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Peptidyl tRNA Hydrolase Is Required for Robust Prolyl-tRNA Turnover in Mycobacterium tuberculosis. mBio 2023; 14:e0346922. [PMID: 36695586 PMCID: PMC9973355 DOI: 10.1128/mbio.03469-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Enzymes involved in rescuing stalled ribosomes and recycling translation machinery are ubiquitous in bacteria and required for growth. Peptidyl tRNA drop-off is a type of abortive translation that results in the release of a truncated peptide that is still bound to tRNA (peptidyl tRNA) into the cytoplasm. Peptidyl tRNA hydrolase (Pth) recycles the released tRNA by cleaving off the unfinished peptide and is essential in most bacteria. We developed a sequencing-based strategy called copper sulfate-based tRNA sequencing (Cu-tRNAseq) to study the physiological role of Pth in Mycobacterium tuberculosis (Mtb). While most peptidyl tRNA species accumulated in a strain with impaired Pth expression, peptidyl prolyl-tRNA was particularly enriched, suggesting that Pth is required for robust peptidyl prolyl-tRNA turnover. Reducing Pth levels increased Mtb's susceptibility to tRNA synthetase inhibitors that are in development to treat tuberculosis (TB) and rendered this pathogen highly susceptible to macrolides, drugs that are ordinarily ineffective against Mtb. Collectively, our findings reveal the potency of Cu-tRNAseq for profiling peptidyl tRNAs and suggest that targeting Pth would open new therapeutic approaches for TB. IMPORTANCE Peptidyl tRNA hydrolase (Pth) is an enzyme that cuts unfinished peptides off tRNA that has been prematurely released from a stalled ribosome. Pth is essential in nearly all bacteria, including the pathogen Mycobacterium tuberculosis (Mtb), but it has not been clear why. We have used genetic and novel biochemical approaches to show that when Pth levels decline in Mtb, peptidyl tRNA accumulates to such an extent that usable tRNA pools drop. Thus, Pth is needed to maintain normal tRNA levels, most strikingly for prolyl-tRNAs. Many antibiotics act on protein synthesis and could be affected by altering the availability of tRNA. This is certainly true for tRNA synthetase inhibitors, several of which are drug candidates for tuberculosis. We find that their action is potentiated by Pth depletion. Furthermore, Pth depletion results in hypersensitivity to macrolides, drugs that are not active enough under ordinary circumstances to be useful for tuberculosis.
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2
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Kleiber N, Lemus-Diaz N, Stiller C, Heinrichs M, Mai MMQ, Hackert P, Richter-Dennerlein R, Höbartner C, Bohnsack KE, Bohnsack MT. The RNA methyltransferase METTL8 installs m 3C 32 in mitochondrial tRNAs Thr/Ser(UCN) to optimise tRNA structure and mitochondrial translation. Nat Commun 2022; 13:209. [PMID: 35017528 PMCID: PMC8752778 DOI: 10.1038/s41467-021-27905-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 12/14/2021] [Indexed: 12/30/2022] Open
Abstract
Modified nucleotides in tRNAs are important determinants of folding, structure and function. Here we identify METTL8 as a mitochondrial matrix protein and active RNA methyltransferase responsible for installing m3C32 in the human mitochondrial (mt-)tRNAThr and mt-tRNASer(UCN). METTL8 crosslinks to the anticodon stem loop (ASL) of many mt-tRNAs in cells, raising the question of how methylation target specificity is achieved. Dissection of mt-tRNA recognition elements revealed U34G35 and t6A37/(ms2)i6A37, present concomitantly only in the ASLs of the two substrate mt-tRNAs, as key determinants for METTL8-mediated methylation of C32. Several lines of evidence demonstrate the influence of U34, G35, and the m3C32 and t6A37/(ms2)i6A37 modifications in mt-tRNAThr/Ser(UCN) on the structure of these mt-tRNAs. Although mt-tRNAThr/Ser(UCN) lacking METTL8-mediated m3C32 are efficiently aminoacylated and associate with mitochondrial ribosomes, mitochondrial translation is mildly impaired by lack of METTL8. Together these results define the cellular targets of METTL8 and shed new light on the role of m3C32 within mt-tRNAs.
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MESH Headings
- Anticodon/chemistry
- Anticodon/metabolism
- Base Pairing
- Cytosine/metabolism
- Gene Expression Regulation
- HEK293 Cells
- Humans
- Methylation
- Methyltransferases/genetics
- Methyltransferases/metabolism
- Mitochondria/genetics
- Mitochondria/metabolism
- Nucleic Acid Conformation
- Protein Binding
- Protein Biosynthesis
- RNA, Mitochondrial/chemistry
- RNA, Mitochondrial/genetics
- RNA, Mitochondrial/metabolism
- RNA, Transfer, Ser/chemistry
- RNA, Transfer, Ser/genetics
- RNA, Transfer, Ser/metabolism
- RNA, Transfer, Thr/chemistry
- RNA, Transfer, Thr/genetics
- RNA, Transfer, Thr/metabolism
- Signal Transduction
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Affiliation(s)
- Nicole Kleiber
- Department of Molecular Biology, University Medical Centre Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Nicolas Lemus-Diaz
- Department of Molecular Biology, University Medical Centre Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Carina Stiller
- Institute of Organic Chemistry, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Marleen Heinrichs
- Department of Cellular Biochemistry, University Medical Centre Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Mandy Mong-Quyen Mai
- Department of Cellular Biochemistry, University Medical Centre Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Philipp Hackert
- Department of Molecular Biology, University Medical Centre Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Ricarda Richter-Dennerlein
- Department of Cellular Biochemistry, University Medical Centre Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Göttingen, Germany
| | - Claudia Höbartner
- Institute of Organic Chemistry, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Katherine E Bohnsack
- Department of Molecular Biology, University Medical Centre Göttingen, Humboldtallee 23, 37073, Göttingen, Germany.
| | - Markus T Bohnsack
- Department of Molecular Biology, University Medical Centre Göttingen, Humboldtallee 23, 37073, Göttingen, Germany.
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Göttingen, Germany.
- Göttingen Center for Molecular Biosciences, Georg-August University Göttingen, Justus-von-Liebig-Weg 11, Göttingen, 37077, Germany.
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3
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Campos-Silva R, D’Urso G, Delalande O, Giudice E, Macedo AJ, Gillet R. Trans-Translation Is an Appealing Target for the Development of New Antimicrobial Compounds. Microorganisms 2021; 10:3. [PMID: 35056452 PMCID: PMC8778911 DOI: 10.3390/microorganisms10010003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 12/09/2021] [Accepted: 12/16/2021] [Indexed: 01/06/2023] Open
Abstract
Because of the ever-increasing multidrug resistance in microorganisms, it is crucial that we find and develop new antibiotics, especially molecules with different targets and mechanisms of action than those of the antibiotics in use today. Translation is a fundamental process that uses a large portion of the cell's energy, and the ribosome is already the target of more than half of the antibiotics in clinical use. However, this process is highly regulated, and its quality control machinery is actively studied as a possible target for new inhibitors. In bacteria, ribosomal stalling is a frequent event that jeopardizes bacterial wellness, and the most severe form occurs when ribosomes stall at the 3'-end of mRNA molecules devoid of a stop codon. Trans-translation is the principal and most sophisticated quality control mechanism for solving this problem, which would otherwise result in inefficient or even toxic protein synthesis. It is based on the complex made by tmRNA and SmpB, and because trans-translation is absent in eukaryotes, but necessary for bacterial fitness or survival, it is an exciting and realistic target for new antibiotics. Here, we describe the current and future prospects for developing what we hope will be a novel generation of trans-translation inhibitors.
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Affiliation(s)
- Rodrigo Campos-Silva
- CNRS, Institut de Génétique et Développement de Rennes (IGDR) UMR6290, University of Rennes, 35000 Rennes, France; (R.C.-S.); (G.D.); (O.D.); (E.G.)
- Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia and Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre 90610-000, Brazil;
| | - Gaetano D’Urso
- CNRS, Institut de Génétique et Développement de Rennes (IGDR) UMR6290, University of Rennes, 35000 Rennes, France; (R.C.-S.); (G.D.); (O.D.); (E.G.)
| | - Olivier Delalande
- CNRS, Institut de Génétique et Développement de Rennes (IGDR) UMR6290, University of Rennes, 35000 Rennes, France; (R.C.-S.); (G.D.); (O.D.); (E.G.)
| | - Emmanuel Giudice
- CNRS, Institut de Génétique et Développement de Rennes (IGDR) UMR6290, University of Rennes, 35000 Rennes, France; (R.C.-S.); (G.D.); (O.D.); (E.G.)
| | - Alexandre José Macedo
- Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia and Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre 90610-000, Brazil;
| | - Reynald Gillet
- CNRS, Institut de Génétique et Développement de Rennes (IGDR) UMR6290, University of Rennes, 35000 Rennes, France; (R.C.-S.); (G.D.); (O.D.); (E.G.)
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4
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Wang H, Huang R, Li L, Zhu J, Li Z, Peng C, Zhuang X, Lin H, Shi S, Huang P. CPA-seq reveals small ncRNAs with methylated nucleosides and diverse termini. Cell Discov 2021; 7:25. [PMID: 33867522 PMCID: PMC8053708 DOI: 10.1038/s41421-021-00265-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 03/25/2021] [Indexed: 12/20/2022] Open
Abstract
High-throughput sequencing reveals the complex landscape of small noncoding RNAs (sRNAs). However, it is limited by requiring 5'-monophosphate and 3'-hydroxyl in RNAs for adapter ligation and hindered by methylated nucleosides that interfere with reverse transcription. Here we develop Cap-Clip acid pyrophosphatase (Cap-Clip), T4 polynucleotide kinase (PNK) and AlkB/AlkB(D135S)-facilitated small ncRNA sequencing (CPA-seq) to detect and quantify sRNAs with terminus multiplicities and nucleoside methylations. CPA-seq identified a large number of previously undetected sRNAs. Comparison of sRNAs with or without AlkB/AlkB(D135S) treatment reveals nucleoside methylations on sRNAs. Using CPA-seq, we profiled the sRNA transcriptomes (sRNomes) of nine mouse tissues and reported the extensive tissue-specific differences of sRNAs. We also observed the transition of sRNomes during hepatic reprogramming. Knockdown of mesenchymal stem cell-enriched U1-5' snsRNA promoted hepatic reprogramming. CPA-seq is a powerful tool with high sensitivity and specificity for profiling sRNAs with methylated nucleosides and diverse termini.
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Affiliation(s)
- Heming Wang
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China.,University of Chinese Academy of Sciences, Beijing, 100049, China.,CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Rong Huang
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China.,University of Chinese Academy of Sciences, Beijing, 100049, China.,CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Ling Li
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Junjin Zhu
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China.,CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Zhihong Li
- National Facility for Protein Science in Shanghai, Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai, 201210, China
| | - Chao Peng
- National Facility for Protein Science in Shanghai, Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai, 201210, China
| | - Xuran Zhuang
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Haifan Lin
- Yale Stem Cell Center and Department of Cell Biology, Yale University School of Medicine, New Haven, CT, 06520, USA
| | - Shuo Shi
- Shanghai Institute for Advanced Immunochemical Studies (SIAIS), ShanghaiTech University, Shanghai, 201210, China.
| | - Pengyu Huang
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China. .,CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China. .,Institute of Biomedical Engineering, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, 300192, China.
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5
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Queuine Is a Nutritional Regulator of Entamoeba histolytica Response to Oxidative Stress and a Virulence Attenuator. mBio 2021; 12:mBio.03549-20. [PMID: 33688012 PMCID: PMC8092309 DOI: 10.1128/mbio.03549-20] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Entamoeba histolytica is a unicellular parasite that causes amebiasis. The parasite resides in the colon and feeds on the colonic microbiota. Queuosine is a naturally occurring modified ribonucleoside found in the first position of the anticodon of the transfer RNAs for Asp, Asn, His, and Tyr. Eukaryotes lack pathways to synthesize queuine, the nucleobase precursor to queuosine, and must obtain it from diet or gut microbiota. Here, we describe the effects of queuine on the physiology of the eukaryotic parasite Entamoeba histolytica, the causative agent of amebic dysentery. Queuine is efficiently incorporated into E. histolytica tRNAs by a tRNA-guanine transglycosylase (EhTGT) and this incorporation stimulates the methylation of C38 in
tRNAGUCAsp. Queuine protects the parasite against oxidative stress (OS) and antagonizes the negative effect that oxidation has on translation by inducing the expression of genes involved in the OS response, such as heat shock protein 70 (Hsp70), antioxidant enzymes, and enzymes involved in DNA repair. On the other hand, queuine impairs E. histolytica virulence by downregulating the expression of genes previously associated with virulence, including cysteine proteases, cytoskeletal proteins, and small GTPases. Silencing of EhTGT prevents incorporation of queuine into tRNAs and strongly impairs methylation of C38 in
tRNAGUCAsp, parasite growth, resistance to OS, and cytopathic activity. Overall, our data reveal that queuine plays a dual role in promoting OS resistance and reducing parasite virulence.
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6
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Nagayoshi Y, Chujo T, Hirata S, Nakatsuka H, Chen CW, Takakura M, Miyauchi K, Ikeuchi Y, Carlyle BC, Kitchen RR, Suzuki T, Katsuoka F, Yamamoto M, Goto Y, Tanaka M, Natsume K, Nairn AC, Suzuki T, Tomizawa K, Wei FY. Loss of Ftsj1 perturbs codon-specific translation efficiency in the brain and is associated with X-linked intellectual disability. SCIENCE ADVANCES 2021; 7:7/13/eabf3072. [PMID: 33771871 PMCID: PMC7997516 DOI: 10.1126/sciadv.abf3072] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 02/09/2021] [Indexed: 05/06/2023]
Abstract
FtsJ RNA 2'-O-methyltransferase 1 (FTSJ1) gene has been implicated in X-linked intellectual disability (XLID), but the molecular pathogenesis is unknown. We show that Ftsj1 is responsible for 2'-O-methylation of 11 species of cytosolic transfer RNAs (tRNAs) at the anticodon region, and these modifications are abolished in Ftsj1 knockout (KO) mice and XLID patient-derived cells. Loss of 2'-O-methylation in Ftsj1 KO mouse selectively reduced the steady-state level of tRNAPhe in the brain, resulting in a slow decoding at Phe codons. Ribosome profiling showed that translation efficiency is significantly reduced in a subset of genes that need to be efficiently translated to support synaptic organization and functions. Ftsj1 KO mice display immature synaptic morphology and aberrant synaptic plasticity, which are associated with anxiety-like and memory deficits. The data illuminate a fundamental role of tRNA modification in the brain through regulation of translation efficiency and provide mechanistic insights into FTSJ1-related XLID.
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Affiliation(s)
- Y Nagayoshi
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - T Chujo
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - S Hirata
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - H Nakatsuka
- Department of Human Intelligence Systems, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan
| | - C-W Chen
- Laboratory for Protein Conformation Diseases, RIKEN Brain Science Institute, Saitama 351-0198, Japan
| | - M Takakura
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - K Miyauchi
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Y Ikeuchi
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
- Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505, Japan
| | - B C Carlyle
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - R R Kitchen
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - T Suzuki
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - F Katsuoka
- Department of Integrative Genomics, Tohoku Medical Megabank Organization, Tohoku University, Sendai 980-8573, Japan
| | - M Yamamoto
- Department of Integrative Genomics, Tohoku Medical Megabank Organization, Tohoku University, Sendai 980-8573, Japan
- Department of Medical Biochemistry, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan
| | - Y Goto
- Department of Mental Retardation and Birth Defect Research, National Institute of Neurology, NCNP, Tokyo 187-8551, Japan
| | - M Tanaka
- Laboratory for Protein Conformation Diseases, RIKEN Brain Science Institute, Saitama 351-0198, Japan
| | - K Natsume
- Department of Human Intelligence Systems, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan
| | - A C Nairn
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - T Suzuki
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - K Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan.
| | - F-Y Wei
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan.
- Department of Modomics Biology and Medicine, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan
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7
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Rubio A, Ghosh S, Mülleder M, Ralser M, Mata J. Ribosome profiling reveals ribosome stalling on tryptophan codons and ribosome queuing upon oxidative stress in fission yeast. Nucleic Acids Res 2021; 49:383-399. [PMID: 33313903 PMCID: PMC7797079 DOI: 10.1093/nar/gkaa1180] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 11/13/2020] [Accepted: 11/19/2020] [Indexed: 12/11/2022] Open
Abstract
Translational control is essential in response to stress. We investigated the translational programmes launched by the fission yeast Schizosaccharomyces pombe upon five environmental stresses. We also explored the contribution of defence pathways to these programmes: The Integrated Stress Response (ISR), which regulates translation initiation, and the stress-response MAPK pathway. We performed ribosome profiling of cells subjected to each stress, in wild type cells and in cells with the defence pathways inactivated. The transcription factor Fil1, a functional homologue of the yeast Gcn4 and the mammalian Atf4 proteins, was translationally upregulated and required for the response to most stresses. Moreover, many mRNAs encoding proteins required for ribosome biogenesis were translationally downregulated. Thus, several stresses trigger a universal translational response, including reduced ribosome production and a Fil1-mediated transcriptional programme. Surprisingly, ribosomes stalled on tryptophan codons upon oxidative stress, likely due to a decrease in charged tRNA-Tryptophan. Stalling caused ribosome accumulation upstream of tryptophan codons (ribosome queuing/collisions), demonstrating that stalled ribosomes affect translation elongation by other ribosomes. Consistently, tryptophan codon stalling led to reduced translation elongation and contributed to the ISR-mediated inhibition of initiation. We show that different stresses elicit common and specific translational responses, revealing a novel role in Tryptophan-tRNA availability.
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Affiliation(s)
- Angela Rubio
- Department of Biochemistry, University of Cambridge, UK
| | - Sanjay Ghosh
- Department of Biochemistry, University of Cambridge, UK
| | - Michael Mülleder
- The Molecular Biology of Metabolism Laboratory, The Francis Crick Institute, London, UK
| | - Markus Ralser
- The Molecular Biology of Metabolism Laboratory, The Francis Crick Institute, London, UK.,Department of Biochemistry, Charité University Medicine, Berlin, Germany
| | - Juan Mata
- Department of Biochemistry, University of Cambridge, UK
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8
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Cai Y, Usher B, Gutierrez C, Tolcan A, Mansour M, Fineran PC, Condon C, Neyrolles O, Genevaux P, Blower TR. A nucleotidyltransferase toxin inhibits growth of Mycobacterium tuberculosis through inactivation of tRNA acceptor stems. SCIENCE ADVANCES 2020; 6:eabb6651. [PMID: 32923609 PMCID: PMC7450476 DOI: 10.1126/sciadv.abb6651] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 06/12/2020] [Indexed: 05/12/2023]
Abstract
Toxin-antitoxin systems are widespread stress-responsive elements, many of whose functions remain largely unknown. Here, we characterize the four DUF1814-family nucleotidyltransferase-like toxins (MenT1-4) encoded by the human pathogen Mycobacterium tuberculosis. Toxin MenT3 inhibited growth of M. tuberculosis when not antagonized by its cognate antitoxin, MenA3. We solved the structures of toxins MenT3 and MenT4 to 1.6 and 1.2 Å resolution, respectively, and identified the biochemical activity and target of MenT3. MenT3 blocked in vitro protein expression and prevented tRNA charging in vivo. MenT3 added pyrimidines (C or U) to the 3'-CCA acceptor stems of uncharged tRNAs and exhibited strong substrate specificity in vitro, preferentially targeting tRNASer from among the 45 M. tuberculosis tRNAs. Our study identifies a previously unknown mechanism that expands the range of enzymatic activities used by bacterial toxins, uncovering a new way to block protein synthesis and potentially treat tuberculosis and other infections.
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Affiliation(s)
- Yiming Cai
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31400 Toulouse, France
| | - Ben Usher
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Claude Gutierrez
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, 205 route de Narbonne, 31400 Toulouse, France
| | - Anastasia Tolcan
- UMR8261 (CNRS, Université de Paris), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Moise Mansour
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31400 Toulouse, France
| | - Peter C. Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Genetics Otago, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Bio-protection Research Centre, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Ciarán Condon
- UMR8261 (CNRS, Université de Paris), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Olivier Neyrolles
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, 205 route de Narbonne, 31400 Toulouse, France
| | - Pierre Genevaux
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31400 Toulouse, France
| | - Tim R. Blower
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
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9
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Kanno A, Asahara SI, Furubayashi A, Masuda K, Yoshitomi R, Suzuki E, Takai T, Kimura-Koyanagi M, Matsuda T, Bartolome A, Hirota Y, Yokoi N, Inaba Y, Inoue H, Matsumoto M, Inoue K, Abe T, Wei FY, Tomizawa K, Ogawa W, Seino S, Kasuga M, Kido Y. GCN2 regulates pancreatic β cell mass by sensing intracellular amino acid levels. JCI Insight 2020; 5:128820. [PMID: 32376799 DOI: 10.1172/jci.insight.128820] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 04/01/2020] [Indexed: 01/09/2023] Open
Abstract
EIF2AK4, which encodes the amino acid deficiency-sensing protein GCN2, has been implicated as a susceptibility gene for type 2 diabetes in the Japanese population. However, the mechanism by which GCN2 affects glucose homeostasis is unclear. Here, we show that insulin secretion is reduced in individuals harboring the risk allele of EIF2AK4 and that maintenance of GCN2-deficient mice on a high-fat diet results in a loss of pancreatic β cell mass. Our data suggest that GCN2 senses amino acid deficiency in β cells and limits signaling by mechanistic target of rapamycin complex 1 to prevent β cell failure during the consumption of a high-fat diet.
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Affiliation(s)
- Ayumi Kanno
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Shun-Ichiro Asahara
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Ayuko Furubayashi
- Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Science, Kobe, Japan
| | - Katsuhisa Masuda
- Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Science, Kobe, Japan
| | - Risa Yoshitomi
- Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Science, Kobe, Japan
| | - Emi Suzuki
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Tomoko Takai
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | | | - Tomokazu Matsuda
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Alberto Bartolome
- Naomi Berrie Diabetes Center and Department of Medicine, Columbia University, New York, New York, USA
| | - Yushi Hirota
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Norihide Yokoi
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yuka Inaba
- Metabolism and Nutrition Research Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa, Ishikawa, Japan
| | - Hiroshi Inoue
- Metabolism and Nutrition Research Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa, Ishikawa, Japan
| | - Michihiro Matsumoto
- Department of Molecular Metabolic Regulation, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | | | - Takaya Abe
- Laboratory for Animal Resource Development and.,Laboratory for Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Fan-Yan Wei
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Wataru Ogawa
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Masato Kasuga
- National Center for Global Health and Medicine, Tokyo, Japan
| | - Yoshiaki Kido
- Division of Diabetes and Endocrinology, Department of Internal Medicine, and.,Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Science, Kobe, Japan
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10
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Meyer B, Immer C, Kaiser S, Sharma S, Yang J, Watzinger P, Weiß L, Kotter A, Helm M, Seitz HM, Kötter P, Kellner S, Entian KD, Wöhnert J. Identification of the 3-amino-3-carboxypropyl (acp) transferase enzyme responsible for acp3U formation at position 47 in Escherichia coli tRNAs. Nucleic Acids Res 2020; 48:1435-1450. [PMID: 31863583 PMCID: PMC7026641 DOI: 10.1093/nar/gkz1191] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 12/10/2019] [Accepted: 12/11/2019] [Indexed: 02/06/2023] Open
Abstract
tRNAs from all domains of life contain modified nucleotides. However, even for the experimentally most thoroughly characterized model organism Escherichia coli not all tRNA modification enzymes are known. In particular, no enzyme has been found yet for introducing the acp3U modification at position 47 in the variable loop of eight E. coli tRNAs. Here we identify the so far functionally uncharacterized YfiP protein as the SAM-dependent 3-amino-3-carboxypropyl transferase catalyzing this modification and thereby extend the list of known tRNA modification enzymes in E. coli. Similar to the Tsr3 enzymes that introduce acp modifications at U or m1Ψ nucleotides in rRNAs this protein contains a DTW domain suggesting that acp transfer reactions to RNA nucleotides are a general function of DTW domain containing proteins. The introduction of the acp3U-47 modification in E. coli tRNAs is promoted by the presence of the m7G-46 modification as well as by growth in rich medium. However, a deletion of the enzymes responsible for the modifications at position 46 and 47 in the variable loop of E. coli tRNAs did not lead to a clearly discernible phenotype suggesting that these two modifications play only a minor role in ensuring the proper function of tRNAs in E. coli.
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Affiliation(s)
- Britta Meyer
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Carina Immer
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Steffen Kaiser
- Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5, 81377 Munich, Germany
| | - Sunny Sharma
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany.,Department of Cell Biology and Neurosciences, Rutgers University, Piscataway, NJ 08854, USA
| | - Jun Yang
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany.,Department of Cell Biology and Neurosciences, Rutgers University, Piscataway, NJ 08854, USA
| | - Peter Watzinger
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Lena Weiß
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Annika Kotter
- Institute of Pharmacy and Biochemistry, Johannes-Gutenberg-Universität Mainz, Staudingerweg 5, 55128 Mainz, Germany
| | - Mark Helm
- Institute of Pharmacy and Biochemistry, Johannes-Gutenberg-Universität Mainz, Staudingerweg 5, 55128 Mainz, Germany
| | - Hans-Michael Seitz
- Institute for Geosciences, Research Unit Mineralogy, and Frankfurt Isotope and Element Research Center (FIERCE), Goethe-Universität Frankfurt, Altenhöferallee 1, 60438 Frankfurt/M., Germany
| | - Peter Kötter
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Stefanie Kellner
- Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5, 81377 Munich, Germany
| | - Karl-Dieter Entian
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
| | - Jens Wöhnert
- Institute for Molecular Biosciences, Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany.,Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-Universität Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/M., Germany
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11
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Guimaraes JC, Mittal N, Gnann A, Jedlinski D, Riba A, Buczak K, Schmidt A, Zavolan M. A rare codon-based translational program of cell proliferation. Genome Biol 2020; 21:44. [PMID: 32102681 PMCID: PMC7045563 DOI: 10.1186/s13059-020-1943-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Accepted: 01/22/2020] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The speed of translation elongation is primarily determined by the abundance of tRNAs. Thus, the codon usage influences the rate with which individual mRNAs are translated. As the nature of tRNA pools and modifications can vary across biological conditions, codon elongation rates may also vary, leading to fluctuations in the protein production from individual mRNAs. Although it has been observed that functionally related mRNAs exhibit similar codon usage, presumably to provide an effective way to coordinate expression of multiple proteins, experimental evidence for codon-mediated translation efficiency modulation of functionally related mRNAs in specific conditions is scarce and the associated mechanisms are still debated. RESULTS Here, we reveal that mRNAs whose expression increases during cell proliferation are enriched in rare codons, poorly adapted to tRNA pools. Ribosome occupancy profiling and proteomics measurements show that upon increased cell proliferation, transcripts enriched in rare codons undergo a higher translation boost than transcripts with common codons. Re-coding of a fluorescent reporter with rare codons increased protein output by ~ 30% relative to a reporter re-coded with common codons. Although the translation capacity of proliferating cells was higher compared to resting cells, we did not find evidence for the regulation of individual tRNAs. Among the models that were proposed so far to account for codon-mediated translational regulation upon changing conditions, the one that seems most consistent with our data involves a global upregulation of ready-to-translate tRNAs, which we show can lead to a higher increase in the elongation velocity at rare codons compared to common codons. CONCLUSIONS We propose that the alleviation of translation bottlenecks in rapidly dividing cells enables preferential upregulation of pro-proliferation proteins, encoded by mRNAs that are enriched in rare codons.
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Affiliation(s)
- Joao C Guimaraes
- Computational and Systems Biology, Biozentrum University of Basel, Klingelbergstrasse 50-70, 4056, Basel, Switzerland.
| | - Nitish Mittal
- Computational and Systems Biology, Biozentrum University of Basel, Klingelbergstrasse 50-70, 4056, Basel, Switzerland
| | - Alexandra Gnann
- Computational and Systems Biology, Biozentrum University of Basel, Klingelbergstrasse 50-70, 4056, Basel, Switzerland
- Department of Biomedicine, University of Basel/University Hospital Basel, Hebelstrasse 20, 4031, Basel, Switzerland
| | - Dominik Jedlinski
- Computational and Systems Biology, Biozentrum University of Basel, Klingelbergstrasse 50-70, 4056, Basel, Switzerland
| | - Andrea Riba
- Computational and Systems Biology, Biozentrum University of Basel, Klingelbergstrasse 50-70, 4056, Basel, Switzerland
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Université de Strasbourg, 1 rue Laurent Fries, 67404, Illkirch CEDEX, France
| | - Katarzyna Buczak
- Proteomics Core Facility, Biozentrum University of Basel, Klingelbergstrasse 50-70, 4056, Basel, Switzerland
| | - Alexander Schmidt
- Proteomics Core Facility, Biozentrum University of Basel, Klingelbergstrasse 50-70, 4056, Basel, Switzerland
| | - Mihaela Zavolan
- Computational and Systems Biology, Biozentrum University of Basel, Klingelbergstrasse 50-70, 4056, Basel, Switzerland.
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12
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Yin L, Harwood C. Charging State Analysis of Transfer RNA from an α-proteobacterium. Bio Protoc 2020; 10:e3834. [DOI: 10.21769/bioprotoc.3834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 08/31/2020] [Accepted: 09/10/2020] [Indexed: 11/02/2022] Open
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13
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Abstract
Gram-negative bacteria in infections, biofilms, and industrial settings often stop growing due to nutrient depletion, immune responses, or environmental stresses. Bacteria in this state tend to be tolerant to antibiotics and are often referred to as dormant. Rhodopseudomonas palustris, a phototrophic alphaproteobacterium, can remain fully viable for more than 4 months when its growth is arrested. Here, we show that protein synthesis, specific proteins involved in translation, and a stringent response are required for this remarkable longevity. Because it can generate ATP from light during growth arrest, R. palustris is an extreme example of a bacterial species that will stay alive for long periods of time as a relatively homogeneous population of cells and it is thus an excellent model organism for studies of bacterial longevity. There is evidence that other Gram-negative species also continue to synthesize proteins during growth arrest and that a stringent response is required for their longevity as well. Our observations challenge the notion that growth-arrested cells are necessarily dormant and metabolically inactive and suggest that such bacteria may have a level of metabolic activity that is higher than many would have assumed. Our results also expand our mechanistic understanding of a crucial but understudied phase of the bacterial life cycle.IMPORTANCE We are surrounded by bacteria, but they do not completely dominate our planet despite the ability of many to grow extremely rapidly in the laboratory. This has been interpreted to mean that bacteria in nature are often in a dormant state. We investigated life in growth arrest of Rhodopseudomonas palustris, a proteobacterium that stays alive for months when it is not growing. We found that cells were metabolically active, and they continued to synthesize proteins and mounted a stringent response, both of which were required for their longevity. Our results suggest that long-lived bacteria are not necessarily inactive but have an active metabolism that is well adjusted to life without growth.
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14
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Lee YH, Lo YT, Chang CP, Yeh CS, Chang TH, Chen YW, Tseng YK, Wang CC. Naturally occurring dual recognition of tRNA His substrates with and without a universal identity element. RNA Biol 2019; 16:1275-1285. [PMID: 31179821 DOI: 10.1080/15476286.2019.1626663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The extra 5' guanine nucleotide (G-1) on tRNAHis is a nearly universal feature that specifies tRNAHis identity. The G-1 residue is either genome encoded or post-transcriptionally added by tRNAHis guanylyltransferase (Thg1). Despite Caenorhabditis elegans being a Thg1-independent organism, its cytoplasmic tRNAHis (CetRNAnHis) retains a genome-encoded G-1. Our study showed that this eukaryote possesses a histidyl-tRNA synthetase (CeHisRS) gene encoding two distinct HisRS isoforms that differ only at their N-termini. Most interestingly, its mitochondrial tRNAHis (CetRNAmHis) lacks G-1, a scenario never observed in any organelle. This tRNA, while lacking the canonical identity element, can still be efficiently aminoacylated in vivo. Even so, addition of G-1 to CetRNAmHis strongly enhanced its aminoacylation efficiency in vitro. Overexpression of CeHisRS successfully bypassed the requirement for yeast THG1 in the presence of CetRNAnHis without G-1. Mutagenesis assays showed that the anticodon takes a primary role in CetRNAHis identity recognition, being comparable to the universal identity element. Consequently, simultaneous introduction of both G-1 and the anticodon of tRNAHis effectively converted a non-cognate tRNA to a tRNAHis-like substrate. Our study suggests that a new balance between identity elements of tRNAHis relieves HisRS from the absolute requirement for G-1.
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Affiliation(s)
- Yi-Hsueh Lee
- a Department of Life Sciences, National Central University , Taoyuan , Taiwan
| | - Ya-Ting Lo
- a Department of Life Sciences, National Central University , Taoyuan , Taiwan
| | - Chia-Pei Chang
- a Department of Life Sciences, National Central University , Taoyuan , Taiwan
| | - Chung-Shu Yeh
- b Genomics Research Center, Academia Sinica , Taipei , Taiwan
| | | | - Yu-Wei Chen
- c Department of Neurology, Landseed International Hospital , Taoyuan , Taiwan
| | - Yi-Kuan Tseng
- d Graduate Institute of Statistics, National Central University , Taoyuan , Taiwan
| | - Chien-Chia Wang
- a Department of Life Sciences, National Central University , Taoyuan , Taiwan
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15
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Mettl1/Wdr4-Mediated m 7G tRNA Methylome Is Required for Normal mRNA Translation and Embryonic Stem Cell Self-Renewal and Differentiation. Mol Cell 2018; 71:244-255.e5. [PMID: 29983320 DOI: 10.1016/j.molcel.2018.06.001] [Citation(s) in RCA: 269] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/25/2018] [Accepted: 05/31/2018] [Indexed: 01/01/2023]
Abstract
tRNAs are subject to numerous modifications, including methylation. Mutations in the human N7-methylguanosine (m7G) methyltransferase complex METTL1/WDR4 cause primordial dwarfism and brain malformation, yet the molecular and cellular function in mammals is not well understood. We developed m7G methylated tRNA immunoprecipitation sequencing (MeRIP-seq) and tRNA reduction and cleavage sequencing (TRAC-seq) to reveal the m7G tRNA methylome in mouse embryonic stem cells (mESCs). A subset of 22 tRNAs is modified at a "RAGGU" motif within the variable loop. We observe increased ribosome occupancy at the corresponding codons in Mettl1 knockout mESCs, implying widespread effects on tRNA function, ribosome pausing, and mRNA translation. Translation of cell cycle genes and those associated with brain abnormalities is particularly affected. Mettl1 or Wdr4 knockout mESCs display defective self-renewal and neural differentiation. Our study uncovers the complexity of the mammalian m7G tRNA methylome and highlights its essential role in ESCs with links to human disease.
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16
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Singh KP, Miaskowski C, Dhruva AA, Flowers E, Kober KM. Mechanisms and Measurement of Changes in Gene Expression. Biol Res Nurs 2018; 20:369-382. [PMID: 29706088 PMCID: PMC6346310 DOI: 10.1177/1099800418772161] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Research on gene expression (GE) provides insights into the physiology of a cell or group of cells at a given point in time. Studies of changes in GE can be used to identify patients at higher risk for various medical conditions, a higher symptom burden, and/or the adverse consequences associated with various treatments. The aims of this article are as follows: (1) to describe the different types of RNA transcripts, (2) to describe the processes involved in GE (i.e., RNA transcription, epigenetics, and posttranscriptional modifications), (3) to describe common sources of variation in GE, (4) to describe the most common methods used to measure GE, and (5) to discuss factors to consider when choosing tissue for a GE study. This article begins with an overview of the mechanisms involved in GE. Then, the factors that can influence the findings from GE experiments (e.g., tissue specificity, host age, host gender, and time of sample collection) are described and potential solutions are presented. This article concludes with a discussion of how the types of tissue used in GE studies can affect study findings. Given that the costs associated with the measurement of changes in GE are decreasing and the methods to analyze GE data are becoming easier to use, nurse scientists need to understand the basic principles that underlie any GE study.
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Affiliation(s)
- Komal P. Singh
- Department of Physiological Nursing, School of Nursing, University of California, San Francisco, CA, USA
| | - Christine Miaskowski
- Department of Physiological Nursing, School of Nursing, University of California, San Francisco, CA, USA
| | - Anand A. Dhruva
- School of Medicine, University of California, San Francisco, CA, USA
| | - Elena Flowers
- Department of Physiological Nursing, School of Nursing, University of California, San Francisco, CA, USA
| | - Kord M. Kober
- Department of Physiological Nursing, School of Nursing, University of California, San Francisco, CA, USA
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17
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Rycroft JA, Gollan B, Grabe GJ, Hall A, Cheverton AM, Larrouy-Maumus G, Hare SA, Helaine S. Activity of acetyltransferase toxins involved in Salmonella persister formation during macrophage infection. Nat Commun 2018; 9:1993. [PMID: 29777131 PMCID: PMC5959882 DOI: 10.1038/s41467-018-04472-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 04/27/2018] [Indexed: 12/31/2022] Open
Abstract
Non-typhoidal Salmonella strains are responsible for invasive infections associated with high mortality and recurrence in sub-Saharan Africa, and there is strong evidence for clonal relapse following antibiotic treatment. Persisters are non-growing bacteria that are thought to be responsible for the recalcitrance of many infections to antibiotics. Toxin-antitoxin systems are stress-responsive elements that are important for Salmonella persister formation, specifically during infection. Here, we report the analysis of persister formation of clinical invasive strains of Salmonella Typhimurium and Enteritidis in human primary macrophages. We show that all the invasive clinical isolates of both serovars that we tested produce high levels of persisters following internalization by human macrophages. Our genome comparison reveals that S. Enteritidis and S. Typhimurium strains contain three acetyltransferase toxins that we characterize structurally and functionally. We show that all induce the persister state by inhibiting translation through acetylation of aminoacyl-tRNAs. However, they differ in their potency and target partially different subsets of aminoacyl-tRNAs, potentially accounting for their non-redundant effect.
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Affiliation(s)
- Julian A Rycroft
- Section of Microbiology, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK
| | - Bridget Gollan
- Section of Microbiology, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK
| | - Grzegorz J Grabe
- Section of Microbiology, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK
| | - Alexander Hall
- Section of Microbiology, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK
| | - Angela M Cheverton
- Section of Microbiology, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK
| | - Gerald Larrouy-Maumus
- Department of Life Sciences, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK
| | - Stephen A Hare
- Department of Life Sciences, Imperial College London, Exhibition Road, London, SW7 2AZ, UK
- School of Life Sciences, University of Sussex, Brighton, BN1 9QG, UK
| | - Sophie Helaine
- Section of Microbiology, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK.
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18
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Abstract
In nature, bacteria frequently experience many adverse conditions, including heat, oxidation, acidity, and hyperosmolarity, which all tend to slow down if not outright stop cell growth. Previous work on bacterial stress mainly focused on understanding gene regulatory responses. Much less is known about how stresses compromise protein synthesis, which is the major driver of cell growth. Here, we quantitatively characterize the translational capacity of Escherichia coli cells growing exponentially under hyperosmotic stress. We found that hyperosmotic stress affects bacterial protein synthesis through reduction of the translational elongation rate, which is largely compensated for by an increase in the cellular ribosome content compared with nutrient limitation at a similar growth rate. The slowdown of translational elongation is attributed to a reduction in the rate of binding of tRNA ternary complexes to the ribosomes. Hyperosmotic stress is a common stress condition confronted by E. coli during infection of the urinary tract. It can significantly compromise the bacterial growth rate. Protein translation capacity is a critical component of bacterial growth. In this study, we find for the first time that hyperosmotic stress causes substantial slowdown in bacterial ribosome translation elongation. The slowdown of translation elongation originates from a reduced binding rate of tRNA ternary complex to the ribosomes.
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19
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Fan Y, Evans CR, Barber KW, Banerjee K, Weiss KJ, Margolin W, Igoshin OA, Rinehart J, Ling J. Heterogeneity of Stop Codon Readthrough in Single Bacterial Cells and Implications for Population Fitness. Mol Cell 2017; 67:826-836.e5. [PMID: 28781237 PMCID: PMC5591071 DOI: 10.1016/j.molcel.2017.07.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/22/2017] [Accepted: 07/07/2017] [Indexed: 12/30/2022]
Abstract
Gene expression noise (heterogeneity) leads to phenotypic diversity among isogenic individual cells. Our current understanding of gene expression noise is mostly limited to transcription, as separating translational noise from transcriptional noise has been challenging. It also remains unclear how translational heterogeneity originates. Using a transcription-normalized reporter system, we discovered that stop codon readthrough is heterogeneous among single cells, and individual cells with higher UGA readthrough grow faster from stationary phase. Our work also revealed that individual cells with lower protein synthesis levels exhibited higher UGA readthrough, which was confirmed with ribosome-targeting antibiotics (e.g., chloramphenicol). Further experiments and mathematical modeling suggest that varied competition between ternary complexes and release factors perturbs the UGA readthrough level. Our results indicate that fluctuations in the concentrations of translational components lead to UGA readthrough heterogeneity among single cells, which enhances phenotypic diversity of the genetically identical population and facilitates its adaptation to changing environments.
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MESH Headings
- Bacterial Proteins/biosynthesis
- Bacterial Proteins/genetics
- Codon, Terminator
- Escherichia coli/genetics
- Escherichia coli/growth & development
- Escherichia coli/metabolism
- Escherichia coli Proteins/biosynthesis
- Escherichia coli Proteins/genetics
- Gene Expression Regulation, Bacterial
- Genes, Reporter
- Genetic Fitness
- Genotype
- Kinetics
- Luminescent Proteins/biosynthesis
- Luminescent Proteins/genetics
- Microscopy, Fluorescence
- Models, Genetic
- One-Carbon Group Transferases
- Phenotype
- RNA, Bacterial/biosynthesis
- RNA, Bacterial/genetics
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Transcription, Genetic
- Red Fluorescent Protein
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Affiliation(s)
- Yongqiang Fan
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Christopher R Evans
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, Houston, TX 77030, USA
| | - Karl W Barber
- Department of Cellular & Molecular Physiology, Yale University, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Kinshuk Banerjee
- Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, USA
| | - Kalyn J Weiss
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, Houston, TX 77030, USA
| | - William Margolin
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, Houston, TX 77030, USA
| | - Oleg A Igoshin
- Center for Theoretical Biological Physics, Rice University, Houston, TX 77005, USA; Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | - Jesse Rinehart
- Department of Cellular & Molecular Physiology, Yale University, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Jiqiang Ling
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA; Graduate School of Biomedical Sciences, Houston, TX 77030, USA.
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20
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Activation of contact-dependent antibacterial tRNase toxins by translation elongation factors. Proc Natl Acad Sci U S A 2017; 114:E1951-E1957. [PMID: 28223500 DOI: 10.1073/pnas.1619273114] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Contact-dependent growth inhibition (CDI) is a mechanism by which bacteria exchange toxins via direct cell-to-cell contact. CDI systems are distributed widely among Gram-negative pathogens and are thought to mediate interstrain competition. Here, we describe tsf mutations that alter the coiled-coil domain of elongation factor Ts (EF-Ts) and confer resistance to the CdiA-CTEC869 tRNase toxin from enterohemorrhagic Escherichia coli EC869. Although EF-Ts is required for toxicity in vivo, our results indicate that it is dispensable for tRNase activity in vitro. We find that CdiA-CTEC869 binds to elongation factor Tu (EF-Tu) with high affinity and this interaction is critical for nuclease activity. Moreover, in vitro tRNase activity is GTP-dependent, suggesting that CdiA-CTEC869 only cleaves tRNA in the context of translationally active GTP·EF-Tu·tRNA ternary complexes. We propose that EF-Ts promotes the formation of GTP·EF-Tu·tRNA ternary complexes, thereby accelerating substrate turnover for rapid depletion of target-cell tRNA.
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21
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Dai X, Zhu M, Warren M, Balakrishnan R, Patsalo V, Okano H, Williamson JR, Fredrick K, Wang YP, Hwa T. Reduction of translating ribosomes enables Escherichia coli to maintain elongation rates during slow growth. Nat Microbiol 2016; 2:16231. [PMID: 27941827 PMCID: PMC5346290 DOI: 10.1038/nmicrobiol.2016.231] [Citation(s) in RCA: 179] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Accepted: 10/17/2016] [Indexed: 01/13/2023]
Abstract
Bacteria growing under different conditions experience a broad range of demand on the rate of protein synthesis, which profoundly affects cellular resource allocation. During fast growth, protein synthesis has long been known to be modulated by adjusting the ribosome content, with the vast majority of ribosomes engaged at a near-maximal rate of elongation. Here, we systematically characterize protein synthesis by Escherichia coli, focusing on slow-growth conditions. We establish that the translational elongation rate decreases as growth slows, exhibiting a Michaelis-Menten dependence on the abundance of the cellular translational apparatus. However, an appreciable elongation rate is maintained even towards zero growth, including the stationary phase. This maintenance, critical for timely protein synthesis in harsh environments, is accompanied by a drastic reduction in the fraction of active ribosomes. Interestingly, well-known antibiotics such as chloramphenicol also cause a substantial reduction in the pool of active ribosomes, instead of slowing down translational elongation as commonly thought.
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Affiliation(s)
- Xiongfeng Dai
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
| | - Manlu Zhu
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
| | - Mya Warren
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
| | - Rohan Balakrishnan
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
- Department of Microbiology and Ohio State Biochemistry Program, the Ohio State University, Columbus OH 43210
| | - Vadim Patsalo
- Department of Integrative Structural and Computational Biology, Department of Chemistry, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Hiroyuki Okano
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
| | - James R. Williamson
- Department of Integrative Structural and Computational Biology, Department of Chemistry, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Kurt Fredrick
- Department of Microbiology and Ohio State Biochemistry Program, the Ohio State University, Columbus OH 43210
| | - Yi-Ping Wang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
| | - Terence Hwa
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
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22
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Shcherbik N, Chernova TA, Chernoff YO, Pestov DG. Distinct types of translation termination generate substrates for ribosome-associated quality control. Nucleic Acids Res 2016; 44:6840-52. [PMID: 27325745 PMCID: PMC5001609 DOI: 10.1093/nar/gkw566] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Accepted: 06/13/2016] [Indexed: 11/24/2022] Open
Abstract
Cotranslational degradation of polypeptide nascent chains plays a critical role in quality control of protein synthesis and the rescue of stalled ribosomes. In eukaryotes, ribosome stalling triggers release of 60S subunits with attached nascent polypeptides, which undergo ubiquitination by the E3 ligase Ltn1 and proteasomal degradation facilitated by the ATPase Cdc48. However, the identity of factors acting upstream in this process is less clear. Here, we examined how the canonical release factors Sup45–Sup35 (eRF1–eRF3) and their paralogs Dom34-Hbs1 affect the total population of ubiquitinated nascent chains associated with yeast ribosomes. We found that the availability of the functional release factor complex Sup45–Sup35 strongly influences the amount of ubiquitinated polypeptides associated with 60S ribosomal subunits, while Dom34-Hbs1 generate 60S-associated peptidyl-tRNAs that constitute a relatively minor fraction of Ltn1 substrates. These results uncover two separate pathways that target nascent polypeptides for Ltn1-Cdc48-mediated degradation and suggest that in addition to canonical termination on stop codons, eukaryotic release factors contribute to cotranslational protein quality control.
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Affiliation(s)
- Natalia Shcherbik
- Department of Cell Biology, Rowan University, School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Tatiana A Chernova
- Department of Biochemistry, Emory University, School of Medicine, Atlanta, GA 30322, USA
| | - Yury O Chernoff
- School of Biology, Georgia Institute of Technology, Atlanta, GA 30322, USA Laboratory of Amyloid Biology & Institute of Translational Biomedicine, St. Petersburg State University, St. Petersburg 199034, Russia
| | - Dimitri G Pestov
- Department of Cell Biology, Rowan University, School of Osteopathic Medicine, Stratford, NJ 08084, USA
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23
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A Salmonella Toxin Promotes Persister Formation through Acetylation of tRNA. Mol Cell 2016; 63:86-96. [PMID: 27264868 PMCID: PMC4942678 DOI: 10.1016/j.molcel.2016.05.002] [Citation(s) in RCA: 175] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 04/22/2016] [Accepted: 04/29/2016] [Indexed: 11/23/2022]
Abstract
The recalcitrance of many bacterial infections to antibiotic treatment is thought to be due to the presence of persisters that are non-growing, antibiotic-insensitive cells. Eventually, persisters resume growth, accounting for relapses of infection. Salmonella is an important pathogen that causes disease through its ability to survive inside macrophages. After macrophage phagocytosis, a significant proportion of the Salmonella population forms non-growing persisters through the action of toxin-antitoxin modules. Here we reveal that one such toxin, TacT, is an acetyltransferase that blocks the primary amine group of amino acids on charged tRNA molecules, thereby inhibiting translation and promoting persister formation. Furthermore, we report the crystal structure of TacT and note unique structural features, including two positively charged surface patches that are essential for toxicity. Finally, we identify a detoxifying mechanism in Salmonella wherein peptidyl-tRNA hydrolase counteracts TacT-dependent growth arrest, explaining how bacterial persisters can resume growth. TacT promotes Salmonella persister formation by inhibiting translation TacT is an acetyltransferase with positively charged patches essential for toxicity TacT blocks the primary amine group of amino acids on charged tRNA molecules Salmonella detoxifies TacT-corrupted tRNAs, allowing bacterial growth to resume
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24
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Balakrishnan R, Oman K, Shoji S, Bundschuh R, Fredrick K. The conserved GTPase LepA contributes mainly to translation initiation in Escherichia coli. Nucleic Acids Res 2014; 42:13370-83. [PMID: 25378333 PMCID: PMC4245954 DOI: 10.1093/nar/gku1098] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
LepA is a paralog of EF-G found in all bacteria. Deletion of lepA confers no obvious growth defect in Escherichia coli, and the physiological role of LepA remains unknown. Here, we identify nine strains (ΔdksA, ΔmolR1, ΔrsgA, ΔtatB, ΔtonB, ΔtolR, ΔubiF, ΔubiG or ΔubiH) in which ΔlepA confers a synthetic growth phenotype. These strains are compromised for gene regulation, ribosome assembly, transport and/or respiration, indicating that LepA contributes to these functions in some way. We also use ribosome profiling to deduce the effects of LepA on translation. We find that loss of LepA alters the average ribosome density (ARD) for hundreds of mRNA coding regions in the cell, substantially reducing ARD in many cases. By contrast, only subtle and codon-specific changes in ribosome distribution along mRNA are seen. These data suggest that LepA contributes mainly to the initiation phase of translation. Consistent with this interpretation, the effect of LepA on ARD is related to the sequence of the Shine–Dalgarno region. Global perturbation of gene expression in the ΔlepA mutant likely explains most of its phenotypes.
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Affiliation(s)
- Rohan Balakrishnan
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Kenji Oman
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA Department of Physics, The Ohio State University, Columbus, OH 43210, USA
| | - Shinichiro Shoji
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Ralf Bundschuh
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA Department of Physics, The Ohio State University, Columbus, OH 43210, USA
| | - Kurt Fredrick
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
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25
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Structure and mechanism of the tRNA-dependent lantibiotic dehydratase NisB. Nature 2014; 517:509-12. [PMID: 25363770 DOI: 10.1038/nature13888] [Citation(s) in RCA: 234] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 09/23/2014] [Indexed: 01/15/2023]
Abstract
Lantibiotics are a class of peptide antibiotics that contain one or more thioether bonds. The lantibiotic nisin is an antimicrobial peptide that is widely used as a food preservative to combat food-borne pathogens. Nisin contains dehydroalanine and dehydrobutyrine residues that are formed by the dehydration of Ser/Thr by the lantibiotic dehydratase NisB (ref. 2). Recent biochemical studies revealed that NisB glutamylates Ser/Thr side chains as part of the dehydration process. However, the molecular mechanism by which NisB uses glutamate to catalyse dehydration remains unresolved. Here we show that this process involves glutamyl-tRNA(Glu) to activate Ser/Thr residues. In addition, the 2.9-Å crystal structure of NisB in complex with its substrate peptide NisA reveals the presence of two separate domains that catalyse the Ser/Thr glutamylation and glutamate elimination steps. The co-crystal structure also provides insights into substrate recognition by lantibiotic dehydratases. Our findings demonstrate an unexpected role for aminoacyl-tRNA in the formation of dehydroamino acids in lantibiotics, and serve as a basis for the functional characterization of the many lantibiotic-like dehydratases involved in the biosynthesis of other classes of natural products.
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26
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Machida K, Mikami S, Masutani M, Mishima K, Kobayashi T, Imataka H. A translation system reconstituted with human factors proves that processing of encephalomyocarditis virus proteins 2A and 2B occurs in the elongation phase of translation without eukaryotic release factors. J Biol Chem 2014; 289:31960-31971. [PMID: 25258322 PMCID: PMC4231674 DOI: 10.1074/jbc.m114.593343] [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] [Indexed: 02/05/2023] Open
Abstract
The genomic RNA of encephalomyocarditis virus (EMCV) encodes a single polyprotein, and the primary scission of the polyprotein occurs between nonstructural proteins 2A and 2B by an unknown mechanism. To gain insight into the mechanism of 2A-2B processing, we first translated the 2A-2B region in vitro with eukaryotic and prokaryotic translation systems. The 2A-2B processing occurred only in the eukaryotic systems, not in the prokaryotic systems, and the unprocessed 2A-2B protein synthesized by a prokaryotic system remained uncleaved when incubated with a eukaryotic cell extract. These results suggest that 2A-2B processing is a eukaryote-specific, co-translational event. To define the translation factors required for 2A-2B processing, we constituted a protein synthesis system with eukaryotic elongation factors 1 and 2, eukaryotic release factors 1 and 3 (eRF1 and eRF3), aminoacyl-tRNA synthetases, tRNAs, ribosome subunits, and a plasmid template that included the hepatitis C virus internal ribosome entry site. We successfully reproduced 2A-2B processing in the reconstituted system even without eRFs. Our results indicate that this unusual event occurs in the elongation phase of translation.
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Affiliation(s)
- Kodai Machida
- Department of Materials Science and Chemistry and University of Hyogo, Himeji 671-2201, Japan; Molecular Nanotechnology Research Center, Graduate School of Engineering, University of Hyogo, Himeji 671-2201, Japan and
| | - Satoshi Mikami
- RIKEN Systems and Structural Biology Center, Yokohama 230-0045, Japan
| | - Mamiko Masutani
- Department of Materials Science and Chemistry and University of Hyogo, Himeji 671-2201, Japan
| | - Kurumi Mishima
- Department of Materials Science and Chemistry and University of Hyogo, Himeji 671-2201, Japan
| | - Tominari Kobayashi
- Department of Materials Science and Chemistry and University of Hyogo, Himeji 671-2201, Japan
| | - Hiroaki Imataka
- Department of Materials Science and Chemistry and University of Hyogo, Himeji 671-2201, Japan; Molecular Nanotechnology Research Center, Graduate School of Engineering, University of Hyogo, Himeji 671-2201, Japan and.
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27
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Janssen BD, Garza-Sánchez F, Hayes CS. A-site mRNA cleavage is not required for tmRNA-mediated ssrA-peptide tagging. PLoS One 2013; 8:e81319. [PMID: 24260569 PMCID: PMC3834316 DOI: 10.1371/journal.pone.0081319] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 10/21/2013] [Indexed: 11/18/2022] Open
Abstract
In Escherichia coli, prolonged translational arrest allows mRNA degradation into the A site of stalled ribosomes. The enzyme that cleaves the A-site codon is not known, but its activity requires RNase II to degrade mRNA downstream of the ribosome. This A-site mRNA cleavage process is thought to function in translation quality control because stalled ribosomes are recycled from A-site truncated transcripts by the tmRNA-SmpB "ribosome rescue" system. During rescue, the tmRNA-encoded ssrA peptide is added to the nascent chain, thereby targeting the tagged protein for degradation after release from the ribosome. Here, we examine the influence of A-site mRNA cleavage upon tmRNA-SmpB activity. Using a model transcript that undergoes stop-codon cleavage in response to inefficient translation termination, we quantify ssrA-peptide tagging of the encoded protein in cells that contain (rnb(+)) or lack (Δrnb) RNase II. A-site mRNA cleavage is reduced approximately three-fold in Δrnb backgrounds, but the efficiency of ssrA-tagging is identical to that of rnb(+) cells. Additionally, pulse-chase analysis demonstrates that paused ribosomes recycle from the test transcripts at similar rates in rnb(+) and Δrnb cells. Together, these results indicate that A-site truncated transcripts are not required for tmRNA-SmpB-mediated ribosome rescue and suggest that A-site mRNA cleavage process may play a role in other recycling 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, United States of America
| | - Fernando Garza-Sánchez
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Christopher S. Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, California, United States of America
- * E-mail:
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