title: Virulence regulator AphB enhances toxR transcription in Vibrio cholerae.
abstract: BACKGROUND
  Vibrio cholerae is the causative agent of cholera. Extensive studies reveal that complicated regulatory cascades regulate expression of virulence genes, the products of which are required for V. cholerae to colonize and cause disease. In this study, we investigated the expression of the key virulence regulator ToxR under different conditions.
  
  
  RESULTS
  We found that compared to that of wild type grown to stationary phase, the toxR expression was lower in an aphB mutant strain. AphB has been previously shown to be a key virulence regulator that is required to activate the expression of tcpP. When expressed constitutively, AphB is able to activate the toxR promoter. Furthermore, gel shift analysis indicates that AphB binds toxR promoter region directly. We also characterize the effect of AphB on the levels of the outer membrane porins OmpT and OmpU, which are known to be regulated by ToxR.
  
  
  CONCLUSIONS
  Our data indicate that V. cholerae possesses an additional regulatory loop that use AphB to activate the expression of two virulence regulators, ToxR and TcpP, which together control the expression of the master virulence regulator ToxT.
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Beijing, PR China. allenxu426@hotmail.com
authors.forename: Xiao
authors.initials: X
authors.lastname: Xu
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Stern
authors.forename: Zhi
authors.initials: Z
authors.lastname: Liu
authors.forename: Biao
authors.initials: B
authors.lastname: Kan
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014734:Vibrio cholerae / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D014774:Virulence
chemical_list: C120327:AphB protein, Vibrio cholerae; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C097244:TCPP protein, Vibrio cholerae; D015534:Trans-Activators; D014157:Transcription Factors; C499324:toxR protein, Vibrio cholerae