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Schultz SK, Kothe U. RNA modifying enzymes shape tRNA biogenesis and function. J Biol Chem 2024:107488. [PMID: 38908752 DOI: 10.1016/j.jbc.2024.107488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 06/11/2024] [Accepted: 06/12/2024] [Indexed: 06/24/2024] Open
Abstract
Transfer RNAs (tRNAs) are the most highly modified cellular RNAs, both with respect to the proportion of nucleotides that are modified within the tRNA sequence and with respect to the extraordinary diversity in tRNA modification chemistry. However, the functions of many different tRNA modifications are only beginning to emerge. tRNAs have two general clusters of modifications. The first cluster is within the anticodon stem-loop including several modifications essential for protein translation. The second cluster of modifications is within the tRNA elbow, and roles for these modifications are less clear. In general, tRNA elbow modifications are typically not essential for cell growth, but nonetheless several tRNA elbow modifications have been highly conserved throughout all domains of life. In addition to forming modifications, many tRNA modifying enzymes have been demonstrated or hypothesized to additionally play an important role in folding tRNA acting as tRNA chaperones. In this review, we summarize the known functions of tRNA modifying enzymes throughout the lifecycle of a tRNA molecule, from transcription to degradation. Thereby, we describe how tRNA modification and folding by tRNA modifying enzymes enhance tRNA maturation, tRNA aminoacylation, and tRNA function during protein synthesis, ultimately impacting cellular phenotypes and disease.
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Affiliation(s)
- Sarah K Schultz
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada; Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada.
| | - Ute Kothe
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada; Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada.
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2
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Bowles IE, Jackman JE. A tRNA-specific function for tRNA methyltransferase Trm10 is associated with a new tRNA quality control mechanism in Saccharomyces cerevisiae. RNA (NEW YORK, N.Y.) 2024; 30:171-187. [PMID: 38071471 PMCID: PMC10798241 DOI: 10.1261/rna.079861.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 11/28/2023] [Indexed: 01/18/2024]
Abstract
In Saccharomyces cerevisiae, a single homolog of the tRNA methyltransferase Trm10 performs m1G9 modification on 13 different tRNAs. Here we provide evidence that the m1G9 modification catalyzed by S. cerevisiae Trm10 plays a biologically important role for one of these tRNA substrates, tRNATrp Overexpression of tRNATrp (and not any of 38 other elongator tRNAs) rescues growth hypersensitivity of the trm10Δ strain in the presence of the antitumor drug 5-fluorouracil (5FU). Mature tRNATrp is depleted in trm10Δ cells, and its levels are further decreased upon growth in 5FU, while another Trm10 substrate (tRNAGly) is not affected under these conditions. Thus, m1G9 in S. cerevisiae is another example of a tRNA modification that is present on multiple tRNAs but is only essential for the biological function of one of those species. In addition to the effects of m1G9 on mature tRNATrp, precursor tRNATrp species accumulate in the same strains, an effect that is due to at least two distinct mechanisms. The levels of mature tRNATrp are rescued in the trm10Δmet22Δ strain, consistent with the known role of Met22 in tRNA quality control, where deletion of met22 causes inhibition of 5'-3' exonucleases that catalyze tRNA decay. However, none of the known Met22-associated exonucleases appear to be responsible for the decay of hypomodified tRNATrp, based on the inability of mutants of each enzyme to rescue the growth of the trm10Δ strain in the presence of 5FU. Thus, the surveillance of tRNATrp appears to constitute a distinct tRNA quality control pathway in S. cerevisiae.
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Affiliation(s)
- Isobel E Bowles
- Department of Chemistry and Biochemistry, Center for RNA Biology, and Ohio State Biochemistry Program, Columbus, Ohio 43210, USA
| | - Jane E Jackman
- Department of Chemistry and Biochemistry, Center for RNA Biology, and Ohio State Biochemistry Program, Columbus, Ohio 43210, USA
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3
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Altered tRNA processing is linked to a distinct and unusual La protein in Tetrahymena thermophila. Nat Commun 2022; 13:7332. [PMID: 36443289 PMCID: PMC9705548 DOI: 10.1038/s41467-022-34796-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 11/07/2022] [Indexed: 11/29/2022] Open
Abstract
Nascent pre-tRNAs are transcribed by RNA polymerase III and immediately bound by La proteins on the UUU-3'OH sequence, using a tandem arrangement of the La motif and an adjacent RNA recognition motif-1 (RRM1), resulting in protection from 3'-exonucleases and promotion of pre-tRNA folding. The Tetrahymena thermophila protein Mlp1 has been previously classified as a genuine La protein, despite the predicted absence of the RRM1. We find that Mlp1 functions as a La protein through binding of pre-tRNAs, and affects pre-tRNA processing in Tetrahymena thermophila and when expressed in fission yeast. However, unlike in other examined eukaryotes, depletion of Mlp1 results in 3'-trailer stabilization. The 3'-trailers in Tetrahymena thermophila are uniquely short relative to other examined eukaryotes, and 5'-leaders have evolved to disfavour pre-tRNA leader/trailer pairing. Our data indicate that this variant Mlp1 architecture is linked to an altered, novel mechanism of tRNA processing in Tetrahymena thermophila.
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4
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Antika TR, Nazilah KR, Lee YH, Lo YT, Yeh CS, Yeh FL, Chang TH, Wang TL, Wang CC. Human Thg1 displays tRNA-inducible GTPase activity. Nucleic Acids Res 2022; 50:10015-10025. [PMID: 36107775 PMCID: PMC9508852 DOI: 10.1093/nar/gkac768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 08/22/2022] [Accepted: 08/26/2022] [Indexed: 11/13/2022] Open
Abstract
tRNAHis guanylyltransferase (Thg1) catalyzes the 3′-5′ incorporation of guanosine into position -1 (G-1) of tRNAHis. G-1 is unique to tRNAHis and is crucial for recognition by histidyl-tRNA synthetase (HisRS). Yeast Thg1 requires ATP for G-1 addition to tRNAHis opposite A73, whereas archaeal Thg1 requires either ATP or GTP for G-1 addition to tRNAHis opposite C73. Paradoxically, human Thg1 (HsThg1) can add G-1 to tRNAsHis with A73 (cytoplasmic) and C73 (mitochondrial). As N73 is immediately followed by a CCA end (positions 74–76), how HsThg1 prevents successive 3′-5′ incorporation of G-1/G-2/G-3 into mitochondrial tRNAHis (tRNAmHis) through a template-dependent mechanism remains a puzzle. We showed herein that mature native human tRNAmHis indeed contains only G-1. ATP was absolutely required for G-1 addition to tRNAmHis by HsThg1. Although HsThg1 could incorporate more than one GTP into tRNAmHisin vitro, a single-GTP incorporation prevailed when the relative GTP level was low. Surprisingly, HsThg1 possessed a tRNA-inducible GTPase activity, which could be inhibited by ATP. Similar activity was found in other high-eukaryotic dual-functional Thg1 enzymes, but not in yeast Thg1. This study suggests that HsThg1 may downregulate the level of GTP through its GTPase activity to prevent multiple-GTP incorporation into tRNAmHis.
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Affiliation(s)
- Titi Rindi Antika
- Department of Life Sciences, National Central University , Zhongli District, Taoyuan 320317, Taiwan
| | - Kun Rohmatan Nazilah
- Department of Life Sciences, National Central University , Zhongli District, Taoyuan 320317, Taiwan
| | - Yi-Hsueh Lee
- Department of Life Sciences, National Central University , Zhongli District, Taoyuan 320317, Taiwan
| | - Ya-Ting Lo
- Department of Life Sciences, National Central University , Zhongli District, Taoyuan 320317, Taiwan
| | - Chung-Shu Yeh
- Genomics Research Center , Academia Sinica, Nankang District, Taipei 11529, Taiwan
| | - Fu-Lung Yeh
- Genomics Research Center , Academia Sinica, Nankang District, Taipei 11529, Taiwan
| | - Tien-Hsien Chang
- Genomics Research Center , Academia Sinica, Nankang District, Taipei 11529, Taiwan
| | - Tzu-Ling Wang
- Graduate Institute of Mathematics and Science Education, National Tsing Hua University , Hsinchu City 30014, Taiwan
| | - Chien-Chia Wang
- Department of Life Sciences, National Central University , Zhongli District, Taoyuan 320317, Taiwan
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5
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Hayashi S, Matsui M, Ikeda A, Yoshihisa T. Six identical tRNATrpCCA genes express a similar amount of mature tRNATrpCCA but unequally contribute to yeast cell growth. Biosci Biotechnol Biochem 2022; 86:1398-1404. [PMID: 35948278 DOI: 10.1093/bbb/zbac134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 07/28/2022] [Indexed: 11/14/2022]
Abstract
Saccharomyces cerevisiae has six synonymous tRNATrpCCA genes encoding the identical sequence, including their intronic region. They are supposed to express tRNATrpCCA in the same quality and quantity. Here, we generated single to quintuple deletion strains with all the possible combinations of the synonymous tRNATrpCCA genes to analyze whether those individual genes equally contribute cell viability and tRNA production. The quintuple deletion strains that only harbor tW(CCA)J, tW(CCA)M, or tW(CCA)P were viable but almost lethal while the other quintuple deletions showed moderately impaired growth. Theses growth differences were not obvious among the quadruple deletion strains, which expressed almost one third of mature tRNATrpCCA in the wild type. Therefore, no dosage compensation operates for tRNATrpCCA amount, and growth variations among the quintuple deletion strains may not simply reflect differences in tRNATrpCCA shortage. Yeast may retain the redundancy of tRNATrpCCA genes for a noncanonical function(s) beyond supply of the tRNA to translation.
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Affiliation(s)
- Sachiko Hayashi
- Graduate School of Science, University of Hyogo, Ako-gun, Japan
| | | | | | - Tohru Yoshihisa
- Graduate School of Science, University of Hyogo, Ako-gun, Japan.,Faculty of Science, University of Hyogo
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6
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Sekulovski S, Trowitzsch S. Transfer RNA processing - from a structural and disease perspective. Biol Chem 2022; 403:749-763. [PMID: 35728022 DOI: 10.1515/hsz-2021-0406] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 05/24/2022] [Indexed: 01/05/2023]
Abstract
Transfer RNAs (tRNAs) are highly structured non-coding RNAs which play key roles in translation and cellular homeostasis. tRNAs are initially transcribed as precursor molecules and mature by tightly controlled, multistep processes that involve the removal of flanking and intervening sequences, over 100 base modifications, addition of non-templated nucleotides and aminoacylation. These molecular events are intertwined with the nucleocytoplasmic shuttling of tRNAs to make them available at translating ribosomes. Defects in tRNA processing are linked to the development of neurodegenerative disorders. Here, we summarize structural aspects of tRNA processing steps with a special emphasis on intron-containing tRNA splicing involving tRNA splicing endonuclease and ligase. Their role in neurological pathologies will be discussed. Identification of novel RNA substrates of the tRNA splicing machinery has uncovered functions unrelated to tRNA processing. Future structural and biochemical studies will unravel their mechanistic underpinnings and deepen our understanding of neurological diseases.
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Affiliation(s)
- Samoil Sekulovski
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Strasse 9, D-60438 Frankfurt/Main, Germany
| | - Simon Trowitzsch
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Strasse 9, D-60438 Frankfurt/Main, Germany
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7
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Lai LB, Lai SM, Szymanski ES, Kapur M, Choi EK, Al-Hashimi HM, Ackerman SL, Gopalan V. Structural basis for impaired 5' processing of a mutant tRNA associated with defects in neuronal homeostasis. Proc Natl Acad Sci U S A 2022; 119:e2119529119. [PMID: 35238631 PMCID: PMC8915964 DOI: 10.1073/pnas.2119529119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 01/09/2022] [Indexed: 02/06/2023] Open
Abstract
SignificanceUnderstanding and treating neurological disorders are global priorities. Some of these diseases are engendered by mutations that cause defects in the cellular synthesis of transfer RNAs (tRNAs), which function as adapter molecules that translate messenger RNAs into proteins. During tRNA biogenesis, ribonuclease P catalyzes removal of the transcribed sequence upstream of the mature tRNA. Here, we focus on a cytoplasmic tRNAArgUCU that is expressed specifically in neurons and, when harboring a particular point mutation, contributes to neurodegeneration in mice. Our results suggest that this mutation favors stable alternative structures that are not cleaved by mouse ribonuclease P and motivate a paradigm that may help to understand the molecular basis for disease-associated mutations in other tRNAs.
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Affiliation(s)
- Lien B. Lai
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Stella M. Lai
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Eric S. Szymanski
- Department of Biochemistry, School of Medicine, Duke University, Durham, NC 27710
| | - Mridu Kapur
- Department of Cellular and Molecular Medicine, Section of Neurobiology, University of California San Diego, La Jolla, CA 92093
- Howard Hughes Medical Institute, University of California San Diego, La Jolla, CA 92093
| | - Edric K. Choi
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
| | - Hashim M. Al-Hashimi
- Department of Biochemistry, School of Medicine, Duke University, Durham, NC 27710
| | - Susan L. Ackerman
- Department of Cellular and Molecular Medicine, Section of Neurobiology, University of California San Diego, La Jolla, CA 92093
- Howard Hughes Medical Institute, University of California San Diego, La Jolla, CA 92093
| | - Venkat Gopalan
- Department of Chemistry & Biochemistry, The Ohio State University, Columbus, OH 43210
- Center for RNA Biology, The Ohio State University, Columbus, OH 43210
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8
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Cherkasova V, Iben JR, Pridham KJ, Kessler AC, Maraia RJ. The leucine-NH4+ uptake regulator Any1 limits growth as part of a general amino acid control response to loss of La protein by fission yeast. PLoS One 2021; 16:e0253494. [PMID: 34153074 PMCID: PMC8216550 DOI: 10.1371/journal.pone.0253494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 06/04/2021] [Indexed: 11/19/2022] Open
Abstract
The sla1+ gene of Schizosachharoymces pombe encodes La protein which promotes proper processing of precursor-tRNAs. Deletion of sla1 (sla1Δ) leads to disrupted tRNA processing and sensitivity to target of rapamycin (TOR) inhibition. Consistent with this, media containing NH4+ inhibits leucine uptake and growth of sla1Δ cells. Here, transcriptome analysis reveals that genes upregulated in sla1Δ cells exhibit highly significant overalp with general amino acid control (GAAC) genes in relevant transcriptomes from other studies. Growth in NH4+ media leads to additional induced genes that are part of a core environmental stress response (CESR). The sla1Δ GAAC response adds to evidence linking tRNA homeostasis and broad signaling in S. pombe. We provide evidence that deletion of the Rrp6 subunit of the nuclear exosome selectively dampens a subset of GAAC genes in sla1Δ cells suggesting that nuclear surveillance-mediated signaling occurs in S. pombe. To study the NH4+-effects, we isolated sla1Δ spontaneous revertants (SSR) of the slow growth phenotype and found that GAAC gene expression and rapamycin hypersensitivity were also reversed. Genome sequencing identified a F32V substitution in Any1, a known negative regulator of NH4+-sensitive leucine uptake linked to TOR. We show that 3H-leucine uptake by SSR-any1-F32V cells in NH4+-media is more robust than by sla1Δ cells. Moreover, F32V may alter any1+ function in sla1Δ vs. sla1+ cells in a distinctive way. Thus deletion of La, a tRNA processing factor leads to a GAAC response involving reprogramming of amino acid metabolism, and isolation of the any1-F32V rescuing mutant provides an additional specific link.
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Affiliation(s)
- Vera Cherkasova
- Kelly@DeWitt, Inc, National Library of Medicine, National Institutes of Health, Bethesda, MD, United States of America
| | - James R. Iben
- Molecular Genomics Core, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States of America
| | - Kevin J. Pridham
- Fralin Biomedical Research Institute at Virginia Tech, Roanoke, VA, United States of America
| | - Alan C. Kessler
- Section on Molecular and Cell Biology, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD United States of America
| | - Richard J. Maraia
- Section on Molecular and Cell Biology, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD United States of America
- * E-mail:
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9
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Arimbasseri GA. Interactions between RNAP III transcription machinery and tRNA processing factors. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2018; 1861:354-360. [PMID: 29428193 DOI: 10.1016/j.bbagrm.2018.02.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 02/06/2018] [Accepted: 02/06/2018] [Indexed: 10/18/2022]
Abstract
Eukaryotes have at least three nuclear RNA polymerases to carry out transcription. While RNA polymerases I and II are responsible for ribosomal RNA transcription and messenger RNA transcription, respectively, RNA Polymerase III transcribes approximately up to 300 nt long noncoding RNAs, including tRNA. For all three RNAPs, the nascent transcripts generated undergo extensive post-transcriptional processing. Transcription of mRNAs by RNAP II and their processing are coupled with the aid of the C-terminal domain of the RNAP II. RNAP I transcription and the processing of its transcripts are co-localized to the nucleolus and to some extent, rRNA processing occurs co-transcriptionally. Here, I review the current evidence for the interaction between tRNA processing factors and RNA polymerase III. These interactions include the moonlighting functions of tRNA processing factors in RNAP III transcription and the indirect effect of tRNA transcription levels on tRNA modification machinery.
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Affiliation(s)
- G Aneeshkumar Arimbasseri
- Molecular Genetics Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
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10
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Blewett NH, Maraia RJ. La involvement in tRNA and other RNA processing events including differences among yeast and other eukaryotes. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2018; 1861:361-372. [PMID: 29397330 DOI: 10.1016/j.bbagrm.2018.01.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 12/29/2017] [Accepted: 01/17/2018] [Indexed: 10/25/2022]
Abstract
The conserved nuclear RNA-binding factor known as La protein arose in an ancient eukaryote, phylogenetically associated with another eukaryotic hallmark, synthesis of tRNA by RNA polymerase III (RNAP III). Because 3'-oligo(U) is the sequence-specific signal for transcription termination by RNAP III as well as the high affinity binding site for La, the latter is linked to the intranuclear posttranscriptional processing of eukaryotic precursor-tRNAs. The pre-tRNA processing pathway must accommodate a variety of substrates that are destined for both common steps as well as tRNA-specific events. The order of intranuclear pre-tRNA processing steps is mediated in part by three activities derived from interaction with La protein: 3'-end protection from untimely decay by 3' exonucleases, nuclear retention and chaperone activity that helps prevent pre-tRNA misfolding and mischanneling into offline pathways. A focus of this perspective will be on differences between yeast and mammals in the subcellular partitioning of pre-tRNA intermediates and differential interactions with La. We review how this is most relevant to pre-tRNA splicing which occurs in the cytoplasm of yeasts but in nuclei of higher eukaryotes. Also divergent is La architecture, comprised of three RNA-binding domains in organisms in all examined branches of the eukaryal tree except yeast, which have lost the C-terminal RNA recognition motif-2α (RRM2α) domain. We also review emerging data that suggest mammalian La interacts with nuclear pre-tRNA splicing intermediates and may impact this branch of the tRNA maturation pathway. Finally, because La is involved in intranuclear tRNA biogenesis we review relevant aspects of tRNA-associated neurodegenerative diseases. This article is part of a Special Issue entitled: SI: Regulation of tRNA synthesis and modification in physiological conditions and disease edited by Dr. Boguta Magdalena.
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Affiliation(s)
- Nathan H Blewett
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Richard J Maraia
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA; Commissioned Corps, U.S. Public Health Service, Rockville, MD, USA.
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11
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Ohira T, Suzuki T. Precursors of tRNAs are stabilized by methylguanosine cap structures. Nat Chem Biol 2016; 12:648-55. [PMID: 27348091 DOI: 10.1038/nchembio.2117] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 05/20/2016] [Indexed: 01/30/2023]
Abstract
Efficient maturation of transfer RNAs (tRNAs) is required for rapid cell growth. However, the precise timing of tRNA processing in coordination with the order of tRNA modifications has not been thoroughly elucidated. To analyze the modification status of tRNA precursors (pre-tRNAs) during maturation, we isolated pre-tRNAs at various stages from Saccharomyces cerevisiae and subjected them to MS analysis. We detected methylated guanosine cap structures at the 5' termini of pre-tRNAs bearing 5' leader sequences. These capped pre-tRNAs accumulated substantially after inhibition of RNase P activity. Upon depletion of the capping enzyme Ceg1p, the steady state level of capped pre-tRNA was markedly reduced. In addition, a population of capped pre-tRNAs accumulated in strains in which 5' exonucleases were inhibited, indicating that the 5' cap structures protect pre-tRNAs from 5'-exonucleolytic degradation during maturation.
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Affiliation(s)
- Takayuki Ohira
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan
| | - Tsutomu Suzuki
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan
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12
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Foretek D, Wu J, Hopper AK, Boguta M. Control of Saccharomyces cerevisiae pre-tRNA processing by environmental conditions. RNA (NEW YORK, N.Y.) 2016; 22:339-49. [PMID: 26729922 PMCID: PMC4748812 DOI: 10.1261/rna.054973.115] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 11/17/2015] [Indexed: 05/21/2023]
Abstract
tRNA is essential for translation and decoding of the proteome. The yeast proteome responds to stress and tRNA biosynthesis contributes in this response by repression of tRNA transcription and alterations of tRNA modification. Here we report that the stress response also involves processing of pre-tRNA 3' termini. By a combination of Northern analyses and RNA sequencing, we show that upon shift to elevated temperatures and/or to glycerol-containing medium, aberrant pre-tRNAs accumulate in yeast cells. For pre-tRNAUAU(Ile) and pre-tRNAUUU Lys) these aberrant forms are unprocessed at the 5' ends, but they possess extended 3' termini. Sequencing analyses showed that partial 3' processing precedes 5' processing for pre-tRNAUAU(Ile). An aberrant pre-tRNA(Tyr) that accumulates also possesses extended 3' termini, but it is processed at the 5' terminus. Similar forms of these aberrant pre-tRNAs are detected in the rex1Δ strain that is defective in 3' exonucleolytic trimming of pre-tRNAs but are absent in the lhp1Δ mutant lacking 3' end protection. We further show direct correlation between the inhibition of 3' end processing rate and the stringency of growth conditions. Moreover, under stress conditions Rex1 nuclease seems to be limiting for 3' end processing, by decreased availability linked to increased protection by Lhp1. Thus, our data document complex 3' processing that is inhibited by stress in a tRNA-type and condition-specific manner. This stress-responsive tRNA 3' end maturation process presumably contributes to fine-tune the levels of functional tRNA in budding yeast in response to environmental conditions.
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Affiliation(s)
- Dominika Foretek
- Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Jingyan Wu
- Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, Ohio 43210, USA
| | - Anita K Hopper
- Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, Ohio 43210, USA
| | - Magdalena Boguta
- Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
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13
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Rijal K, Maraia RJ, Arimbasseri AG. A methods review on use of nonsense suppression to study 3' end formation and other aspects of tRNA biogenesis. Gene 2014; 556:35-50. [PMID: 25447915 DOI: 10.1016/j.gene.2014.11.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 11/13/2014] [Accepted: 11/14/2014] [Indexed: 12/26/2022]
Abstract
Suppressor tRNAs bear anticodon mutations that allow them to decode premature stop codons in metabolic marker gene mRNAs, that can be used as in vivo reporters of functional tRNA biogenesis. Here, we review key components of a suppressor tRNA system specific to Schizosaccharomyces pombe and its adaptations for use to study specific steps in tRNA biogenesis. Eukaryotic tRNA biogenesis begins with transcription initiation by RNA polymerase (pol) III. The nascent pre-tRNAs must undergo folding, 5' and 3' processing to remove the leader and trailer, nuclear export, and splicing if applicable, while multiple complex chemical modifications occur throughout the process. We review evidence that precursor-tRNA processing begins with transcription termination at the oligo(T) terminator element, which forms a 3' oligo(U) tract on the nascent RNA, a sequence-specific binding site for the RNA chaperone, La protein. The processing pathway bifurcates depending on a poorly understood property of pol III termination that determines the 3' oligo(U) length and therefore the affinity for La. We thus review the pol III termination process and the factors involved including advances using gene-specific random mutagenesis by dNTP analogs that identify key residues important for transcription termination in certain pol III subunits. The review ends with a 'technical approaches' section that includes a parts lists of suppressor-tRNA alleles, strains and plasmids, and graphic examples of its diverse uses.
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Affiliation(s)
- Keshab Rijal
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Richard J Maraia
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
| | - Aneeshkumar G Arimbasseri
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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14
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Skowronek E, Grzechnik P, Späth B, Marchfelder A, Kufel J. tRNA 3' processing in yeast involves tRNase Z, Rex1, and Rrp6. RNA (NEW YORK, N.Y.) 2014; 20:115-30. [PMID: 24249226 PMCID: PMC3866640 DOI: 10.1261/rna.041467.113] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 10/24/2013] [Indexed: 05/20/2023]
Abstract
Mature tRNA 3' ends in the yeast Saccharomyces cerevisiae are generated by two pathways: endonucleolytic and exonucleolytic. Although two exonucleases, Rex1 and Rrp6, have been shown to be responsible for the exonucleolytic trimming, the identity of the endonuclease has been inferred from other systems but not confirmed in vivo. Here, we show that the yeast tRNA 3' endonuclease tRNase Z, Trz1, is catalyzing endonucleolytic tRNA 3' processing. The majority of analyzed tRNAs utilize both pathways, with a preference for the endonucleolytic one. However, 3'-end processing of precursors with long 3' trailers depends to a greater extent on Trz1. In addition to its function in the nucleus, Trz1 processes the 3' ends of mitochondrial tRNAs, contributing to the general RNA metabolism in this organelle.
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Affiliation(s)
- Ewa Skowronek
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
| | - Pawel Grzechnik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
| | - Bettina Späth
- Molekulare Botanik, Universität Ulm, 89069 Ulm, Germany
| | | | - Joanna Kufel
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
- Corresponding authorE-mail
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15
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Gaidamakov S, Maximova OA, Chon H, Blewett NH, Wang H, Crawford AK, Day A, Tulchin N, Crouch RJ, Morse HC, Blitzer RD, Maraia RJ. Targeted deletion of the gene encoding the La autoantigen (Sjögren's syndrome antigen B) in B cells or the frontal brain causes extensive tissue loss. Mol Cell Biol 2014; 34:123-31. [PMID: 24190965 PMCID: PMC3911279 DOI: 10.1128/mcb.01010-13] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 09/09/2013] [Accepted: 10/23/2013] [Indexed: 11/20/2022] Open
Abstract
La antigen (Sjögren's syndrome antigen B) is a phosphoprotein associated with nascent precursor tRNAs and other RNAs, and it is targeted by autoantibodies in patients with Sjögren's syndrome, systemic lupus erythematosus, and neonatal lupus. Increased levels of La are associated with leukemias and other cancers, and various viruses usurp La to promote their replication. Yeast cells (Saccharomyces cerevisiae and Schizosaccharomyces pombe) genetically depleted of La grow and proliferate, whereas deletion from mice causes early embryonic lethality, raising the question of whether La is required by mammalian cells generally or only to surpass a developmental stage. We developed a conditional La allele and used it in mice that express Cre recombinase in either B cell progenitors or the forebrain. B cell Mb1(Cre) La-deleted mice produce no B cells. Consistent with αCamKII Cre, which induces deletion in hippocampal CA1 cells in the third postnatal week and later throughout the neocortex, brains develop normally in La-deleted mice until ∼5 weeks and then lose a large amount of forebrain cells and mass, with evidence of altered pre-tRNA processing. The data indicate that La is required not only in proliferating cells but also in nondividing postmitotic cells. Thus, La is essential in different cell types and required for normal development of various tissue types.
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Affiliation(s)
- Sergei Gaidamakov
- Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Olga A. Maximova
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Hyongi Chon
- Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Nathan H. Blewett
- Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Hongsheng Wang
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Amanda K. Crawford
- Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Amanda Day
- Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Natalie Tulchin
- Department of Pathology, Mount Sinai School of Medicine, New York, New York, USA
| | - Robert J. Crouch
- Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Herbert C. Morse
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Robert D. Blitzer
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, New York, USA
| | - Richard J. Maraia
- Intramural Research Programs of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
- Commissioned Corps, U.S. Public Health Service, Washington, DC, USA
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16
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Retrograde transfer RNA nuclear import provides a new level of tRNA quality control in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2013; 110:21042-7. [PMID: 24297920 DOI: 10.1073/pnas.1316579110] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In eukaryotes, transfer RNAs (tRNAs) are transcribed in the nucleus yet function in the cytoplasm; thus, tRNA movement within the cell was believed to be unidirectional--from the nucleus to the cytoplasm. It is now known that mature tRNAs also move in a retrograde direction from the cytoplasm to the nucleus via retrograde tRNA nuclear import, a process that is conserved from yeast to vertebrates. The biological significance of this tRNA nuclear import is not entirely clear. We hypothesized that retrograde tRNA nuclear import might function in proofreading tRNAs to ensure that only proper tRNAs reside in the cytoplasm and interact with the translational machinery. Here we identify two major types of aberrant tRNAs in yeast: a 5', 3' end-extended, spliced tRNA and hypomodified tRNAs. We show that both types of aberrant tRNAs accumulate in mutant cells that are defective in tRNA nuclear traffic, suggesting that they are normally imported into the nucleus and are repaired or degraded. The retrograde pathway functions in parallel with the cytoplasmic rapid tRNA decay pathway previously demonstrated to monitor tRNA quality, and cells are not viable if they lack both pathways. Our data support the hypothesis that the retrograde process provides a newly discovered level of tRNA quality control as a pathway that monitors both end processing of pre-tRNAs and the modification state of mature tRNAs.
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17
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Wichtowska D, Turowski TW, Boguta M. An interplay between transcription, processing, and degradation determines tRNA levels in yeast. WILEY INTERDISCIPLINARY REVIEWS-RNA 2013; 4:709-22. [PMID: 24039171 DOI: 10.1002/wrna.1190] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 07/09/2013] [Accepted: 07/10/2013] [Indexed: 11/06/2022]
Abstract
tRNA biogenesis in yeast involves the synthesis of the initial transcript by RNA polymerase III followed by processing and controlled degradation in both the nucleus and the cytoplasm. A vast landscape of regulatory elements controlling tRNA stability in yeast has emerged from recent studies. Diverse pathways of tRNA maturation generate multiple stable and unstable intermediates. A significant impact on tRNA stability is exerted by a variety of nucleotide modifications. Pre-tRNAs are targets of exosome-dependent surveillance in the nucleus. Some tRNAs that are hypomodified or bear specific destabilizing mutations are directed to the rapid tRNA decay pathway leading to 5'→3' exonucleolytic degradation by Rat1 and Xrn1. tRNA molecules are selectively marked for degradation by a double CCA at their 3' ends. In addition, under different stress conditions, tRNA half-molecules can be generated by independent endonucleolytic cleavage events. Recent studies reveal unexpected relationships between the subsequent steps of tRNA biosynthesis and the mechanisms controlling its quality and turnover.
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Affiliation(s)
- Dominika Wichtowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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18
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Maraia RJ, Lamichhane TN. 3' processing of eukaryotic precursor tRNAs. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 2:362-75. [PMID: 21572561 DOI: 10.1002/wrna.64] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Biogenesis of eukaryotic tRNAs requires transcription by RNA polymerase III and subsequent processing. 5' processing of precursor tRNA occurs by a single mechanism, cleavage by RNase P, and usually occurs before 3' processing although some conditions allow observation of the 3'-first pathway. 3' processing is relatively complex and is the focus of this review. Precursor RNA 3'-end formation begins with pol III termination generating a variable length 3'-oligo(U) tract that represents an underappreciated and previously unreviewed determinant of processing. Evidence that the pol III-intrinsic 3'exonuclease activity mediated by Rpc11p affects 3'oligo(U) length is reviewed. In addition to multiple 3' nucleases, precursor tRNA(pre-tRNA) processing involves La and Lsm, distinct oligo(U)-binding proteins with proposed chaperone activities. 3' processing is performed by the endonuclease RNase Z or the exonuclease Rex1p (possibly others) along alternate pathways conditional on La. We review a Schizosaccharomyces pombe tRNA reporter system that has been used to distinguish two chaperone activities of La protein to its two conserved RNA binding motifs. Pre-tRNAs with structural impairments are degraded by a nuclear surveillance system that mediates polyadenylation by the TRAMP complex followed by 3'-digestion by the nuclear exosome which appears to compete with 3' processing. We also try to reconcile limited data on pre-tRNA processing and Lsm proteins which largely affect precursors but not mature tRNAs.A pathway is proposed in which 3' oligo(U) length is a primary determinant of La binding with subsequent steps distinguished by 3'-endo versus exo nucleases,chaperone activities, and nuclear surveillance.
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Affiliation(s)
- Richard J Maraia
- Intramural Research Program, Eunice Kennedy Shriver NationalInstitute of Child Health and Human Development, NationalInstitutes of Health, Bethesda, MD, USA.
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19
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Karkusiewicz I, Turowski TW, Graczyk D, Towpik J, Dhungel N, Hopper AK, Boguta M. Maf1 protein, repressor of RNA polymerase III, indirectly affects tRNA processing. J Biol Chem 2011; 286:39478-88. [PMID: 21940626 DOI: 10.1074/jbc.m111.253310] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Maf1 is negative regulator of RNA polymerase III in yeast. We observed high levels of both primary transcript and end-matured, intron-containing pre-tRNAs in the maf1Δ strain. This pre-tRNA accumulation could be overcome by transcription inhibition, arguing against a direct role of Maf1 in tRNA maturation and suggesting saturation of processing machinery by the increased amounts of primary transcripts. Saturation of the tRNA exportin, Los1, is one reason why end-matured intron-containing pre-tRNAs accumulate in maf1Δ cells. However, it is likely possible that other components of the processing pathway are also limiting when tRNA transcription is increased. According to our model, Maf1-mediated transcription control and nuclear export by Los1 are two major stages of tRNA biosynthesis that are regulated by environmental conditions in a coordinated manner.
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Affiliation(s)
- Iwona Karkusiewicz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02 106 Warsaw, Poland
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20
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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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21
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Bayfield MA, Yang R, Maraia RJ. Conserved and divergent features of the structure and function of La and La-related proteins (LARPs). BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1799:365-78. [PMID: 20138158 PMCID: PMC2860065 DOI: 10.1016/j.bbagrm.2010.01.011] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 01/08/2010] [Accepted: 01/27/2010] [Indexed: 12/19/2022]
Abstract
Genuine La proteins contain two RNA binding motifs, a La motif (LAM) followed by a RNA recognition motif (RRM), arranged in a unique way to bind RNA. These proteins interact with an extensive variety of cellular RNAs and exhibit activities in two broad categories: i) to promote the metabolism of nascent pol III transcripts, including precursor-tRNAs, by binding to their common, UUU-3'OH containing ends, and ii) to modulate the translation of certain mRNAs involving an unknown binding mechanism. Characterization of several La-RNA crystal structures as well as biochemical studies reveal insight into their unique two-motif domain architecture and how the LAM recognizes UUU-3'OH while the RRM binds other parts of a pre-tRNA. Recent studies of members of distinct families of conserved La-related proteins (LARPs) indicate that some of these harbor activity related to genuine La proteins, suggesting that their UUU-3'OH binding mode has been appropriated for the assembly and regulation of a specific snRNP (e.g., 7SK snRNP assembly by hLARP7/PIP7S). Analyses of other LARP family members suggest more diverged RNA binding modes and specialization for cytoplasmic mRNA-related functions. Thus it appears that while genuine La proteins exhibit broad general involvement in both snRNA-related and mRNA-related functions, different LARP families may have evolved specialized activities in either snRNA or mRNA-related functions. In this review, we summarize recent progress that has led to greater understanding of the structure and function of La proteins and their roles in tRNA processing and RNP assembly dynamics, as well as progress on the different LARPs.
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Affiliation(s)
- Mark A Bayfield
- Department of Biology, York University, Toronto, ON, Canada.
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22
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Hopper AK, Pai DA, Engelke DR. Cellular dynamics of tRNAs and their genes. FEBS Lett 2009; 584:310-7. [PMID: 19931532 DOI: 10.1016/j.febslet.2009.11.053] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 11/10/2009] [Accepted: 11/13/2009] [Indexed: 10/20/2022]
Abstract
This discussion focuses on the cellular dynamics of tRNA transcription, processing, and turnover. Early tRNA biosynthesis steps are shared among most tRNAs, while later ones are often individualized for specific tRNAs. In yeast, tRNA transcription and early processing occur coordinately in the nucleolus, requiring topological arrangement of approximately 300 tRNA genes and early processing enzymes to this site; later processing events occur in the nucleoplasm or cytoplasm. tRNA nuclear export requires multiple exporters which function in parallel and the export process is coupled with other cellular events. Nuclear-cytoplasmic tRNA subcellular movement is not unidirectional as a retrograde pathway delivers mature cytoplasmic tRNAs to the nucleus. Despite the long half-lives, there are multiple pathways to turnover damaged tRNAs or normal tRNAs upon cellular stress.
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Affiliation(s)
- Anita K Hopper
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, 484 W. 12th Ave., Room Riffe 800, Columbus, OH 43210, USA.
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23
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Functional conservation of tRNase ZL among Saccharomyces cerevisiae, Schizosaccharomyces pombe and humans. Biochem J 2009; 422:483-92. [PMID: 19555350 DOI: 10.1042/bj20090743] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Although tRNase Z from various organisms was shown to process nuclear tRNA 3' ends in vitro, only a very limited number of studies have reported its in vivo biological functions. tRNase Z is present in a short form, tRNase Z(S), and a long form, tRNase Z(L). Unlike Saccharomyces cerevisiae, which contains one tRNase Z(L) gene (scTRZ1) and humans, which contain one tRNase Z(L) encoded by the prostate-cancer susceptibility gene ELAC2 and one tRNase Z(S), Schizosaccharomyces pombe contains two tRNase Z(L) genes, designated sptrz1(+) and sptrz2(+). We report that both sptrz1(+) and sptrz2(+) are essential for growth. Moreover, sptrz1(+) is required for cell viability in the absence of Sla1p, which is thought to be required for endonuclease-mediated maturation of pre-tRNA 3' ends in yeast. Both scTRZ1 and ELAC2 can complement a temperature-sensitive allele of sptrz1(+), sptrz1-1, but not the sptrz1 null mutant, indicating that despite exhibiting species specificity, tRNase Z(L)s are functionally conserved among S. cerevisiae, S. pombe and humans. Overexpression of sptrz1(+), scTRZ1 and ELAC2 can increase suppression of the UGA nonsense mutation ade6-704 through facilitating 3' end processing of the defective suppressor tRNA that mediates suppression. Our findings reveal that 3' end processing is a limiting step for defective tRNA maturation and demonstrate that overexpression of sptrz1(+), scTRZ1 and ELAC2 can promote defective tRNA 3' processing in vivo. Our results also support the notion that yeast tRNase Z(L) is absolutely required for 3' end processing of at least a few pre-tRNAs even in the absence of Sla1p.
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24
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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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25
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Gaston KW, Rubio MAT, Spears JL, Pastar I, Papavasiliou FN, Alfonzo JD. C to U editing at position 32 of the anticodon loop precedes tRNA 5' leader removal in trypanosomatids. Nucleic Acids Res 2007; 35:6740-9. [PMID: 17916576 PMCID: PMC2175311 DOI: 10.1093/nar/gkm745] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In all organisms, precursor tRNAs are processed into mature functional units by post-transcriptional changes. These involve 5′ and 3′ end trimming as well as the addition of a significant number of chemical modifications, including RNA editing. The only known example of non-organellar C to U editing of tRNAs occurs in trypanosomatids. In this system, editing at position 32 of the anticodon loop of tRNAThr(AGU) stimulates, but is not required for, the subsequent formation of inosine at position 34. In the present work, we expand the number of C to U edited tRNAs to include all the threonyl tRNA isoacceptors. Notably, the absence of a naturally encoded adenosine, at position 34, in two of these isoacceptors demonstrates that A to I is not required for C to U editing. We also show that C to U editing is a nuclear event while A to I is cytoplasmic, where C to U editing at position 32 occurs in the precursor tRNA prior to 5′ leader removal. Our data supports the view that C to U editing is more widespread than previously thought and is part of a stepwise process in the maturation of tRNAs in these organisms.
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Affiliation(s)
- Kirk W Gaston
- Department of Microbiology, The Ohio State RNA Group, The Ohio State University, Columbus, Ohio 43210, USA
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26
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Fleurdépine S, Deragon JM, Devic M, Guilleminot J, Bousquet-Antonelli C. A bona fide La protein is required for embryogenesis in Arabidopsis thaliana. Nucleic Acids Res 2007; 35:3306-21. [PMID: 17459889 PMCID: PMC1904278 DOI: 10.1093/nar/gkm200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 03/21/2007] [Accepted: 03/21/2007] [Indexed: 01/28/2023] Open
Abstract
Searches in the Arabidopsis thaliana genome using the La motif as query revealed the presence of eight La or La-like proteins. Using structural and phylogenetic criteria, we identified two putative genuine La proteins (At32 and At79) and showed that both are expressed throughout plant development but at different levels and under different regulatory conditions. At32, but not At79, restores Saccharomyces cerevisiae La nuclear functions in non-coding RNAs biogenesis and is able to bind to plant 3'-UUU-OH RNAs. We conclude that these La nuclear functions are conserved in Arabidopsis and supported by At32, which we renamed as AtLa1. Consistently, AtLa1 is predominantly localized to the plant nucleoplasm and was also detected in the nucleolar cavity. The inactivation of AtLa1 in Arabidopsis leads to an embryonic-lethal phenotype with deficient embryos arrested at early globular stage of development. In addition, mutant embryonic cells display a nucleolar hypertrophy suggesting that AtLa1 is required for normal ribosome biogenesis. The identification of two distantly related proteins with all structural characteristics of genuine La proteins suggests that these factors evolved to a certain level of specialization in plants. This unprecedented situation provides a unique opportunity to dissect the very different aspects of this crucial cellular activity.
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Affiliation(s)
- Sophie Fleurdépine
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Jean-Marc Deragon
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Martine Devic
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Jocelyne Guilleminot
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Cécile Bousquet-Antonelli
- CNRS UMR6547 GEEM, Université Blaise Pascal, 63177 Aubière, France and CNRS UMR5096 LGDP, Université de Perpignan Via Domitia, 66860 Perpignan, France
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27
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Behm-Ansmant I, Massenet S, Immel F, Patton JR, Motorin Y, Branlant C. A previously unidentified activity of yeast and mouse RNA:pseudouridine synthases 1 (Pus1p) on tRNAs. RNA (NEW YORK, N.Y.) 2006; 12:1583-93. [PMID: 16804160 PMCID: PMC1524882 DOI: 10.1261/rna.100806] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Mouse pseudouridine synthase 1 (mPus1p) was the first vertebrate RNA:pseudouridine synthase that was cloned and characterized biochemically. The mPus1p was previously found to catalyze Psi formation at positions 27, 28, 34, and 36 in in vitro produced yeast and human tRNAs. On the other hand, the homologous Saccharomyces cerevisiae scPus1p protein was shown to modify seven uridine residues in tRNAs (26, 27, 28, 34, 36, 65, and 67) and U44 in U2 snRNA. In this work, we expressed mPus1p in yeast cells lacking scPus1p and studied modification of U2 snRNA and several yeast tRNAs. Our data showed that, in these in vivo conditions, the mouse enzyme efficiently modifies yeast U2 snRNA at position 44 and tRNAs at positions 27, 28, 34, and 36. However, a tRNA:Psi26-synthase activity of mPus1p was not observed. Furthermore, we found that both scPus1p and mPus1p, in vivo and in vitro, have a previously unidentified activity at position 1 in cytoplasmic tRNAArg(ACG). This modification can take place in mature tRNA, as well as in pre-tRNAs with 5' and/or 3' extensions. Thus, we identified the protein carrying one of the last missing yeast tRNA:Psi synthase activities. In addition, our results reveal an additional activity of mPus1p at position 30 in tRNA that scPus1p does not possess.
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Affiliation(s)
- Isabelle Behm-Ansmant
- Laboratoire de Maturation des ARN et Enzymologie Moléculaire, UMR 7567 CNRS-UHP, Nancy I, Faculté des Sciences, BP 239, 54506 Vandoeuvre-les-Nancy Cedex, France
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28
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Kassavetis GA, Steiner DF. Nhp6 is a transcriptional initiation fidelity factor for RNA polymerase III transcription in vitro and in vivo. J Biol Chem 2006; 281:7445-51. [PMID: 16407207 DOI: 10.1074/jbc.m512810200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The binding of the RNA polymerase III (pol III) transcription factor TFIIIC to the box A intragenic promoter element of tRNA genes specifies the placement of TFIIIB on upstream-lying DNA. In turn, TFIIIB recruits pol III to the promoter and specifies transcription initiating 17-19 base pairs upstream of box A. The resolution of the pol III transcription apparatus into recombinant TFIIIB, highly purified TFIIIC, and pol III is accompanied by a loss of precision in specifying where transcription initiation occurs due to heterogeneous placement of TFIIIB. In this paper we show that Nhp6a, an abundant high mobility group B (HMGB) family, non-sequence-specific DNA-binding protein in Saccharomyces cerevisiae restores transcriptional initiation fidelity to this highly purified in vitro system. Restoration of initiation fidelity requires the presence of Nhp6a prior to TFIIIB-DNA complex formation. Chemical nuclease footprinting of TFIIIC- and TFIIIB-TFIIIC-DNA complexes reveals that Nhp6a markedly alters the TFIIIC footprint over box A and reduces the size of the TFIIIB footprint on upstream DNA sequence. Analyses of unprocessed tRNAs from yeast lacking Nhp6a and its closely related paralogue Nhp6b demonstrate that Nhp6 is required for transcriptional initiation fidelity of some but not all tRNA genes, in vivo.
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Affiliation(s)
- George A Kassavetis
- Division of Biological Sciences and Center for Molecular Genetics, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA.
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29
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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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Foldynová-Trantírková S, Paris Z, Sturm NR, Campbell DA, Lukes J. The Trypanosoma brucei La protein is a candidate poly(U) shield that impacts spliced leader RNA maturation and tRNA intron removal. Int J Parasitol 2005; 35:359-66. [PMID: 15777912 DOI: 10.1016/j.ijpara.2004.12.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2004] [Revised: 12/17/2004] [Accepted: 12/17/2004] [Indexed: 10/25/2022]
Abstract
By virtue of its preferential binding to poly(U) tails on small RNA precursors and nuclear localisation motif, the La protein has been implicated for a role in the stabilisation and nuclear retention of processing intermediates for a variety of small RNAs in eukaryotic cells. As the universal substrate for trans-splicing, the spliced leader RNA is transcribed as a precursor with just such a tail. La protein was targeted for selective knockdown by inducible RNA interference in Trypanosoma brucei. Of three RNA interference strategies employed, a p2T7-177 vector was the most effective in reducing both the La mRNA as well as the protein itself from induced cells. In the relative absence of La protein T. brucei cells were not viable, in contrast to La gene knockouts in yeast. A variety of potential small RNA substrates were examined under induction, including spliced leader RNA, spliced leader associated RNA, the U1, U2, U4, and U6 small nuclear RNAs, 5S ribosomal RNA, U3 small nucleolar RNA, and tRNATyr. None of these molecules showed significant variance in size or abundance in their mature forms, although a discrete subset of intermediates appear for spliced leader RNA and tRNATyr intron splicing under La depletion conditions. 5'-end methylation in the spliced leader RNA and U1 small nuclear RNA was unaffected. The immediate cause of lethality in T. brucei was not apparent, but may represent a cumulative effect of multiple defects including processing of spliced leader RNA, tRNATyr and other unidentified RNA substrates. This study indicates that La protein binding is not essential for maturation of the spliced leader RNA, but does not rule out the presence of an alternative processing pathway that could compensate for the absence of normally-associated La protein.
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Affiliation(s)
- Silvie Foldynová-Trantírková
- Institute of Parasitology, Czech Academy of Sciences, Faculty of Biology, University of South Bohemia, 37005 Ceské Budejovice, Czech Republic
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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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Huang Y, Intine RV, Mozlin A, Hasson S, Maraia RJ. Mutations in the RNA polymerase III subunit Rpc11p that decrease RNA 3' cleavage activity increase 3'-terminal oligo(U) length and La-dependent tRNA processing. Mol Cell Biol 2005; 25:621-36. [PMID: 15632064 PMCID: PMC543423 DOI: 10.1128/mcb.25.2.621-636.2005] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2004] [Revised: 10/01/2004] [Accepted: 10/15/2004] [Indexed: 11/20/2022] Open
Abstract
Termination by RNA polymerase III (Pol III) produces RNAs whose 3' oligo(U) termini are bound by La protein, a chaperone that protects RNAs from 3' exonucleases and promotes their maturation. Multiple reports indicate that yeasts use La-dependent and -independent pathways for tRNA maturation, with defective pre-tRNAs being most sensitive to decay and most dependent on La for maturation and function. The Rpc11p subunit of Pol III shows homology with the zinc ribbon of TFIIS and is known to mediate RNA 3' cleavage and to be important for termination. We used a La-dependent opal suppressor, tRNASerUGAM, which suppresses ade6-704 and the accumulation of red pigment, to screen Schizosaccaromyces pombe for rpc11 mutants that increase tRNA-mediated suppression. Analyses of two zinc ribbon mutants indicate that they are deficient in Pol III RNA 3' cleavage activity and produce pre-tRNASerUGAM transcripts with elongated 3'-oligo(U) tracts that are better substrates for La. A substantial fraction of pre-tRNASerUGAM contains too few 3' Us for efficient La binding and appears to decay in wild-type cells but has elongated oligo(U) tracts and matures along the La-dependent pathway in the mutants. The data indicate that Rpc11p limits RNA 3'-U length and that this significantly restricts pre-tRNAs to a La-independent pathway of maturation in fission yeast.
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Affiliation(s)
- Ying Huang
- Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, NIH, 31 Center Dr., Room 2A25, Bethesda, MD 20892-2426, USA
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Verdone L, Galardi S, Page D, Beggs JD. Lsm proteins promote regeneration of pre-mRNA splicing activity. Curr Biol 2004; 14:1487-91. [PMID: 15324666 DOI: 10.1016/j.cub.2004.08.032] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Revised: 05/29/2004] [Accepted: 06/23/2004] [Indexed: 11/21/2022]
Abstract
Lsm proteins are ubiquitous, multifunctional proteins that affect the processing of most RNAs in eukaryotic cells, but their function is unknown. A complex of seven Lsm proteins, Lsm2-8, associates with the U6 small nuclear RNA (snRNA) that is a component of spliceosome complexes in which pre-mRNA splicing occurs. Spliceosomes contain five snRNAs, U1, U2, U4, U5, and U6, that are packaged as ribonucleoprotein particles (snRNPs). U4 and U6 snRNAs contain extensive sequence complementarity and interact to form U4/U6 di-snRNPs. U4/U6 di-snRNPs associate with U5 snRNPs to form U4/U6.U5 tri-snRNPs prior to spliceosome assembly. Within spliceosomes, disruption of base-paired U4/U6 heterodimer allows U6 snRNA to form part of the catalytic center. Following completion of the splicing reaction, snRNPs must be recycled for subsequent rounds of splicing, although little is known about this process. Here we present evidence that regeneration of splicing activity in vitro is dependent on Lsm proteins. RNP reconstitution experiments with exogenous U6 RNA show that Lsm proteins promote the formation of U6-containing complexes and suggest that Lsm proteins have a chaperone-like function, supporting the assembly or remodeling of RNP complexes involved in splicing. Such a function could explain the involvement of Lsm proteins in a wide variety of RNA processing pathways.
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Affiliation(s)
- Loredana Verdone
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JR, United Kingdom
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Levinger L, Mörl M, Florentz C. Mitochondrial tRNA 3' end metabolism and human disease. Nucleic Acids Res 2004; 32:5430-41. [PMID: 15477393 PMCID: PMC524294 DOI: 10.1093/nar/gkh884] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Over 150 mutations in the mitochondrial genome have been shown to be associated with human disease. Remarkably, two-thirds of them are found in tRNA genes, which constitute only one-tenth of the mitochondrial genome. A total of 22 tRNAs punctuate the genome and are produced together with 11 mRNAs and 2 rRNAs from long polycistronic primary transcripts with almost no spacers. Pre-tRNAs thus require precise endonucleolytic excision. Furthermore, the CCA triplet which forms the 3' end of all tRNAs is not encoded, but must be synthesized by the CCA-adding enzyme after 3' end cleavage. Amino acid attachment to the CCA of mature tRNA is performed by aminoacyl-tRNA synthetases, which, like the preceding processing enzymes, are nuclear-encoded and imported into mitochondria. Here, we critically review the effectiveness and reliability of evidence obtained from reactions with in vitro transcripts that pathogenesis-associated mutant mitochondrial tRNAs can lead to deficiencies in tRNA 3' end metabolism (3' end cleavage, CCA addition and aminoacylation) toward an understanding of molecular mechanisms underlying human tRNA disorders. These defects probably contribute, individually and cumulatively, to the progression of human mitochondrial diseases.
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Affiliation(s)
- Louis Levinger
- York College/CUNY, 94-20 Guy R. Brewer Boulevard, Jamaica, NY 11451, USA.
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Current awareness on yeast. Yeast 2003; 20:837-44. [PMID: 12886942 DOI: 10.1002/yea.946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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MESH Headings
- Active Transport, Cell Nucleus
- Endoribonucleases/metabolism
- Genes, Fungal
- Mitochondria/metabolism
- Models, Biological
- Nucleic Acid Conformation
- Protein Biosynthesis
- RNA Editing
- RNA Processing, Post-Transcriptional
- RNA Splicing
- RNA, Catalytic/metabolism
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Ribonuclease P
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- Anita K Hopper
- Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
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