide Termination Factors; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D037521:Virulence Factors