scholarly journals Integration Host Factor Positively Regulates Virulence Gene Expression in Vibrio cholerae

2008 ◽  
Vol 190 (13) ◽  
pp. 4736-4748 ◽  
Author(s):  
Emily Stonehouse ◽  
Gabriela Kovacikova ◽  
Ronald K. Taylor ◽  
Karen Skorupski
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Gene ◽  
Toxin Production ◽  
Dnase I ◽  
Integration Host Factor ◽  
Host Factor ◽  
Mobility Shift ◽  
Virulence Gene Expression ◽  
Dnase I Footprinting

ABSTRACT Virulence gene expression in Vibrio cholerae is dependent upon a complex transcriptional cascade that is influenced by both specific and global regulators in response to environmental stimuli. Here, we report that the global regulator integration host factor (IHF) positively affects virulence gene expression in V. cholerae. Inactivation of ihfA and ihfB, the genes encoding the IHF subunits, decreased the expression levels of the two main virulence factors tcpA and ctx and prevented toxin-coregulated pilus and cholera toxin production. IHF was found to directly bind to and bend the tcpA promoter region at an IHF consensus site centered at position −162 by using gel mobility shift assays and DNase I footprinting experiments. Deletion or mutation of the tcpA IHF consensus site resulted in the loss of IHF binding and additionally disrupted the binding of the repressor H-NS. DNase I footprinting revealed that H-NS protection overlaps with both the IHF and the ToxT binding sites at the tcpA promoter. In addition, disruption of ihfA in an hns or toxT mutant background had no effect on tcpA expression. These results suggest that IHF may function at the tcpA promoter to alleviate H-NS repression.

scholarly journals Autoregulation and Virulence Control by the Toxin-Antitoxin System SavRS inStaphylococcus aureus

2018 ◽  
Vol 86 (5) ◽  
pp. e00032-18 ◽  
Author(s):  
Wen Wen ◽  
Banghui Liu ◽  
Lu Xue ◽  
Zhongliang Zhu ◽  
Liwen Niu ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Molecular Mechanisms ◽  
Cell Formation ◽  
Virulence Gene ◽  
Dnase I ◽  
Titration Calorimetry ◽  
Mobility Shift ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Dnase I Footprinting

ABSTRACTToxin-antitoxin (TA) systems play diverse physiological roles, such as plasmid maintenance, growth control, and persister cell formation, but their involvement in bacterial pathogenicity remains largely unknown. Here, we have identified a novel type II toxin-antitoxin system, SavRS, and revealed the molecular mechanisms of its autoregulation and virulence control inStaphylococcus aureus. Electrophoretic mobility shift assay and isothermal titration calorimetry data indicated that the antitoxin SavR acted as the primary repressor bound to its own promoter, while the toxin SavS formed a complex with SavR to enhance the ability to bind to the operator site. DNase I footprinting assay identified the SavRS-binding site containing a short and long palindrome in the promoter region. Further, mutation and DNase I footprinting assay demonstrated that the two palindromes were crucial for DNA binding and transcriptional repression. More interestingly, genetic deletion of thesavRSsystem led to the increased hemolytic activity and pathogenicity in a mouse subcutaneous abscess model. We further identified two virulence genes,hlaandefb, by real-time quantitative reverse transcription-PCR and demonstrated that SavR and SavRS could directly bind to their promoter regions to repress virulence gene expression.

scholarly journals TolC Affects Virulence Gene Expression in Vibrio cholerae

2011 ◽  
Vol 193 (20) ◽  
pp. 5850-5852 ◽  
Author(s):  
Y. Minato ◽  
R. L. Siefken ◽  
C. C. Hase
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Gene ◽  
Virulence Gene Expression

scholarly journals Regulatory Networks Controlling Vibrio cholerae Virulence Gene Expression

2007 ◽  
Vol 75 (12) ◽  
pp. 5542-5549 ◽  
Author(s):  
Jyl S. Matson ◽  
Jeffrey H. Withey ◽  
Victor J. DiRita
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Regulatory Networks ◽  
Virulence Gene ◽  
Virulence Gene Expression

scholarly journals TcpH Influences Virulence Gene Expression in Vibrio cholerae by Inhibiting Degradation of the Transcription Activator TcpP

2004 ◽  
Vol 186 (24) ◽  
pp. 8309-8316 ◽  
Author(s):  
Nancy A. Beck ◽  
Eric S. Krukonis ◽  
Victor J. DiRita
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Time Course ◽  
Virulence Gene ◽  
Degradation Pathway ◽  
Mrna Levels ◽  
Transcription Activator ◽  
Virulence Gene Expression ◽  
Protein Levels ◽  
Periplasmic Domain

ABSTRACT Expression of toxT, the transcription activator of cholera toxin and pilus production in Vibrio cholerae, is the consequence of a complex cascade of regulatory events that culminates in activation of the toxT promoter by TcpP and ToxR, two membrane-localized transcription factors. Both are encoded in operons with genes whose products, TcpH and ToxS, which are also membrane localized, are hypothesized to control their activity. In this study we analyzed the role of TcpH in controlling TcpP function. We show that a mutant of V. cholerae lacking TcpH expressed virtually undetectable levels of TcpP, although tcpP mRNA levels remain unaffected. A time course experiment showed that levels of TcpP, expressed from a plasmid, are dramatically reduced over time without co-overexpression of TcpH. By contrast, deletion of toxS did not affect ToxR protein levels. A fusion protein in which the TcpP periplasmic domain is replaced with that of ToxR remains stable, suggesting that the periplasmic domain of TcpP is the target for degradation of the protein. Placement of the periplasmic domain of TcpP on ToxR, an otherwise stable protein, results in instability, providing further evidence for the hypothesis that the periplasmic domain of TcpP is a target for degradation. Consistent with this interpretation is our finding that derivatives of TcpP lacking a periplasmic domain are more stable in V. cholerae than are derivatives in which the periplasmic domain has been truncated. This work identifies at least one role for the periplasmic domain of TcpP, i.e., to act as a target for a protein degradation pathway that regulates TcpP levels. It also provides a rationale for why the V. cholerae tcpH mutant strain is avirulent. We hypothesize that regulator degradation may be an important mechanism for regulating virulence gene expression in V. cholerae.

scholarly journals A Genome-Wide Screen Reveals that the Vibrio cholerae Phosphoenolpyruvate Phosphotransferase System Modulates Virulence Gene Expression

2015 ◽  
Vol 83 (9) ◽  
pp. 3381-3395 ◽  
Author(s):  
Qiyao Wang ◽  
Yves A. Millet ◽  
Michael C. Chao ◽  
Jumpei Sasabe ◽  
Brigid M. Davis ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cholera Toxin ◽  
Vibrio Cholerae ◽  
Insertion Site ◽  
Virulence Gene ◽  
Loss Of Function ◽  
Phosphotransferase System ◽  
Content Type ◽  
Virulence Gene Expression ◽  
A Genome

Diverse environmental stimuli and a complex network of regulatory factors are known to modulate expression ofVibrio cholerae's principal virulence factors. However, there is relatively little known about how metabolic factors impinge upon the pathogen's well-characterized cascade of transcription factors that induce expression of cholera toxin and the toxin-coregulated pilus (TCP). Here, we used a transposon insertion site (TIS) sequencing-based strategy to identify new factors required for expression oftcpA, which encodes the major subunit of TCP, the organism's chief intestinal colonization factor. Besides identifying most of the genes known to modulatetcpAexpression, the screen yieldedptsIandptsH, which encode the enzyme I (EI) and Hpr components of theV. choleraephosphoenolpyruvate phosphotransferase system (PTS). In addition to reduced expression of TcpA, strains lacking EI, Hpr, or the associated EIIAGlcprotein produced less cholera toxin (CT) and had a diminished capacity to colonize the infant mouse intestine. The PTS modulates virulence gene expression by regulating expression oftcpPHandaphAB, which themselves control expression oftoxT, the central activator of virulence gene expression. One mechanism by which PTS promotes virulence gene expression appears to be by modulating the amounts of intracellular cyclic AMP (cAMP). Our findings reveal that theV. choleraePTS is an additional modulator of the ToxT regulon and demonstrate the potency of loss-of-function TIS sequencing screens for defining regulatory networks.

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