Journal article
Vfr Directly Activates exsA Transcription To Regulate Expression of the Pseudomonas aeruginosa Type III Secretion System
Journal of bacteriology, Vol.198(9), pp.1442-1450
05/2016
DOI: 10.1128/JB.00049-16
PMCID: PMC4836234
PMID: 26929300
Abstract
The Pseudomonas aeruginosa cyclic AMP (cAMP)-Vfr system (CVS) is a global regulator of virulence gene expression. Regulatory targets include type IV pili, secreted proteases, and the type III secretion system (T3SS). The mechanism by which CVS regulates T3SS gene expression remains undefined. Single-cell expression studies previously found that only a portion of the cells within a population express the T3SS under inducing conditions, a property known as bistability. We now report that bistability is altered in avfr mutant, wherein a substantially smaller fraction of the cells express the T3SS relative to the parental strain. Since bistability usually involves positive-feedback loops, we tested the hypothesis that virulence factor regulator (Vfr) regulates the expression of exsA ExsA is the central regulator of T3SS gene expression and autoregulates its own expression. Although exsA is the last gene of the exsCEBA polycistronic mRNA, we demonstrate that Vfr directly activates exsA transcription from a second promoter (PexsA) located immediately upstream of exsA PexsA promoter activity is entirely Vfr dependent. Direct binding of Vfr to a PexsA promoter probe was demonstrated by electrophoretic mobility shift assays, and DNase I footprinting revealed an area of protection that coincides with a putative Vfr consensus-binding site. Mutagenesis of that site disrupted Vfr binding and PexsA promoter activity. We conclude that Vfr contributes to T3SS gene expression through activation of the PexsA promoter, which is internal to the previously characterized exsCEBA operon.
Vfr is a cAMP-dependent DNA-binding protein that functions as a global regulator of virulence gene expression in Pseudomonas aeruginosa Regulation by Vfr allows for the coordinate production of related virulence functions, such as type IV pili and type III secretion, required for adherence to and intoxication of host cells, respectively. Although the molecular mechanism of Vfr regulation has been defined for many target genes, a direct link between Vfr and T3SS gene expression had not been established. In the present study, we report that Vfr directly controls exsA transcription, the master regulator of T3SS gene expression, from a newly identified promoter located immediately upstream of exsA.
Details
- Title: Subtitle
- Vfr Directly Activates exsA Transcription To Regulate Expression of the Pseudomonas aeruginosa Type III Secretion System
- Creators
- Anne E Marsden - Department of Microbiology, University of Iowa, Iowa City, Iowa, USAPeter J Intile - Department of Microbiology, University of Iowa, Iowa City, Iowa, USAKayley H Schulmeyer - Department of Microbiology, University of Iowa, Iowa City, Iowa, USAEthan R Simmons-Patterson - Department of Microbiology, University of Iowa, Iowa City, Iowa, USAMark L Urbanowski - Department of Microbiology, University of Iowa, Iowa City, Iowa, USAMatthew C Wolfgang - Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina, USATimothy L Yahr - Department of Microbiology, University of Iowa, Iowa City, Iowa, USA tim-yahr@uiowa.edu
- Resource Type
- Journal article
- Publication Details
- Journal of bacteriology, Vol.198(9), pp.1442-1450
- Publisher
- United States
- DOI
- 10.1128/JB.00049-16
- PMID
- 26929300
- PMCID
- PMC4836234
- ISSN
- 0021-9193
- eISSN
- 1098-5530
- Grant note
- T32 AI007511 / NIAID NIH HHS T32 GM082729 / NIGMS NIH HHS R01 AI069116 / NIAID NIH HHS R01-AI069116 / NIAID NIH HHS R01-AI055042 / NIAID NIH HHS R01 AI055042 / NIAID NIH HHS T32 AI07511 / NIAID NIH HHS P30 DK054759 / NIDDK NIH HHS
- Language
- English
- Date published
- 05/2016
- Academic Unit
- Microbiology and Immunology
- Record Identifier
- 9984002396702771
Metrics
19 Record Views