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Takallou S, Hajikarimlou M, Al-Gafari M, Wang J, Kazmirchuk TDD, Said KB, Samanfar B, Golshani A. The Involvement of YNR069C in Protein Synthesis in the Baker's Yeast, Saccharomyces cerevisiae. BIOLOGY 2024; 13:138. [PMID: 38534408 DOI: 10.3390/biology13030138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/17/2024] [Accepted: 02/19/2024] [Indexed: 03/28/2024]
Abstract
Maintaining translation fidelity is a critical step within the process of gene expression. It requires the involvement of numerous regulatory elements to ensure the synthesis of functional proteins. The efficient termination of protein synthesis can play a crucial role in preserving this fidelity. Here, we report on investigating a protein of unknown function, YNR069C (also known as BSC5), for its activity in the process of translation. We observed a significant increase in the bypass of premature stop codons upon the deletion of YNR069C. Interestingly, the genomic arrangement of this ORF suggests a compatible mode of expression reliant on translational readthrough, incorporating the neighboring open reading frame. We also showed that the deletion of YNR069C results in an increase in the rate of translation. Based on our results, we propose that YNR069C may play a role in translation fidelity, impacting the overall quantity and quality of translation. Our genetic interaction analysis supports our hypothesis, associating the role of YNR069C to the regulation of protein synthesis.
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Affiliation(s)
- Sarah Takallou
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Maryam Hajikarimlou
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Mustafa Al-Gafari
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Jiashu Wang
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Thomas David Daniel Kazmirchuk
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Kamaledin B Said
- Department of Pathology and Microbiology, College of Medicine, University of Hail, Hail 55476, Saudi Arabia
| | - Bahram Samanfar
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre (ORDC), Ottawa, ON K1A 0C6, Canada
| | - Ashkan Golshani
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
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2
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Nørgård MØ, Lund PM, Kalisi N, Andresen TL, Larsen JB, Vogel S, Svenningsen P. Mitochondrial reactive oxygen species modify extracellular vesicles secretion rate. FASEB Bioadv 2023; 5:355-366. [PMID: 37674540 PMCID: PMC10478507 DOI: 10.1096/fba.2023-00053] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/13/2023] [Accepted: 06/21/2023] [Indexed: 09/08/2023] Open
Abstract
Extracellular vesicle (EV) secretion rate is stimulated by hypoxia that causes increased reactive oxygen species (ROS) production by the mitochondrial electron transport chain (ETC) and hypoxia-induced factor (HIF)-1 signaling; however, their contribution to the increased EV secretion rate is unknown. We found that the EV marker secretion rate in our EV reporter cell line CD9truc-EGFP was unaffected by the HIF-1α stabilizer roxadustat; yet, ETC stimulation by dichloroacetic acid (DCA) significantly increased EV secretion. The DCA-induced EV secretion was blocked by the antioxidant TEMPO and rotenone, an inhibitor of the ETC's Complex I. Under hypoxic conditions, the limited oxygen reduction impedes the ETC's Complex III. To mimic this, we inhibited Complex III with antimycin A, which increased ROS-dependent EV secretion. The electron transport between Complex I and III is accomplished by coenzyme Q created by the mevalonate pathway and tyrosine metabolites. Blocking an early step in the mevalonate pathway using pitavastatin augmented the DCA-induced EV secretion, and 4-nitrobenzoate-an inhibitor of the condensation of the mevalonate pathway with tyrosine metabolites-increased ROS-dependent EV secretion. Our findings indicate that hypoxia-mimetics targeting the ETC modify EV secretion and that ROS produced by the ETC is a potent stimulus for EV secretion.
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Affiliation(s)
- Mikkel Ø. Nørgård
- Department of Molecular Medicine, Cardiovascular and Renal ResearchUniversity of Southern DenmarkOdenseDenmark
| | - Philip M. Lund
- Department of Health Technology, Center for Intestinal Absorption and Transport of BiopharmaceuticalsTechnical University of DenmarkKongens LyngbyDenmark
| | - Nazmie Kalisi
- Department of Physics, Chemistry and PharmacyUniversity of Southern DenmarkOdenseDenmark
| | - Thomas L. Andresen
- Department of Health Technology, Center for Intestinal Absorption and Transport of BiopharmaceuticalsTechnical University of DenmarkKongens LyngbyDenmark
| | - Jannik B. Larsen
- Department of Health Technology, Center for Intestinal Absorption and Transport of BiopharmaceuticalsTechnical University of DenmarkKongens LyngbyDenmark
| | - Stefan Vogel
- Department of Physics, Chemistry and PharmacyUniversity of Southern DenmarkOdenseDenmark
| | - Per Svenningsen
- Department of Molecular Medicine, Cardiovascular and Renal ResearchUniversity of Southern DenmarkOdenseDenmark
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3
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Abstract
The study of eukaryotic tRNA processing has given rise to an explosion of new information and insights in the last several years. We now have unprecedented knowledge of each step in the tRNA processing pathway, revealing unexpected twists in biochemical pathways, multiple new connections with regulatory pathways, and numerous biological effects of defects in processing steps that have profound consequences throughout eukaryotes, leading to growth phenotypes in the yeast Saccharomyces cerevisiae and to neurological and other disorders in humans. This review highlights seminal new results within the pathways that comprise the life of a tRNA, from its birth after transcription until its death by decay. We focus on new findings and revelations in each step of the pathway including the end-processing and splicing steps, many of the numerous modifications throughout the main body and anticodon loop of tRNA that are so crucial for tRNA function, the intricate tRNA trafficking pathways, and the quality control decay pathways, as well as the biogenesis and biology of tRNA-derived fragments. We also describe the many interactions of these pathways with signaling and other pathways in the cell.
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Affiliation(s)
- Eric M Phizicky
- Department of Biochemistry and Biophysics and Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York 14642, USA
| | - Anita K Hopper
- Department of Molecular Genetics and Center for RNA Biology, Ohio State University, Columbus, Ohio 43235, USA
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4
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Jagadeesan SK, Al-gafari M, Wang J, Takallou S, Allard D, Hajikarimlou M, Kazmirchuk TDD, Moteshareie H, Said KB, Nokhbeh R, Smith M, Samanfar B, Golshani A. DBP7 and YRF1-6 Are Involved in Cell Sensitivity to LiCl by Regulating the Translation of PGM2 mRNA. Int J Mol Sci 2023; 24:ijms24021785. [PMID: 36675300 PMCID: PMC9864399 DOI: 10.3390/ijms24021785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 01/13/2023] [Accepted: 01/14/2023] [Indexed: 01/17/2023] Open
Abstract
Lithium chloride (LiCl) has been widely researched and utilized as a therapeutic option for bipolar disorder (BD). Several pathways, including cell signaling and signal transduction pathways in mammalian cells, are shown to be regulated by LiCl. LiCl can negatively control the expression and activity of PGM2, a phosphoglucomutase that influences sugar metabolism in yeast. In the presence of galactose, when yeast cells are challenged by LiCl, the phosphoglucomutase activity of PGM2p is decreased, causing an increase in the concentration of toxic galactose metabolism intermediates that result in cell sensitivity. Here, we report that the null yeast mutant strains DBP7∆ and YRF1-6∆ exhibit increased LiCl sensitivity on galactose-containing media. Additionally, we demonstrate that DBP7 and YRF1-6 modulate the translational level of PGM2 mRNA, and the observed alteration in translation seems to be associated with the 5'-untranslated region (UTR) of PGM2 mRNA. Furthermore, we observe that DBP7 and YRF1-6 influence, to varying degrees, the translation of other mRNAs that carry different 5'-UTR secondary structures.
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Affiliation(s)
- Sasi Kumar Jagadeesan
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Mustafa Al-gafari
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Jiashu Wang
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Sarah Takallou
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Danielle Allard
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Maryam Hajikarimlou
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Thomas David Daniel Kazmirchuk
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Houman Moteshareie
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Biotechnology Laboratory, Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Kamaledin B. Said
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Department of Pathology and Microbiology, College of Medicine, University of Hail, Hail 55476, Saudi Arabia
| | - Reza Nokhbeh
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Myron Smith
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Bahram Samanfar
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre (ORDC), Ottawa, ON K1A 0C6, Canada
| | - Ashkan Golshani
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Correspondence:
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5
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Coll-SanMartin L, Davalos V, Piñeyro D, Rosselló-Tortella M, Bueno-Costa A, Setien F, Villanueva A, Granada I, Ruiz-Xiviller N, Kotter A, Helm M, Yokota J, Kawabata-Iwakawa R, Kohno T, Esteller M. Gene Amplification-Associated Overexpression of the Selenoprotein tRNA Enzyme TRIT1 Confers Sensitivity to Arsenic Trioxide in Small-Cell Lung Cancer. Cancers (Basel) 2021; 13:1869. [PMID: 33919717 PMCID: PMC8070726 DOI: 10.3390/cancers13081869] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/06/2021] [Accepted: 04/12/2021] [Indexed: 12/16/2022] Open
Abstract
The alteration of RNA modification patterns is emerging as a common feature of human malignancies. If these changes affect key RNA molecules for mRNA translation, such as transfer RNA, they can have important consequences for cell transformation. TRIT1 is the enzyme responsible for the hypermodification of adenosine 37 in the anticodon region of human tRNAs containing serine and selenocysteine. Herein, we show that TRIT1 undergoes gene amplification-associated overexpression in cancer cell lines and primary samples of small-cell lung cancer. From growth and functional standpoints, the induced depletion of TRIT1 expression in amplified cells reduces their tumorigenic potential and downregulates the selenoprotein transcripts. We observed that TRIT1-amplified cells are sensitive to arsenic trioxide, a compound that regulates selenoproteins, whereas reduction of TRIT1 levels confers loss of sensitivity to the drug. Overall, our results indicate a role for TRIT1 as a small-cell lung cancer-relevant gene that, when undergoing gene amplification-associated activation, can be targeted with the differentiation agent arsenic trioxide.
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Affiliation(s)
- Laia Coll-SanMartin
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
| | - Veronica Davalos
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
| | - David Piñeyro
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
- Centro de Investigación Biomédica en Red Cáncer (CIBERONC), 28029 Madrid, Spain
| | - Margalida Rosselló-Tortella
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
- Germans Trias i Pujol Health Science Research Institute (IGTP), 08916 Barcelona, Spain
| | - Alberto Bueno-Costa
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
| | - Fernando Setien
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
| | - Alberto Villanueva
- Group of Chemoresistance and Predictive Factors, Subprogram Against Cancer Therapeutic Resistance (ProCURE), Oncobell Program, IDIBELL, Institut Català d’Oncologia (ICO), L’Hospitalet del Llobregat, 08908 Barcelona, Spain;
| | - Isabel Granada
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
- Cytogenetics Platform, Hematology Laboratory Service, Institut Català d’Oncologia (ICO)-Hospital Germans Trias i Pujol (IGTP), 08916 Barcelona, Spain
| | - Neus Ruiz-Xiviller
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
- Cytogenetics Platform, Hematology Laboratory Service, Institut Català d’Oncologia (ICO)-Hospital Germans Trias i Pujol (IGTP), 08916 Barcelona, Spain
| | - Annika Kotter
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany; (A.K.); (M.H.)
| | - Mark Helm
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany; (A.K.); (M.H.)
| | - Jun Yokota
- Division of Genome Biology, National Cancer Center Research Institute, Tokyo 104-0045, Japan; (J.Y.); (R.K.-I.); (T.K.)
| | - Reika Kawabata-Iwakawa
- Division of Genome Biology, National Cancer Center Research Institute, Tokyo 104-0045, Japan; (J.Y.); (R.K.-I.); (T.K.)
- Division of Integrated Oncology Research, Gunma University Initiative for Advanced Research, Gunma 371-8511, Japan
| | - Takashi Kohno
- Division of Genome Biology, National Cancer Center Research Institute, Tokyo 104-0045, Japan; (J.Y.); (R.K.-I.); (T.K.)
- Division of Translational Genomics, Exploratory Oncology Research and Clinical Trial Center, National Cancer Center, Tokyo 104-0045, Japan
| | - Manel Esteller
- Josep Carreras Leukaemia Research Institute (IJC), 08916 Barcelona, Spain; (L.C.-S.); (V.D.); (D.P.); (M.R.-T.); (A.B.-C.); (F.S.); (I.G.); (N.R.-X.)
- Centro de Investigación Biomédica en Red Cáncer (CIBERONC), 28029 Madrid, Spain
- Institucio Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
- Physiological Sciences Department, School of Medicine and Health Sciences, University of Barcelona (UB), 08036 Barcelona, Spain
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6
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Khalique A, Mattijssen S, Haddad AF, Chaudhry S, Maraia RJ. Targeting mitochondrial and cytosolic substrates of TRIT1 isopentenyltransferase: Specificity determinants and tRNA-i6A37 profiles. PLoS Genet 2020; 16:e1008330. [PMID: 32324744 PMCID: PMC7200024 DOI: 10.1371/journal.pgen.1008330] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 05/05/2020] [Accepted: 03/18/2020] [Indexed: 11/29/2022] Open
Abstract
The tRNA isopentenyltransferases (IPTases), which add an isopentenyl group to N6 of A37 (i6A37) of certain tRNAs, are among a minority of enzymes that modify cytosolic and mitochondrial tRNAs. Pathogenic mutations to the human IPTase, TRIT1, that decrease i6A37 levels, cause mitochondrial insufficiency that leads to neurodevelopmental disease. We show that TRIT1 encodes an amino-terminal mitochondrial targeting sequence (MTS) that directs mitochondrial import and modification of mitochondrial-tRNAs. Full understanding of IPTase function must consider the tRNAs selected for modification, which vary among species, and in their cytosol and mitochondria. Selection is principally via recognition of the tRNA A36-A37-A38 sequence. An exception is unmodified tRNATrpCCA-A37-A38 in Saccharomyces cerevisiae, whereas tRNATrpCCA is readily modified in Schizosaccharomyces pombe, indicating variable IPTase recognition systems and suggesting that additional exceptions may account for some of the tRNA-i6A37 paucity in higher eukaryotes. Yet TRIT1 had not been characterized for restrictive type substrate-specific recognition. We used i6A37-dependent tRNA-mediated suppression and i6A37-sensitive northern blotting to examine IPTase activities in S. pombe and S. cerevisiae lacking endogenous IPTases on a diversity of tRNA-A36-A37-A38 substrates. Point mutations to the TRIT1 MTS that decrease human mitochondrial import, decrease modification of mitochondrial but not cytosolic tRNAs in both yeasts. TRIT1 exhibits clear substrate-specific restriction against a cytosolic-tRNATrpCCA-A37-A38. Additional data suggest that position 32 of tRNATrpCCA is a conditional determinant for substrate-specific i6A37 modification by the restrictive IPTases, Mod5 and TRIT1. The cumulative biochemical and phylogenetic sequence analyses provide new insights into IPTase activities and determinants of tRNA-i6A37 profiles in cytosol and mitochondria.
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Affiliation(s)
- Abdul Khalique
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sandy Mattijssen
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
| | - Alexander F. Haddad
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
| | - Shereen Chaudhry
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
| | - Richard J. Maraia
- Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, of the National Institutes of Health, Bethesda, Maryland, United States of America
- Commissioned Corps, United States Public Health Service, Rockville, Maryland, United States of America
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7
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Hopper AK, Nostramo RT. tRNA Processing and Subcellular Trafficking Proteins Multitask in Pathways for Other RNAs. Front Genet 2019; 10:96. [PMID: 30842788 PMCID: PMC6391926 DOI: 10.3389/fgene.2019.00096] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 01/29/2019] [Indexed: 01/28/2023] Open
Abstract
This article focuses upon gene products that are involved in tRNA biology, with particular emphasis upon post-transcriptional RNA processing and nuclear-cytoplasmic subcellular trafficking. Rather than analyzing these proteins solely from a tRNA perspective, we explore the many overlapping functions of the processing enzymes and proteins involved in subcellular traffic. Remarkably, there are numerous examples of conserved gene products and RNP complexes involved in tRNA biology that multitask in a similar fashion in the production and/or subcellular trafficking of other RNAs, including small structured RNAs such as snRNA, snoRNA, 5S RNA, telomerase RNA, and SRP RNA as well as larger unstructured RNAs such as mRNAs and RNA-protein complexes such as ribosomes. Here, we provide examples of steps in tRNA biology that are shared with other RNAs including those catalyzed by enzymes functioning in 5' end-processing, pseudoU nucleoside modification, and intron splicing as well as steps regulated by proteins functioning in subcellular trafficking. Such multitasking highlights the clever mechanisms cells employ for maximizing their genomes.
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Affiliation(s)
- Anita K Hopper
- Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, OH, United States
| | - Regina T Nostramo
- Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, OH, United States
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8
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Pollo-Oliveira L, de Crécy-Lagard V. Can Protein Expression Be Regulated by Modulation of tRNA Modification Profiles? Biochemistry 2018; 58:355-362. [PMID: 30511849 DOI: 10.1021/acs.biochem.8b01035] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
tRNAs are the central adaptor molecules in translation. Their decoding properties are influenced by post-transcriptional modifications, particularly in the critical anticodon-stem-loop (ASL) region. Synonymous codon choice, also called codon usage bias, affects both translation efficiency and accuracy, and ASL modifications play key roles in both of these processes. In combination with a handful of historical examples, recent studies integrating ribosome profiling, proteomics, codon-usage analyses, and modification quantifications show that levels of tRNA modifications can change under stress, during development, or under specific metabolic conditions and can modulate the expression of specific genes. Deconvoluting the different responses (global or specific) to tRNA modification deficiencies can be difficult because of pleiotropic effects, but, as more cases emerge, it does seem that tRNA modification changes could add another layer of regulation in the transfer of information from DNA to protein.
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Affiliation(s)
- Leticia Pollo-Oliveira
- Department of Microbiology and Cell Science , University of Florida , Gainesville , Florida 32603 , United States
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science , University of Florida , Gainesville , Florida 32603 , United States.,University of Florida Genetics Institute , Gainesville , Florida 32608 , United States
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9
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Marín M, Fernández-Calero T, Ehrlich R. Protein folding and tRNA biology. Biophys Rev 2017; 9:573-588. [PMID: 28944442 PMCID: PMC5662057 DOI: 10.1007/s12551-017-0322-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 08/28/2017] [Indexed: 12/14/2022] Open
Abstract
Polypeptides can fold into tertiary structures while they are synthesized by the ribosome. In addition to the amino acid sequence, protein folding is determined by several factors within the cell. Among others, the folding pathway of a nascent polypeptide can be affected by transient interactions with other proteins, ligands, or the ribosome, as well as by the translocation through membrane pores. Particularly, the translation machinery and the population of tRNA under different physiological or adaptive responses can dramatically affect protein folding. This review summarizes the scientific evidence describing the role of translation kinetics and tRNA populations on protein folding and addresses current efforts to better understand tRNA biology. It is organized into three main parts, which are focused on: (i) protein folding in the cellular context; (ii) tRNA biology and the complexity of the tRNA population; and (iii) available methods and technical challenges in the characterization of tRNA pools. In this manner, this work illustrates the ways by which functional properties of proteins may be modulated by cellular tRNA populations.
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Affiliation(s)
- Mónica Marín
- Biochemistry-Molecular Biology Section, Cellular and Molecular Biology Department, Faculty of Sciences, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
| | - Tamara Fernández-Calero
- Biochemistry-Molecular Biology Section, Cellular and Molecular Biology Department, Faculty of Sciences, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
- Bioinformatics Unit, Institut Pasteur Montevideo, Mataojo 2020, 11400 Montevideo, Uruguay
| | - Ricardo Ehrlich
- Biochemistry-Molecular Biology Section, Cellular and Molecular Biology Department, Faculty of Sciences, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
- Institut Pasteur Montevideo, Mataojo 2020, 11400 Montevideo, Uruguay
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10
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Read DF, Waller TJ, Tse E, Southworth DR, Engelke DR, Smaldino PJ. Aggregation of Mod5 is affected by tRNA binding with implications for tRNA gene-mediated silencing. FEBS Lett 2017; 591:1601-1610. [PMID: 28303570 DOI: 10.1002/1873-3468.12627] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 03/09/2017] [Accepted: 03/13/2017] [Indexed: 12/24/2022]
Abstract
Mod5 is a multifunctional protein that modifies a subset of tRNAs in the cytoplasm and is also required for an RNA-mediated form of transcriptional silencing. Previous in vivo studies have shown that the nuclear silencing function of Mod5 does not require that the causative tRNA gene encode a Mod5 substrate, although Mod5 is still required. However, previous data have not directly tested whether Mod5 can directly bind substrate and nonsubstrate RNAs. We herein demonstrate that Mod5 directly binds to both substrate and nonsubstrate RNAs, including a highly structured, non-tRNA sequence (5S-rRNA), consistent with previous in vivo data. Furthermore, we show that some RNAs drastically change the aggregation behavior of Mod5 with implications for tRNA gene-mediated silencing.
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Affiliation(s)
- David F Read
- Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - Thomas J Waller
- Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - Eric Tse
- Biological Chemistry, University of Michigan, Ann Arbor, MI, USA.,Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Daniel R Southworth
- Biological Chemistry, University of Michigan, Ann Arbor, MI, USA.,Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - David R Engelke
- Biological Chemistry, University of Michigan, Ann Arbor, MI, USA.,University of Colorado Denver/Anschutz Medical Campus, Aurora, CO, USA
| | - Philip J Smaldino
- Biological Chemistry, University of Michigan, Ann Arbor, MI, USA.,Biology, Ball State University, Muncie, IN, USA
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11
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Schweizer U, Bohleber S, Fradejas-Villar N. The modified base isopentenyladenosine and its derivatives in tRNA. RNA Biol 2017; 14:1197-1208. [PMID: 28277934 PMCID: PMC5699536 DOI: 10.1080/15476286.2017.1294309] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Base 37 in tRNA, 3′-adjacent to the anticodon, is occupied by a purine base that is thought to stabilize codon recognition by stacking interactions on the first Watson-Crick base pair. If the first codon position forms an A.U or U.A base pair, the purine is likely further modified in all domains of life. One of the first base modifications found in tRNA is N6-isopentenyl adenosine (i6A) present in a fraction of tRNAs in bacteria and eukaryotes, which can be further modified to 2-methyl-thio-N6-isopentenyladenosine (ms2i6A) in a subset of tRNAs. Homologous tRNA isopentenyl transferase enzymes have been identified in bacteria (MiaA), yeast (Mod5, Tit1), roundworm (GRO-1), and mammals (TRIT1). In eukaryotes, isopentenylation of cytoplasmic and mitochondrial tRNAs is mediated by products of the same gene. Accordingly, a patient with homozygous mutations in TRIT1 has mitochondrial disease. The role of i6A in a subset of tRNAs in gene expression has been linked with translational fidelity, speed of translation, skewed gene expression, and non-sense suppression. This review will not cover the action of i6A as a cytokinin in plants or the potential function of Mod5 as a prion in yeast.
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Affiliation(s)
- Ulrich Schweizer
- a Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn , Bonn , Germany
| | - Simon Bohleber
- a Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn , Bonn , Germany
| | - Noelia Fradejas-Villar
- a Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn , Bonn , Germany
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12
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Hinsch J, Galuszka P, Tudzynski P. Functional characterization of the first filamentous fungal tRNA-isopentenyltransferase and its role in the virulence of Claviceps purpurea. THE NEW PHYTOLOGIST 2016; 211:980-992. [PMID: 27074411 DOI: 10.1111/nph.13960] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 03/01/2016] [Indexed: 06/05/2023]
Abstract
In plants, cytokinins (CKs) are synthesized de novo or by the degradation of modified tRNAs. Recently, the first fungal de novo pathway was identified within the plant pathogen Claviceps purpurea. As the deletion of the de novo pathway did not lead to a complete loss of CKs, this work focuses on the tRNA-modifying protein tRNA-isopentenyltransferase (CptRNA-IPT). The contribution of this enzyme to the CK pool of Claviceps and the role of CKs in the host-pathogen interaction are emphasized. The effects of the deletion of cptRNA-ipt and the double deletion of cptRNA-ipt and the key gene of de novo biosynthesis cpipt-log on growth, CK biosynthesis and virulence were analyzed. In addition, the sites of action of CptRNA-IPT were visualized using reporter gene fusions. In addition to CK-independent functions, CptRNA-IPT was essential for the biosynthesis of cis-zeatin (cZ) and contributed to the formation of isopentenyladenine (iP) and trans-zeatin (tZ). Although ΔcptRNA-ipt was reduced in virulence, the 'CK-free' double deletion mutant was nearly apathogenic. The results prove a redundancy of the CK biosynthesis pathway in C. purpurea for iP and tZ formation. Moreover, we show, for the first time, that CKs are required for the successful establishment of a host-fungus interaction.
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Affiliation(s)
- Janine Hinsch
- Institute of Plant Biology and Biotechnology, Westfälische Wilhelms-University Münster, Schlossplatz 8, 48143, Münster, Germany
| | - Petr Galuszka
- Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University, Šlechtitelů 27, 78371, Olomouc, Czech Republic
| | - Paul Tudzynski
- Institute of Plant Biology and Biotechnology, Westfälische Wilhelms-University Münster, Schlossplatz 8, 48143, Münster, Germany
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RNA Polymerase III Output Is Functionally Linked to tRNA Dimethyl-G26 Modification. PLoS Genet 2015; 11:e1005671. [PMID: 26720005 PMCID: PMC4697793 DOI: 10.1371/journal.pgen.1005671] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 10/26/2015] [Indexed: 11/19/2022] Open
Abstract
Control of the differential abundance or activity of tRNAs can be important determinants of gene regulation. RNA polymerase (RNAP) III synthesizes all tRNAs in eukaryotes and it derepression is associated with cancer. Maf1 is a conserved general repressor of RNAP III under the control of the target of rapamycin (TOR) that acts to integrate transcriptional output and protein synthetic demand toward metabolic economy. Studies in budding yeast have indicated that the global tRNA gene activation that occurs with derepression of RNAP III via maf1-deletion is accompanied by a paradoxical loss of tRNA-mediated nonsense suppressor activity, manifested as an antisuppression phenotype, by an unknown mechanism. We show that maf1-antisuppression also occurs in the fission yeast S. pombe amidst general activation of RNAP III. We used tRNA-HydroSeq to document that little changes occurred in the relative levels of different tRNAs in maf1Δ cells. By contrast, the efficiency of N2,N2-dimethyl G26 (m(2)2G26) modification on certain tRNAs was decreased in response to maf1-deletion and associated with antisuppression, and was validated by other methods. Over-expression of Trm1, which produces m(2)2G26, reversed maf1-antisuppression. A model that emerges is that competition by increased tRNA levels in maf1Δ cells leads to m(2)2G26 hypomodification due to limiting Trm1, reducing the activity of suppressor-tRNASerUCA and accounting for antisuppression. Consistent with this, we show that RNAP III mutations associated with hypomyelinating leukodystrophy decrease tRNA transcription, increase m(2)2G26 efficiency and reverse antisuppression. Extending this more broadly, we show that a decrease in tRNA synthesis by treatment with rapamycin leads to increased m(2)2G26 modification and that this response is conserved among highly divergent yeasts and human cells.
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Abstract
A prion is an infectious protein horizontally transmitting a disease or trait without a required nucleic acid. Yeast and fungal prions are nonchromosomal genes composed of protein, generally an altered form of a protein that catalyzes the same alteration of the protein. Yeast prions are thus transmitted both vertically (as genes composed of protein) and horizontally (as infectious proteins, or prions). Formation of amyloids (linear ordered β-sheet-rich protein aggregates with β-strands perpendicular to the long axis of the filament) underlies most yeast and fungal prions, and a single prion protein can have any of several distinct self-propagating amyloid forms with different biological properties (prion variants). Here we review the mechanism of faithful templating of protein conformation, the biological roles of these prions, and their interactions with cellular chaperones, the Btn2 and Cur1 aggregate-handling systems, and other cellular factors governing prion generation and propagation. Human amyloidoses include the PrP-based prion conditions and many other, more common amyloid-based diseases, several of which show prion-like features. Yeast prions increasingly are serving as models for the understanding and treatment of many mammalian amyloidoses. Patients with different clinical pictures of the same amyloidosis may be the equivalent of yeasts with different prion variants.
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Abstract
A prion is an infectious protein horizontally transmitting a disease or trait without a required nucleic acid. Yeast and fungal prions are nonchromosomal genes composed of protein, generally an altered form of a protein that catalyzes the same alteration of the protein. Yeast prions are thus transmitted both vertically (as genes composed of protein) and horizontally (as infectious proteins, or prions). Formation of amyloids (linear ordered β-sheet-rich protein aggregates with β-strands perpendicular to the long axis of the filament) underlies most yeast and fungal prions, and a single prion protein can have any of several distinct self-propagating amyloid forms with different biological properties (prion variants). Here we review the mechanism of faithful templating of protein conformation, the biological roles of these prions, and their interactions with cellular chaperones, the Btn2 and Cur1 aggregate-handling systems, and other cellular factors governing prion generation and propagation. Human amyloidoses include the PrP-based prion conditions and many other, more common amyloid-based diseases, several of which show prion-like features. Yeast prions increasingly are serving as models for the understanding and treatment of many mammalian amyloidoses. Patients with different clinical pictures of the same amyloidosis may be the equivalent of yeasts with different prion variants.
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16
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Abstract
Cellular RNAs can be chemically modified over a hundred different ways. These modifications were once thought to be static, discrete, and utilized to fine-tune RNA structure and function. However, recent studies have revealed that some modifications, like mRNA methylation, can be reversed, and these reversible modifications may play active roles in regulating diverse biological processes. In this perspective, we summarize examples of dynamic RNA modifications that affect biological functions. We further propose that reversible modifications might occur on tRNA, rRNA, and other noncoding RNAs to regulate gene expression analogous to the reversible mRNA methylation.
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17
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Schoenrock A, Samanfar B, Pitre S, Hooshyar M, Jin K, Phillips CA, Wang H, Phanse S, Omidi K, Gui Y, Alamgir M, Wong A, Barrenäs F, Babu M, Benson M, Langston MA, Green JR, Dehne F, Golshani A. Efficient prediction of human protein-protein interactions at a global scale. BMC Bioinformatics 2014; 15:383. [PMID: 25492630 PMCID: PMC4272565 DOI: 10.1186/s12859-014-0383-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 11/12/2014] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Our knowledge of global protein-protein interaction (PPI) networks in complex organisms such as humans is hindered by technical limitations of current methods. RESULTS On the basis of short co-occurring polypeptide regions, we developed a tool called MP-PIPE capable of predicting a global human PPI network within 3 months. With a recall of 23% at a precision of 82.1%, we predicted 172,132 putative PPIs. We demonstrate the usefulness of these predictions through a range of experiments. CONCLUSIONS The speed and accuracy associated with MP-PIPE can make this a potential tool to study individual human PPI networks (from genomic sequences alone) for personalized medicine.
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Affiliation(s)
| | | | - Sylvain Pitre
- School of Computer Science, Carleton University, Ottawa, Canada.
| | | | - Ke Jin
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada.
| | - Charles A Phillips
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee, USA.
| | - Hui Wang
- Department of Pediatrics, Gothenburg University, Gothenburg, Sweden. .,The Centre for Individualized Medication, Linköping University, Linköping, Sweden.
| | - Sadhna Phanse
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada.
| | - Katayoun Omidi
- Department of Biology, Carleton University, Ottawa, Canada.
| | - Yuan Gui
- Department of Biology, Carleton University, Ottawa, Canada.
| | - Md Alamgir
- Department of Biology, Carleton University, Ottawa, Canada.
| | - Alex Wong
- Department of Biology, Carleton University, Ottawa, Canada.
| | - Fredrik Barrenäs
- Department of Pediatrics, Gothenburg University, Gothenburg, Sweden. .,The Centre for Individualized Medication, Linköping University, Linköping, Sweden.
| | - Mohan Babu
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada.
| | - Mikael Benson
- Department of Pediatrics, Gothenburg University, Gothenburg, Sweden. .,The Centre for Individualized Medication, Linköping University, Linköping, Sweden.
| | - Michael A Langston
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee, USA.
| | - James R Green
- Department of Systems and Computer Engineering, Carleton University, Ottawa, Canada.
| | - Frank Dehne
- School of Computer Science, Carleton University, Ottawa, Canada.
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18
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Smaldino PJ, Read DF, Pratt-Hyatt M, Hopper AK, Engelke DR. The cytoplasmic and nuclear populations of the eukaryote tRNA-isopentenyl transferase have distinct functions with implications in human cancer. Gene 2014; 556:13-8. [PMID: 25261850 DOI: 10.1016/j.gene.2014.09.049] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 09/22/2014] [Accepted: 09/23/2014] [Indexed: 12/29/2022]
Abstract
Mod5 is the yeast tRNA isopentenyl transferase, an enzyme that is conserved from bacteria to humans. Mod5 is primarily cytoplasmic where it modifies the A37 position of a few tRNAs, and the yeast enzyme has been shown capable of forming heritable, amyloid-like aggregates that confer a selective advantage in the presence of specific antifungal agents. A subpopulation of Mod5 is also found associated with nuclear tRNA genes, where it contributes tRNA-gene mediated (tgm) silencing of local transcription by RNA polymerase II. The tgm-silencing function of Mod5 has been observed in yeast and a Mod5-deletion in yeast can be complemented by the plant and human tRNA isopentenyl transferases, but not the bacterial enzymes, possibly due to the lack of an extended C-terminal domain found in eukaryotes. In light of this additional nuclear role for Mod5 we discuss the proposed role of the human homologue of Mod5, TRIT1, as a tumor suppressor protein.
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Affiliation(s)
- P J Smaldino
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
| | - D F Read
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - M Pratt-Hyatt
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; The Great Plains Laboratory, 11813W. 77th St. Lenexa KS 66214, USA
| | - A K Hopper
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - D R Engelke
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
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19
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Yarham JW, Lamichhane TN, Pyle A, Mattijssen S, Baruffini E, Bruni F, Donnini C, Vassilev A, He L, Blakely EL, Griffin H, Santibanez-Koref M, Bindoff LA, Ferrero I, Chinnery PF, McFarland R, Maraia RJ, Taylor RW. Defective i6A37 modification of mitochondrial and cytosolic tRNAs results from pathogenic mutations in TRIT1 and its substrate tRNA. PLoS Genet 2014; 10:e1004424. [PMID: 24901367 PMCID: PMC4046958 DOI: 10.1371/journal.pgen.1004424] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 04/20/2014] [Indexed: 01/10/2023] Open
Abstract
Identifying the genetic basis for mitochondrial diseases is technically challenging given the size of the mitochondrial proteome and the heterogeneity of disease presentations. Using next-generation exome sequencing, we identified in a patient with severe combined mitochondrial respiratory chain defects and corresponding perturbation in mitochondrial protein synthesis, a homozygous p.Arg323Gln mutation in TRIT1. This gene encodes human tRNA isopentenyltransferase, which is responsible for i6A37 modification of the anticodon loops of a small subset of cytosolic and mitochondrial tRNAs. Deficiency of i6A37 was previously shown in yeast to decrease translational efficiency and fidelity in a codon-specific manner. Modelling of the p.Arg323Gln mutation on the co-crystal structure of the homologous yeast isopentenyltransferase bound to a substrate tRNA, indicates that it is one of a series of adjacent basic side chains that interact with the tRNA backbone of the anticodon stem, somewhat removed from the catalytic center. We show that patient cells bearing the p.Arg323Gln TRIT1 mutation are severely deficient in i6A37 in both cytosolic and mitochondrial tRNAs. Complete complementation of the i6A37 deficiency of both cytosolic and mitochondrial tRNAs was achieved by transduction of patient fibroblasts with wild-type TRIT1. Moreover, we show that a previously-reported pathogenic m.7480A>G mt-tRNASer(UCN) mutation in the anticodon loop sequence A36A37A38 recognised by TRIT1 causes a loss of i6A37 modification. These data demonstrate that deficiencies of i6A37 tRNA modification should be considered a potential mechanism of human disease caused by both nuclear gene and mitochondrial DNA mutations while providing insight into the structure and function of TRIT1 in the modification of cytosolic and mitochondrial tRNAs. Mitochondrial disorders are clinically diverse, and identifying the underlying genetic mutations is technically challenging due to the large number of mitochondrial proteins. Using high-throughput sequencing technology, we identified a disease-causing mutation in the TRIT1 gene. This gene encodes an enzyme, tRNA isopentenyltransferase, that adds an N6-isopentenyl modification to adenosine-37 (i6A37) in a small number of tRNAs, enabling them to function correctly during the synthesis of essential mitochondrial proteins. We show that this mutation leads to severe deficiency of tRNA-i6A37 in the patient's cells that can be rescued by introduction of the wild-type TRIT1 protein. A deficiency in oxidative phosphorylation, the process by which energy (ATP) is generated in the mitochondria, leads to a mitochondrial disease presentation. Introducing the mutant protein into model yeast species and measuring the resulting impairment provided further evidence of the pathogenic effect of the mutation. Additional studies investigating a previously reported pathogenic mutation in a mitochondrial tRNA gene demonstrated that a mutation in a substrate of TRIT1 can also cause a loss of the modification, providing evidence of a new mechanism causing mitochondrial disease in humans.
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Affiliation(s)
- John W. Yarham
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Tek N. Lamichhane
- Intramural Research Program, NICHD, NIH, Bethesda, Maryland, United States of America
| | - Angela Pyle
- Wellcome Trust Centre for Mitochondrial Research, Institute for Genetic Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Sandy Mattijssen
- Intramural Research Program, NICHD, NIH, Bethesda, Maryland, United States of America
| | | | - Francesco Bruni
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Claudia Donnini
- Department of Life Sciences, University of Parma, Parma, Italy
| | - Alex Vassilev
- Intramural Research Program, NICHD, NIH, Bethesda, Maryland, United States of America
| | - Langping He
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Emma L. Blakely
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Helen Griffin
- Wellcome Trust Centre for Mitochondrial Research, Institute for Genetic Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Mauro Santibanez-Koref
- Wellcome Trust Centre for Mitochondrial Research, Institute for Genetic Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Laurence A. Bindoff
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Ileana Ferrero
- Department of Life Sciences, University of Parma, Parma, Italy
| | - Patrick F. Chinnery
- Wellcome Trust Centre for Mitochondrial Research, Institute for Genetic Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Richard J. Maraia
- Intramural Research Program, NICHD, NIH, Bethesda, Maryland, United States of America
- * E-mail: (RJM) (RM); (RWT) (RT)
| | - Robert W. Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
- * E-mail: (RJM) (RM); (RWT) (RT)
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20
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Sugiyama S, Tanaka M. Self-propagating amyloid as a critical regulator for diverse cellular functions. J Biochem 2014; 155:345-51. [PMID: 24711463 DOI: 10.1093/jb/mvu026] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Amyloids are β-sheet-rich fibrillar protein aggregates characterized by structural properties of self-propagation and strong resistance to detergent and proteinase. Although a number of causative proteins for neurodegenerative disorders are known to undergo amyloid formation, recent studies have revealed that amyloids may also play beneficial roles in cells. Cellular processes that could be regulated by amyloids are diverse and include translational regulation, programmed cell death and protein storage. Yeast prions of Mod5 and Mot3, non-Mendelian extra-chromosomal factors, also show amyloid-like biophysical properties and have recently been shown to confer host cells resistant to environmental stressors. Furthermore, yeast cells actively respond to environmental stress for fitness adaptation to environmental changes by converting soluble yeast prion proteins into their amyloid forms, allowing cells to survive under stress conditions. Therefore, amyloids are not simply the terminal end-products of protein misfolding but a growing body of evidence suggests that they may possess physiological roles by using their self-propagating properties. Here, we present an overview on recent progress of the research on such functional amyloids.
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Affiliation(s)
- Shinju Sugiyama
- Laboratory for Protein Conformation Diseases, RIKEN Brain Science Institute, Wako 351-0198, Japan and Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, JapanLaboratory for Protein Conformation Diseases, RIKEN Brain Science Institute, Wako 351-0198, Japan and Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan
| | - Motomasa Tanaka
- Laboratory for Protein Conformation Diseases, RIKEN Brain Science Institute, Wako 351-0198, Japan and Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, JapanLaboratory for Protein Conformation Diseases, RIKEN Brain Science Institute, Wako 351-0198, Japan and Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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21
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The translational machinery is an optimized molecular network that affects cellular homoeostasis and disease. Biochem Soc Trans 2014; 42:173-6. [DOI: 10.1042/bst20130131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Translation involves interactions between mRNAs, ribosomes, tRNAs and a host of translation factors. Emerging evidence on the eukaryotic translational machinery indicates that these factors are organized in a highly optimized network, in which the levels of the different factors are finely matched to each other. This optimal factor network is essential for producing proteomes that result in optimal fitness, and perturbations to the optimal network that significantly affect translational activity therefore result in non-optimal proteomes, fitness losses and disease. On the other hand, experimental evidence indicates that translation and cell growth are relatively robust to perturbations, and viability can be maintained even upon significant damage to individual translation factors. How the eukaryotic translational machinery is optimized, and how it can maintain optimization in the face of changing internal parameters, are open questions relevant to the interaction between translation and cellular disease states.
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22
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Posttranscriptional RNA Modifications: playing metabolic games in a cell's chemical Legoland. ACTA ACUST UNITED AC 2013; 21:174-85. [PMID: 24315934 DOI: 10.1016/j.chembiol.2013.10.015] [Citation(s) in RCA: 164] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/24/2013] [Accepted: 10/30/2013] [Indexed: 12/15/2022]
Abstract
Nature combines existing biochemical building blocks, at times with subtlety of purpose. RNA modifications are a prime example of this, where standard RNA nucleosides are decorated with chemical groups and building blocks that we recall from our basic biochemistry lectures. The result: a wealth of chemical diversity whose full biological relevance has remained elusive despite being public knowledge for some time. Here, we highlight several modifications that, because of their chemical intricacy, rely on seemingly unrelated pathways to provide cofactors for their synthesis. Besides their immediate role in affecting RNA function, modifications may act as sensors and transducers of information that connect a cell's metabolic state to its translational output, carefully orchestrating a delicate balance between metabolic rate and protein synthesis at a system's level.
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23
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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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24
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Mod5 protein binds to tRNA gene complexes and affects local transcriptional silencing. Proc Natl Acad Sci U S A 2013; 110:E3081-9. [PMID: 23898186 DOI: 10.1073/pnas.1219946110] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The tRNA gene-mediated (tgm) silencing of RNA polymerase II promoters is dependent on subnuclear clustering of the tRNA genes, but genetic analysis shows that the silencing requires additional mechanisms. We have identified proteins that bind tRNA gene transcription complexes and are required for tgm silencing but not required for gene clustering. One of the proteins, Mod5, is a tRNA modifying enzyme that adds an N6-isopentenyl adenosine modification at position 37 on a small number of tRNAs in the cytoplasm, although a subpopulation of Mod5 is also found in the nucleus. Recent publications have also shown that Mod5 has tumor suppressor characteristics in humans as well as confers drug resistance through prion-like misfolding in yeast. Here, we show that a subpopulation of Mod5 associates with tRNA gene complexes in the nucleolus. This association occurs and is required for tgm silencing regardless of whether the pre-tRNA transcripts are substrates for Mod5 modification. In addition, Mod5 is bound to nuclear pre-tRNA transcripts, although they are not substrates for the A37 modification. Lastly, we show that truncation of the tRNA transcript to remove the normal tRNA structure also alleviates silencing, suggesting that synthesis of intact pre-tRNAs is required for the silencing mechanism. These results are discussed in light of recent results showing that silencing near tRNA genes also requires chromatin modification.
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25
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Wickner RB, Edskes HK, Bateman DA, Kelly AC, Gorkovskiy A, Dayani Y, Zhou A. Amyloids and yeast prion biology. Biochemistry 2013; 52:1514-27. [PMID: 23379365 DOI: 10.1021/bi301686a] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The prions (infectious proteins) of Saccharomyces cerevisiae are proteins acting as genes, by templating their conformation from one molecule to another in analogy to DNA templating its sequence. Most yeast prions are amyloid forms of normally soluble proteins, and a single protein sequence can have any of several self-propagating forms (called prion strains or variants), analogous to the different possible alleles of a DNA gene. A central issue in prion biology is the structural basis of this conformational templating process. The in-register parallel β sheet structure found for several infectious yeast prion amyloids naturally suggests an explanation for this conformational templating. While most prions are plainly diseases, the [Het-s] prion of Podospora anserina may be a functional amyloid, with important structural implications. Yeast prions are important models for human amyloid diseases in general, particularly because new evidence is showing infectious aspects of several human amyloidoses not previously classified as prions. We also review studies of the roles of chaperones, aggregate-collecting proteins, and other cellular components using yeast that have led the way in improving the understanding of similar processes that must be operating in many human amyloidoses.
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Affiliation(s)
- Reed B Wickner
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0830, USA.
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Suzuki G, Tanaka M. Active conversion to the prion state as a molecular switch for cellular adaptation to environmental stress. Bioessays 2012; 35:12-6. [DOI: 10.1002/bies.201200121] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Suzuki G, Shimazu N, Tanaka M. A yeast prion, Mod5, promotes acquired drug resistance and cell survival under environmental stress. Science 2012; 336:355-9. [PMID: 22517861 DOI: 10.1126/science.1219491] [Citation(s) in RCA: 177] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Prion conversion from a soluble protein to an aggregated state may be involved in the cellular adaptation of yeast to the environment. However, it remains unclear whether and how cells actively use prion conversion to acquire a fitness advantage in response to environmental stress. We identified Mod5, a yeast transfer RNA isopentenyltransferase lacking glutamine/asparagine-rich domains, as a yeast prion protein and found that its prion conversion in yeast regulated the sterol biosynthetic pathway for acquired cellular resistance against antifungal agents. Furthermore, selective pressure by antifungal drugs on yeast facilitated the de novo appearance of Mod5 prion states for cell survival. Thus, phenotypic changes caused by active prion conversion under environmental selection may contribute to cellular adaptation in living organisms.
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Affiliation(s)
- Genjiro Suzuki
- Laboratory for Protein Conformation Diseases, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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28
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Lamichhane TN, Blewett NH, Maraia RJ. Plasticity and diversity of tRNA anticodon determinants of substrate recognition by eukaryotic A37 isopentenyltransferases. RNA (NEW YORK, N.Y.) 2011; 17:1846-57. [PMID: 21873461 PMCID: PMC3185917 DOI: 10.1261/rna.2628611] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The N(6)-(isopentenyl)adenosine (i(6)A) modification of some tRNAs at position A37 is found in all kingdoms and facilitates codon-specific mRNA decoding, but occurs in different subsets of tRNAs in different species. Here we examine yeasts' tRNA isopentenyltransferases (i.e., dimethylallyltransferase, DMATase, members of the Δ(2)-isopentenylpyrophosphate transferase, IPPT superfamily) encoded by tit1(+) in Schizosaccharomyces pombe and MOD5 in Saccharomyces cerevisiae, whose homologs are Escherichia coli miaA, the human tumor suppressor TRIT1, and the Caenorhabditis elegans life-span gene product GRO-1. A major determinant of miaA activity is known to be the single-stranded tRNA sequence, A36A37A38, in a stem-loop. tRNA(Trp)(CCA) from either yeast is a Tit1p substrate, but neither is a Mod5p substrate despite the presence of A36A37A38. We show that Tit1p accommodates a broader range of substrates than Mod5p. tRNA(Trp)(CCA) is distinct from Mod5p substrates, which we sort into two classes based on the presence of G at position 34 and other elements. A single substitution of C34 to G converts tRNA(Trp)(CCA) to a Mod5p substrate in vitro and in vivo, consistent with amino acid contacts to G34 in existing Mod5p-tRNA(Cys)(GCA) crystal structures. Mutation of Mod5p in its G34 recognition loop region debilitates it differentially for its G34 (class I) substrates. Multiple alignments reveal that the G34 recognition loop sequence of Mod5p differs significantly from Tit1p, which more resembles human TRIT1 and other DMATases. We show that TRIT1 can also modify tRNA(Trp)(CCA) consistent with broad recognition similar to Tit1p. This study illustrates previously unappreciated molecular plasticity and biological diversity of the tRNA-isopentenyltransferase system of eukaryotes.
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Affiliation(s)
- Tek N. Lamichhane
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Nathan H. Blewett
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Richard J. Maraia
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
- Commissioned Corps, US Public Health Service, Washington, DC 20201, USA
- Corresponding author.E-mail .
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Kuranda K, François J, Palamarczyk G. The isoprenoid pathway and transcriptional response to its inhibitors in the yeastSaccharomyces cerevisiae. FEMS Yeast Res 2010; 10:14-27. [DOI: 10.1111/j.1567-1364.2009.00560.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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30
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Frechin M, Kern D, Martin RP, Becker HD, Senger B. Arc1p: Anchoring, routing, coordinating. FEBS Lett 2009; 584:427-33. [DOI: 10.1016/j.febslet.2009.11.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Revised: 11/09/2009] [Accepted: 11/09/2009] [Indexed: 10/20/2022]
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31
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Biosynthesis of 7-deazaguanosine-modified tRNA nucleosides: a new role for GTP cyclohydrolase I. J Bacteriol 2008; 190:7876-84. [PMID: 18931107 DOI: 10.1128/jb.00874-08] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Queuosine (Q) and archaeosine (G(+)) are hypermodified ribonucleosides found in tRNA. Q is present in the anticodon region of tRNA(GUN) in Eukarya and Bacteria, while G(+) is found at position 15 in the D-loop of archaeal tRNA. Prokaryotes produce these 7-deazaguanosine derivatives de novo from GTP through the 7-cyano-7-deazaguanine (pre-Q(0)) intermediate, but mammals import the free base, queuine, obtained from the diet or the intestinal flora. By combining the results of comparative genomic analysis with those of genetic studies, we show that the first enzyme of the folate pathway, GTP cyclohydrolase I (GCYH-I), encoded in Escherichia coli by folE, is also the first enzyme of pre-Q(0) biosynthesis in both prokaryotic kingdoms. Indeed, tRNA extracted from an E. coli DeltafolE strain is devoid of Q and the deficiency is complemented by expressing GCYH-I-encoding genes from different bacterial or archaeal origins. In a similar fashion, tRNA extracted from a Haloferax volcanii strain carrying a deletion of the GCYH-I-encoding gene contains only traces of G(+). These results link the production of a tRNA-modified base to primary metabolism and further clarify the biosynthetic pathway for these complex modified nucleosides.
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Gustavsson M, Ronne H. Evidence that tRNA modifying enzymes are important in vivo targets for 5-fluorouracil in yeast. RNA (NEW YORK, N.Y.) 2008; 14:666-74. [PMID: 18314501 PMCID: PMC2271368 DOI: 10.1261/rna.966208] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We have screened a collection of haploid yeast knockout strains for increased sensitivity to 5-fluorouracil (5-FU). A total of 138 5-FU sensitive strains were found. Mutants affecting rRNA and tRNA maturation were particularly sensitive to 5-FU, with the tRNA methylation mutant trm10 being the most sensitive mutant. This is intriguing since trm10, like many other tRNA modification mutants, lacks a phenotype under normal conditions. However, double mutants for nonessential tRNA modification enzymes are frequently temperature sensitive, due to destabilization of hypomodified tRNAs. We therefore tested if the sensitivity of our mutants to 5-FU is affected by the temperature. We found that the cytotoxic effect of 5-FU is strongly enhanced at 38 degrees C for tRNA modification mutants. Furthermore, tRNA modification mutants show similar synthetic interactions for temperature sensitivity and sensitivity to 5-FU. A model is proposed for how 5-FU kills these mutants by reducing the number of tRNA modifications, thus destabilizing tRNA. Finally, we found that also wild-type cells are temperature sensitive at higher concentrations of 5-FU. This suggests that tRNA destabilization contributes to 5-FU cytotoxicity in wild-type cells and provides a possible explanation why hyperthermia can enhance the effect of 5-FU in cancer therapy.
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MESH Headings
- Antineoplastic Agents/pharmacology
- Drug Resistance, Fungal/genetics
- Fluorouracil/pharmacology
- Gene Deletion
- Genes, Fungal
- Haploidy
- Humans
- Models, Biological
- Models, Molecular
- Mutation
- Nucleic Acid Conformation
- RNA Processing, Post-Transcriptional
- RNA Stability
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Saccharomyces cerevisiae/drug effects
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Temperature
- tRNA Methyltransferases/genetics
- tRNA Methyltransferases/metabolism
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Affiliation(s)
- Marie Gustavsson
- Department of Medical Biochemistry and Microbiology, Uppsala University, SE-751 23 Uppsala, Sweden
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33
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Yevdakova NA, von Schwartzenberg K. Characterisation of a prokaryote-type tRNA-isopentenyltransferase gene from the moss Physcomitrella patens. PLANTA 2007; 226:683-95. [PMID: 17450376 DOI: 10.1007/s00425-007-0516-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2006] [Accepted: 03/16/2007] [Indexed: 05/15/2023]
Abstract
Cytokinins are of critical importance to numerous developmental processes in plants. Two cytokinin biosynthetic pathways have been described; each one uses a different type of isopentenyltransferases (IPTs) as the key enzyme. In the first pathway, adenylate-IPTs (EC 2.5.1.27) prenylate adenylic nucleotides to cytokinin nucleotides, thus catalysing the direct de novo biosynthesis of free cytokinins. In the second pathway, tRNA-IPTs (EC 2.5.1.8) catalyse cytokinin formation by isopentenylation of tRNA, the degradation of which liberates cytokinin nucleotides. Seed plants have been shown to possess both forms of IPTs. Here, we report on the in-silico based identification and on the functional characterisation of an IPT encoding gene (PpIPT1) from the bryophyte Physcomitrella patens. Analysis of the PpIPT1 amino acid sequence revealed high similarities to tRNA-IPTs of other plants. No adenylate-IPT genes were found in the Physcomitrella sequenced transcriptome/genome. PpIPT1 functionally complemented a defective tRNA-IPT gene of Saccharomyces cerevisiae (ScMOD5) in the strain MT-8. Dephosphorylated tRNA hydrolysates from PpIPT1-transformed MT-8 showed cytokinin activity in a moss bioassay and the presence of isopentenyladenosine in HPLC analysis, in contrast to those prepared from untransformed MT-8. A comparison of pro- and eukaryotic homologues revealed two classes of tRNA-IPTs; PpIPT1 belongs to a prokaryotic type with predicted chloroplast targeting. RT-PCR experiments revealed a stronger expression in the cytokinin overproducing mutant oveST25, thus indicating the potential role of PpIPT1 for cytokinin biosynthesis in the evolutionary old land plant Physcomitrella.
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Affiliation(s)
- Natalya A Yevdakova
- Biocenter Klein Flottbek and Botanical Garden, University of Hamburg, Ohnhorst street 18, 22609 Hamburg, Germany
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34
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Urbonavičius J, Jäger G, Björk GR. Amino acid residues of the Escherichia coli tRNA(m5U54)methyltransferase (TrmA) critical for stability, covalent binding of tRNA and enzymatic activity. Nucleic Acids Res 2007; 35:3297-305. [PMID: 17459887 PMCID: PMC1904294 DOI: 10.1093/nar/gkm205] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Escherichia coli trmA gene encodes the tRNA(m5U54)methyltransferase, which catalyses the formation of m5U54 in tRNA. During the synthesis of m5U54, a covalent 62-kDa TrmA-tRNA intermediate is formed between the amino acid C324 of the enzyme and the 6-carbon of uracil. We have analysed the formation of this TrmA-tRNA intermediate and m5U54 in vivo, using mutants with altered TrmA. We show that the amino acids F188, Q190, G220, D299, R302, C324 and E358, conserved in the C-terminal catalytic domain of several RNA(m5U)methyltransferases of the COG2265 family, are important for the formation of the TrmA-tRNA intermediate and/or the enzymatic activity. These amino acids seem to have the same function as the ones present in the catalytic domain of RumA, whose structure is known, and which catalyses the formation of m5U in position 1939 of E. coli 23 S rRNA. We propose that the unusually high in vivo level of the TrmA-tRNA intermediate in wild-type cells may be due to a suboptimal cellular concentration of SAM, which is required to resolve this intermediate. Our results are consistent with the modular evolution of RNA(m5U)methyltransferases, in which the specificity of the enzymatic reaction is achieved by combining the conserved catalytic domain with different RNA-binding domains.
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Affiliation(s)
| | | | - Glenn R. Björk
- *To whom correspondence should be addressed. Tel: +46-90-7856759; Fax: +46-90-772630;
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35
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von der Haar T, Tuite MF. Regulated translational bypass of stop codons in yeast. Trends Microbiol 2006; 15:78-86. [PMID: 17187982 DOI: 10.1016/j.tim.2006.12.002] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 11/13/2006] [Accepted: 12/07/2006] [Indexed: 10/23/2022]
Abstract
Stop codons are used to signal the ribosome to terminate the decoding of an mRNA template. Recent studies on translation termination in the yeast Saccharomyces cerevisiae have not only enabled the identification of the key components of the termination machinery, but have also revealed several regulatory mechanisms that might enable the controlled synthesis of C-terminally extended polypeptides via stop-codon readthrough. These include both genetic and epigenetic mechanisms. Rather than being a translation 'error', stop-codon readthrough can have important effects on other cellular processes such as mRNA degradation and, in some cases, can confer a beneficial phenotype to the cell.
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Affiliation(s)
- Tobias von der Haar
- Protein Science Group, Department of Biosciences, University of Kent, Canterbury, CT2 7NJ, UK.
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36
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Beltran G, Novo M, Leberre V, Sokol S, Labourdette D, Guillamon JM, Mas A, François J, Rozes N. Integration of transcriptomic and metabolic analyses for understanding the global responses of low-temperature winemaking fermentations. FEMS Yeast Res 2006; 6:1167-83. [PMID: 17156014 DOI: 10.1111/j.1567-1364.2006.00106.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Wine produced at low temperature is often considered to have improved sensory qualities. To investigate the effects of temperature on winemaking, the expression patterns during the industrial fermentation process carried out at 13 degrees C and 25 degrees C were compared, and correlated with physiological and biochemical data, including viability, fermentation byproducts and lipid content of the cells. From a total of 535 ORFs that were significantly differentially expressed between the 13 degrees C and 25 degrees C fermentations, two significant transcription programmes were identified. A cold-stress response was expressed at the initial stage of the fermentation, and this was followed by a transcription pattern of upregulated genes concerned with the cell cycle, growth control and maintenance in the middle and late stages of the process at 13 degrees C with respect to 25 degrees C. These expression patterns were correlated with higher cell viability at low temperature. The other relevant transcriptomic difference was that several genes implicated in cytosolic fatty acid synthesis were downregulated, while those involved in mitochondrial short-chain fatty acid synthesis were upregulated in the fermentation process conducted at 13 degrees C with respect to that at 25 degrees C. These transcriptional changes were qualitatively correlated with improved resistance to ethanol and increased production of short-chain (C(4)-C(8)) fatty acids and their corresponding esters at 13 degrees C as compared to 25 degrees C. While this increase of ethyl esters may account in part for the improved sensory quality of wine fermented at 13 degrees C, it is still unclear how the esterification of the short-chain fatty acids takes place. On the basis of its strong upregulation at 13 degrees C, we propose a possible role of IAH1 encoding an esterase/ester synthase in this process.
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Affiliation(s)
- Gemma Beltran
- Departament de Bioquímica i Biotecnologia, Facultat d'Enologia de Tarragona, Universitat Rovira i Virgili, Tarragona, Spain
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37
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Manzano D, Busquets A, Closa M, Hoyerová K, Schaller H, Kamínek M, Arró M, Ferrer A. Overexpression of farnesyl diphosphate synthase in Arabidopsis mitochondria triggers light-dependent lesion formation and alters cytokinin homeostasis. PLANT MOLECULAR BIOLOGY 2006; 61:195-213. [PMID: 16786301 DOI: 10.1007/s11103-006-6263-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Accepted: 12/31/2005] [Indexed: 05/10/2023]
Abstract
To investigate the role of mitochondrial farnesyl diphosphate synthase (FPS) in plant isoprenoid biosynthesis we characterized transgenic Arabidopsis thaliana plants overexpressing FPS1L isoform. This overexpressed protein was properly targeted to mitochondria yielding a mature and active form of the enzyme of 40 kDa. Leaves from transgenic plants grown under continuous light exhibited symptoms of chlorosis and cell death correlating to H(2)O(2) accumulation, and leaves detached from the same plants displayed accelerated senescence. Overexpression of FPS in mitochondria also led to altered leaf cytokinin profile, with a reduction in the contents of physiologically active trans-zeatin- and isopentenyladenine-type cytokinins and their corresponding riboside monophosphates as well as enhanced levels of cis-zeatin 7-glucoside and storage cytokinin O-glucosides. Overexpression of 3-hydroxy-3-methylglutaryl coenzyme A reductase did not prevent chlorosis in plants overexpressing FPS1L, but did rescue accelerated senescence of detached leaves and restored wild-type levels of cytokinins. We propose that the overexpression of FPS1L leads to an enhanced uptake and metabolism of mevalonic acid-derived isopentenyl diphosphate and/or dimethylallyl diphosphate by mitochondria, thereby altering cytokinin homeostasis and causing a mitochondrial dysfunction that renders plants more sensitive to the oxidative stress induced by continuous light.
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Affiliation(s)
- David Manzano
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Spain
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38
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Johnson A, Gin P, Marbois BN, Hsieh EJ, Wu M, Barros MH, Clarke CF, Tzagoloff A. COQ9, a new gene required for the biosynthesis of coenzyme Q in Saccharomyces cerevisiae. J Biol Chem 2005; 280:31397-404. [PMID: 16027161 DOI: 10.1074/jbc.m503277200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Currently, eight genes are known to be involved in coenzyme Q6 biosynthesis in Saccharomyces cerevisiae. Here, we report a new gene designated COQ9 that is also required for the biosynthesis of this lipoid quinone. The respiratory-deficient pet mutant C92 was found to be deficient in coenzyme Q and to have low mitochondrial NADH-cytochrome c reductase activity, which could be restored by addition of coenzyme Q2. The mutant was used to clone COQ9, corresponding to reading frame YLR201c on chromosome XII. The respiratory defect of C92 is complemented by COQ9 and suppressed by COQ8/ABC1. The latter gene has been shown to be required for coenzyme Q biosynthesis in yeast and bacteria. Suppression by COQ8/ABC1 of C92, but not other coq9 mutants tested, has been related to an increase in the mitochondrial concentration of several enzymes of the pathway. Coq9p may either catalyze a reaction in the coenzyme Q biosynthetic pathway or have a regulatory role similar to that proposed for Coq8p.
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Affiliation(s)
- Alisha Johnson
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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Cartlidge RA, Knebel A, Peggie M, Alexandrov A, Phizicky EM, Cohen P. The tRNA methylase METTL1 is phosphorylated and inactivated by PKB and RSK in vitro and in cells. EMBO J 2005; 24:1696-705. [PMID: 15861136 PMCID: PMC1142581 DOI: 10.1038/sj.emboj.7600648] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Accepted: 03/23/2005] [Indexed: 11/09/2022] Open
Abstract
A substrate for protein kinase B (PKB)alpha in HeLa cell extracts was identified as methyltransferase-like protein-1 (METTL1), the orthologue of trm8, which catalyses the 7-methylguanosine modification of tRNA in Saccharomyces cerevisiae. PKB and ribosomal S6 kinase (RSK) both phosphorylated METTL1 at Ser27 in vitro. Ser27 became phosphorylated when HEK293 cells were stimulated with insulin-like growth factor-1 (IGF-1) and this was prevented by inhibition of phosphatidyinositol 3-kinase. The IGF-1-induced Ser27 phosphorylation did not occur in 3-phosphoinositide-dependent protein kinase-1 (PDK1)-deficient embryonic stem cells, but occurred normally in PDK1[L155E] cells, indicating that the effect of IGF-1 is mediated by PKB. METTL1 also became phosphorylated at Ser27 in response to phorbol-12-myristate 13-acetate and this was prevented by PD 184352 or pharmacological inhibition of RSK. Phosphorylation of METTL1 by PKB or RSK inactivated METTL1 in vitro, as did mutation of Ser27 to Asp or Glu. Expression of METTL1[S27D] or METTL1[S27E] did not rescue the growth phenotype of yeast lacking trm8. In contrast, expression of METTL1 or METTL1[S27A] partially rescued growth. These results demonstrate that METTL1 is inactivated by PKB and RSK in cells, and the potential implications of this finding are discussed.
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Affiliation(s)
- Robert A Cartlidge
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
| | - Axel Knebel
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
| | - Mark Peggie
- Division of Signal Transduction Therapy, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
| | - Andrei Alexandrov
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, NY, USA
| | - Eric M Phizicky
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine, Rochester, NY, USA
| | - Philip Cohen
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
- Division of Signal Transduction Therapy, School of Life Sciences, MSI/WTB complex, University of Dundee, Dundee, UK
- MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB complex, University of Dundee, Dow Street, Dundee DD1 5EH, UK. Tel.: +44 1382 344238; Fax: 44 1382 223778; E-mail:
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40
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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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41
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Manzano D, Fernández-Busquets X, Schaller H, González V, Boronat A, Arró M, Ferrer A. The metabolic imbalance underlying lesion formation in Arabidopsis thaliana overexpressing farnesyl diphosphate synthase (isoform 1S) leads to oxidative stress and is triggered by the developmental decline of endogenous HMGR activity. PLANTA 2004; 219:982-992. [PMID: 15605175 DOI: 10.1007/s00425-004-1301-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2003] [Accepted: 04/16/2004] [Indexed: 05/24/2023]
Abstract
Overexpression of Arabidopsis thaliana farnesyl diphosphate synthase isoform 1S (FPS1S) in transgenic A. thaliana (L.) Heynh. leads to necrotic lesion formation in leaves in planta and to premature senescence in detached leaves [A. Masferrer et al. (2002) Plant J 30:123-132]. Here we report that leaves of plants overexpressing FPS1S with symptoms of necrosis show increased H2O2 formation and induction of both the pathogenesis-related 1 (PR-1) and the alternative oxidase 1a (AOX1a) genes. These findings indicate that plants overexpressing FPS1S should be considered as lesion-mimic mutants and lead us to propose that H2O2 is the main inducing agent of necrosis in these plants. The onset of necrosis appears in a developmentally regulated manner that correlates with the developmental decline of endogenous 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity. Accordingly, constitutive overexpression of HMGR in plants overexpressing FPS1S prevents both necrosis and premature senescence. These observations demonstrate that both phenotypes are due to an insufficient supply of mevalonic acid and support the notion that the metabolic imbalance associated with FPS1S overexpression is, in fact, triggered by the developmental decline of HMGR activity. We also show that overexpression of FPS1S alleviates growth inhibition caused by overexpression of the catalytic domain of isoform HMGR1S. Overall, our results reinforce the view that the levels of specific intermediates of the mevalonic acid pathway must be strictly controlled, particularly those located at branch-point positions, in order to avoid deleterious effects on plant growth and development.
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Affiliation(s)
- David Manzano
- Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Universitat de Barcelona, Av. Diagonal 643, 08028, Spain
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42
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Moosmann B, Behl C. Selenoproteins, Cholesterol-Lowering Drugs, and the Consequences Revisiting of the Mevalonate Pathway. Trends Cardiovasc Med 2004; 14:273-81. [PMID: 15542379 DOI: 10.1016/j.tcm.2004.08.003] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) and peroxisome proliferator-activated receptor alpha activators (fibrates) are the backbone of pharmacologic hypercholesterolemia and dyslipidemia treatment. Many of their clinical effects, however, are still enigmatic. This article describes how a side road of the mevalonate pathway, characterized in recent years, can rationalize a major fraction of these unexplained observations. This side road is the enzymatic isopentenylation of selenocysteine-tRNA([Ser]Sec) (Sec-tRNA), the singular tRNA to decode the unusual amino acid selenocysteine. The functionally indispensable isopentenylation of Sec-tRNA requires a unique intermediate from the mevalonate pathway, isopentenyl pyrophosphate, which concomitantly constitutes the central building block for cholesterol biosynthesis, and whose formation is suppressed by statins and fibrates. The resultant inhibition of Sec-tRNA isopentenylation profoundly decreases selenoprotein expression. This effect might seamlessly explain the immunosuppressive, redox, endothelial, sympatholytic, and thyroidal effects of statins and fibrates as well as their common side effects and drug interactions.
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Affiliation(s)
- Bernd Moosmann
- Department of Pathobiochemistry, Johannes Gutenberg University, Medical School, Duesbergweg 6, 55099 Mainz, Germany
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Abstract
Statins are possibly the most effective drugs for the prevention and treatment of hypercholesterolaemia and coronary heart disease. They are generally well tolerated, however, they do cause some unusual side-effects with potentially severe consequences, most prominently myopathy or rhabdomyolysis and polyneuropathy. We noted that the pattern of side-effects associated with statins resembles the pathology of selenium deficiency, and postulated that the mechanism lay in a well established, but often overlooked, biochemical pathway--the isopentenylation of selenocysteine-tRNA([Ser]Sec). A negative effect of statins on selenoprotein synthesis does seem to explain many of the enigmatic effects and side-effects of statins, in particular, statin-induced myopathy.
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Affiliation(s)
- Bernd Moosmann
- Department of Pathobiochemistry, Johannes Gutenberg University, Medical School, Mainz, Germany
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44
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Willis IM, Desai N, Upadhya R. Signaling repression of transcription by RNA polymerase III in yeast. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2004; 77:323-53. [PMID: 15196897 DOI: 10.1016/s0079-6603(04)77009-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Ian M Willis
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461 USA
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45
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Anand M, Valente L, Carr-Schmid A, Munshi R, Olarewaju O, Ortiz PA, Kinzy TG. Translation elongation factor 1 functions in the yeast Saccharomyces cerevisiae. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 66:439-48. [PMID: 12762046 DOI: 10.1101/sqb.2001.66.439] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- M Anand
- Department of Molecular Genetics and Microbiology, UMDNJ Robert Wood Johnson Medical School, New Jersey, USA
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46
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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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47
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Kamińska J, Grabińska K, Kwapisz M, Sikora J, Smagowicz WJ, Palamarczyk G, Zoładek T, Boguta M. The isoprenoid biosynthetic pathway in Saccharomyces cerevisiae is affected in a maf1-1 mutant with altered tRNA synthesis. FEMS Yeast Res 2002; 2:31-7. [PMID: 12702319 DOI: 10.1111/j.1567-1364.2002.tb00066.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
tRNA isopentenylation is a branch of an isoprenoid pathway in yeast. There is a competition for a substrate between isoprenoid biosynthetic enzyme Erg20p and tRNA isopentenyltransferase. Here we studied the direct effect of elevated tRNA biosynthesis on ERG20 expression. The maf1-1 mutant of Saccharomyces cerevisiae that has enhanced cellular tRNA levels was used. We show that both ERG20 transcript and Erg20 protein levels are increased in maf1-1. Additionally, maf1-1 leads to decreased ergosterol content in the cells. These effects of maf1-1 are dependent on functional tRNA isopentenyltransferase. Our results indicate that a complex regulation of the isoprenoid pathway involves also an effect of changes in tRNA biosynthesis.
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Affiliation(s)
- Joanna Kamińska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
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48
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Abstract
During the last decade several novel yeast genes encoding proteins related to the PPP family of Ser/Thr protein phosphatases have been discovered and their functional characterization initiated. Most of these novel phosphatases display intriguing structural features and/or are involved in a number of important functions, such as cell cycle regulation, protein synthesis and maintenance of cellular integrity. While in some cases these genes appear to be restricted to fungi, in others similar proteins can be found in higher eukaryotes. This review will summarize the latest advances in our understanding about how these phosphatases are regulated and fulfil their functions in the yeast cell.
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Affiliation(s)
- Joaquín Ariño
- Department de Bioquímica i Biologia Molecular, Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra Spain.
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49
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Pluta K, Lefebvre O, Martin NC, Smagowicz WJ, Stanford DR, Ellis SR, Hopper AK, Sentenac A, Boguta M. Maf1p, a negative effector of RNA polymerase III in Saccharomyces cerevisiae. Mol Cell Biol 2001; 21:5031-40. [PMID: 11438659 PMCID: PMC87229 DOI: 10.1128/mcb.21.15.5031-5040.2001] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although yeast RNA polymerase III (Pol III) and the auxiliary factors TFIIIC and TFIIIB are well characterized, the mechanisms of class III gene regulation are poorly understood. Previous studies identified MAF1, a gene that affects tRNA suppressor efficiency and interacts genetically with Pol III. We show here that tRNA levels are elevated in maf1 mutant cells. In keeping with the higher levels of tRNA observed in vivo, the in vitro rate of Pol III RNA synthesis is significantly increased in maf1 cell extracts. Mutations in the RPC160 gene encoding the largest subunit of Pol III which reduce tRNA levels were identified as suppressors of the maf1 growth defect. Interestingly, Maf1p is located in the nucleus and coimmunopurifies with epitope-tagged RNA Pol III. These results indicate that Maf1p acts as a negative effector of Pol III synthesis. This potential regulator of Pol III transcription is likely conserved since orthologs of Maf1p are present in other eukaryotes, including humans.
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Affiliation(s)
- K Pluta
- Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02 106 Warsaw, Poland
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50
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Fisher AJ, Rosenstiel TN, Shirk MC, Fall R. Nonradioactive assay for cellular dimethylallyl diphosphate. Anal Biochem 2001; 292:272-9. [PMID: 11355861 DOI: 10.1006/abio.2001.5079] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A sensitive, nonradioactive method was developed to measure cellular levels of dimethylallyl diphosphate (DMAPP), a central intermediate of isoprenoid metabolism in nature. The assay is based on the hydrolysis of DMAPP in acid to the volatile hydrocarbon isoprene (2-methyl-1,3-butadiene), with subsequent analysis of isoprene by headspace gas chromatography with reduction gas detection. In the assay, cell samples are directly acidified with 4 M H(2)SO(4) in sealed reaction vials. Therefore, there is no need to extract metabolites, purify them, and keep them stable prior to analysis, and degradative enzymatic activities are destroyed. DMAPP levels of 23 +/- 4 nmol (g fresh weight)(-1) [ca. 85 nmol (g dry weight)(-1)] and 80 +/- 14 nmol (g fresh weight)(-1) [ca. 296 nmol (g dry weight)(-1)] were measured in dark- and light-adapted leaves of Populus deltoides (Eastern cottonwood), respectively. Evidence is presented to show that DMAPP is the major leaf metabolite giving rise to isoprene following acid hydrolysis. DMAPP levels in Bacillus subtilis and Saccharomyces cerevisiae were determined to be 40.8 +/- 16.7 pmol (OD(600))(-1) [ca. 638 pmol (mg dry weight)(-1)] and 6.3 +/- 3.7 pmol (OD(600))(-1) [ca. 139 pmol (mg dry weight)(-1)], respectively. The method should be suitable for any cell or tissue type and isolated cellular organelles.
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Affiliation(s)
- A J Fisher
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA
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