51
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Abstract
tRNA molecules undergo extensive post-transcriptional processing to generate the mature functional tRNA species that are essential for translation in all organisms. These processing steps include the introduction of numerous specific chemical modifications to nucleotide bases and sugars; among these modifications, methylation reactions are by far the most abundant. The tRNA methyltransferases comprise a diverse enzyme superfamily, including members of multiple structural classes that appear to have arisen independently during evolution. Even among closely related family members, examples of unusual substrate specificity and chemistry have been observed. Here we review recent advances in tRNA methyltransferase mechanism and function with a particular emphasis on discoveries of alternative substrate specificities and chemistry associated with some methyltransferases. Although the molecular function for a specific tRNA methylation may not always be clear, mutations in tRNA methyltransferases have been increasingly associated with human disease. The impact of tRNA methylation on human biology is also discussed.
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Affiliation(s)
- William E Swinehart
- a Center for RNA Biology and Department of Chemistry and Biochemistry ; Ohio State University ; Columbus , OH USA
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52
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Cozen AE, Quartley E, Holmes AD, Hrabeta-Robinson E, Phizicky EM, Lowe TM. ARM-seq: AlkB-facilitated RNA methylation sequencing reveals a complex landscape of modified tRNA fragments. Nat Methods 2015; 12:879-84. [PMID: 26237225 PMCID: PMC4553111 DOI: 10.1038/nmeth.3508] [Citation(s) in RCA: 317] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 07/09/2015] [Indexed: 01/02/2023]
Abstract
High throughput RNA sequencing has accelerated discovery of the complex regulatory roles of small RNAs, but RNAs containing modified nucleosides may escape detection when those modifications interfere with reverse transcription during RNA-seq library preparation. Here we describe AlkB-facilitated RNA Methylation sequencing (ARM-Seq) which uses pre-treatment with Escherichia coli AlkB to demethylate 1-methyladenosine, 3-methylcytidine, and 1-methylguanosine, all commonly found in transfer RNAs. Comparative methylation analysis using ARM-Seq provides the first detailed, transcriptome-scale map of these modifications, and reveals an abundance of previously undetected, methylated small RNAs derived from tRNAs. ARM-Seq demonstrates that tRNA-derived small RNAs accurately recapitulate the m1A modification state for well-characterized yeast tRNAs, and generates new predictions for a large number of human tRNAs, including tRNA precursors and mitochondrial tRNAs. Thus, ARM-Seq provides broad utility for identifying previously overlooked methyl-modified RNAs, can efficiently monitor methylation state, and may reveal new roles for tRNA-derived RNAs as biomarkers or signaling molecules.
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Affiliation(s)
- Aaron E Cozen
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, California, USA
| | - Erin Quartley
- Department of Biochemistry &Biophysics, University of Rochester School of Medicine, Rochester, New York, USA
| | - Andrew D Holmes
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, California, USA
| | - Eva Hrabeta-Robinson
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, California, USA
| | - Eric M Phizicky
- Department of Biochemistry &Biophysics, University of Rochester School of Medicine, Rochester, New York, USA.,Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, USA
| | - Todd M Lowe
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, California, USA
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53
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Chan CTY, Deng W, Li F, DeMott MS, Babu IR, Begley TJ, Dedon PC. Highly Predictive Reprogramming of tRNA Modifications Is Linked to Selective Expression of Codon-Biased Genes. Chem Res Toxicol 2015; 28:978-88. [PMID: 25772370 PMCID: PMC4438938 DOI: 10.1021/acs.chemrestox.5b00004] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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Cells respond to stress by controlling
gene expression at several
levels, with little known about the role of translation. Here, we
demonstrate a coordinated translational stress response system involving
stress-specific reprogramming of tRNA wobble modifications that leads
to selective translation of codon-biased mRNAs representing different
classes of critical response proteins. In budding yeast exposed to
four oxidants and five alkylating agents, tRNA modification patterns
accurately distinguished among chemically similar stressors, with
14 modified ribonucleosides forming the basis for a data-driven model
that predicts toxicant chemistry with >80% sensitivity and specificity.
tRNA modification subpatterns also distinguish SN1 from
SN2 alkylating agents, with SN2-induced increases
in m3C in tRNA mechanistically linked to selective translation
of threonine-rich membrane proteins from genes enriched with ACC and
ACT degenerate codons for threonine. These results establish tRNA
modifications as predictive biomarkers of exposure and illustrate
a novel regulatory mechanism for translational control of cell stress
response.
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Affiliation(s)
| | | | | | | | | | - Thomas J Begley
- ∥College of Nanoscale Science, State University of New York, Albany, New York 12203, United States
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54
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Abstract
Endocytosis, the process whereby the plasma membrane invaginates to form vesicles, is essential for bringing many substances into the cell and for membrane turnover. The mechanism driving clathrin-mediated endocytosis (CME) involves > 50 different protein components assembling at a single location on the plasma membrane in a temporally ordered and hierarchal pathway. These proteins perform precisely choreographed steps that promote receptor recognition and clustering, membrane remodeling, and force-generating actin-filament assembly and turnover to drive membrane invagination and vesicle scission. Many critical aspects of the CME mechanism are conserved from yeast to mammals and were first elucidated in yeast, demonstrating that it is a powerful system for studying endocytosis. In this review, we describe our current mechanistic understanding of each step in the process of yeast CME, and the essential roles played by actin polymerization at these sites, while providing a historical perspective of how the landscape has changed since the preceding version of the YeastBook was published 17 years ago (1997). Finally, we discuss the key unresolved issues and where future studies might be headed.
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Affiliation(s)
- Bruce L Goode
- Brandeis University, Department of Biology, Rosenstiel Center, Waltham, Massachusetts 02454
| | - Julian A Eskin
- Brandeis University, Department of Biology, Rosenstiel Center, Waltham, Massachusetts 02454
| | - Beverly Wendland
- The Johns Hopkins University, Department of Biology, Baltimore, Maryland 21218
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55
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Singer-Krüger B, Jansen RP. Here, there, everywhere. mRNA localization in budding yeast. RNA Biol 2014; 11:1031-9. [PMID: 25482891 DOI: 10.4161/rna.29945] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
mRNA localization and localized translation is a common mechanism that contributes to cell polarity and cellular asymmetry. In metazoan, mRNA transport participates in embryonic axis determination and neuronal plasticity. Since the mRNA localization process and its molecular machinery are rather complex in higher eukaryotes, the unicellular yeast Saccharomyces cerevisiae has become an attractive model to study mRNA localization. Although the focus has so far been on the mechanism of ASH1 mRNA transport, it has become evident that mRNA localization also assists in protein sorting to organelles, as well as in polarity establishment and maintenance. A diversity of different pathways has been identified that targets mRNA to their destination site, ranging from motor protein-dependent trafficking of translationally silenced mRNAs to co-translational targeting, in which mRNAs hitch-hike to organelles on ribosomes during nascent polypeptide chain elongation. The presence of these diverse pathways in yeast allows a systemic analysis of the contribution of mRNA localization to the physiology of a cell.
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Affiliation(s)
- Birgit Singer-Krüger
- a Interfaculty Institute of Biochemistry ; University of Tübingen ; Tübingen , Germany
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56
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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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57
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Suzuki T, Suzuki T. A complete landscape of post-transcriptional modifications in mammalian mitochondrial tRNAs. Nucleic Acids Res 2014; 42:7346-57. [PMID: 24831542 PMCID: PMC4066797 DOI: 10.1093/nar/gku390] [Citation(s) in RCA: 216] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In mammalian mitochondria, 22 species of tRNAs encoded in mitochondrial DNA play crucial roles in the translation of 13 essential subunits of the respiratory chain complexes involved in oxidative phosphorylation. Following transcription, mitochondrial tRNAs are modified by nuclear-encoded tRNA-modifying enzymes. These modifications are required for the proper functioning of mitochondrial tRNAs (mt tRNAs), and the absence of these modifications can cause pathological consequences. To date, however, the information available about these modifications has been incomplete. To address this issue, we isolated all 22 species of mt tRNAs from bovine liver and comprehensively determined the post-transcriptional modifications in each tRNA by mass spectrometry. Here, we describe the primary structures with post-transcriptional modifications of seven species of mt tRNAs which were previously uncharacterized, and provide revised information regarding base modifications in five other mt tRNAs. In the complete set of bovine mt tRNAs, we found 15 species of modified nucleosides at 118 positions (7.48% of total bases). This result provides insight into the molecular mechanisms underlying the decoding system in mammalian mitochondria and enables prediction of candidate tRNA-modifying enzymes responsible for each modification of mt tRNAs.
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Affiliation(s)
- Takeo Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Tsutomu Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
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58
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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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59
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Xie P, Wei FY, Hirata S, Kaitsuka T, Suzuki T, Suzuki T, Tomizawa K. Quantitative PCR measurement of tRNA 2-methylthio modification for assessing type 2 diabetes risk. Clin Chem 2013; 59:1604-12. [PMID: 23974085 DOI: 10.1373/clinchem.2013.210401] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Genetic variants in the human CDKAL1 (CDK5 regulatory subunit associated protein 1-like 1) gene have been associated with reduced insulin secretion and type 2 diabetes (T2D). CDKAL1 is a methylthiotransferase that catalyzes 2-methylthio (ms(2)) modification of the adenine at position 37 (A37) of cytoplasmic tRNA(Lys)(UUU). We investigated the ms(2)-modification level of tRNA(Lys)(UUU) as a direct readout of CDKAL1 enzyme activity in human samples. METHOD We developed a quantitative PCR (qPCR)-based method to measure ms(2) modification. tRNA(Lys)(UUU) was reverse-transcribed with 2 unique primers: Reverse primer r1 was designed to anneal to the middle of this tRNA, including the nucleotide at A37, and reverse primer r2 was designed to anneal to the region downstream (3') of A37. Subsequent qPCR was performed to detect the corresponding transcribed cDNAs. RESULTS The efficiency of reverse transcription of tRNA(Lys)(UUU) was ms(2)-modification dependent. The relative difference in threshold cycle number obtained with the r1 or r2 primer yielded the ms(2)-modification level in tRNA(Lys)(UUU) precisely as predicted by an original mathematical model. The method was capable of measuring ms(2)-modification levels in tRNA(Lys)(UUU) in total RNA isolated from human peripheral blood samples, revealing that the ms(2)-modification rate in tRNA(Lys)(UUU) was decreased in individuals carrying the CDKAL1 genotype associated with T2D. In addition, the ms(2)-modification level was correlated with insulin secretion. CONCLUSIONS The results point to the critical role of ms(2) modification in T2D and to a potential clinical use of a simple and high-throughput method for assessing T2D risk.
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Affiliation(s)
- Peiyu Xie
- Department of Molecular Physiology, Kumamoto University, Kumamoto, Japan
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60
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El Yacoubi B, Bailly M, de Crécy-Lagard V. Biosynthesis and Function of Posttranscriptional Modifications of Transfer RNAs. Annu Rev Genet 2012; 46:69-95. [DOI: 10.1146/annurev-genet-110711-155641] [Citation(s) in RCA: 380] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Basma El Yacoubi
- Department of Microbiology and Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611-0700;
| | - Marc Bailly
- Department of Microbiology and Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611-0700;
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611-0700;
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61
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Zeng Y, Kulkarni A, Yang Z, Patil PB, Zhou W, Chi X, Van Lanen S, Chen S. Biosynthesis of albomycin δ(2) provides a template for assembling siderophore and aminoacyl-tRNA synthetase inhibitor conjugates. ACS Chem Biol 2012; 7:1565-75. [PMID: 22704654 DOI: 10.1021/cb300173x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
"Trojan horse" antibiotic albomycins are peptidyl nucleosides consisting of a highly modified 4'-thiofuranosyl cytosine moiety and a ferrichrome siderophore that are linked by a peptide bond via a serine residue. While the latter component serves to sequester iron from the environment, the seryl nucleoside portion is a potent inhibitor of bacterial seryl-tRNA synthetases, resulting in broad-spectrum antimicrobial activities of albomycin δ(2). The isolation of albomycins has revealed this biological activity is optimized only following two unusual cytosine modifications, N4-carbamoylation and N3-methylation. We identified a genetic locus (named abm) for albomycin production in Streptomyces sp. ATCC 700974. Gene deletion and complementation experiments along with bioinformatic analysis suggested 18 genes are responsible for albomycin biosynthesis and resistance, allowing us to propose a potential biosynthetic pathway for installing the novel chemical features. The gene abmI, encoding a putative methyltransferase, was functionally assigned in vitro and shown to modify the N3 of a variety of cytosine-containing nucleosides and antibiotics such as blasticidin S. Furthermore, a ΔabmI mutant was shown to produce the descarbamoyl-desmethyl albomycin analogue, supporting that the N3-methylation occurs before the N4-carbamoylation in the biosynthesis of albomycin δ(2). The combined genetic information was utilized to identify an abm-related locus (named ctj) from the draft genome of Streptomyces sp. C. Cross-complementation experiments and in vitro studies with CtjF, the AbmI homologue, suggest the production of a similar 4'-thiofuranosyl cytosine in this organism. In total, the genetic and biochemical data provide a biosynthetic template for assembling siderophore-inhibitor conjugates and modifying the albomycin scaffold to generate new derivatives.
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Affiliation(s)
- Yu Zeng
- Molecular and Cellular Biology
Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701, United States
| | - Aditya Kulkarni
- Molecular and Cellular Biology
Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701, United States
| | - Zhaoyong Yang
- Department of Pharmaceutical
Sciences, University of Kentucky College of Pharmacy, Lexington, Kentucky 40536, United States
| | - Preeti B. Patil
- Molecular and Cellular Biology
Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701, United States
| | - Wei Zhou
- Molecular and Cellular Biology
Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701, United States
| | - Xiuling Chi
- Department of Pharmaceutical
Sciences, University of Kentucky College of Pharmacy, Lexington, Kentucky 40536, United States
| | - Steven Van Lanen
- Department of Pharmaceutical
Sciences, University of Kentucky College of Pharmacy, Lexington, Kentucky 40536, United States
| | - Shawn Chen
- Molecular and Cellular Biology
Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701, United States
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62
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Bi E, Park HO. Cell polarization and cytokinesis in budding yeast. Genetics 2012; 191:347-87. [PMID: 22701052 PMCID: PMC3374305 DOI: 10.1534/genetics.111.132886] [Citation(s) in RCA: 217] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Accepted: 11/04/2011] [Indexed: 12/26/2022] Open
Abstract
Asymmetric cell division, which includes cell polarization and cytokinesis, is essential for generating cell diversity during development. The budding yeast Saccharomyces cerevisiae reproduces by asymmetric cell division, and has thus served as an attractive model for unraveling the general principles of eukaryotic cell polarization and cytokinesis. Polarity development requires G-protein signaling, cytoskeletal polarization, and exocytosis, whereas cytokinesis requires concerted actions of a contractile actomyosin ring and targeted membrane deposition. In this chapter, we discuss the mechanics and spatial control of polarity development and cytokinesis, emphasizing the key concepts, mechanisms, and emerging questions in the field.
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Affiliation(s)
- Erfei Bi
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6058, USA.
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63
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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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64
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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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65
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Kilchert C, Spang A. Cotranslational transport of ABP140 mRNA to the distal pole of S. cerevisiae. EMBO J 2011; 30:3567-80. [PMID: 21792172 DOI: 10.1038/emboj.2011.247] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 06/24/2011] [Indexed: 11/09/2022] Open
Abstract
In budding yeast, several mRNAs are selectively transported into the daughter cell in an actin-dependent manner by a specialized myosin system, the SHE machinery. With ABP140 mRNA, we now describe the first mRNA that is transported in the opposite direction and localizes to the distal pole of the mother cell, independent of the SHE machinery. Distal pole localization is not observed in mutants devoid of actin cables and can be disrupted by latrunculin A. Furthermore, localization of ABP140 mRNA requires the N-terminal actin-binding domain of Abp140p to be expressed. By replacing the N-terminal localization motif, ABP140 mRNA can be retargeted to different subcellular structures. In addition, accumulation of the mRNA at the distal pole can be prevented by disruption of polysomes. Using the MS2 system, the mRNA was found to associate with actin cables and to follow actin cable dynamics. We therefore propose a model of translational coupling, in which ABP140 mRNA is tethered to actin cables via its nascent protein product and is transported to the distal pole by actin retrograde flow.
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