Co‐ordinate expression of virulence genes by ToxR in <i>Vibrio cholerae</i>

DiRita, Victor J.

doi:10.1111/j.1365-2958.1992.tb01489.x

Cited by 222 publications

(142 citation statements)

References 59 publications

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“…Expression of toxT from a constitutive promoter partially corrects a toxR mutant phenotype (except for the expression of OmpU), consistent with a position for ToxT downstream of ToxR in a regulatory cascade . In this cascade, ToxR activates transcription of cholera toxin, OmpU and toxT, and ToxT in turn activates transcription of the other virulence genes of V. cholerae (DiRita, 1992). Since expression of ToxR is not itself regulated by environmental conditions that modulate expression of cholera toxin and Tcp (DiRita, 1992), the mechanism by which these conditions modulate expression of genes in the ToxR regulon is not well understood.…”

Section: Introductionmentioning

confidence: 99%

Phase variation in tcpH modulates expression of the ToxR regulon in Vibrio cholerae

Carroll

Tashima

Rogers

et al. 1997

Molecular Microbiology

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SummaryWe evaluated a spontaneous mutant of Vibrio cholerae, which was avirulent in an infant mouse and had reduced expression of cholera toxin and TcpA in response to environmental signals. The toxR, toxS and toxT genes in the mutant were normal, but transcription of toxT was absent. A plasmid expressing wild-type tcpP and tcpH complemented the mutant. The mutation resulted from a frameshift in a string of nine G residues within tcpH; similar slipped-strand mutations in tcpH arose at a frequency of 10 ¹4 during overnight growth and in the majority of colonies by the end of 5 days of growth in ToxR-inducing conditions. Transcription of tcpPH was regulated by temperature and pH independently of ToxR or ToxT. These results suggest that TcpH couples environmental signals (temperature and pH) to expression of the ToxR regulon, and provide a model for phase variation in the co-ordinate expression of cholera virulence factors.

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Section: Introductionmentioning

confidence: 99%

Phase variation in tcpH modulates expression of the ToxR regulon in Vibrio cholerae

Carroll

Tashima

Rogers

et al. 1997

Molecular Microbiology

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124

126

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“…This and not the opposite direction of evolution is preferred since, on the one hand, Zot and 0RF3 are closely related to gp1 of PfI but only distantly related to gp1 of other bacteriophages, and on the other hand, it appears most likely that all filamentous bacteriophages have a common origin. The zur gene, together with the adjacent CIX operon encoding the two subunits of the classical cholera toxin, belongs to a site-specific transposable element [15]. It is interesting to speculate that this element could have evolved from a filamentous bacteriophage via a plasmid intermediate resembling pKB74CJ.…”

Section: Evolutionary Implicationsmentioning

confidence: 99%

The second cholera toxin, Zot, and its plasmid‐encoded and phage‐encoded homologues constitute a group of putative ATPases with an altered purine NTP‐binding motif

Koonin

1992

FEBS Letters

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It is shown that the second cholera toxin, Zot, 0RF3 product of Pseudo~o/~s plasmid pKB740, and ORF424 product of bacteriophage Pfl arc a group of closely related proteins conlaining a modified version of the purinc NTP-binding motif, with a drastic substitution of tyrosinc for a conserved glycinc. They are distantly but reliably related to the product of gene I of filamentous bacteriophages which is a putative ATPase containing the classical NTP-binding motif and is involn;cd in iracteriophagc assembly and exit from the bacterial cell. Mydropathy analysis suggests that the Zot and gene I product may have a similar transmembtanc topology. It is hypothcsbecl thal Zot may possess ATPase activity and modify the membrane structure of its target cells in an ATP-dcpendcnt fashion. Genes for Zot and the related protein of pKB740 are likely to have evolved from gene 1 of a Pfl-like bacteriophage.

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“…Environmental sensing and co-ordinate regulation of gene expression is essential for V. cholerae to persist in drastically different environments and cause disease. Among the increasing number of transcription factors described in the regulation of virulence gene expression in V. cholerae, ToxR is the most extensively characterized (reviewed by DiRita, 1992;Skorupski and Taylor, 1997a).…”

Section: Introductionmentioning

confidence: 99%

ToxR interferes with CRP‐dependent transcriptional activation of ompT in Vibrio cholerae

Merrell

Camilli

et al. 2002

Molecular Microbiology

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SummaryIn pathogenic Vibrio cholerae, the transmembrane DNA-binding protein ToxR co-ordinates the expression of over 20 genes, including those encoding important virulence factors such as cholera toxin and the toxin-co-regulated pilus. The outer membrane protein OmpT is the only member of the ToxR regulon known to be repressed by ToxR. In this study, we examined the environmental conditions that regulate OmpT expression and demonstrated that ompT transcription is upregulated 14-fold when the bacteria enter late log phase from early log phase. Deletion of the crp gene completely abolishes OmpT expression. Comparison of ompT transcription levels in the isogenic crp -, toxR -and crp -toxR -mutants revealed that (i) in the absence of ToxR, constitutive high-level ompT transcription is dependent on cAMP receptor protein (CRP); (ii) ToxR not only interferes with CRPdependent ompT activation, but also abolishes the CRP-independent, basal level ompT transcription; thus, the mechanism by which ToxR represses ompT transcription involves both antiactivation and direct repression; (iii) both CRP and ToxR are required for the regulation of OmpT expression by growth phase. To provide further insights into the molecular mechanism of CRP-dependent activation of ompT transcription, we demonstrated that CRP-dependent activation requires a CRP binding site centred at -310 of the ompT promoter, without which the interaction of CRP with other CRP binding site(s) more proximal to the promoter results in repression. Mutations in two regions on CRP (AR1 and AR2) that directly

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Co‐ordinate expression of virulence genes by ToxR in Vibrio cholerae

Cited by 222 publications

References 59 publications

Phase variation in tcpH modulates expression of the ToxR regulon in Vibrio cholerae

Phase variation in tcpH modulates expression of the ToxR regulon in Vibrio cholerae

The second cholera toxin, Zot, and its plasmid‐encoded and phage‐encoded homologues constitute a group of putative ATPases with an altered purine NTP‐binding motif

ToxR interferes with CRP‐dependent transcriptional activation of ompT in Vibrio cholerae

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