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Takuma H, Ushio N, Minoji M, Kazayama A, Shigi N, Hirata A, Tomikawa C, Ochi A, Hori H. Substrate tRNA recognition mechanism of eubacterial tRNA (m1A58) methyltransferase (TrmI). J Biol Chem 2015; 290:5912-25. [PMID: 25593312 DOI: 10.1074/jbc.m114.606038] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TrmI generates N(1)-methyladenosine at position 58 (m(1)A58) in tRNA. The Thermus thermophilus tRNA(Phe) transcript was methylated efficiently by T. thermophilus TrmI, whereas the yeast tRNA(Phe) transcript was poorly methylated. Fourteen chimeric tRNA transcripts derived from these two tRNAs revealed that TrmI recognized the combination of aminoacyl stem, variable region, and T-loop. This was confirmed by 10 deletion tRNA variants: TrmI methylated transcripts containing the aminoacyl stem, variable region, and T-arm. The requirement for the T-stem itself was confirmed by disrupting the T-stem. Disrupting the interaction between T- and D-arms accelerated the methylation, suggesting that this disruption is included in part of the reaction. Experiments with 17 point mutant transcripts elucidated the positive sequence determinants C56, purine 57, A58, and U60. Replacing A58 with inosine and 2-aminopurine completely abrogated methylation, demonstrating that the 6-amino group in A58 is recognized by TrmI. T. thermophilus tRNAGGU(Thr)GGU(Thr) contains C60 instead of U60. The tRNAGGU(Thr) transcript was poorly methylated by TrmI, and replacing C60 with U increased the methylation, consistent with the point mutation experiments. A gel shift assay revealed that tRNAGGU(Thr) had a low affinity for TrmI than tRNA(Phe). Furthermore, analysis of tRNAGGU(Thr) purified from the trmI gene disruptant strain revealed that the other modifications in tRNA accelerated the formation of m(1)A58 by TrmI. Moreover, nucleoside analysis of tRNAGGU(Thr) from the wild-type strain indicated that less than 50% of tRNAGG(Thr) contained m(1)A58. Thus, the results from the in vitro experiments were confirmed by the in vivo methylation patterns.
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Affiliation(s)
- Hiroyuki Takuma
- From the Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan and
| | - Natsumi Ushio
- From the Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan and
| | - Masayuki Minoji
- From the Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan and
| | - Ai Kazayama
- From the Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan and
| | - Naoki Shigi
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo 135-0064, Japan
| | - Akira Hirata
- From the Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan and
| | - Chie Tomikawa
- From the Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan and
| | - Anna Ochi
- From the Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan and
| | - Hiroyuki Hori
- From the Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan and
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Abstract
Mammalian messenger RNA (mRNA) and long noncoding RNA (lncRNA) contain tens of thousands of posttranscriptional chemical modifications. Among these, the N(6)-methyl-adenosine (m(6)A) modification is the most abundant and can be removed by specific mammalian enzymes. m(6)A modification is recognized by families of RNA binding proteins that affect many aspects of mRNA function. mRNA/lncRNA modification represents another layer of epigenetic regulation of gene expression, analogous to DNA methylation and histone modification.
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53
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Hori H. Methylated nucleosides in tRNA and tRNA methyltransferases. Front Genet 2014; 5:144. [PMID: 24904644 PMCID: PMC4033218 DOI: 10.3389/fgene.2014.00144] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 05/04/2014] [Indexed: 12/26/2022] Open
Abstract
To date, more than 90 modified nucleosides have been found in tRNA and the biosynthetic pathways of the majority of tRNA modifications include a methylation step(s). Recent studies of the biosynthetic pathways have demonstrated that the availability of methyl group donors for the methylation in tRNA is important for correct and efficient protein synthesis. In this review, I focus on the methylated nucleosides and tRNA methyltransferases. The primary functions of tRNA methylations are linked to the different steps of protein synthesis, such as the stabilization of tRNA structure, reinforcement of the codon-anticodon interaction, regulation of wobble base pairing, and prevention of frameshift errors. However, beyond these basic functions, recent studies have demonstrated that tRNA methylations are also involved in the RNA quality control system and regulation of tRNA localization in the cell. In a thermophilic eubacterium, tRNA modifications and the modification enzymes form a network that responses to temperature changes. Furthermore, several modifications are involved in genetic diseases, infections, and the immune response. Moreover, structural, biochemical, and bioinformatics studies of tRNA methyltransferases have been clarifying the details of tRNA methyltransferases and have enabled these enzymes to be classified. In the final section, the evolution of modification enzymes is discussed.
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Affiliation(s)
- Hiroyuki Hori
- Department of Materials Science and Biotechnology, Applied Chemistry, Graduate School of Science and Engineering, Ehime University Matsuyama, Japan
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Transfer RNA post-transcriptional processing, turnover, and subcellular dynamics in the yeast Saccharomyces cerevisiae. Genetics 2013; 194:43-67. [PMID: 23633143 DOI: 10.1534/genetics.112.147470] [Citation(s) in RCA: 145] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Transfer RNAs (tRNAs) are essential for protein synthesis. In eukaryotes, tRNA biosynthesis employs a specialized RNA polymerase that generates initial transcripts that must be subsequently altered via a multitude of post-transcriptional steps before the tRNAs beome mature molecules that function in protein synthesis. Genetic, genomic, biochemical, and cell biological approaches possible in the powerful Saccharomyces cerevisiae system have led to exciting advances in our understandings of tRNA post-transcriptional processing as well as to novel insights into tRNA turnover and tRNA subcellular dynamics. tRNA processing steps include removal of transcribed leader and trailer sequences, addition of CCA to the 3' mature sequence and, for tRNA(His), addition of a 5' G. About 20% of yeast tRNAs are encoded by intron-containing genes. The three-step splicing process to remove the introns surprisingly occurs in the cytoplasm in yeast and each of the splicing enzymes appears to moonlight in functions in addition to tRNA splicing. There are 25 different nucleoside modifications that are added post-transcriptionally, creating tRNAs in which ∼15% of the residues are nucleosides other than A, G, U, or C. These modified nucleosides serve numerous important functions including tRNA discrimination, translation fidelity, and tRNA quality control. Mature tRNAs are very stable, but nevertheless yeast cells possess multiple pathways to degrade inappropriately processed or folded tRNAs. Mature tRNAs are also dynamic in cells, moving from the cytoplasm to the nucleus and back again to the cytoplasm; the mechanism and function of this retrograde process is poorly understood. Here, the state of knowledge for tRNA post-transcriptional processing, turnover, and subcellular dynamics is addressed, highlighting the questions that remain.
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Chujo T, Suzuki T. Trmt61B is a methyltransferase responsible for 1-methyladenosine at position 58 of human mitochondrial tRNAs. RNA (NEW YORK, N.Y.) 2012; 18:2269-76. [PMID: 23097428 PMCID: PMC3504677 DOI: 10.1261/rna.035600.112] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
In human mitochondria, 1-methyladenosine (m¹A) occurs at position 58 of tRNA(Leu(UUR)). In addition, partial m¹A58 modifications have been found in human mitochondrial tRNA(Lys) and tRNA(Ser(UCN)). We identified human Trmt61B, which encodes a mitochondria-specific tRNA methyltransferase responsible for m¹A58 in these three tRNAs. Trmt61B is dominantly localized to the mitochondria. m¹A58 formation in human mitochondrial tRNA(Leu(UUR)) could be reconstituted in vitro using recombinant Trmt61B in the presence of Ado-Met as a methyl donor. Unlike the cytoplasmic tRNA m¹A58 methyltransferase that consists of an α2β2 heterotetramer formed by Trmt61A and Trmt6, Trmt61B formed a homo-oligomer (presumably a homotetramer) that resembled the bacterial homotetrameric m¹A58 methyltransferase. The bacterial origin of Trmt61B is supported by the results of the phylogenetic analysis.
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Affiliation(s)
- Takeshi Chujo
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Tsutomu Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Corresponding authorE-mail
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56
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Towns WL, Begley TJ. Transfer RNA methytransferases and their corresponding modifications in budding yeast and humans: activities, predications, and potential roles in human health. DNA Cell Biol 2012; 31:434-54. [PMID: 22191691 PMCID: PMC3322404 DOI: 10.1089/dna.2011.1437] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 11/07/2011] [Accepted: 11/11/2011] [Indexed: 12/13/2022] Open
Abstract
Throughout the kingdoms of life, transfer RNA (tRNA) undergoes over 100 enzyme-catalyzed, methyl-based modifications. Although a majority of the methylations are conserved from bacteria to mammals, the functions of a number of these modifications are unknown. Many of the proteins responsible for tRNA methylation, named tRNA methyltransferases (Trms), have been characterized in Saccharomyces cerevisiae. In contrast, only a few human Trms have been characterized. A BLAST search for human homologs of each S. cerevisiae Trm revealed a total of 34 human proteins matching our search criteria for an S. cerevisiae Trm homolog candidate. We have compiled a database cataloging basic information about each human and yeast Trm. Every S. cerevisiae Trm has at least one human homolog, while several Trms have multiple candidates. A search of cancer cell versus normal cell mRNA expression studies submitted to Oncomine found that 30 of the homolog genes display a significant change in mRNA expression levels in at least one data set. While 6 of the 34 human homolog candidates have confirmed tRNA methylation activity, the other candidates remain uncharacterized. We believe that our database will serve as a resource for investigating the role of human Trms in cellular stress signaling.
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Affiliation(s)
- William L. Towns
- College of Nanoscale Science and Engineering, University at Albany, Albany, New York
| | - Thomas J. Begley
- College of Nanoscale Science and Engineering, University at Albany, Albany, New York
- RNA Institute, University at Albany, Rensselaer, New York
- Cancer Research Center, University at Albany, Rensselaer, New York
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57
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Graille M, Figaro S, Kervestin S, Buckingham RH, Liger D, Heurgué-Hamard V. Methylation of class I translation termination factors: structural and functional aspects. Biochimie 2012; 94:1533-43. [PMID: 22266024 DOI: 10.1016/j.biochi.2012.01.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 01/07/2012] [Indexed: 12/23/2022]
Abstract
During protein synthesis, release of polypeptide from the ribosome occurs when an in frame termination codon is encountered. Contrary to sense codons, which are decoded by tRNAs, stop codons present in the A-site are recognized by proteins named class I release factors, leading to the release of newly synthesized proteins. Structures of these factors bound to termination ribosomal complexes have recently been obtained, and lead to a better understanding of stop codon recognition and its coordination with peptidyl-tRNA hydrolysis in bacteria. Release factors contain a universally conserved GGQ motif which interacts with the peptidyl-transferase centre to allow peptide release. The Gln side chain from this motif is methylated, a feature conserved from bacteria to man, suggesting an important biological role. However, methylation is catalysed by completely unrelated enzymes. The function of this motif and its post-translational modification will be discussed in the context of recent structural and functional studies.
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Affiliation(s)
- Marc Graille
- IBBMC, Université Paris-Sud 11, CNRS UMR8619, Orsay Cedex, F-91405, France.
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58
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Suzuki T, Nagao A, Suzuki T. Human Mitochondrial tRNAs: Biogenesis, Function, Structural Aspects, and Diseases. Annu Rev Genet 2011; 45:299-329. [DOI: 10.1146/annurev-genet-110410-132531] [Citation(s) in RCA: 413] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
Abstract
Mitochondria are eukaryotic organelles that generate most of the energy in the cell by oxidative phosphorylation (OXPHOS). Each mitochondrion contains multiple copies of a closed circular double-stranded DNA genome (mtDNA). Human (mammalian) mtDNA encodes 13 essential subunits of the inner membrane complex responsible for OXPHOS. These mRNAs are translated by the mitochondrial protein synthesis machinery, which uses the 22 species of mitochondrial tRNAs (mt tRNAs) encoded by mtDNA. The unique structural features of mt tRNAs distinguish them from cytoplasmic tRNAs bearing the canonical cloverleaf structure. The genes encoding mt tRNAs are highly susceptible to point mutations, which are a primary cause of mitochondrial dysfunction and are associated with a wide range of pathologies. A large number of nuclear factors involved in the biogenesis and function of mt tRNAs have been identified and characterized, including processing endonucleases, tRNA-modifying enzymes, and aminoacyl-tRNA synthetases. These nuclear factors are also targets of pathogenic mutations linked to various diseases, indicating the functional importance of mt tRNAs for mitochondrial activity.
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Affiliation(s)
| | - Asuteka Nagao
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo 113-8656, Japan
| | - Takeo Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo 113-8656, Japan
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59
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Qiu X, Huang K, Ma J, Gao Y. Crystallization and preliminary X-ray diffraction crystallographic study of tRNA m(1)A58 methyltransferase from Saccharomyces cerevisiae. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:1448-50. [PMID: 22102254 PMCID: PMC3212473 DOI: 10.1107/s174430911103733x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 09/13/2011] [Indexed: 11/11/2022]
Abstract
In Saccharomyces cerevisiae, TRM6 and TRM61 compose a tRNA methyltransferase which catalyzes the methylation of the N1 of adenine at position 58 in tRNAs, especially initiator methionine tRNA. TRM61 is the subunit that binds S-adenosyl-L-methionine and both subunits contribute to target tRNA binding. In order to elucidate the catalytic mechanism of TRM6-TRM61 and the mode of interaction between the two subunits, expression, purification, crystallization and X-ray diffraction analysis of the TRM6-TRM61 complex were performed in this study. The crystals diffracted to 2.80 Å resolution and belonged to the trigonal space group P3(1)21 or P3(2)21, with unit-cell parameters a = b = 139.14, c = 101.62 Å.
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Affiliation(s)
- Xiaoting Qiu
- Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China
| | - Kai Huang
- Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China
| | - Jinming Ma
- Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China
| | - Yongxiang Gao
- Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230026, People’s Republic of China
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60
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van Hoof A, Wagner EJ. A brief survey of mRNA surveillance. Trends Biochem Sci 2011; 36:585-92. [PMID: 21903397 DOI: 10.1016/j.tibs.2011.07.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 07/21/2011] [Accepted: 07/25/2011] [Indexed: 11/19/2022]
Abstract
Defective mRNAs are degraded more rapidly than normal mRNAs in a process called mRNA surveillance. Eukaryotic cells use a variety of mechanisms to detect aberrations in mRNAs and a variety of enzymes to preferentially degrade them. Recent advances in the field of RNA surveillance have provided new information regarding how cells determine which mRNA species should be subject to destruction and novel mechanisms by which a cell tags an mRNA once such a decision has been reached. In this review, we highlight recent progress in our understanding of these processes.
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Affiliation(s)
- Ambro van Hoof
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, 6431 Fannin Street, Houston, TX 77030, USA.
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61
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Awai T, Ochi A, Ihsanawati, Sengoku T, Hirata A, Bessho Y, Yokoyama S, Hori H. Substrate tRNA recognition mechanism of a multisite-specific tRNA methyltransferase, Aquifex aeolicus Trm1, based on the X-ray crystal structure. J Biol Chem 2011; 286:35236-46. [PMID: 21844194 DOI: 10.1074/jbc.m111.253641] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Archaeal and eukaryotic tRNA (N(2),N(2)-guanine)-dimethyltransferase (Trm1) produces N(2),N(2)-dimethylguanine at position 26 in tRNA. In contrast, Trm1 from Aquifex aeolicus, a hyper-thermophilic eubacterium, modifies G27 as well as G26. Here, a gel mobility shift assay revealed that the T-arm in tRNA is the binding site of A. aeolicus Trm1. To address the multisite specificity, we performed an x-ray crystal structure study. The overall structure of A. aeolicus Trm1 is similar to that of archaeal Trm1, although there is a zinc-cysteine cluster in the C-terminal domain of A. aeolicus Trm1. The N-terminal domain is a typical catalytic domain of S-adenosyl-l-methionine-dependent methyltransferases. On the basis of the crystal structure and amino acid sequence alignment, we prepared 30 mutant Trm1 proteins. These mutant proteins clarified residues important for S-adenosyl-l-methionine binding and enabled us to propose a hypothetical reaction mechanism. Furthermore, the tRNA-binding site was also elucidated by methyl transfer assay and gel mobility shift assay. The electrostatic potential surface models of A. aeolicus and archaeal Trm1 proteins demonstrated that the distribution of positive charges differs between the two proteins. We constructed a tRNA-docking model, in which the T-arm structure was placed onto the large area of positive charge, which is the expected tRNA-binding site, of A. aeolicus Trm1. In this model, the target G26 base can be placed near the catalytic pocket; however, the nucleotide at position 27 gains closer access to the pocket. Thus, this docking model introduces a rational explanation of the multisite specificity of A. aeolicus Trm1.
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Affiliation(s)
- Takako Awai
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan
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62
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Kobitski A, Hengesbach M, Seidu-Larry S, Dammertz K, Chow C, van Aerschot A, Nienhaus GU, Helm M. Single-Molecule FRET Reveals a Cooperative Effect of Two Methyl Group Modifications in the Folding of Human Mitochondrial tRNALys. ACTA ACUST UNITED AC 2011; 18:928-36. [DOI: 10.1016/j.chembiol.2011.03.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 03/14/2011] [Accepted: 03/29/2011] [Indexed: 10/17/2022]
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63
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Lahoud G, Goto-Ito S, Yoshida KI, Ito T, Yokoyama S, Hou YM. Differentiating analogous tRNA methyltransferases by fragments of the methyl donor. RNA (NEW YORK, N.Y.) 2011; 17:1236-1246. [PMID: 21602303 PMCID: PMC3138561 DOI: 10.1261/rna.2706011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 04/15/2011] [Indexed: 05/30/2023]
Abstract
Bacterial TrmD and eukaryotic-archaeal Trm5 form a pair of analogous tRNA methyltransferase that catalyze methyl transfer from S-adenosyl methionine (AdoMet) to N(1) of G37, using catalytic motifs that share no sequence or structural homology. Here we show that natural and synthetic analogs of AdoMet are unable to distinguish TrmD from Trm5. Instead, fragments of AdoMet, adenosine and methionine, are selectively inhibitory of TrmD rather than Trm5. Detailed structural information of the two enzymes in complex with adenosine reveals how Trm5 escapes targeting by adopting an altered structure, whereas TrmD is trapped by targeting due to its rigid structure that stably accommodates the fragment. Free energy analysis exposes energetic disparities between the two enzymes in how they approach the binding of AdoMet versus fragments and provides insights into the design of inhibitors selective for TrmD.
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Affiliation(s)
- Georges Lahoud
- Thomas Jefferson University, Department of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107, USA
| | - Sakurako Goto-Ito
- RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
- Department of Biophysics and Biochemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ken-ichi Yoshida
- RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
- Department of Biophysics and Biochemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takuhiro Ito
- RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
| | - Shigeyuki Yokoyama
- RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa 230-0045, Japan
- Department of Biophysics and Biochemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ya-Ming Hou
- Thomas Jefferson University, Department of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107, USA
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64
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Liger D, Mora L, Lazar N, Figaro S, Henri J, Scrima N, Buckingham RH, van Tilbeurgh H, Heurgué-Hamard V, Graille M. Mechanism of activation of methyltransferases involved in translation by the Trm112 'hub' protein. Nucleic Acids Res 2011; 39:6249-59. [PMID: 21478168 PMCID: PMC3152332 DOI: 10.1093/nar/gkr176] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Methylation is a common modification encountered in DNA, RNA and proteins. It plays a central role in gene expression, protein function and mRNA translation. Prokaryotic and eukaryotic class I translation termination factors are methylated on the glutamine of the essential and universally conserved GGQ motif, in line with an important cellular role. In eukaryotes, this modification is performed by the Mtq2-Trm112 holoenzyme. Trm112 activates not only the Mtq2 catalytic subunit but also two other tRNA methyltransferases (Trm9 and Trm11). To understand the molecular mechanisms underlying methyltransferase activation by Trm112, we have determined the 3D structure of the Mtq2-Trm112 complex and mapped its active site. Using site-directed mutagenesis and in vivo functional experiments, we show that this structure can also serve as a model for the Trm9-Trm112 complex, supporting our hypothesis that Trm112 uses a common strategy to activate these three methyltransferases.
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Affiliation(s)
- Dominique Liger
- Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Université Paris-Sud, IFR115, CNRS UMR 8619, Orsay Cedex F-91405, France
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65
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Brooks MA, Gewartowski K, Mitsiki E, Létoquart J, Pache RA, Billier Y, Bertero M, Corréa M, Czarnocki-Cieciura M, Dadlez M, Henriot V, Lazar N, Delbos L, Lebert D, Piwowarski J, Rochaix P, Böttcher B, Serrano L, Séraphin B, van Tilbeurgh H, Aloy P, Perrakis A, Dziembowski A. Systematic bioinformatics and experimental validation of yeast complexes reduces the rate of attrition during structural investigations. Structure 2011; 18:1075-82. [PMID: 20826334 DOI: 10.1016/j.str.2010.08.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2010] [Revised: 06/30/2010] [Accepted: 08/07/2010] [Indexed: 10/19/2022]
Abstract
For high-throughput structural studies of protein complexes of composition inferred from proteomics data, it is crucial that candidate complexes are selected accurately. Herein, we exemplify a procedure that combines a bioinformatics tool for complex selection with in vivo validation, to deliver structural results in a medium-throughout manner. We have selected a set of 20 yeast complexes, which were predicted to be feasible by either an automated bioinformatics algorithm, by manual inspection of primary data, or by literature searches. These complexes were validated with two straightforward and efficient biochemical assays, and heterologous expression technologies of complex components were then used to produce the complexes to assess their feasibility experimentally. Approximately one-half of the selected complexes were useful for structural studies, and we detail one particular success story. Our results underscore the importance of accurate target selection and validation in avoiding transient, unstable, or simply nonexistent complexes from the outset.
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Affiliation(s)
- Mark A Brooks
- IBBMC-CNRS UMR8619, IFR 115, Bât. 430, Université Paris-Sud, 91405 Orsay, France
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66
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Abstract
tRNA biology has come of age, revealing an unprecedented level of understanding and many unexpected discoveries along the way. This review highlights new findings on the diverse pathways of tRNA maturation, and on the formation and function of a number of modifications. Topics of special focus include the regulation of tRNA biosynthesis, quality control tRNA turnover mechanisms, widespread tRNA cleavage pathways activated in response to stress and other growth conditions, emerging evidence of signaling pathways involving tRNA and cleavage fragments, and the sophisticated intracellular tRNA trafficking that occurs during and after biosynthesis.
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Affiliation(s)
- Eric M Phizicky
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York 14642, USA.
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67
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Saikia M, Fu Y, Pavon-Eternod M, He C, Pan T. Genome-wide analysis of N1-methyl-adenosine modification in human tRNAs. RNA (NEW YORK, N.Y.) 2010; 16:1317-27. [PMID: 20484468 PMCID: PMC2885681 DOI: 10.1261/rna.2057810] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 04/14/2010] [Indexed: 05/19/2023]
Abstract
The N(1)-methyl-Adenosine (m(1)A58) modification at the conserved nucleotide 58 in the TPsiC loop is present in most eukaryotic tRNAs. In yeast, m(1)A58 modification is essential for viability because it is required for the stability of the initiator-tRNA(Met). However, m(1)A58 modification is not required for the stability of several other tRNAs in yeast. This differential m(1)A58 response for different tRNA species raises the question of whether some tRNAs are hypomodified at A58 in normal cells, and how hypomodification at A58 may affect the stability and function of tRNA. Here, we apply a genomic approach to determine the presence of m(1)A58 hypomodified tRNAs in human cell lines and show how A58 hypomodification affects stability and involvement of tRNAs in translation. Our microarray-based method detects the presence of m(1)A58 hypomodified tRNA species on the basis of their permissiveness in primer extension. Among five human cell lines examined, approximately one-quarter of all tRNA species are hypomodified in varying amounts, and the pattern of the hypomodified tRNAs is quite similar. In all cases, no hypomodified initiator-tRNA(Met) is detected, consistent with the requirement of this modification in stabilizing this tRNA in human cells. siRNA knockdown of either subunit of the m(1)A58-methyltransferase results in a slow-growth phenotype, and a marked increase in the amount of m(1)A58 hypomodified tRNAs. Most m(1)A58 hypomodified tRNAs can associate with polysomes in varying extents. Our results show a distinct pattern for m(1)A58 hypomodification in human tRNAs, and are consistent with the notion that this modification fine tunes tRNA functions in different contexts.
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Affiliation(s)
- Mridusmita Saikia
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, USA
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68
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Han TX, Xu XY, Zhang MJ, Peng X, Du LL. Global fitness profiling of fission yeast deletion strains by barcode sequencing. Genome Biol 2010; 11:R60. [PMID: 20537132 PMCID: PMC2911108 DOI: 10.1186/gb-2010-11-6-r60] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Revised: 05/14/2010] [Accepted: 06/10/2010] [Indexed: 12/25/2022] Open
Abstract
A genome-wide deletion library is a powerful tool for probing gene functions and one has recently become available for the fission yeast Schizosaccharomyces pombe. Here we use deep sequencing to accurately characterize the barcode sequences in the deletion library, thus enabling the quantitative measurement of the fitness of fission yeast deletion strains by barcode sequencing.
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Affiliation(s)
- Tian Xu Han
- National Institute of Biological Sciences, 7 Science Park Road, Zhongguancun Life Science Park, Beijing, 102206, PR China
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69
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Guelorget A, Roovers M, Guérineau V, Barbey C, Li X, Golinelli-Pimpaneau B. Insights into the hyperthermostability and unusual region-specificity of archaeal Pyrococcus abyssi tRNA m1A57/58 methyltransferase. Nucleic Acids Res 2010; 38:6206-18. [PMID: 20483913 PMCID: PMC2952851 DOI: 10.1093/nar/gkq381] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The S-adenosyl-L-methionine dependent methylation of adenine 58 in the T-loop of tRNAs is essential for cell growth in yeast or for adaptation to high temperatures in thermophilic organisms. In contrast to bacterial and eukaryotic tRNA m(1)A58 methyltransferases that are site-specific, the homologous archaeal enzyme from Pyrococcus abyssi catalyzes the formation of m(1)A also at the adjacent position 57, m(1)A57 being a precursor of 1-methylinosine. We report here the crystal structure of P. abyssi tRNA m(1)A57/58 methyltransferase ((Pab)TrmI), in complex with S-adenosyl-L-methionine or S-adenosyl-L-homocysteine in three different space groups. The fold of the monomer and the tetrameric architecture are similar to those of the bacterial enzymes. However, the inter-monomer contacts exhibit unique features. In particular, four disulfide bonds contribute to the hyperthermostability of the archaeal enzyme since their mutation lowers the melting temperature by 16.5°C. His78 in conserved motif X, which is present only in TrmIs from the Thermococcocales order, lies near the active site and displays two alternative conformations. Mutagenesis indicates His78 is important for catalytic efficiency of (Pab)TrmI. When A59 is absent in tRNA(Asp), only A57 is modified. Identification of the methylated positions in tRNAAsp by mass spectrometry confirms that (Pab)TrmI methylates the first adenine of an AA sequence.
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Affiliation(s)
- Amandine Guelorget
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette, France
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70
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Tomikawa C, Yokogawa T, Kanai T, Hori H. N7-Methylguanine at position 46 (m7G46) in tRNA from Thermus thermophilus is required for cell viability at high temperatures through a tRNA modification network. Nucleic Acids Res 2010; 38:942-57. [PMID: 19934251 PMCID: PMC2817472 DOI: 10.1093/nar/gkp1059] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 10/24/2009] [Accepted: 10/26/2009] [Indexed: 02/06/2023] Open
Abstract
N(7)-methylguanine at position 46 (m(7)G46) in tRNA is produced by tRNA (m(7)G46) methyltransferase (TrmB). To clarify the role of this modification, we made a trmB gene disruptant (DeltatrmB) of Thermus thermophilus, an extreme thermophilic eubacterium. The absence of TrmB activity in cell extract from the DeltatrmB strain and the lack of the m(7)G46 modification in tRNA(Phe) were confirmed by enzyme assay, nucleoside analysis and RNA sequencing. When the DeltatrmB strain was cultured at high temperatures, several modified nucleotides in tRNA were hypo-modified in addition to the lack of the m(7)G46 modification. Assays with tRNA modification enzymes revealed hypo-modifications of Gm18 and m(1)G37, suggesting that the m(7)G46 positively affects their formations. Although the lack of the m(7)G46 modification and the hypo-modifications do not affect the Phe charging activity of tRNA(Phe), they cause a decrease in melting temperature of class I tRNA and degradation of tRNA(Phe) and tRNA(Ile). (35)S-Met incorporation into proteins revealed that protein synthesis in DeltatrmB cells is depressed above 70 degrees C. At 80 degrees C, the DeltatrmB strain exhibits a severe growth defect. Thus, the m(7)G46 modification is required for cell viability at high temperatures via a tRNA modification network, in which the m(7)G46 modification supports introduction of other modifications.
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Affiliation(s)
- Chie Tomikawa
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Department of Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido 1-1, Gifu, Gifu 501-1193, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, Kyoto 615-8510, Venture Business Laboratory, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577 and RIKEN SPring-8 Center, Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyougo 679-5148, Japan
| | - Takashi Yokogawa
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Department of Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido 1-1, Gifu, Gifu 501-1193, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, Kyoto 615-8510, Venture Business Laboratory, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577 and RIKEN SPring-8 Center, Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyougo 679-5148, Japan
| | - Tamotsu Kanai
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Department of Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido 1-1, Gifu, Gifu 501-1193, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, Kyoto 615-8510, Venture Business Laboratory, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577 and RIKEN SPring-8 Center, Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyougo 679-5148, Japan
| | - Hiroyuki Hori
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Department of Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido 1-1, Gifu, Gifu 501-1193, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, Kyoto 615-8510, Venture Business Laboratory, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577 and RIKEN SPring-8 Center, Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyougo 679-5148, Japan
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71
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Phizicky EM, Alfonzo JD. Do all modifications benefit all tRNAs? FEBS Lett 2009; 584:265-71. [PMID: 19931536 DOI: 10.1016/j.febslet.2009.11.049] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 11/12/2009] [Accepted: 11/13/2009] [Indexed: 10/20/2022]
Abstract
Despite the universality of tRNA modifications, some tRNAs lacking specific modifications are subject to degradation pathways, while other tRNAs lacking the same modifications are resistant. Here, we suggest a model in which some modifications have minor, possibly redundant, roles in specific tRNAs. This model is consistent with the low specificity of some modification enzymes. Limitations of this model include the limited assays and growth conditions on which these conclusions are based, as well as the high specificity exhibited by many modification enzymes with important roles in translation. The specificity of these enzymes is often enhanced by complex substrate recognition patterns and sub-cellular compartmentalization.
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Affiliation(s)
- Eric M Phizicky
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, NY 14642, USA.
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72
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Kolitz SE, Lorsch JR. Eukaryotic initiator tRNA: finely tuned and ready for action. FEBS Lett 2009; 584:396-404. [PMID: 19925799 DOI: 10.1016/j.febslet.2009.11.047] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 11/11/2009] [Accepted: 11/12/2009] [Indexed: 12/17/2022]
Abstract
The initiator tRNA must serve functions distinct from those of other tRNAs, evading binding to elongation factors and instead binding directly to the ribosomal P site with the aid of initiation factors. It plays a key role in decoding the start codon, setting the frame for translation of the mRNA. Sequence elements and modifications of the initiator tRNA distinguish it from the elongator methionyl tRNA and help it to perform its varied tasks. These identity elements appear to finely tune the structure of the initiator tRNA, and growing evidence suggests that the body of the tRNA is involved in transmitting the signal that the start codon has been found to the rest of the pre-initiation complex.
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Affiliation(s)
- Sarah E Kolitz
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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73
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Anderson JT, Wang X. Nuclear RNA surveillance: no sign of substrates tailing off. Crit Rev Biochem Mol Biol 2009; 44:16-24. [PMID: 19280429 DOI: 10.1080/10409230802640218] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The production of cellular RNAs is tightly regulated to ensure gene expression is limited to appropriate times and locations. Elimination of RNA can be rapid and programmed to quickly terminate gene expression, or can be used to purge old, damaged or inappropriately formed RNAs. It is elimination of RNAs through the action of a polyadenylation complex (TRAMP), first described in the yeast Saccharomyces cerevisiae, which is the focus of this review. The discovery of TRAMP and presence of orthologs in most eukaryotes, along with an increasing number of potential TRAMP substrates in the form of new small non-coding RNAs, many of which emanate from areas of genomes once thought transcriptionally silent; promise to make this area of research of great interest for the foreseeable future.
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Affiliation(s)
- James T Anderson
- Department of Biological Sciences, Marquette University, Milwaukee, WI, USA.
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74
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Ozanick SG, Wang X, Costanzo M, Brost RL, Boone C, Anderson JT. Rex1p deficiency leads to accumulation of precursor initiator tRNAMet and polyadenylation of substrate RNAs in Saccharomyces cerevisiae. Nucleic Acids Res 2008; 37:298-308. [PMID: 19042972 PMCID: PMC2615624 DOI: 10.1093/nar/gkn925] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A synthetic genetic array was used to identify lethal and slow-growth phenotypes produced when a mutation in TRM6, which encodes a tRNA modification enzyme subunit, was combined with the deletion of any non-essential gene in Saccharomyces cerevisiae. We found that deletion of the REX1 gene resulted in a slow-growth phenotype in the trm6-504 strain. Previously, REX1 was shown to be involved in processing the 3′ ends of 5S rRNA and the dimeric tRNAArg-tRNAAsp. In this study, we have discovered a requirement for Rex1p in processing the 3′ end of tRNAiMet precursors and show that precursor tRNAiMet accumulates in a trm6-504 rex1Δ strain. Loss of Rex1p results in polyadenylation of its substrates, including tRNAiMet, suggesting that defects in 3′ end processing can activate the nuclear surveillance pathway. Finally, purified Rex1p displays Mg2+-dependent ribonuclease activity in vitro, and the enzyme is inactivated by mutation of two highly conserved amino acids.
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Affiliation(s)
- Sarah G Ozanick
- Department of Biological Sciences, Marquette University, Milwaukee, WI, USA
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75
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Studte P, Zink S, Jablonowski D, Bär C, von der Haar T, Tuite MF, Schaffrath R. tRNA and protein methylase complexes mediate zymocin toxicity in yeast. Mol Microbiol 2008; 69:1266-77. [PMID: 18657261 DOI: 10.1111/j.1365-2958.2008.06358.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Modification of Saccharomyces cerevisiae tRNA anticodons at the wobble uridine (U34) position is required for tRNA cleavage by the zymocin tRNase killer toxin from Kluyveromyces lactis. Hence, U34 modification defects including lack of the U34 tRNA methyltransferase Trm9 protect against tRNA cleavage and zymocin. Using zymocin as a tool, we have identified toxin-resistant mutations in TRM9 that are likely to affect the U34 methylation reaction. Most strikingly, C-terminal truncations in Trm9 abolish interaction with Trm112, a protein shown to individually purify with Lys9 and two more methylases, Trm11 and Mtq2. Downregulation of a GAL1-TRM112 allele protects against zymocin whereas LYS9, TRM11 and MTQ2 are dosage suppressors of zymocin. Based on immune precipitation studies, the latter scenario correlates with competition for Trm112 and in excess, some of these Trm112 partners interfere with formation of the toxin-relevant Trm9.Trm112 complex. In contrast to trm11Delta or lys9Delta cells, trm112Delta and mtq2Delta null mutants are zymocin resistant. In line with the identified role that methylation of Sup45 by Mtq2 has for translation termination by the release factor dimer Sup45.Sup35, we observe that SUP45 overexpression and sup45 mutants suppress zymocin. Intriguingly, this suppression correlates with upregulated levels of tRNA species targeted by zymocin's tRNase activity.
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Affiliation(s)
- Patrick Studte
- Institut für Biologie, Bereich Genetik, Martin-Luther-Universität, Halle-Wittenberg, Weinbergweg 10, D-06120 Halle (Saale), Germany
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76
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Crystal structure of Thermus thermophilus tRNA m1A58 methyltransferase and biophysical characterization of its interaction with tRNA. J Mol Biol 2008; 377:535-50. [PMID: 18262540 DOI: 10.1016/j.jmb.2008.01.041] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Revised: 01/11/2008] [Accepted: 01/16/2008] [Indexed: 11/22/2022]
Abstract
Methyltransferases from the m(1)A(58) tRNA methyltransferase (TrmI) family catalyze the S-adenosyl-l-methionine-dependent N(1)-methylation of tRNA adenosine 58. The crystal structure of Thermus thermophilus TrmI, in complex with S-adenosyl-l-homocysteine, was determined at 1.7 A resolution. This structure is closely related to that of Mycobacterium tuberculosis TrmI, and their comparison enabled us to enlighten two grooves in the TrmI structure that are large enough and electrostatically compatible to accommodate one tRNA per face of TrmI tetramer. We have then conducted a biophysical study based on electrospray ionization mass spectrometry, site-directed mutagenesis, and molecular docking. First, we confirmed the tetrameric oligomerization state of TrmI, and we showed that this protein remains tetrameric upon tRNA binding, with formation of complexes involving one to two molecules of tRNA per TrmI tetramer. Second, three key residues for the methylation reaction were identified: the universally conserved D170 and two conserved aromatic residues Y78 and Y194. We then used molecular docking to position a N(9)-methyladenine in the active site of TrmI. The N(9)-methyladenine snugly fits into the catalytic cleft, where the side chain of D170 acts as a bidentate ligand binding the amino moiety of S-adenosyl-l-methionine and the exocyclic amino group of the adenosine. Y194 interacts with the N(9)-methyladenine ring, whereas Y78 can stabilize the sugar ring. From our results, we propose that the conserved residues that form the catalytic cavity (D170, Y78, and Y194) are essential for fashioning an optimized shape of the catalytic pocket.
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77
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Kotelawala L, Grayhack EJ, Phizicky EM. Identification of yeast tRNA Um(44) 2'-O-methyltransferase (Trm44) and demonstration of a Trm44 role in sustaining levels of specific tRNA(Ser) species. RNA (NEW YORK, N.Y.) 2008; 14:158-69. [PMID: 18025252 PMCID: PMC2151035 DOI: 10.1261/rna.811008] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Accepted: 10/07/2007] [Indexed: 05/17/2023]
Abstract
A characteristic feature of tRNAs is the numerous modifications found throughout their sequences, which are highly conserved and often have important roles. Um(44) is highly conserved among eukaryotic cytoplasmic tRNAs with a long variable loop and unique to tRNA(Ser) in yeast. We show here that the yeast ORF YPL030w (now named TRM44) encodes tRNA(Ser) Um(44) 2'-O-methyltransferase. Trm44 was identified by screening a yeast genomic library of affinity purified proteins for activity and verified by showing that a trm44-delta strain lacks 2'-O-methyltransferase activity and has undetectable levels of Um(44) in its tRNA(Ser) and by showing that Trm44 purified from Escherichia coli 2'-O-methylates U(44) of tRNA(Ser) in vitro. Trm44 is conserved among metazoans and fungi, consistent with the conservation of Um(44) in eukaryotic tRNAs, but surprisingly, Trm44 is not found in plants. Although trm44-delta mutants have no detectable growth defect, TRM44 is required for survival at 33 degrees C in a tan1-delta mutant strain, which lacks ac(4)C12 in tRNA(Ser) and tRNA(Leu). At nonpermissive temperature, a trm44-delta tan1-delta mutant strain has reduced levels of tRNA(Ser(CGA)) and tRNA(Ser(UGA)), but not other tRNA(Ser) or tRNA(Leu) species. The trm44-delta tan1-delta growth defect is suppressed by addition of multiple copies of tRNA(Ser(CGA)) and tRNA(Ser(UGA)), directly implicating these tRNA(Ser) species in this phenotype. The reduction of specific tRNA(Ser) species in a trm44-delta tan1-delta mutant underscores the importance of tRNA modifications in sustaining tRNA levels and further emphasizes that tRNAs undergo quality control.
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Affiliation(s)
- Lakmal Kotelawala
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, New York 14642, USA
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78
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Bujnicki JM, Droogmans L, Grosjean H, Purushothaman SK, Lapeyre B. Bioinformatics-Guided Identification and Experimental Characterization of Novel RNA Methyltransferas. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/978-3-540-74268-5_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2023]
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79
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Structure of the Yeast tRNA m7G Methylation Complex. Structure 2008; 16:52-61. [DOI: 10.1016/j.str.2007.10.025] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2007] [Revised: 10/19/2007] [Accepted: 10/19/2007] [Indexed: 11/17/2022]
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80
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Wang X, Jia H, Jankowsky E, Anderson JT. Degradation of hypomodified tRNA(iMet) in vivo involves RNA-dependent ATPase activity of the DExH helicase Mtr4p. RNA (NEW YORK, N.Y.) 2008; 14:107-16. [PMID: 18000032 PMCID: PMC2151029 DOI: 10.1261/rna.808608] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Accepted: 09/19/2007] [Indexed: 05/11/2023]
Abstract
Effective turnover of many incorrectly processed RNAs in yeast, including hypomodified tRNA(iMet), requires the TRAMP complex, which appends a short poly(A) tail to RNA designated for decay. The poly(A) tail stimulates degradation by the exosome. The TRAMP complex contains the poly(A) polymerase Trf4p, the RNA-binding protein Air2p, and the DExH RNA helicase Mtr4p. The role of Mtr4p in RNA degradation processes involving the TRAMP complex has been unclear. Here we show through a genetic analysis that MTR4 is required for degradation but not for polyadenylation of hypomodified tRNA(iMet). A suppressor of the trm6-504 mutation in the tRNA m(1)A58 methyltransferase (Trm6p/Trm61p), which causes a reduced level of tRNA(iMet), was mapped to MTR4. This mtr4-20 mutation changed a single amino acid in the conserved helicase motif VI of Mtr4p. The mutation stabilizes hypomodified tRNA(iMet) in vivo but has no effect on TRAMP complex stability or polyadenylation activity in vivo or in vitro. We further show that purified recombinant Mtr4p displays RNA-dependent ATPase activity and unwinds RNA duplexes with a 3'-to-5' polarity in an ATP-dependent fashion. Unwinding and RNA-stimulated ATPase activities are strongly reduced in the recombinant mutant Mtr4-20p, suggesting that these activities of Mtr4p are critical for degradation of polyadenylated hypomodified tRNA(iMet).
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Affiliation(s)
- Xuying Wang
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201, USA
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81
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Ozanick SG, Bujnicki JM, Sem DS, Anderson JT. Conserved amino acids in each subunit of the heteroligomeric tRNA m1A58 Mtase from Saccharomyces cerevisiae contribute to tRNA binding. Nucleic Acids Res 2007; 35:6808-19. [PMID: 17932071 PMCID: PMC2175304 DOI: 10.1093/nar/gkm574] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
In Saccharomyces cerevisiae, a two-subunit methyltransferase (Mtase) encoded by the essential genes TRM6 and TRM61 is responsible for the formation of 1-methyladenosine, a modified nucleoside found at position 58 in tRNA that is critical for the stability of tRNA(Met)i The crystal structure of the homotetrameric m1A58 tRNA Mtase from Mycobacterium tuberculosis, TrmI, has been solved and was used as a template to build a model of the yeast m1A58 tRNA Mtase heterotetramer. We altered amino acids in TRM6 and TRM61 that were predicted to be important for the stability of the heteroligomer based on this model. Yeast strains expressing trm6 and trm61 mutants exhibited growth phenotypes indicative of reduced m1A formation. In addition, recombinant mutant enzymes had reduced in vitro Mtase activity. We demonstrate that the mutations introduced do not prevent heteroligomer formation and do not disrupt binding of the cofactor S-adenosyl-L-methionine. Instead, amino acid substitutions in either Trm6p or Trm61p destroy the ability of the yeast m1A58 tRNA Mtase to bind tRNA(Met)i, indicating that each subunit contributes to tRNA binding and suggesting a structural alteration of the substrate-binding pocket occurs when these mutations are present.
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Affiliation(s)
- Sarah G Ozanick
- Department of Biological Sciences, Marquette University, P.O. Box 1881, Milwaukee, WI 53201, USA
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82
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Schneider C, Anderson JT, Tollervey D. The exosome subunit Rrp44 plays a direct role in RNA substrate recognition. Mol Cell 2007; 27:324-331. [PMID: 17643380 PMCID: PMC7610968 DOI: 10.1016/j.molcel.2007.06.006] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 04/12/2007] [Accepted: 06/06/2007] [Indexed: 10/23/2022]
Abstract
The exosome plays key roles in RNA maturation and surveillance, but it is unclear how target RNAs are identified. We report the functional characterization of the yeast exosome component Rrp44, a member of the RNase II family. Recombinant Rrp44 and the purified TRAMP polyadenylation complex each specifically recognized tRNA(i)(Met) lacking a single m(1)A(58) modification, even in the presence of a large excess of total tRNA. This tRNA is otherwise mature and functional in translation in vivo but is presumably subtly misfolded. Complete degradation of the hypomodified tRNA required both Rrp44 and the poly(A) polymerase activity of TRAMP. The intact exosome lacking only the catalytic activity of Rrp44 failed to degrade tRNA(i)(Met), showing this to be a specific Rrp44 substrate. Recognition of hypomodified tRNA(i)(Met) by Rrp44 is genetically separable from its catalytic activity on other substrates, with the mutations mapping to distinct regions of the protein.
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Affiliation(s)
- Claudia Schneider
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK
| | - James T Anderson
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA
| | - David Tollervey
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, UK.
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83
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Walbott H, Auxilien S, Grosjean H, Golinelli-Pimpaneau B. The Carboxyl-terminal Extension of Yeast tRNA m5C Methyltransferase Enhances the Catalytic Efficiency of the Amino-terminal Domain. J Biol Chem 2007; 282:23663-71. [PMID: 17567576 DOI: 10.1074/jbc.m703818200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The human tRNA m(5)C methyltransferase is a potential target for anticancer drugs because it is a novel downstream target of the proto-oncogene myc, mediating Myc-induced cell proliferation. Sequence comparisons of RNA m(5)C methyltransferases indicate that the eukaryotic enzymes possess, in addition to a conserved catalytic domain, a large characteristic carboxyl-terminal extension. To gain insight into the function of this additional domain, the modular architecture of the yeast tRNA m(5)C methyltransferase orthologue, Trm4p, was studied. The yeast enzyme catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to carbon 5 of cytosine at different positions depending on the tRNAs. By limited proteolysis, Trm4p was shown to be composed of two domains that have been separately produced and purified. Here we demonstrate that the aminoterminal domain, encompassing the active site, binds tRNA with similar affinity as the whole enzyme but shows low catalytic efficiency. The carboxyl-terminal domain displays only weak affinity for tRNA. It is not required for m(5)C formation and does not appear to contribute to substrate specificity. However, it enhances considerably the catalytic efficiency of the amino-terminal domain.
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Affiliation(s)
- Hélène Walbott
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS Bâtiment 34, 1 Avenue de la Terrasse, 91190 Gif-sur-Yvette, France
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84
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Wolin SL, Wurtmann EJ. Molecular chaperones and quality control in noncoding RNA biogenesis. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2007; 71:505-11. [PMID: 17381333 DOI: 10.1101/sqb.2006.71.051] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Although noncoding RNAs have critical roles in all cells, both the mechanisms by which these RNAs fold into functional structures and the quality control pathways that monitor correct folding are only beginning to be elucidated. Here, we discuss several proteins that likely function as molecular chaperones for noncoding RNAs and review the existing knowledge on noncoding RNA quality control. One protein, the La protein, binds many nascent noncoding RNAs in eukaryotes and is required for efficient folding of certain pre-tRNAs. In prokaryotes, the Sm-like protein Hfq is required for the function of many noncoding RNAs. Recent work in bacteria and yeast has revealed the existence of quality control systems involving polyadenylation of unstable noncoding RNAs followed by exonucleolytic degradation. In addition, the Ro protein, which is present in many animal cells and also certain bacteria, binds misfolded noncoding RNAs and is proposed to function in RNA quality control.
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MESH Headings
- Bacteria/genetics
- Bacteria/metabolism
- Models, Molecular
- Molecular Chaperones/genetics
- Molecular Chaperones/metabolism
- Mutation
- Nucleic Acid Conformation
- RNA, Bacterial/biosynthesis
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Fungal/biosynthesis
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Untranslated/biosynthesis
- RNA, Untranslated/chemistry
- RNA, Untranslated/genetics
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- S L Wolin
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06536, USA
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85
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Timofeev E, Mikhailov S, Zuev A, Efimtseva E, Herdewijn P, Somers R, Lemaitre M. Oligodeoxynucleotides Containing 2′-Deoxy-1-methyladenosine andDimroth Rearrangement. Helv Chim Acta 2007. [DOI: 10.1002/hlca.200790093] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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86
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Jackman JE, Kotelawala L, Grayhack EJ, Phizicky EM. Identification and Characterization of Modification Enzymes by Biochemical Analysis of the Proteome. Methods Enzymol 2007; 425:139-52. [PMID: 17673082 DOI: 10.1016/s0076-6879(07)25006-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The use of proteomic libraries designed to express the complete set of proteins from an organism has resulted in the identification of many RNA modification enzymes whose function was previously unknown. Here we describe a generalized procedure for the biochemical analysis of a yeast proteomic library for identification of nucleic acid-modifying enzymes, by use of the yeast MORF (Moveable Open Reading Frame) library (Gelperin et al., 2005) as the source of protein activity, and the known yeast tRNA methyltransferase Trm4 as a test case. The procedures outlined in this chapter can be applied to any proteomic expression library from any organism, many of which will become increasingly available as the number of sequenced genomes increases and as genomic cloning techniques improve.
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Affiliation(s)
- Jane E Jackman
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, NY, USA
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87
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Alexandrov A, Chernyakov I, Gu W, Hiley SL, Hughes TR, Grayhack EJ, Phizicky EM. Rapid tRNA decay can result from lack of nonessential modifications. Mol Cell 2006; 21:87-96. [PMID: 16387656 DOI: 10.1016/j.molcel.2005.10.036] [Citation(s) in RCA: 364] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 10/18/2005] [Accepted: 10/28/2005] [Indexed: 11/19/2022]
Abstract
The biological role of many nonessential tRNA modifications outside of the anticodon remains elusive despite their evolutionary conservation. We show here that m7G46 methyltransferase Trm8p/Trm82p acts as a hub of synthetic interactions with several tRNA modification enzymes, resulting in temperature-sensitive growth. Analysis of three double mutants indicates reduced levels of tRNA(Val(AAC)), consistent with a role of the corresponding modifications in maintenance of tRNA levels. Detailed examination of a trm8-delta trm4-delta double mutant demonstrates rapid degradation of preexisting tRNA(Val(AAC)) accompanied by its de-aminoacylation. Multiple copies of tRNA(Val(AAC)) suppress the trm8-delta trm4-delta growth defect, directly implicating this tRNA in the phenotype. These results define a rapid tRNA degradation (RTD) pathway that is independent of the TRF4/RRP6-dependent nuclear surveillance pathway. The degradation of an endogenous tRNA species at a rate typical of mRNA decay demonstrates a critical role of nonessential modifications for tRNA stability and cell survival.
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Affiliation(s)
- Andrei Alexandrov
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, New York 14642, USA
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88
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Abstract
Alternative foldings are an inherent property of RNA and a ubiquitous problem in scientific investigations. To a living organism, alternative foldings can be a blessing or a problem, and so nature has found both, ways to harness this property and ways to avoid the drawbacks. A simple and effective method employed by nature to avoid unwanted folding is the modulation of conformation space through post-transcriptional base modification. Modified nucleotides occur in almost all classes of natural RNAs in great chemical diversity. There are about 100 different base modifications known, which may perform a plethora of functions. The presumably most ancient and simple nucleotide modifications, such as methylations and uridine isomerization, are able to perform structural tasks on the most basic level, namely by blocking or reinforcing single base-pairs or even single hydrogen bonds in RNA. In this paper, functional, genomic and structural evidence on cases of folding space alteration by post-transcriptional modifications in native RNA are reviewed.
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Affiliation(s)
- Mark Helm
- Department of Chemistry, Institute for Pharmacy and Molecular Biotechnology, University of Heidelberg, Im Neuenheimer Feld 364, D-69120 Heidelberg, Germany.
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89
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Abstract
Cells reprogram gene expression in response to environmental changes by mobilizing transcriptional activators. The activator protein Gcn4 of the yeast Saccharomyces cerevisiae is regulated by an intricate translational control mechanism, which is the primary focus of this review, and also by the modulation of its stability in response to nutrient availability. Translation of GCN4 mRNA is derepressed in amino acid-deprived cells, leading to transcriptional induction of nearly all genes encoding amino acid biosynthetic enzymes. The trans-acting proteins that control GCN4 translation have general functions in the initiation of protein synthesis, or regulate the activities of initiation factors, so that the molecular events that induce GCN4 translation also reduce the rate of general protein synthesis. This dual regulatory response enables cells to limit their consumption of amino acids while diverting resources into amino acid biosynthesis in nutrient-poor environments. Remarkably, mammalian cells use the same strategy to downregulate protein synthesis while inducing transcriptional activators of stress-response genes under various stressful conditions, including amino acid starvation.
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Affiliation(s)
- Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, Bethesda, Maryland 20892, USA.
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90
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Kozbial PZ, Mushegian AR. Natural history of S-adenosylmethionine-binding proteins. BMC STRUCTURAL BIOLOGY 2005; 5:19. [PMID: 16225687 PMCID: PMC1282579 DOI: 10.1186/1472-6807-5-19] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Accepted: 10/14/2005] [Indexed: 11/10/2022]
Abstract
BACKGROUND S-adenosylmethionine is a source of diverse chemical groups used in biosynthesis and modification of virtually every class of biomolecules. The most notable reaction requiring S-adenosylmethionine, transfer of methyl group, is performed by a large class of enzymes, S-adenosylmethionine-dependent methyltransferases, which have been the focus of considerable structure-function studies. Evolutionary trajectories of these enzymes, and especially of other classes of S-adenosylmethionine-binding proteins, nevertheless, remain poorly understood. We addressed this issue by computational comparison of sequences and structures of various S-adenosylmethionine-binding proteins. RESULTS Two widespread folds, Rossmann fold and TIM barrel, have been repeatedly used in evolution for diverse types of S-adenosylmethionine conversion. There were also cases of recruitment of other relatively common folds for S-adenosylmethionine binding. Several classes of proteins have unique unrelated folds, specialized for just one type of chemistry and unified by the theme of internal domain duplications. In several cases, functional divergence is evident, when evolutionarily related enzymes have changed the mode of binding and the type of chemical transformation of S-adenosylmethionine. There are also instances of functional convergence, when biochemically similar processes are performed by drastically different classes of S-adenosylmethionine-binding proteins. Comparison of remote sequence similarities and analysis of phyletic patterns suggests that the last universal common ancestor of cellular life had between 10 and 20 S-adenosylmethionine-binding proteins from at least 5 fold classes, providing for S-adenosylmethionine formation, polyamine biosynthesis, and methylation of several substrates, including nucleic acids and peptide chain release factor. CONCLUSION We have observed several novel relationships between families that were not known to be related before, and defined 15 large superfamilies of SAM-binding proteins, at least 5 of which may have been represented in the last common ancestor.
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Affiliation(s)
- Piotr Z Kozbial
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA
| | - Arcady R Mushegian
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA
- Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA
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91
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Arhin GK, Shen S, Irmer H, Ullu E, Tschudi C. Role of a 300-kilodalton nuclear complex in the maturation of Trypanosoma brucei initiator methionyl-tRNA. EUKARYOTIC CELL 2005; 3:893-9. [PMID: 15302822 PMCID: PMC500872 DOI: 10.1128/ec.3.4.893-899.2004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
tRNAs are transcribed as precursors containing 5' leader and 3' extensions that are removed by a series of posttranscriptional processing reactions to yield functional mature tRNAs. Here, we examined the maturation pathway of tRNA(Met) in Trypanosoma brucei, an early divergent unicellular eukaryote. We identified an approximately 300-kDa complex located in the nucleus of T. brucei that is required for trimming the 5' leader of initiator tRNA(Met) precursors. One of the subunits of the complex (T. brucei MT40 [TbMT40]) is a putative methyltransferase and a homolog of Saccharomyces cerevisiae Gcd14, which is essential for 1-methyladenosine modification in tRNAs. Down-regulation of TbMT40 by RNA interference resulted in the accumulation of precursor initiator tRNA(Met) containing 5' extensions but processed 3' ends. In addition, immunoprecipitations with anti-La antibodies revealed initiator tRNA(Met) molecules with 5' and 3' extensions in TbMT40-silenced cells, albeit at a much lower level. Interestingly, silencing of TbMT40, as well as of TbMT53, a second subunit of the complex, led to an increase in the levels of mature elongator tRNA(Met). Taken together, our data provide a glance at the maturation of tRNAs in parasitic protozoa and suggest that at least for initiator tRNA(Met), 3' trimming precedes 5' processing.
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Affiliation(s)
- George K Arhin
- Department of Epidemiology and Public Health, Yale University Medical School, 295 Congress Avenue, New Haven, CT 06536-0812, USA
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92
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Ozanick S, Krecic A, Andersland J, Anderson JT. The bipartite structure of the tRNA m1A58 methyltransferase from S. cerevisiae is conserved in humans. RNA (NEW YORK, N.Y.) 2005; 11:1281-90. [PMID: 16043508 PMCID: PMC1370811 DOI: 10.1261/rna.5040605] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Among all types of RNA, tRNA is unique given that it possesses the largest assortment and abundance of modified nucleosides. The methylation at N(1) of adenosine 58 is a conserved modification, occurring in bacterial, archaeal, and eukaryotic tRNAs. In the yeast Saccharomyces cerevisiae, the tRNA 1-methyladenosine 58 (m(1)A58) methyltransferase (Mtase) is a two-subunit enzyme encoded by the essential genes TRM6 (GCD10) and TRM61 (GCD14). While the significance of many tRNA modifications is poorly understood, methylation of A58 is known to be critical for maintaining the stability of initiator tRNA(Met) in yeast. Furthermore, all retroviruses utilize m(1)A58-containing tRNAs to prime reverse transcription, and it has been shown that the presence of m(1)A58 in human tRNA(3) (Lys) is needed for accurate termination of plus-strand strong-stop DNA synthesis during HIV-1 replication. In this study we have identified the human homologs of the yeast m(1)A Mtase through amino acid sequence identity and complementation of trm6 and trm61 mutant phenotypes. When coexpressed in yeast, human Trm6p and Trm61p restored the formation of m(1)A in tRNA, modifying both yeast initiator tRNA(Met) and human tRNA(3) (Lys). Stable hTrm6p/hTrm61p complexes purified from yeast maintained tRNA m(1)A Mtase activity in vitro. The human m(1)A Mtase complex also exhibited substrate specificity--modifying wild-type yeast tRNA(i) (Met) but not an A58U mutant. Therefore, the human tRNA m(1)A Mtase shares both functional and structural homology with the yeast tRNA m(1)A Mtase, possessing similar enzymatic activity as well as a conserved binary composition.
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Affiliation(s)
- Sarah Ozanick
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA
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93
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Alexandrov A, Grayhack EJ, Phizicky EM. tRNA m7G methyltransferase Trm8p/Trm82p: evidence linking activity to a growth phenotype and implicating Trm82p in maintaining levels of active Trm8p. RNA (NEW YORK, N.Y.) 2005; 11:821-30. [PMID: 15811913 PMCID: PMC1370766 DOI: 10.1261/rna.2030705] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We show that Saccharomyces cerevisiae strains lacking Trm8p/Trm82p tRNA m7G methyltransferase are temperature-sensitive in synthetic media containing glycerol. Bacterial TRM8 orthologs complement the growth defect of trm8-Delta, trm82-Delta, and trm8-Delta trm82-Delta double mutants, suggesting that bacteria employ a single subunit for Trm8p/Trm82p function. The growth phenotype of trm8 mutants correlates with lack of tRNA m7G methyltransferase activity in vitro and in vivo, based on analysis of 10 mutant alleles of trm8 and bacterial orthologs, and suggests that m7G modification is the cellular function important for growth. Initial examination of the roles of the yeast subunits shows that Trm8p has most of the functions required to effect m7G modification, and that a major role of Trm82p is to maintain cellular levels of Trm8p. Trm8p efficiently cross-links to pre-tRNAPhe in vitro in the presence or absence of Trm82p, in addition to its known residual tRNA m7G modification activity and its SAM-binding domain. Surprisingly, the levels of Trm8p, but not its mRNA, are severely reduced in a trm82-Delta strain. Although Trm8p can be produced in the absence of Trm82p by deliberate overproduction, the resulting protein is inactive, suggesting that a second role of Trm82p is to stabilize Trm8p in an active conformation.
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Affiliation(s)
- Andrei Alexandrov
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, 601 Elmwood Ave., Box 712, Rochester, NY 14642, USA
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94
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Cartlidge RA, Knebel A, Peggie M, Alexandrov A, Phizicky EM, Cohen P. The tRNA methylase METTL1 is phosphorylated and inactivated by PKB and RSK in vitro and in cells. EMBO J 2005; 24:1696-705. [PMID: 15861136 PMCID: PMC1142581 DOI: 10.1038/sj.emboj.7600648] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Accepted: 03/23/2005] [Indexed: 11/09/2022] Open
Abstract
A substrate for protein kinase B (PKB)alpha in HeLa cell extracts was identified as methyltransferase-like protein-1 (METTL1), the orthologue of trm8, which catalyses the 7-methylguanosine modification of tRNA in Saccharomyces cerevisiae. PKB and ribosomal S6 kinase (RSK) both phosphorylated METTL1 at Ser27 in vitro. Ser27 became phosphorylated when HEK293 cells were stimulated with insulin-like growth factor-1 (IGF-1) and this was prevented by inhibition of phosphatidyinositol 3-kinase. The IGF-1-induced Ser27 phosphorylation did not occur in 3-phosphoinositide-dependent protein kinase-1 (PDK1)-deficient embryonic stem cells, but occurred normally in PDK1[L155E] cells, indicating that the effect of IGF-1 is mediated by PKB. METTL1 also became phosphorylated at Ser27 in response to phorbol-12-myristate 13-acetate and this was prevented by PD 184352 or pharmacological inhibition of RSK. Phosphorylation of METTL1 by PKB or RSK inactivated METTL1 in vitro, as did mutation of Ser27 to Asp or Glu. Expression of METTL1[S27D] or METTL1[S27E] did not rescue the growth phenotype of yeast lacking trm8. In contrast, expression of METTL1 or METTL1[S27A] partially rescued growth. These results demonstrate that METTL1 is inactivated by PKB and RSK in cells, and the potential implications of this finding are discussed.
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Affiliation(s)
- Robert A Cartlidge
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
| | - Axel Knebel
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
| | - Mark Peggie
- Division of Signal Transduction Therapy, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
| | - Andrei Alexandrov
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, NY, USA
| | - Eric M Phizicky
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, NY, USA
| | - Philip Cohen
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
- Division of Signal Transduction Therapy, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dow Street, Dundee DD1 5EH, UK. Tel.: +44 1382 344238; Fax: 44 1382 223778; E-mail:
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95
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Huang B, Johansson MJO, Byström AS. An early step in wobble uridine tRNA modification requires the Elongator complex. RNA (NEW YORK, N.Y.) 2005; 11:424-36. [PMID: 15769872 PMCID: PMC1370732 DOI: 10.1261/rna.7247705] [Citation(s) in RCA: 346] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Accepted: 01/06/2005] [Indexed: 05/17/2023]
Abstract
Elongator has been reported to be a histone acetyltransferase complex involved in elongation of RNA polymerase II transcription. In Saccharomyces cerevisiae, mutations in any of the six Elongator protein subunit (ELP1-ELP6) genes or the three killer toxin insensitivity (KTI11-KTI13) genes cause similar pleiotropic phenotypes. By analyzing modified nucleosides in individual tRNA species, we show that the ELP1-ELP6 and KTI11-KTI13 genes are all required for an early step in synthesis of 5-methoxycarbonylmethyl (mcm5) and 5-carbamoylmethyl (ncm5) groups present on uridines at the wobble position in tRNA. Transfer RNA immunoprecipitation experiments showed that the Elp1 and Elp3 proteins specifically coprecipitate a tRNA susceptible to formation of an mcm5 side chain, indicating a direct role of Elongator in tRNA modification. The presence of mcm5U, ncm5U, or derivatives thereof at the wobble position is required for accurate and efficient translation, suggesting that the phenotypes of elp1-elp6 and kti11-kti13 mutants could be caused by a translational defect. Accordingly, a deletion of any ELP1-ELP6 or KTI11-KTI13 gene prevents an ochre suppressor tRNA that normally contains mcm5U from reading ochre stop codons.
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Affiliation(s)
- Bo Huang
- Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden
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96
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Transfer RNA modifications and modifying enzymes in Saccharomyces cerevisiae. FINE-TUNING OF RNA FUNCTIONS BY MODIFICATION AND EDITING 2005. [DOI: 10.1007/b105814] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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97
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Crausaz Esseiva A, Maréchal-Drouard L, Cosset A, Schneider A. The T-stem determines the cytosolic or mitochondrial localization of trypanosomal tRNAsMet. Mol Biol Cell 2004; 15:2750-7. [PMID: 15064351 PMCID: PMC420099 DOI: 10.1091/mbc.e03-11-0821] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The mitochondrion of Trypanosoma brucei lacks tRNA genes. Organellar translation therefore depends on import of cytosolic, nucleus-encoded tRNAs. Except for the cytosol-specific initiator tRNA(Met), all trypanosomal tRNAs function in both the cytosol and the mitochondrion. The initiator tRNA(Met) is closely related to the imported elongator tRNA(Met). Thus, the distinct localization of the two tRNAs(Met) must be specified by the 26 nucleotides, which differ between the two molecules. Using transgenic T. brucei cell lines and subsequent cell fractionation, we show that the T-stem is both required and sufficient to specify the localization of the tRNAs(Met). Furthermore, it was shown that the tRNA(Met) T-stem localization determinants are also functional in the context of two other tRNAs. In vivo analysis of the modified nucleotides found in the initiator tRNA(Met) indicates that the T-stem localization determinants do not require modified nucleotides. In contrast, import of native tRNAs(Met) into isolated mitochondria suggests that nucleotide modifications might be involved in regulating the extent of import of elongator tRNA(Met).
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Affiliation(s)
- Anne Crausaz Esseiva
- Department of Biology/Zoology, University of Fribourg, CH-1700 Fribourg, Switzerland
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98
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Johansson MJO, Byström AS. The Saccharomyces cerevisiae TAN1 gene is required for N4-acetylcytidine formation in tRNA. RNA (NEW YORK, N.Y.) 2004; 10:712-9. [PMID: 15037780 PMCID: PMC1370561 DOI: 10.1261/rna.5198204] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The biogenesis of transfer RNA is a process that requires many different factors. In this study, we describe a genetic screen aimed to identify gene products participating in this process. By screening for mutations lethal in combination with a sup61-T47:2C allele, coding for a mutant form of, the nonessential TAN1 gene was identified. We show that the TAN1 gene product is required for formation of the modified nucleoside N(4)-acetylcytidine (ac(4)C) in tRNA. In Saccharomyces cerevisiae, ac(4)C is present at position 12 in tRNAs specific for leucine and serine as well as in 18S ribosomal RNA. Analysis of RNA isolated from a tan1-null mutant revealed that ac(4)C was absent in tRNA, but not rRNA. Although no tRNA acetyltransferase activity by a GST-Tan1 fusion protein was detected, a gel-shift assay revealed that Tan1p binds tRNA, suggesting a direct role in synthesis of ac(4)C(12). The absence of the TAN1 gene in the sup61-T47:2C mutant caused a decreased level of mature, indicating that ac(4)C(12) and/or Tan1p is important for tRNA stability.
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99
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Varshney U, Ramesh V, Madabushi A, Gaur R, Subramanya HS, RajBhandary UL. Mycobacterium tuberculosis Rv2118c codes for a single-component homotetrameric m1A58 tRNA methyltransferase. Nucleic Acids Res 2004; 32:1018-27. [PMID: 14960715 PMCID: PMC373377 DOI: 10.1093/nar/gkh207] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Modified nucleosides in tRNAs play important roles in tRNA structure, biosynthesis and function, and serve as crucial determinants of bacterial growth and virulence. In the yeast Saccharomyces cerevisiae, mutants defective in N1-methylation of a highly conserved adenosine (A58) in the TPsiC loop of initiator tRNA are non-viable. The yeast m1A58 methyltransferase is a heterotetramer consisting of two different polypeptide chains, Gcd14p and Gcd10p. Interestingly, while m1A58 is not found in most eubacteria, the mycobacterial tRNAs have m1A58. Here, we report on the cloning, overexpression, purification and biochemical characterization of the Rv2118c gene-encoded protein (Rv2118p) from Mycobacterium tuberculosis, which is homologous to yeast Gcd14p. We show that Rv2118c codes for a protein of approximately 31 kDa. Activity assays, modified base analysis and primer extension experiments using reverse transcriptase reveal that Rv2118p is an S-adenosyl-l-methionine-dependent methyltransferase which carries out m1A58 modification in tRNAs, both in vivo and in vitro. Remarkably, when expressed in Escherichia coli, the enzyme methylates the endogenous E.coli initiator tRNA essentially quantitatively. Furthermore, unlike its eukaryotic counterpart, which is a heterotetramer, the mycobacterial enzyme is a homotetramer. Also, the presence of rT modification at position 54, which was found to inhibit the Tetrahymena pyriformis enzyme, does not affect the activity of Rv2118p. Thus, the mycobacterial m1A58 tRNA methyltransferase possesses distinct biochemical properties. We discuss aspects of the biological relevance of Rv2118p in M.tuberculosis, and its potential use as a drug target to control the growth of mycobacteria.
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Affiliation(s)
- U Varshney
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India
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Roovers M, Wouters J, Bujnicki JM, Tricot C, Stalon V, Grosjean H, Droogmans L. A primordial RNA modification enzyme: the case of tRNA (m1A) methyltransferase. Nucleic Acids Res 2004; 32:465-76. [PMID: 14739239 PMCID: PMC373318 DOI: 10.1093/nar/gkh191] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Revised: 12/04/2003] [Accepted: 12/04/2003] [Indexed: 01/22/2023] Open
Abstract
The modified nucleoside 1-methyladenosine (m(1)A) is found in the T-loop of many tRNAs from organisms belonging to the three domains of life (Eukaryota, Bacteria, Archaea). In the T-loop of eukaryotic and bacterial tRNAs, m(1)A is present at position 58, whereas in archaeal tRNAs it is present at position(s) 58 and/or 57, m(1)A57 being the obligatory intermediate in the biosynthesis of 1-methylinosine (m(1)I57). In yeast, the formation of m(1)A58 is catalysed by the essential tRNA (m(1)A58) methyltransferase (MTase), a tetrameric enzyme that is composed of two types of subunits (Gcd14p and Gcd10p), whereas in the bacterium Thermus thermophilus the enzyme is a homotetramer of the TrmI polypeptide. Here, we report that the TrmI enzyme from the archaeon Pyrococcus abyssi is also a homotetramer. However, unlike the bacterial site-specific TrmI MTase, the P.abyssi enzyme is region-specific and catalyses the formation of m(1)A at two adjacent positions (57 and 58) in the T-loop of certain tRNAs. The stabilisation of P.abyssi TrmI at extreme temperatures involves intersubunit disulphide bridges that reinforce the tetrameric oligomerisation, as revealed by biochemical and crystallographic evidences. The origin and evolution of m(1)A MTases is discussed in the context of different hypotheses of the tree of life.
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Affiliation(s)
- Martine Roovers
- Laboratoire de Microbiologie, Université Libre de Bruxelles, Belgium
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