title: Regulatory elements involved in the expression of competence genes in naturally transformable Vibrio cholerae.
abstract: BACKGROUND
  The human pathogen Vibrio cholerae normally enters the developmental program of natural competence for transformation after colonizing chitinous surfaces. Natural competence is regulated by at least three pathways in this organism: chitin sensing/degradation, quorum sensing and carbon catabolite repression (CCR). The cyclic adenosine monophosphate (cAMP) receptor protein CRP, which is the global regulator of CCR, binds to regulatory DNA elements called CRP sites when in complex with cAMP. Previous studies in Haemophilus influenzae suggested that the CRP protein binds competence-specific CRP-S sites under competence-inducing conditions, most likely in concert with the master regulator of transformation Sxy/TfoX.
  
  
  RESULTS
  In this study, we investigated the regulation of the competence genes qstR and comEA as an example of the complex process that controls competence gene activation in V. cholerae. We identified previously unrecognized putative CRP-S sites upstream of both genes. Deletion of these motifs significantly impaired natural transformability. Moreover, site-directed mutagenesis of these sites resulted in altered gene expression. This altered gene expression also correlated directly with protein levels, bacterial capacity for DNA uptake, and natural transformability.
  
  
  CONCLUSIONS
  Based on the data provided in this study we suggest that the identified sites are important for the expression of the competence genes qstR and comEA and therefore for natural transformability of V. cholerae even though the motifs might not reflect bona fide CRP-S sites.
authors.forename: Mirella
authors.initials: M
authors.lastname: Lo Scrudato
authors.forename: Sandrine
authors.initials: S
authors.lastname: Borgeaud
authors.forename: Melanie
authors.initials: M
authors.lastname: Blokesch
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D057465:Catabolite Repression / Q000235:genetics; D002686:Chitin / Q000378:metabolism; D000242:Cyclic AMP / Q000235:genetics; D002373:Cyclic AMP Receptor Protein / Q000235:genetics; D061269:DNA Transformation Competence / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D016297:Mutagenesis, Site-Directed / Q000379:methods; D053038:Quorum Sensing / Q000235:genetics; D050436:Regulatory Elements, Transcriptional / Q000235:genetics*; D014169:Transformation, Bacterial / Q000235:genetics*; D014734:Vibrio cholerae / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D002686:Chitin; D000242:Cyclic AMP