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Ruangprasert A, Maehigashi T, Miles SJ, Dunham CM. Importance of the E. coli DinJ antitoxin carboxy terminus for toxin suppression and regulated proteolysis. Mol Microbiol 2017; 104:65-77. [PMID: 28164393 DOI: 10.1111/mmi.13641] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2017] [Indexed: 11/26/2022]
Abstract
Toxin-antitoxin genes play important roles in the regulation of bacterial growth during stress. One response to stress is selective proteolysis of antitoxin proteins which releases their cognate toxin partners causing rapid inhibition of growth. The features of toxin-antitoxin complexes that are important to inhibit toxin activity as well as to release the active toxin remain elusive. Furthermore, it is unclear how antitoxins are selected for proteolysis by cellular proteases. Here, we test the minimal structural requirements of the Escherichia coli DinJ antitoxin to suppress its toxin partner, YafQ. We find that DinJ-YafQ complex formation is critically dependent on the last ten C-terminal residues of DinJ. However, deletion of these 10 DinJ residues has little effect on transcriptional autorepression suggesting that the YafQ toxin is not a critical component of the repression complex in contrast to other toxin-antitoxin systems. We further demonstrate that loop 5 preceding these ten C-terminal residues is important for Lon-mediated proteolysis. These results provide important insights into the critical interactions between toxin-antitoxin pairs necessary to inhibit toxin activity and the regulated proteolysis of antitoxins.
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Affiliation(s)
- Ajchareeya Ruangprasert
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA
| | - Tatsuya Maehigashi
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA
| | - Stacey J Miles
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA
| | - Christine M Dunham
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road NE, Atlanta, GA, 30322, USA
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Van Melderen L, Wood TK. Commentary: What Is the Link between Stringent Response, Endoribonuclease Encoding Type II Toxin-Antitoxin Systems and Persistence? Front Microbiol 2017; 8:191. [PMID: 28261163 PMCID: PMC5306293 DOI: 10.3389/fmicb.2017.00191] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 01/26/2017] [Indexed: 11/13/2022] Open
Affiliation(s)
- Laurence Van Melderen
- Laboratoire de Génétique et Physiologie Bactérienne, Faculté des Sciences, Université Libre de Bruxelles (ULB) Gosselies, Belgium
| | - Thomas K Wood
- Department of Chemical Engineering, Pennsylvania State University State College, PA, USA
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53
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Ramisetty BCM, Ghosh D, Roy Chowdhury M, Santhosh RS. What Is the Link between Stringent Response, Endoribonuclease Encoding Type II Toxin-Antitoxin Systems and Persistence? Front Microbiol 2016; 7:1882. [PMID: 27933045 PMCID: PMC5120126 DOI: 10.3389/fmicb.2016.01882] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Accepted: 11/09/2016] [Indexed: 11/21/2022] Open
Abstract
Persistence is a transient and non-inheritable tolerance to antibiotics by a small fraction of a bacterial population. One of the proposed determinants of bacterial persistence is toxin–antitoxin systems (TASs) which are also implicated in a wide range of stress-related phenomena. Maisonneuve E, Castro-Camargo M, Gerdes K. 2013. Cell 154:1140–1150 reported an interesting link between ppGpp mediated stringent response, TAS, and persistence. It is proposed that accumulation of ppGpp enhances the accumulation of inorganic polyphosphate which modulates Lon protease to degrade antitoxins. The decrease in the concentration of antitoxins supposedly activated the toxin to increase in the number of persisters during antibiotic treatment. In this study, we show that inorganic polyphosphate is not required for transcriptional activation of yefM/yoeB TAS, which is an indirect indication of Lon-dependent degradation of YefM antitoxin. The Δ10 strain, an Escherichia coli MG1655 derivative in which the 10 TAS are deleted, is more sensitive to ciprofloxacin compared to wild type MG1655. Furthermore, we show that the Δ10 strain has relatively lower fitness compared to the wild type and hence, we argue that the persistence related implications based on Δ10 strain are void. We conclude that the transcriptional regulation and endoribonuclease activity of YefM/YoeB TAS is independent of ppGpp and inorganic polyphosphate. Therefore, we urge for thorough inspection and debate on the link between chromosomal endoribonuclease TAS and persistence.
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Affiliation(s)
- Bhaskar C M Ramisetty
- School of Chemical and Biotechnology, SASTRA UniversityThanjavur, India; Department of Biochemistry and Molecular Biology, University of Southern DenmarkOdense, Denmark
| | - Dimpy Ghosh
- School of Chemical and Biotechnology, SASTRA University Thanjavur, India
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54
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Yang J, Zhou K, Liu P, Dong Y, Gao Z, Zhang J, Liu Q. Structural insight into the E. coli HigBA complex. Biochem Biophys Res Commun 2016; 478:1521-7. [DOI: 10.1016/j.bbrc.2016.08.131] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 08/23/2016] [Indexed: 12/16/2022]
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55
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Zhao Y, McAnulty MJ, Wood TK. Toxin YafQ Reduces Escherichia coli Growth at Low Temperatures. PLoS One 2016; 11:e0161577. [PMID: 27557125 PMCID: PMC4996492 DOI: 10.1371/journal.pone.0161577] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 08/08/2016] [Indexed: 11/19/2022] Open
Abstract
Toxin/antitoxin (TA) systems reduce metabolism under stress; for example, toxin YafQ of the YafQ/DinJ Escherichia coli TA system reduces growth by cleaving transcripts with in-frame 5'-AAA-G/A-3' sites, and antitoxin DinJ is a global regulator that represses its locus as well as controls levels of the stationary sigma factor RpoS. Here we investigated the influence on cell growth at various temperatures and found that deletion of the antitoxin gene, dinJ, resulted in both reduced metabolism and slower growth at 18°C but not at 37°C. The reduction in growth could be complemented by producing DinJ from a plasmid. Using a transposon screen to reverse the effect of the absence of DinJ, two mutations were found that inactivated the toxin YafQ; hence, the toxin caused the slower growth only at low temperatures rather than DinJ acting as a global regulator. Corroborating this result, a clean deletion of yafQ in the ΔdinJ ΔKmR strain restored both metabolism and growth at 18°C. In addition, production of YafQ was more toxic at 18°C compared to 37°C. Furthermore, by overproducing all the E. coli proteins, the global transcription repressor Mlc was found that counteracts YafQ toxicity only at 18°C. Therefore, YafQ is more effective at reducing metabolism at low temperatures, and Mlc is its putative target.
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Affiliation(s)
- Yueju Zhao
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing, 100193, P. R. China
- Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, P. R. China
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America
| | - Michael J. McAnulty
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America
| | - Thomas K. Wood
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America
- * E-mail:
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Schureck MA, Maehigashi T, Miles SJ, Marquez J, Dunham CM. mRNA bound to the 30S subunit is a HigB toxin substrate. RNA (NEW YORK, N.Y.) 2016; 22:1261-70. [PMID: 27307497 PMCID: PMC4931118 DOI: 10.1261/rna.056218.116] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 05/07/2016] [Indexed: 05/22/2023]
Abstract
Activation of bacterial toxins during stress results in cleavage of mRNAs in the context of the ribosome. These toxins are thought to function as global translational inhibitors yet recent studies suggest each may have distinct mRNA specificities that result in selective translation for bacterial survival. Here we demonstrate that mRNA in the context of a bacterial 30S subunit is sufficient for ribosome-dependent toxin HigB endonucleolytic activity, suggesting that HigB interferes with the initiation step of translation. We determined the X-ray crystal structure of HigB bound to the 30S, revealing that two solvent-exposed clusters of HigB basic residues directly interact with 30S 16S rRNA helices 18, 30, and 31. We further show that these HigB residues are essential for ribosome recognition and function. Comparison with other ribosome-dependent toxins RelE and YoeB reveals that each interacts with similar features of the 30S aminoacyl (A) site yet does so through presentation of diverse structural motifs.
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Affiliation(s)
- Marc A Schureck
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | - Tatsuya Maehigashi
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | - Stacey J Miles
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | - Jhomar Marquez
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | - Christine M Dunham
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Type II Toxin-Antitoxin Systems in the Unicellular Cyanobacterium Synechocystis sp. PCC 6803. Toxins (Basel) 2016; 8:toxins8070228. [PMID: 27455323 PMCID: PMC4963859 DOI: 10.3390/toxins8070228] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 07/11/2016] [Indexed: 12/03/2022] Open
Abstract
Bacterial toxin–antitoxin (TA) systems are genetic elements, which are encoded by plasmid as well as chromosomal loci. They mediate plasmid and genomic island maintenance through post-segregational killing mechanisms but may also have milder effects, acting as mobile stress response systems that help certain cells of a population in persisting adverse growth conditions. Very few cyanobacterial TA system have been characterized thus far. In this work, we focus on the cyanobacterium Synechocystis 6803, a widely used model organism. We expand the number of putative Type II TA systems from 36 to 69 plus seven stand-alone components. Forty-seven TA pairs are located on the chromosome and 22 are plasmid-located. Different types of toxins are associated with various antitoxins in a mix and match principle. According to protein domains and experimental data, 81% of all toxins in Synechocystis 6803 likely exhibit RNase activity, suggesting extensive potential for toxicity-related RNA degradation and toxin-mediated transcriptome remodeling. Of particular interest is the Ssr8013–Slr8014 system encoded on plasmid pSYSG, which is part of a larger defense island or the pSYSX system Slr6056–Slr6057, which is linked to a bacterial ubiquitin-like system. Consequently, Synechocystis 6803 is one of the most prolific sources of new information about these genetic elements.
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58
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Toxin-Antitoxin Modules Are Pliable Switches Activated by Multiple Protease Pathways. Toxins (Basel) 2016; 8:toxins8070214. [PMID: 27409636 PMCID: PMC4963847 DOI: 10.3390/toxins8070214] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Revised: 06/24/2016] [Accepted: 06/27/2016] [Indexed: 02/06/2023] Open
Abstract
Toxin-antitoxin (TA) modules are bacterial regulatory switches that facilitate conflicting outcomes for cells by promoting a pro-survival phenotypic adaptation and/or by directly mediating cell death, all through the toxin activity upon degradation of antitoxin. Intensive study has revealed specific details of TA module functions, but significant gaps remain about the molecular details of activation via antitoxin degradation used by different bacteria and in different environments. This review summarizes the current state of knowledge about the interaction of antitoxins with cellular proteases Lon and ClpP to mediate TA module activation. An understanding of these processes can answer long-standing questions regarding stochastic versus specific activation of TA modules and provide insight into the potential for manipulation of TA modules to alter bacterial growth.
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59
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Characterization of the Deep-Sea Streptomyces sp. SCSIO 02999 Derived VapC/VapB Toxin-Antitoxin System in Escherichia coli. Toxins (Basel) 2016; 8:toxins8070195. [PMID: 27376329 PMCID: PMC4963828 DOI: 10.3390/toxins8070195] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/13/2016] [Accepted: 06/20/2016] [Indexed: 11/16/2022] Open
Abstract
Toxin-antitoxin (TA) systems are small genetic elements that are ubiquitous in prokaryotes. Most studies on TA systems have focused on commensal and pathogenic bacteria; yet very few studies have focused on TAs in marine bacteria, especially those isolated from a deep sea environment. Here, we characterized a type II VapC/VapB TA system from the deep-sea derived Streptomyces sp. SCSIO 02999. The VapC (virulence-associated protein) protein belongs to the PIN (PilT N-terminal) superfamily. Overproduction of VapC strongly inhibited cell growth and resulted in a bleb-containing morphology in E. coli. The toxicity of VapC was neutralized through direct protein-protein interaction by a small protein antitoxin VapB encoded by a neighboring gene. Antitoxin VapB alone or the VapB/VapC complex negatively regulated the vapBC promoter activity. We further revealed that three conserved Asp residues in the PIN domain were essential for the toxic effect of VapC. Additionally, the VapC/VapB TA system stabilized plasmid in E. coli. Furthermore, VapC cross-activated transcription of several TA operons via a partially Lon-dependent mechanism in E. coli, and the activated toxins accumulated more preferentially than their antitoxin partners. Collectively, we identified and characterized a new deep sea TA system in the deep sea Streptomyces sp. and demonstrated that the VapC toxin in this system can cross-activate TA operons in E. coli.
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60
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AAU-Specific RNA Cleavage Mediated by MazF Toxin Endoribonuclease Conserved in Nitrosomonas europaea. Toxins (Basel) 2016; 8:toxins8060174. [PMID: 27271670 PMCID: PMC4926141 DOI: 10.3390/toxins8060174] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 05/30/2016] [Indexed: 02/07/2023] Open
Abstract
Nitrosomonas europaea carries numerous toxin-antitoxin systems. However, despite the abundant representation in its chromosome, studies have not surveyed the underlying molecular functions in detail, and their biological roles remain enigmatic. In the present study, we found that a chromosomally-encoded MazF family member, predicted at the locus NE1181, is a functional toxin endoribonuclease, and constitutes a toxin-antitoxin system, together with its cognate antitoxin, MazE. Massive parallel sequencing provided strong evidence that this toxin endoribonuclease exhibits RNA cleavage activity, primarily against the AAU triplet. This sequence-specificity was supported by the results of fluorometric assays. Our results indicate that N. europaea alters the translation profile and regulates its growth using the MazF family of endoribonuclease under certain stressful conditions.
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61
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Ainelo A, Tamman H, Leppik M, Remme J, Hõrak R. The toxin GraT inhibits ribosome biogenesis. Mol Microbiol 2016; 100:719-34. [PMID: 26833678 DOI: 10.1111/mmi.13344] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/31/2016] [Indexed: 12/28/2022]
Abstract
Most bacteria encode numerous chromosomal toxin-antitoxin (TA) systems that are proposed to contribute to stress tolerance, as they are able to shift the cells to a dormant state. Toxins act on a variety of targets with the majority attacking the translational apparatus. Intriguingly, the toxicity mechanisms of even closely related toxins may differ essentially. Here, we report on a new type of TA toxin that inhibits ribosome biogenesis. GraT of the GraTA system has previously been described in Pseudomonas putida as an unusually moderate toxin at optimal growth temperatures. However, GraT causes a severe growth defect at lower temperatures. Here, we demonstrate that GraT causes the accumulation of free ribosomal subunits. Mapping the rRNA 5' ends reveals incomplete processing of the free subunits and quantification of modified nucleosides shows an underrepresentation of late subunit assembly specific modifications. This indicates that GraT inhibits ribosome subunit assembly. Interestingly, GraT effects can be alleviated by modification of the chaperone DnaK, a known facilitator of late stages in ribosome biogenesis. We show that GraT directly interacts with DnaK and suggest two possible models for the role of this interaction in GraT toxicity.
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Affiliation(s)
- Andres Ainelo
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Hedvig Tamman
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Margus Leppik
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Jaanus Remme
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
| | - Rita Hõrak
- Institute of Molecular and Cell Biology, University of Tartu, 51010, Tartu, Estonia
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62
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Miyamoto T, Kato Y, Sekiguchi Y, Tsuneda S, Noda N. Characterization of MazF-Mediated Sequence-Specific RNA Cleavage in Pseudomonas putida Using Massive Parallel Sequencing. PLoS One 2016; 11:e0149494. [PMID: 26885644 PMCID: PMC4757574 DOI: 10.1371/journal.pone.0149494] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 02/02/2016] [Indexed: 11/18/2022] Open
Abstract
Under environmental stress, microbes are known to alter their translation patterns using sequence-specific endoribonucleases that we call RNA interferases. However, there has been limited insight regarding which RNAs are specifically cleaved by these RNA interferases, hence their physiological functions remain unknown. In the current study, we developed a novel method to effectively identify cleavage specificities with massive parallel sequencing. This approach uses artificially designed RNAs composed of diverse sequences, which do not form extensive secondary structures, and it correctly identified the cleavage sequence of a well-characterized Escherichia coli RNA interferase, MazF, as ACA. In addition, we also determined that an uncharacterized MazF homologue isolated from Pseudomonas putida specifically recognizes the unique triplet, UAC. Using a real-time fluorescence resonance energy transfer assay, the UAC triplet was further proved to be essential for cleavage in P. putida MazF. These results highlight an effective method to determine cleavage specificity of RNA interferases.
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Affiliation(s)
- Tatsuki Miyamoto
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan.,Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Yuka Kato
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Yuji Sekiguchi
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Satoshi Tsuneda
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Naohiro Noda
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan.,Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
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63
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Persistence Increases in the Absence of the Alarmone Guanosine Tetraphosphate by Reducing Cell Growth. Sci Rep 2016; 6:20519. [PMID: 26837570 PMCID: PMC4738310 DOI: 10.1038/srep20519] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 01/07/2016] [Indexed: 11/09/2022] Open
Abstract
Most bacterial cells are stressed, and as a result, some become tolerant to antibiotics by entering a dormant state known as persistence. The key intracellular metabolite that has been linked to this persister state is guanosine tetraphosphate (ppGpp), the alarmone that was first linked to nutrient stress. In Escherichia coli, ppGpp redirects protein production during nutrient stress by interacting with RNA polymerase directly and by inhibiting several proteins. Consistently, increased levels of ppGpp lead to increased persistence; but, the mechanism by which elevated ppGpp translates into persistence has not been determined. Hence, we explored persistence in the absence of ppGpp so that the underlying mechanism of persister cell formation could be explored. We found that persister cells still form, although at lower levels, in the absence of ppGpp. Additionally, the toxin/antitoxin systems that we investigated (MqsR, MazF, GhoT, and YafQ) remain able to increase persistence dramatically in the absence of ppGpp. By overproducing each E. coli protein from the 4287 plasmid vectors of the ASKA library and selecting for increased persistence in the absence of ppGpp (via a relA spoT mutant), we identified five new proteins, YihS, PntA, YqjE, FocA, and Zur, that increase persistence simply by reducing cell growth.
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64
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Schifano JM, Cruz JW, Vvedenskaya IO, Edifor R, Ouyang M, Husson RN, Nickels BE, Woychik NA. tRNA is a new target for cleavage by a MazF toxin. Nucleic Acids Res 2016; 44:1256-70. [PMID: 26740583 PMCID: PMC4756823 DOI: 10.1093/nar/gkv1370] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 11/25/2015] [Indexed: 01/08/2023] Open
Abstract
Toxin-antitoxin (TA) systems play key roles in bacterial persistence, biofilm formation and stress responses. The MazF toxin from the Escherichia coli mazEF TA system is a sequence- and single-strand-specific endoribonuclease, and many studies have led to the proposal that MazF family members exclusively target mRNA. However, recent data indicate some MazF toxins can cleave specific sites within rRNA in concert with mRNA. In this report, we identified the repertoire of RNAs cleaved by Mycobacterium tuberculosis toxin MazF-mt9 using an RNA-seq-based approach. This analysis revealed that two tRNAs were the principal targets of MazF-mt9, and each was cleaved at a single site in either the tRNA(Pro14) D-loop or within the tRNA(Lys43) anticodon. This highly selective target discrimination occurs through recognition of not only sequence but also structural determinants. Thus, MazF-mt9 represents the only MazF family member known to target tRNA and to require RNA structure for recognition and cleavage. Interestingly, the tRNase activity of MazF-mt9 mirrors basic features of eukaryotic tRNases that also generate stable tRNA-derived fragments that can inhibit translation in response to stress. Our data also suggest a role for tRNA distinct from its canonical adapter function in translation, as cleavage of tRNAs by MazF-mt9 downregulates bacterial growth.
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Affiliation(s)
- Jason M Schifano
- Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, USA
| | - Jonathan W Cruz
- Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, USA
| | - Irina O Vvedenskaya
- Waksman Institute, Rutgers University, Piscataway, NJ, USA Department of Genetics, Rutgers University, Piscataway, NJ, USA
| | - Regina Edifor
- Division of Infectious Diseases, Boston Children's Hospital/Harvard Medical School, Boston, MA, USA
| | - Ming Ouyang
- Department of Computer Science, University of Massachusetts Boston, Boston, MA, USA
| | - Robert N Husson
- Division of Infectious Diseases, Boston Children's Hospital/Harvard Medical School, Boston, MA, USA
| | - Bryce E Nickels
- Waksman Institute, Rutgers University, Piscataway, NJ, USA Department of Genetics, Rutgers University, Piscataway, NJ, USA Member, Rutgers Cancer Institute of New Jersey, NJ, USA
| | - Nancy A Woychik
- Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, USA Member, Rutgers Cancer Institute of New Jersey, NJ, USA
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65
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Tsukuda M, Nakashima N, Miyazaki K. Counterselection method based on conditional silencing of antitoxin genes in Escherichia coli. J Biosci Bioeng 2015; 120:591-5. [DOI: 10.1016/j.jbiosc.2015.03.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/02/2015] [Accepted: 03/12/2015] [Indexed: 01/29/2023]
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66
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The Mycobacterium tuberculosis relBE toxin:antitoxin genes are stress-responsive modules that regulate growth through translation inhibition. J Microbiol 2015; 53:783-95. [PMID: 26502963 DOI: 10.1007/s12275-015-5333-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/30/2015] [Accepted: 10/05/2015] [Indexed: 12/11/2022]
Abstract
Toxin-antitoxin (TA) genes are ubiquitous among bacteria and are associated with persistence and dormancy. Following exposure to unfavorable environmental stimuli, several species (Escherichia coli, Staphylococcus aureus, Myxococcus xanthus) employ toxin proteins such as RelE and MazF to downregulate growth or initiate cell death. Mycobacterium tuberculosis possesses three Rel TA modules (Rel Mtb ): RelBE Mtb , RelFG Mtb and RelJK Mtb (Rv1246c-Rv1247c, Rv2865-Rv2866, and Rv3357-Rv3358, respectively), which inhibit mycobacterial growth when the toxin gene (relE, relG, relK) is expressed independently of the antitoxin gene (relB, relF, relJ). In the present study, we examined the in vivo mechanism of the RelE Mtb toxin protein, the impact of RelE Mtb on M. tuberculosis physiology and the environmental conditions that regulate all three rel Mtb modules. RelE Mtb negatively impacts growth and the structural integrity of the mycobacterial envelope, generating cells with aberrant forms that are prone to extensive aggregation. At a time coincident with growth defects, RelE Mtb mediates mRNA degradation in vivo resulting in significant changes to the proteome. We establish that rel Mtb modules are stress responsive, as all three operons are transcriptionally activated following mycobacterial exposure to oxidative stress or nitrogen-limiting growth environments. Here we present evidence that the rel Mtb toxin:antitoxin family is stress-responsive and, through the degradation of mRNA, the RelE Mtb toxin influences the growth, proteome and morphology of mycobacterial cells.
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67
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Defining the mRNA recognition signature of a bacterial toxin protein. Proc Natl Acad Sci U S A 2015; 112:13862-7. [PMID: 26508639 DOI: 10.1073/pnas.1512959112] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacteria contain multiple type II toxins that selectively degrade mRNAs bound to the ribosome to regulate translation and growth and facilitate survival during the stringent response. Ribosome-dependent toxins recognize a variety of three-nucleotide codons within the aminoacyl (A) site, but how these endonucleases achieve substrate specificity remains poorly understood. Here, we identify the critical features for how the host inhibition of growth B (HigB) toxin recognizes each of the three A-site nucleotides for cleavage. X-ray crystal structures of HigB bound to two different codons on the ribosome illustrate how HigB uses a microbial RNase-like nucleotide recognition loop to recognize either cytosine or adenosine at the second A-site position. Strikingly, a single HigB residue and 16S rRNA residue C1054 form an adenosine-specific pocket at the third A-site nucleotide, in contrast to how tRNAs decode mRNA. Our results demonstrate that the most important determinant for mRNA cleavage by ribosome-dependent toxins is interaction with the third A-site nucleotide.
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Wood TK. Combatting bacterial persister cells. Biotechnol Bioeng 2015; 113:476-83. [DOI: 10.1002/bit.25721] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 08/03/2015] [Accepted: 08/04/2015] [Indexed: 01/07/2023]
Affiliation(s)
- Thomas K. Wood
- Department of Chemical EngineeringPennsylvania State UniversityUniversity ParkPennsylvania
- Department Biochemistry, Molecular BiologyPennsylvania State UniversityUniversity ParkPennsylvania16802‐4400
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69
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Maehigashi T, Ruangprasert A, Miles SJ, Dunham CM. Molecular basis of ribosome recognition and mRNA hydrolysis by the E. coli YafQ toxin. Nucleic Acids Res 2015; 43:8002-12. [PMID: 26261214 PMCID: PMC4652777 DOI: 10.1093/nar/gkv791] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 07/22/2015] [Indexed: 01/30/2023] Open
Abstract
Bacterial type II toxin-antitoxin modules are protein–protein complexes whose functions are finely tuned by rapidly changing environmental conditions. E. coli toxin YafQ is suppressed under steady state growth conditions by virtue of its interaction with its cognate antitoxin, DinJ. During stress, DinJ is proteolytically degraded and free YafQ halts translation by degrading ribosome-bound mRNA to slow growth until the stress has passed. Although structures of the ribosome with toxins RelE and YoeB have been solved, it is unclear what residues among ribosome-dependent toxins are essential for mediating both recognition of the ribosome and the mRNA substrate given their low sequence identities. Here we show that YafQ coordinates binding to the 70S ribosome via three surface-exposed patches of basic residues that we propose directly interact with 16S rRNA. We demonstrate that YafQ residues H50, H63, D67 and H87 participate in acid-base catalysis during mRNA hydrolysis and further show that H50 and H63 functionally complement as general bases to initiate the phosphodiester cleavage reaction. Moreover YafQ residue F91 likely plays an important role in mRNA positioning. In summary, our findings demonstrate the plasticity of ribosome-dependent toxin active site residues and further our understanding of which toxin residues are important for function.
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Affiliation(s)
- Tatsuya Maehigashi
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
| | | | - Stacey J Miles
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Christine M Dunham
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
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70
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Janssen BD, Garza-Sánchez F, Hayes CS. YoeB toxin is activated during thermal stress. Microbiologyopen 2015; 4:682-97. [PMID: 26147890 PMCID: PMC4554461 DOI: 10.1002/mbo3.272] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 05/27/2015] [Indexed: 11/07/2022] Open
Abstract
Type II toxin-antitoxin (TA) modules are thought to mediate stress-responses by temporarily suppressing protein synthesis while cells redirect transcription to adapt to environmental change. Here, we show that YoeB, a ribosome-dependent mRNase toxin, is activated in Escherichia coli cells grown at elevated temperatures. YoeB activation is dependent on Lon protease, suggesting that thermal stress promotes increased degradation of the YefM antitoxin. Though YefM is efficiently degraded in response to Lon overproduction, we find that Lon antigen levels do not increase during heat shock, indicating that another mechanism accounts for temperature-induced YefM proteolysis. These observations suggest that YefM/YoeB functions in adaptation to temperature stress. However, this response is distinct from previously described models of TA function. First, YoeB mRNase activity is maintained over several hours of culture at 42°C, indicating that thermal activation is not transient. Moreover, heat-activated YoeB does not induce growth arrest nor does it suppress global protein synthesis. In fact, E. coli cells proliferate more rapidly at elevated temperatures and instantaneously accelerate their growth rate in response to acute heat shock. We propose that heat-activated YoeB may serve a quality control function, facilitating the recycling of stalled translation complexes through ribosome rescue pathways.
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Affiliation(s)
- Brian D Janssen
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California
| | - Fernando Garza-Sánchez
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California.,Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, California
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71
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Yao J, Guo Y, Zeng Z, Liu X, Shi F, Wang X. Identification and characterization of a HEPN-MNT family type II toxin-antitoxin in Shewanella oneidensis. Microb Biotechnol 2015; 8:961-73. [PMID: 26112399 PMCID: PMC4621449 DOI: 10.1111/1751-7915.12294] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 04/20/2015] [Accepted: 05/02/2015] [Indexed: 11/30/2022] Open
Abstract
Toxin-antitoxin (TA) systems are prevalent in bacteria and archaea. However, related studies in the ecologically and bioelectrochemically important strain Shewanella oneidensis are limited. Here, we show that SO_3166, a member of the higher eukaryotes and prokaryotes nucleotide-binding (HEPN) superfamily, strongly inhibited cell growth in S. oneidensis and Escherichia coli. SO_3165, a putative minimal nucleotidyltransferase (MNT), neutralized the toxicity of SO_3166. Gene SO_3165 lies upstream of SO_3166, and they are co-transcribed. Moreover, the SO_3165 and SO_3166 proteins interact with each other directly in vivo, and antitoxin SO_3165 bound to the promoter of the TA operon and repressed its activity. Finally, the conserved Rx4-6H domain in HEPN family was identified in SO_3166. Mutating either the R or H abolished SO_3166 toxicity, confirming that Rx4-6H domain is critical for SO_3166 activity. Taken together, these results demonstrate that SO_3166 and SO_3165 in S. oneidensis form a typical type II TA pair. This TA pair plays a critical role in regulating bacterial functions because its disruption led to impaired cell motility in S. oneidensis. Thus, we demonstrated for the first time that HEPN-MNT can function as a TA system, thereby providing important insights into the understanding of the function and regulation of HEPNs and MNTs in prokaryotes.
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Affiliation(s)
- Jianyun Yao
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yunxue Guo
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Zhenshun Zeng
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoxiao Liu
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Fei Shi
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Xiaoxue Wang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
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Activation of Toxin-Antitoxin System Toxins Suppresses Lethality Caused by the Loss of σE in Escherichia coli. J Bacteriol 2015; 197:2316-24. [PMID: 25917909 DOI: 10.1128/jb.00079-15] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 04/24/2015] [Indexed: 01/01/2023] Open
Abstract
UNLABELLED σ(E), an alternative σ factor that governs a major signaling pathway in envelope stress responses in Gram-negative bacteria, is essential for growth of Escherichia coli not only under stressful conditions, such as elevated temperature, but also under normal laboratory conditions. A mutational inactivation of the hicB gene has been reported to suppress the lethality caused by the loss of σ(E). hicB encodes the antitoxin of the HicA-HicB toxin-antitoxin (TA) system; overexpression of the HicA toxin, which exhibits mRNA interferase activity, causes cleavage of mRNAs and an arrest of cell growth, while simultaneous expression of HicB neutralizes the toxic effects of overproduced HicA. To date, however, how the loss of HicB rescues the cell lethality in the absence of σ(E) and, more specifically, whether HicA is involved in this process remain unknown. Here we showed that simultaneous disruption of hicA abolished suppression of the σ(E) essentiality in the absence of hicB, while ectopic expression of wild-type HicA, but not that of its mutant forms without mRNA interferase activity, restored the suppression. Furthermore, HicA and two other mRNA interferase toxins, HigB and YafQ, suppressed the σ(E) essentiality even in the presence of chromosomally encoded cognate antitoxins when these toxins were overexpressed individually. Interestingly, when the growth media were supplemented with low levels of antibiotics that are known to activate toxins, E. coli cells with no suppressor mutations grew independently of σ(E). Taken together, our results indicate that the activation of TA system toxins can suppress the σ(E) essentiality and affect the extracytoplasmic stress responses. IMPORTANCE σ(E) is an alternative σ factor involved in extracytoplasmic stress responses. Unlike other alternative σ factors, σ(E) is indispensable for the survival of E. coli even under unstressed conditions, although the exact reason for its essentiality remains unknown. Toxin-antitoxin (TA) systems are widely distributed in prokaryotes and are composed of two adjacent genes, encoding a toxin that exerts harmful effects on the toxin-producing bacterium itself and an antitoxin that neutralizes the cognate toxin. Curiously, it is known that inactivation of an antitoxin rescues the σ(E) essentiality, suggesting a connection between TA systems and σ(E) function. We demonstrate here that toxin activation is necessary for this rescue and suggest the possible involvement of TA systems in extracytoplasmic stress responses.
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73
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Sterckx YGJ, De Gieter S, Zorzini V, Hadži S, Haesaerts S, Loris R, Garcia-Pino A. An efficient method for the purification of proteins from four distinct toxin–antitoxin modules. Protein Expr Purif 2015; 108:30-40. [DOI: 10.1016/j.pep.2015.01.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 12/27/2014] [Accepted: 01/04/2015] [Indexed: 11/24/2022]
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74
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MazF ribonucleases promote Mycobacterium tuberculosis drug tolerance and virulence in guinea pigs. Nat Commun 2015; 6:6059. [PMID: 25608501 DOI: 10.1038/ncomms7059] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 12/05/2014] [Indexed: 11/08/2022] Open
Abstract
Toxin-antitoxin (TA) systems are highly conserved in members of the Mycobacterium tuberculosis (Mtb) complex and have been proposed to play an important role in physiology and virulence. Nine of these TA systems belong to the mazEF family, encoding the intracellular MazF toxin and its antitoxin, MazE. By overexpressing each of the nine putative MazF homologues in Mycobacterium bovis BCG, here we show that Rv1102c (MazF3), Rv1991c (MazF6) and Rv2801c (MazF9) induce bacteriostasis. The construction of various single-, double- and triple-mutant Mtb strains reveals that these MazF ribonucleases contribute synergistically to the ability of Mtb to adapt to conditions such as oxidative stress, nutrient depletion and drug exposure. Moreover, guinea pigs infected with the triple-mutant strain exhibits significantly reduced bacterial loads and pathological damage in infected tissues in comparison with parental strain-infected guinea pigs. The present study highlights the importance of MazF ribonucleases in Mtb stress adaptation, drug tolerance and virulence.
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Starosta AL, Lassak J, Jung K, Wilson DN. The bacterial translation stress response. FEMS Microbiol Rev 2014; 38:1172-201. [PMID: 25135187 DOI: 10.1111/1574-6976.12083] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 07/18/2014] [Accepted: 08/07/2014] [Indexed: 11/30/2022] Open
Abstract
Throughout their life, bacteria need to sense and respond to environmental stress. Thus, such stress responses can require dramatic cellular reprogramming, both at the transcriptional as well as the translational level. This review focuses on the protein factors that interact with the bacterial translational apparatus to respond to and cope with different types of environmental stress. For example, the stringent factor RelA interacts with the ribosome to generate ppGpp under nutrient deprivation, whereas a variety of factors have been identified that bind to the ribosome under unfavorable growth conditions to shut-down (RelE, pY, RMF, HPF and EttA) or re-program (MazF, EF4 and BipA) translation. Additional factors have been identified that rescue ribosomes stalled due to stress-induced mRNA truncation (tmRNA, ArfA, ArfB), translation of unfavorable protein sequences (EF-P), heat shock-induced subunit dissociation (Hsp15), or antibiotic inhibition (TetM, FusB). Understanding the mechanism of how the bacterial cell responds to stress will not only provide fundamental insight into translation regulation, but will also be an important step to identifying new targets for the development of novel antimicrobial agents.
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Affiliation(s)
- Agata L Starosta
- Gene Center, Department for Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany; Center for integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universität München, Munich, Germany
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76
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Hu Y, Kwan BW, Osbourne DO, Benedik MJ, Wood TK. Toxin YafQ increases persister cell formation by reducing indole signalling. Environ Microbiol 2014; 17:1275-85. [PMID: 25041421 DOI: 10.1111/1462-2920.12567] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 07/05/2014] [Indexed: 01/04/2023]
Abstract
Persister cells survive antibiotic and other environmental stresses by slowing metabolism. Since toxins of toxin/antitoxin (TA) systems have been postulated to be responsible for persister cell formation, we investigated the influence of toxin YafQ of the YafQ/DinJ Escherichia coli TA system on persister cell formation. Under stress, YafQ alters metabolism by cleaving transcripts with in-frame 5'-AAA-G/A-3' sites. Production of YafQ increased persister cell formation with multiple antibiotics, and by investigating changes in protein expression, we found that YafQ reduced tryptophanase levels (TnaA mRNA has 16 putative YafQ cleavage sites). Consistently, TnaA mRNA levels were also reduced by YafQ. Tryptophanase is activated in the stationary phase by the stationary-phase sigma factor RpoS, which was also reduced dramatically upon production of YafQ. Tryptophanase converts tryptophan into indole, and as expected, indole levels were reduced by the production of YafQ. Corroborating the effect of YafQ on persistence, addition of indole reduced persistence. Furthermore, persistence increased upon deleting tnaA, and persistence decreased upon adding tryptophan to the medium to increase indole levels. Also, YafQ production had a much smaller effect on persistence in a strain unable to produce indole. Therefore, YafQ increases persistence by reducing indole, and TA systems are related to cell signalling.
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Affiliation(s)
- Ying Hu
- Department of Chemical Engineering and, Pennsylvania State University, University Park, PA, 16802-4400, USA
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77
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Ruangprasert A, Maehigashi T, Miles SJ, Giridharan N, Liu JX, Dunham CM. Mechanisms of toxin inhibition and transcriptional repression by Escherichia coli DinJ-YafQ. J Biol Chem 2014; 289:20559-69. [PMID: 24898247 PMCID: PMC4110269 DOI: 10.1074/jbc.m114.573006] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 05/29/2014] [Indexed: 01/26/2023] Open
Abstract
Bacteria encounter environmental stresses that regulate a gene expression program required for adaptation and survival. Here, we report the 1.8-Å crystal structure of the Escherichia coli toxin-antitoxin complex YafQ-(DinJ)2-YafQ, a key component of the stress response. The antitoxin DinJ dimer adopts a ribbon-helix-helix motif required for transcriptional autorepression, and toxin YafQ contains a microbial RNase fold whose proposed active site is concealed by DinJ binding. Contrary to previous reports, our studies indicate that equivalent levels of transcriptional repression occur by direct interaction of either YafQ-(DinJ)2-YafQ or a DinJ dimer at a single inverted repeat of its recognition sequence that overlaps with the -10 promoter region. Surprisingly, multiple YafQ-(DinJ)2-YafQ complexes binding to the operator region do not appear to amplify the extent of repression. Our results suggest an alternative model for transcriptional autorepression that may be novel to DinJ-YafQ.
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Affiliation(s)
- Ajchareeya Ruangprasert
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Tatsuya Maehigashi
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Stacey J Miles
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Nisha Giridharan
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Julie X Liu
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Christine M Dunham
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
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78
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Liang Y, Gao Z, Wang F, Zhang Y, Dong Y, Liu Q. Structural and functional characterization of Escherichia coli toxin-antitoxin complex DinJ-YafQ. J Biol Chem 2014; 289:21191-202. [PMID: 24923448 DOI: 10.1074/jbc.m114.559773] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Toxin YafQ functions as a ribonuclease in the dinJ-yafQ toxin-antitoxin system of Escherichia coli. Antitoxin DinJ neutralizes YafQ-mediated toxicity by forming a stable protein complex. Here, crystal structures of the (DinJ)2-(YafQ)2 complex and the isolated YafQ toxin have been determined. The structure of the heterotetrameric complex (DinJ)2-(YafQ)2 revealed that the N-terminal region of DinJ folds into a ribbon-helix-helix motif and dimerizes for DNA recognition, and the C-terminal portion of each DinJ exclusively wraps around a YafQ molecule. Upon incorporation into the heterotetrameric complex, a conformational change of YafQ in close proximity to the catalytic site of the typical microbial ribonuclease fold was observed and validated. Mutagenesis experiments revealed that a DinJ mutant restored YafQ RNase activity in a tetramer complex in vitro but not in vivo. An electrophoretic mobility shift assay showed that one of the palindromic sequences present in the upstream intergenic region of DinJ served as a binding sequences for both the DinJ-YafQ complex and the antitoxin DinJ alone. Based on structure-guided and site-directed mutagenesis of DinJ-YafQ, we showed that two pairs of amino acids in DinJ were important for DNA binding; the R8A and K16A substitutions and the S31A and R35A substitutions in DinJ abolished the DNA binding ability of the DinJ-YafQ complex.
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Affiliation(s)
- Yajing Liang
- From the School of Life Sciences, University of Science and Technology of China, Hefei, Anhui Province 230027, China, the Multidiscipline Research Center, Institute of High Energy Physics of the Chinese Academy of Sciences, 19B Yuequan Road, Beijing 100049, China, and
| | - Zengqiang Gao
- the Multidiscipline Research Center, Institute of High Energy Physics of the Chinese Academy of Sciences, 19B Yuequan Road, Beijing 100049, China, and
| | - Fei Wang
- the Multidiscipline Research Center, Institute of High Energy Physics of the Chinese Academy of Sciences, 19B Yuequan Road, Beijing 100049, China, and
| | - Yangli Zhang
- the Key Laboratory of Molecular Biology on Infectious Disease, Chongqing Medical University, YiXueYuanlu-1, Chongqing 400016, China
| | - Yuhui Dong
- the Multidiscipline Research Center, Institute of High Energy Physics of the Chinese Academy of Sciences, 19B Yuequan Road, Beijing 100049, China, and
| | - Quansheng Liu
- the Multidiscipline Research Center, Institute of High Energy Physics of the Chinese Academy of Sciences, 19B Yuequan Road, Beijing 100049, China, and
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The C-Terminal Portion of an Archaeal Toxin, aRelE, Plays a Crucial Role in Protein Synthesis Inhibition. Biosci Biotechnol Biochem 2014; 73:2766-8. [DOI: 10.1271/bbb.90485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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80
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Im H, Jang SB, Pathak C, Yang YJ, Yoon HJ, Yu TK, Suh JY, Lee BJ. Crystal structure of toxin HP0892 from Helicobacter pylori with two Zn(II) at 1.8 Å resolution. Protein Sci 2014; 23:819-32. [PMID: 24677509 DOI: 10.1002/pro.2465] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 03/05/2014] [Accepted: 03/22/2014] [Indexed: 11/11/2022]
Abstract
Antibiotic resistance and microorganism virulence have been consistently exhibited by bacteria and archaea, which survive in conditions of environmental stress through toxin-antitoxin (TA) systems. The HP0892-HP0893 TA system is one of the two known TA systems belonging to Helicobacter pylori. The antitoxin, HP0893, binds and inhibits the HP0892 toxin and regulates the transcription of the TA operon. Here, we present the crystal structure of the zinc-bound HP0892 toxin at 1.8 Å resolution. Reorientation of residues at the mRNase active site was shown. The involved residues, namely E58A, H86A, and H58A/ H60A, were mutated and the binding affinity was monitored by ITC studies. Through the structural difference between the apo and the metal-bound state, and using a homology modeling tool, the involvement of the metal ion in mRNase active site could be identified. The most catalytically important residue, His86, reorients itself to exhibit RNase activity. His47, Glu58, and His60 are involved in metal binding where Glu58 acts as a general base and His47 and His60 may also act as a general acid in enzymatic activity. Glu58 and Asp64 are involved in substrate binding and specific sequence recognition. Arg83 is involved in phosphate binding and stabilization of the transition state, and Phe90 is involved in base packing and substrate orientation.
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Affiliation(s)
- Hookang Im
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, 151-742, Korea
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81
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An RNA-seq method for defining endoribonuclease cleavage specificity identifies dual rRNA substrates for toxin MazF-mt3. Nat Commun 2014; 5:3538. [PMID: 24709835 PMCID: PMC4090939 DOI: 10.1038/ncomms4538] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 03/03/2014] [Indexed: 11/10/2022] Open
Abstract
Toxin-antitoxin (TA) systems are widespread in prokaryotes. Among these, the mazEF TA system encodes an endoribonucleolytic toxin, MazF, that inhibits growth by sequence-specific cleavage of single-stranded RNA. Defining the physiological targets of a MazF toxin first requires the identification of its cleavage specificity, yet the current toolkit is antiquated and limited. We describe a rapid genome-scale approach, MORE (Mapping by Overexpression of an RNase in Escherichia coli) RNA-seq, for defining the cleavage specificity of endoribonucleolytic toxins. Application of MORE RNA-seq to MazF-mt3 from Mycobacterium tuberculosis reveals two critical ribosomal targets — the essential, evolutionarily conserved helix/loop 70 of 23S rRNA and the anti-Shine-Dalgarno (aSD) sequence of 16S rRNA. Our findings support an emerging model where both rRNA and mRNA are principal targets of MazF toxins and suggest that, as in E. coli, removal of the aSD sequence by a MazF toxin modifies ribosomes to selectively translate leaderless mRNAs in M. tuberculosis.
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82
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Hino M, Zhang J, Takagi H, Miyoshi T, Uchiumi T, Nakashima T, Kakuta Y, Kimura M. Characterization of putative toxin/antitoxin systems in Vibrio parahaemolyticus. J Appl Microbiol 2014; 117:185-95. [PMID: 24698443 DOI: 10.1111/jam.12513] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 03/16/2014] [Accepted: 03/27/2014] [Indexed: 11/29/2022]
Abstract
AIM To obtain more information about the toxin/antitoxin (TA) systems in the Vibrio genus and also to examine their involvement in the induction of a viable but nonculturable (VBNC) state, we searched homologues of the Escherichia coli TA systems in the Vibrio parahaemolyticus genome. METHODS AND RESULTS We found that a gene cluster, vp1842/vp1843, in the V. parahaemolyticus genome database has homology to that encoding the E. coli TA proteins, DinJ/YafQ. Expression of the putative toxin gene vp1843 in E. coli cells strongly inhibited the cell growth, while coexpression with the putative antitoxin gene vp1842 neutralized this effect. Mutational analysis identified Lys37 and Pro45 in the gene product VP1843 of vp1843 as crucial residues for the growth retardation of E. coli cells. VP1843, unlike the E. coli toxin YafQ, has no protein synthesis inhibitory activity, and that instead the expression of vp1843 in E. coli caused morphological change of the cells. CONCLUSIONS The gene cluster vp1842/vp1843 encodes the V. parahaemolyticus TA system; VP1843 inhibits cell growth, whereas VP1842 serves as an antitoxin by forming a stable complex with VP1843. SIGNIFICANCE AND IMPACT OF THE STUDY The putative toxin, VP1843, may be involved in the induction of the VBNC state in V. parahaemolyticus by inhibiting cell division.
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Affiliation(s)
- M Hino
- Department of Health and Nutrition Sciences, Faculty of Health and Nutrition, Nishikyushu University, Kanzaki-shi, Saga, Japan
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Martínez LC, Vadyvaloo V. Mechanisms of post-transcriptional gene regulation in bacterial biofilms. Front Cell Infect Microbiol 2014; 4:38. [PMID: 24724055 PMCID: PMC3971182 DOI: 10.3389/fcimb.2014.00038] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 03/08/2014] [Indexed: 12/19/2022] Open
Abstract
Biofilms are characterized by a dense multicellular community of microorganisms that can be formed by the attachment of bacteria to an inert surface and to each other. The development of biofilm involves the initial attachment of planktonic bacteria to a surface, followed by replication, cell-to-cell adhesion to form microcolonies, maturation, and detachment. Mature biofilms are embedded in a self-produced extracellular polymeric matrix composed primarily of bacterial-derived exopolysaccharides, specialized proteins, adhesins, and occasionally DNA. Because the synthesis and assembly of biofilm matrix components is an exceptionally complex process, the transition between its different phases requires the coordinate expression and simultaneous regulation of many genes by complex genetic networks involving all levels of gene regulation. The finely controlled intracellular level of the chemical second messenger molecule, cyclic-di-GMP is central to the post-transcriptional mechanisms governing the switch between the motile planktonic lifestyle and the sessile biofilm forming state in many bacteria. Several other post-transcriptional regulatory mechanisms are known to dictate biofilm development and assembly and these include RNA-binding proteins, small non-coding RNAs, toxin-antitoxin systems, riboswitches, and RNases. Post-transcriptional regulation is therefore a powerful molecular mechanism employed by bacteria to rapidly adjust to the changing environment and to fine tune gene expression to the developmental needs of the cell. In this review, we discuss post-transcriptional mechanisms that influence the biofilm developmental cycle in a variety of pathogenic bacteria.
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Affiliation(s)
| | - Viveka Vadyvaloo
- Paul G. Allen School for Global Animal Health, Washington State UniversityPullman, WA, USA
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84
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Brzozowska I, Zielenkiewicz U. The ClpXP protease is responsible for the degradation of the Epsilon antidote to the Zeta toxin of the streptococcal pSM19035 plasmid. J Biol Chem 2014; 289:7514-23. [PMID: 24492616 DOI: 10.1074/jbc.m113.519488] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most bacterial genomes contain different types of toxin-antitoxin (TA) systems. The ω-ε-ζ proteinaceous type II TA cassette from the streptococcal pSM19035 plasmid is a member of the ε/ζ family, which is commonly found in multiresistance plasmids and chromosomes of various human pathogens. Regulation of type II TA systems relies on the proteolysis of antitoxin proteins. Under normal conditions, the Epsilon antidote neutralizes the Zeta toxin through the formation of a tight complex. In this study, we show, using both in vivo and in vitro analyses, that the ClpXP protease is responsible for Epsilon antitoxin degradation. Using in vivo studies, we examined the stability of the plasmids with active or inactive ω-ε-ζ TA cassettes in B. subtilis mutants that were defective for different proteases. Using in vitro assays, the degradation of purified His6-Epsilon by the His6-LonBs, ClpPBs, and ClpXBs proteases from B. subtilis was analyzed. Additionally, we showed that purified Zeta toxin protects the Epsilon protein from rapid ClpXP-catalyzed degradation.
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Affiliation(s)
- Iwona Brzozowska
- From the Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
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85
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Bertram R, Schuster CF. Post-transcriptional regulation of gene expression in bacterial pathogens by toxin-antitoxin systems. Front Cell Infect Microbiol 2014; 4:6. [PMID: 24524029 PMCID: PMC3905216 DOI: 10.3389/fcimb.2014.00006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 01/13/2014] [Indexed: 01/27/2023] Open
Abstract
Toxin-antitoxin (TA) systems are small genetic elements ubiquitous in prokaryotic genomes that encode toxic proteins targeting various vital cellular functions. Typically, toxin activity is controlled by adjacently encoded protein or RNA antitoxins and unleashed as a consequence of genetic fluctuations or stressful conditions. Whereas some TA systems interfere with replication or cell wall synthesis, most of them influence transcriptional and post-transcriptional gene regulation. Antitoxin proteins often act as DNA binding transcriptional regulators and many TA toxins exhibit endoribonuclease activity to selectively degrade different RNA species and thus alter gene expression patterns. Some TA RNases cleave tRNA, tmRNAs or rRNAs, whereas most commonly mRNAs either in association with the ribosome or as free transcripts, are targeted. Examples are provided on how TA toxins differentially shape gene expression in bacterial pathogens by creating specialized ribosomes or by altering the transcriptome and how this may be tied in the control of pathogenicity factors.
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Affiliation(s)
- Ralph Bertram
- Department of Microbial Genetics, Faculty of Science, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen Tübingen, Germany
| | - Christopher F Schuster
- Department of Microbial Genetics, Faculty of Science, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen Tübingen, Germany
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86
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Schureck MA, Maehigashi T, Miles SJ, Marquez J, Cho SE, Erdman R, Dunham CM. Structure of the Proteus vulgaris HigB-(HigA)2-HigB toxin-antitoxin complex. J Biol Chem 2014; 289:1060-70. [PMID: 24257752 PMCID: PMC3887174 DOI: 10.1074/jbc.m113.512095] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 10/28/2013] [Indexed: 01/08/2023] Open
Abstract
Bacterial toxin-antitoxin (TA) systems regulate key cellular processes to promote cell survival during periods of stress. During steady-state cell growth, antitoxins typically interact with their cognate toxins to inhibit activity presumably by preventing substrate recognition. We solved two x-ray crystal structures of the Proteus vulgaris tetrameric HigB-(HigA)2-HigB TA complex and found that, unlike most other TA systems, the antitoxin HigA makes minimal interactions with toxin HigB. HigB adopts a RelE family tertiary fold containing a highly conserved concave surface where we predict its active site is located. HigA does not cover the solvent-exposed HigB active site, suggesting that, in general, toxin inhibition is not solely mediated by active site hindrance by its antitoxin. Each HigA monomer contains a helix-turn-helix motif that binds to its own DNA operator to repress transcription during normal cellular growth. This is distinct from antitoxins belonging to other superfamilies that typically only form DNA-binding motifs upon dimerization. We further show that disruption of the HigB-(HigA)2-HigB tetramer to a HigBA heterodimer ablates operator binding. Taken together, our biochemical and structural studies elucidate the novel molecular details of the HigBA TA system.
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MESH Headings
- Amino Acid Sequence
- Antitoxins/chemistry
- Antitoxins/genetics
- Antitoxins/metabolism
- Bacterial Proteins/chemistry
- Bacterial Proteins/genetics
- Bacterial Proteins/metabolism
- Catalytic Domain
- Crystallography, X-Ray
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- DNA, Bacterial/metabolism
- Electrophoresis, Polyacrylamide Gel
- Models, Molecular
- Molecular Sequence Data
- Multiprotein Complexes/chemistry
- Multiprotein Complexes/metabolism
- Nucleic Acid Conformation
- Promoter Regions, Genetic/genetics
- Protein Binding
- Protein Multimerization
- Protein Structure, Quaternary
- Protein Structure, Tertiary
- Proteus vulgaris/genetics
- Proteus vulgaris/metabolism
- Repressor Proteins/chemistry
- Repressor Proteins/genetics
- Repressor Proteins/metabolism
- Ribosomes/chemistry
- Ribosomes/metabolism
- Sequence Homology, Amino Acid
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Affiliation(s)
- Marc A. Schureck
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Tatsuya Maehigashi
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Stacey J. Miles
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Jhomar Marquez
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Shein Ei Cho
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Rachel Erdman
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Christine M. Dunham
- From the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
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87
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Toxin-antitoxin systems as multilevel interaction systems. Toxins (Basel) 2014; 6:304-24. [PMID: 24434905 PMCID: PMC3920263 DOI: 10.3390/toxins6010304] [Citation(s) in RCA: 172] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 12/19/2013] [Accepted: 12/27/2013] [Indexed: 01/05/2023] Open
Abstract
Toxin-antitoxin (TA) systems are small genetic modules usually composed of a toxin and an antitoxin counteracting the activity of the toxic protein. These systems are widely spread in bacterial and archaeal genomes. TA systems have been assigned many functions, ranging from persistence to DNA stabilization or protection against mobile genetic elements. They are classified in five types, depending on the nature and mode of action of the antitoxin. In type I and III, antitoxins are RNAs that either inhibit the synthesis of the toxin or sequester it. In type II, IV and V, antitoxins are proteins that either sequester, counterbalance toxin activity or inhibit toxin synthesis. In addition to these interactions between the antitoxin and toxin components (RNA-RNA, protein-protein, RNA-protein), TA systems interact with a variety of cellular factors, e.g., toxins target essential cellular components, antitoxins are degraded by RNAses or ATP-dependent proteases. Hence, TA systems have the capacity to interact with each other at different levels. In this review, we will discuss the different interactions in which TA systems are involved and their implications in TA system functions and evolution.
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88
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Ning D, Liu S, Xu W, Zhuang Q, Wen C, Tang X. Transcriptional and proteolytic regulation of the toxin-antitoxin locus vapBC10 (ssr2962/slr1767) on the chromosome of Synechocystis sp. PCC 6803. PLoS One 2013; 8:e80716. [PMID: 24260461 PMCID: PMC3834315 DOI: 10.1371/journal.pone.0080716] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 10/07/2013] [Indexed: 12/01/2022] Open
Abstract
VapBC toxin-antitoxin (TA) systems are defined by the association of a PIN-domain toxin with a DNA-binding antitoxin, and are thought to play important physiological roles in bacteria and archaea. Recently, the PIN-associated gene pair PIN-COG2442 was proposed to encode VapBC-family TA system and found to be abundant in cyanobacteria. However, the features of these predicted TA loci remain under investigation. We here report characterization of the PIN-COG2442 locus vapBC10 (ssr2962/slr1767) on the chromosome of Synechocystis sp. PCC 6803. RT-PCR analysis revealed that the vapBC10 genes were co-transcribed under normal growth conditions. Ectopic expression of the PIN-domain protein VapC10 caused growth arrest of Escherichia coli that does not possess vapBC TA locus. Coincidentally, this growth-inhibition effect could be neutralized by either simultaneous or subsequent production of the COG2442-domain protein VapB10 through formation of the TA complex VapBC10 in vivo. In contrast to the transcription repression activity of the well-studied antitoxins, VapB10 positively auto-regulated the transcription of its own operon via specific binding to the promoter region. Furthermore, in vivo experiments in E. coli demonstrated that the Synechocystis protease ClpXP2s, rather than Lons, could cleave VapB10 and proteolytically activate the VapC10 toxicity. Our results show that the PIN-COG2442 locus vapBC10 encodes a functional VapBC TA system with an alternative mechanism for the transcriptional auto-regulation of its own operon.
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Affiliation(s)
- Degang Ning
- Department of Environment Sciences, School of the Environment, Jiangsu University, Zhenjiang, Jiangsu, China
| | - Shuibing Liu
- Department of Environment Sciences, School of the Environment, Jiangsu University, Zhenjiang, Jiangsu, China
| | - Weidong Xu
- Department of Pharmaceutical engineering, School of Pharmacy, Jiangsu University, Xuefu Road, Zhenjiang, Jiangsu, China
| | - Qiang Zhuang
- Department of Environment Sciences, School of the Environment, Jiangsu University, Zhenjiang, Jiangsu, China
| | - Chongwei Wen
- Department of Pharmaceutical engineering, School of Pharmacy, Jiangsu University, Xuefu Road, Zhenjiang, Jiangsu, China
| | - Xiaoxia Tang
- Department of Environment Sciences, School of the Environment, Jiangsu University, Zhenjiang, Jiangsu, China
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89
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Das U, Shuman S. 2'-Phosphate cyclase activity of RtcA: a potential rationale for the operon organization of RtcA with an RNA repair ligase RtcB in Escherichia coli and other bacterial taxa. RNA (NEW YORK, N.Y.) 2013; 19:1355-62. [PMID: 23945037 PMCID: PMC3854526 DOI: 10.1261/rna.039917.113] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 06/20/2013] [Indexed: 05/19/2023]
Abstract
RNA terminal phosphate cyclase catalyzes the ATP-dependent conversion of a 3'-phosphate RNA end to a 2',3'-cyclic phosphate via covalent enzyme-(histidinyl-Nε)-AMP and RNA(3')pp(5')A intermediates. Here, we report that Escherichia coli RtcA (and its human homolog Rtc1) are capable of cyclizing a 2'-phosphate RNA end in high yield. The rate of 2'-phosphate cyclization by RtcA is five orders of magnitude slower than 3'-phosphate cyclization, notwithstanding that RtcA binds with similar affinity to RNA3'p and RNA2'p substrates. These findings expand the functional repertoire of RNA cyclase and suggest that phosphate geometry during adenylate transfer to RNA is a major factor in the kinetics of cyclization. RtcA is coregulated in an operon with an RNA ligase, RtcB, that splices RNA 5'-OH ends to either 3'-phosphate or 2',3'-cyclic phosphate ends. Our results suggest that RtcA might serve an end healing function in an RNA repair pathway, by converting RNA 2'-phosphates, which cannot be spliced by RtcB, to 2',3'-cyclic phosphates that can be sealed. The rtcBA operon is controlled by the σ(54) coactivator RtcR encoded by an adjacent gene. This operon arrangement is conserved in diverse bacterial taxa, many of which have also incorporated the RNA-binding protein Ro (which is implicated in RNA quality control under stress conditions) as a coregulated component of the operon.
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90
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Pathak C, Im H, Yang YJ, Yoon HJ, Kim HM, Kwon AR, Lee BJ. Crystal structure of apo and copper bound HP0894 toxin from Helicobacter pylori 26695 and insight into mRNase activity. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2579-90. [PMID: 24060809 DOI: 10.1016/j.bbapap.2013.09.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 09/13/2013] [Accepted: 09/14/2013] [Indexed: 11/18/2022]
Abstract
The toxin-antitoxin (TA) systems widely spread among bacteria and archaea are important for antibiotic resistance and microorganism virulence. The bacterial kingdom uses TA systems to adjust the global level of gene expression and translation through RNA degradation. In Helicobacter pylori, only two TA systems are known thus far. Our previous studies showed that HP0894-HP0895 acts as a TA system and that HP0894 exhibits intrinsic RNase activity. However, the precise molecular basis for interaction with substrate or antitoxin and the mechanism of mRNA cleavage remain unclear. Therefore, in an attempt to shed some light on the mechanism behind the TA system of HP0894-HP0895, here we present the crystal structures of apo- and metal-bound H. pylori 0894 at 1.28Å and 1.89Å, respectively. Through the combined approach of structural analysis and structural homology search, the amino acids involved in mRNase active site were monitored and the reorientations of different residues were discussed in detail. In the mRNase active site of HP0894 toxin, His84 acts as a catalytic residue and reorients itself to exhibit this type of activity, acting as a general acid in an acid-base catalysis reaction, while His47 and His60 stabilize the transition state. Lys52, Glu58, Asp64 and Arg80 have phosphate binding and specific sequence recognition. Glu58 also acts as a general base, and substrate reorientation is caused by Phe88. Based on experimental findings, a model for antitoxin binding could be suggested.
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Affiliation(s)
- Chinar Pathak
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea
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91
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Cleavage of the antitoxin of the parD toxin–antitoxin system is determined by the ClpAP protease and is modulated by the relative ratio of the toxin and the antitoxin. Plasmid 2013; 70:78-85. [DOI: 10.1016/j.plasmid.2013.01.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2012] [Revised: 01/29/2013] [Accepted: 01/30/2013] [Indexed: 11/21/2022]
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92
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Regulation of toxin–antitoxin systems by proteolysis. Plasmid 2013; 70:33-41. [DOI: 10.1016/j.plasmid.2013.01.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 01/24/2013] [Accepted: 01/25/2013] [Indexed: 11/19/2022]
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93
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Abstract
Bacterial type II toxin-antitoxin systems are widespread in bacteria. Among them, the RelE toxin family is one of the most abundant. The RelE(K-12) toxin of Escherichia coli K-12 represents the paradigm for this family and has been extensively studied, both in vivo and in vitro. RelE(K-12) is an endoribonuclease that cleaves mRNAs that are translated by the ribosome machinery as these transcripts enter the A site. Earlier in vivo reports showed that RelE(K-12) cleaves preferentially in the 5'-end coding region of the transcripts in a codon-independent manner. To investigate whether the molecular activity as well as the cleavage pattern are conserved within the members of this toxin family, RelE-like sequences were selected in Proteobacteria, Cyanobacteria, Actinobacteria, and Spirochaetes and tested in E. coli. Our results show that these RelE-like sequences are part of toxin-antitoxin gene pairs, and that they inhibit translation in E. coli by cleaving transcripts that are being translated. Primer extension analyses show that these toxins exhibit specific cleavage patterns in vivo, both in terms of frequency and location of cleavage sites. We did not observe codon-dependent cleavage but rather a trend to cleave upstream purines and between the second and third positions of codons, except for the actinobacterial toxin. Our results suggest that RelE-like toxins have evolved to rapidly and efficiently shut down translation in a large spectrum of bacterial species, which correlates with the observation that toxin-antitoxin systems are spreading by horizontal gene transfer.
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94
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Ning D, Jiang Y, Liu Z, Xu Q. Characterization of a chromosomal type II toxin-antitoxin system mazEaFa in the Cyanobacterium Anabaena sp. PCC 7120. PLoS One 2013; 8:e56035. [PMID: 23451033 PMCID: PMC3581536 DOI: 10.1371/journal.pone.0056035] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 01/04/2013] [Indexed: 01/04/2023] Open
Abstract
Cyanobacteria have evolved to survive stressful environmental changes by regulating growth, however, the underlying mechanism for this is obscure. The ability of chromosomal type II toxin-antitoxin (TA) systems to modulate growth or cell death has been documented in a variety of prokaryotes. A chromosomal mazEaFa locus of Anabaena sp. PCC 7120 has been predicted as a putative mazEF TA system. Here we demonstrate that mazEaFa form a bicistronic operon that is co-transcribed under normal growth conditions. Overproduction of MazFa induced Anabaena growth arrest which could be neutralized by co-expression of MazEa. MazFa also inhibited the growth of Escherichia coli cells, and this effect could be overcome by simultaneous or subsequent expression of MazEa via formation of the MazEa-MazFa complex in vivo, further confirming the nature of the mazEaFa locus as a type II TA system. Interestingly, like most TA systems, deletion of mazEaFa had no effect on the growth of Anabaena during the tested stresses. Our data suggest that mazEaFa, or together with other chromosomal type II TA systems, may promote cells to cope with particular stresses by inducing reversible growth arrest of Anabaena.
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Affiliation(s)
- Degang Ning
- Department of Environment Sciences, School of the Environment, Jiangsu University, Zhenjiang, Jiangsu, China
| | - Yan Jiang
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu, China
| | - Zhaoying Liu
- Department of Environment Sciences, School of the Environment, Jiangsu University, Zhenjiang, Jiangsu, China
| | - Qinggang Xu
- Institute of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu, China
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95
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Kasari V, Mets T, Tenson T, Kaldalu N. Transcriptional cross-activation between toxin-antitoxin systems of Escherichia coli. BMC Microbiol 2013; 13:45. [PMID: 23432955 PMCID: PMC3598666 DOI: 10.1186/1471-2180-13-45] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 02/18/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Bacterial toxin-antitoxin (TA) systems are formed by potent regulatory or suicide factors (toxins) and their short-lived inhibitors (antitoxins). Antitoxins are DNA-binding proteins and auto-repress transcription of TA operons. Transcription of multiple TA operons is activated in temporarily non-growing persister cells that can resist killing by antibiotics. Consequently, the antitoxin levels of persisters must have been dropped and toxins are released of inhibition. RESULTS Here, we describe transcriptional cross-activation between different TA systems of Escherichia coli. We find that the chromosomal relBEF operon is activated in response to production of the toxins MazF, MqsR, HicA, and HipA. Expression of the RelE toxin in turn induces transcription of several TA operons. We show that induction of mazEF during amino acid starvation depends on relBE and does not occur in a relBEF deletion mutant. Induction of TA operons has been previously shown to depend on Lon protease which is activated by polyphospate accumulation. We show that transcriptional cross-activation occurs also in strains deficient for Lon, ClpP, and HslV proteases and polyphosphate kinase. Furthermore, we find that toxins cleave the TA mRNA in vivo, which is followed by degradation of the antitoxin-encoding fragments and selective accumulation of the toxin-encoding regions. We show that these accumulating fragments can be translated to produce more toxin. CONCLUSION Transcriptional activation followed by cleavage of the mRNA and disproportionate production of the toxin constitutes a possible positive feedback loop, which can fire other TA systems and cause bistable growth heterogeneity. Cross-interacting TA systems have a potential to form a complex network of mutually activating regulators in bacteria.
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Affiliation(s)
- Villu Kasari
- Institute of Technology, University of Tartu, Nooruse 1, 50411, Tartu, Estonia
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96
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Han KD, Ahn DH, Lee SA, Min YH, Kwon AR, Ahn HC, Lee BJ. Identification of chromosomal HP0892-HP0893 toxin-antitoxin proteins in Helicobacter pylori and structural elucidation of their protein-protein interaction. J Biol Chem 2013; 288:6004-13. [PMID: 23297406 PMCID: PMC3581365 DOI: 10.1074/jbc.m111.322784] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacterial chromosomal toxin-antitoxin (TA) systems have been proposed not only to play an important role in the stress response, but also to be associated with antibiotic resistance. Here, we identified the chromosomal HP0892-HP0893 TA proteins in the gastric pathogen, Helicobacter pylori, and structurally characterized their protein-protein interaction. Previously, HP0892 protein was suggested to be a putative TA toxin based on its structural similarity to other RelE family TA toxins. In this study, we demonstrated that HP0892 binds to HP0893 strongly with a stoichiometry of 1:1, and HP0892-HP0893 interaction occurs mainly between the N-terminal secondary structure elements of HP0892 and the C-terminal region of HP0893. HP0892 cleaved mRNA in vitro, preferentially at the 5' end of A or G, and the RNase activity of HP0892 was inhibited by HP0893. In addition, heterologous expression of HP0892 in Escherichia coli cells led to cell growth arrest, and the cell toxicity of HP0892 was neutralized by co-expression with HP0893. From these results and a structural comparison with other TA toxins, it is concluded that HP0892 is a toxin with intrinsic RNase activity and HP0893 is an antitoxin against HP0892 from a TA system of H. pylori. It has been known that hp0893 gene and another TA antitoxin gene, hp0895, of H. pylori, are both genomic open reading frames that correspond to genes that are potentially expressed in response to interactions with the human gastric mucosa. Therefore, it is highly probable that TA systems of H. pylori are involved in virulence of H. pylori.
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Affiliation(s)
- Kyung-Doo Han
- Advanced Analysis Center, Korea Institute of Science and Technology, Seoungbuk-gu, Seoul 136-791, Korea
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97
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New-found fundamentals of bacterial persistence. Trends Microbiol 2012; 20:577-85. [DOI: 10.1016/j.tim.2012.08.009] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 08/10/2012] [Accepted: 08/17/2012] [Indexed: 12/26/2022]
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98
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Hansen S, Vulić M, Min J, Yen TJ, Schumacher MA, Brennan RG, Lewis K. Regulation of the Escherichia coli HipBA toxin-antitoxin system by proteolysis. PLoS One 2012; 7:e39185. [PMID: 22720069 PMCID: PMC3376134 DOI: 10.1371/journal.pone.0039185] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 05/21/2012] [Indexed: 01/09/2023] Open
Abstract
Bacterial populations produce antibiotic-tolerant persister cells. A number of recent studies point to the involvement of toxin/antitoxin (TA) modules in persister formation. hipBA is a type II TA module that codes for the HipB antitoxin and the HipA toxin. HipA is an EF-Tu kinase, which causes protein synthesis inhibition and dormancy upon phosphorylation of its substrate. Antitoxins are labile proteins that are degraded by one of the cytosolic ATP-dependent proteases. We followed the rate of HipB degradation in different protease deficient strains and found that HipB was stabilized in a lon(-) background. These findings were confirmed in an in vitro degradation assay, showing that Lon is the main protease responsible for HipB proteolysis. Moreover, we demonstrated that degradation of HipB is dependent on the presence of an unstructured carboxy-terminal stretch of HipB that encompasses the last 16 amino acid residues. Further, substitution of the conserved carboxy-terminal tryptophan of HipB to alanine or even the complete removal of this 16 residue fragment did not alter the affinity of HipB for hipBA operator DNA or for HipA indicating that the major role of this region of HipB is to control HipB degradation and hence HipA-mediated persistence.
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Affiliation(s)
- Sonja Hansen
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Marin Vulić
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Jungki Min
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Tien-Jui Yen
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Maria A. Schumacher
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Richard G. Brennan
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Kim Lewis
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
- * E-mail:
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Clostridium difficile MazF toxin exhibits selective, not global, mRNA cleavage. J Bacteriol 2012; 194:3464-74. [PMID: 22544268 DOI: 10.1128/jb.00217-12] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Clostridium difficile is an important, emerging nosocomial pathogen. The transition from harmless colonization to disease is typically preceded by antimicrobial therapy, which alters the balance of the intestinal flora, enabling C. difficile to proliferate in the colon. One of the most perplexing aspects of the C. difficile infectious cycle is its ability to survive antimicrobial therapy and transition from inert colonization to active infection. Toxin-antitoxin (TA) systems have been implicated in facilitating persistence after antibiotic treatment. We identified only one TA system in C. difficile strain 630 (epidemic type X), designated MazE-cd and MazF-cd, a counterpart of the well-characterized Escherichia coli MazEF TA system. This E. coli MazF toxin cleaves mRNA at ACA sequences, leading to global mRNA degradation, growth arrest, and death. Likewise, MazF-cd expression in E. coli or Clostridium perfringens resulted in growth arrest. Primer extension analysis revealed that MazF-cd cleaved RNA at the five-base consensus sequence UACAU, suggesting that the mRNAs susceptible to cleavage comprise a subset of total mRNAs. In agreement, we observed differential cleavage of several mRNAs by MazF-cd in vivo, revealing a direct correlation between the number of cleavage recognition sites within a given transcript and its susceptibility to degradation by MazF-cd. Interestingly, upon detailed statistical analyses of the C. difficile transcriptome, the major C. difficile virulence factor toxin B (TcdB) and CwpV, a cell wall protein involved in aggregation, were predicted to be significantly resistant to MazF-cd cleavage.
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Abstract
Almost all bacteria and many archaea contain genes whose expression inhibits cell growth and may lead to cell death when overproduced, reminiscent of apoptotic genes in higher systems. The cellular targets of these toxins are quite diverse and include DNA replication, mRNA stability, protein synthesis, cell-wall biosynthesis, and ATP synthesis. These toxins are co-expressed and neutralized with their cognate antitoxins from a TA (toxin-antitoxin) operon in normally growing cells. Antitoxins are more labile than toxins and are readily degraded under stress conditions, allowing the toxins to exert their toxic effect. Presence of at least 33 TA systems in Escherichia coli and more than 60 TA systems in Mycobacterium tuberculosis suggests that the TA systems are involved not only in normal bacterial physiology but also in pathogenicity of bacteria. The elucidation of their cellular function and regulation is thus crucial for our understanding of bacterial physiology under various stress conditions.
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Affiliation(s)
- Yoshihiro Yamaguchi
- Department of Biochemistry, Center for Advanced Biotechnology and Medicine, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
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