1
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Clifton BE, Fariz MA, Uechi GI, Laurino P. Evolutionary repair reveals an unexpected role of the tRNA modification m1G37 in aminoacylation. Nucleic Acids Res 2021; 49:12467-12485. [PMID: 34761260 PMCID: PMC8643618 DOI: 10.1093/nar/gkab1067] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 10/13/2021] [Accepted: 10/20/2021] [Indexed: 11/13/2022] Open
Abstract
The tRNA modification m1G37, introduced by the tRNA methyltransferase TrmD, is thought to be essential for growth in bacteria because it suppresses translational frameshift errors at proline codons. However, because bacteria can tolerate high levels of mistranslation, it is unclear why loss of m1G37 is not tolerated. Here, we addressed this question through experimental evolution of trmD mutant strains of Escherichia coli. Surprisingly, trmD mutant strains were viable even if the m1G37 modification was completely abolished, and showed rapid recovery of growth rate, mainly via duplication or mutation of the proline-tRNA ligase gene proS. Growth assays and in vitro aminoacylation assays showed that G37-unmodified tRNAPro is aminoacylated less efficiently than m1G37-modified tRNAPro, and that growth of trmD mutant strains can be largely restored by single mutations in proS that restore aminoacylation of G37-unmodified tRNAPro. These results show that inefficient aminoacylation of tRNAPro is the main reason for growth defects observed in trmD mutant strains and that proS may act as a gatekeeper of translational accuracy, preventing the use of error-prone unmodified tRNAPro in translation. Our work shows the utility of experimental evolution for uncovering the hidden functions of essential genes and has implications for the development of antibiotics targeting TrmD.
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Affiliation(s)
- Ben E Clifton
- Protein Engineering and Evolution Unit, Okinawa Institute of Science and Technology, Onna, Okinawa 904-0495, Japan
| | - Muhammad A Fariz
- Protein Engineering and Evolution Unit, Okinawa Institute of Science and Technology, Onna, Okinawa 904-0495, Japan
| | - Gen-Ichiro Uechi
- Protein Engineering and Evolution Unit, Okinawa Institute of Science and Technology, Onna, Okinawa 904-0495, Japan
| | - Paola Laurino
- Protein Engineering and Evolution Unit, Okinawa Institute of Science and Technology, Onna, Okinawa 904-0495, Japan
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2
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Masuda I, Hwang JY, Christian T, Maharjan S, Mohammad F, Gamper H, Buskirk AR, Hou YM. Loss of N1-methylation of G37 in tRNA induces ribosome stalling and reprograms gene expression. eLife 2021; 10:70619. [PMID: 34382933 PMCID: PMC8384417 DOI: 10.7554/elife.70619] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 08/09/2021] [Indexed: 01/20/2023] Open
Abstract
N1-methylation of G37 is required for a subset of tRNAs to maintain the translational reading-frame. While loss of m1G37 increases ribosomal +1 frameshifting, whether it incurs additional translational defects is unknown. Here, we address this question by applying ribosome profiling to gain a genome-wide view of the effects of m1G37 deficiency on protein synthesis. Using E coli as a model, we show that m1G37 deficiency induces ribosome stalling at codons that are normally translated by m1G37-containing tRNAs. Stalling occurs during decoding of affected codons at the ribosomal A site, indicating a distinct mechanism than that of +1 frameshifting, which occurs after the affected codons leave the A site. Enzyme- and cell-based assays show that m1G37 deficiency reduces tRNA aminoacylation and in some cases peptide-bond formation. We observe changes of gene expression in m1G37 deficiency similar to those in the stringent response that is typically induced by deficiency of amino acids. This work demonstrates a previously unrecognized function of m1G37 that emphasizes its role throughout the entire elongation cycle of protein synthesis, providing new insight into its essentiality for bacterial growth and survival.
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Affiliation(s)
- Isao Masuda
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, United States
| | - Jae-Yeon Hwang
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Thomas Christian
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, United States
| | - Sunita Maharjan
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, United States
| | - Fuad Mohammad
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Howard Gamper
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, United States
| | - Allen R Buskirk
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, United States
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3
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Jaroensuk J, Wong YH, Zhong W, Liew CW, Maenpuen S, Sahili AE, Atichartpongkul S, Chionh YH, Nah Q, Thongdee N, McBee ME, Prestwich EG, DeMott MS, Chaiyen P, Mongkolsuk S, Dedon PC, Lescar J, Fuangthong M. Crystal structure and catalytic mechanism of the essential m 1G37 tRNA methyltransferase TrmD from Pseudomonas aeruginosa. RNA (NEW YORK, N.Y.) 2019; 25:1481-1496. [PMID: 31399541 PMCID: PMC6795141 DOI: 10.1261/rna.066746.118] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Accepted: 07/28/2019] [Indexed: 06/10/2023]
Abstract
The tRNA (m1G37) methyltransferase TrmD catalyzes m1G formation at position 37 in many tRNA isoacceptors and is essential in most bacteria, which positions it as a target for antibiotic development. In spite of its crucial role, little is known about TrmD in Pseudomonas aeruginosa (PaTrmD), an important human pathogen. Here we present detailed structural, substrate, and kinetic properties of PaTrmD. The mass spectrometric analysis confirmed the G36G37-containing tRNAs Leu(GAG), Leu(CAG), Leu(UAG), Pro(GGG), Pro(UGG), Pro(CGG), and His(GUG) as PaTrmD substrates. Analysis of steady-state kinetics with S-adenosyl-l-methionine (SAM) and tRNALeu(GAG) showed that PaTrmD catalyzes the two-substrate reaction by way of a ternary complex, while isothermal titration calorimetry revealed that SAM and tRNALeu(GAG) bind to PaTrmD independently, each with a dissociation constant of 14 ± 3 µM. Inhibition by the SAM analog sinefungin was competitive with respect to SAM (Ki = 0.41 ± 0.07 µM) and uncompetitive for tRNA (Ki = 6.4 ± 0.8 µM). A set of crystal structures of the homodimeric PaTrmD protein bound to SAM and sinefungin provide the molecular basis for enzyme competitive inhibition and identify the location of the bound divalent ion. These results provide insights into PaTrmD as a potential target for the development of antibiotics.
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Affiliation(s)
- Juthamas Jaroensuk
- Applied Biological Sciences Program, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok 10210, Thailand
- Singapore-MIT Alliance for Research and Technology Antimicrobial Resistance and Infectious Disease Interdisciplinary Research Groups, 138602 Singapore
| | - Yee Hwa Wong
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
- NTU Institute of Structural Biology, Nanyang Technological University, 636921 Singapore
| | - Wenhe Zhong
- Singapore-MIT Alliance for Research and Technology Antimicrobial Resistance and Infectious Disease Interdisciplinary Research Groups, 138602 Singapore
- NTU Institute of Structural Biology, Nanyang Technological University, 636921 Singapore
| | - Chong Wai Liew
- NTU Institute of Structural Biology, Nanyang Technological University, 636921 Singapore
| | - Somchart Maenpuen
- Department of Biochemistry, Faculty of Science, Burapha University, Chonburi 20131, Thailand
| | - Abbas E Sahili
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
- NTU Institute of Structural Biology, Nanyang Technological University, 636921 Singapore
| | | | - Yok Hian Chionh
- Singapore-MIT Alliance for Research and Technology Antimicrobial Resistance and Infectious Disease Interdisciplinary Research Groups, 138602 Singapore
| | - Qianhui Nah
- Singapore-MIT Alliance for Research and Technology Antimicrobial Resistance and Infectious Disease Interdisciplinary Research Groups, 138602 Singapore
| | - Narumon Thongdee
- Applied Biological Sciences Program, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok 10210, Thailand
| | - Megan E McBee
- Singapore-MIT Alliance for Research and Technology Antimicrobial Resistance and Infectious Disease Interdisciplinary Research Groups, 138602 Singapore
| | - Erin G Prestwich
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Michael S DeMott
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Pimchai Chaiyen
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong 21210, Thailand
| | - Skorn Mongkolsuk
- Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok 10210, Thailand
- Department of Biotechnology, Faculty of Sciences, Mahidol University, Bangkok 10400, Thailand
- Center of Excellence on Environmental Health and Toxicology (EHT), Bangkok 10400, Thailand
| | - Peter C Dedon
- Singapore-MIT Alliance for Research and Technology Antimicrobial Resistance and Infectious Disease Interdisciplinary Research Groups, 138602 Singapore
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Julien Lescar
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
- NTU Institute of Structural Biology, Nanyang Technological University, 636921 Singapore
| | - Mayuree Fuangthong
- Applied Biological Sciences Program, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok 10210, Thailand
- Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok 10210, Thailand
- Center of Excellence on Environmental Health and Toxicology (EHT), Bangkok 10400, Thailand
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4
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Hou YM, Masuda I, Gamper H. Codon-Specific Translation by m 1G37 Methylation of tRNA. Front Genet 2019; 9:713. [PMID: 30687389 PMCID: PMC6335274 DOI: 10.3389/fgene.2018.00713] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 12/20/2018] [Indexed: 12/31/2022] Open
Abstract
Although the genetic code is degenerate, synonymous codons for the same amino acid are not translated equally. Codon-specific translation is important for controlling gene expression and determining the proteome of a cell. At the molecular level, codon-specific translation is regulated by post-transcriptional epigenetic modifications of tRNA primarily at the wobble position 34 and at position 37 on the 3'-side of the anticodon. Modifications at these positions determine the quality of codon-anticodon pairing and the speed of translation on the ribosome. Different modifications operate in distinct mechanisms of codon-specific translation, generating a diversity of regulation that is previously unanticipated. Here we summarize recent work that demonstrates codon-specific translation mediated by the m1G37 methylation of tRNA at CCC and CCU codons for proline, an amino acid that has unique features in translation.
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Affiliation(s)
- Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, United States
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5
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Hou YM, Matsubara R, Takase R, Masuda I, Sulkowska JI. TrmD: A Methyl Transferase for tRNA Methylation With m 1G37. Enzymes 2017; 41:89-115. [PMID: 28601227 DOI: 10.1016/bs.enz.2017.03.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
TrmD is an S-adenosyl methionine (AdoMet)-dependent methyl transferase that synthesizes the methylated m1G37 in tRNA. TrmD is specific to and essential for bacterial growth, and it is fundamentally distinct from its eukaryotic and archaeal counterpart Trm5. TrmD is unusual by using a topological protein knot to bind AdoMet. Despite its restricted mobility, the TrmD knot has complex dynamics necessary to transmit the signal of AdoMet binding to promote tRNA binding and methyl transfer. Mutations in the TrmD knot block this intramolecular signaling and decrease the synthesis of m1G37-tRNA, prompting ribosomes to +1-frameshifts and premature termination of protein synthesis. TrmD is unique among AdoMet-dependent methyl transferases in that it requires Mg2+ in the catalytic mechanism. This Mg2+ dependence is important for regulating Mg2+ transport to Salmonella for survival of the pathogen in the host cell. The strict conservation of TrmD among bacterial species suggests that a better characterization of its enzymology and biology will have a broad impact on our understanding of bacterial pathogenesis.
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Affiliation(s)
- Ya-Ming Hou
- Thomas Jefferson University, Philadelphia, PA, United States.
| | - Ryuma Matsubara
- Thomas Jefferson University, Philadelphia, PA, United States
| | - Ryuichi Takase
- Thomas Jefferson University, Philadelphia, PA, United States
| | - Isao Masuda
- Thomas Jefferson University, Philadelphia, PA, United States
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6
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Zhang Y, Agrebi R, Bellows LE, Collet JF, Kaever V, Gründling A. Evolutionary Adaptation of the Essential tRNA Methyltransferase TrmD to the Signaling Molecule 3',5'-cAMP in Bacteria. J Biol Chem 2016; 292:313-327. [PMID: 27881678 PMCID: PMC5217690 DOI: 10.1074/jbc.m116.758896] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 11/21/2016] [Indexed: 11/06/2022] Open
Abstract
The nucleotide signaling molecule 3',5'-cyclic adenosine monophosphate (3',5'-cAMP) plays important physiological roles, ranging from carbon catabolite repression in bacteria to mediating the action of hormones in higher eukaryotes, including human. However, it remains unclear whether 3',5'-cAMP is universally present in the Firmicutes group of bacteria. We hypothesized that searching for proteins that bind 3',5'-cAMP might provide new insight into this question. Accordingly, we performed a genome-wide screen and identified the essential Staphylococcus aureus tRNA m1G37 methyltransferase enzyme TrmD, which is conserved in all three domains of life as a tight 3',5'-cAMP-binding protein. TrmD enzymes are known to use S-adenosyl-l-methionine (AdoMet) as substrate; we have shown that 3',5'-cAMP binds competitively with AdoMet to the S. aureus TrmD protein, indicating an overlapping binding site. However, the physiological relevance of this discovery remained unclear, as we were unable to identify a functional adenylate cyclase in S. aureus and only detected 2',3'-cAMP but not 3',5'-cAMP in cellular extracts. Interestingly, TrmD proteins from Escherichia coli and Mycobacterium tuberculosis, organisms known to synthesize 3',5'-cAMP, did not bind this signaling nucleotide. Comparative bioinformatics, mutagenesis, and biochemical analyses revealed that the highly conserved Tyr-86 residue in E. coli TrmD is essential to discriminate between 3',5'-cAMP and the native substrate AdoMet. Combined with a phylogenetic analysis, these results suggest that amino acids in the substrate binding pocket of TrmD underwent an adaptive evolution to accommodate the emergence of adenylate cyclases and thus the signaling molecule 3',5'-cAMP. Altogether this further indicates that S. aureus does not produce 3',5'-cAMP, which would otherwise competitively inhibit an essential enzyme.
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Affiliation(s)
- Yong Zhang
- From the Section of Microbiology and MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ, United Kingdom
| | - Rym Agrebi
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium.,de Duve Institute, Université Catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium, and
| | - Lauren E Bellows
- From the Section of Microbiology and MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ, United Kingdom
| | - Jean-François Collet
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium.,de Duve Institute, Université Catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium, and
| | - Volkhard Kaever
- Research Core Unit Metabolomics, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Angelika Gründling
- From the Section of Microbiology and MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ, United Kingdom,
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7
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Abstract
Transfer RNA (tRNA) from all organisms on this planet contains modified nucleosides, which are derivatives of the four major nucleosides. tRNA from Escherichia coli/Salmonella enterica contains 31 different modified nucleosides, which are all, except for one (Queuosine[Q]), synthesized on an oligonucleotide precursor, which through specific enzymes later matures into tRNA. The corresponding structural genes for these enzymes are found in mono- and polycistronic operons, the latter of which have a complex transcription and translation pattern. The syntheses of some of them (e.g.,several methylated derivatives) are catalyzed by one enzyme, which is position and base specific, but synthesis of some have a very complex biosynthetic pathway involving several enzymes (e.g., 2-thiouridines, N6-threonyladenosine [t6A],and Q). Several of the modified nucleosides are essential for viability (e.g.,lysidin, t6A, 1-methylguanosine), whereas deficiency in others induces severe growth defects. However, some have no or only a small effect on growth at laboratory conditions. Modified nucleosides that are present in the anticodon loop or stem have a fundamental influence on the efficiency of charging the tRNA, reading cognate codons, and preventing missense and frameshift errors. Those, which are present in the body of the tRNA, have a primarily stabilizing effect on the tRNA. Thus, the ubiquitouspresence of these modified nucleosides plays a pivotal role in the function of the tRNA by their influence on the stability and activity of the tRNA.
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8
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A divalent metal ion-dependent N(1)-methyl transfer to G37-tRNA. ACTA ACUST UNITED AC 2014; 21:1351-1360. [PMID: 25219964 DOI: 10.1016/j.chembiol.2014.07.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 07/20/2014] [Accepted: 07/22/2014] [Indexed: 01/09/2023]
Abstract
The catalytic mechanism of the majority of S-adenosyl methionine (AdoMet)-dependent methyl transferases requires no divalent metal ions. Here we report that methyl transfer from AdoMet to N(1) of G37-tRNA, catalyzed by the bacterial TrmD enzyme, is strongly dependent on divalent metal ions and that Mg(2+) is the most physiologically relevant. Kinetic isotope analysis, metal rescue, and spectroscopic measurements indicate that Mg(2+) is not involved in substrate binding, but in promoting methyl transfer. On the basis of the pH-activity profile indicating one proton transfer during the TrmD reaction, we propose a catalytic mechanism in which the role of Mg(2+) is to help to increase the nucleophilicity of N(1) of G37 and stabilize the negative developing charge on O(6) during attack on the methyl sulfonium of AdoMet. This work demonstrates how Mg(2+) contributes to the catalysis of AdoMet-dependent methyl transfer in one of the most crucial posttranscriptional modifications to tRNA.
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9
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Björk GR, Hagervall TG. Transfer RNA Modification: Presence, Synthesis, and Function. EcoSal Plus 2014; 6. [PMID: 26442937 DOI: 10.1128/ecosalplus.esp-0007-2013] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Indexed: 06/05/2023]
Abstract
Transfer RNA (tRNA) from all organisms on this planet contains modified nucleosides, which are derivatives of the four major nucleosides. tRNA from Escherichia coli/Salmonella enterica serovar Typhimurium contains 33 different modified nucleosides, which are all, except one (Queuosine [Q]), synthesized on an oligonucleotide precursor, which by specific enzymes later matures into tRNA. The structural genes for these enzymes are found in mono- and polycistronic operons, the latter of which have a complex transcription and translation pattern. The synthesis of the tRNA-modifying enzymes is not regulated similarly, and it is not coordinated to that of their substrate, the tRNA. The synthesis of some of them (e.g., several methylated derivatives) is catalyzed by one enzyme, which is position and base specific, whereas synthesis of some has a very complex biosynthetic pathway involving several enzymes (e.g., 2-thiouridines, N 6-cyclicthreonyladenosine [ct6A], and Q). Several of the modified nucleosides are essential for viability (e.g., lysidin, ct6A, 1-methylguanosine), whereas the deficiency of others induces severe growth defects. However, some have no or only a small effect on growth at laboratory conditions. Modified nucleosides that are present in the anticodon loop or stem have a fundamental influence on the efficiency of charging the tRNA, reading cognate codons, and preventing missense and frameshift errors. Those that are present in the body of the tRNA primarily have a stabilizing effect on the tRNA. Thus, the ubiquitous presence of these modified nucleosides plays a pivotal role in the function of the tRNA by their influence on the stability and activity of the tRNA.
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Affiliation(s)
- Glenn R Björk
- Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden
| | - Tord G Hagervall
- Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden
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10
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Masuda I, Sakaguchi R, Liu C, Gamper H, Hou YM. The temperature sensitivity of a mutation in the essential tRNA modification enzyme tRNA methyltransferase D (TrmD). J Biol Chem 2013; 288:28987-96. [PMID: 23986443 DOI: 10.1074/jbc.m113.485797] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Conditional temperature-sensitive (ts) mutations are important reagents to study essential genes. Although it is commonly assumed that the ts phenotype of a specific mutation arises from thermal denaturation of the mutant enzyme, the possibility also exists that the mutation decreases the enzyme activity to a certain level at the permissive temperature and aggravates the negative effect further upon temperature upshifts. Resolving these possibilities is important for exploiting the ts mutation for studying the essential gene. The trmD gene is essential for growth in bacteria, encoding the enzyme for converting G37 to m(1)G37 on the 3' side of the tRNA anticodon. This conversion involves methyl transfer from S-adenosyl methionine and is critical to minimize tRNA frameshift errors on the ribosome. Using the ts-S88L mutation of Escherichia coli trmD as an example, we show that although the mutation confers thermal lability to the enzyme, the effect is relatively minor. In contrast, the mutation decreases the catalytic efficiency of the enzyme to 1% at the permissive temperature, and at the nonpermissive temperature, it renders further deterioration of activity to 0.1%. These changes are accompanied by losses of both the quantity and quality of tRNA methylation, leading to the potential of cellular pleiotropic effects. This work illustrates the principle that the ts phenotype of an essential gene mutation can be closely linked to the catalytic defect of the gene product and that such a mutation can provide a useful tool to study the mechanism of catalytic inactivation.
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Affiliation(s)
- Isao Masuda
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
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11
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Urbonavičius J, Jäger G, Björk GR. Amino acid residues of the Escherichia coli tRNA(m5U54)methyltransferase (TrmA) critical for stability, covalent binding of tRNA and enzymatic activity. Nucleic Acids Res 2007; 35:3297-305. [PMID: 17459887 PMCID: PMC1904294 DOI: 10.1093/nar/gkm205] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Escherichia coli trmA gene encodes the tRNA(m5U54)methyltransferase, which catalyses the formation of m5U54 in tRNA. During the synthesis of m5U54, a covalent 62-kDa TrmA-tRNA intermediate is formed between the amino acid C324 of the enzyme and the 6-carbon of uracil. We have analysed the formation of this TrmA-tRNA intermediate and m5U54 in vivo, using mutants with altered TrmA. We show that the amino acids F188, Q190, G220, D299, R302, C324 and E358, conserved in the C-terminal catalytic domain of several RNA(m5U)methyltransferases of the COG2265 family, are important for the formation of the TrmA-tRNA intermediate and/or the enzymatic activity. These amino acids seem to have the same function as the ones present in the catalytic domain of RumA, whose structure is known, and which catalyses the formation of m5U in position 1939 of E. coli 23 S rRNA. We propose that the unusually high in vivo level of the TrmA-tRNA intermediate in wild-type cells may be due to a suboptimal cellular concentration of SAM, which is required to resolve this intermediate. Our results are consistent with the modular evolution of RNA(m5U)methyltransferases, in which the specificity of the enzymatic reaction is achieved by combining the conserved catalytic domain with different RNA-binding domains.
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Affiliation(s)
| | | | - Glenn R. Björk
- *To whom correspondence should be addressed. Tel: +46-90-7856759; Fax: +46-90-772630;
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12
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Chen P, Crain PF, Näsvall SJ, Pomerantz SC, Björk GR. A "gain of function" mutation in a protein mediates production of novel modified nucleosides. EMBO J 2005; 24:1842-51. [PMID: 15861125 PMCID: PMC1142597 DOI: 10.1038/sj.emboj.7600666] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2004] [Accepted: 04/08/2005] [Indexed: 11/08/2022] Open
Abstract
The mutation sufY204 mediates suppression of a +1 frameshift mutation in the histidine operon of Salmonella enterica serovar Typhimurium and synthesis of two novel modified nucleosides in tRNA. The sufY204 mutation, which results in an amino-acid substitution in a protein, is, surprisingly, dominant over its wild-type allele and thus it is a "gain of function" mutation. One of the new nucleosides is 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U34) modified by addition of a C(10)H(17) side chain of unknown structure. Increased amounts of both nucleosides in tRNA are correlated to gene dosage of the sufY204 allele, to an increased efficiency of frameshift suppression, and to a decreased amount of the wobble nucleoside mnm(5)s(2)U34 in tRNA. Purified tRNA(Gln)(cmnm(5)s(2)UUG) in the mutant strain contains a modified nucleoside similar to the novel nucleosides and the level of aminoacylation of tRNA(Gln)(cmnm(5)s(2)UUG) was reduced to 26% compared to that found in the wild type (86%). The results are discussed in relation to the mechanism of reading frame maintenance and the evolution of modified nucleosides in tRNA.
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Affiliation(s)
- Peng Chen
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Pamela F Crain
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT, USA
| | | | - Steven C Pomerantz
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT, USA
| | - Glenn R Björk
- Department of Molecular Biology, Umeå University, Umeå, Sweden
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13
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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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O'Dwyer K, Watts JM, Biswas S, Ambrad J, Barber M, Brulé H, Petit C, Holmes DJ, Zalacain M, Holmes WM. Characterization of Streptococcus pneumoniae TrmD, a tRNA methyltransferase essential for growth. J Bacteriol 2004; 186:2346-54. [PMID: 15060037 PMCID: PMC412112 DOI: 10.1128/jb.186.8.2346-2354.2004] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Down-regulation of expression of trmD, encoding the enzyme tRNA (guanosine-1)-methyltransferase, has shown that this gene is essential for growth of Streptococcus pneumoniae. The S. pneumoniae trmD gene has been isolated and expressed in Escherichia coli by using a His-tagged T7 expression vector. Recombinant protein has been purified, and its catalytic and physical properties have been characterized. The native enzyme displays a molecular mass of approximately 65,000 Da, suggesting that streptococcal TrmD is a dimer of two identical subunits. In fact, this characteristic can be extended to several other TrmD orthologs, including E. coli TrmD. Kinetic studies show that the streptococcal enzyme utilizes a sequential mechanism. Binding of tRNA by gel mobility shift assays gives a dissociation constant of 22 nM for one of its substrates, tRNA(Leu)(CAG). Other heterologous nonsubstrate tRNA species, like, tRNA (Thr)(GGT), tRNA(Phe), and tRNA (Ala)(TGC), bind the enzyme with similar affinities, suggesting that tRNA specificity is achieved via a postbinding event(s).
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Affiliation(s)
- Karen O'Dwyer
- Microbial, Musculoskeletal and Proliferative Diseases CEDD, GlaxoSmithKline, Collegeville, Pennsylvania 19426, USA
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Agris PF. Decoding the genome: a modified view. Nucleic Acids Res 2004; 32:223-38. [PMID: 14715921 PMCID: PMC384350 DOI: 10.1093/nar/gkh185] [Citation(s) in RCA: 270] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2003] [Revised: 12/02/2003] [Accepted: 12/02/2003] [Indexed: 11/12/2022] Open
Abstract
Transfer RNA's role in decoding the genome is critical to the accuracy and efficiency of protein synthesis. Though modified nucleosides were identified in RNA 50 years ago, only recently has their importance to tRNA's ability to decode cognate and wobble codons become apparent. RNA modifications are ubiquitous. To date, some 100 different posttranslational modifications have been identified. Modifications of tRNA are the most extensively investigated; however, many other RNAs have modified nucleosides. The modifications that occur at the first, or wobble position, of tRNA's anticodon and those 3'-adjacent to the anticodon are of particular interest. The tRNAs most affected by individual and combinations of modifications respond to codons in mixed codon boxes where distinction of the third codon base is important for discriminating between the correct cognate or wobble codons and the incorrect near-cognate codons (e.g. AAA/G for lysine versus AAU/C asparagine). In contrast, other modifications expand wobble codon recognition, such as U*U base pairing, for tRNAs that respond to multiple codons of a 4-fold degenerate codon box (e.g. GUU/A/C/G for valine). Whether restricting codon recognition, expanding wobble, enabling translocation, or maintaining the messenger RNA, reading frame modifications appear to reduce anticodon loop dynamics to that accepted by the ribosome. Therefore, we suggest that anticodon stem and loop domain nucleoside modifications allow a limited number of tRNAs to accurately and efficiently decode the 61 amino acid codons by selectively restricting some anticodon-codon interactions and expanding others.
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Affiliation(s)
- Paul F Agris
- Department of Molecular and Structural Biochemistry, 128 Polk Hall, Campus Box 7622, North Carolina State University, Raleigh, NC 27695-7622, USA.
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