101
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MprA and DosR coregulate a Mycobacterium tuberculosis virulence operon encoding Rv1813c and Rv1812c. Infect Immun 2012; 80:3018-33. [PMID: 22689819 DOI: 10.1128/iai.00520-12] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis remains a significant global pathogen, causing extensive morbidity and mortality worldwide. This bacterium persists within granulomatous lesions in a poorly characterized, nonreplicating state. The two-component signal transduction systems MprAB and DosRS-DosT (DevRS-Rv2027c) are responsive to conditions likely to be present within granulomatous lesions and mediate aspects of M. tuberculosis persistence in vitro and in vivo. Here, we describe a previously uncharacterized locus, Rv1813c-Rv1812c, that is coregulated by both MprA and DosR. We demonstrate that MprA and DosR bind to adjacent and overlapping sequences within the promoter region of Rv1813c and direct transcription from an initiation site located several hundred base pairs upstream of the Rv1813 translation start site. We further show that Rv1813c and Rv1812c are cotranscribed, and that the genomic organization of this operon is specific to M. tuberculosis and Mycobacterium bovis. Although Rv1813c is not required for survival of M. tuberculosis in vitro, including under conditions in which MprAB and DosRST signaling are activated, an M. tuberculosis ΔRv1813c mutant is attenuated in the low-dose aerosol model of murine tuberculosis, where it exhibits a lower bacterial burden, delayed time to death, and decreased ability to stimulate proinflammatory cytokines interleukin-1β (IL-1β) and IL-12. Interestingly, overcomplementation of these phenotypes is observed in the M. tuberculosis ΔRv1813c mutant expressing both Rv1813c and Rv1812c, but not Rv1813c alone, in trans. Therefore, Rv1813c and Rv1812c may represent general stress-responsive elements that are necessary for aspects of M. tuberculosis virulence and the host immune response to infection.
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102
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De Majumdar S, Vashist A, Dhingra S, Gupta R, Singh A, Challu VK, Ramanathan VD, Kumar P, Tyagi JS. Appropriate DevR (DosR)-mediated signaling determines transcriptional response, hypoxic viability and virulence of Mycobacterium tuberculosis. PLoS One 2012; 7:e35847. [PMID: 22563409 PMCID: PMC3338549 DOI: 10.1371/journal.pone.0035847] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2012] [Accepted: 03/23/2012] [Indexed: 11/25/2022] Open
Abstract
Background The DevR(DosR) regulon is implicated in hypoxic adaptation and virulence of Mycobacterium tuberculosis. The present study was designed to decipher the impact of perturbation in DevR-mediated signaling on these properties. Methodology/Principal Findings M. tb complemented (Comp) strains expressing different levels of DevR were constructed in Mut1* background (expressing DevR N-terminal domain in fusion with AphI (DevRN-Kan) and in Mut2ΔdevR background (deletion mutant). They were compared for their hypoxia adaptation and virulence properties. Diverse phenotypes were noted; basal level expression (∼5.3±2.3 µM) when induced to levels equivalent to WT levels (∼25.8±9.3 µM) was associated with robust DevR regulon induction and hypoxic adaptation (Comp 9* and 10*), whereas low-level expression (detectable at transcript level) as in Comp 11* and Comp15 was associated with an adaptation defect. Intermediate-level expression (∼3.3±1.2 µM) partially restored hypoxic adaptation functions in Comp2, but not in Comp1* bacteria that co-expressed DevRN-Kan. Comp* strains in Mut1* background also exhibited diverse virulence phenotypes; high/very low-level DevR expression was associated with virulence whereas intermediate-level expression was associated with low virulence. Transcription profiling and gene expression analysis revealed up-regulation of the phosphate starvation response (PSR) in Mut1* and Comp11* bacteria, but not in WT/Mut2ΔdevR/other Comp strains, indicating a plasticity in expression pathways that is determined by the magnitude of signaling perturbation through DevRN-Kan. Conclusions/Significance A minimum DevR concentration of ∼3.3±1.2 µM (as in Comp2 bacteria) is required to support HspX expression in the standing culture hypoxia model. The relative intracellular concentrations of DevR and DevRN-Kan appear to be critical for determining dormancy regulon induction, hypoxic adaptation and virulence. Dysregulated DevRN-Kan-mediated signaling selectively triggers the PSR in bacteria expressing no/very low level of DevR. Our findings illustrate the important role of appropriate two-component- mediated signaling in pathogen physiology and the resilience of bacteria when such signaling is perturbed.
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Affiliation(s)
| | - Atul Vashist
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India
| | - Sakshi Dhingra
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India
| | - Rajesh Gupta
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India
| | - Alka Singh
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India
| | | | - V. D. Ramanathan
- Department of Pathology, Tuberculosis Research Centre, Chennai, India
| | | | - Jaya Sivaswami Tyagi
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India
- * E-mail:
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103
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Hegde SR, Rajasingh H, Das C, Mande SS, Mande SC. Understanding communication signals during mycobacterial latency through predicted genome-wide protein interactions and boolean modeling. PLoS One 2012; 7:e33893. [PMID: 22448278 PMCID: PMC3309013 DOI: 10.1371/journal.pone.0033893] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 02/18/2012] [Indexed: 12/18/2022] Open
Abstract
About 90% of the people infected with Mycobacterium tuberculosis carry latent bacteria that are believed to get activated upon immune suppression. One of the fundamental challenges in the control of tuberculosis is therefore to understand molecular mechanisms involved in the onset of latency and/or reactivation. We have attempted to address this problem at the systems level by a combination of predicted functional protein:protein interactions, integration of functional interactions with large scale gene expression studies, predicted transcription regulatory network and finally simulations with a boolean model of the network. Initially a prediction for genome-wide protein functional linkages was obtained based on genome-context methods using a Support Vector Machine. This set of protein functional linkages along with gene expression data of the available models of latency was employed to identify proteins involved in mediating switch signals during dormancy. We show that genes that are up and down regulated during dormancy are not only coordinately regulated under dormancy-like conditions but also under a variety of other experimental conditions. Their synchronized regulation indicates that they form a tightly regulated gene cluster and might form a latency-regulon. Conservation of these genes across bacterial species suggests a unique evolutionary history that might be associated with M. tuberculosis dormancy. Finally, simulations with a boolean model based on the regulatory network with logical relationships derived from gene expression data reveals a bistable switch suggesting alternating latent and actively growing states. Our analysis based on the interaction network therefore reveals a potential model of M. tuberculosis latency.
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Affiliation(s)
- Shubhada R. Hegde
- Structural Biology Laboratory, Centre for DNA Fingerprinting and Diagnostics, Gruhakalpa, Nampally, Hyderabad, India
| | - Hannah Rajasingh
- Bio-Sciences R & D Division, TCS Innovation Labs, Tata Consultancy Services, Hyderabad, India
| | - Chandrani Das
- Structural Biology Laboratory, Centre for DNA Fingerprinting and Diagnostics, Gruhakalpa, Nampally, Hyderabad, India
- Bio-Sciences R & D Division, TCS Innovation Labs, Tata Consultancy Services, Hyderabad, India
| | - Sharmila S. Mande
- Bio-Sciences R & D Division, TCS Innovation Labs, Tata Consultancy Services, Hyderabad, India
| | - Shekhar C. Mande
- Structural Biology Laboratory, Centre for DNA Fingerprinting and Diagnostics, Gruhakalpa, Nampally, Hyderabad, India
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104
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Both phthiocerol dimycocerosates and phenolic glycolipids are required for virulence of Mycobacterium marinum. Infect Immun 2012; 80:1381-9. [PMID: 22290144 DOI: 10.1128/iai.06370-11] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Phthiocerol dimycocerosates (PDIMs) and structurally related phenolic glycolipids (PGLs) are complex cell wall lipids unique to pathogenic mycobacteria. While these lipids have been extensively studied in recent years, there are conflicting reports on some aspects of their biosynthesis and on the role of PDIMs and especially PGLs in virulence of Mycobacterium tuberculosis. This has been complicated by the natural deficiency of PGLs in many clinical strains of M. tuberculosis and the frequent loss of PDIMs in laboratory M. tuberculosis strains. In this study, we isolated seven mutants of Mycobacterium marinum deficient in PDIMs and/or PGLs in which multiple genes of the PDIM/PGL biosynthetic locus were disrupted by transposon insertion. Zebrafish infection experiments showed that M. marinum strains lacking one or both of these lipids were avirulent, suggesting that both PDIMs and PGLs are required for virulence. We also found that these strains were hypersensitive to antibiotics and exhibited increased cell wall permeability. Our studies provide new insights into the biosynthesis of PDIMs/PGLs and may help us to understand the role of PDIMs and PGLs in M. tuberculosis virulence.
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105
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Abstract
Bacteria survive treatments with antimicrobial agents; they achieve this in two ways. Firstly, bacteria quickly become tolerant to these agents. This tolerance is temporary, reversible, and associated with slowing of the multiplication rate. Secondly, bacteria can undergo genetic mutations leading to permanent clonal resistance to antimicrobial agents. In patients with infections, nonmultiplying bacteria, some of which may be viable but nonculturable, exist side by side with multiplying bacteria. Current antibiotics capable of killing actively multiplying bacteria have very limited or no effect against nonmultiplying bacteria. Treatment of such infections requires a regimen of multiple antimicrobial agents in order to control nonmultiplying persistent bacteria. This is especially important in tuberculosis where there is co-existence of slowly multiplying tolerant bacteria with fast growing sensitive organisms. For this reason, a prolonged length of chemotherapy, lasting 6 months, is necessary to achieve cure. This long duration of treatment is due to the slow, inadequate effect of antibiotics on nonmultiplying persistent bacteria. Similar problems with eradication of persistent bacteria are evident in the treatment of biofilms. These bacteria serve as a pool for recurrent infections. Extended courses of antibiotics increase the likelihood of genetic resistance, raise the cost of treatments, and lead to more side effects.
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Affiliation(s)
- Yanmin Hu
- Centre for Infection, St George's University of London, London, UK.
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106
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Bretl DJ, Demetriadou C, Zahrt TC. Adaptation to environmental stimuli within the host: two-component signal transduction systems of Mycobacterium tuberculosis. Microbiol Mol Biol Rev 2011; 75:566-82. [PMID: 22126994 PMCID: PMC3232741 DOI: 10.1128/mmbr.05004-11] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pathogenic microorganisms encounter a variety of environmental stresses following infection of their respective hosts. Mycobacterium tuberculosis, the etiological agent of tuberculosis, is an unusual bacterial pathogen in that it is able to establish lifelong infections in individuals within granulomatous lesions that are formed following a productive immune response. Adaptation to this highly dynamic environment is thought to be mediated primarily through transcriptional reprogramming initiated in response to recognition of stimuli, including low-oxygen tension, nutrient depletion, reactive oxygen and nitrogen species, altered pH, toxic lipid moieties, cell wall/cell membrane-perturbing agents, and other environmental cues. To survive continued exposure to these potentially adverse factors, M. tuberculosis encodes a variety of regulatory factors, including 11 complete two-component signal transduction systems (TCSSs) and several orphaned response regulators (RRs) and sensor kinases (SKs). This report reviews our current knowledge of the TCSSs present in M. tuberculosis. In particular, we discuss the biochemical and functional characteristics of individual RRs and SKs, the environmental stimuli regulating their activation, the regulons controlled by the various TCSSs, and the known or postulated role(s) of individual TCSSs in the context of M. tuberculosis physiology and/or pathogenesis.
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Affiliation(s)
| | | | - Thomas C. Zahrt
- Center for Infectious Disease Research and Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226-0509
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107
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Pang X, Cao G, Neuenschwander PF, Haydel SE, Hou G, Howard ST. The β-propeller gene Rv1057 of Mycobacterium tuberculosis has a complex promoter directly regulated by both the MprAB and TrcRS two-component systems. Tuberculosis (Edinb) 2011; 91 Suppl 1:S142-9. [PMID: 22099420 DOI: 10.1016/j.tube.2011.10.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The β-propeller gene Rv1057 of Mycobacterium tuberculosis is activated by envelope stress and was first characterized as a regulatory target of the TrcRS two-component system (TCS). Rv1057 expression is repressed by TrcRS, and the Rv1057 proximal promoter contains a TrcR binding site. In this study, we determined that Rv1057 is also directly regulated by MprAB, a TCS associated with envelope stress. Multiple potential MprA binding sites (MprA boxes) were identified in the 1 kb intergenic region upstream of Rv1057, and four sites were shown to bind MprA. Although MprA boxes were found in the proximal promoter, analyses suggest that MprA and TrcR do not compete for binding in this region. An MprAB-dependent, detergent-inducible transcriptional start point for Rv1057 was identified downstream of the MprA boxes, and a second TrcR binding site and small ORF of the 13E12 family were discovered in the distal promoter. MprAB was required for activation of Rv1057 during growth in macrophages and under detergent stress, and lacZ promoter constructs suggest the entire intergenic region is utilized during MprAB-dependent activation of Rv1057. These findings indicate that Rv1057 has an extensive and complex promoter, and provide evidence for coordinated regulation of stress response genes by TCSs.
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Affiliation(s)
- Xiuhua Pang
- The State Key Lab of Microbial Technology, Shandong University, Jinan 250100, China.
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108
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Bhattacharya M, Das AK. Inverted repeats in the promoter as an autoregulatory sequence for TcrX in Mycobacterium tuberculosis. Biochem Biophys Res Commun 2011; 415:17-23. [PMID: 22001925 DOI: 10.1016/j.bbrc.2011.09.143] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 09/29/2011] [Indexed: 11/27/2022]
Abstract
TcrY, a histidine kinase, and TcrX, a response regulator, constitute a two-component system in Mycobacterium tuberculosis. tcrX, which is expressed during iron scarcity, is instrumental in the survival of iron-dependent M. tuberculosis. However, the regulator of tcrX/Y has not been fully characterized. Crosslinking studies of TcrX reveal that it can form oligomers in vitro. Electrophoretic mobility shift assays (EMSAs) show that TcrX recognizes two regions in the promoter that are comprised of inverted repeats separated by ∼30 bp. The dimeric in silico model of TcrX predicts binding to one of these inverted repeat regions. Site-directed mutagenesis and radioactive phosphorylation indicate that D54 of TcrX is phosphorylated by H256 of TcrY. However, phosphorylated and unphosphorylated TcrX bind the regulatory sequence with equal efficiency, which was shown with an EMSA using the D54A TcrX mutant.
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Affiliation(s)
- Monolekha Bhattacharya
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
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109
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He H, Bretl DJ, Penoske RM, Anderson DM, Zahrt TC. Components of the Rv0081-Rv0088 locus, which encodes a predicted formate hydrogenlyase complex, are coregulated by Rv0081, MprA, and DosR in Mycobacterium tuberculosis. J Bacteriol 2011; 193:5105-18. [PMID: 21821774 PMCID: PMC3187382 DOI: 10.1128/jb.05562-11] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 07/27/2011] [Indexed: 01/04/2023] Open
Abstract
Mycobacterium tuberculosis, the etiological agent of tuberculosis, remains a significant cause of morbidity and mortality throughout the world despite a vaccine and cost-effective antibiotics. The success of this organism can be attributed, in part, to its ability to adapt to potentially harmful stress within the host and establish, maintain, and reactivate from long-term persistent infection within granulomatous structures. The DosRS-DosT/DevRS-Rv2027c, and MprAB two-component signal transduction systems have previously been implicated in aspects of persistent infection by M. tuberculosis and are known to be responsive to conditions likely to be found within the granuloma. Here, we describe initial characterization of a locus (Rv0081-Rv0088) encoding components of a predicted formate hydrogenylase enzyme complex that is directly regulated by DosR/DevR and MprA, and the product of the first gene in this operon, Rv0081. In particular, we demonstrate that Rv0081 negatively regulates its own expression and that of downstream genes by binding an inverted repeat element in its upstream region. In contrast, DosR/DevR and MprA positively regulate Rv0081 expression by binding to recognition sequences that either partially or completely overlap that recognized by Rv0081, respectively. Expression of Rv0081 initiates from two promoter elements; one promoter located downstream of the DosR/DevR binding site but overlapping the sequence recognized by both Rv0081 and MprA and another promoter downstream of the DosR/DevR, Rv0081, and MprA binding sites. Interestingly, Rv0081 represses Rv0081 and downstream determinants following activation of DosRS-DosT/DevRS-Rv2027c by nitric oxide, suggesting that expression of this locus is complex and subject to multiple levels of regulation. Based on this and other published information, a model is proposed detailing Rv0081-Rv0088 expression by these transcription factors within particular growth environments.
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Affiliation(s)
- Hongjun He
- Department of Microbiology and Molecular Genetics, Center for Infectious Disease Research, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226-0509
| | - Daniel J. Bretl
- Department of Microbiology and Molecular Genetics, Center for Infectious Disease Research, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226-0509
| | - Renee M. Penoske
- Department of Microbiology and Molecular Genetics, Center for Infectious Disease Research, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226-0509
| | - David M. Anderson
- Department of Microbiology and Molecular Genetics, Center for Infectious Disease Research, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226-0509
| | - Thomas C. Zahrt
- Department of Microbiology and Molecular Genetics, Center for Infectious Disease Research, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226-0509
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110
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The residue threonine 82 of DevR (DosR) is essential for DevR activation and function in Mycobacterium tuberculosis despite its atypical location. J Bacteriol 2011; 193:4849-58. [PMID: 21764934 DOI: 10.1128/jb.05051-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The DevR (DosR) response regulator initiates the bacterial adaptive response to a variety of signals, including hypoxia in in vitro models of dormancy. Its receiver domain works as a phosphorylation-mediated switch to activate the DNA binding property of its output domain. Receiver domains are characterized by the presence of several highly conserved residues, and these sequence features correlate with structure and hence function. In response regulators, interaction of phosphorylated aspartic acid at the active site with the conserved threonine is believed to be crucial for phosphorylation-mediated conformational change. DevR contains all the conserved residues, but the structure of its receiver domain in the unphosphorylated protein is strikingly different, and key threonine (T82), tyrosine (Y101), and lysine (K104) residues are placed uncharacteristically far from the D54 phosphorylation site. In view of the atypical location of T82 in DevR, the present study aimed to examine the importance of this residue in the activation mechanism. Mycobacterium tuberculosis expressing a DevR T82A mutant protein is defective in autoregulation and supports hypoxic induction of the DevR regulon only very weakly. These defects are ascribed to slow and partial phosphorylation and the failure of T82A mutant protein to bind cooperatively with DNA. Our results indicate that the T82 residue is crucial in implementing conformational changes in DevR that are essential for cooperative binding and for subsequent gene activation. We propose that the function of the T82 residue in the activation mechanism of DevR is conserved in spite of the unusual architecture of its receiver domain.
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111
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Roberts G, Vadrevu IS, Madiraju MV, Parish T. Control of CydB and GltA1 expression by the SenX3 RegX3 two component regulatory system of Mycobacterium tuberculosis. PLoS One 2011; 6:e21090. [PMID: 21698211 PMCID: PMC3116866 DOI: 10.1371/journal.pone.0021090] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 05/20/2011] [Indexed: 01/05/2023] Open
Abstract
Two component regulatory systems are used widely by bacteria to coordinate changes in global gene expression profiles in response to environmental signals. The SenX3-RegX3 two component system of Mycobacterium tuberculosis has previously been shown to play a role in virulence and phosphate-responsive control of gene expression. We demonstrate that expression of SenX3-RegX3 is controlled in response to growth conditions, although the absolute changes are small. Global gene expression profiling of a RegX3 deletion strain and wild-type strain in different culture conditions (static, microaerobic, anaerobic), as well as in an over-expressing strain identified a number of genes with changed expression patterns. Among those were genes previously identified as differentially regulated in aerobic culture, including ald (encoding alanine dehydrogenase) cyd,encoding a subunit of the cytochrome D ubiquinol oxidase, and gltA1, encoding a citrate synthase. Promoter activity in the upstream regions of both cydB and gltA1 was altered in the RegX3 deletion strain. DNA-binding assays confirmed that RegX3 binds to the promoter regions of ald, cydB and gltA1 in a phosphorylation-dependent manner. Taken together these data suggest a direct role for the SenX-RegX3 system in modulating expression of aerobic respiration, in addition to its role during phosphate limitation.
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Affiliation(s)
- Gretta Roberts
- Queen Mary University of London, Barts and the London School of Medicine and Dentistry, London, United Kingdom
| | - Indumathi S. Vadrevu
- Biomedical Research, The University of Texas Health Center, Tyler, Texas, United States of America
| | - Murty V. Madiraju
- Biomedical Research, The University of Texas Health Center, Tyler, Texas, United States of America
| | - Tanya Parish
- Queen Mary University of London, Barts and the London School of Medicine and Dentistry, London, United Kingdom
- Infectious Disease Research Institute, Seattle, Washington, United States of America
- * E-mail:
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112
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Hu Y, Coates ARM. Mycobacterium tuberculosis acg gene is required for growth and virulence in vivo. PLoS One 2011; 6:e20958. [PMID: 21687631 PMCID: PMC3110807 DOI: 10.1371/journal.pone.0020958] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 05/16/2011] [Indexed: 11/29/2022] Open
Abstract
Mycobacterium tuberculosisdosRS two-component regulatory system controls transcription of approximately 50 genes including hspX, acg and Rv2030c, in response to hypoxia and nitric oxide conditions and within macrophages and mice. The hspX lies between acg and Rv2030c. However, the functions of the dosR regulated genes in vitro and in vivo are largely unknown. Previously, we demonstrated that deletion of hspX gene produced a mutant which grew faster in macrophages and in mice. In this study, we attempted to determine the functions of acg and Rv2030c by gene inactivation. We demonstrate that Rv2030c is dispensable for virulence and growth. However, deletion of acg produced a mutant which is attenuated in both resting and activated macrophages and in acute and persistent murine infection models. Surprisingly, deletion of acg did not compromise the viability of the mutant to nitrosative and oxidative stresses in vitro and in vivo. In addition, when the WT and the acg mutants were treated with antibiotics such as the prodrugs nitrofurantoin and nitrofuran, the acg mutant became more sensitive than the WT strain to these drugs. This suggests that Acg may not function as a nitroreductase. These data indicate that acg encodes an essential virulence factor for M. tuberculosis and enables it to grow and survive in macrophages and in mouse organs.
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Affiliation(s)
- Yanmin Hu
- Division of Clinical Sciences, Infection and Immunity Research Centre, St. George's University of London, London, United Kingdom
| | - Anthony R. M. Coates
- Division of Clinical Sciences, Infection and Immunity Research Centre, St. George's University of London, London, United Kingdom
- * E-mail:
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113
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Chauhan S, Sharma D, Singh A, Surolia A, Tyagi JS. Comprehensive insights into Mycobacterium tuberculosis DevR (DosR) regulon activation switch. Nucleic Acids Res 2011; 39:7400-14. [PMID: 21653552 PMCID: PMC3177182 DOI: 10.1093/nar/gkr375] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
DevR regulon function is believed to be crucial for the survival of Mycobacterium tuberculosis during dormancy. In this study, we undertook a comprehensive analysis of the DevR regulon. All the regulon promoters were assigned to four classes based on the number of DevR binding sites (Dev boxes). A minimum of two boxes are essential for complete interaction and their tandem arrangement is an architectural hallmark at all promoters. Initial interaction of DevR with the conserved box is essential for its cooperative binding to adjacent sites bearing low to very poor sequence conservation and is the universal mechanism underlying DevR-mediated transcriptional induction. The functional importance of tandem arrangement was established by analyzing promoter variants harboring Dev boxes with altered spacing. Conserved sequence logos were generated from 47 binding sequences which included 24 newly discovered Dev boxes. In each half site of an 18-bp binding motif, G5 and C7 are essential for DevR binding. Finally, we show that DevR regulon induction occurs in a temporal manner and genes that are induced early are also usually powerfully induced. The information theory-based approach along with binding and temporal expression studies provide us with comprehensive insights into the complex pattern of DevR regulon activation.
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Affiliation(s)
- Santosh Chauhan
- Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
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114
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Gupta RK, Chauhan S, Tyagi JS. K182G substitution in DevR or C₈G mutation in the Dev box impairs protein-DNA interaction and abrogates DevR-mediated gene induction in Mycobacterium tuberculosis. FEBS J 2011; 278:2131-9. [PMID: 21518251 DOI: 10.1111/j.1742-4658.2011.08130.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The DevR response regulator mediates adaptation of Mycobacterium tuberculosis to various signals that are likely to be encountered within the host such as hypoxia, nitric oxide, carbon monoxide and ascorbic acid. DevR is proposed as a promising target for developing drugs against dormant bacteria. It induces the expression of target genes by interacting with DNA motifs located in their promoter regions. An understanding of DNA-protein interactions is expected to facilitate the development of inhibitors targeting DevR. Only three amino acids in DevR, namely Lys179, Lys182 and Asn183, directly contact nucleotide bases in the DNA motif. The present study was designed to decipher the contribution of Lys182 in DevR function. M. tuberculosis fdxA (Rv2007c), a member of the DevR regulon, was selected for this analysis. Its transcriptional start point was mapped at -1 or -2 with respect to the putative translational start site suggesting that fdxA is expressed as a leaderless mRNA. DNase I footprinting led to the discovery of a secondary binding site and induction of the fdxA promoter is explained by the cooperative binding of DevR to two binding sites. Mutation of Lys182 lowers the DNA binding affinity of DevR and abrogates induction of fdxA and other regulon genes. Mutational analyses also highlight the singular importance of Lys182-G(13) nucleotide interaction for DevR binding and regulon induction. Our findings demonstrate that impairment of Lys182-mediated interactions alone abolishes DevR function and provide valuable insights for designing molecules that interfere with DevR-mediated dormancy adaptation.
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Affiliation(s)
- Rajesh Kumar Gupta
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, India
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115
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Movahedzadeh F, Frita R, Gutka HJ. A two-step strategy for the complementation of M. tuberculosis mutants. Genet Mol Biol 2011; 34:286-9. [PMID: 21734831 PMCID: PMC3115324 DOI: 10.1590/s1415-47572011000200020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 02/07/2011] [Indexed: 11/23/2022] Open
Abstract
The sequence of Mycobacterium tuberculosis, completed in 1998, facilitated both the development of genomic tools, and the creation of a number of mycobacterial mutants. These mutants have a wide range of phenotypes, from attenuated to hypervirulent strains. These phenotypes must be confirmed, to rule out possible secondary mutations that may arise during the generation of mutant strains. This may occur during the amplification of target genes or during the generation of the mutation, thus constructing a complementation strain, which expresses the wild-type copy of the gene in the mutant strain, becomes necessary. In this study we have introduced a two-step strategy to construct complementation strains using the Ag85 promoter. We have constitutively expressed dosR and have shown dosR expression is restored to wild-type level.
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Affiliation(s)
- Farahnaz Movahedzadeh
- Department of Pathology and Infectious Diseases, Royal Veterinary College, London, UK
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The Staphylococcus aureus KdpDE two-component system couples extracellular K+ sensing and Agr signaling to infection programming. Infect Immun 2011; 79:2154-67. [PMID: 21422185 DOI: 10.1128/iai.01180-10] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The Kdp system is widely distributed among bacteria. In Escherichia coli, the Kdp-ATPase is a high-affinity K+ uptake system and its expression is activated by the KdpDE two-component system in response to K+ limitation or salt stress. However, information about the role of this system in many bacteria still remains obscure. Here we demonstrate that KdpFABC in Staphylococcus aureus is not a major K+ transporter and that the main function of KdpDE is not associated with K+ transport but that instead it regulates transcription for a series of virulence factors through sensing external K+ concentrations, indicating that this bacterium might modulate its infectious status through sensing specific external K+ stimuli in different environments. Our results further reveal that S. aureus KdpDE is upregulated by the Agr/RNAIII system, which suggests that KdpDE may be an important virulence regulator coordinating the external K+ sensing and Agr signaling during pathogenesis in this bacterium.
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Abstract
In recent studies of human bacterial pathogens, oxidation sensing and regulation have been shown to impact very diverse pathways that extend beyond inducing antioxidant genes in the bacteria. In fact, some redox-sensitive regulatory proteins act as major regulators of bacteria's adaptability to oxidative stress, an ability that originates from immune host response as well as antibiotic stress. Such proteins play particularly important roles in pathogenic bacteria S. aureus, P. aeruginosa, and M. tuberculosis in part because reactive oxygen species and reactive nitrogen species present significant challenges for pathogens during infection. Herein, we review recent progress toward the identification and understanding of oxidation sensing and regulation in human pathogens. The newly identified redox switches in pathogens are a focus of this review. We will cover several reactive oxygen species-sensing global regulators in both gram-positive and gram-negative pathogenic bacteria in detail. The following discussion of the mechanisms that these proteins employ to sense redox signals through covalent modification of redox active amino acid residues or associated metalloprotein centers will provide further understanding of bacteria pathogenesis, antibiotic resistance, and host-pathogen interaction.
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Affiliation(s)
- Peng R Chen
- Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China.
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118
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Muttucumaru DN, Smith DA, McMinn EJ, Reese V, Coler RN, Parish T. Mycobacterium tuberculosis Rv0198c, a putative matrix metalloprotease is involved in pathogenicity. Tuberculosis (Edinb) 2011; 91:111-6. [DOI: 10.1016/j.tube.2010.11.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 10/11/2010] [Accepted: 11/27/2010] [Indexed: 11/25/2022]
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Farhana A, Guidry L, Srivastava A, Singh A, Hondalus MK, Steyn AJC. Reductive stress in microbes: implications for understanding Mycobacterium tuberculosis disease and persistence. Adv Microb Physiol 2011; 57:43-117. [PMID: 21078441 DOI: 10.1016/b978-0-12-381045-8.00002-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Mycobacterium tuberculosis (Mtb) is a remarkably successful pathogen that is capable of persisting in host tissues for decades without causing disease. Years after initial infection, the bacilli may resume growth, the outcome of which is active tuberculosis (TB). In order to establish infection, resist host defences and re-emerge, Mtb must coordinate its metabolism with the in vivo environmental conditions and nutrient availability within the primary site of infection, the lung. Maintaining metabolic homeostasis for an intracellular pathogen such as Mtb requires a carefully orchestrated series of oxidation-reduction reactions, which, if unbalanced, generate oxidative or reductive stress. The importance of oxidative stress in microbial pathogenesis has been appreciated and well studied over the past several decades. However, the role of its counterpart, reductive stress, has been largely ignored. Reductive stress is defined as an aberrant increase in reducing equivalents, the magnitude and identity of which is determined by host carbon source utilisation and influenced by the presence of host-generated gases (e.g. NO, CO, O(2) and CO(2)). This increased reductive power must be dissipated for bacterial survival. To recycle reducing equivalents, microbes have evolved unique electron 'sinks' that are distinct for their particular environmental niche. In this review, we describe the specific mechanisms that some microbes have evolved to dispel reductive stress. The intention of this review is to introduce the concept of reductive stress, in tuberculosis research in particular, in the hope of stimulating new avenues of investigation.
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Affiliation(s)
- Aisha Farhana
- Department of Microbiology, University of Alabama at Birmingham, AL, USA
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Gautam US, Chauhan S, Tyagi JS. Determinants outside the DevR C-terminal domain are essential for cooperativity and robust activation of dormancy genes in Mycobacterium tuberculosis. PLoS One 2011; 6:e16500. [PMID: 21304599 PMCID: PMC3029386 DOI: 10.1371/journal.pone.0016500] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2010] [Accepted: 01/03/2011] [Indexed: 11/23/2022] Open
Abstract
Background DevR (also called as DosR) is a two-domain response regulator of the NarL subfamily that controls dormancy adaptation of Mycobacterium tuberculosis (M. tb). In response to inducing signals such as hypoxia and ascorbic acid, the N-terminal receiver domain of DevR (DevRN) is phosphorylated at Asp54. This results in DevR binding to DNA via its C-terminal domain (DevRC) and subsequent induction of the DevR regulon. The mechanism of phosphorylation-mediated activation is not known. The present study was designed to understand the role of the N- and C-terminal domains of DevR in DevR regulon genes activation. Methodology/Principal Findings Towards deciphering the activation mechanism of DevR, we compared the DNA binding properties of DevRC and DevR and correlated the findings with their ability to activate gene expression. We show that isolated DevRC can interact with DNA, but only with the high affinity site of a representative target promoter. Therefore, one role of DevRN is to mask the intrinsic DNA binding function of DevRC. However, unlike phosphorylated DevR, isolated DevRC does not interact with the adjacent low affinity binding site suggesting that a second role of DevRN is in cooperative binding to the secondary site. Transcriptional analysis shows that consistent with unmasking of its DNA binding property, DevRC supports the aerobic induction, albeit feebly, of DevR regulon genes but is unable to sustain gene activation during hypoxia. Conclusions/Significance DevR is a unique response regulator that employs a dual activation mechanism including relief of inhibition and cooperative interaction with binding sites. Importantly, both these functions reside outside the C-terminal domain. DevRN is also essential for stabilizing DevR and sustaining autoregulation under hypoxia. Hence, both domains of DevR are required for robust transcription activation.
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Affiliation(s)
- Uma Shankar Gautam
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, Indian
| | - Santosh Chauhan
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, Indian
| | - Jaya Sivaswami Tyagi
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi, Indian
- * E-mail:
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Genes and regulatory networks involved in persistence of Mycobacterium tuberculosis. SCIENCE CHINA-LIFE SCIENCES 2011; 54:300-10. [PMID: 21267668 DOI: 10.1007/s11427-011-4134-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 09/06/2010] [Indexed: 10/18/2022]
Abstract
The causative agent of tuberculosis, Mycobacterium tuberculosis, is one of the most successful of human pathogens. It can evade the host immune response and establish a persistent infection or enter a dormant state within the host which can be reactivated if the host becomes immuno-compromised. Both of these features are major obstacles to tuberculosis eradication. Dormancy and reactivation of M. tuberculosis are tightly coordinated dynamic processes involving numerous genes and their products. Molecular mechanisms underlying M. tuberculosis persistence may provide an opportunity for the discovery of effective drug targets for tuberculosis control. Here, we review the genes required for M. tuberculosis persistence and propose a regulatory network for the action of these genes using text mining. This should provide fresh insights into the persistence mechanisms of M. tuberculosis and suggest candidates for new drug targets and immune intervention.
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122
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Analysis of transcription at the oriC locus in Mycobacterium tuberculosis. Microbiol Res 2011; 166:508-14. [PMID: 21239151 DOI: 10.1016/j.micres.2010.10.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Revised: 10/15/2010] [Accepted: 10/24/2010] [Indexed: 11/21/2022]
Abstract
Details of the mechanism of DNA replication in the slow growing pathogen Mycobacterium tuberculosis (M. tb) are unknown. The dnaA and dnaN gene products are essential for chromosome replication and growth of a bacterium. Here we analyzed the transcriptional activity at the oriC locus in M. tb that includes dnaA, dnaN and recF. dnaA and dnaN are each transcribed from a transcription start point (TSP) located at -261 bp and -113 bp, respectively. recF is co-transcribed with dnaN and both genes are co-induced in stationary phase cultures of M. tb. Transcription was also observed inside the oriC region and leftward transcription predominated over rightward transcription. The transcriptional activity of dnaA, dnaN and recF genes was found to be unchanged under all the stress conditions that were examined except during hypoxia when a ∼2-fold decrease in dnaA and dnaN transcription was observed. This analysis of transcription at the oriC locus would be useful for future studies to assess the link if any between transcription at this locus and DNA replication.
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Stallings CL, Glickman MS. Is Mycobacterium tuberculosis stressed out? A critical assessment of the genetic evidence. Microbes Infect 2010; 12:1091-101. [PMID: 20691805 PMCID: PMC3587153 DOI: 10.1016/j.micinf.2010.07.014] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 07/27/2010] [Indexed: 11/17/2022]
Abstract
Mycobacterium tuberculosis is an obligate human intracellular pathogen which remains a major killer worldwide. A remarkable feature of M. tuberculosis infection is the ability of the pathogen to persist within the host for decades despite an impressive onslaught of stresses. In this review we seek to outline the host-inflicted stresses experienced by M. tuberculosis, the bacterial strategies used to withstand these stresses, and how this information should guide our efforts to combat this global pathogen.
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Affiliation(s)
- Christina L Stallings
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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124
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Kinnings SL, Xie L, Fung KH, Jackson RM, Xie L, Bourne PE. The Mycobacterium tuberculosis drugome and its polypharmacological implications. PLoS Comput Biol 2010; 6:e1000976. [PMID: 21079673 PMCID: PMC2973814 DOI: 10.1371/journal.pcbi.1000976] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 09/24/2010] [Indexed: 11/26/2022] Open
Abstract
We report a computational approach that integrates structural bioinformatics, molecular modelling and systems biology to construct a drug-target network on a structural proteome-wide scale. The approach has been applied to the genome of Mycobacterium tuberculosis (M.tb), the causative agent of one of today's most widely spread infectious diseases. The resulting drug-target interaction network for all structurally characterized approved drugs bound to putative M.tb receptors, we refer to as the ‘TB-drugome’. The TB-drugome reveals that approximately one-third of the drugs examined have the potential to be repositioned to treat tuberculosis and that many currently unexploited M.tb receptors may be chemically druggable and could serve as novel anti-tubercular targets. Furthermore, a detailed analysis of the TB-drugome has shed new light on the controversial issues surrounding drug-target networks [1]–[3]. Indeed, our results support the idea that drug-target networks are inherently modular, and further that any observed randomness is mainly caused by biased target coverage. The TB-drugome (http://funsite.sdsc.edu/drugome/TB) has the potential to be a valuable resource in the development of safe and efficient anti-tubercular drugs. More generally the methodology may be applied to other pathogens of interest with results improving as more of their structural proteomes are determined through the continued efforts of structural biology/genomics. The worldwide increase in multi-drug resistant TB poses a great threat to human health and highlights the need to identify new anti-tubercular agents. We have developed a computational strategy to link the structural proteome of Mycobacterium tuberculosis, the causative agent of tuberculosis, to all structurally characterized approved drugs, and hence construct a proteome-wide drug-target network – the TB-drugome. The TB-drugome has the potential to be a valuable resource in the development of safe and efficient anti-tubercular drugs. More generally, the proteome-wide and multi-scale view of target and drug space may facilitate a systematic drug discovery process, which concurrently takes into account the disease mechanism and druggability of targets, the drug-likeness and ADMET properties of chemical compounds, and the genetic dispositions of individuals. Ultimately it may help to reduce the high attrition rate in drug development through a better understanding of drug-receptor interactions on a large scale.
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Affiliation(s)
- Sarah L. Kinnings
- Institute of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
- San Diego Supercomputer Center, University of California, San Diego, La Jolla, California, United States of America
| | - Li Xie
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California, United States of America
| | - Kingston H. Fung
- Bioinformatics Program, University of California, San Diego, La Jolla, California, United States of America
| | - Richard M. Jackson
- Institute of Molecular and Cellular Biology and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Lei Xie
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California, United States of America
- * E-mail: (LX); (PEB)
| | - Philip E. Bourne
- San Diego Supercomputer Center, University of California, San Diego, La Jolla, California, United States of America
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California, United States of America
- * E-mail: (LX); (PEB)
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125
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Kendall SL, Frita R. Construction of targeted mycobacterial mutants by homologous recombination. Methods Mol Biol 2010; 465:297-310. [PMID: 20560068 DOI: 10.1007/978-1-59745-207-6_20] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The ability to select genes to knock out of mycobacterial genomes has greatly improved our understanding of mycobacteria. This chapter describes a method for doing this. The gene (including a 1-kb flanking region) is cloned into a pNIL series vector and disrupted by deletion or insertion of a cassette. A selection of marker genes obtained from the pGOAL series of vectors are inserted into the pNIL vector to create a suicide delivery system. This delivery vector is introduced into mycobacteria where the disrupted version of the gene replaces the wild-type version by a two-step homologous recombination process. The method involves selecting for a single crossover event followed by selection of double crossovers. Single crossovers have incorporated plasmid marker genes and are sucrose(S), kanamycin(R) and blue on media containing X-gal. Double crossovers have lost plasmid markers and are sucrose(R), kanamycin(S) and white on media containing X-gal.
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Affiliation(s)
- Sharon L Kendall
- Department of Pathology and Infectious Diseases, The Royal Veterinary College, Royal College Street, London NW1 OTU, UK.
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126
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Li Y, Zeng J, Zhang H, He ZG. The characterization of conserved binding motifs and potential target genes for M. tuberculosis MtrAB reveals a link between the two-component system and the drug resistance of M. smegmatis. BMC Microbiol 2010; 10:242. [PMID: 20843371 PMCID: PMC2945938 DOI: 10.1186/1471-2180-10-242] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Accepted: 09/16/2010] [Indexed: 01/18/2023] Open
Abstract
Background The two-component systems of Mycobacterium tuberculosis are apparently required for its growth and resistance in hostile host environments. In such environments, MtrAB has been reported to regulate the expression of the M. tuberculosis replication initiator gene, dnaA. However, the dnaA promoter binding sites and many potential target genes for MtrA have yet to be precisely characterized. Results In this study, a 7 bp sequence motif in the dnaA promoter region was identified for MtrA binding using DNaseI footprinting assays and surface plasmon resonance (SPR) analysis. Approximately 420 target genes potentially regulated by MtrA, including the isoniazid inducible gene iniB, were further characterized from M. tuberculosis and M. smegmatis genomes. When assayed using quantitative real-time PCR (qRT-PCR), many of the target genes demonstrated significant expression changes when the antisense mRNA of the mtrA gene was expressed in M. smegmatis. The recombinant mycobacteria grew in length and were more sensitive to two anti-tuberculosis drugs, isoniazid and streptomycin. Conclusions These findings yield critical information about the regulatory mechanisms of the MtrAB two-component system and its role in the drug resistance of M. smegmatis.
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Affiliation(s)
- Yuqing Li
- National Key Laboratory of Agricultural Microbiology, Center for Proteomics Research, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
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127
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Li Y, Zeng J, He ZG. Characterization of a functional C-terminus of the Mycobacterium tuberculosis MtrA responsible for both DNA binding and interaction with its two-component partner protein, MtrB. J Biochem 2010; 148:549-56. [PMID: 20671191 DOI: 10.1093/jb/mvq082] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Virulence in pathogenic bacteria is due in part to the action of two-component systems. However, in the human pathogen Mycobacterium tuberculosis, the molecular mechanisms underlying these systems are as yet unclear. In this study, MtrA was shown to contain a functional C-terminus and also to have Ca(2+) as its preferred cofactor for DNA binding. Further mutation experiments demonstrated that the C-terminus of MtrA was responsible for specific interactions with the target DNA motif and also with its partner protein, MtrB. The physical interaction between MtrA and MtrB inhibited DNA binding by MtrA. These findings yield critical information about the unique regulatory mechanisms of the essential MtrAB two-component system in this pathogen.
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Affiliation(s)
- Yuqing Li
- National Key Laboratory of Agricultural Microbiology, Center for Proteomics Research, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
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128
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Balhana R, Stoker NG, Sikder MH, Chauviac FX, Kendall SL. Rapid construction of mycobacterial mutagenesis vectors using ligation-independent cloning. J Microbiol Methods 2010; 83:34-41. [PMID: 20650290 PMCID: PMC2941038 DOI: 10.1016/j.mimet.2010.07.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 07/08/2010] [Accepted: 07/12/2010] [Indexed: 10/25/2022]
Abstract
Targeted mutagenesis is one of the major tools for determining the function of a given gene and its involvement in bacterial pathogenesis. In mycobacteria, gene deletion is often accomplished by using allelic exchange techniques that commonly utilise a suicide delivery vector. We have adapted a widely-used suicide delivery vector (p1NIL) for cloning two flanking regions of a gene using ligation independent cloning (LIC). The pNILRB plasmid series produced allow a faster, more efficient and less laborious cloning procedure. In this paper we describe the making of pNILRB5, a modified version of p1NIL that contains two pairs of LIC sites flanking either a sacB or a lacZ gene. We demonstrate the success of this technique by generating 3 mycobacterial mutant strains. These vectors will contribute to more high-throughput methods of mutagenesis.
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Affiliation(s)
- Ricardo Balhana
- Department of Pathology and Infectious Diseases, The Royal Veterinary College, Centre for Emerging, Endemic and Exotic Disease, Hawkshead Lane, Hertfordshire, AL9 7TA, United Kingdom
| | - Neil G. Stoker
- Department of Pathology and Infectious Diseases, The Royal Veterinary College, Centre for Emerging, Endemic and Exotic Disease, Hawkshead Lane, Hertfordshire, AL9 7TA, United Kingdom
| | - Mahmudul Hasan Sikder
- Department of Pathology and Infectious Diseases, The Royal Veterinary College, Centre for Emerging, Endemic and Exotic Disease, Hawkshead Lane, Hertfordshire, AL9 7TA, United Kingdom
| | | | - Sharon L. Kendall
- Department of Pathology and Infectious Diseases, The Royal Veterinary College, Centre for Emerging, Endemic and Exotic Disease, Hawkshead Lane, Hertfordshire, AL9 7TA, United Kingdom
- Corresponding author. Tel.: +44 1707 666333x7058.
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129
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Chao JD, Papavinasasundaram KG, Zheng X, Chávez-Steenbock A, Wang X, Lee GQ, Av-Gay Y. Convergence of Ser/Thr and two-component signaling to coordinate expression of the dormancy regulon in Mycobacterium tuberculosis. J Biol Chem 2010; 285:29239-46. [PMID: 20630871 DOI: 10.1074/jbc.m110.132894] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signal transduction in Mycobacterium tuberculosis is mediated primarily by the Ser/Thr protein kinases and the two-component systems. The Ser/Thr kinase PknH has been shown to regulate growth of M. tuberculosis in a mouse model and in response to NO stress in vitro. Comparison of a pknH deletion mutant (ΔpknH) with its parental M. tuberculosis H37Rv strain using iTRAQ enabled us to quantify >700 mycobacterial proteins. Among these, members of the hypoxia- and NO-inducible dormancy (DosR) regulon were disregulated in the ΔpknH mutant. Using kinase assays, protein-protein interactions, and mass spectrometry analysis, we demonstrated that the two-component response regulator DosR is a substrate of PknH. PknH phosphorylation of DosR mapped to Thr(198) and Thr(205) on the key regulatory helix α10 involved in activation and dimerization of DosR. PknH Thr phosphorylation and DosS Asp phosphorylation of DosR cooperatively enhanced DosR binding to cognate DNA sequences. Transcriptional analysis comparing ΔpknH and parental M. tuberculosis revealed that induction of the DosR regulon was subdued in the ΔpknH mutant in response to NO. Together, these results indicate that PknH phosphorylation of DosR is required for full induction of the DosR regulon and demonstrate convergence of the two major signal transduction systems for the first time in M. tuberculosis.
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Affiliation(s)
- Joseph D Chao
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V5Z 3J5, Canada
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130
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Staphylococcus aureus AI-2 quorum sensing associates with the KdpDE two-component system to regulate capsular polysaccharide synthesis and virulence. Infect Immun 2010; 78:3506-15. [PMID: 20498265 DOI: 10.1128/iai.00131-10] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Autoinducer 2 (AI-2) is widely recognized as a signal molecule for intra- and interspecies communication in Gram-negative bacteria, but its signaling function in Gram-positive bacteria, especially in Staphylococcus aureus, remains obscure. Here we reveal the role of LuxS in the regulation of capsular polysaccharide synthesis in S. aureus NCTC8325 and show that AI-2 can regulate gene expression and is involved in some physiological activities in S. aureus as a signaling molecule. Inactivation of luxS in S. aureus NCTC8325 resulted in higher levels of transcription of capsular polysaccharide synthesis genes. The survival rate of the luxS mutant was higher than that of the wild type in both human blood and U937 macrophages. In comparison to the luxS mutant, a culture supplemented with chemically synthesized 4,5-dihydroxy-2,3-pentanedione (DPD), the AI-2 precursor molecule, restored all the parental phenotypes, suggesting that AI-2 has a signaling function in S. aureus. Furthermore, we demonstrated that the LuxS/AI-2 signaling system regulates capsular polysaccharide production via a two-component system, KdpDE, whose function has not yet been clarified in S. aureus. This regulation occurred via the phosphorylation of KdpE binding to the cap promoter.
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131
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Variation among genome sequences of H37Rv strains of Mycobacterium tuberculosis from multiple laboratories. J Bacteriol 2010; 192:3645-53. [PMID: 20472797 DOI: 10.1128/jb.00166-10] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The publication of the complete genome sequence for Mycobacterium tuberculosis H37Rv in 1998 has had a great impact on the research community. Nonetheless, it is suspected that genetic differences have arisen in stocks of H37Rv that are maintained in different laboratories. In order to assess the consistency of the genome sequences among H37Rv strains in use and the extent to which they have diverged from the original strain sequenced, we carried out whole-genome sequencing on six strains of H37Rv from different laboratories. Polymorphisms at 73 sites were observed, which were shared among the lab strains, though 72 of these were also shared with H37Ra and are likely to be due to sequencing errors in the original H37Rv reference sequence. An updated H37Rv genome sequence should be valuable to the tuberculosis research community as well as the broader microbial research community. In addition, several polymorphisms unique to individual strains and several shared polymorphisms were identified and shown to be consistent with the known provenance of these strains. Aside from nucleotide substitutions and insertion/deletions, multiple IS6110 transposition events were observed, supporting the theory that they play a significant role in plasticity of the M. tuberculosis genome. This genome-wide catalog of genetic differences can help explain any phenotypic differences that might be found, including a frameshift mutation in the mycocerosic acid synthase gene which causes two of the strains to be deficient in biosynthesis of the surface glycolipid phthiocerol dimycocerosate (PDIM). The resequencing of these six lab strains represents a fortuitous "in vitro evolution" experiment that demonstrates how the M. tuberculosis genome continues to evolve even in a controlled environment.
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Co-expression of DevR and DevR(N)-Aph proteins is associated with hypoxic adaptation defect and virulence attenuation of Mycobacterium tuberculosis. PLoS One 2010; 5:e9448. [PMID: 20195478 PMCID: PMC2829086 DOI: 10.1371/journal.pone.0009448] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Accepted: 02/04/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The DevR response regulator is implicated in both hypoxic adaptation and virulence of Mycobacterium tuberculosis (M. tb). DevR regulon genes are powerfully induced in vivo implicating them in bacterial adaptation to host control strategies. A better understanding of DevR function will illumine the way for new strategies to control and treat tuberculosis. METHODOLOGY/PRINCIPAL FINDINGS Towards this objective, we used a combination of genetic, microbiological, biochemical, cell biological tools and a guinea pig virulence assay to compare the hypoxic adaptation and virulence properties of two novel M. tb strains, namely, a devR disruption mutant, Mut1, that expresses C-terminal truncated N-terminal domain of DevR (DevR(NTD)) as a fusion protein with AphI (DevR(N)-Kan), and its complemented strain, Comp1, that expresses intact DevR along with DevR(N)-Kan. Comp1 bacteria exhibit a defect in DevR-mediated phosphosignalling, hypoxic induction of HspX and also hypoxic survival. In addition, we find that Comp1 is attenuated in virulence in guinea pigs and shows decreased infectivity of THP-1 cells. While Mut1 bacilli are also defective in hypoxic adaptation and early growth in spleen, they exhibit an overall virulence comparable to that of wild-type bacteria. CONCLUSIONS/SIGNIFICANCE The hypoxic defect of Comp1 is associated to a defect in DevR expression level. The demonstrated repression of DevR function by DevR(N)-Kan suggests that such a knockdown approach could be useful for evaluating the activity of DevRS and other two-component signaling pathways. Further investigation is necessary to elucidate the mechanism underlying Comp1 attenuation.
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de Souza GA, Fortuin S, Aguilar D, Pando RH, McEvoy CRE, van Helden PD, Koehler CJ, Thiede B, Warren RM, Wiker HG. Using a label-free proteomics method to identify differentially abundant proteins in closely related hypo- and hypervirulent clinical Mycobacterium tuberculosis Beijing isolates. Mol Cell Proteomics 2010; 9:2414-23. [PMID: 20190197 PMCID: PMC2984234 DOI: 10.1074/mcp.m900422-mcp200] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Although the genome of the Mycobacterium tuberculosis H37Rv laboratory strain has been available for over 10 years, it is only recently that genomic information from clinical isolates has been used to generate the hypothesis of virulence differences between different strains. In addition, the relationship between strains displaying differing virulence in an epidemiological setting and their behavior in animal models has received little attention. The potential causes for variation in virulence between strains, as determined by differential protein expression, have similarly been a neglected area of investigation. In this study, we used a label-free quantitative proteomics approach to estimate differences in protein abundance between two closely related Beijing genotypes that have been shown to be hyper- and hypovirulent on the basis of both epidemiological and mouse model studies. We were able to identify a total of 1668 proteins from both samples, and protein abundance calculations revealed that 48 proteins were over-represented in the hypovirulent isolate, whereas 53 were over-represented in the hypervirulent. Functional classification of these results shows that molecules of cell wall organization and DNA transcription regulatory proteins may have a critical influence in defining the level of virulence. The reduction in the presence of ESAT-6, other Esx-like proteins, and FbpD (MPT51) in the hypervirulent strain indicates that changes in the repertoire of highly immunogenic proteins can be a defensive process undertaken by the virulent cell. In addition, most of the previously well characterized gene targets related to virulence were found to be similarly expressed in our model. Our data support the use of proteomics as a complementary tool for genomic comparisons to understand the biology of M. tuberculosis virulence.
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Affiliation(s)
- Gustavo A de Souza
- Section for Microbiology and Immunology, The Gade Institute, University of Bergen, Bergen, Norway
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Strains of the East Asian (W/Beijing) lineage of Mycobacterium tuberculosis are DosS/DosT-DosR two-component regulatory system natural mutants. J Bacteriol 2010; 192:2228-38. [PMID: 20154135 DOI: 10.1128/jb.01597-09] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
As part of our ongoing efforts to uncover the phenotypic consequences of genetic variability among clinical Mycobacterium tuberculosis isolates, we previously reported that isolates of the "East Asian" or "W/Beijing" lineage constitutively overexpress the coordinately regulated transcriptional program known as the DosR regulon under standard in vitro conditions. This phenotype distinguishes the W/Beijing lineage from all other M. tuberculosis lineages, which normally induce expression of this regulon only once exposed to low oxygen or nitric oxide, both of which result in inhibition of bacterial respiration and replication. Transcription of the DosR regulon is controlled through a two-component regulatory system comprising the transcription factor DosR and two possible cognate histidine sensor kinases, DosS and DosT. Through sequence analysis of a carefully selected set of isolates representing each of the major M. tuberculosis lineages, we describe herein a naturally occurring frameshift mutation in the gene encoding the DosT sensor kinase for isolates of the most recently evolved W/Beijing sublineages. Intriguingly, the occurrence of the frameshift mutation correlates precisely with the appearance of the constitutive DosR regulon phenotype displayed by the same "modern" W/Beijing strains. However, complementation studies have revealed that the mutation in dosT alone is not directly responsible for the constitutive DosR regulon phenotype. Our data serve to highlight the evolutionary pressure that exists among distinct M. tuberculosis lineages to maintain tight control over DosR regulon expression.
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135
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The Mycobacterium tuberculosis DosR regulon assists in metabolic homeostasis and enables rapid recovery from nonrespiring dormancy. J Bacteriol 2009; 192:1662-70. [PMID: 20023019 DOI: 10.1128/jb.00926-09] [Citation(s) in RCA: 198] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis survives in latently infected individuals, likely in a nonreplicating or dormancy-like state. The M. tuberculosis DosR regulon is a genetic program induced by conditions that inhibit aerobic respiration and prevent bacillus replication. In this study, we used a mutant incapable of DosR regulon induction to investigate the contribution of this regulon to bacterial metabolism during anaerobic dormancy. Our results confirm that the DosR regulon is essential for M. tuberculosis survival during anaerobic dormancy and demonstrate that it is required for metabolic processes that occur upon entry into and throughout the dormant state. Specifically, we showed that regulon mechanisms shift metabolism away from aerobic respiration in the face of dwindling oxygen availability and are required for maintaining energy levels and redox balance as the culture becomes anaerobic. We also demonstrated that the DosR regulon is crucial for rapid resumption of growth once M. tuberculosis exits an anaerobic or nitric oxide-induced nonrespiring state. In summary, the DosR regulon encodes novel metabolic mechanisms essential for M. tuberculosis to survive in the absence of respiration and to successfully transition rapidly between respiring and nonrespiring conditions without loss of viability.
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Cook GM, Berney M, Gebhard S, Heinemann M, Cox RA, Danilchanka O, Niederweis M. Physiology of mycobacteria. Adv Microb Physiol 2009; 55:81-182, 318-9. [PMID: 19573696 DOI: 10.1016/s0065-2911(09)05502-7] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mycobacterium tuberculosis is a prototrophic, metabolically flexible bacterium that has achieved a spread in the human population that is unmatched by any other bacterial pathogen. The success of M. tuberculosis as a pathogen can be attributed to its extraordinary stealth and capacity to adapt to environmental changes throughout the course of infection. These changes include: nutrient deprivation, hypoxia, various exogenous stress conditions and, in the case of the pathogenic species, the intraphagosomal environment. Knowledge of the physiology of M. tuberculosis during this process has been limited by the slow growth of the bacterium in the laboratory and other technical problems such as cell aggregation. Advances in genomics and molecular methods to analyze the M. tuberculosis genome have revealed that adaptive changes are mediated by complex regulatory networks and signals, resulting in temporal gene expression coupled to metabolic and energetic changes. An important goal for bacterial physiologists will be to elucidate the physiology of M. tuberculosis during the transition between the diverse conditions encountered by M. tuberculosis. This review covers the growth of the mycobacterial cell and how environmental stimuli are sensed by this bacterium. Adaptation to different environments is described from the viewpoint of nutrient acquisition, energy generation, and regulation. To gain quantitative understanding of mycobacterial physiology will require a systems biology approach and recent efforts in this area are discussed.
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Affiliation(s)
- Gregory M Cook
- Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand
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Powerful induction of divergent tgs1-Rv3131 genes in Mycobacterium tuberculosis is mediated by DevR interaction with a high-affinity site and an adjacent cryptic low-affinity site. J Bacteriol 2009; 191:6075-81. [PMID: 19648251 DOI: 10.1128/jb.00310-09] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DevR activates the transcription of approximately 48 genes in response to hypoxia and other stresses and triggers metabolic downshift and dormancy development in Mycobacterium tuberculosis. tgs1 and Rv3131 encode triacylglycerol synthase and a putative nitroreductase, respectively, and both are members of the DevR regulon. This study aimed to understand how a single putative DevR binding site identified previously could sustain powerful induction of divergent tgs1-Rv3131 genes. DNase I footprinting revealed that phosphorylated DevR in fact binds to two sites symmetrically located at -42.5 and -63.5 bp from transcription start points of both genes. DevR first bound to the high-affinity site, P, and cooperatively recruited another DevR molecule to the secondary low-affinity site, S, to activate tgs1-Rv3131 transcription by approximately 210- and approximately 110-fold, respectively. The presence of a single P site significantly reduced activation of tgs1 expression and abolished Rv3131 activity, reinforcing the requirement of two binding sites for robust expression in both directions. P site inversion abolished tgs1 but not Rv3131 transcription despite DevR occupancy at both sites. The lack of tgs1 expression is most likely due to disruption of its -35 promoter element rather than inversion of the binding site per se. We conclude that (i) an overlap of a DevR binding site and -35 sequence is indispensable for promoter activation, (ii) DevR interaction with two binding sites is obligatory for synergistic activation of tgs1-Rv3131 promoters, and (iii) DevR interaction with binding sites of different affinities offers scope for temporal and differential expression of target genes.
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Bartek IL, Rutherford R, Gruppo V, Morton RA, Morris RP, Klein MR, Visconti KC, Ryan GJ, Schoolnik GK, Lenaerts A, Voskuil MI. The DosR regulon of M. tuberculosis and antibacterial tolerance. Tuberculosis (Edinb) 2009; 89:310-6. [PMID: 19577518 DOI: 10.1016/j.tube.2009.06.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 05/22/2009] [Accepted: 06/01/2009] [Indexed: 10/20/2022]
Abstract
Adaptation of Mycobacterium tuberculosis to an anaerobic dormant state that is tolerant to several antibacterials is mediated largely by a set of highly expressed genes controlled by DosR. A DosR mutant was constructed to investigate whether the DosR regulon is involved in antibacterial tolerance. We demonstrate that induction of the regulon is not required for drug tolerance either in vivo during a mouse infection or in vitro during anaerobic dormancy. Thus, drug tolerance observed in these models is due to other mechanisms such as the bacilli simply being in a non-replicating or low metabolic state. Our data also demonstrate that the DosR regulon is not essential for virulence during chronic murine infection. However, decreased lung pathology was observed in the DosR mutant. We also show that the DosR regulon genes are more highly conserved in environmental mycobacteria, than in pathogenic mycobacteria lacking a latent phase or environmental reservoir. It is possible that the DosR regulon could contribute to drug tolerance in human infections; however, it is not the only mechanism and not the primary mechanism for tolerance during a mouse infection. These data suggest that the regulon evolved not for pathogenesis or drug tolerance but for adaptation to anaerobic conditions in the environment and has been adapted by M. tuberculosis for survival during latent infection.
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Affiliation(s)
- I L Bartek
- Department of Microbiology, School of Medicine, University of Colorado Denver, P18-9115, 12800 East 19th Avenue, PO Box 6511, Aurora, CO 80045, USA
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Gopalaswamy R, Narayanan S, Chen B, Jacobs WR, Av-Gay Y. The serine/threonine protein kinase PknI controls the growth ofMycobacterium tuberculosisupon infection. FEMS Microbiol Lett 2009; 295:23-9. [DOI: 10.1111/j.1574-6968.2009.01570.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Drumm JE, Mi K, Bilder P, Sun M, Lim J, Bielefeldt-Ohmann H, Basaraba R, So M, Zhu G, Tufariello JM, Izzo AA, Orme IM, Almo SC, Leyh TS, Chan J. Mycobacterium tuberculosis universal stress protein Rv2623 regulates bacillary growth by ATP-Binding: requirement for establishing chronic persistent infection. PLoS Pathog 2009; 5:e1000460. [PMID: 19478878 PMCID: PMC2682197 DOI: 10.1371/journal.ppat.1000460] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2008] [Accepted: 04/30/2009] [Indexed: 01/20/2023] Open
Abstract
Tuberculous latency and reactivation play a significant role in the pathogenesis of tuberculosis, yet the mechanisms that regulate these processes remain unclear. The Mycobacterium tuberculosisuniversal stress protein (USP) homolog, rv2623, is among the most highly induced genes when the tubercle bacillus is subjected to hypoxia and nitrosative stress, conditions thought to promote latency. Induction of rv2623 also occurs when M. tuberculosis encounters conditions associated with growth arrest, such as the intracellular milieu of macrophages and in the lungs of mice with chronic tuberculosis. Therefore, we tested the hypothesis that Rv2623 regulates tuberculosis latency. We observed that an Rv2623-deficient mutant fails to establish chronic tuberculous infection in guinea pigs and mice, exhibiting a hypervirulence phenotype associated with increased bacterial burden and mortality. Consistent with this in vivo growth-regulatory role, constitutive overexpression of rv2623 attenuates mycobacterial growth in vitro. Biochemical analysis of purified Rv2623 suggested that this mycobacterial USP binds ATP, and the 2.9-Å-resolution crystal structure revealed that Rv2623 engages ATP in a novel nucleotide-binding pocket. Structure-guided mutagenesis yielded Rv2623 mutants with reduced ATP-binding capacity. Analysis of mycobacteria overexpressing these mutants revealed that the in vitro growth-inhibitory property of Rv2623 correlates with its ability to bind ATP. Together, the results indicate that i) M. tuberculosis Rv2623 regulates mycobacterial growth in vitro and in vivo, and ii) Rv2623 is required for the entry of the tubercle bacillus into the chronic phase of infection in the host; in addition, iii) Rv2623 binds ATP; and iv) the growth-regulatory attribute of this USP is dependent on its ATP-binding activity. We propose that Rv2623 may function as an ATP-dependent signaling intermediate in a pathway that promotes persistent infection. Mycobacterium tuberculosis poses serious threats to public health worldwide. The ability of this pathogen to establish in the host a clinically silent, persistent latent infection that can subsequently reactivate to cause diseases constitutes a major challenge in controlling tuberculosis. Our study showed that an M. tuberculosis mutant that is deficient in a universal stress protein (USP) designated Rv2623 fails to establish a chronic persistent infection in animal hosts. The mutant strain exhibits a hypervirulent phenotype as assessed by increased bacillary growth, pathology, and mortality in infected animals relative to the parental strain. Consistent with this in vivo growth-regulating attribute, we demonstrated that Rv2623, when expressed in mycobacteria at levels higher than that of the wild-type strain, retards bacterial growth in vitro. Using biochemical and biophysical analyses, including the Rv2623 crystal structure, we showed that this USP binds to ATP within a novel ATP-binding pocket. Through targeted mutagenesis studies, we further determined that the ability of Rv2623 to regulate bacillary growth is dependent on its ATP-binding capacity. Our data strongly suggest Rv2623 as a critical component that regulates the entry of M. tuberculosis into a chronic persistent growth phase, and therefore provide valuable insight into tuberculous dormancy and uncover new opportunities for the development of novel anti-tuberculous therapies.
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Affiliation(s)
- Joshua E. Drumm
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Kaixia Mi
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Patrick Bilder
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Physiology & Biophysics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Meihao Sun
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Jihyeon Lim
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Helle Bielefeldt-Ohmann
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Randall Basaraba
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Melvin So
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Guofeng Zhu
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - JoAnn M. Tufariello
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Angelo A. Izzo
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Ian M. Orme
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Steve C. Almo
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Physiology & Biophysics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Thomas S. Leyh
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - John Chan
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail:
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Champion MD, Zeng Q, Nix EB, Nano FE, Keim P, Kodira CD, Borowsky M, Young S, Koehrsen M, Engels R, Pearson M, Howarth C, Larson L, White J, Alvarado L, Forsman M, Bearden SW, Sjöstedt A, Titball R, Michell SL, Birren B, Galagan J. Comparative genomic characterization of Francisella tularensis strains belonging to low and high virulence subspecies. PLoS Pathog 2009; 5:e1000459. [PMID: 19478886 PMCID: PMC2682660 DOI: 10.1371/journal.ppat.1000459] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Accepted: 04/29/2009] [Indexed: 01/15/2023] Open
Abstract
Tularemia is a geographically widespread, severely debilitating, and occasionally lethal disease in humans. It is caused by infection by a gram-negative bacterium, Francisella tularensis. In order to better understand its potency as an etiological agent as well as its potential as a biological weapon, we have completed draft assemblies and report the first complete genomic characterization of five strains belonging to the following different Francisella subspecies (subsp.): the F. tularensis subsp. tularensis FSC033, F. tularensis subsp. holarctica FSC257 and FSC022, and F. tularensis subsp. novicida GA99-3548 and GA99-3549 strains. Here, we report the sequencing of these strains and comparative genomic analysis with recently available public Francisella sequences, including the rare F. tularensis subsp. mediasiatica FSC147 strain isolate from the Central Asian Region. We report evidence for the occurrence of large-scale rearrangement events in strains of the holarctica subspecies, supporting previous proposals that further phylogenetic subdivisions of the Type B clade are likely. We also find a significant enrichment of disrupted or absent ORFs proximal to predicted breakpoints in the FSC022 strain, including a genetic component of the Type I restriction-modification defense system. Many of the pseudogenes identified are also disrupted in the closely related rarely human pathogenic F. tularensis subsp. mediasiatica FSC147 strain, including modulator of drug activity B (mdaB) (FTT0961), which encodes a known NADPH quinone reductase involved in oxidative stress resistance. We have also identified genes exhibiting sequence similarity to effectors of the Type III (T3SS) and components of the Type IV secretion systems (T4SS). One of the genes, msrA2 (FTT1797c), is disrupted in F. tularensis subsp. mediasiatica and has recently been shown to mediate bacterial pathogen survival in host organisms. Our findings suggest that in addition to the duplication of the Francisella Pathogenicity Island, and acquisition of individual loci, adaptation by gene loss in the more recently emerged tularensis, holarctica, and mediasiatica subspecies occurred and was distinct from evolutionary events that differentiated these subspecies, and the novicida subspecies, from a common ancestor. Our findings are applicable to future studies focused on variations in Francisella subspecies pathogenesis, and of broader interest to studies of genomic pathoadaptation in bacteria.
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Affiliation(s)
- Mia D Champion
- Microbial Analysis Group, Broad Institute of MIT and Harvard, Cambridge, MA, USA.
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Rustad TR, Sherrid AM, Minch KJ, Sherman DR. Hypoxia: a window into Mycobacterium tuberculosis latency. Cell Microbiol 2009; 11:1151-9. [PMID: 19388905 DOI: 10.1111/j.1462-5822.2009.01325.x] [Citation(s) in RCA: 183] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tuberculosis is a massive public health problem on a global scale and the success of Mycobacterium tuberculosis is linked to its ability to persist within humans for long periods without causing any overt disease symptoms. Hypoxia is predicted to be a key host-induced stress limiting growth of the pathogen in vivo. However, multiple studies in vitro and in vivo indicate that M. tuberculosis adapts to oxygen limitation by entering into a metabolically altered state, while awaiting the opportunity to reactivate. Molecular signatures of bacteria adapted to hypoxia in vitro are accumulating, although correlations to human disease are only now being established. Similarly, defining the mechanisms that control this adaptation is an active area of research. In this review we discuss the historical precedents linking hypoxia and latency, and the gathering knowledge of M. tuberculosis hypoxic responses. We also examine the role of these responses in tuberculosis latency, and identify promising avenues for future studies.
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Affiliation(s)
- Tige R Rustad
- Seattle Biomedical Research Institute, Seattle, WA, USA
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143
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Converse PJ, Karakousis PC, Klinkenberg LG, Kesavan AK, Ly LH, Allen SS, Grosset JH, Jain SK, Lamichhane G, Manabe YC, McMurray DN, Nuermberger EL, Bishai WR. Role of the dosR-dosS two-component regulatory system in Mycobacterium tuberculosis virulence in three animal models. Infect Immun 2009; 77:1230-7. [PMID: 19103767 PMCID: PMC2643651 DOI: 10.1128/iai.01117-08] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2008] [Revised: 10/11/2008] [Accepted: 12/14/2008] [Indexed: 11/20/2022] Open
Abstract
The Mycobacterium tuberculosis dosR gene (Rv3133c) is part of an operon, Rv3134c-Rv3132c, and encodes a response regulator that has been shown to be upregulated by hypoxia and other in vitro stress conditions and may be important for bacterial survival within granulomatous lesions found in tuberculosis. DosR is activated in response to hypoxia and nitric oxide by DosS (Rv3132c) or DosT (Rv2027c). We compared the virulence levels of an M. tuberculosis dosR-dosS deletion mutant (DeltadosR-dosS [DeltadosR-S]), a dosR-complemented strain, and wild-type H37Rv in rabbits, guinea pigs, and mice infected by the aerosol route and in a mouse hollow-fiber model that may mimic in vivo granulomatous conditions. In the mouse and the guinea pig models, the DeltadosR-S mutant exhibited a growth defect. In the rabbit, the DeltadosR-S mutant did not replicate more than the wild type. In the hollow-fiber model, the mutant phenotype was not different from that of the wild-type strain. Our analyses reveal that the dosR and dosS genes are required for full virulence and that there may be differences in the patterns of attenuation of this mutant between the animal models studied.
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Affiliation(s)
- Paul J Converse
- Center for Tuberculosis Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
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Zhu X, Chang S, Fang K, Cui S, Liu J, Wu Z, Yu X, Gao GF, Yang H, Zhu B, Wang J. MyBASE: a database for genome polymorphism and gene function studies of Mycobacterium. BMC Microbiol 2009; 9:40. [PMID: 19228437 PMCID: PMC2656513 DOI: 10.1186/1471-2180-9-40] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Accepted: 02/20/2009] [Indexed: 01/09/2023] Open
Abstract
Background Mycobacterial pathogens are a major threat to humans. With the increasing availability of functional genomic data, research on mycobacterial pathogenesis and subsequent control strategies will be greatly accelerated. It has been suggested that genome polymorphisms, namely large sequence polymorphisms, can influence the pathogenicity of different mycobacterial strains. However, there is currently no database dedicated to mycobacterial genome polymorphisms with functional interpretations. Description We have developed a mycobacterial database (MyBASE) housing genome polymorphism data and gene functions to provide the mycobacterial research community with a useful information resource and analysis platform. Whole genome comparison data produced by our lab and the novel genome polymorphisms identified were deposited into MyBASE. Extensive literature review of genome polymorphism data, mainly large sequence polymorphisms (LSPs), operon predictions and curated annotations of virulence and essentiality of mycobacterial genes are unique features of MyBASE. Large-scale genomic data integration from public resources makes MyBASE a comprehensive data warehouse useful for current research. All data is cross-linked and can be graphically viewed via a toolbox in MyBASE. Conclusion As an integrated platform focused on the collection of experimental data from our own lab and published literature, MyBASE will facilitate analysis of genome structure and polymorphisms, which will provide insight into genome evolution. Importantly, the database will also facilitate the comparison of virulence factors among various mycobacterial strains. MyBASE is freely accessible via http://mybase.psych.ac.cn.
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Affiliation(s)
- Xinxing Zhu
- Behavioral Genetics Center, Institute of Psychology, Chinese Academy of Sciences, Beijing, PR China.
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Alvarez AH, Estrada-Chávez C, Flores-Valdez MA. Molecular findings and approaches spotlighting Mycobacterium bovis persistence in cattle. Vet Res 2009; 40:22. [PMID: 19220975 PMCID: PMC2695034 DOI: 10.1051/vetres/2009005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Accepted: 02/11/2009] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis (Mtb) and Mycobacterium bovis (M. bovis) are the etiological agents of human and bovine tuberculosis (TB, bTB) respectively, and share genetic identity over 99% at the whole genome level. Progress has been made towards explaining how mycobacteria and their infected hosts remain in balance without producing clinical symptoms of disease, a phenomenon referred to as latency or persistence, which can be mimicked by certain in vitro conditions. Latency/persistence has mainly been studied using Mtb, where the two-component signalling system, dosRS, has been assigned an instrumental role, and even constitutes the current basis for development of new diagnostic methods and treatment addressing this particular stage of TB. M. bovis conserves homolog genes that in Mtb play a role in human latent TB infection and that, by analogy, would allow it to enter a persistent state in infected cattle; nevertheless, little attention has been paid to this stage in bovine hosts. We suggest that many of the advances acquired through the study of Mtb can and should be taken into consideration by research groups and veterinary professionals dealing with bTB. The study of the infection in bovines, paying particular attention to defining the molecular and cellular markers of a M. bovis persistent infection in cattle, presents great opportunities for the development and trial of new diagnostic tests and vaccines, tools that will surely help in promoting eradication of bTB in high-burden settings.
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Affiliation(s)
- Angel H Alvarez
- Centro de Investigación y Asistencía en Tecnologá y diseño del Estado de Jalisco (CIATEJ) A.C., Unidad de Biotecnología, Guadalajara, Jalisco, C.P. 44270, México
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Parikh A, Verma SK, Khan S, Prakash B, Nandicoori VK. PknB-mediated phosphorylation of a novel substrate, N-acetylglucosamine-1-phosphate uridyltransferase, modulates its acetyltransferase activity. J Mol Biol 2008; 386:451-64. [PMID: 19121323 DOI: 10.1016/j.jmb.2008.12.031] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 12/06/2008] [Accepted: 12/10/2008] [Indexed: 10/21/2022]
Abstract
Identifying direct targets of kinases and determining how their activities are regulated are central to understanding how they generate biological responses. Genetic and biochemical studies have shown that Mycobacterium tuberculosis serine/threonine protein kinases PknA and PknB play a role in modulating cell shape and possibly cell division. In this report, we show that the enzyme N-acetylglucosamine-1-phosphate uridyltransferase (GlmU) of M. tuberculosis is a novel substrate of PknB and is phosphorylated on threonine residues. GlmU carries out two important biochemical activities: a C-terminal domain catalyzes the transfer of acetyl group from acetyl coenzyme A to glucosamine-1-phosphate to produce N-acetylglucosamine-1-phosphate, which is converted into UDP-N-acetylglucosamine by the transfer of uridine 5'-monophosphate (from uridine 5'-triphosphate), a reaction catalyzed by the N-terminal domain. We determined the crystal structures of GlmU in apo form and UDP-N-acetylglucosamine-bound form, and analyzed them to identify threonine residues that may be accessible to PknB. The structure shows a two-domain architecture, with an N-terminal domain having an alpha/beta-like fold and with a C-terminal domain that forms a left-handed parallel beta-helix structure. Kinase assays with PknB using the N- and C-terminal domains of GlmU as substrates illustrated that PknB phosphorylates GlmU in the C-terminal domain. Furthermore, mutational studies reveal one of the five threonines present in region 414-439 to be phosphorylated by PknB. Structural and biochemical analyses have shown the significance of a variable C-terminal tail in regulating acetyltransferase activity. Notably, we demonstrate that although PknB-mediated phosphorylation of GlmU does not affect its uridyltransferase activity, it significantly modulates the acetyltransferase activity. These findings imply a role for PknB in regulating peptidoglycan synthesis by modulating the acetyltransferase activity of GlmU.
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Affiliation(s)
- Amit Parikh
- National Institute of Immunology, New Delhi, India
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147
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Käser M, Pluschke G. Differential gene repertoire in Mycobacterium ulcerans identifies candidate genes for patho-adaptation. PLoS Negl Trop Dis 2008; 2:e353. [PMID: 19104652 PMCID: PMC2600814 DOI: 10.1371/journal.pntd.0000353] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Accepted: 12/02/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Based on large genomic sequence polymorphisms, several haplotypes belonging to two major lineages of the human pathogen Mycobacterium ulcerans could be distinguished among patient isolates from various geographic origins. However, the biological relevance of insertional/deletional diversity is not understood. METHODOLOGY Using comparative genomics, we have investigated the genes located in regions of difference recently identified by DNA microarray based hybridisation analysis. The analysed regions of difference comprise approximately 7% of the entire M. ulcerans genome. PRINCIPAL FINDINGS Several different mechanisms leading to loss of functional genes were identified, ranging from pseudogenization, caused by frame shift mutations or mobile genetic element interspersing, to large sequence polymorphisms. Four hot spot regions for genetic instability were unveiled. Altogether, 229 coding sequences were found to be differentially inactivated, constituting a repertoire of coding sequence variation in the rather monomorphic M. ulcerans. CONCLUSIONS/SIGNIFICANCE The differential gene inactivation patterns associated with the M. ulcerans haplotypes identified candidate genes that may confer enhanced adaptation upon ablation of expression. A number of gene conversions confined to the classical lineage may contribute to particular virulence of this group comprising isolates from Africa and Australia. Identification of this spectrum of anti-virulence gene candidates expands our understanding of the pathogenicity and ecology of the emerging infectious disease Buruli ulcer.
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148
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Sharma D, Tyagi JS. The value of comparative genomics in understanding mycobacterial virulence: Mycobacterium tuberculosis H37Ra genome sequencing - a worthwhile endeavour. J Biosci 2008; 32:185-9. [PMID: 17435310 DOI: 10.1007/s12038-007-0018-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Deepak Sharma
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India
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149
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Schnell R, Agren D, Schneider G. 1.9 A structure of the signal receiver domain of the putative response regulator NarL from Mycobacterium tuberculosis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2008; 64:1096-100. [PMID: 19052358 PMCID: PMC2593691 DOI: 10.1107/s1744309108035203] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Accepted: 10/28/2008] [Indexed: 11/10/2022]
Abstract
NarL from Mycobacterium tuberculosis is a putative nitrate response regulator that is involved in the regulation of anaerobic metabolism in this pathogen. The recombinant purified N-terminal signal receiver domain of NarL has been crystallized in space group C222(1), with unit-cell parameters a = 85.6, b = 90.0, c = 126.3 A, and the structure was determined by molecular replacement to 1.9 A resolution. Comparisons with related signal receiver domains show that the closest structural homologue is an uncharacterized protein from Staphylococcus aureus, whereas the nearest sequence homologue, NarL from Escherichia coli, displays larger differences in three-dimensional structure. The largest differences between the mycobacterial and E. coli NarL domains were found in the loop between beta3 and alpha3 in the proximity of the phosphorylation site. The active site in response regulators is similar to that of members of the haloacid dehalogenase (HAD) family, which also form a phospho-aspartyl intermediate. In NarL, the aspartic acid that acts as catalytic acid/base in several HAD enzymes is replaced by an arginine residue, which is less likely to participate in steps involving proton abstraction. This substitution may slow down the breakdown of the phospho-aspartyl anhydride and allow signalling beyond the timescales defined by a catalytic reaction intermediate.
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Affiliation(s)
- Robert Schnell
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden.
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150
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Balázsi G, Heath AP, Shi L, Gennaro ML. The temporal response of the Mycobacterium tuberculosis gene regulatory network during growth arrest. Mol Syst Biol 2008; 4:225. [PMID: 18985025 PMCID: PMC2600667 DOI: 10.1038/msb.2008.63] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Accepted: 09/19/2008] [Indexed: 12/13/2022] Open
Abstract
The virulence of Mycobacterium tuberculosis depends on the ability of the bacilli to switch between replicative (growth) and non-replicative (dormancy) states in response to host immunity. However, the gene regulatory events associated with transition to dormancy are largely unknown. To address this question, we have assembled the largest M. tuberculosis transcriptional-regulatory network to date, and characterized the temporal response of this network during adaptation to stationary phase and hypoxia, using published microarray data. Distinct sets of transcriptional subnetworks (origons) were responsive at various stages of adaptation, showing a gradual progression of network response under both conditions. Most of the responsive origons were in common between the two conditions and may help define a general transcriptional signature of M. tuberculosis growth arrest. These results open the door for a systems-level understanding of transition to non-replicative persistence, a phenotypic state that prevents sterilization of infection by the host immune response and promotes the establishment of latent M. tuberculosis infection, a condition found in two billion people worldwide.
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Affiliation(s)
- Gábor Balázsi
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA.
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