UNIPROT:P51532 - FACTA Search

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Query: UNIPROT:P51532 (transcriptional activator)
6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Upon incubation at 37 degrees C in the absence of Ca2+ ions, pathogenic yersiniae release high amounts of pYV plasmid-encoded proteins called Yops, involved in pathogenesis. Yersinia enterocolitica also express two outer membrane proteins, an adhesin called YadA and a lipoprotein called YlpA. The production of the Yops is co-ordinately regulated by a 20 kb region of the plasmid referred to as the 'Ca2+ dependence region' and containing at least four loci called virA, virB, virC, and virF. The 8.5 kb virC region, involved in the specific transport of the Yops, is a single operon containing 13 open reading frames called yscA to yscM. Gene virF encodes a key transcriptional activator of the yop, yadA and ylpA genes. It is only transcribed at 37 degrees C and its expression is modulated by a chromosome-encoded histone-like protein called YmoA. We show here that virF also controls the virC operon. By contrast, virF is not essential for the induction of virA and virB. The VirF protein binds specifically to yop promoters. In particular, it protects the region spanning nucleotides -64 to -34 of yopH. In order to analyse the role of temperature in the induction of the yop regulon, we constructed Y. enterocolitica strains expressing virF from the tac promoter. In spite of the fact that virF was transcribed at 25 degrees C, neither the Yops nor YadA were expressed at that temperature. This poor response to VirF at 25 degrees C was at least partially due to a weak and slow transcription of the genes controlled by virF. Surprisingly, when cloned on pACYC184, gene yadA was expressed even in absence of VirF, but remained thermodependent. Hence temperature and virF are both required for the induction of the yop regulon. Among other possible roles, temperature could modify the structure of either the activator itself or the yop promoter. The fact that VirF binds in vitro to yop promoters at 25 degrees C rules out the first hypothesis. In order to test the second hypothesis, we studied, in vivo, the activity of the yopH promoter in ymoA mutants. The yopH promoter became active in the absence of VirF, indicating that yop promoter activity depends upon chromatin structure. We conclude from these two observations that, in vivo, temperature is required to modify the DNA structure of the yop promoters in order to allow the action of the transcriptional activator.
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PMID:Role of the transcriptional activator, VirF, and temperature in the expression of the pYV plasmid genes of Yersinia enterocolitica. 155 53

Exoenzyme S is an ADP-ribosyltransferase enzyme distinct from exotoxin A that is synthesized and secreted by Pseudomonas aeruginosa. Yields of exoenzyme S are variable and depend on strain and growth conditions. Since certain medium additives are required for exoenzyme S production, its regulation may be influenced by environmental stimuli. In this study, we have cloned a region that complements the exoenzyme S-deficient phenotype of strain 388 exs1::Tn1, a chromosomal Tn1 insertional mutation. A large clone (28 kb) was shown to restore both synthesis and secretory functions to the mutant strain. Subcloning and Tn501 mutagenesis experiments localized the region required for exoenzyme S synthesis to a 3.2-kb fragment. Nucleotide sequence analysis demonstrated several open reading frames. Comparison of the N-terminal amino acid sequence of purified exoenzyme S with predicted amino acid sequences of all open reading frames indicated that the structural gene was not encoded within the sequenced region. Homology studies suggested that the region encoded three regulatory genes, exsC, exsB, and exsA. ExsA was homologous to the AraC family of transcriptional activator proteins, with extensive homology being found with one member of this family, VirF of Yersinia enterocolitica. VirF and ExsA both contain carboxy-terminal domains with the helix-turn-helix motif of DNA-binding proteins. The ExsA gene product appeared to be required for induction of exoenzyme S synthesis above a low basal level. Expression of ExsA was demonstrated by cloning the region under the control of the T7 promoter. Gene replacement experiments suggested that the expression of ExsC affects the final yield of exoenzyme S.
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PMID:Cloning and sequence analysis of a trans-regulatory locus required for exoenzyme S synthesis in Pseudomonas aeruginosa. 165 13

The expression of listeriolysin, a major virulence factor of the gram-positive facultative intracellular pathogen Listeria monocytogenes, is positively regulated by a transcriptional activator, the prfA gene product. We had previously shown that mutations within the prfA gene lead to loss of listeriolysin production. In this communication, the regulation of expression of listeriolysin by a specific environmental condition, namely, temperature, was studied in wild-type strains of Listeria monocytogenes. We found that expression of the hemolysis phenotype was thermoregulated. A lisA::lacZ fusion was constructed, and its expression in the wild-type strain was studied at various growth temperatures. The results showed that the fusion beta-galactosidase activity was expressed only when cultures were grown at temperatures above 30 degrees C. This activity could be either specifically repressed or induced, depending on growth temperature. No change in activity was detected in a strain harboring a control beta-galactosidase fusion at the various growth temperatures tested. Northern (RNA) blot analysis of lisA-specific RNA transcripts showed that thermoregulation is manifested at the level of transcription. We also found that the transcription of other PrfA-regulated virulence genes in L. monocytogenes was similarly affected by growth temperature. Hence, as in other facultative intracellular pathogens, Shigella and Yersinia spp., temperature is an important cue in the induction of expression of virulence genes in L. monocytogenes. Our studies revealed that a higher level of regulation is imposed on the PrfA-mediated activation of virulence genes in pathogenic L. monocytogenes.
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PMID:The expression of virulence genes in Listeria monocytogenes is thermoregulated. 173 27

Upon incubation at 37 degrees C in the absence of Ca2+ ions, pathogenic yersiniae release large amounts of pYV plasmid-encoded proteins called Yops that are involved in pathogenesis. Yersinia enterocolitica also expresses an outer membrane protein that is considered an adhesin and called YadA (previously called P1 or YopA). The production of Yops is coordinately regulated by a 20-kb region of the plasmid referred to as the Ca2+ dependence region and containing at least four loci called virA, virB, virC, and virF. The virF gene encodes a key transcriptional activator of yop genes. We have shown here that virF is also required for transcription of yadA and that virB is necessary for full transcription of the yop and yadA genes. In contrast, mutations in genes virA and virC had only a weak influence on the transcription of yop and yadA genes. These mutations did not affect the production of YadA but they completely inhibited the translocation of Yops from the intracellular compartment to the extracellular milieu. We inferred from these data that virA and virC are involved in the specific transport of Yops. We analyzed the 8.5-kb virC region and showed that it is most probably a single operon containing 13 open reading frames called yscA to yscM (for Yop secretion). Protein YscC has a putative signal sequence and shares significant homology with outer membrane proteins involved in the secretion of pullulanase by Klebsiella pneumoniae (PulD) or in the assembly of filamentous bacteriophages (gene IV product). At least the putative products of yscD, yscJ, and yscL were shown to be required for the export of Yops. YscJ turned out to be YlpB, a lipoprotein that we had detected previously. The yscM gene shares homology with yopH, the adjacent gene on the pYV plasmid. Its product does not appear to be necessary for the production of Yops. Transcription of the virC operon was subjected to the same regulation as the yop genes.
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PMID:Analysis of virC, an operon involved in the secretion of Yop proteins by Yersinia enterocolitica. 186 Aug 16

The virulence functions of Yersinia enterocolitica include the pYV-encoded Yop proteins and YadA adhesin as well as the chromosome-encoded enterotoxin, Yst. The yop and yadA genes form a temperature-activated regulon controlled by the transcriptional activator VirF. Gene virF, also localized on pYV, is itself thermoinduced in the absence of other pYV genes. The enterotoxin yst gene is silent in some collection strains including strain W22703. This paper describes two Tn5-Tc1 chromosomal insertion mutants of W22703 transcribing virF, and hence the yop and yadA genes, at low temperature. These mutants also resumed their production of Yst, with its typical temperature dependence. Both mutations were insertions in the same gene called ymoA for 'Yersinia modulator'. The cloned ymoA gene fully complemented the two mutations. Several properties of the mutants suggest that ymoA encodes a histone-like protein. According to the nucleic acid sequence, the product of ymoA is an 8064 Da protein rich in aspartic acid (9%), glutamic acid (9%) and lysine (10.5%), but the predicted amino acid sequence shows no similarity with any described histone-like protein. This work supports recent reports which propose a role for DNA topology and bacterial chromatin structure in thermoregulation of virulence functions.
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PMID:ymoA, a Yersinia enterocolitica chromosomal gene modulating the expression of virulence functions. 195 83

Virulent yersiniae (Yersinia pestis, Y. pseudotuberculosis, and Y. enterocolitica) restrict their growth at 37 degrees C in rich medium deprived of calcium. This property, called calcium dependency, correlates with the secretion of Yersinia outer membrane proteins (Yops) and with pathogenicity. It is mediated by a 70-kilobase plasmid called pYV. The structural genes of the Yops (yop genes), as well as genes involved in the control of their expression (vir genes), have been localized on pYV. In this communication we show that virF encodes a transcriptional activator controlling the yop regulon. This activator is a 30,879-dalton protein related to AraC, the regulator of the Escherichia coli and Salmonella typhimurium arabinose operons. We also show in this paper that transcription of virF is thermodependent and presumably autoregulated. virF is thus responsible for the effect of temperature on the production of the Yops. Finally, we show that virF activates transcription of the yop genes independently of the presence of calcium ions. The role of calcium therefore remains unaccounted for.
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PMID:Homology between virF, the transcriptional activator of the Yersinia virulence regulon, and AraC, the Escherichia coli arabinose operon regulator. 264 92

In recent years it has become clear that the production of N-acyl homoserine lactones (N-AHLs) is widespread in Gram-negative bacteria. These molecules act as diffusible chemical communication signals (bacterial pheromones) which regulate diverse physiological processes including bioluminescence, antibiotic production, plasmid conjugal transfer and synthesis of exoenzyme virulence factors in plant and animal pathogens. The paradigm for N-AHL production is in the bioluminescence (lux) phenotype of Photobacterium fischeri (formerly classified as Vibrio fischeri) where the signalling molecule N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) is synthesized by the action of the LuxI protein. OHHL is thought to bind to the LuxR protein, allowing it to act as a positive transcriptional activator in an autoinduction process that physiologically couples cell density (and growth phase) to the expression of the bioluminescence genes. Based on the growing information on LuxI and LuxR homologues in other N-AHL-producing bacterial species such as Erwinia carotovora, Pseudomonas aeruginosa, Yersinia enterocolitica, Agrobacterium tumefaciens and Rhizobium leguminosarum, it seems that analogues of the P. fischeri lux autoinducer sensing system are widely distributed in bacteria. The general physiological function of these simple chemical signalling systems appears to be the modulation of discrete and diverse metabolic processes in concert with cell density. In an evolutionary sense, the elaboration and action of these bacterial pheromones can be viewed as an example of multicellularity in prokaryotic populations.
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PMID:The bacterial 'enigma': cracking the code of cell-cell communication. 747 57

The hrpX gene is essential for pathogenicity of Xanthomonas species. Loss of hrpX by mutation results in the loss of pathogenicity and a gain in the ability of Xanthomonas to cause the hypersensitive response in their respective host plants, suggesting that hrpX confers a means to evade this host defense response. The function of HrpX protein was predicted by sequencing of hrpXc and hrpXo from X. campestris pv. campestris and X. oryzae, respectively. The predicted amino acid sequences of the protein encoded by these respective genes revealed similarities (45.96%) to the HrpB protein of Burkholderia solanacearum, which has sequence identity to the transcriptional activator VirF of Yersinia enterocolitica and AraC of Escherichia coli. Thus, HrpX may regulate Xanthomonas virulence genes since a putative DNA binding domain present in the carboxyl terminal half of HrpX is highly conserved among HrpB, VirF and AraC and since over-expression of the carboxyl terminal half of HrpX in E. coli is lethal.
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PMID:Conservation of the hypersensitivity-pathogenicity regulatory gene hrpX of Xanthomonas campestris and X. oryzae. 762 86

Pathogenic yersiniae require Ca2+ for growth at 37 degrees C. They harbor closely related plasmids of about 70 kb that are essential for virulence. At 37 degrees C and in the absence of Ca2+ ions, these plasmids cause a decrease in growth rate and the release of large amounts of proteins called Yops. Here we describe the virG gene of Yersinia enterocolitica; virG is located just upstream of the virF gene, which encodes the transcriptional activator of some plasmid virulence factors. Analysis of the VirG amino acid sequence suggested that virG encodes a lipoprotein, which was confirmed by [3H]palmitate labeling of VirG-PhoA fusion proteins. A nonpolar virG mutant was constructed and found to be Ca2+ independent for growth at 37 degrees C but to still secrete Yops. This phenotype was complemented by the introduction of a plasmid harboring an intact virG gene. VirG was found to be homologous to ExsB, a protein encoded by a Pseudomonas aeruginosa gene located in the locus controlling exoenzyme S synthesis. Interestingly, the exsA gene, located just downstream of exsB, is also homologous to virF.
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PMID:VirG, a Yersinia enterocolitica lipoprotein involved in Ca2+ dependency, is related to exsB of Pseudomonas aeruginosa. 763 10

The chromosome of Y. enterocolitica encodes a heat-stable enterotoxin, Yst, being related to STI. The capacity to produce Yst generally disappears during storage of the strains. In these strains, the yst gene is intact but remains silent. The pYV plasmid encodes the eleven secreted antihost proteins called Yops as well as the outer membrane protein YadA. The Yops are secreted by a novel, pYV-encoded secretion mechanism. This mechanism which does not involve the removal of an N-terminal signal sequence, is encoded by the pYV virA and virC loci. The virC locus contains 13 genes called yscA-M. The virA locus encodes the LcrD membrane protein. The yop, yadA and ysc genes form the yop regulon controlled by transcriptional activator VirF. Transcription of the yop, yadA, ysc and virF genes is controlled by temperature. A chromosome-encoded histone-like protein, called YmoA, is involved in the thermoregulation of the yop regulon, which suggests that this thermoregulation could result from temperature-induced changes in DNA topology. The phenotype of ymoA mutants resembles that of osmZ or drdX mutants of E. coli but YmoA is not the Yersinia homologue of the E. coli histone H1. The YmoA histone is also involved in the silencing of the yst gene.
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PMID:Role of the transcription activator virF and the histone-like protein YmoA in the thermoregulation of virulence functions in yersiniae. 834 24

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