1
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Lin XN, Gai BX, Liu L, Cheng L. Advances in the investigation of N 6-isopentenyl adenosine i 6A RNA modification. Bioorg Med Chem 2024; 110:117838. [PMID: 39018794 DOI: 10.1016/j.bmc.2024.117838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2024] [Revised: 07/09/2024] [Accepted: 07/09/2024] [Indexed: 07/19/2024]
Abstract
Prenylation (isopentenylation), a key post-transcriptional modification with a hydrophobic prenyl group onto the biomacromolecules such as RNA and proteins, influences their localization and function. Prenyltransferases mediate this process, while cytokinin oxidases degrade the prenylated adenosine in plants. This review summarizes current progress in detecting prenylation modifications in RNA across species and their effects on protein synthesis. Advanced methods have been developed to label and study these modifications in vitro and in vivo, despite challenges posed by the inert chemical properties of prenyl groups. Continued advancements in bioorthogonal chemistry promise new tools for understanding the precise biological functions of prenylated RNA modifications and other related proteins.
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Affiliation(s)
- Xiu-Na Lin
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bo-Xu Gai
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Li Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liang Cheng
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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2
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Sun J, Wu J, Yuan Y, Fan L, Chua WLP, Ling YHS, Balamkundu S, priya D, Suen HCS, de Crécy-Lagard V, Dziergowska A, Dedon PC. tRNA modification profiling reveals epitranscriptome regulatory networks in Pseudomonas aeruginosa. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.01.601603. [PMID: 39005467 PMCID: PMC11245014 DOI: 10.1101/2024.07.01.601603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Transfer RNA (tRNA) modifications have emerged as critical posttranscriptional regulators of gene expression affecting diverse biological and disease processes. While there is extensive knowledge about the enzymes installing the dozens of post-transcriptional tRNA modifications - the tRNA epitranscriptome - very little is known about how metabolic, signaling, and other networks integrate to regulate tRNA modification levels. Here we took a comprehensive first step at understanding epitranscriptome regulatory networks by developing a high-throughput tRNA isolation and mass spectrometry-based modification profiling platform and applying it to a Pseudomonas aeruginosa transposon insertion mutant library comprising 5,746 strains. Analysis of >200,000 tRNA modification data points validated the annotations of predicted tRNA modification genes, uncovered novel tRNA-modifying enzymes, and revealed tRNA modification regulatory networks in P. aeruginosa. Platform adaptation for RNA-seq library preparation would complement epitranscriptome studies, while application to human cell and mouse tissue demonstrates its utility for biomarker and drug discovery and development.
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Affiliation(s)
- Jingjing Sun
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Antimicrobial Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, 138602 Singapore
| | - Junzhou Wu
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Antimicrobial Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, 138602 Singapore
| | - Yifeng Yuan
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611 USA
| | - Leon Fan
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Wei Lin Patrina Chua
- Antimicrobial Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, 138602 Singapore
| | - Yan Han Sharon Ling
- Antimicrobial Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, 138602 Singapore
| | | | - Dwija priya
- Antimicrobial Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, 138602 Singapore
| | - Hazel Chay Suen Suen
- Department of Food, Chemical & Biotechnology, Singapore of Institute of Technology, 138683 Singapore
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611 USA
- Genetic Institute, University of Florida, Gainesville, FL 32611 USA
| | | | - Peter C. Dedon
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
- Antimicrobial Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, 138602 Singapore
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3
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Throll P, G Dolce L, Rico-Lastres P, Arnold K, Tengo L, Basu S, Kaiser S, Schneider R, Kowalinski E. Structural basis of tRNA recognition by the m 3C RNA methyltransferase METTL6 in complex with SerRS seryl-tRNA synthetase. Nat Struct Mol Biol 2024:10.1038/s41594-024-01341-3. [PMID: 38918637 DOI: 10.1038/s41594-024-01341-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 05/29/2024] [Indexed: 06/27/2024]
Abstract
Methylation of cytosine 32 in the anticodon loop of tRNAs to 3-methylcytosine (m3C) is crucial for cellular translation fidelity. Misregulation of the RNA methyltransferases setting this modification can cause aggressive cancers and metabolic disturbances. Here, we report the cryo-electron microscopy structure of the human m3C tRNA methyltransferase METTL6 in complex with seryl-tRNA synthetase (SerRS) and their common substrate tRNASer. Through the complex structure, we identify the tRNA-binding domain of METTL6. We show that SerRS acts as the tRNASer substrate selection factor for METTL6. We demonstrate that SerRS augments the methylation activity of METTL6 and that direct contacts between METTL6 and SerRS are necessary for efficient tRNASer methylation. Finally, on the basis of the structure of METTL6 in complex with SerRS and tRNASer, we postulate a universal tRNA-binding mode for m3C RNA methyltransferases, including METTL2 and METTL8, suggesting that these mammalian paralogs use similar ways to engage their respective tRNA substrates and cofactors.
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Affiliation(s)
| | | | - Palma Rico-Lastres
- Institute of Functional Epigenetics, Helmholtz Zentrum Munich, Neuherberg, Germany
| | - Katharina Arnold
- Institute of Functional Epigenetics, Helmholtz Zentrum Munich, Neuherberg, Germany
| | - Laura Tengo
- European Molecular Biology Laboratory, Grenoble, France
| | - Shibom Basu
- European Molecular Biology Laboratory, Grenoble, France
| | - Stefanie Kaiser
- Institute of Pharmaceutical Chemistry, Goethe University Frankfurt, Frankfurt, Germany
| | - Robert Schneider
- Institute of Functional Epigenetics, Helmholtz Zentrum Munich, Neuherberg, Germany
| | - Eva Kowalinski
- European Molecular Biology Laboratory, Grenoble, France.
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4
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Li Y, Zhou H, Chen S, Li Y, Guo Y, Chen X, Wang S, Wang L, Gan Y, Zhang S, Zheng Y, Sheng J, Zhou Z, Wang R. Bioorthogonal labeling and profiling of N6-isopentenyladenosine (i6A) modified RNA. Nucleic Acids Res 2024; 52:2808-2820. [PMID: 38426933 PMCID: PMC11014277 DOI: 10.1093/nar/gkae150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 02/06/2024] [Accepted: 02/16/2024] [Indexed: 03/02/2024] Open
Abstract
Chemical modifications in RNAs play crucial roles in diversifying their structures and regulating numerous biochemical processes. Since the 1990s, several hydrophobic prenyl-modifications have been discovered in various RNAs. Prenyl groups serve as precursors for terpenes and many other biological molecules. The processes of prenylation in different macromolecules have been extensively studied. We introduce here a novel chemical biology toolkit that not only labels i6A, a prenyl-modified RNA residue, by leveraging the unique reactivity of the prenyl group, but also provides a general strategy to incorporate fluorescence functionalities into RNAs for molecular tracking purposes. Our findings revealed that iodine-mediated cyclization reactions of the prenyl group occur rapidly, transforming i6A from a hydrogen-bond acceptor to a donor. Based on this reactivity, we developed an Iodine-Mediated Cyclization and Reverse Transcription (IMCRT) tRNA-seq method, which can profile all nine endogenous tRNAs containing i6A residues in Saccharomyces cerevisiae with single-base resolution. Furthermore, under stress conditions, we observed a decline in i6A levels in budding yeast, accompanied by significant decrease of mutation rate at A37 position. Thus, the IMCRT tRNA-seq method not only permits semi-quantification of i6A levels in tRNAs but also holds potential for transcriptome-wide detection and analysis of various RNA species containing i6A modifications.
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Affiliation(s)
- Yuanyuan Li
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Hongling Zhou
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Shasha Chen
- National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Yinan Li
- National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Yuyang Guo
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Xiaoqian Chen
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Sheng Wang
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Li Wang
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Youfang Gan
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Shusheng Zhang
- Innovation Research Institute of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
| | - Ya Ying Zheng
- Department of Chemistry and The RNA Institute, University at Albany, State University of New York, Albany, NY 12222, USA
| | - Jia Sheng
- Department of Chemistry and The RNA Institute, University at Albany, State University of New York, Albany, NY 12222, USA
| | - Zhipeng Zhou
- National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Rui Wang
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
- Shenzhen Huazhong University of Science and Technology Research Institute, Shenzhen, Guangdong 518057, China
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5
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Abstract
The study of eukaryotic tRNA processing has given rise to an explosion of new information and insights in the last several years. We now have unprecedented knowledge of each step in the tRNA processing pathway, revealing unexpected twists in biochemical pathways, multiple new connections with regulatory pathways, and numerous biological effects of defects in processing steps that have profound consequences throughout eukaryotes, leading to growth phenotypes in the yeast Saccharomyces cerevisiae and to neurological and other disorders in humans. This review highlights seminal new results within the pathways that comprise the life of a tRNA, from its birth after transcription until its death by decay. We focus on new findings and revelations in each step of the pathway including the end-processing and splicing steps, many of the numerous modifications throughout the main body and anticodon loop of tRNA that are so crucial for tRNA function, the intricate tRNA trafficking pathways, and the quality control decay pathways, as well as the biogenesis and biology of tRNA-derived fragments. We also describe the many interactions of these pathways with signaling and other pathways in the cell.
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Affiliation(s)
- Eric M Phizicky
- Department of Biochemistry and Biophysics and Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York 14642, USA
| | - Anita K Hopper
- Department of Molecular Genetics and Center for RNA Biology, Ohio State University, Columbus, Ohio 43235, USA
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6
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Modopathies Caused by Mutations in Genes Encoding for Mitochondrial RNA Modifying Enzymes: Molecular Mechanisms and Yeast Disease Models. Int J Mol Sci 2023; 24:ijms24032178. [PMID: 36768505 PMCID: PMC9917222 DOI: 10.3390/ijms24032178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/17/2023] [Accepted: 01/20/2023] [Indexed: 01/25/2023] Open
Abstract
In eukaryotes, mitochondrial RNAs (mt-tRNAs and mt-rRNAs) are subject to specific nucleotide modifications, which are critical for distinct functions linked to the synthesis of mitochondrial proteins encoded by mitochondrial genes, and thus for oxidative phosphorylation. In recent years, mutations in genes encoding for mt-RNAs modifying enzymes have been identified as being causative of primary mitochondrial diseases, which have been called modopathies. These latter pathologies can be caused by mutations in genes involved in the modification either of tRNAs or of rRNAs, resulting in the absence of/decrease in a specific nucleotide modification and thus on the impairment of the efficiency or the accuracy of the mitochondrial protein synthesis. Most of these mutations are sporadic or private, thus it is fundamental that their pathogenicity is confirmed through the use of a model system. This review will focus on the activity of genes that, when mutated, are associated with modopathies, on the molecular mechanisms through which the enzymes introduce the nucleotide modifications, on the pathological phenotypes associated with mutations in these genes and on the contribution of the yeast Saccharomyces cerevisiae to confirming the pathogenicity of novel mutations and, in some cases, for defining the molecular defects.
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7
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Yakita M, Chujo T, Wei FY, Hirayama M, Kato K, Takahashi N, Naganuma K, Nagata M, Kawahara K, Nakayama H, Tomizawa K. Extracellular N6 -isopentenyladenosine (i 6A) addition induces cotranscriptional i 6A incorporation into ribosomal RNAs. RNA (NEW YORK, N.Y.) 2022; 28:1013-1027. [PMID: 35414588 PMCID: PMC9202588 DOI: 10.1261/rna.079176.122] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 04/07/2022] [Indexed: 06/14/2023]
Abstract
N6 -isopentenyladenosine (i6A), a modified adenosine monomer, is known to induce cell death upon its addition to the culture medium. However, the molecular fate of extracellularly added i6A has yet to be identified. Here we show that i6A addition to cell culture medium results in i6A incorporation into cellular RNA in several cell lines, including the 5-fluorouracil (5-FU)-resistant human oral squamous cell carcinoma cell line FR2-SAS and its parental 5-FU-sensitive cell line SAS. i6A was predominantly incorporated into 18S and 28S rRNAs, and i6A incorporation into total RNA was mostly suppressed by treating these cell lines with an RNA polymerase I (Pol I) inhibitor. i6A was incorporated into RNA even upon inactivation of TRIT1, the only cellular i6A-modifying enzyme. These results indicate that upon cellular uptake of i6A, it is anabolized to be used for Pol I transcription. Interestingly, at lower i6A concentrations, the cytotoxic effect of i6A was substantially more pronounced in FR2-SAS cells than in SAS cells. Moreover, in FR2-SAS cells, i6A treatment decreased the rate of cellular protein synthesis and increased intracellular protein aggregation, and these effects were more pronounced than in SAS cells. Our work provides insights into the molecular fate of extracellularly applied i6A in the context of intracellular nucleic acid anabolism and suggests investigation of i6A as a candidate for a chemotherapy agent against 5-FU-resistant cancer cells.
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Affiliation(s)
- Maya Yakita
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
- Department of Oral and Maxillofacial Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Takeshi Chujo
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Fan-Yan 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
| | - Mayumi Hirayama
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
- Department of Oral and Maxillofacial Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Koji Kato
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Nozomu Takahashi
- Department of Oral and Maxillofacial Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Kenta Naganuma
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Masashi Nagata
- Department of Oral and Maxillofacial Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Kenta Kawahara
- Department of Oral and Maxillofacial Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Hideki Nakayama
- Department of Oral and Maxillofacial Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
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8
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Lentini JM, Bargabos R, Chen C, Fu D. Methyltransferase METTL8 is required for 3-methylcytosine modification in human mitochondrial tRNAs. J Biol Chem 2022; 298:101788. [PMID: 35247384 PMCID: PMC8980813 DOI: 10.1016/j.jbc.2022.101788] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 02/21/2022] [Accepted: 02/22/2022] [Indexed: 02/03/2023] Open
Abstract
A subset of eukaryotic tRNAs is methylated in the anticodon loop, forming 3-methylcytosine (m3C) modifications. In mammals, the number of tRNAs containing m3C modifications has been expanded to include mitochondrial (mt) tRNA-Ser-UGA and mt-tRNA-Thr-UGU. However, whereas the enzymes catalyzing m3C formation in nuclear-encoded tRNAs have been identified, the proteins responsible for m3C modification in mt-tRNAs are unknown. Here, we show that m3C formation in human mt-tRNAs is dependent upon the Methyltransferase-Like 8 (METTL8) enzyme. We find that METTL8 is a mitochondria-associated protein that interacts with mitochondrial seryl-tRNA synthetase, as well as with mt-tRNAs containing m3C. We demonstrate that human cells deficient in METTL8 exhibit loss of m3C modification in mt-tRNAs, but not nuclear-encoded tRNAs. Consistent with the mitochondrial import of METTL8, the formation of m3C in METTL8-deficient cells could be rescued by re-expression of wildtype METTL8, but not by a METTL8 variant lacking the N-terminal mitochondrial localization signal. Notably, we found METTL8-deficiency in human cells causes alterations in the native migration pattern of mt-tRNA-Ser-UGA, suggesting a role for m3C in tRNA folding. Altogether, these findings demonstrate that METTL8 is required for m3C formation in mitochondrial tRNAs and uncover a potential function for m3C modification in mitochondrial tRNA structure.
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Affiliation(s)
- Jenna M Lentini
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, New York, United States of America
| | - Rachel Bargabos
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, New York, United States of America
| | - Chen Chen
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, New York, United States of America
| | - Dragony Fu
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, New York, United States of America.
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9
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Khalique A, Mattijssen S, Maraia RJ. A versatile tRNA modification-sensitive northern blot method with enhanced performance. RNA (NEW YORK, N.Y.) 2022; 28:418-432. [PMID: 34930808 PMCID: PMC8848930 DOI: 10.1261/rna.078929.121] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 12/01/2021] [Indexed: 06/14/2023]
Abstract
The 22 mitochondrial and ∼45 cytosolic tRNAs in human cells contain several dozen different post-transcriptional modified nucleotides such that each carries a unique constellation that complements its function. Many tRNA modifications are linked to altered gene expression, and deficiencies due to mutations in tRNA modification enzymes (TMEs) are responsible for numerous diseases. Easily accessible methods to detect tRNA hypomodifications can facilitate progress in advancing such molecular studies. Our laboratory developed a northern blot method that can quantify relative levels of base modifications on multiple specific tRNAs ∼10 yr ago, which has been used to characterize four different TME deficiencies and is likely further extendable. The assay method depends on differential annealing efficiency of a DNA-oligo probe to the modified versus unmodified tRNA. The signal of this probe is then normalized by a second probe elsewhere on the same tRNA. This positive hybridization in the absence of modification (PHAM) assay has proven useful for i6A37, t6A37, m3C32, and m2,2G26 in multiple laboratories. Yet, over the years we have observed idiosyncratic inconsistency and variability in the assay. Here we document these for some tRNAs and probes and illustrate principles and practices for improved reliability and uniformity in performance. We provide an overview of the method and illustrate benefits of the improved conditions. This is followed by data that demonstrate quantitative validation of PHAM using a TME deletion control, and that nearby modifications can falsely alter the calculated apparent modification efficiency. Finally, we include a calculator tool for matching probe and hybridization conditions.
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Affiliation(s)
- Abdul Khalique
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Sandy Mattijssen
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Richard J Maraia
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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10
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Chujo T, Tomizawa K. Human transfer RNA modopathies: diseases caused by aberrations in transfer RNA modifications. FEBS J 2021; 288:7096-7122. [PMID: 33513290 PMCID: PMC9255597 DOI: 10.1111/febs.15736] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 12/13/2020] [Accepted: 01/27/2021] [Indexed: 12/14/2022]
Abstract
tRNA molecules are post-transcriptionally modified by tRNA modification enzymes. Although composed of different chemistries, more than 40 types of human tRNA modifications play pivotal roles in protein synthesis by regulating tRNA structure and stability as well as decoding genetic information on mRNA. Many tRNA modifications are conserved among all three kingdoms of life, and aberrations in various human tRNA modification enzymes cause life-threatening diseases. Here, we describe the class of diseases and disorders caused by aberrations in tRNA modifications as 'tRNA modopathies'. Aberrations in over 50 tRNA modification enzymes are associated with tRNA modopathies, which most frequently manifest as dysfunctions of the brain and/or kidney, mitochondrial diseases, and cancer. However, the molecular mechanisms that link aberrant tRNA modifications to human diseases are largely unknown. In this review, we provide a comprehensive compilation of human tRNA modification functions, tRNA modification enzyme genes, and tRNA modopathies, and we summarize the elucidated pathogenic mechanisms underlying several tRNA modopathies. We will also discuss important questions that need to be addressed in order to understand the molecular pathogenesis of tRNA modopathies.
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Affiliation(s)
- Takeshi Chujo
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Japan
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Japan
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11
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A substrate binding model for the KEOPS tRNA modifying complex. Nat Commun 2020; 11:6233. [PMID: 33277478 PMCID: PMC7718258 DOI: 10.1038/s41467-020-19990-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 11/02/2020] [Indexed: 11/09/2022] Open
Abstract
The KEOPS complex, which is conserved across archaea and eukaryotes, is composed of four core subunits; Pcc1, Kae1, Bud32 and Cgi121. KEOPS is crucial for the fitness of all organisms examined. In humans, pathogenic mutations in KEOPS genes lead to Galloway-Mowat syndrome, an autosomal-recessive disease causing childhood lethality. Kae1 catalyzes the universal and essential tRNA modification N6-threonylcarbamoyl adenosine, but the precise roles of all other KEOPS subunits remain an enigma. Here we show using structure-guided studies that Cgi121 recruits tRNA to KEOPS by binding to its 3' CCA tail. A composite model of KEOPS bound to tRNA reveals that all KEOPS subunits form an extended tRNA-binding surface that we have validated in vitro and in vivo to mediate the interaction with the tRNA substrate and its modification. These findings provide a framework for understanding the inner workings of KEOPS and delineate why all KEOPS subunits are essential.
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12
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Lentini JM, Alsaif HS, Faqeih E, Alkuraya FS, Fu D. DALRD3 encodes a protein mutated in epileptic encephalopathy that targets arginine tRNAs for 3-methylcytosine modification. Nat Commun 2020; 11:2510. [PMID: 32427860 PMCID: PMC7237682 DOI: 10.1038/s41467-020-16321-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 04/24/2020] [Indexed: 12/24/2022] Open
Abstract
In mammals, a subset of arginine tRNA isoacceptors are methylated in the anticodon loop by the METTL2 methyltransferase to form the 3-methylcytosine (m3C) modification. However, the mechanism by which METTL2 identifies specific tRNA arginine species for m3C formation as well as the biological role of m3C in mammals is unknown. Here, we show that human METTL2 forms a complex with DALR anticodon binding domain containing 3 (DALRD3) protein to recognize particular arginine tRNAs destined for m3C modification. DALRD3-deficient human cells exhibit nearly complete loss of the m3C modification in tRNA-Arg species. Notably, we identify a homozygous nonsense mutation in the DALRD3 gene that impairs m3C formation in human patients exhibiting developmental delay and early-onset epileptic encephalopathy. These findings uncover an unexpected function for the DALRD3 protein in the targeting of distinct arginine tRNAs for m3C modification and suggest a crucial biological role for DALRD3-dependent tRNA modification in proper neurological development.
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Affiliation(s)
- Jenna M Lentini
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, NY, USA
| | - Hessa S Alsaif
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Eissa Faqeih
- Section of Medical Genetics, Children's Specialist Hospital, King Fahad Medical City, Riyadh, Saudi Arabia
| | - Fowzan S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
- Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
| | - Dragony Fu
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, NY, USA.
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13
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Dabravolski S. Multi-faceted nature of the tRNA isopentenyltransferase. FUNCTIONAL PLANT BIOLOGY : FPB 2020; 47:475-485. [PMID: 32345433 DOI: 10.1071/fp19255] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 12/26/2019] [Indexed: 06/11/2023]
Abstract
Transfer RNA isopentenylation an adenine 37 position (A37) is a universal modification known in prokaryotes and eukaryotes. A set of highly homologous enzymes catalyse a series of reactions, leading to tRNA modifications, aimed to increase adaptation to environmental condition through the control of translation efficiency and reading frame maintenance. Transfer RNA-isopentenylation-related (TI-related) functions are well studied in bacteria, mitochondria of yeast and human, but completely unexplored in plants. Transfer RNA-isopentenylation-unrelated (TI-unrelated) functions participate in adaptation to environmental stresses via the regulation of sterol metabolism, gene silencing/suppression and amyloid fibrils formation. TI-unrelated functions are mostly studied in yeast. Finally, the degradation of A37-modified tRNA releases a set of bioactive compounds known as cis-cytokinins. Although all organisms are able to produce cis-cytokinins, its physiological role is still a matter of debates. For several species of bacteria and fungi, cis-cytokinins are known to play a crucial role in pathogenesis. In mammalian and human models cis-cytokinins have tumour-suppressing and anti-inflammation effects. This review aims to summarise current knowledge of the TI-related and TI-unrelated functions and main bioactive by-products of isopentenylated tRNA degradation.
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Affiliation(s)
- Siarhei Dabravolski
- Department of Molecular Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelu 27, 78371 Olomouc, Czech Republic.
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14
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Janin M, Coll-SanMartin L, Esteller M. Disruption of the RNA modifications that target the ribosome translation machinery in human cancer. Mol Cancer 2020; 19:70. [PMID: 32241281 PMCID: PMC7114786 DOI: 10.1186/s12943-020-01192-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 03/24/2020] [Indexed: 12/20/2022] Open
Abstract
Genetic and epigenetic changes deregulate RNA and protein expression in cancer cells. In this regard, tumors exhibit an abnormal proteome in comparison to the corresponding normal tissues. Translation control is a crucial step in the regulation of gene expression regulation under normal and pathological conditions that ultimately determines cellular fate. In this context, evidence shows that transfer and ribosomal RNA (tRNA and rRNA) modifications affect the efficacy and fidelity of translation. The number of RNA modifications increases with the complexity of organisms, suggesting an evolutionary diversification of the possibilities for fine-tuning the functions of coding and non-coding RNAs. In this review, we focus on alterations of modifications of transfer and ribosomal RNA that affect translation in human cancer. This variation in the RNA modification status can be the result of altered modifier expression (writers, readers or erasers), but also due to components of the machineries (C/D or H/ACA boxes) or alterations of proteins involved in modifier expression. Broadening our understanding of the mechanisms by which site-specific modifications modulate ribosome activity in the context of tumorigenesis will enable us to enrich our knowledge about how ribosomes can influence cell fate and form the basis of new therapeutic opportunities.
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Affiliation(s)
- Maxime Janin
- Josep Carreras Leukaemia Research Institute (IJC), Badalona, Barcelona, Catalonia, Spain
| | - Laia Coll-SanMartin
- Josep Carreras Leukaemia Research Institute (IJC), Badalona, Barcelona, Catalonia, Spain
| | - Manel Esteller
- Josep Carreras Leukaemia Research Institute (IJC), Badalona, Barcelona, Catalonia, Spain.
- Centro de Investigacion Biomedica en Red Cancer (CIBERONC), Madrid, Spain.
- Physiological Sciences Department, School of Medicine and Health Sciences, University of Barcelona (UB), Barcelona, Catalonia, Spain.
- Institucio Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Catalonia, Spain.
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15
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Khalique A, Mattijssen S, Haddad AF, Chaudhry S, Maraia RJ. Targeting mitochondrial and cytosolic substrates of TRIT1 isopentenyltransferase: Specificity determinants and tRNA-i6A37 profiles. PLoS Genet 2020; 16:e1008330. [PMID: 32324744 PMCID: PMC7200024 DOI: 10.1371/journal.pgen.1008330] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 05/05/2020] [Accepted: 03/18/2020] [Indexed: 11/29/2022] Open
Abstract
The tRNA isopentenyltransferases (IPTases), which add an isopentenyl group to N6 of A37 (i6A37) of certain tRNAs, are among a minority of enzymes that modify cytosolic and mitochondrial tRNAs. Pathogenic mutations to the human IPTase, TRIT1, that decrease i6A37 levels, cause mitochondrial insufficiency that leads to neurodevelopmental disease. We show that TRIT1 encodes an amino-terminal mitochondrial targeting sequence (MTS) that directs mitochondrial import and modification of mitochondrial-tRNAs. Full understanding of IPTase function must consider the tRNAs selected for modification, which vary among species, and in their cytosol and mitochondria. Selection is principally via recognition of the tRNA A36-A37-A38 sequence. An exception is unmodified tRNATrpCCA-A37-A38 in Saccharomyces cerevisiae, whereas tRNATrpCCA is readily modified in Schizosaccharomyces pombe, indicating variable IPTase recognition systems and suggesting that additional exceptions may account for some of the tRNA-i6A37 paucity in higher eukaryotes. Yet TRIT1 had not been characterized for restrictive type substrate-specific recognition. We used i6A37-dependent tRNA-mediated suppression and i6A37-sensitive northern blotting to examine IPTase activities in S. pombe and S. cerevisiae lacking endogenous IPTases on a diversity of tRNA-A36-A37-A38 substrates. Point mutations to the TRIT1 MTS that decrease human mitochondrial import, decrease modification of mitochondrial but not cytosolic tRNAs in both yeasts. TRIT1 exhibits clear substrate-specific restriction against a cytosolic-tRNATrpCCA-A37-A38. Additional data suggest that position 32 of tRNATrpCCA is a conditional determinant for substrate-specific i6A37 modification by the restrictive IPTases, Mod5 and TRIT1. The cumulative biochemical and phylogenetic sequence analyses provide new insights into IPTase activities and determinants of tRNA-i6A37 profiles in cytosol and mitochondria.
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Affiliation(s)
- Abdul Khalique
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sandy Mattijssen
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
| | - Alexander F. Haddad
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
| | - Shereen Chaudhry
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
| | - Richard J. Maraia
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
- Commissioned Corps, United States Public Health Service, Rockville, Maryland, United States of America
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16
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Aoki MM, Seegobin M, Kisiala A, Noble A, Brunetti C, Emery RJN. Phytohormone metabolism in human cells: Cytokinins are taken up and interconverted in HeLa cell culture. FASEB Bioadv 2019; 1:320-331. [PMID: 32123835 PMCID: PMC6996375 DOI: 10.1096/fba.2018-00032] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 02/06/2019] [Accepted: 02/07/2019] [Indexed: 01/30/2023] Open
Abstract
Cytokinins (CKs) encompass a group of phytohormones, known to orchestrate many critical processes in plant development. Excluding Archaea, CKs are pervasive among all kingdoms, but much less is reported about their metabolism beyond plants. Recent evidence from mammalian tissues indicates the presence of six additional CK forms beyond the previously identified, single mammalian CK, N6-isopentenyladenosine (i6A). There is limited understanding of CK biosynthesis pathways in mammalian systems; therefore, human cervical cancer (HeLa) cells were used to further characterize CK processing by tracking the interconversion of CKs into their various structural derivatives in mammalian cells in a time-course study. Through high-performance liquid chromatography-positive electrospray ionization-tandem mass spectrometry (HPLC-(+ESI)-MS/MS), we document changes in the functional profiles of endogenous CKs in a human cell line following metabolism by HeLa cell cultures. The nucleotide CK fraction (iPRP) was found exclusively within the cell pellet (0.34 pmol/106 cells), and the active free base (FB) form (iP) and riboside fraction (iPR) were found in greater abundance extracellularly (1.67 and 0.10 nmol/L respectively). For further confirmation, we demonstrate that HeLa cells metabolize an exogenously supplied CK, N6-benzyladenosine (BAR). In the HeLa culture supernatant, a 12-fold decrease in BAR concentration was observed within the first 24 hours of incubation accompanied by a fivefold increase in the FB form, N6-benzyladenine (BA). These findings support the hypothesis that HeLa cells have the enzymatic pathways required for the metabolism of both endogenous and exogenous CKs.
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Affiliation(s)
- Megan M. Aoki
- Department of BiologyTrent UniversityPeterboroughOntarioCanada
| | - Mark Seegobin
- Department of BiologyTrent UniversityPeterboroughOntarioCanada
| | - Anna Kisiala
- Department of BiologyTrent UniversityPeterboroughOntarioCanada
| | | | - Craig Brunetti
- Department of BiologyTrent UniversityPeterboroughOntarioCanada
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17
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Hoffmann A, Fallmann J, Vilardo E, Mörl M, Stadler PF, Amman F. Accurate mapping of tRNA reads. Bioinformatics 2019; 34:1116-1124. [PMID: 29228294 DOI: 10.1093/bioinformatics/btx756] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 12/07/2017] [Indexed: 11/12/2022] Open
Abstract
Motivation Many repetitive DNA elements are transcribed at appreciable expression levels. Mapping the corresponding RNA sequencing reads back to a reference genome is notoriously difficult and error-prone task, however. This is in particular true if chemical modifications introduce systematic mismatches, while at the same time the genomic loci are only approximately identical, as in the case of tRNAs. Results We therefore developed a dedicated mapping strategy to handle RNA-seq reads that map to tRNAs relying on a modified target genome in which known tRNA loci are masked and instead intronless tRNA precursor sequences are appended as artificial 'chromosomes'. In a first pass, reads that overlap the boundaries of mature tRNAs are extracted. In the second pass, the remaining reads are mapped to a tRNA-masked target that is augmented by representative mature tRNA sequences. Using both simulated and real life data we show that our best-practice workflow removes most of the mapping artefacts introduced by simpler mapping schemes and makes it possible to reliably identify many of chemical tRNA modifications in generic small RNA-seq data. Using simulated data the FDR is only 2%. We find compelling evidence for tissue specific differences of tRNA modification patterns. Availability and implementation The workflow is available both as a bash script and as a Galaxy workflow from https://github.com/AnneHoffmann/tRNA-read-mapping. Contact fabian@tbi.univie.ac.at. Supplementary information Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Anne Hoffmann
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, D-04107 Leipzig, Germany
| | - Jörg Fallmann
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, D-04107 Leipzig, Germany
| | - Elisa Vilardo
- Center for Anatomy and Cell Biology, Medical University of Vienna, Austria
| | - Mario Mörl
- Institute for Biochemistry, Leipzig University, D-04103 Leipzig, Germany
| | - Peter F Stadler
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, D-04107 Leipzig, Germany.,German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Competence Center for Scalable Data Services and Solutions, and Leipzig Research Center for Civilization Diseases, Leipzig University, D-04107 Leipzig, Germany.,Max Planck Institute for Mathematics in the Sciences, D-04103 Leipzig, Germany.,Fraunhofer Institute for Cell Therapy and Immunology, D-04103 Leipzig, Germany.,Center for RNA in Technology and Health, University of Copenhagen, Frederiksberg C, Denmark.,Santa Fe Institute, Santa Fe, NM 87501, USA.,Department of Theoretical Chemistry of the University of Vienna, A-1090 Vienna, Austria
| | - Fabian Amman
- Department of Theoretical Chemistry of the University of Vienna, A-1090 Vienna, Austria.,Department of Chromosome Biology of the University of Vienna, A-1030 Vienna, Austria
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18
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Chambers AE, Richardson AE, Read DF, Waller TJ, Bernstein DA, Smaldino PJ. An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity. J Vis Exp 2018. [PMID: 30346392 DOI: 10.3791/58100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
N6-isopentenyladenosine RNA modifications are functionally diverse and highly conserved among prokaryotes and eukaryotes. One of the most highly conserved N6-isopentenyladenosine modifications occurs at the A37 position in a subset of tRNAs. This modification improves translation efficiency and fidelity by increasing the affinity of the tRNA for the ribosome. Mutation of enzymes responsible for this modification in eukaryotes are associated with several disease states, including mitochondrial dysfunction and cancer. Therefore, understanding the substrate specificity and biochemical activities of these enzymes is important for understanding of normal and pathologic eukaryotic biology. A diverse array of methods has been employed to characterize i6A modifications. Herein is described a direct approach for the detection of isopentenylation by Mod5. This method utilizes incubation of RNAs with a recombinant isopentenyl transferase, followed by RNase T1 digestion, and 1-dimensional gel electrophoresis analysis to detect i6A modifications. In addition, the potential adaptability of this protocol to characterize other RNA-modifying enzymes is discussed.
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Affiliation(s)
| | | | - David F Read
- Department of Genome Sciences, University of Washington
| | - Thomas J Waller
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan
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19
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Seegobin M, Kisiala A, Noble A, Kaplan D, Brunetti C, Emery RJN. Canis familiaris tissues are characterized by different profiles of cytokinins typical of the tRNA degradation pathway. FASEB J 2018; 32:fj201800347. [PMID: 29894666 DOI: 10.1096/fj.201800347] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Cytokinins (CKs) are a group of phytohormones essential to plant growth and development. The presence of these N6-modified adenine derivatives has also been documented in other groups of organisms, including bacteria, fungi, and insects. Thus far, however, only a single CK, N6-(Δ2-isopentenyl) adenine-9-riboside (iPR), has been identified in mammals. In plants, the nucleotide form of isopentenyladenine [iPR (either mono-, di-, or tri-) phosphate (iPRP)] is the first form of CK synthesized, and it is further modified to produce other CK types. To determine if a similar biosynthesis pathway exists in mammals, we tested for the presence of 27 CKs in a wide selection of canine organs using HPLC electrospray ionization-tandem mass spectrometry. Seven forms of CK were detected in the majority of the analyzed samples, including iPR, iPRP, cis-zeatin-9-riboside, cis-zeatin-9-riboside-5' (either mono-, di-, or triphosphate), 2-methylthio-N6-isopentenyladenine, 2-methylthio-N6-isopentenyladenosine, and 2-methylthio-zeatin. Total CK concentrations ranged from 1.96 pmol/g fresh weight (adrenal glands) to 1.40 × 103 pmol/g fresh weight (thyroid). The results of this study provide evidence that mammalian cells, like plant cells, can synthesize and process a diverse set of CKs including cis- and methylthiol-type CKs.-Seegobin, M., Kisiala, A., Noble, A., Kaplan, D., Brunetti, C., Emery, R. J. N. Canis familiaris tissues are characterized by different profiles of cytokinins typical of tRNA degradation pathway.
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Affiliation(s)
- Mark Seegobin
- Department of Biology, Trent University, Peterborough, Ontario, Canada
| | - Anna Kisiala
- Department of Biology, Trent University, Peterborough, Ontario, Canada
| | | | - David Kaplan
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Craig Brunetti
- Department of Biology, Trent University, Peterborough, Ontario, Canada
| | - R J Neil Emery
- Department of Biology, Trent University, Peterborough, Ontario, Canada
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20
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Marín M, Fernández-Calero T, Ehrlich R. Protein folding and tRNA biology. Biophys Rev 2017; 9:573-588. [PMID: 28944442 PMCID: PMC5662057 DOI: 10.1007/s12551-017-0322-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 08/28/2017] [Indexed: 12/14/2022] Open
Abstract
Polypeptides can fold into tertiary structures while they are synthesized by the ribosome. In addition to the amino acid sequence, protein folding is determined by several factors within the cell. Among others, the folding pathway of a nascent polypeptide can be affected by transient interactions with other proteins, ligands, or the ribosome, as well as by the translocation through membrane pores. Particularly, the translation machinery and the population of tRNA under different physiological or adaptive responses can dramatically affect protein folding. This review summarizes the scientific evidence describing the role of translation kinetics and tRNA populations on protein folding and addresses current efforts to better understand tRNA biology. It is organized into three main parts, which are focused on: (i) protein folding in the cellular context; (ii) tRNA biology and the complexity of the tRNA population; and (iii) available methods and technical challenges in the characterization of tRNA pools. In this manner, this work illustrates the ways by which functional properties of proteins may be modulated by cellular tRNA populations.
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Affiliation(s)
- Mónica Marín
- Biochemistry-Molecular Biology Section, Cellular and Molecular Biology Department, Faculty of Sciences, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
| | - Tamara Fernández-Calero
- Biochemistry-Molecular Biology Section, Cellular and Molecular Biology Department, Faculty of Sciences, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
- Bioinformatics Unit, Institut Pasteur Montevideo, Mataojo 2020, 11400 Montevideo, Uruguay
| | - Ricardo Ehrlich
- Biochemistry-Molecular Biology Section, Cellular and Molecular Biology Department, Faculty of Sciences, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
- Institut Pasteur Montevideo, Mataojo 2020, 11400 Montevideo, Uruguay
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21
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Zheng C, Black KA, Dos Santos PC. Diverse Mechanisms of Sulfur Decoration in Bacterial tRNA and Their Cellular Functions. Biomolecules 2017; 7:biom7010033. [PMID: 28327539 PMCID: PMC5372745 DOI: 10.3390/biom7010033] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 03/10/2017] [Accepted: 03/16/2017] [Indexed: 01/01/2023] Open
Abstract
Sulfur-containing transfer ribonucleic acids (tRNAs) are ubiquitous biomolecules found in all organisms that possess a variety of functions. For decades, their roles in processes such as translation, structural stability, and cellular protection have been elucidated and appreciated. These thionucleosides are found in all types of bacteria; however, their biosynthetic pathways are distinct among different groups of bacteria. Considering that many of the thio-tRNA biosynthetic enzymes are absent in Gram-positive bacteria, recent studies have addressed how sulfur trafficking is regulated in these prokaryotic species. Interestingly, a novel proposal has been given for interplay among thionucleosides and the biosynthesis of other thiocofactors, through participation of shared-enzyme intermediates, the functions of which are impacted by the availability of substrate as well as metabolic demand of thiocofactors. This review describes the occurrence of thio-modifications in bacterial tRNA and current methods for detection of these modifications that have enabled studies on the biosynthesis and functions of S-containing tRNA across bacteria. It provides insight into potential modes of regulation and potential evolutionary events responsible for divergence in sulfur metabolism among prokaryotes.
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Affiliation(s)
- Chenkang Zheng
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27101, USA.
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22
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Maraia RJ, Arimbasseri AG. Factors That Shape Eukaryotic tRNAomes: Processing, Modification and Anticodon-Codon Use. Biomolecules 2017; 7:biom7010026. [PMID: 28282871 PMCID: PMC5372738 DOI: 10.3390/biom7010026] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 02/24/2017] [Indexed: 01/24/2023] Open
Abstract
Transfer RNAs (tRNAs) contain sequence diversity beyond their anticodons and the large variety of nucleotide modifications found in all kingdoms of life. Some modifications stabilize structure and fit in the ribosome whereas those to the anticodon loop modulate messenger RNA (mRNA) decoding activity more directly. The identities of tRNAs with some universal anticodon loop modifications vary among distant and parallel species, likely to accommodate fine tuning for their translation systems. This plasticity in positions 34 (wobble) and 37 is reflected in codon use bias. Here, we review convergent evidence that suggest that expansion of the eukaryotic tRNAome was supported by its dedicated RNA polymerase III transcription system and coupling to the precursor-tRNA chaperone, La protein. We also review aspects of eukaryotic tRNAome evolution involving G34/A34 anticodon-sparing, relation to A34 modification to inosine, biased codon use and regulatory information in the redundancy (synonymous) component of the genetic code. We then review interdependent anticodon loop modifications involving position 37 in eukaryotes. This includes the eukaryote-specific tRNA modification, 3-methylcytidine-32 (m3C32) and the responsible gene, TRM140 and homologs which were duplicated and subspecialized for isoacceptor-specific substrates and dependence on i6A37 or t6A37. The genetics of tRNA function is relevant to health directly and as disease modifiers.
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Affiliation(s)
- Richard J Maraia
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
- Commissioned Corps, U.S. Public Health Service, Rockville, MD, 20016, USA.
| | - Aneeshkumar G Arimbasseri
- Molecular Genetics Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
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23
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Schweizer U, Bohleber S, Fradejas-Villar N. The modified base isopentenyladenosine and its derivatives in tRNA. RNA Biol 2017; 14:1197-1208. [PMID: 28277934 PMCID: PMC5699536 DOI: 10.1080/15476286.2017.1294309] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Base 37 in tRNA, 3′-adjacent to the anticodon, is occupied by a purine base that is thought to stabilize codon recognition by stacking interactions on the first Watson-Crick base pair. If the first codon position forms an A.U or U.A base pair, the purine is likely further modified in all domains of life. One of the first base modifications found in tRNA is N6-isopentenyl adenosine (i6A) present in a fraction of tRNAs in bacteria and eukaryotes, which can be further modified to 2-methyl-thio-N6-isopentenyladenosine (ms2i6A) in a subset of tRNAs. Homologous tRNA isopentenyl transferase enzymes have been identified in bacteria (MiaA), yeast (Mod5, Tit1), roundworm (GRO-1), and mammals (TRIT1). In eukaryotes, isopentenylation of cytoplasmic and mitochondrial tRNAs is mediated by products of the same gene. Accordingly, a patient with homozygous mutations in TRIT1 has mitochondrial disease. The role of i6A in a subset of tRNAs in gene expression has been linked with translational fidelity, speed of translation, skewed gene expression, and non-sense suppression. This review will not cover the action of i6A as a cytokinin in plants or the potential function of Mod5 as a prion in yeast.
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Affiliation(s)
- Ulrich Schweizer
- a Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn , Bonn , Germany
| | - Simon Bohleber
- a Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn , Bonn , Germany
| | - Noelia Fradejas-Villar
- a Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn , Bonn , Germany
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24
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Arimbasseri AG, Iben J, Wei FY, Rijal K, Tomizawa K, Hafner M, Maraia RJ. Evolving specificity of tRNA 3-methyl-cytidine-32 (m3C32) modification: a subset of tRNAsSer requires N6-isopentenylation of A37. RNA (NEW YORK, N.Y.) 2016; 22:1400-10. [PMID: 27354703 PMCID: PMC4986895 DOI: 10.1261/rna.056259.116] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Accepted: 05/24/2016] [Indexed: 05/10/2023]
Abstract
Post-transcriptional modifications of anticodon loop (ACL) nucleotides impact tRNA structure, affinity for the ribosome, and decoding activity, and these activities can be fine-tuned by interactions between nucleobases on either side of the anticodon. A recently discovered ACL modification circuit involving positions 32, 34, and 37 is disrupted by a human disease-associated mutation to the gene encoding a tRNA modification enzyme. We used tRNA-HydroSeq (-HySeq) to examine (3)methyl-cytidine-32 (m(3)C32), which is found in yeast only in the ACLs of tRNAs(Ser) and tRNAs(Thr) In contrast to that reported for Saccharomyces cerevisiae in which all m(3)C32 depends on a single gene, TRM140, the m(3)C32 of tRNAs(Ser) and tRNAs(Thr) of the fission yeast S. pombe, are each dependent on one of two related genes, trm140(+) and trm141(+), homologs of which are found in higher eukaryotes. Interestingly, mammals and other vertebrates contain a third homolog and also contain m(3)C at new sites, positions 32 on tRNAs(Arg) and C47:3 in the variable arm of tRNAs(Ser) More significantly, by examining S. pombe mutants deficient for other modifications, we found that m(3)C32 on the three tRNAs(Ser) that contain anticodon base A36, requires N(6)-isopentenyl modification of A37 (i(6)A37). This new C32-A37 ACL circuitry indicates that i(6)A37 is a pre- or corequisite for m(3)C32 on these tRNAs. Examination of the tRNA database suggests that such circuitry may be more expansive than observed here. The results emphasize two contemporary themes, that tRNA modifications are interconnected, and that some specific modifications on tRNAs of the same anticodon identity are species-specific.
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Affiliation(s)
- Aneeshkumar G Arimbasseri
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - James Iben
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Fan-Yan Wei
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, 860-0862 Kumamoto, Japan
| | - Keshab Rijal
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, 860-0862 Kumamoto, Japan
| | - Markus Hafner
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Richard J Maraia
- Commissioned Corps, US Public Health Service, Washington, DC 20201, USA
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Lamichhane TN, Arimbasseri AG, Rijal K, Iben JR, Wei FY, Tomizawa K, Maraia RJ. Lack of tRNA-i6A modification causes mitochondrial-like metabolic deficiency in S. pombe by limiting activity of cytosolic tRNATyr, not mito-tRNA. RNA (NEW YORK, N.Y.) 2016; 22:583-96. [PMID: 26857223 PMCID: PMC4793213 DOI: 10.1261/rna.054064.115] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 12/28/2015] [Indexed: 05/17/2023]
Abstract
tRNA-isopentenyl transferases (IPTases) are highly conserved enzymes that form isopentenyl-N(6)-A37 (i6A37) on subsets of tRNAs, enhancing their translation activity. Nuclear-encoded IPTases modify select cytosolic (cy-) and mitochondrial (mt-) tRNAs. Mutation in human IPTase, TRIT1, causes disease phenotypes characteristic of mitochondrial translation deficiency due to mt-tRNA dysfunction. Deletion of the Schizosaccharomyces pombe IPTase (tit1-Δ) causes slow growth in glycerol, as well as in rapamycin, an inhibitor of TOR kinase that maintains metabolic homeostasis. Schizosaccharomyces pombe IPTase modifies three different cy-tRNAs(Ser) as well as cy-tRNA(Tyr), cy-tRNA(Trp), and mt-tRNA(Trp). We show that lower ATP levels in tit1-Δ relative to tit1(+) cells are also more decreased by an inhibitor of oxidative phosphorylation, indicative of mitochondrial dysfunction. Here we asked if the tit1-Δ phenotypes are due to hypomodification of cy-tRNA or mt-tRNA. A cytosol-specific IPTase that modifies cy-tRNA, but not mt-tRNA, fully rescues the tit1-Δ phenotypes. Moreover, overexpression of cy-tRNAs also rescues the phenotypes, and cy-tRNA(Tyr) alone substantially does so. Bioinformatics indicate that cy-tRNA(Tyr) is most limiting for codon demand in tit1-Δ cells and that the cytosolic mRNAs most loaded with Tyr codons encode carbon metabolilizing enzymes, many of which are known to localize to mitochondria. Thus, S. pombe i6A37 hypomodification-associated metabolic deficiency results from hypoactivity of cy-tRNA, mostly tRNA(Tyr), and unlike human TRIT1-deficiency does not impair mitochondrial translation due to mt-tRNA hypomodification. We discuss species-specific aspects of i6A37. Specifically relevant to mitochondria, we show that its hypermodified version, ms2i6A37 (2-methylthiolated), which occurs on certain mammalian mt-tRNAs (but not cy-tRNAs), is not found in yeast.
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Affiliation(s)
- Tek N Lamichhane
- Section on Molecular and Cell Biology, Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Aneeshkumar G Arimbasseri
- Section on Molecular and Cell Biology, Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Keshab Rijal
- Section on Molecular and Cell Biology, Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - James R Iben
- Molecular Genetics Laboratory, Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Fan Yan Wei
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, 860-0862 Kumamoto, Japan
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, 860-0862 Kumamoto, Japan
| | - Richard J Maraia
- Section on Molecular and Cell Biology, Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA Commissioned Corps, US Public Health Service, Rockville, Maryland 20016, USA
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RNA Polymerase III Output Is Functionally Linked to tRNA Dimethyl-G26 Modification. PLoS Genet 2015; 11:e1005671. [PMID: 26720005 PMCID: PMC4697793 DOI: 10.1371/journal.pgen.1005671] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 10/26/2015] [Indexed: 11/19/2022] Open
Abstract
Control of the differential abundance or activity of tRNAs can be important determinants of gene regulation. RNA polymerase (RNAP) III synthesizes all tRNAs in eukaryotes and it derepression is associated with cancer. Maf1 is a conserved general repressor of RNAP III under the control of the target of rapamycin (TOR) that acts to integrate transcriptional output and protein synthetic demand toward metabolic economy. Studies in budding yeast have indicated that the global tRNA gene activation that occurs with derepression of RNAP III via maf1-deletion is accompanied by a paradoxical loss of tRNA-mediated nonsense suppressor activity, manifested as an antisuppression phenotype, by an unknown mechanism. We show that maf1-antisuppression also occurs in the fission yeast S. pombe amidst general activation of RNAP III. We used tRNA-HydroSeq to document that little changes occurred in the relative levels of different tRNAs in maf1Δ cells. By contrast, the efficiency of N2,N2-dimethyl G26 (m(2)2G26) modification on certain tRNAs was decreased in response to maf1-deletion and associated with antisuppression, and was validated by other methods. Over-expression of Trm1, which produces m(2)2G26, reversed maf1-antisuppression. A model that emerges is that competition by increased tRNA levels in maf1Δ cells leads to m(2)2G26 hypomodification due to limiting Trm1, reducing the activity of suppressor-tRNASerUCA and accounting for antisuppression. Consistent with this, we show that RNAP III mutations associated with hypomyelinating leukodystrophy decrease tRNA transcription, increase m(2)2G26 efficiency and reverse antisuppression. Extending this more broadly, we show that a decrease in tRNA synthesis by treatment with rapamycin leads to increased m(2)2G26 modification and that this response is conserved among highly divergent yeasts and human cells.
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The importance of codon–anticodon interactions in translation elongation. Biochimie 2015; 114:72-9. [DOI: 10.1016/j.biochi.2015.04.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 04/16/2015] [Indexed: 11/16/2022]
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Rojas-Benitez D, Thiaville PC, de Crécy-Lagard V, Glavic A. The Levels of a Universally Conserved tRNA Modification Regulate Cell Growth. J Biol Chem 2015; 290:18699-707. [PMID: 26063805 DOI: 10.1074/jbc.m115.665406] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Indexed: 01/05/2023] Open
Abstract
N(6)-Threonylcarbamoyl-adenosine (t(6)A) is a universal modification occurring at position 37 in nearly all tRNAs that decode A-starting codons, including the eukaryotic initiator tRNA (tRNAi (Met)). Yeast lacking central components of the t(6)A synthesis machinery, such as Tcs3p (Kae1p) or Tcs5p (Bud32p), show slow-growth phenotypes. In the present work, we show that loss of the Drosophila tcs3 homolog also leads to a severe reduction in size and demonstrate, for the first time in a non-microbe, that Tcs3 is required for t(6)A synthesis. In Drosophila and in mammals, tRNAi (Met) is a limiting factor for cell and animal growth. We report that the t(6)A-modified form of tRNAi (Met) is the actual limiting factor. We show that changing the proportion of t(6)A-modified tRNAi (Met), by expression of an un-modifiable tRNAi (Met) or changing the levels of Tcs3, regulate target of rapamycin (TOR) kinase activity and influences cell and animal growth in vivo. These findings reveal an unprecedented relationship between the translation machinery and TOR, where translation efficiency, limited by the availability of t(6)A-modified tRNA, determines growth potential in eukaryotic cells.
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Affiliation(s)
- Diego Rojas-Benitez
- From the Centro de Regulación del Genoma, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile 7800024 and
| | - Patrick C Thiaville
- the Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida32611-0700
| | - Valérie de Crécy-Lagard
- the Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida32611-0700
| | - Alvaro Glavic
- From the Centro de Regulación del Genoma, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile 7800024 and
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Rijal K, Maraia RJ, Arimbasseri AG. A methods review on use of nonsense suppression to study 3' end formation and other aspects of tRNA biogenesis. Gene 2014; 556:35-50. [PMID: 25447915 DOI: 10.1016/j.gene.2014.11.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 11/13/2014] [Accepted: 11/14/2014] [Indexed: 12/26/2022]
Abstract
Suppressor tRNAs bear anticodon mutations that allow them to decode premature stop codons in metabolic marker gene mRNAs, that can be used as in vivo reporters of functional tRNA biogenesis. Here, we review key components of a suppressor tRNA system specific to Schizosaccharomyces pombe and its adaptations for use to study specific steps in tRNA biogenesis. Eukaryotic tRNA biogenesis begins with transcription initiation by RNA polymerase (pol) III. The nascent pre-tRNAs must undergo folding, 5' and 3' processing to remove the leader and trailer, nuclear export, and splicing if applicable, while multiple complex chemical modifications occur throughout the process. We review evidence that precursor-tRNA processing begins with transcription termination at the oligo(T) terminator element, which forms a 3' oligo(U) tract on the nascent RNA, a sequence-specific binding site for the RNA chaperone, La protein. The processing pathway bifurcates depending on a poorly understood property of pol III termination that determines the 3' oligo(U) length and therefore the affinity for La. We thus review the pol III termination process and the factors involved including advances using gene-specific random mutagenesis by dNTP analogs that identify key residues important for transcription termination in certain pol III subunits. The review ends with a 'technical approaches' section that includes a parts lists of suppressor-tRNA alleles, strains and plasmids, and graphic examples of its diverse uses.
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Affiliation(s)
- Keshab Rijal
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Richard J Maraia
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
| | - Aneeshkumar G Arimbasseri
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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Smaldino PJ, Read DF, Pratt-Hyatt M, Hopper AK, Engelke DR. The cytoplasmic and nuclear populations of the eukaryote tRNA-isopentenyl transferase have distinct functions with implications in human cancer. Gene 2014; 556:13-8. [PMID: 25261850 DOI: 10.1016/j.gene.2014.09.049] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 09/22/2014] [Accepted: 09/23/2014] [Indexed: 12/29/2022]
Abstract
Mod5 is the yeast tRNA isopentenyl transferase, an enzyme that is conserved from bacteria to humans. Mod5 is primarily cytoplasmic where it modifies the A37 position of a few tRNAs, and the yeast enzyme has been shown capable of forming heritable, amyloid-like aggregates that confer a selective advantage in the presence of specific antifungal agents. A subpopulation of Mod5 is also found associated with nuclear tRNA genes, where it contributes tRNA-gene mediated (tgm) silencing of local transcription by RNA polymerase II. The tgm-silencing function of Mod5 has been observed in yeast and a Mod5-deletion in yeast can be complemented by the plant and human tRNA isopentenyl transferases, but not the bacterial enzymes, possibly due to the lack of an extended C-terminal domain found in eukaryotes. In light of this additional nuclear role for Mod5 we discuss the proposed role of the human homologue of Mod5, TRIT1, as a tumor suppressor protein.
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Affiliation(s)
- P J Smaldino
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
| | - D F Read
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - M Pratt-Hyatt
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; The Great Plains Laboratory, 11813W. 77th St. Lenexa KS 66214, USA
| | - A K Hopper
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - D R Engelke
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
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Abstract
Whole-genome and functional analyses suggest a wealth of secondary or auxiliary genetic information (AGI) within the redundancy component of the genetic code. Although there are multiple aspects of biased codon use, we focus on two types of auxiliary information: codon-specific translational pauses that can be used by particular proteins toward their unique folding and biased codon patterns shared by groups of functionally related mRNAs with coordinate regulation. AGI is important to genetics in general and to human disease; here, we consider influences of its three major components, biased codon use itself, variations in the tRNAome, and anticodon modifications that distinguish synonymous decoding. AGI is plastic and can be used by different species to different extents, with tissue-specificity and in stress responses. Because AGI is species-specific, it is important to consider codon-sensitive experiments when using heterologous systems; for this we focus on the tRNA anticodon loop modification enzyme, CDKAL1, and its link to type 2 diabetes. Newly uncovered tRNAome variability among humans suggests roles in penetrance and as a genetic modifier and disease modifier. Development of experimental and bioinformatics methods are needed to uncover additional means of auxiliary genetic information.
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Affiliation(s)
- Richard J. Maraia
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
- Corresponding authorE-mail
| | - James R. Iben
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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Yarham JW, Lamichhane TN, Pyle A, Mattijssen S, Baruffini E, Bruni F, Donnini C, Vassilev A, He L, Blakely EL, Griffin H, Santibanez-Koref M, Bindoff LA, Ferrero I, Chinnery PF, McFarland R, Maraia RJ, Taylor RW. Defective i6A37 modification of mitochondrial and cytosolic tRNAs results from pathogenic mutations in TRIT1 and its substrate tRNA. PLoS Genet 2014; 10:e1004424. [PMID: 24901367 PMCID: PMC4046958 DOI: 10.1371/journal.pgen.1004424] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 04/20/2014] [Indexed: 01/10/2023] Open
Abstract
Identifying the genetic basis for mitochondrial diseases is technically challenging given the size of the mitochondrial proteome and the heterogeneity of disease presentations. Using next-generation exome sequencing, we identified in a patient with severe combined mitochondrial respiratory chain defects and corresponding perturbation in mitochondrial protein synthesis, a homozygous p.Arg323Gln mutation in TRIT1. This gene encodes human tRNA isopentenyltransferase, which is responsible for i6A37 modification of the anticodon loops of a small subset of cytosolic and mitochondrial tRNAs. Deficiency of i6A37 was previously shown in yeast to decrease translational efficiency and fidelity in a codon-specific manner. Modelling of the p.Arg323Gln mutation on the co-crystal structure of the homologous yeast isopentenyltransferase bound to a substrate tRNA, indicates that it is one of a series of adjacent basic side chains that interact with the tRNA backbone of the anticodon stem, somewhat removed from the catalytic center. We show that patient cells bearing the p.Arg323Gln TRIT1 mutation are severely deficient in i6A37 in both cytosolic and mitochondrial tRNAs. Complete complementation of the i6A37 deficiency of both cytosolic and mitochondrial tRNAs was achieved by transduction of patient fibroblasts with wild-type TRIT1. Moreover, we show that a previously-reported pathogenic m.7480A>G mt-tRNASer(UCN) mutation in the anticodon loop sequence A36A37A38 recognised by TRIT1 causes a loss of i6A37 modification. These data demonstrate that deficiencies of i6A37 tRNA modification should be considered a potential mechanism of human disease caused by both nuclear gene and mitochondrial DNA mutations while providing insight into the structure and function of TRIT1 in the modification of cytosolic and mitochondrial tRNAs. Mitochondrial disorders are clinically diverse, and identifying the underlying genetic mutations is technically challenging due to the large number of mitochondrial proteins. Using high-throughput sequencing technology, we identified a disease-causing mutation in the TRIT1 gene. This gene encodes an enzyme, tRNA isopentenyltransferase, that adds an N6-isopentenyl modification to adenosine-37 (i6A37) in a small number of tRNAs, enabling them to function correctly during the synthesis of essential mitochondrial proteins. We show that this mutation leads to severe deficiency of tRNA-i6A37 in the patient's cells that can be rescued by introduction of the wild-type TRIT1 protein. A deficiency in oxidative phosphorylation, the process by which energy (ATP) is generated in the mitochondria, leads to a mitochondrial disease presentation. Introducing the mutant protein into model yeast species and measuring the resulting impairment provided further evidence of the pathogenic effect of the mutation. Additional studies investigating a previously reported pathogenic mutation in a mitochondrial tRNA gene demonstrated that a mutation in a substrate of TRIT1 can also cause a loss of the modification, providing evidence of a new mechanism causing mitochondrial disease in humans.
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Affiliation(s)
- John W. Yarham
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Tek N. Lamichhane
- Intramural Research Program, NICHD, NIH, Bethesda, Maryland, United States of America
| | - Angela Pyle
- Wellcome Trust Centre for Mitochondrial Research, Institute for Genetic Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Sandy Mattijssen
- Intramural Research Program, NICHD, NIH, Bethesda, Maryland, United States of America
| | | | - Francesco Bruni
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Claudia Donnini
- Department of Life Sciences, University of Parma, Parma, Italy
| | - Alex Vassilev
- Intramural Research Program, NICHD, NIH, Bethesda, Maryland, United States of America
| | - Langping He
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Emma L. Blakely
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Helen Griffin
- Wellcome Trust Centre for Mitochondrial Research, Institute for Genetic Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Mauro Santibanez-Koref
- Wellcome Trust Centre for Mitochondrial Research, Institute for Genetic Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Laurence A. Bindoff
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Ileana Ferrero
- Department of Life Sciences, University of Parma, Parma, Italy
| | - Patrick F. Chinnery
- Wellcome Trust Centre for Mitochondrial Research, Institute for Genetic Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Richard J. Maraia
- Intramural Research Program, NICHD, NIH, Bethesda, Maryland, United States of America
- * E-mail: (RJM) (RM); (RWT) (RT)
| | - Robert W. Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
- * E-mail: (RJM) (RM); (RWT) (RT)
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Eichhorn CD, Kang M, Feigon J. Structure and function of preQ 1 riboswitches. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:939-950. [PMID: 24798077 DOI: 10.1016/j.bbagrm.2014.04.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 04/22/2014] [Accepted: 04/25/2014] [Indexed: 12/17/2022]
Abstract
PreQ1 riboswitches help regulate the biosynthesis and transport of preQ1 (7-aminomethyl-7-deazaguanine), a precursor of the hypermodified guanine nucleotide queuosine (Q), in a number of Firmicutes, Proteobacteria, and Fusobacteria. Queuosine is almost universally found at the wobble position of the anticodon in asparaginyl, tyrosyl, histidyl and aspartyl tRNAs, where it contributes to translational fidelity. Two classes of preQ1 riboswitches have been identified (preQ1-I and preQ1-II), and structures of examples from both classes have been determined. Both classes form H-type pseudoknots upon preQ1 binding, each of which has distinct unusual features and modes of preQ1 recognition. These features include an unusually long loop 2 in preQ1-I pseudoknots and an embedded hairpin in loop 3 in preQ1-II pseudoknots. PreQ1-I riboswitches are also notable for their unusually small aptamer domain, which has been extensively investigated by NMR, X-ray crystallography, FRET, and other biophysical methods. Here we review the discovery, structural biology, ligand specificity, cation interactions, folding, dynamics, and applications to biotechnology of preQ1 riboswitches. This article is part of a Special Issue entitled: Riboswitches.
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Affiliation(s)
- Catherine D Eichhorn
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Mijeong Kang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA; UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, CA 90095, USA
| | - Juli Feigon
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA; UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, CA 90095, USA
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Posttranscriptional RNA Modifications: playing metabolic games in a cell's chemical Legoland. ACTA ACUST UNITED AC 2013; 21:174-85. [PMID: 24315934 DOI: 10.1016/j.chembiol.2013.10.015] [Citation(s) in RCA: 164] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/24/2013] [Accepted: 10/30/2013] [Indexed: 12/15/2022]
Abstract
Nature combines existing biochemical building blocks, at times with subtlety of purpose. RNA modifications are a prime example of this, where standard RNA nucleosides are decorated with chemical groups and building blocks that we recall from our basic biochemistry lectures. The result: a wealth of chemical diversity whose full biological relevance has remained elusive despite being public knowledge for some time. Here, we highlight several modifications that, because of their chemical intricacy, rely on seemingly unrelated pathways to provide cofactors for their synthesis. Besides their immediate role in affecting RNA function, modifications may act as sensors and transducers of information that connect a cell's metabolic state to its translational output, carefully orchestrating a delicate balance between metabolic rate and protein synthesis at a system's level.
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Human cells have a limited set of tRNA anticodon loop substrates of the tRNA isopentenyltransferase TRIT1 tumor suppressor. Mol Cell Biol 2013; 33:4900-8. [PMID: 24126054 DOI: 10.1128/mcb.01041-13] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Human TRIT1 is a tRNA isopentenyltransferase (IPTase) homologue of Escherichia coli MiaA, Saccharomyces cerevisiae Mod5, Schizosaccharomyces pombe Tit1, and Caenorhabditis elegans GRO-1 that adds isopentenyl groups to adenosine 37 (i6A37) of substrate tRNAs. Prior studies indicate that i6A37 increases translation fidelity and efficiency in codon-specific ways. TRIT1 is a tumor suppressor whose mutant alleles are associated with cancer progression. We report the systematic identification of i6A37-containing tRNAs in a higher eukaryote, performed using small interfering RNA knockdown and other methods to examine TRIT1 activity in HeLa cells. Although several potential substrates contained the IPTase recognition sequence A36A37A38 in the anticodon loop, only tRNA(Ser)AGA, tRNA(Ser)CGA, tRNA(Ser)UGA, and selenocysteine tRNA with UCA (tRNA([Ser]Sec)UCA) contained i6A37. This subset is a significantly more restricted than that for two distant yeasts (S. cerevisiae and S. pombe), the only other organisms comprehensively examined. Unlike the fully i6A37-modified tRNAs for Ser, tRNA([Ser]Sec)UCA is partially (∼40%) modified. Exogenous selenium and other treatments that decreased the i6A37 content of tRNA([Ser]Sec)UCA led to increased levels of the tRNA([Ser]Sec)UCA. Of the human mitochondrion (mt)-encoded tRNAs with A36A37A38, only mt tRNAs tRNA(Ser)UGA and tRNA(Trp)UCA contained detectable i6A37. Moreover, while tRNA(Ser) levels were unaffected by TRIT1 knockdown, the tRNA([Ser]Sec)UCA level was increased and the mt tRNA(Ser)UGA level was decreased, suggesting that TRIT1 may control the levels of some tRNAs as well as their specific activity.
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Gisselberg JE, Dellibovi-Ragheb TA, Matthews KA, Bosch G, Prigge ST. The suf iron-sulfur cluster synthesis pathway is required for apicoplast maintenance in malaria parasites. PLoS Pathog 2013; 9:e1003655. [PMID: 24086138 PMCID: PMC3784473 DOI: 10.1371/journal.ppat.1003655] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 08/12/2013] [Indexed: 11/19/2022] Open
Abstract
The apicoplast organelle of the malaria parasite Plasmodium falciparum contains metabolic pathways critical for liver-stage and blood-stage development. During the blood stages, parasites lacking an apicoplast can grow in the presence of isopentenyl pyrophosphate (IPP), demonstrating that isoprenoids are the only metabolites produced in the apicoplast which are needed outside of the organelle. Two of the isoprenoid biosynthesis enzymes are predicted to rely on iron-sulfur (FeS) cluster cofactors, however, little is known about FeS cluster synthesis in the parasite or the roles that FeS cluster proteins play in parasite biology. We investigated two putative FeS cluster synthesis pathways (Isc and Suf) focusing on the initial step of sulfur acquisition. In other eukaryotes, these proteins can be located in multiple subcellular compartments, raising the possibility of cross-talk between the pathways or redundant functions. In P. falciparum, SufS and its partner SufE were found exclusively the apicoplast and SufS was shown to have cysteine desulfurase activity in a complementation assay. IscS and its effector Isd11 were solely mitochondrial, suggesting that the Isc pathway cannot contribute to apicoplast FeS cluster synthesis. The Suf pathway was disrupted with a dominant negative mutant resulting in parasites that were only viable when supplemented with IPP. These parasites lacked the apicoplast organelle and its organellar genome--a phenotype not observed when isoprenoid biosynthesis was specifically inhibited with fosmidomycin. Taken together, these results demonstrate that the Suf pathway is essential for parasite survival and has a fundamental role in maintaining the apicoplast organelle in addition to any role in isoprenoid biosynthesis.
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Affiliation(s)
- Jolyn E. Gisselberg
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Teegan A. Dellibovi-Ragheb
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Krista A. Matthews
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Gundula Bosch
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Sean T. Prigge
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- * E-mail:
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Lack of tRNA modification isopentenyl-A37 alters mRNA decoding and causes metabolic deficiencies in fission yeast. Mol Cell Biol 2013; 33:2918-29. [PMID: 23716598 DOI: 10.1128/mcb.00278-13] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
tRNA isopentenyltransferases (Tit1) modify tRNA position 37, adjacent to the anticodon, to N6-isopentenyladenosine (i6A37) in all cells, yet the tRNA subsets selected for modification vary among species, and their relevance to phenotypes is unknown. We examined the function of i6A37 in Schizosaccharomyces pombe tit1+ and tit1-Δ cells by using a β-galactosidase codon-swap reporter whose catalytic activity is sensitive to accurate decoding of codon 503. i6A37 increased the activity of tRNACys at a cognate codon and that of tRNATyr at a near-cognate codon, suggesting that i6A37 promotes decoding activity generally and increases fidelity at cognate codons while decreasing fidelity at noncognate codons. S. pombe cells lacking tit1+ exhibit slow growth in glycerol or rapamycin. While existing data link wobble base U34 modifications to translation of functionally related mRNAs, whether this might extend to the anticodon-adjacent position 37 was unknown. Indeed, we found a biased presence of i6A37-cognate codons in high-abundance mRNAs for ribosome subunits and energy metabolism, congruent with the observed phenotypes and the idea that i6A37 promotes translational efficiency. Polysome profiles confirmed the decreased translational efficiency of mRNAs in tit1-Δ cells. Because subsets of i6A37-tRNAs differ among species, as do their cognate codon-sensitive mRNAs, these genomic variables may underlie associated phenotypic differences.
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Mammalian Trit1 is a tRNA([Ser]Sec)-isopentenyl transferase required for full selenoprotein expression. Biochem J 2013; 450:427-32. [PMID: 23289710 DOI: 10.1042/bj20121713] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Selenoproteins are proteins carrying the rare amino acid Sec (selenocysteine). Full expression of selenoproteins requires modification of tRNA([Ser]Sec), including N(6)-isopentenylation of base A(37). We show that Trit1 is a dimethylallyl:tRNA([Ser]Sec) transferase. Knockdown of Trit1 reduces expression of selenoproteins. Incubation of in vitro transcribed tRNA[Ser]Sec with recombinant Trit1 transfers [(14)C]dimethylallyl pyrophosphate to tRNA([Ser]Sec). 37A>G tRNA([Ser]Sec) is resistant to isopentenylation by Trit1.
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39
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Jackman JE, Alfonzo JD. Transfer RNA modifications: nature's combinatorial chemistry playground. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 4:35-48. [PMID: 23139145 DOI: 10.1002/wrna.1144] [Citation(s) in RCA: 222] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Following synthesis, tRNAs are peppered by numerous chemical modifications which may differentially affect a tRNA's structure and function. Although modifications affecting the business ends of a tRNA are predictably important for cell viability, a majority of modifications play more subtle structural roles that can affect tRNA stability and folding. The current trend is that modifications act in concert and it is in the context of the specific sequence of a given tRNA that they impart their differing effects. Recent developments in the modification field have highlighted the diversity of modifications in tRNA. From these, the combinatorial nature of modifications in explaining previously described phenotypes derived from their absence has emerged as a growing theme.
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Affiliation(s)
- Jane E Jackman
- The Ohio State Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
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Yamagami R, Yamashita K, Nishimasu H, Tomikawa C, Ochi A, Iwashita C, Hirata A, Ishitani R, Nureki O, Hori H. The tRNA recognition mechanism of folate/FAD-dependent tRNA methyltransferase (TrmFO). J Biol Chem 2012; 287:42480-94. [PMID: 23095745 DOI: 10.1074/jbc.m112.390112] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The conserved U54 in tRNA is often modified to 5-methyluridine (m(5)U) and forms a reverse Hoogsteen base pair with A58 that stabilizes the L-shaped tRNA structure. In Gram-positive and some Gram-negative eubacteria, m(5)U54 is produced by folate/FAD-dependent tRNA (m(5)U54) methyltransferase (TrmFO). TrmFO utilizes N(5),N(10)-methylenetetrahydrofolate (CH(2)THF) as a methyl donor. We previously reported an in vitro TrmFO assay system, in which unstable [(14)C]CH(2)THF was supplied from [(14)C]serine and tetrahydrofolate by serine hydroxymethyltransferase. In the current study, we have improved the TrmFO assay system by optimization of enzyme and substrate concentrations and introduction of a filter assay system. Using this assay, we have focused on the tRNA recognition mechanism of TrmFO. 42 tRNA mutant variants were prepared, and experiments with truncated tRNA and microhelix RNAs revealed that the minimum requirement of TrmFO exists in the T-arm structure. The positive determinants for TrmFO were found to be the U54U55C56 sequence and G53-C61 base pair. The gel mobility shift assay and fluorescence quenching showed that the affinity of TrmFO for tRNA in the initial binding process is weak. The inhibition experiments showed that the methylated tRNA is released before the structural change process. Furthermore, we found that A38 prevents incorrect methylation of U32 in the anticodon loop. Moreover, the m(1)A58 modification clearly accelerates the TrmFO reaction, suggesting a synergistic effect of the m(5)U54, m(1)A58, and s(2)U54 modifications on m(5)s(2)U54 formation in Thermus thermophilus cells. The docking model of TrmFO and the T-arm showed that the G53-C61 base pair is not able to directly contact the enzyme.
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Affiliation(s)
- Ryota Yamagami
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, 3 Bunkyo, Matsuyama, Ehime 790-8577, Japan
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