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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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2
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Fernandes De Abreu DA, Salinas-Giegé T, Drouard L, Remy JJ. Alanine tRNAs Translate Environment Into Behavior in Caenorhabditis elegans. Front Cell Dev Biol 2020; 8:571359. [PMID: 33195203 PMCID: PMC7662486 DOI: 10.3389/fcell.2020.571359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 10/12/2020] [Indexed: 12/16/2022] Open
Abstract
Caenorhabditis elegans nematodes produce and maintain imprints of attractive chemosensory cues to which they are exposed early in life. Early odor-exposure increases adult chemo-attraction to the same cues. Imprinting is transiently or stably inherited, depending on the number of exposed generations. We show here that the Alanine tRNA (UGC) plays a central role in regulating C. elegans chemo-attraction. Naive worms fed on tRNAAla (UGC) purified from odor-experienced worms, acquire odor-specific imprints. Chemo-attractive responses require the tRNA-modifying Elongator complex sub-units 1 (elpc-1) and 3 (elpc-3) genes. elpc-3 deletions impair chemo-attraction, which is fully restored by wild-type tRNAAla (UGC) feeding. A stably inherited decrease of odor-specific responses ensues from early odor-exposition of elpc-1 deletion mutants. tRNAAla (UGC) may adopt various chemical forms to mediate the cross-talk between innately-programmed and environment-directed chemo-attractive behavior.
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Affiliation(s)
- Diana Andrea Fernandes De Abreu
- Genes, Environment, Plasticity, Institut Sophia Agrobiotech ISA UMR CNRS 7254, INRAE 1355, Université Nice Côte d’Azur, Sophia-Antipolis, France
| | - Thalia Salinas-Giegé
- Institut de Biologie Moléculaire des Plantes-CNRS, Université de Strasbourg, Strasbourg, France
| | - Laurence Drouard
- Institut de Biologie Moléculaire des Plantes-CNRS, Université de Strasbourg, Strasbourg, France
| | - Jean-Jacques Remy
- Genes, Environment, Plasticity, Institut Sophia Agrobiotech ISA UMR CNRS 7254, INRAE 1355, Université Nice Côte d’Azur, Sophia-Antipolis, France
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3
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Eisermann I, Motyka V, Kümmel S, Dobrev PI, Hübner K, Deising HB, Wirsel SGR. CgIPT1 is required for synthesis of cis-zeatin cytokinins and contributes to stress tolerance and virulence in Colletotrichum graminicola. Fungal Genet Biol 2020; 143:103436. [PMID: 32693088 DOI: 10.1016/j.fgb.2020.103436] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 06/09/2020] [Accepted: 07/14/2020] [Indexed: 10/23/2022]
Abstract
We have previously shown that the maize pathogen Colletotrichum graminicola is able to synthesise cytokinins (CKs). However, it remained unsettled whether fungal CK production is essential for virulence in this hemibiotrophic fungus. Here, we identified a candidate gene, CgIPT1, that is homologous to MOD5 of Saccharomyces cerevisiae and genes from other fungi and plants, which encode tRNA-isopentenyltransferases (IPTs). We show that the wild type strain mainly synthesises cis-zeatin-type (cisZ) CKs whereas ΔCgipt1 mutants are severely impeded to do so. The spectrum of CKs produced confirms bioinformatical analyses predicting that CgIpt1 is a tRNA-IPT. The virulence of the ΔCgipt1 mutants is moderately reduced. Furthermore, the mutants exhibit increased sensitivities to osmotic stress imposed by sugar alcohols and salts, as well as cell wall stress imposed by Congo red. Amendment of media with CKs did not reverse this phenotype suggesting that fungal-derived CKs do not explain the role of CgIpt1 in mediating abiotic stress tolerance. Moreover, the mutants still cause green islands on senescing maize leaves indicating that the cisZ-type CKs produced by the fungus do not cause this phenotype.
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Affiliation(s)
- Iris Eisermann
- Institut für Agrar- und Ernährungswissenschaften, Naturwissenschaftliche Fakultät III, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 3, D-06120 Halle (Saale), Germany
| | - Václav Motyka
- Institute of Experimental Botany of the Czech Academy of Sciences, Rozvojová 263, CZ-165 02 Prague 6, Czech Republic
| | - Stefanie Kümmel
- Institut für Agrar- und Ernährungswissenschaften, Naturwissenschaftliche Fakultät III, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 3, D-06120 Halle (Saale), Germany
| | - Petre I Dobrev
- Institute of Experimental Botany of the Czech Academy of Sciences, Rozvojová 263, CZ-165 02 Prague 6, Czech Republic
| | - Konstantin Hübner
- Institut für Agrar- und Ernährungswissenschaften, Naturwissenschaftliche Fakultät III, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 3, D-06120 Halle (Saale), Germany
| | - Holger B Deising
- Institut für Agrar- und Ernährungswissenschaften, Naturwissenschaftliche Fakultät III, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 3, D-06120 Halle (Saale), Germany
| | - Stefan G R Wirsel
- Institut für Agrar- und Ernährungswissenschaften, Naturwissenschaftliche Fakultät III, Martin-Luther-Universität Halle-Wittenberg, Betty-Heimann-Str. 3, D-06120 Halle (Saale), Germany.
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Aoki MM, Emery RJN, Anjard C, Brunetti CR, Huber RJ. Cytokinins in Dictyostelia - A Unique Model for Studying the Functions of Signaling Agents From Species to Kingdoms. Front Cell Dev Biol 2020; 8:511. [PMID: 32714926 PMCID: PMC7316887 DOI: 10.3389/fcell.2020.00511] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 05/28/2020] [Indexed: 02/06/2023] Open
Abstract
Cytokinins (CKs) are a diverse group of evolutionarily significant growth-regulating molecules. While the CK biosynthesis and signal transduction pathways are the most well-understood in plant systems, these molecules have been identified in all kingdoms of life. This review follows the recent discovery of an expanded CK profile in the social amoeba, Dictyostelium discoideum. A comprehensive review on the present knowledge of CK biosynthesis, signal transduction, and CK-small molecule interactions within members of Dictyostelia will be summarized. In doing so, the utility of social amoebae will be highlighted as a model system for studying the evolution of these hormone-like signaling agents, which will set the stage for future research in this area.
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Affiliation(s)
- Megan M Aoki
- Department of Biology, Trent University, Peterborough, ON, Canada
| | - R J Neil Emery
- Department of Biology, Trent University, Peterborough, ON, Canada
| | - Christophe Anjard
- Institut Lumière Matière, CNRS UMR 5306, Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
| | - Craig R Brunetti
- Department of Biology, Trent University, Peterborough, ON, Canada
| | - Robert J Huber
- Department of Biology, Trent University, Peterborough, ON, Canada
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5
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Dabravolski S. Multi-faceted nature of the tRNA isopentenyltransferase. FUNCTIONAL PLANT BIOLOGY : FPB 2020; 47:475-485. [PMID: 32345433 DOI: 10.1071/fp19255] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 12/26/2019] [Indexed: 06/11/2023]
Abstract
Transfer RNA isopentenylation an adenine 37 position (A37) is a universal modification known in prokaryotes and eukaryotes. A set of highly homologous enzymes catalyse a series of reactions, leading to tRNA modifications, aimed to increase adaptation to environmental condition through the control of translation efficiency and reading frame maintenance. Transfer RNA-isopentenylation-related (TI-related) functions are well studied in bacteria, mitochondria of yeast and human, but completely unexplored in plants. Transfer RNA-isopentenylation-unrelated (TI-unrelated) functions participate in adaptation to environmental stresses via the regulation of sterol metabolism, gene silencing/suppression and amyloid fibrils formation. TI-unrelated functions are mostly studied in yeast. Finally, the degradation of A37-modified tRNA releases a set of bioactive compounds known as cis-cytokinins. Although all organisms are able to produce cis-cytokinins, its physiological role is still a matter of debates. For several species of bacteria and fungi, cis-cytokinins are known to play a crucial role in pathogenesis. In mammalian and human models cis-cytokinins have tumour-suppressing and anti-inflammation effects. This review aims to summarise current knowledge of the TI-related and TI-unrelated functions and main bioactive by-products of isopentenylated tRNA degradation.
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Affiliation(s)
- Siarhei Dabravolski
- Department of Molecular Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelu 27, 78371 Olomouc, Czech Republic.
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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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Trotta E. RNA polymerase II (RNAP II)-associated factors are recruited to tRNA loci, revealing that RNAP II- and RNAP III-mediated transcriptions overlap in yeast. J Biol Chem 2019; 294:12349-12358. [PMID: 31235518 PMCID: PMC6699833 DOI: 10.1074/jbc.ra119.008529] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 06/19/2019] [Indexed: 07/24/2023] Open
Abstract
In yeast (Saccharomyces cerevisiae), the synthesis of tRNAs by RNA polymerase III (RNAP III) down-regulates the transcription of the nearby RNAP II-transcribed genes by a mechanism that is poorly understood. To clarify the basis of this tRNA gene-mediated (TGM) silencing, here, conducting a bioinformatics analysis of available ChIP-chip and ChIP-sequencing genomic data from yeast, we investigated whether the RNAP III transcriptional machinery can recruit protein factors required for RNAP II transcription. An analysis of 46 genome-wide protein-density profiles revealed that 12 factors normally implicated in RNAP II-mediated gene transcription are more enriched at tRNA than at mRNA loci. These 12 factors typically have RNA-binding properties, participate in the termination stage of the RNAP II transcription, and preferentially localize to the tRNA loci by a mechanism that apparently is based on the RNAP III transcription level. The factors included two kinases of RNAP II (Bur1 and Ctk1), a histone demethylase (Jhd2), and a mutated form of a nucleosome-remodeling factor (Spt6) that have never been reported to be recruited to tRNA loci. Moreover, we show that the expression levels of RNAP II-transcribed genes downstream of tRNA loci correlate with the distance from the tRNA gene by a mechanism that depends on their orientation. These results are consistent with the notion that pre-tRNAs recruit RNAP II-associated factors, thereby reducing the availability of these factors for RNAP II transcription and contributing, at least in part, to the TGM-silencing mechanism.
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Affiliation(s)
- Edoardo Trotta
- Institute of Translational Pharmacology, Consiglio Nazionale delle Ricerche (CNR), Roma 00133, Italy.
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Chen Y, Bai B, Yan H, Wen F, Qin D, Jander G, Xia Q, Wang G. Systemic disruption of the homeostasis of transfer RNA isopentenyltransferase causes growth and development abnormalities in Bombyx mori. INSECT MOLECULAR BIOLOGY 2019; 28:380-391. [PMID: 30548717 DOI: 10.1111/imb.12561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Isopentenylation at A37 (i6 A37) of some transfer RNAs (tRNAs) plays a vital role in regulating the efficiency and fidelity of protein synthesis. However, whether insects, which are well known for their highly efficient protein synthesis machinery, employ this regulatory mechanism remains uninvestigated. In the current study, a candidate tRNA isopentenyltransferase (IPT) gene with three alternative splicing isoforms (BmIPT1-BmIPT3) was identified in Bombyx mori (silkworm). Only BmIPT1 could complement a yeast mutant lacking tRNA IPT. Phylogenetic analysis showed that silkworm tRNA IPT is conserved in the Lepidoptera. BmIPT was expressed in all B. mori tissues and organs that were investigated, but was expressed at a significantly higher level in silk glands of the fourth instar compared to the first day of the fifth instar. Interestingly, BmIPT was expressed at a significantly higher level in the domesticated silkworm, B. mori, than in wild Bombyx mandarina in multiple tissues and organs. Knock-down of BmIPT by RNA interference caused severe abnormalities in silk spinning and metamorphosis. Constitutive overexpression of BmIPT1 using a cytoplasmic actin 4 promoter in B. mori raised its messenger RNA level more than sixfold compared with nontransgenic insects and led to significant decreases in the body weight and cocoon shell ratio. Together, these results confirm the first functional tRNA IPT in insects and show that a suitable expression level of tRNA IPT is vital for silk spinning, normal growth, and metamorphosis. Thus, i6 A modification at position A37 in tRNA probably plays an important role in B. mori protein synthesis.
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Affiliation(s)
- Y Chen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - B Bai
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - H Yan
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - F Wen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - D Qin
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - G Jander
- Boyce Thompson Institute, Ithaca, NY, USA
| | - Q Xia
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing Engineering and Technology Research Center for Novel Silk Materials, Southwest University, Chongqing, China
| | - G Wang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing Engineering and Technology Research Center for Novel Silk Materials, Southwest University, Chongqing, China
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de Crécy-Lagard V, Boccaletto P, Mangleburg CG, Sharma P, Lowe TM, Leidel SA, Bujnicki JM. Matching tRNA modifications in humans to their known and predicted enzymes. Nucleic Acids Res 2019; 47:2143-2159. [PMID: 30698754 PMCID: PMC6412123 DOI: 10.1093/nar/gkz011] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 12/28/2018] [Accepted: 01/10/2019] [Indexed: 12/25/2022] Open
Abstract
tRNA are post-transcriptionally modified by chemical modifications that affect all aspects of tRNA biology. An increasing number of mutations underlying human genetic diseases map to genes encoding for tRNA modification enzymes. However, our knowledge on human tRNA-modification genes remains fragmentary and the most comprehensive RNA modification database currently contains information on approximately 20% of human cytosolic tRNAs, primarily based on biochemical studies. Recent high-throughput methods such as DM-tRNA-seq now allow annotation of a majority of tRNAs for six specific base modifications. Furthermore, we identified large gaps in knowledge when we predicted all cytosolic and mitochondrial human tRNA modification genes. Only 48% of the candidate cytosolic tRNA modification enzymes have been experimentally validated in mammals (either directly or in a heterologous system). Approximately 23% of the modification genes (cytosolic and mitochondrial combined) remain unknown. We discuss these 'unidentified enzymes' cases in detail and propose candidates whenever possible. Finally, tissue-specific expression analysis shows that modification genes are highly expressed in proliferative tissues like testis and transformed cells, but scarcely in differentiated tissues, with the exception of the cerebellum. Our work provides a comprehensive up to date compilation of human tRNA modifications and their enzymes that can be used as a resource for further studies.
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Affiliation(s)
- Valérie de Crécy-Lagard
- Department of Microbiology and Cell Sciences, University of Florida, Gainesville, FL 32611, USA
- Cancer and Genetic Institute, University of Florida, Gainesville, FL 32611, USA
| | - Pietro Boccaletto
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, ul. Trojdena 4, 02-109 Warsaw, Poland
| | - Carl G Mangleburg
- Department of Microbiology and Cell Sciences, University of Florida, Gainesville, FL 32611, USA
| | - Puneet Sharma
- Max Planck Research Group for RNA Biology, Max Planck Institute for Molecular Biomedicine, 48149 Muenster, Germany
- Cells-in-Motion Cluster of Excellence, University of Muenster, 48149 Muenster, Germany
| | - Todd M Lowe
- Department of Biomolecular Engineering, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Sebastian A Leidel
- Max Planck Research Group for RNA Biology, Max Planck Institute for Molecular Biomedicine, 48149 Muenster, Germany
- Cells-in-Motion Cluster of Excellence, University of Muenster, 48149 Muenster, Germany
- Research Group for RNA Biochemistry, Institute of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - Janusz M Bujnicki
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, ul. Trojdena 4, 02-109 Warsaw, Poland
- Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, ul. Umultowska 89, 61-614 Poznań, Poland
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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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11
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Manipulation of cytokinin level in the ergot fungus Claviceps purpurea emphasizes its contribution to virulence. Curr Genet 2018; 64:1303-1319. [PMID: 29850931 DOI: 10.1007/s00294-018-0847-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 05/15/2018] [Accepted: 05/28/2018] [Indexed: 11/30/2022]
Abstract
Pathogen-derived cytokinins (CKs) have been recognized as important virulence factor in several host-pathogen interactions and it was demonstrated multiple times that phytopathogenic fungi form CKs via the tRNA degradation pathway. In contrast to previous studies, the focus of this study is on the second step of CK formation and CK degradation to improve our understanding of the biosynthesis in fungi on the one hand, and to understand CK contribution to the infection process of Claviceps purpurea on the other hand. The ergot fungus Claviceps purpurea is a biotrophic phytopathogen with a broad host range including economically important crops causing harvest intoxication upon infection. Its infection process is restricted to unfertilized ovaries without causing macroscopic defense symptoms. Thus, sophisticated host manipulation strategies are implicated. The cytokinin (CK) plant hormones are known to regulate diverse plant cell processes, and several plant pathogens alter CK levels during infection. C. purpurea synthesizes CKs via two mechanisms, and fungus-derived CKs influence the host-pathogen interaction but not fungus itself. CK deficiency in fungi with impact on virulence has only been achieved to date by deletion of a tRNA-ipt gene that is also involved in a process of translation regulation. To obtain a better understanding of CK biosynthesis and CKs' contribution to the plant-fungus interaction, we applied multiple approaches to generate strains with altered or depleted CK content. The first approach is based on deletion of the two CK phosphoribohydrolase (LOG)-encoding genes, which are believed to be essential for the release of active CKs. Single and double deletion strains were able to produce all types of CKs. Apparently, log gene products are dispensable for the formation of CKs and so alternative activation pathways must be present. The CK biosynthesis pathway remains unaffected in the second approach, because it is based on heterologous overexpression of CK-degrading enzymes from maize (ZmCKX1). Zmckx1 overexpressing C. purpurea strains shows strong CKX activity and drastically reduced CK levels. The strains are impaired in virulence, which reinforces the assumption that fungal-derived CKs are crucial for full virulence. Taken together, this study comprises the first analysis of a log depletion mutant that proved the presence of alternative cytokinin activation pathways in fungi and showed that heterologous CKX expression is a suitable approach for CK level reduction.
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12
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Koh CS, Sarin LP. Transfer RNA modification and infection – Implications for pathogenicity and host responses. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:419-432. [DOI: 10.1016/j.bbagrm.2018.01.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 01/04/2018] [Accepted: 01/19/2018] [Indexed: 12/19/2022]
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13
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Arimbasseri GA. Interactions between RNAP III transcription machinery and tRNA processing factors. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2018; 1861:354-360. [PMID: 29428193 DOI: 10.1016/j.bbagrm.2018.02.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 02/06/2018] [Accepted: 02/06/2018] [Indexed: 10/18/2022]
Abstract
Eukaryotes have at least three nuclear RNA polymerases to carry out transcription. While RNA polymerases I and II are responsible for ribosomal RNA transcription and messenger RNA transcription, respectively, RNA Polymerase III transcribes approximately up to 300 nt long noncoding RNAs, including tRNA. For all three RNAPs, the nascent transcripts generated undergo extensive post-transcriptional processing. Transcription of mRNAs by RNAP II and their processing are coupled with the aid of the C-terminal domain of the RNAP II. RNAP I transcription and the processing of its transcripts are co-localized to the nucleolus and to some extent, rRNA processing occurs co-transcriptionally. Here, I review the current evidence for the interaction between tRNA processing factors and RNA polymerase III. These interactions include the moonlighting functions of tRNA processing factors in RNAP III transcription and the indirect effect of tRNA transcription levels on tRNA modification machinery.
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Affiliation(s)
- G Aneeshkumar Arimbasseri
- Molecular Genetics Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
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14
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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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15
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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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16
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Waller TJ, Read DF, Engelke DR, Smaldino PJ. The human tRNA-modifying protein, TRIT1, forms amyloid fibers in vitro. Gene 2016; 612:19-24. [PMID: 27984194 DOI: 10.1016/j.gene.2016.10.041] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 10/24/2016] [Accepted: 10/27/2016] [Indexed: 12/19/2022]
Abstract
TRIT1 is a highly conserved tRNA isopentenyl transferase that modifies a subset of tRNAs in human cells and is a candidate tumor suppressor in lung cancer in certain ethnic populations. The yeast homologue, Mod5, has similar tRNA-modifying functions in the cytoplasm and is required for the transcriptional silencing activity of RNA polymerase II promoters near tRNA genes in the nucleus, a phenomenon termed tRNA gene mediated (tgm) silencing. Furthermore, Mod5 can fold into amyloid fibers in vitro and in vivo, which confers resistance to certain fungicides in yeast. Since TRIT1 complements both tRNA modifying and tgm-silencing activities in yeast where the Mod5 gene has been deleted, it seemed possible that TRIT1 might also have amyloid-forming capabilities. Here we show that TRIT1, like Mod5, directly binds to tRNAs that are both substrate and non-substrates for modification with similar affinity, and to an unstructured, non-tRNA. Binding appears to involve distinct protein-RNA multimers which decrease in electrophoretic mobility as the protein to RNA ratio increases. Furthermore, we characterize TRIT1 as a novel human amyloid fiber forming protein. We discuss these data in light of TRIT1's functional roles and possible implications for disease.
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Affiliation(s)
- T J Waller
- Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, United States
| | - D F Read
- Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, United States
| | - D R Engelke
- Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, United States; University of Denver, Aurora, CO 80045, United States.
| | - P J Smaldino
- Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, United States; Biology, Ball State University, Muncie, IN 47306, United States.
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17
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Pontvianne F, Carpentier MC, Durut N, Pavlištová V, Jaške K, Schořová Š, Parrinello H, Rohmer M, Pikaard CS, Fojtová M, Fajkus J, Sáez-Vásquez J. Identification of Nucleolus-Associated Chromatin Domains Reveals a Role for the Nucleolus in 3D Organization of the A. thaliana Genome. Cell Rep 2016; 16:1574-1587. [PMID: 27477271 PMCID: PMC5279810 DOI: 10.1016/j.celrep.2016.07.016] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 05/24/2016] [Accepted: 07/03/2016] [Indexed: 11/27/2022] Open
Abstract
The nucleolus is the site of rRNA gene transcription, rRNA processing, and ribosome biogenesis. However, the nucleolus also plays additional roles in the cell. We isolated nucleoli using fluorescence-activated cell sorting (FACS) and identified nucleolus-associated chromatin domains (NADs) by deep sequencing, comparing wild-type plants and null mutants for the nucleolar protein NUCLEOLIN 1 (NUC1). NADs are primarily genomic regions with heterochromatic signatures and include transposable elements (TEs), sub-telomeric regions, and mostly inactive protein-coding genes. However, NADs also include active rRNA genes and the entire short arm of chromosome 4 adjacent to them. In nuc1 null mutants, which alter rRNA gene expression and overall nucleolar structure, NADs are altered, telomere association with the nucleolus is decreased, and telomeres become shorter. Collectively, our studies reveal roles for NUC1 and the nucleolus in the spatial organization of chromosomes as well as telomere maintenance.
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Affiliation(s)
- Frédéric Pontvianne
- CNRS, Laboratoire Génome et Développement des Plantes, UMR5096, 66860 Perpignan, France; Université de Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR5096, 66860 Perpignan, France; Department of Biology and Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA.
| | - Marie-Christine Carpentier
- CNRS, Laboratoire Génome et Développement des Plantes, UMR5096, 66860 Perpignan, France; Université de Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR5096, 66860 Perpignan, France
| | - Nathalie Durut
- CNRS, Laboratoire Génome et Développement des Plantes, UMR5096, 66860 Perpignan, France; Université de Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR5096, 66860 Perpignan, France
| | - Veronika Pavlištová
- Central European Institute of Technology and Faculty of Science, Masaryk University, 62500 Brno, Czech Republic
| | - Karin Jaške
- Central European Institute of Technology and Faculty of Science, Masaryk University, 62500 Brno, Czech Republic
| | - Šárka Schořová
- Central European Institute of Technology and Faculty of Science, Masaryk University, 62500 Brno, Czech Republic
| | | | | | - Craig S Pikaard
- Department of Biology and Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA; Howard Hughes Medical Institute, Indiana University, Bloomington, IN 47405, USA
| | - Miloslava Fojtová
- Central European Institute of Technology and Faculty of Science, Masaryk University, 62500 Brno, Czech Republic
| | - Jiří Fajkus
- Central European Institute of Technology and Faculty of Science, Masaryk University, 62500 Brno, Czech Republic
| | - Julio Sáez-Vásquez
- CNRS, Laboratoire Génome et Développement des Plantes, UMR5096, 66860 Perpignan, France; Université de Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR5096, 66860 Perpignan, France
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18
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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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19
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RNA Polymerase III Advances: Structural and tRNA Functional Views. Trends Biochem Sci 2016; 41:546-559. [PMID: 27068803 DOI: 10.1016/j.tibs.2016.03.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 03/03/2016] [Accepted: 03/09/2016] [Indexed: 12/25/2022]
Abstract
RNA synthesis in eukaryotes is divided among three RNA polymerases (RNAPs). RNAP III transcribes hundreds of tRNA genes and fewer additional short RNA genes. We survey recent work on transcription by RNAP III including an atomic structure, mechanisms of action, interactions with chromatin and retroposons, and a conserved link between its activity and a tRNA modification that enhances mRNA decoding. Other new work suggests important mechanistic connections to oxidative stress, autoimmunity and cancer, embryonic stem cell pluripotency, and tissue-specific developmental effects. We consider that, for some of its complex functions, variation in RNAP III activity levels lead to nonuniform changes in tRNAs that can shift the translation profiles of key codon-biased mRNAs with resultant phenotypes or disease states.
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20
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Chanclud E, Kisiala A, Emery NRJ, Chalvon V, Ducasse A, Romiti-Michel C, Gravot A, Kroj T, Morel JB. Cytokinin Production by the Rice Blast Fungus Is a Pivotal Requirement for Full Virulence. PLoS Pathog 2016; 12:e1005457. [PMID: 26900703 PMCID: PMC4765853 DOI: 10.1371/journal.ppat.1005457] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 01/25/2016] [Indexed: 12/22/2022] Open
Abstract
Plants produce cytokinin (CK) hormones for controlling key developmental processes like source/sink distribution, cell division or programmed cell-death. Some plant pathogens have been shown to produce CKs but the function of this mimicry production by non-tumor inducing pathogens, has yet to be established. Here we identify a gene required for CK biosynthesis, CKS1, in the rice blast fungus Magnaporthe oryzae. The fungal-secreted CKs are likely perceived by the plant during infection since the transcriptional regulation of rice CK-responsive genes is altered in plants infected by the mutants in which CKS1 gene was deleted. Although cks1 mutants showed normal in vitro growth and development, they were severely affected for in planta growth and virulence. Moreover, we showed that the cks1 mutant triggered enhanced induction of plant defenses as manifested by an elevated oxidative burst and expression of defense-related markers. In addition, the contents of sugars and key amino acids for fungal growth were altered in and around the infection site by the cks1 mutant in a different manner than by the control strain. These results suggest that fungal-derived CKs are key effectors required for dampening host defenses and affecting sugar and amino acid distribution in and around the infection site.
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Affiliation(s)
- Emilie Chanclud
- Université Montpellier, UMR BGPI INRA/CIRAD/SupAgro, Montpellier, France
| | - Anna Kisiala
- Biology Department, Trent University, Peterborough, Ontario, Canada
- Department of Plant Genetics, Physiology and Biotechnology, University of Technology and Life Sciences, Bydgoszcz, Poland
| | - Neil R. J Emery
- Biology Department, Trent University, Peterborough, Ontario, Canada
| | | | | | | | | | - Thomas Kroj
- INRA, UMR BGPI INRA/CIRAD/SupAgro, Montpellier, France
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21
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Armengod ME, Meseguer S, Villarroya M, Prado S, Moukadiri I, Ruiz-Partida R, Garzón MJ, Navarro-González C, Martínez-Zamora A. Modification of the wobble uridine in bacterial and mitochondrial tRNAs reading NNA/NNG triplets of 2-codon boxes. RNA Biol 2015; 11:1495-507. [PMID: 25607529 DOI: 10.4161/15476286.2014.992269] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Posttranscriptional modification of the uridine located at the wobble position (U34) of tRNAs is crucial for optimization of translation. Defects in the U34 modification of mitochondrial-tRNAs are associated with a group of rare diseases collectively characterized by the impairment of the oxidative phosphorylation system. Retrograde signaling pathways from mitochondria to nucleus are involved in the pathophysiology of these diseases. These pathways may be triggered by not only the disturbance of the mitochondrial (mt) translation caused by hypomodification of tRNAs, but also as a result of nonconventional roles of mt-tRNAs and mt-tRNA-modifying enzymes. The evolutionary conservation of these enzymes supports their importance for cell and organismal functions. Interestingly, bacterial and eukaryotic cells respond to stress by altering the expression or activity of these tRNA-modifying enzymes, which leads to changes in the modification status of tRNAs. This review summarizes recent findings about these enzymes and sets them within the previous data context.
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Affiliation(s)
- M Eugenia Armengod
- a Laboratory of RNA Modification and Mitochondrial Diseases ; Centro de Investigación Príncipe Felipe ; Valencia , Spain
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22
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Argonaute 2 Binds Directly to tRNA Genes and Promotes Gene Repression in cis. Mol Cell Biol 2015; 35:2278-94. [PMID: 25918241 DOI: 10.1128/mcb.00076-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To further our understanding of the RNAi machinery within the human nucleus, we analyzed the chromatin and RNA binding of Argonaute 2 (AGO2) within human cancer cell lines. Our data indicated that AGO2 binds directly to nascent tRNA and 5S rRNA, and to the genomic loci from which these RNAs are transcribed, in a small RNA- and DICER-independent manner. AGO2 chromatin binding was not observed at non-TFIIIC-dependent RNA polymerase III (Pol III) genes or at extra-TFIIIC (ETC) sites, indicating that the interaction is specific for TFIIIC-dependent Pol III genes. A genome-wide analysis indicated that loss of AGO2 caused a global increase in mRNA expression level among genes that flank AGO2-bound tRNA genes. This effect was shown to be distinct from that of the disruption of DICER, DROSHA, or CTCF. We propose that AGO2 binding to tRNA genes has a novel and important regulatory role in human cells.
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23
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Han L, Kon Y, Phizicky EM. Functional importance of Ψ38 and Ψ39 in distinct tRNAs, amplified for tRNAGln(UUG) by unexpected temperature sensitivity of the s2U modification in yeast. RNA (NEW YORK, N.Y.) 2015; 21:188-201. [PMID: 25505024 PMCID: PMC4338347 DOI: 10.1261/rna.048173.114] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The numerous modifications of tRNA play central roles in controlling tRNA structure and translation. Modifications in and around the anticodon loop often have critical roles in decoding mRNA and in maintaining its reading frame. Residues U38 and U39 in the anticodon stem-loop are frequently modified to pseudouridine (Ψ) by members of the widely conserved TruA/Pus3 family of pseudouridylases. We investigate here the cause of the temperature sensitivity of pus3Δ mutants of the yeast Saccharomyces cerevisiae and find that, although Ψ38 or Ψ39 is found on at least 19 characterized cytoplasmic tRNA species, the temperature sensitivity is primarily due to poor function of tRNA(Gln(UUG)), which normally has Ψ38. Further investigation reveals that at elevated temperatures there are substantially reduced levels of the s(2)U moiety of mcm(5)s(2)U34 of tRNA(Gln(UUG)) and the other two cytoplasmic species with mcm(5)s(2)U34, that the reduced s(2)U levels occur in the parent strain BY4741 and in the widely used strain W303, and that reduced levels of the s(2)U moiety are detectable in BY4741 at temperatures as low as 33°C. Additional examination of the role of Ψ38,39 provides evidence that Ψ38 is important for function of tRNA(Gln(UUG)) at permissive temperature, and indicates that Ψ39 is important for the function of tRNA(Trp(CCA)) in trm10Δ pus3Δ mutants and of tRNA(Leu(CAA)) as a UAG nonsense suppressor. These results provide evidence for important roles of both Ψ38 and Ψ39 in specific tRNAs, and establish that modification of the wobble position is subject to change under relatively mild growth conditions.
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Affiliation(s)
- Lu Han
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York 14642, USA
| | - Yoshiko Kon
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York 14642, USA
| | - Eric M Phizicky
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York 14642, USA
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24
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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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25
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Meseguer S, Martínez-Zamora A, García-Arumí E, Andreu AL, Armengod ME. The ROS-sensitive microRNA-9/9* controls the expression of mitochondrial tRNA-modifying enzymes and is involved in the molecular mechanism of MELAS syndrome. Hum Mol Genet 2014; 24:167-84. [PMID: 25149473 DOI: 10.1093/hmg/ddu427] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Mitochondrial dysfunction activates mitochondria-to-nucleus signaling pathways whose components are mostly unknown. Identification of these components is important to understand the molecular mechanisms underlying mitochondrial diseases and to discover putative therapeutic targets. MELAS syndrome is a rare neurodegenerative disease caused by mutations in mitochondrial (mt) DNA affecting mt-tRNA(Leu(UUR)). Patient and cybrid cells exhibit elevated oxidative stress. Moreover, mutant mt-tRNAs(Leu(UUR)) lack the taurine-containing modification normally present at the wobble uridine (U34) of wild-type mt-tRNA(Leu(UUR)), which is considered an etiology of MELAS. However, the molecular mechanism is still unclear. We found that MELAS cybrids exhibit a significant decrease in the steady-state levels of several mt-tRNA-modification enzymes, which is not due to transcriptional regulation. We demonstrated that oxidative stress mediates an NFkB-dependent induction of microRNA-9/9*, which acts as a post-transcriptional negative regulator of the mt-tRNA-modification enzymes GTPBP3, MTO1 and TRMU. Down-regulation of these enzymes by microRNA-9/9* affects the U34 modification status of non-mutant tRNAs and contributes to the MELAS phenotype. Anti-microRNA-9 treatments of MELAS cybrids reverse the phenotype, whereas miR-9 transfection of wild-type cells mimics the effects of siRNA-mediated down-regulation of GTPBP3, MTO1 and TRMU. Our data represent the first evidence that an mt-DNA disease can directly affect microRNA expression. Moreover, we demonstrate that the modification status of mt-tRNAs is dynamic and that cells respond to stress by modulating the expression of mt-tRNA-modifying enzymes. microRNA-9/9* is a crucial player in mitochondria-to-nucleus signaling as it regulates expression of nuclear genes in response to changes in the functional state of mitochondria.
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Affiliation(s)
- Salvador Meseguer
- Laboratory of RNA Modification and Mitochondrial Diseases, Centro de Investigación Príncipe Felipe, Valencia 46012, Spain
| | - Ana Martínez-Zamora
- Laboratory of RNA Modification and Mitochondrial Diseases, Centro de Investigación Príncipe Felipe, Valencia 46012, Spain
| | - Elena García-Arumí
- Hospital Universitari Vall d'Hebron, Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona 08035, Spain Biomedical Research Networking Centre for Rare Diseases (CIBERER) (node U701), Barcelona, Spain and
| | - Antonio L Andreu
- Hospital Universitari Vall d'Hebron, Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona 08035, Spain Biomedical Research Networking Centre for Rare Diseases (CIBERER) (node U701), Barcelona, Spain and
| | - M-Eugenia Armengod
- Laboratory of RNA Modification and Mitochondrial Diseases, Centro de Investigación Príncipe Felipe, Valencia 46012, Spain CIBERER (node U721), Valencia, Spain
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26
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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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Pai DA, Kaplan CD, Kweon HK, Murakami K, Andrews PC, Engelke DR. RNAs nonspecifically inhibit RNA polymerase II by preventing binding to the DNA template. RNA (NEW YORK, N.Y.) 2014; 20:644-655. [PMID: 24614752 PMCID: PMC3988566 DOI: 10.1261/rna.040444.113] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Accepted: 01/22/2014] [Indexed: 06/03/2023]
Abstract
Many RNAs are known to act as regulators of transcription in eukaryotes, including certain small RNAs that directly inhibit RNA polymerases both in prokaryotes and eukaryotes. We have examined the potential for a variety of RNAs to directly inhibit transcription by yeast RNA polymerase II (Pol II) and find that unstructured RNAs are potent inhibitors of purified yeast Pol II. Inhibition by RNA is achieved by blocking binding of the DNA template and requires binding of the RNA to Pol II prior to open complex formation. RNA is not able to displace a DNA template that is already stably bound to Pol II, nor can RNA inhibit elongating Pol II. Unstructured RNAs are more potent inhibitors than highly structured RNAs and can also block specific transcription initiation in the presence of basal transcription factors. Crosslinking studies with ultraviolet light show that unstructured RNA is most closely associated with the two large subunits of Pol II that comprise the template binding cleft, but the RNA has contacts in a basic residue channel behind the back wall of the active site. These results are distinct from previous observations of specific inhibition by small, structured RNAs in that they demonstrate a sensitivity of the holoenzyme to inhibition by unstructured RNA products that bind to a surface outside the DNA cleft. These results are discussed in terms of the need to prevent inhibition by RNAs, either though sequestration of nascent RNA or preemptive interaction of Pol II with the DNA template.
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Affiliation(s)
- Dave A. Pai
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Craig D. Kaplan
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA
| | - Hye Kyong Kweon
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Kenji Murakami
- Department of Structural Biology, Stanford University, Stanford, California 94305, USA
| | - Philip C. Andrews
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - David R. Engelke
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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