Dual Promoters Control Expression of the<i>Bacillus anthracis</i>Virulence Factor AtxA

Bongiorni, Cristina; Fukushima, Tatsuya; Wilson, Adam C.; Chiang, Christina; Mansilla, María C.; Hoch, James A.; Perego, Marta

doi:10.1128/jb.00766-08

Cited by 30 publications

(34 citation statements)

References 37 publications

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“…4A). Similar results showing a modest change in atxA promoter activity upon P2 deletion were reported by Bongiorni et al (7). Activity of a clone harboring only the P1 start site (pUTE843) decreased approximately 3.2-fold when sequences from Ϫ72 to Ϫ54 relative to the P1 transcription start site (ϩ1) were deleted (pUTE890).…”

Section: Fig 2 Siga Consensus Sequence-dependent Expression Of a Transupporting

confidence: 72%

“…A modest decrease in atxA expression was observed upon deletion of P2, indicating that P1 is the dominant transcription start site (7). There is a putative consensus sequence for the housekeeping sigma factor SigA, but not SigH, upstream of each transcription start site.…”

mentioning

confidence: 99%

“…The B. anthracis spo0A promoter has a SigH recognition sequence comparable to that for the B. subtilis gene (23). SigH control of atxA occurs via its positive effect on spo0A, and in one strain, sigH positively regulates atxA expression in a spo0A-and abrB-independent manner (7,23,43,50).…”

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confidence: 99%

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cis -Acting Elements That Control Expression of the Master Virulence Regulatory Gene atxA in Bacillus anthracis

et al. 2012

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Transcription of the Bacillus anthracis structural genes for the anthrax toxin proteins and biosynthetic operon for capsule is positively regulated by AtxA, a transcription regulator with unique properties. Consistent with the role of atxA in virulence factor expression, a B. anthracis atxA-null mutant is avirulent in a murine model for anthrax. In culture, multiple signals impact atxA transcript levels, and the timing and steady-state level of atxA expression are critical for optimal toxin and capsule synthesis. Despite the apparent complex control of atxA transcription, only one trans-acting protein, the transition state regulator AbrB, has been demonstrated to interact directly with the atxA promoter. Here we employ 5= and 3= deletion analysis and sitedirected mutagenesis of the atxA control region to demonstrate that atxA transcription from the major start site P1 is dependent upon a consensus sequence for the housekeeping sigma factor SigA and an A؉T-rich upstream element for RNA polymerase. We also show that an additional trans-acting protein(s) binds specifically to atxA promoter sequences located between ؊13 and ؉36 relative to P1 and negatively impacts transcription. Deletion of this region increases promoter activity up to 15-fold. Site-directed mutagenesis of a 9-bp palindromic sequence within the region prevents binding of the trans-acting protein(s), increasing promoter activity 7-fold and resulting in a corresponding increase in AtxA and anthrax toxin production. Notably, an atxA promoter mutant that produced elevated levels of AtxA and toxin proteins during culture was unaffected for virulence in a murine model for anthrax.

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Section: Fig 2 Siga Consensus Sequence-dependent Expression Of a Transupporting

confidence: 72%

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confidence: 99%

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cis -Acting Elements That Control Expression of the Master Virulence Regulatory Gene atxA in Bacillus anthracis

et al. 2012

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“…The B. anthracis strain used in this study, 34F2⌬118, is a derivative of Sterne strain 34F2 (pXO1 ϩ pXO2 Ϫ ) carrying a spectinomycin replacement of the pXO1-118 coding sequence (2). Transformation of B. anthracis with plasmid DNA was carried out as previously described (11).…”

Section: Methodsmentioning

confidence: 99%

A Unique GTP-Dependent Sporulation Sensor Histidine Kinase in Bacillus anthracis

et al. 2009

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The Bacillus anthracis BA2291 gene codes for a sensor histidine kinase involved in the induction of sporulation. Genes for orthologs of the sensor domain of the BA2291 kinase exist in virulence plasmids in this organism, and these proteins, when expressed, inhibit sporulation by converting BA2291 to an apparent phosphatase of the sporulation phosphorelay. Evidence suggests that the sensor domains inhibit BA2291 by titrating its activating signal ligand. Studies with purified BA2291 revealed that this kinase is uniquely specific for GTP in the forward reaction and GDP in the reverse reaction. The G1 motif of BA2291 is highly modified from ATP-specific histidine kinases, and modeling this motif in the structure of the kinase catalytic domain suggested how guanine binds to the region. A mutation in the putative coiled-coil linker between the sensor domain and the catalytic domains was found to decrease the rate of the forward autophosphorylation reaction and not affect the reverse reaction from phosphorylated Spo0F. The results suggest that the activating ligand for BA2291 is a critical signal for sporulation and in a limited concentration in the cell. Decreasing the response to it either by slowing the forward reaction through mutation or by titration of the ligand by expressing the plasmid-encoded sensor domains switches BA2291 from an inducer to an inhibitor of the phosphorelay and sporulation.

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“…Expression of both virulence determinants strictly depends on the AtxA transcription factor, whose full expression requires the activity of two distinct promoters (7,14,18,19). The mechanisms regulating the activity of these promoters are largely unknown.…”

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confidence: 99%

Glucose-Dependent Activation ofBacillus anthracisToxin Gene Expression and Virulence Requires the Carbon Catabolite Protein CcpA

2011

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Sensing environmental conditions is an essential aspect of bacterial physiology and virulence. In Bacillus anthracis, the causative agent of anthrax, transcription of the two major virulence factors, toxin and capsule, is triggered by bicarbonate, a major compound in the mammalian body. Here it is shown that glucose is an additional signaling molecule recognized by B. anthracis for toxin synthesis. The presence of glucose increased the expression of the protective antigen toxin component-encoding gene (pagA) by stimulating induction of transcription of the AtxA virulence transcription factor. Induction of atxA transcription by glucose required the carbon catabolite protein CcpA via an indirect mechanism. CcpA did not bind specifically to any region of the extended atxA promoter. The virulence of a B. anthracis strain from which the ccpA gene was deleted was significantly attenuated in a mouse model of infection. The data demonstrated that glucose is an important host environment-derived signaling molecule and that CcpA is a molecular link between environmental sensing and B. anthracis pathogenesis.The capacity for sensing and responding to their surroundings is an essential feature of all living organisms. Bacteria have developed an array of highly sophisticated sensing and adaptation systems, such as two-component systems, quorum-sensing systems, and transport systems (9,15,21,42,58). Investigations into bacterial pathogenesis have revealed an intuitive connection between basic metabolic processes of adaptation and virulence. For example, it has been reported that bacteria alter the transcription of carbohydrate utilization genes and virulence factor-encoding genes in response to the sugar availability encountered in the environment, in particular, in the infected host (44,65,67,69,79). Consequently, regulatory mechanisms that connect carbohydrate metabolism to virulence factor production must have evolved.A key role in carbohydrate utilization in both Gram-negative and Gram-positive organisms is played by the complex sugartransporting phosphotransferase system (PTS), but additional proteins and different mechanisms are involved in the two types of bacteria (4,16,53). One of these mechanisms is the carbon catabolite repression (CCR) system that is based on the Crp-cyclic AMP system in Gram-negative bacteria, while the HPr protein of the PTS system, together with the transcription factor CcpA, is the master regulator in Gram-positive bacteria (27,59,75).Extensive work carried out mostly in Bacillus subtilis has demonstrated that HPr can be phosphorylated on the His15 residue (B. subtilis numeration) by the enzyme I (EI) of the PTS in response to the phosphoenolpyruvate-to-pyruvate ratio or on the Ser46 residue by the HPr kinase/phosphorylase (HPrK/P) enzyme in response to the concentrations of ATP, P i , PP i , and fructose-1,6-bisphosphate (FBP) (23,30,43,56). HPr phosphorylated on Ser46 interacts and stimulates CcpA DNA binding activity, thus providing the link between carbon availability and transcriptional a...

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Dual Promoters Control Expression of theBacillus anthracisVirulence Factor AtxA

Cited by 30 publications

References 37 publications

cis -Acting Elements That Control Expression of the Master Virulence Regulatory Gene atxA in Bacillus anthracis

cis -Acting Elements That Control Expression of the Master Virulence Regulatory Gene atxA in Bacillus anthracis

A Unique GTP-Dependent Sporulation Sensor Histidine Kinase in Bacillus anthracis

Glucose-Dependent Activation ofBacillus anthracisToxin Gene Expression and Virulence Requires the Carbon Catabolite Protein CcpA

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