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Margolis SR, Meeske AJ. Chaperones help TACkle phage infection. Cell Host Microbe 2024; 32:1039-1041. [PMID: 38991498 DOI: 10.1016/j.chom.2024.06.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2024] [Revised: 06/06/2024] [Accepted: 06/07/2024] [Indexed: 07/13/2024]
Abstract
Bacteria have evolved anti-viral defenses, but the mechanisms of sensing and stopping infection are still under investigation. In this issue of Cell Host & Microbe, Mets, Kurata, Ernits et al. describe how direct sensing of a phage protein by a bacterial toxin-antitoxin-associated chaperone unleashes toxin activity to prevent infection.
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Affiliation(s)
- Shally R Margolis
- Department of Microbiology, University of Washington, Seattle, WA, USA
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2
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Mets T, Kurata T, Ernits K, Johansson MJO, Craig SZ, Evora GM, Buttress JA, Odai R, Wallant KC, Nakamoto JA, Shyrokova L, Egorov AA, Doering CR, Brodiazhenko T, Laub MT, Tenson T, Strahl H, Martens C, Harms A, Garcia-Pino A, Atkinson GC, Hauryliuk V. Mechanism of phage sensing and restriction by toxin-antitoxin-chaperone systems. Cell Host Microbe 2024; 32:1059-1073.e8. [PMID: 38821063 DOI: 10.1016/j.chom.2024.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 04/10/2024] [Accepted: 05/07/2024] [Indexed: 06/02/2024]
Abstract
Toxin-antitoxins (TAs) are prokaryotic two-gene systems composed of a toxin neutralized by an antitoxin. Toxin-antitoxin-chaperone (TAC) systems additionally include a SecB-like chaperone that stabilizes the antitoxin by recognizing its chaperone addiction (ChAD) element. TACs mediate antiphage defense, but the mechanisms of viral sensing and restriction are unexplored. We identify two Escherichia coli antiphage TAC systems containing host inhibition of growth (HigBA) and CmdTA TA modules, HigBAC and CmdTAC. HigBAC is triggered through recognition of the gpV major tail protein of phage λ. Chaperone HigC recognizes gpV and ChAD via analogous aromatic molecular patterns, with gpV outcompeting ChAD to trigger toxicity. For CmdTAC, the CmdT ADP-ribosyltransferase toxin modifies mRNA to halt protein synthesis and limit phage propagation. Finally, we establish the modularity of TACs by creating a hybrid broad-spectrum antiphage system combining the CmdTA TA warhead with a HigC chaperone phage sensor. Collectively, these findings reveal the potential of TAC systems in broad-spectrum antiphage defense.
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Affiliation(s)
- Toomas Mets
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden; University of Tartu, Institute of Technology, 50411 Tartu, Estonia
| | - Tatsuaki Kurata
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Karin Ernits
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Marcus J O Johansson
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Sophie Z Craig
- Cellular and Molecular Microbiology (CM2), Faculté des Sciences, Université Libre de Bruxelles (ULB), Campus La Plaine, Building BC, Room 1C4203, Boulevard du Triomphe, 1050 Brussels, Belgium
| | - Gabriel Medina Evora
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden; Cellular and Molecular Microbiology (CM2), Faculté des Sciences, Université Libre de Bruxelles (ULB), Campus La Plaine, Building BC, Room 1C4203, Boulevard du Triomphe, 1050 Brussels, Belgium
| | - Jessica A Buttress
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4AX, UK
| | - Roni Odai
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Kyo Coppieters't Wallant
- Centre for Structural Biology and Bioinformatics, Université Libre de Bruxelles (ULB), Boulevard du Triomphe, Building BC, 1050 Bruxelles, Belgium
| | - Jose A Nakamoto
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Lena Shyrokova
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Artyom A Egorov
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | | | | | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Tanel Tenson
- University of Tartu, Institute of Technology, 50411 Tartu, Estonia
| | - Henrik Strahl
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4AX, UK
| | - Chloe Martens
- Centre for Structural Biology and Bioinformatics, Université Libre de Bruxelles (ULB), Boulevard du Triomphe, Building BC, 1050 Bruxelles, Belgium
| | - Alexander Harms
- ETH Zurich, Institute of Food, Nutrition and Health, 8092 Zürich, Switzerland
| | - Abel Garcia-Pino
- Cellular and Molecular Microbiology (CM2), Faculté des Sciences, Université Libre de Bruxelles (ULB), Campus La Plaine, Building BC, Room 1C4203, Boulevard du Triomphe, 1050 Brussels, Belgium.
| | - Gemma C Atkinson
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden; Virus Centre, Lund University, Lund, Sweden.
| | - Vasili Hauryliuk
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden; University of Tartu, Institute of Technology, 50411 Tartu, Estonia; Virus Centre, Lund University, Lund, Sweden; Science for Life Laboratory, Lund, Sweden.
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Gurung V, Biswas S, Biswas I. Diverse nature of ClpX degradation motifs in Streptococcus mutans. Microbiol Spectr 2024; 12:e0345723. [PMID: 38051052 PMCID: PMC10782952 DOI: 10.1128/spectrum.03457-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 11/07/2023] [Indexed: 12/07/2023] Open
Abstract
IMPORTANCE Cytoplasmic Clp-related proteases play a major role in maintaining cellular proteome in bacteria. ClpX/P is one such proteolytic complex that is important for conserving protein homeostasis. In this study, we investigated the role of ClpX/P in Streptococcus mutans, an important oral pathogen. We identified several putative substrates whose cellular levels are regulated by ClpX/P in S. mutans and subsequently discovered several recognition motifs that are critical for degradation. Our study is the first comprehensive analysis of determining ClpX/P motifs in streptococci. We believe that identifying the substrates that are regulated by ClpX/P will enhance our understanding about virulence regulation in this important group of pathogens.
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Affiliation(s)
- Vivek Gurung
- Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Saswati Biswas
- Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Indranil Biswas
- Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City, Kansas, USA
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Mycobacterium tuberculosis Requires the Outer Membrane Lipid Phthiocerol Dimycocerosate for Starvation-Induced Antibiotic Tolerance. mSystems 2023; 8:e0069922. [PMID: 36598240 PMCID: PMC9948706 DOI: 10.1128/msystems.00699-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Tolerance of Mycobacterium tuberculosis to antibiotics contributes to the long duration of tuberculosis (TB) treatment and the emergence of drug-resistant strains. M. tuberculosis drug tolerance is induced by nutrient restriction, but the genetic determinants that promote antibiotic tolerance triggered by nutrient limitation have not been comprehensively identified. Here, we show that M. tuberculosis requires production of the outer membrane lipid phthiocerol dimycocerosate (PDIM) to tolerate antibiotics under nutrient-limited conditions. We developed an arrayed transposon (Tn) mutant library in M. tuberculosis Erdman and used orthogonal pooling and transposon sequencing (Tn-seq) to map the locations of individual mutants in the library. We screened a subset of the library (~1,000 mutants) by Tn-seq and identified 32 and 102 Tn mutants with altered tolerance to antibiotics under stationary-phase and phosphate-starved conditions, respectively. Two mutants recovered from the arrayed library, ppgK::Tn and clpS::Tn, showed increased susceptibility to two different drug combinations under both nutrient-limited conditions, but their phenotypes were not complemented by the Tn-disrupted gene. Whole-genome sequencing revealed single nucleotide polymorphisms in both the ppgK::Tn and clpS::Tn mutants that prevented PDIM production. Complementation of the clpS::Tn ppsD Q291* mutant with ppsD restored PDIM production and antibiotic tolerance, demonstrating that loss of PDIM sensitized M. tuberculosis to antibiotics. Our data suggest that drugs targeting production of PDIM, a critical M. tuberculosis virulence determinant, have the potential to enhance the efficacy of existing antibiotics, thereby shortening TB treatment and limiting development of drug resistance. IMPORTANCE Mycobacterium tuberculosis causes 10 million cases of active TB disease and over 1 million deaths worldwide each year. TB treatment is complex, requiring at least 6 months of therapy with a combination of antibiotics. One factor that contributes to the length of TB treatment is M. tuberculosis phenotypic antibiotic tolerance, which allows the bacteria to survive prolonged drug exposure even in the absence of genetic mutations causing drug resistance. Here, we report a genetic screen to identify M. tuberculosis genes that promote drug tolerance during nutrient starvation. Our study revealed the outer membrane lipid phthiocerol dimycocerosate (PDIM) as a key determinant of M. tuberculosis antibiotic tolerance triggered by nutrient starvation. Our study implicates PDIM synthesis as a potential target for development of new TB drugs that would sensitize M. tuberculosis to existing antibiotics to shorten TB treatment.
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Aljghami ME, Barghash MM, Majaesic E, Bhandari V, Houry WA. Cellular functions of the ClpP protease impacting bacterial virulence. Front Mol Biosci 2022; 9:1054408. [PMID: 36533084 PMCID: PMC9753991 DOI: 10.3389/fmolb.2022.1054408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 11/15/2022] [Indexed: 09/28/2023] Open
Abstract
Proteostasis mechanisms significantly contribute to the sculpting of the proteomes of all living organisms. ClpXP is a central AAA+ chaperone-protease complex present in both prokaryotes and eukaryotes that facilitates the unfolding and subsequent degradation of target substrates. ClpX is a hexameric unfoldase ATPase, while ClpP is a tetradecameric serine protease. Substrates of ClpXP belong to many cellular pathways such as DNA damage response, metabolism, and transcriptional regulation. Crucially, disruption of this proteolytic complex in microbes has been shown to impact the virulence and infectivity of various human pathogenic bacteria. Loss of ClpXP impacts stress responses, biofilm formation, and virulence effector protein production, leading to decreased pathogenicity in cell and animal infection models. Here, we provide an overview of the multiple critical functions of ClpXP and its substrates that modulate bacterial virulence with examples from several important human pathogens.
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Affiliation(s)
- Mazen E. Aljghami
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Marim M. Barghash
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Emily Majaesic
- Department of Chemistry, University of Toronto, Toronto, ON, Canada
| | - Vaibhav Bhandari
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Walid A. Houry
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
- Department of Chemistry, University of Toronto, Toronto, ON, Canada
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Mansour M, Giudice E, Xu X, Akarsu H, Bordes P, Guillet V, Bigot DJ, Slama N, D'urso G, Chat S, Redder P, Falquet L, Mourey L, Gillet R, Genevaux P. Substrate recognition and cryo-EM structure of the ribosome-bound TAC toxin of Mycobacterium tuberculosis. Nat Commun 2022; 13:2641. [PMID: 35552387 PMCID: PMC9098466 DOI: 10.1038/s41467-022-30373-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 04/27/2022] [Indexed: 11/16/2022] Open
Abstract
Toxins of toxin-antitoxin systems use diverse mechanisms to control bacterial growth. Here, we focus on the deleterious toxin of the atypical tripartite toxin-antitoxin-chaperone (TAC) system of Mycobacterium tuberculosis, whose inhibition requires the concerted action of the antitoxin and its dedicated SecB-like chaperone. We show that the TAC toxin is a bona fide ribonuclease and identify exact cleavage sites in mRNA targets on a transcriptome-wide scale in vivo. mRNA cleavage by the toxin occurs after the second nucleotide of the ribosomal A-site codon during translation, with a strong preference for CCA codons in vivo. Finally, we report the cryo-EM structure of the ribosome-bound TAC toxin in the presence of native M. tuberculosis cspA mRNA, revealing the specific mechanism by which the TAC toxin interacts with the ribosome and the tRNA in the P-site to cleave its mRNA target. Toxin-antitoxin systems are widespread in bacteria. Here the authors present structures of M. tuberculosis HigBTAC alone and bound to the ribosome in the presence of native cspA mRNA, shedding light on its mechanism of translation inhibition.
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Affiliation(s)
- Moise Mansour
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Emmanuel Giudice
- Institut de Génétique et Développement de Rennes (IGDR), UMR6290, Université de Rennes, CNRS, Rennes, France
| | - Xibing Xu
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Hatice Akarsu
- Department of Biology, University of Fribourg & Swiss Institute of Bioinformatics, Fribourg, Switzerland.,Institute of Veterinary Bacteriology, University of Bern, Bern, Switzerland
| | - Patricia Bordes
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Valérie Guillet
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Donna-Joe Bigot
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France.,Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Nawel Slama
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Gaetano D'urso
- Institut de Génétique et Développement de Rennes (IGDR), UMR6290, Université de Rennes, CNRS, Rennes, France
| | - Sophie Chat
- Institut de Génétique et Développement de Rennes (IGDR), UMR6290, Université de Rennes, CNRS, Rennes, France
| | - Peter Redder
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Laurent Falquet
- Department of Biology, University of Fribourg & Swiss Institute of Bioinformatics, Fribourg, Switzerland
| | - Lionel Mourey
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Reynald Gillet
- Institut de Génétique et Développement de Rennes (IGDR), UMR6290, Université de Rennes, CNRS, Rennes, France.
| | - Pierre Genevaux
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France.
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Abstract
Regulated proteolysis is where AAA+ ATPases (ClpX, ClpC, and ClpE) are coupled to a protease subunit (ClpP) to facilitate degradation of misfolded and native regulatory proteins in the cell. The process is intricately linked to protein quality control and homeostasis and modulates several biological processes. In streptococci, regulated proteolysis is vital to various functions, including virulence expression, competence development, bacteriocin production, biofilm formation, and stress responses. Among the various Clp ATPases, ClpX is the major one that recognizes specific amino acid residues in its substrates and delivers them to the ClpP proteolytic chamber for degradation. While multiple ClpX substrates have been identified in Escherichia coli and other bacteria, little is known about the identity of these substrates in streptococci. Here, we used a preliminary proteomic analysis to identify putative ClpX substrates using Streptococcus mutans as a model organism. SMU.961 is one such putative substrate where we identified the Glu-Lue-Gln (ELQ) motif at the C terminus that is recognized by ClpX/P. We identified several other proteins, including MecA, which also harbor ELQ and are degraded by ClpX/P. This is surprising since MecA is known to be degraded by ClpC/P in Bacillus subtilis; however, ClpX/P-mediated MecA degradation is unknown. We also identified Glu and Gln as the crucial residues for ClpX recognition. Our data indicate a species and perhaps strain-specific recognition of ELQ by streptococcal ClpX/P. At present, we do not know whether this species-dependent degradation by ClpX/P is unique to S. mutans, and we are currently examining the phenomenon in other pathogenic streptococci. IMPORTANCE ClpX/P is a major intracellular proteolytic complex that is responsible for protein quality control in the cell. ClpX, an AAA+ ATPase, distinguishes the potential substrates by recognizing short motifs at the C-terminal end of proteins and delivers the substrates for degradation by ClpP protease. The identity of these ClpX substrates, which varies greatly among bacteria, is known only for a few well-studied species. Here, we used Streptococcus mutans as a model organism to identify ClpX substrates. We found that a short motif of three residues is successfully recognized by ClpX/P. Interestingly, the motif is not present at the ultimate C-terminal end; rather it is present close to the end. This result suggests that streptococcal ClpX ATPase can recognize internal motifs.
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Abstract
Toxin-antitoxin systems are widespread in bacterial genomes. They are usually composed of two elements: a toxin that inhibits an essential cellular process and an antitoxin that counteracts its cognate toxin. In the past decade, a number of new toxin-antitoxin systems have been described, bringing new growth inhibition mechanisms to light as well as novel modes of antitoxicity. However, recent advances in the field profoundly questioned the role of these systems in bacterial physiology, stress response and antimicrobial persistence. This shifted the paradigm of the functions of toxin-antitoxin systems to roles related to interactions between hosts and their mobile genetic elements, such as viral defence or plasmid stability. In this Review, we summarize the recent progress in understanding the biology and evolution of these small genetic elements, and discuss how genomic conflicts could shape the diversification of toxin-antitoxin systems.
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Sharma A, Sagar K, Chauhan NK, Venkataraman B, Gupta N, Gosain TP, Bhalla N, Singh R, Gupta A. HigB1 Toxin in Mycobacterium tuberculosis Is Upregulated During Stress and Required to Establish Infection in Guinea Pigs. Front Microbiol 2021; 12:748890. [PMID: 34917044 PMCID: PMC8669151 DOI: 10.3389/fmicb.2021.748890] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 10/29/2021] [Indexed: 12/20/2022] Open
Abstract
The extraordinary expansion of Toxin Antitoxin (TA) modules in the genome of Mycobacterium tuberculosis has received significant attention over the last few decades. The cumulative evidence suggests that TA systems are activated in response to stress conditions and are essential for M. tuberculosis pathogenesis. In M. tuberculosis, Rv1955-Rv1956-Rv1957 constitutes the only tripartite TAC (Toxin Antitoxin Chaperone) module. In this locus, Rv1955 (HigB1) encodes for the toxin and Rv1956 (HigA1) encodes for antitoxin. Rv1957 encodes for a SecB-like chaperone that regulates HigBA1 toxin antitoxin system by preventing HigA1 degradation. Here, we have investigated the physiological role of HigB1 toxin in stress adaptation and pathogenesis of Mycobacterium tuberculosis. qPCR studies revealed that higBA1 is upregulated in nutrient limiting conditions and upon exposure to levofloxacin. We also show that the promoter activity of higBA1 locus in M. tuberculosis is (p)ppGpp dependent. We observed that HigB1 locus is non-essential for M. tuberculosis growth under different stress conditions in vitro. However, guinea pigs infected with higB1 deletion strain exhibited significantly reduced bacterial loads and pathological damage in comparison to the animals infected with the parental strain. Transcriptome analysis suggested that deletion of higB1 reduced the expression of genes involved in virulence, detoxification and adaptation. The present study describes the role of higB1 toxin in M. tuberculosis physiology and highlights the importance of higBA1 locus during infection in host tissues.
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Affiliation(s)
- Arun Sharma
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, Faridabad, India
| | - Kalpana Sagar
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India.,Centre for Innovation in Infectious Disease Research, Education and Training, New Delhi, India
| | - Neeraj Kumar Chauhan
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, Faridabad, India
| | - Balaji Venkataraman
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India
| | - Nidhi Gupta
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India
| | - Tannu Priya Gosain
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, Faridabad, India
| | - Nikhil Bhalla
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India
| | - Ramandeep Singh
- Tuberculosis Research Laboratory, Translational Health Science and Technology Institute, Faridabad, India
| | - Amita Gupta
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India.,Centre for Innovation in Infectious Disease Research, Education and Training, New Delhi, India
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Bordes P, Genevaux P. Control of Toxin-Antitoxin Systems by Proteases in Mycobacterium Tuberculosis. Front Mol Biosci 2021; 8:691399. [PMID: 34079824 PMCID: PMC8165232 DOI: 10.3389/fmolb.2021.691399] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 05/06/2021] [Indexed: 12/30/2022] Open
Abstract
Toxin-antitoxin (TA) systems are small genetic elements composed of a noxious toxin and a counteracting cognate antitoxin. Although they are widespread in bacterial chromosomes and in mobile genetic elements, their cellular functions and activation mechanisms remain largely unknown. It has been proposed that toxin activation or expression of the TA operon could rely on the degradation of generally less stable antitoxins by cellular proteases. The resulting active toxin would then target essential cellular processes and inhibit bacterial growth. Although interplay between proteases and TA systems has been observed, evidences for such activation cycle are very limited. Herein, we present an overview of the current knowledge on TA recognition by proteases with a main focus on the major human pathogen Mycobacterium tuberculosis, which harbours multiple TA systems (over 80), the essential AAA + stress proteases, ClpC1P1P2 and ClpXP1P2, and the Pup-proteasome system.
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Affiliation(s)
- Patricia Bordes
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Pierre Genevaux
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, Toulouse, France
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