title: VirS, an OmpR/PhoB subfamily response regulator, is required for activation of vapA gene expression in Rhodococcus equi.
abstract: BACKGROUND
  Rhodococcus equi is an important pulmonary pathogen in foals and in immunocompromised individuals. Virulent R. equi strains carry an 80-90 kb virulence plasmid that expresses the virulence-associated protein A (VapA). VapA expression is regulated by temperature and pH. The LysR-type transcriptional regulator, VirR, is involved in the regulation of the vapA gene. To examine the mechanism underlying transcriptional regulation of vapA, we characterized an R. equi mutant in which another putative transcriptional regulator encoded on the virulence plasmid, VirS, was deleted.
  
  
  RESULTS
  Deletion of virS reduced vapA promoter activity to non-inducible levels. Complementary expression of VirS in the virS deletion mutant restored transcription at the PvapA promoter, even under non-inducing conditions (30°C and pH 8.0). In addition, VirS expression increased PvapA promoter activity in the absence of functional VirR. Further, transcription of the icgA operon containing virS was regulated by pH and temperature in the same manner as vapA.
  
  
  CONCLUSIONS
  This study suggests that VirS is required for VapA expression and that regulation of PvapA-promoter activity may be achieved by controlling VirS expression levels.
authors.affiliation: Laboratory of Animal Hygiene, School of Veterinary Medicine, Kitasato University, Higashi 23-35-1, Towada 034-8628, Aomori, Japan. kakuda@vmas.kitasato-u.ac.jp.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kakuda
authors.forename: Takuya
authors.initials: T
authors.lastname: Hirota
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hagiuda
authors.forename: Shiko
authors.initials: S
authors.lastname: Miyazaki
authors.forename: Shinji
authors.initials: S
authors.lastname: Takai
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D010957:Plasmids; D011401:Promoter Regions, Genetic; D016929:Rhodococcus equi / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D014157:Transcription Factors; C541879:VapA protein, Rhodococcus equi