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Sele C, Krupinska E, Andersson Rasmussen A, Ekström S, Hultgren L, Lou J, Kozielski F, Fisher SZ, Knecht W. New insights into complex formation by SARS-CoV-2 nsp10 and nsp14. Nucleosides Nucleotides Nucleic Acids 2024:1-15. [PMID: 38422227 DOI: 10.1080/15257770.2024.2321600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 02/05/2024] [Indexed: 03/02/2024]
Abstract
SARS-CoV-2 non-structural protein 10 (nsp10) is essential for the stimulation of enzymatic activities of nsp14 and nsp16, acting as both an activator and scaffolding protein. Nsp14 is a bifunctional enzyme with the N-terminus containing a 3'-5' exoribonuclease (ExoN) domain that allows the excision of nucleotide mismatches at the virus RNA 3'-end, and a C-terminal N7-methyltransferase (N7-MTase) domain. Nsp10 is required for stimulating both ExoN proofreading and the nsp16 2'-O-methyltransferase activities. This makes nsp10 a central player in both viral resistance to nucleoside-based drugs and the RNA cap methylation machinery that helps the virus evade innate immunity. We characterised the interactions between full-length nsp10 (139 residues), N- and C-termini truncated nsp10 (residues 10-133), and nsp10 with a C-terminal truncation (residues 1-133) with nsp14 using microscale thermophoresis, multi-detection SEC, and hydrogen-deuterium (H/D) exchange mass spectrometry. We describe the functional role of the C-terminal region of nsp10 for binding to nsp14 and show that full N- and C-termini of nsp10 are important for optimal binding. In addition, our H/D exchange experiments suggest an intermediary interaction of nsp10 with the N7-MTase domain of nsp14. In summary, our results suggest intermediary steps in the process of association or dissociation of the nsp10-nsp14 complex, involving contacts between the two proteins in regions not identifiable by X-ray crystallography alone.
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Affiliation(s)
- Céleste Sele
- Department of Biology & Lund Protein Production Platform & Protein Production Sweden, Lund University, Lund, Sweden
| | - Ewa Krupinska
- Department of Biology & Lund Protein Production Platform & Protein Production Sweden, Lund University, Lund, Sweden
| | - Anna Andersson Rasmussen
- Department of Biology & Lund Protein Production Platform & Protein Production Sweden, Lund University, Lund, Sweden
| | - Simon Ekström
- Swedish National Infrastructure for Biological Mass Spectrometry and SciLifeLab, Integrated Structural Biology platform, Structural Proteomics Unit Sweden, Lund University, Lund, Sweden
| | - Lucas Hultgren
- Swedish National Infrastructure for Biological Mass Spectrometry and SciLifeLab, Integrated Structural Biology platform, Structural Proteomics Unit Sweden, Lund University, Lund, Sweden
| | - Jiaqi Lou
- School of Pharmacy, University College London, London, UK
| | | | - S Zoë Fisher
- Department of Biology & Lund Protein Production Platform & Protein Production Sweden, Lund University, Lund, Sweden
- European Spallation Source ERIC, Lund, Sweden
| | - Wolfgang Knecht
- Department of Biology & Lund Protein Production Platform & Protein Production Sweden, Lund University, Lund, Sweden
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2
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Krempl C, Lazzaretti D, Sprangers R. A structural biology view on the enzymes involved in eukaryotic mRNA turnover. Biol Chem 2023; 404:1101-1121. [PMID: 37709756 DOI: 10.1515/hsz-2023-0182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 08/24/2023] [Indexed: 09/16/2023]
Abstract
The cellular environment contains numerous ribonucleases that are dedicated to process mRNA transcripts that have been targeted for degradation. Here, we review the three dimensional structures of the ribonuclease complexes (Pan2-Pan3, Ccr4-Not, Xrn1, exosome) and the mRNA decapping enzymes (Dcp2, DcpS) that are involved in mRNA turnover. Structures of major parts of these proteins have been experimentally determined. These enzymes and factors do not act in isolation, but are embedded in interaction networks which regulate enzyme activity and ensure that the appropriate substrates are recruited. The structural details of the higher order complexes that form can, in part, be accurately deduced from known structural data of sub-complexes. Interestingly, many of the ribonuclease and decapping enzymes have been observed in structurally different conformations. Together with experimental data, this highlights that structural changes are often important for enzyme function. We conclude that the known structural data of mRNA decay factors provide important functional insights, but that static structural data needs to be complemented with information regarding protein motions to complete the picture of how transcripts are turned over. In addition, we highlight multiple aspects that influence mRNA turnover rates, but that have not been structurally characterized so far.
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Affiliation(s)
- Christina Krempl
- Institute of Biophysics and Physical Biochemistry, Regensburg Center for Biochemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Daniela Lazzaretti
- Institute of Biophysics and Physical Biochemistry, Regensburg Center for Biochemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Remco Sprangers
- Institute of Biophysics and Physical Biochemistry, Regensburg Center for Biochemistry, University of Regensburg, D-93053 Regensburg, Germany
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3
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Orlovetskie N, Mani D, Rouvinski A, Jarrous N. Human RNase P exhibits and controls distinct ribonucleolytic activities required for ordered maturation of tRNA. Proc Natl Acad Sci U S A 2023; 120:e2307185120. [PMID: 37831743 PMCID: PMC10589621 DOI: 10.1073/pnas.2307185120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Accepted: 09/05/2023] [Indexed: 10/15/2023] Open
Abstract
Precursor tRNAs are transcribed with flanking and intervening sequences known to be processed by specific ribonucleases. Here, we show that transcription complexes of RNA polymerase III assembled on tRNA genes comprise RNase P that cleaves precursor tRNA and subsequently degrades the excised 5' leader. Degradation is based on a 3'-5' exoribonucleolytic activity carried out by the protein subunit Rpp14, as determined by biochemical and reverse genetic analyses. Neither reconstituted nor purified RNase P displays this magnesium ion-dependent, processive exoribonucleolytic activity. Markedly, knockdown of Rpp14 by RNA interference leads to a wide-ranging inhibition of cleavage of flanking and intervening sequences of various precursor tRNAs in extracts and cells. This study reveals that RNase P controls tRNA splicing complex and RNase Z for ordered maturation of nascent precursor tRNAs by transcription complexes.
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Affiliation(s)
- Natalie Orlovetskie
- Department of Microbiology and Molecular Genetics, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem9112010, Israel
| | - Dhivakar Mani
- Department of Microbiology and Molecular Genetics, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem9112010, Israel
| | - Alexander Rouvinski
- Department of Microbiology and Molecular Genetics, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem9112010, Israel
- The Kuvin Center for the Study of Infectious and Tropical Diseases, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem9112010, Israel
| | - Nayef Jarrous
- Department of Microbiology and Molecular Genetics, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem9112010, Israel
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4
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Guo L, Salian S, Xue JY, Rath N, Rousseau J, Kim H, Ehresmann S, Moosa S, Nakagawa N, Kuroda H, Clayton-Smith J, Wang J, Wang Z, Banka S, Jackson A, Zhang YM, Wei ZJ, Hüning I, Brunet T, Ohashi H, Thomas MF, Bupp C, Miyake N, Matsumoto N, Mendoza-Londono R, Costain G, Hahn G, Di Donato N, Yigit G, Yamada T, Nishimura G, Ansel KM, Wollnik B, Hrabě de Angelis M, Mégarbané A, Rosenfeld JA, Heissmeyer V, Ikegawa S, Campeau PM. Null and missense mutations of ERI1 cause a recessive phenotypic dichotomy in humans. Am J Hum Genet 2023; 110:1068-1085. [PMID: 37352860 PMCID: PMC10357479 DOI: 10.1016/j.ajhg.2023.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 05/31/2023] [Accepted: 06/01/2023] [Indexed: 06/25/2023] Open
Abstract
ERI1 is a 3'-to-5' exoribonuclease involved in RNA metabolic pathways including 5.8S rRNA processing and turnover of histone mRNAs. Its biological and medical significance remain unclear. Here, we uncover a phenotypic dichotomy associated with bi-allelic ERI1 variants by reporting eight affected individuals from seven unrelated families. A severe spondyloepimetaphyseal dysplasia (SEMD) was identified in five affected individuals with missense variants but not in those with bi-allelic null variants, who showed mild intellectual disability and digital anomalies. The ERI1 missense variants cause a loss of the exoribonuclease activity, leading to defective trimming of the 5.8S rRNA 3' end and a decreased degradation of replication-dependent histone mRNAs. Affected-individual-derived induced pluripotent stem cells (iPSCs) showed impaired in vitro chondrogenesis with downregulation of genes regulating skeletal patterning. Our study establishes an entity previously unreported in OMIM and provides a model showing a more severe effect of missense alleles than null alleles within recessive genotypes, suggesting a key role of ERI1-mediated RNA metabolism in human skeletal patterning and chondrogenesis.
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Affiliation(s)
- Long Guo
- Department of Laboratory Animal Science, School of Basic Medical Sciences, Xi'an Jiaotong University, Xi'an 710061, China; National Local Joint Engineering Research Center for Precision Surgery & Regenerative Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, China; Center of Medical Genetics, Northwest Women's and Children's Hospital, the Affiliated Northwest Women's and Children's Hospital of Xi'an Jiaotong University Health Science Center, Xi'an 710003, China.
| | - Smrithi Salian
- Department of Pediatrics, CHU Sainte Justine Research Center, University of Montreal, 3175 Cote-Sainte-Catherine, Montreal, QC H3T 1C5, Canada
| | - Jing-Yi Xue
- Department of Laboratory Animal Science, School of Basic Medical Sciences, Xi'an Jiaotong University, Xi'an 710061, China; Laboratory for Bone and Joint Diseases, RIKEN Center for Integrative Medical Sciences, Tokyo 108-8639, Japan
| | - Nicola Rath
- Research Unit Molecular Immune Regulation, Helmholtz Zentrum München, German Research Center for Environmental Health, D-81377 Munich, Germany
| | - Justine Rousseau
- Department of Pediatrics, CHU Sainte Justine Research Center, University of Montreal, 3175 Cote-Sainte-Catherine, Montreal, QC H3T 1C5, Canada
| | - Hyunyun Kim
- Department of Pediatrics, CHU Sainte Justine Research Center, University of Montreal, 3175 Cote-Sainte-Catherine, Montreal, QC H3T 1C5, Canada
| | - Sophie Ehresmann
- Molecular Biology Program, Université de Montréal, Montréal, QC H3T 1J4, Canada
| | - Shahida Moosa
- Division of Molecular Biology and Human Genetics, Stellenbosch University and Medical Genetics, Tygerberg Hospital, Tygerberg 7505, South Africa
| | - Norio Nakagawa
- Department of Pediatrics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan; Department of Pediatrics, North Medical Center, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Hiroshi Kuroda
- Department of Pediatrics, Kyoto City Hospital, Kyoto 604-8845, Japan
| | - Jill Clayton-Smith
- Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University Foundation NHS Trust, Health Innovation Manchester, M13 9WL Manchester, UK; Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, M13 9PL Manchester, UK
| | - Juan Wang
- Department of Ultrasound, the Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710004, China
| | - Zheng Wang
- Laboratory for Bone and Joint Diseases, RIKEN Center for Integrative Medical Sciences, Tokyo 108-8639, Japan
| | - Siddharth Banka
- Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University Foundation NHS Trust, Health Innovation Manchester, M13 9WL Manchester, UK; Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, M13 9PL Manchester, UK
| | - Adam Jackson
- Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University Foundation NHS Trust, Health Innovation Manchester, M13 9WL Manchester, UK; Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, M13 9PL Manchester, UK
| | - Yan-Min Zhang
- Shaanxi Institute for Pediatric Diseases, Xi'an Children's Hospital, Affiliated Children's Hospital of Xi'an Jiaotong University, Xi'an 710082, China
| | - Zhen-Jie Wei
- Laboratory for Bone and Joint Diseases, RIKEN Center for Integrative Medical Sciences, Tokyo 108-8639, Japan
| | - Irina Hüning
- Institute of Human Genetics, University of Lübeck, 23538 Lübeck, Germany
| | - Theresa Brunet
- Institute of Human Genetics, School of Medicine, Technical University Munich, 80333 Munich, Germany; Department of Paediatric Neurology and Developmental Medicine, Hauner Children's Hospital, Ludwig Maximilian University of Munich, 80539 Munich, Germany
| | - Hirofumi Ohashi
- Division of Medical Genetics, Saitama Children's Hospital, Saitama 330-8777, Japan
| | - Molly F Thomas
- Division of Gastroenterology, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Caleb Bupp
- Spectrum Health, Grand Rapids, MI 49503, USA
| | - Noriko Miyake
- Department of Human Genetics, Research Institute, National Center for Global Health and Medicine, Tokyo 162-8655, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Roberto Mendoza-Londono
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Program in Genetics and Genome Biology, SickKids Research Institute, and Department of Paediatrics, University of Toronto, Toronto, ON M5G 1X8, Canada
| | - Gregory Costain
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A4, Canada
| | - Gabriele Hahn
- Institute for Radiological Diagnostics, Universitätsklinikum Carl Gustav Carus Dresden, Technische Universität, 01307 Dresden, Germany
| | - Nataliya Di Donato
- Institute for Clinical Genetics, University Hospital, TU Dresden, 01069 Dresden, Germany
| | - Gökhan Yigit
- Institute of Human Genetics, University Medical Center Göttingen, 37075 Göttingen, Germany; DZHK (German Center for Cardiovascular Research), partner site Göttingen, 37075 Göttingen, Germany
| | - Takahiro Yamada
- Department of Medical Ethics and Medical Genetics, Kyoto University School of Public Health, Kyoto 606-8501, Japan
| | - Gen Nishimura
- Laboratory for Bone and Joint Diseases, RIKEN Center for Integrative Medical Sciences, Tokyo 108-8639, Japan
| | - K Mark Ansel
- Department of Microbiology and Immunology, University of California San Francisco, San Francisco, CA 94143, USA
| | - Bernd Wollnik
- Institute of Human Genetics, University Medical Center Göttingen, 37075 Göttingen, Germany; DZHK (German Center for Cardiovascular Research), partner site Göttingen, 37075 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37075 Göttingen, Germany
| | - Martin Hrabě de Angelis
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; Chair of Experimental Genetics, TUM School of Life Sciences, Technische Universität München, 85354 Freising, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - André Mégarbané
- Department of Human Genetics, Gilbert and Rose-Marie Chagoury School of Medicine, Lebanese American University, 1102-2801, Lebanon and Institut Jerome Lejeune, 75015 Paris, France
| | - Jill A Rosenfeld
- Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Baylor Genetics Laboratories, Houston, TX 77021, USA
| | - Vigo Heissmeyer
- Research Unit Molecular Immune Regulation, Helmholtz Zentrum München, German Research Center for Environmental Health, D-81377 Munich, Germany; Institute for Immunology, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität in Munich, 82152 Planegg-Martinsried, Germany
| | - Shiro Ikegawa
- Laboratory for Bone and Joint Diseases, RIKEN Center for Integrative Medical Sciences, Tokyo 108-8639, Japan
| | - Philippe M Campeau
- Department of Pediatrics, CHU Sainte Justine Research Center, University of Montreal, 3175 Cote-Sainte-Catherine, Montreal, QC H3T 1C5, Canada.
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5
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Yin X, Popa H, Stapon A, Bouda E, Garcia-Diaz M. Fidelity of Ribonucleotide Incorporation by the SARS-CoV-2 Replication Complex. J Mol Biol 2023; 435:167973. [PMID: 36690070 DOI: 10.1016/j.jmb.2023.167973] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 01/16/2023] [Accepted: 01/17/2023] [Indexed: 01/21/2023]
Abstract
The SARS-CoV-2 coronavirus has caused a global pandemic. Despite the initial success of vaccines at preventing infection, genomic variation has led to the proliferation of variants capable of higher infectivity. Mutations in the SARS-CoV-2 genome are the consequence of replication errors, highlighting the importance of understanding the determinants of SARS-CoV-2 replication fidelity. The RNA-dependent RNA polymerase (RdRp) is the central catalytic subunit for SARS-CoV-2 RNA replication and genome transcription. Here, we report the fidelity of ribonucleotide incorporation by SARS-CoV-2 RdRp (nsp12), along with its co-factors nsp7/nsp8, using steady-state kinetic analysis. Our analysis suggests that in the absence of the proofreading subunit (nsp14), the nsp12/7/8 complex has a surprisingly low base substitution fidelity (10-1-10-3). This is orders of magnitude lower than the fidelity reported for other coronaviruses (10-6-10-7), highlighting the importance of proofreading for faithful SARS-CoV-2 replication. We performed a mutational analysis of all reported SARS-CoV-2 genomes and identified mutations in both nsp12 and nsp14 that appear likely to lower viral replication fidelity through mechanisms that include impairing the nsp14 exonuclease activity or its association with the RdRp. Our observations provide novel insight into the mechanistic basis of replication fidelity in SARS-CoV-2 and the potential effect of nsp12 and nsp14 mutations on replication fidelity, informing the development of future antiviral agents and SARS-CoV-2 vaccines.
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6
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Cartalas J, Coudray L, Gobert A. How RNases Shape Mitochondrial Transcriptomes. Int J Mol Sci 2022; 23:6141. [PMID: 35682820 DOI: 10.3390/ijms23116141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 11/17/2022] Open
Abstract
Mitochondria are the power houses of eukaryote cells. These endosymbiotic organelles of prokaryote origin are considered as semi-autonomous since they have retained a genome and fully functional gene expression mechanisms. These pathways are particularly interesting because they combine features inherited from the bacterial ancestor of mitochondria with characteristics that appeared during eukaryote evolution. RNA biology is thus particularly diverse in mitochondria. It involves an unexpectedly vast array of factors, some of which being universal to all mitochondria and others being specific from specific eukaryote clades. Among them, ribonucleases are particularly prominent. They play pivotal functions such as the maturation of transcript ends, RNA degradation and surveillance functions that are required to attain the pool of mature RNAs required to synthesize essential mitochondrial proteins such as respiratory chain proteins. Beyond these functions, mitochondrial ribonucleases are also involved in the maintenance and replication of mitochondrial DNA, and even possibly in the biogenesis of mitochondrial ribosomes. The diversity of mitochondrial RNases is reviewed here, showing for instance how in some cases a bacterial-type enzyme was kept in some eukaryotes, while in other clades, eukaryote specific enzymes were recruited for the same function.
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Łabędzka-Dmoch K, Rażew M, Gapińska M, Piątkowski J, Kolondra A, Salmonowicz H, Wenda JM, Nowotny M, Golik P. The Pet127 protein is a mitochondrial 5'-to-3' exoribonuclease from the PD-(D/E)XK superfamily involved in RNA maturation and intron degradation in yeasts. RNA 2022; 28:711-728. [PMID: 35197365 PMCID: PMC9014873 DOI: 10.1261/rna.079083.121] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 01/31/2022] [Indexed: 06/01/2023]
Abstract
Pet127 is a mitochondrial protein found in multiple eukaryotic lineages, but absent from several taxa, including plants and animals. Distant homology suggests that it belongs to the divergent PD-(D/E)XK superfamily which includes various nucleases and related proteins. Earlier yeast genetics experiments suggest that it plays a nonessential role in RNA degradation and 5' end processing. Our phylogenetic analysis suggests that it is a primordial eukaryotic invention that was retained in diverse groups, and independently lost several times in the evolution of other organisms. We demonstrate for the first time that the fungal Pet127 protein in vitro is a processive 5'-to-3' exoribonuclease capable of digesting various substrates in a sequence nonspecific manner. Mutations in conserved residues essential in the PD-(D/E)XK superfamily active site abolish the activity of Pet127. Deletion of the PET127 gene in the pathogenic yeast Candida albicans results in a moderate increase in the steady-state levels of several transcripts and in accumulation of unspliced precursors and intronic sequences of three introns. Mutations in the active site residues result in a phenotype identical to that of the deletant, confirming that the exoribonuclease activity is related to the physiological role of the Pet127 protein. Pet127 activity is, however, not essential for maintaining the mitochondrial respiratory activity in C. albicans.
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Affiliation(s)
- Karolina Łabędzka-Dmoch
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw 02-106, Poland
| | - Michal Rażew
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Marta Gapińska
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Jakub Piątkowski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw 02-106, Poland
| | - Adam Kolondra
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw 02-106, Poland
| | - Hanna Salmonowicz
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw 02-106, Poland
- Laboratory of Metabolic Quality Control, IMOL, Polish Academy of Sciences, Warsaw 00-783, Poland
| | - Joanna M Wenda
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw 02-106, Poland
| | - Marcin Nowotny
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Paweł Golik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw 02-106, Poland
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw 02-106, Poland
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8
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Moeller NH, Shi K, Demir Ö, Belica C, Banerjee S, Yin L, Durfee C, Amaro RE, Aihara H. Structure and dynamics of SARS-CoV-2 proofreading exoribonuclease ExoN. Proc Natl Acad Sci U S A 2022; 119. [PMID: 35165203 DOI: 10.1073/pnas.2106379119] [Citation(s) in RCA: 64] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/11/2022] [Indexed: 12/13/2022] Open
Abstract
High-fidelity replication of the large RNA genome of coronaviruses (CoVs) is mediated by a 3'-to-5' exoribonuclease (ExoN) in nonstructural protein 14 (nsp14), which excises nucleotides including antiviral drugs misincorporated by the low-fidelity viral RNA-dependent RNA polymerase (RdRp) and has also been implicated in viral RNA recombination and resistance to innate immunity. Here, we determined a 1.6-Å resolution crystal structure of severe acute respiratory syndrome CoV 2 (SARS-CoV-2) ExoN in complex with its essential cofactor, nsp10. The structure shows a highly basic and concave surface flanking the active site, comprising several Lys residues of nsp14 and the N-terminal amino group of nsp10. Modeling suggests that this basic patch binds to the template strand of double-stranded RNA substrates to position the 3' end of the nascent strand in the ExoN active site, which is corroborated by mutational and computational analyses. We also show that the ExoN activity can rescue a stalled RNA primer poisoned with sofosbuvir and allow RdRp to continue its extension in the presence of the chain-terminating drug, biochemically recapitulating proofreading in SARS-CoV-2 replication. Molecular dynamics simulations further show remarkable flexibility of multidomain nsp14 and suggest that nsp10 stabilizes ExoN for substrate RNA binding to support its exonuclease activity. Our high-resolution structure of the SARS-CoV-2 ExoN-nsp10 complex serves as a platform for future development of anticoronaviral drugs or strategies to attenuate the viral virulence.
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Falchi FA, Pizzoccheri R, Briani F. Activity and Function in Human Cells of the Evolutionary Conserved Exonuclease Polynucleotide Phosphorylase. Int J Mol Sci 2022; 23:ijms23031652. [PMID: 35163574 PMCID: PMC8836086 DOI: 10.3390/ijms23031652] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 01/28/2022] [Accepted: 01/28/2022] [Indexed: 02/04/2023] Open
Abstract
Polynucleotide phosphorylase (PNPase) is a phosphorolytic RNA exonuclease highly conserved throughout evolution. Human PNPase (hPNPase) is located in mitochondria and is essential for mitochondrial function and homeostasis. Not surprisingly, mutations in the PNPT1 gene, encoding hPNPase, cause serious diseases. hPNPase has been implicated in a plethora of processes taking place in different cell compartments and involving other proteins, some of which physically interact with hPNPase. This paper reviews hPNPase RNA binding and catalytic activity in relation with the protein structure and in comparison, with the activity of bacterial PNPases. The functions ascribed to hPNPase in different cell compartments are discussed, highlighting the gaps that still need to be filled to understand the physiological role of this ancient protein in human cells.
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10
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Riccio AA, Sullivan ED, Copeland WC. Activation of the SARS-CoV-2 NSP14 3'-5' exoribonuclease by NSP10 and response to antiviral inhibitors. J Biol Chem 2021; 298:101518. [PMID: 34942146 PMCID: PMC8685350 DOI: 10.1016/j.jbc.2021.101518] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 12/15/2021] [Accepted: 12/17/2021] [Indexed: 12/22/2022] Open
Abstract
Understanding the core replication complex of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential to the development of novel coronavirus-specific antiviral therapeutics. Among the proteins required for faithful replication of the SARS-CoV-2 genome are nonstructural protein 14 (NSP14), a bifunctional enzyme with an N-terminal 3′-to-5′ exoribonuclease (ExoN) and a C-terminal N7-methyltransferase, and its accessory protein, NSP10. The difficulty in producing pure and high quantities of the NSP10/14 complex has hampered the biochemical and structural study of these important proteins. We developed a straightforward protocol for the expression and purification of both NSP10 and NSP14 from Escherichia coli and for the in vitro assembly and purification of a stoichiometric NSP10/14 complex with high yields. Using these methods, we observe that NSP10 provides a 260-fold increase in kcat/Km in the exoribonucleolytic activity of NSP14 and enhances protein stability. We also probed the effect of two small molecules on NSP10/14 activity, remdesivir monophosphate and the methyltransferase inhibitor S-adenosylhomocysteine. Our analysis highlights two important factors for drug development: first, unlike other exonucleases, the monophosphate nucleoside analog intermediate of remdesivir does not inhibit NSP14 activity; and second, S-adenosylhomocysteine modestly activates NSP14 exonuclease activity. In total, our analysis provides insights for future structure–function studies of SARS-CoV-2 replication fidelity for the treatment of coronavirus disease 2019.
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Affiliation(s)
- Amanda A Riccio
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709
| | - Eric D Sullivan
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709.
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11
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Łabędzka-Dmoch K, Kolondra A, Karpińska MA, Dębek S, Grochowska J, Grochowski M, Piątkowski J, Hoang Diu Bui T, Golik P. Pervasive transcription of the mitochondrial genome in Candida albicans is revealed in mutants lacking the mtEXO RNase complex. RNA Biol 2021; 18:303-317. [PMID: 34229573 PMCID: PMC8677008 DOI: 10.1080/15476286.2021.1943929] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The mitochondrial genome of the pathogenic yeast Candida albicans displays a typical organization of several (eight) primary transcription units separated by noncoding regions. Presence of genes encoding Complex I subunits and the stability of its mtDNA sequence make it an attractive model to study organellar genome expression using transcriptomic approaches. The main activity responsible for RNA degradation in mitochondria is a two-component complex (mtEXO) consisting of a 3ʹ-5ʹ exoribonuclease, in yeasts encoded by the DSS1 gene, and a conserved Suv3p helicase. In C. albicans, deletion of either DSS1 or SUV3 gene results in multiple defects in mitochondrial genome expression leading to the loss of respiratory competence. Transcriptomic analysis reveals pervasive transcription in mutants lacking the mtEXO activity, with evidence of the entire genome being transcribed, whereas in wild-type strains no RNAs corresponding to a significant fraction of the noncoding genome can be detected. Antisense (‘mirror’) transcripts, absent from normal mitochondria are also prominent in the mutants. The expression of multiple mature transcripts, particularly those translated from bicistronic mRNAs, as well as those that contain introns is affected in the mutants, resulting in a decreased level of proteins and reduced respiratory complex activity. The phenotype is most severe in the case of Complex IV, where a decrease of mature COX1 mRNA level to ~5% results in a complete loss of activity. These results show that RNA degradation by mtEXO is essential for shaping the mitochondrial transcriptome and is required to maintain the functional demarcation between transcription units and non-coding genome segments.
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Affiliation(s)
- Karolina Łabędzka-Dmoch
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Adam Kolondra
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Magdalena A Karpińska
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Sonia Dębek
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Joanna Grochowska
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.,Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Maciej Grochowski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Jakub Piątkowski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Thi Hoang Diu Bui
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Paweł Golik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.,Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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12
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Chen J, To L, de Mets F, Luo X, Majdalani N, Tai CH, Gottesman S. A fluorescence-based genetic screen reveals diverse mechanisms silencing small RNA signaling in E. coli. Proc Natl Acad Sci U S A 2021; 118:e2106964118. [PMID: 34210798 DOI: 10.1073/pnas.2106964118] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
As key players of gene regulation in many bacteria, small regulatory RNAs (sRNAs) associated with the RNA chaperone Hfq shape numerous phenotypic traits, including metabolism, stress response and adaptation, as well as virulence. sRNAs can alter target messenger RNA (mRNA) translation and stability via base pairing. sRNA synthesis is generally under tight transcriptional regulation, but other levels of regulation of sRNA signaling are less well understood. Here we used a fluorescence-based functional screen to identify regulators that can quench sRNA signaling of the iron-responsive sRNA RyhB in Escherichia coli The identified regulators fell into two classes, general regulators (affecting signaling by many sRNAs) and RyhB-specific regulators; we focused on the specific ones here. General regulators include three Hfq-interacting sRNAs, CyaR, ChiX, and McaS, previously found to act through Hfq competition, RNase T, a 3' to 5' exonuclease not previously implicated in sRNA degradation, and YhbS, a putative GCN5-related N-acetyltransferase (GNAT). Two specific regulators were identified. AspX, a 3'end-derived small RNA, specifically represses RyhB signaling via an RNA sponging mechanism. YicC, a previously uncharacterized but widely conserved protein, triggers rapid RyhB degradation via collaboration with the exoribonuclease PNPase. These findings greatly expand our knowledge of regulation of bacterial sRNA signaling and suggest complex regulatory networks for controlling iron homeostasis in bacteria. The fluorescence-based genetic screen system described here is a powerful tool expected to accelerate the discovery of novel regulators of sRNA signaling in many bacteria.
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13
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Tahir M. Coronavirus genomic nsp14-ExoN, structure, role, mechanism, and potential application as a drug target. J Med Virol 2021; 93:4258-4264. [PMID: 33837972 PMCID: PMC8250946 DOI: 10.1002/jmv.27009] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Revised: 04/07/2021] [Accepted: 04/08/2021] [Indexed: 12/20/2022]
Abstract
The recent coronavirus disease 2019 (COVID-19), causing a global pandemic with devastating effects on healthcare and social-economic systems, has no special antiviral therapies available for human coronaviruses (CoVs). The severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) possesses a nonstructural protein (nsp14), with amino-terminal domain coding for proofreading exoribonuclease (ExoN) that is required for high-fidelity replication. The ability of CoVs during genome replication and transcription to proofread and exclude mismatched nucleotides has long hindered the development of anti-CoV drugs. The resistance of SARS-CoV-2 to antivirals, especially nucleoside analogs (NAs), shows the need to identify new CoV inhibition targets. Therefore, this review highlights the importance of nsp14-ExoN as a target for inhibition. Also, nucleoside analogs could be used in combination with existing anti-CoV therapeutics to target the proofreading mechanism.
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Affiliation(s)
- Mohammed Tahir
- Department of BiologyUniversity of SulaimaniSulaimanyahKurdistanIraq
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14
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Munaweera R, Hu YS. Computational Characterizations of the Interactions Between the Pontacyl Violet 6R and Exoribonuclease as a Potential Drug Target Against SARS-CoV-2. Front Chem 2021; 8:627340. [PMID: 33553109 PMCID: PMC7858249 DOI: 10.3389/fchem.2020.627340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 12/21/2020] [Indexed: 11/24/2022] Open
Abstract
We report a molecular-docking and virtual-screening-based identification and characterization of interactions of lead molecules with exoribonuclease (ExoN) enzyme in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). From previously identified DEDDh/DEEDh subfamily nuclease inhibitors, our results revealed strong binding of pontacyl violet 6R (PV6R) at the catalytic active site of ExoN. The binding was found to be stabilized via two hydrogen bonds and hydrophobic interactions. Molecular dynamics simulations further confirmed the stability of PV6R at the active site showing a shift in ligand to reach a more stabilized binding. Using PV6R as the lead molecule, we employed virtual screening to identify potential molecular candidates that form strong interactions at the ExoN active site. Our study paves ways for evaluating the ExoN as a novel drug target for antiviral treatment against SARS-CoV-2.
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Affiliation(s)
- Rangika Munaweera
- Department of Chemistry, College of Liberal Arts and Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Ying S Hu
- Department of Chemistry, College of Liberal Arts and Sciences, University of Illinois at Chicago, Chicago, IL, United States
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15
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Xie W, Sowemimo I, Hayashi R, Wang J, Burkard TR, Brennecke J, Ameres SL, Patel DJ. Structure-function analysis of microRNA 3'-end trimming by Nibbler. Proc Natl Acad Sci U S A 2020; 117:30370-30379. [PMID: 33199607 PMCID: PMC7720153 DOI: 10.1073/pnas.2018156117] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Nibbler (Nbr) is a 3'-to-5' exoribonuclease whose catalytic 3'-end trimming activity impacts microRNA (miRNA) and PIWI-interacting RNA (piRNA) biogenesis. Here, we report on structural and functional studies to decipher the contributions of Nbr's N-terminal domain (NTD) and exonucleolytic domain (EXO) in miRNA 3'-end trimming. We have solved the crystal structures of the NTD core and EXO domains of Nbr, both in the apo-state. The NTD-core domain of Aedes aegypti Nbr adopts a HEAT-like repeat scaffold with basic patches constituting an RNA-binding surface exhibiting a preference for binding double-strand RNA (dsRNA) over single-strand RNA (ssRNA). Structure-guided functional assays in Drosophila S2 cells confirmed a principal role of the NTD in exonucleolytic miRNA trimming, which depends on basic surface patches. Gain-of-function experiments revealed a potential role of the NTD in recruiting Nbr to Argonaute-bound small RNA substrates. The EXO domain of A. aegypti and Drosophila melanogaster Nbr adopt a mixed α/β-scaffold with a deep pocket lined by a DEDDy catalytic cleavage motif. We demonstrate that Nbr's EXO domain exhibits Mn2+-dependent ssRNA-specific 3'-to-5' exoribonuclease activity. Modeling of a 3' terminal Uridine into the catalytic pocket of Nbr EXO indicates that 2'-O-methylation of the 3'-U would result in a steric clash with a tryptophan side chain, suggesting that 2'-O-methylation protects small RNAs from Nbr-mediated trimming. Overall, our data establish that Nbr requires its NTD as a substrate recruitment platform to execute exonucleolytic miRNA maturation, catalyzed by the ribonuclease EXO domain.
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Affiliation(s)
- Wei Xie
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065
| | - Ivica Sowemimo
- Institute of Molecular Biotechnology, Vienna BioCenter, 1030 Vienna, Austria
| | - Rippei Hayashi
- Department of Genome Sciences, The John Curtin School of Medical Research, Australian National University, Canberra 2601, Australia
| | - Juncheng Wang
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065
| | - Thomas R Burkard
- Institute of Molecular Biotechnology, Vienna BioCenter, 1030 Vienna, Austria
| | - Julius Brennecke
- Institute of Molecular Biotechnology, Vienna BioCenter, 1030 Vienna, Austria;
| | - Stefan L Ameres
- Institute of Molecular Biotechnology, Vienna BioCenter, 1030 Vienna, Austria;
- Max Perutz Labs, University of Vienna, Vienna BioCenter, 1030 Vienna, Austria
| | - Dinshaw J Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065;
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16
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Abshire ET, Hughes KL, Diao R, Pearce S, Gopalakrishna S, Trievel RC, Rorbach J, Freddolino PL, Goldstrohm AC. Differential processing and localization of human Nocturnin controls metabolism of mRNA and nicotinamide adenine dinucleotide cofactors. J Biol Chem 2020; 295:15112-15133. [PMID: 32839274 PMCID: PMC7606674 DOI: 10.1074/jbc.ra120.012618] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 08/06/2020] [Indexed: 01/02/2023] Open
Abstract
Nocturnin (NOCT) is a eukaryotic enzyme that belongs to a superfamily of exoribonucleases, endonucleases, and phosphatases. In this study, we analyze the expression, processing, localization, and cellular functions of human NOCT. We find that NOCT protein is differentially expressed and processed in a cell and tissue type-specific manner to control its localization to the cytoplasm or mitochondrial exterior or interior. The N terminus of NOCT is necessary and sufficient to confer import and processing in the mitochondria. We measured the impact of cytoplasmic NOCT on the transcriptome and observed that it affects mRNA levels of hundreds of genes that are significantly enriched in osteoblast, neuronal, and mitochondrial functions. Recent biochemical data indicate that NOCT dephosphorylates NADP(H) metabolites, and thus we measured the effect of NOCT on these cofactors in cells. We find that NOCT increases NAD(H) and decreases NADP(H) levels in a manner dependent on its intracellular localization. Collectively, our data indicate that NOCT can regulate levels of both mRNAs and NADP(H) cofactors in a manner specified by its location in cells.
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Affiliation(s)
- Elizabeth T Abshire
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA; Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Kelsey L Hughes
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA
| | - Rucheng Diao
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Sarah Pearce
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institute, Solna, Sweden; Max Planck Institute Biology of Ageing - Karolinska Institute Laboratory, Karolinska Institute, Stockholm, Sweden
| | - Shreekara Gopalakrishna
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institute, Solna, Sweden
| | - Raymond C Trievel
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Joanna Rorbach
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institute, Solna, Sweden; Max Planck Institute Biology of Ageing - Karolinska Institute Laboratory, Karolinska Institute, Stockholm, Sweden
| | - Peter L Freddolino
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA; Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Aaron C Goldstrohm
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, USA.
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17
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Graepel KW, Agostini ML, Lu X, Sexton NR, Denison MR. Fitness Barriers Limit Reversion of a Proofreading-Deficient Coronavirus. J Virol 2019; 93:e00711-19. [PMID: 31341046 DOI: 10.1128/JVI.00711-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 07/05/2019] [Indexed: 12/28/2022] Open
Abstract
Coronaviruses encode an exoribonuclease (ExoN) that is important for viral replication, fitness, and virulence, yet coronaviruses with a defective ExoN (ExoN-AA) have not reverted under diverse experimental conditions. In this study, we identify multiple impediments to MHV-ExoN-AA reversion. We show that ExoN-AA reversion is possible but evolutionarily unfavorable. Instead, compensatory mutations outside ExoN-AA motif I are more accessible and beneficial than partial reversion. We also show that coevolution between replicase proteins over long-term passage partially compensates for ExoN-AA motif I but renders the virus inhospitable to a reverted ExoN. Our results reveal the evolutionary basis for the genetic stability of ExoN-inactivating mutations, illuminate complex functional and evolutionary relationships between coronavirus replicase proteins, and identify potential mechanisms for stabilization of ExoN-AA coronavirus mutants. The 3′-to-5′ exoribonuclease in coronavirus (CoV) nonstructural protein 14 (nsp14-ExoN) mediates RNA proofreading during genome replication. ExoN catalytic residues are arranged in three motifs: I (DE), II (E), and III (D). Alanine replacement of the motif I residues (AA-E-D; four nucleotide substitutions) in murine hepatitis virus (MHV) and severe acute respiratory syndrome (SARS)-CoV yields viable mutants with impaired replication and fitness, increased mutation rates, and attenuated virulence in vivo. Despite these impairments, MHV- and SARS-CoV ExoN motif I AA mutants (ExoN-AA) have not reverted at motif I in diverse in vitro and in vivo environments, suggesting that profound fitness barriers prevent motif I reversion. To test this hypothesis, we engineered MHV-ExoN-AA with 1, 2, or 3 nucleotide mutations along genetic pathways to AA-to-DE reversion. We show that engineered intermediate revertants were viable but had no increased replication or competitive fitness compared to that of MHV-ExoN-AA. In contrast, a low-passage-number (passage 10 [P10]) MHV-ExoN-AA showed increased replication and competitive fitness without reversion of ExoN-AA. Finally, engineered reversion of ExoN-AA to ExoN-DE in the presence of ExoN-AA passage-adaptive mutations resulted in significant fitness loss. These results demonstrate that while reversion is possible, at least one alternative adaptive pathway is more rapidly advantageous than intermediate revertants and may alter the genetic background to render reversion detrimental to fitness. Our results provide an evolutionary rationale for lack of ExoN-AA reversion, illuminate potential multiprotein replicase interactions and coevolution, and support future studies aimed at stabilizing attenuated CoV ExoN-AA mutants. IMPORTANCE Coronaviruses encode an exoribonuclease (ExoN) that is important for viral replication, fitness, and virulence, yet coronaviruses with a defective ExoN (ExoN-AA) have not reverted under diverse experimental conditions. In this study, we identify multiple impediments to MHV-ExoN-AA reversion. We show that ExoN-AA reversion is possible but evolutionarily unfavorable. Instead, compensatory mutations outside ExoN-AA motif I are more accessible and beneficial than partial reversion. We also show that coevolution between replicase proteins over long-term passage partially compensates for ExoN-AA motif I but renders the virus inhospitable to a reverted ExoN. Our results reveal the evolutionary basis for the genetic stability of ExoN-inactivating mutations, illuminate complex functional and evolutionary relationships between coronavirus replicase proteins, and identify potential mechanisms for stabilization of ExoN-AA coronavirus mutants.
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18
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Ogando NS, Ferron F, Decroly E, Canard B, Posthuma CC, Snijder EJ. The Curious Case of the Nidovirus Exoribonuclease: Its Role in RNA Synthesis and Replication Fidelity. Front Microbiol 2019; 10:1813. [PMID: 31440227 PMCID: PMC6693484 DOI: 10.3389/fmicb.2019.01813] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 07/23/2019] [Indexed: 12/20/2022] Open
Abstract
Among RNA viruses, the order Nidovirales stands out for including viruses with the largest RNA genomes currently known. Nidoviruses employ a complex RNA-synthesizing machinery comprising a variety of non-structural proteins (nsps). One of the postulated drivers of the expansion of nidovirus genomes is the presence of a proofreading 3′-to-5′ exoribonuclease (ExoN) belonging to the DEDDh family. ExoN may enhance the fidelity of RNA synthesis by correcting nucleotide incorporation errors made by the RNA-dependent RNA polymerase. Here, we review our current understanding of ExoN evolution, structure, and function. Most experimental data are derived from studies of the ExoN domain of coronaviruses (CoVs), which were triggered by the bioinformatics-based identification of ExoN in the genome of severe acute respiratory syndrome coronavirus (SARS-CoV) and its relatives in 2003. Although convincing data supporting the proofreading hypothesis have been obtained, from biochemical assays and studies with CoV mutants lacking ExoN functionality, the features of ExoN from most other nidovirus families remain to be characterized. Remarkably, viable ExoN knockout mutants were obtained only for two CoVs, mouse hepatitis virus (MHV) and SARS-CoV, whose RNA synthesis and replication kinetics were mildly affected by the lack of ExoN function. In several other CoV species, ExoN inactivation was not tolerated, and knockout mutants could not be rescued when launched using a reverse genetics system. This suggests that ExoN is also critical for primary viral RNA synthesis, a property that poorly matches the profile of an enzyme that would merely boost long-term replication fidelity. In CoVs, ExoN resides in a bifunctional replicase subunit (nsp14) whose C-terminal part has (N7-guanine)-methyltransferase activity. The crystal structure of SARS-CoV nsp14 has shed light on the interplay between these two domains, and on nsp14’s interactions with nsp10, a co-factor that strongly enhances ExoN activity in vitro assays. Further elucidation of the structure-function relationships of ExoN and its interactions with other (viral and/or host) members of the CoV replication machinery will be key to understanding the enzyme’s role in viral RNA synthesis and pathogenesis, and may contribute to the design of new approaches to combat emerging nidoviruses.
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Affiliation(s)
- Natacha S Ogando
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Francois Ferron
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France.,European Virus Bioinformatics Center, Jena, Germany
| | - Etienne Decroly
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France
| | - Bruno Canard
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France
| | - Clara C Posthuma
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Eric J Snijder
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
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19
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Weick EM, Puno MR, Januszyk K, Zinder JC, DiMattia MA, Lima CD. Helicase-Dependent RNA Decay Illuminated by a Cryo-EM Structure of a Human Nuclear RNA Exosome-MTR4 Complex. Cell 2018; 173:1663-1677.e21. [PMID: 29906447 DOI: 10.1016/j.cell.2018.05.041] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 04/26/2018] [Accepted: 05/17/2018] [Indexed: 01/08/2023]
Abstract
The ribonucleolytic RNA exosome interacts with RNA helicases to degrade RNA. To understand how the 3' to 5' Mtr4 helicase engages RNA and the nuclear exosome, we reconstituted 14-subunit Mtr4-containing RNA exosomes from Saccharomyces cerevisiae, Schizosaccharomyces pombe, and human and show that they unwind structured substrates to promote degradation. We loaded a human exosome with an optimized DNA-RNA chimera that stalls MTR4 during unwinding and determined its structure to an overall resolution of 3.45 Å by cryoelectron microscopy (cryo-EM). The structure reveals an RNA-engaged helicase atop the non-catalytic core, with RNA captured within the central channel and DIS3 exoribonuclease active site. MPP6 tethers MTR4 to the exosome through contacts to the RecA domains of MTR4. EXOSC10 remains bound to the core, but its catalytic module and cofactor C1D are displaced by RNA-engaged MTR4. Competition for the exosome core may ensure that RNA is committed to degradation by DIS3 when engaged by MTR4.
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20
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Fang X, Zhao G, Zhang S, Li Y, Gu H, Li Y, Zhao Q, Qi Y. Chloroplast-to-Nucleus Signaling Regulates MicroRNA Biogenesis in Arabidopsis. Dev Cell 2019; 48:371-382.e4. [PMID: 30595534 DOI: 10.1016/j.devcel.2018.11.046] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 10/15/2018] [Accepted: 11/28/2018] [Indexed: 01/04/2023]
Abstract
As integral regulators in plant development and stress response, microRNAs (miRNAs) themselves need to be tightly regulated. Here, we show that tocopherols (vitamin E), lipid-soluble antioxidants synthesized from tyrosine in chloroplasts, positively regulate the biogenesis of miRNAs. Tocopherols are required for the accumulation of 3'-phosphoadenosine 5'-phosphate (PAP), a retrograde inhibitor of the nuclear exoribonucleases (XRN), which may protect primary miRNAs from being degraded and promote mature miRNA production. Such regulation is involved in heat-induced accumulation of miR398 and plant acquisition of heat tolerance. Our study reveals a chloroplast-to-nucleus signaling mechanism that favors miRNA biogenesis under heat and possibly other environmental perturbations.
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21
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Abstract
MicroRNAs are extensively studied regulatory non-coding small RNAs that silence animal genes throughout most biological processes, typically doing so by binding to partially complementary sequences within target RNAs. A plethora of studies has described detailed mechanisms for microRNA biogenesis and function, as well as their temporal and spatial regulation during development. By inducing translational repression and/or degradation of their target RNAs, microRNAs can contribute to achieve highly specific cell- or tissue-specific gene expression, while their aberrant expression can lead to disease. Yet an unresolved aspect of microRNA biology is how such small RNA molecules are themselves cleared from the cell, especially under circumstances where fast microRNA turnover or specific degradation of individual microRNAs is required. In recent years, it was unexpectedly found that binding of specific target RNAs to microRNAs with extensive complementarity can reverse the outcome, triggering degradation of the bound microRNAs. This emerging pathway, named TDMD for Target RNA-Directed MicroRNA Degradation, leads to microRNA 3'-end tailing by the addition of A/U non-templated nucleotides, trimming or shortening from the 3' end, and highly specific microRNA loss, providing a new layer of microRNA regulation. Originally described in flies and known to be triggered by viral RNAs, novel endogenous instances of TDMD have been uncovered and are now starting to be understood. Here, we review our current knowledge of this pathway and its potential role in the control and diversification of microRNA expression patterns.
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Affiliation(s)
- Federico Fuchs Wightman
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias, Buenos Aires, Argentina
| | - Luciana E Giono
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias, Buenos Aires, Argentina
| | - Juan Pablo Fededa
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | - Manuel de la Mata
- Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias, Buenos Aires, Argentina
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22
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Kretschmer J, Rao H, Hackert P, Sloan KE, Höbartner C, Bohnsack MT. The m 6A reader protein YTHDC2 interacts with the small ribosomal subunit and the 5'-3' exoribonuclease XRN1. RNA 2018; 24:1339-1350. [PMID: 29970596 PMCID: PMC6140455 DOI: 10.1261/rna.064238.117] [Citation(s) in RCA: 154] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 06/26/2018] [Indexed: 05/20/2023]
Abstract
N6-methyladenosine (m6A) modifications in RNAs play important roles in regulating many different aspects of gene expression. While m6As can have direct effects on the structure, maturation, or translation of mRNAs, such modifications can also influence the fate of RNAs via proteins termed "readers" that specifically recognize and bind modified nucleotides. Several YTH domain-containing proteins have been identified as m6A readers that regulate the splicing, translation, or stability of specific mRNAs. In contrast to the other YTH domain-containing proteins, YTHDC2 has several defined domains and here, we have analyzed the contribution of these domains to the RNA and protein interactions of YTHDC2. The YTH domain of YTHDC2 preferentially binds m6A-containing RNAs via a conserved hydrophobic pocket, whereas the ankyrin repeats mediate an RNA-independent interaction with the 5'-3' exoribonuclease XRN1. We show that the YTH and R3H domains contribute to the binding of YTHDC2 to cellular RNAs, and using crosslinking and analysis of cDNA (CRAC), we reveal that YTHDC2 interacts with the small ribosomal subunit in close proximity to the mRNA entry/exit sites. YTHDC2 was recently found to promote a "fast-track" expression program for specific mRNAs, and our data suggest that YTHDC2 accomplishes this by recruitment of the RNA degradation machinery to regulate the stability of m6A-containing mRNAs and by utilizing its distinct RNA-binding domains to bridge interactions between m6A-containing mRNAs and the ribosomes to facilitate their efficient translation.
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Affiliation(s)
- Jens Kretschmer
- Department of Molecular Biology, University Medical Centre Göttingen, 37073 Göttingen, Germany
| | - Harita Rao
- Institute for Organic and Biomolecular Chemistry, Georg-August-University, 37077 Göttingen, Germany
| | - Philipp Hackert
- Department of Molecular Biology, University Medical Centre Göttingen, 37073 Göttingen, Germany
| | - Katherine E Sloan
- Department of Molecular Biology, University Medical Centre Göttingen, 37073 Göttingen, Germany
| | - Claudia Höbartner
- Institute for Organic and Biomolecular Chemistry, Georg-August-University, 37077 Göttingen, Germany
- Institute for Organic Chemistry, University Würzburg, 97074 Würzburg, Germany
| | - Markus T Bohnsack
- Department of Molecular Biology, University Medical Centre Göttingen, 37073 Göttingen, Germany
- Göttingen Center for Molecular Biosciences, Georg-August-University, 37073 Göttingen, Germany
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23
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Abstract
White bream virus (WBV), a poorly characterized plus-strand RNA virus infecting freshwater fish of the Cyprinidae family, is the prototype species of the genus Bafinivirus in the subfamily Torovirinae (family Coronaviridae, order Nidovirales). In common with other nidoviruses featuring >20 kilobase genomes, bafiniviruses have been predicted to encode an exoribonuclease (ExoN) in their replicase gene. Here, we used information on the substrate specificity of bafinivirus 3C-like proteases to express WBV ExoN in an active form in Escherichia coli. The 374-residue protein displayed robust 3'-to-5' exoribonuclease activity in the presence of Mg2+ ions and, unlike its coronavirus homologues, did not require a protein cofactor for activity. Characterization of mutant forms of ExoN provided support for predictions on putative active-site and conserved zinc-binding residues. WBV ExoN was revealed to be most active on double-stranded RNA substrates containing one or two non-paired 3'-terminal nucleotides, supporting its presumed role in increasing the fidelity of the bafinivirus RNA-dependent RNA polymerase.
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Affiliation(s)
- Izabela Durzynska
- 1Centre for Infection and Immunity, Queen's University, Belfast, UK.,†Present address: Department of Cancer Biology, Dana Farber Cancer Institute, Boston, USA.,‡Present address: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, USA
| | - Marc Sauerwald
- 2Institute of Medical Virology, Justus Liebig University, Giessen, Germany
| | - Nadja Karl
- 1Centre for Infection and Immunity, Queen's University, Belfast, UK.,2Institute of Medical Virology, Justus Liebig University, Giessen, Germany
| | | | - John Ziebuhr
- 2Institute of Medical Virology, Justus Liebig University, Giessen, Germany.,1Centre for Infection and Immunity, Queen's University, Belfast, UK
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24
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Wang X, Wang Y, Dou Y, Chen L, Wang J, Jiang N, Guo C, Yao Q, Wang C, Liu L, Yu B, Zheng B, Chekanova JA, Ma J, Ren G. Degradation of unmethylated miRNA/miRNA*s by a DEDDy-type 3' to 5' exoribonuclease Atrimmer 2 in Arabidopsis. Proc Natl Acad Sci U S A 2018; 115:E6659-67. [PMID: 29941559 DOI: 10.1073/pnas.1721917115] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The 3' end methylation catalyzed by HUA Enhancer 1 (HEN1) is a crucial step of small RNA stabilization in plants, yet how unmethylated small RNAs undergo degradation remains largely unknown. Using a reverse genetic approach, we here show that Atrimmer 2 (ATRM2), a DEDDy-type 3' to 5' exoribonuclease, acts in the degradation of unmethylated miRNAs and miRNA*s in Arabidopsis Loss-of-function mutations in ATRM2 partially suppress the morphological defects caused by HEN1 malfunction, with restored levels of a subset of miRNAs and receded expression of corresponding miRNA targets. Dysfunction of ATRM2 has negligible effect on miRNA trimming, and further increase the fertility of hen1 heso1 urt1, a mutant with an almost complete abolishment of miRNA uridylation, indicating that ATRM2 may neither be involved in 3' to 5' trimming nor be the enzyme that specifically degrades uridylated miRNAs. Notably, the fold changes of miRNAs and their corresponding miRNA*s were significantly correlated in hen1 atrm2 versus hen1 Unexpectedly, we observed a marked increase of 3' to 5' trimming of several miRNA*s but not miRNAs in ATRM2 compromised backgrounds. These data suggest an action of ATRM2 on miRNA/miRNA* duplexes, and the existence of an unknown exoribonuclease for specific trimming of miRNA*. This asymmetric effect on miRNA/miRNA* is likely related to Argonaute (AGO) proteins, which can distinguish miRNAs from miRNA*s. Finally, we show that ATRM2 colocalizes and physically interacts with Argonaute 1 (AGO1). Taken together, our results suggest that ATRM2 may be involved in the surveillance of unmethylated miRNA/miRNA* duplexes during the initiation step of RNA-induced silencing complex assembly.
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25
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Flobinus A, Chevigny N, Charley PA, Seissler T, Klein E, Bleykasten-Grosshans C, Ratti C, Bouzoubaa S, Wilusz J, Gilmer D. Beet Necrotic Yellow Vein Virus Noncoding RNA Production Depends on a 5'→3' Xrn Exoribonuclease Activity. Viruses 2018; 10:v10030137. [PMID: 29562720 PMCID: PMC5869530 DOI: 10.3390/v10030137] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 02/28/2018] [Accepted: 03/17/2018] [Indexed: 12/27/2022] Open
Abstract
The RNA3 species of the beet necrotic yellow vein virus (BNYVV), a multipartite positive-stranded RNA phytovirus, contains the 'core' nucleotide sequence required for its systemic movement in Beta macrocarpa. Within this 'core' sequence resides a conserved "coremin" motif of 20 nucleotides that is absolutely essential for long-distance movement. RNA3 undergoes processing steps to yield a noncoding RNA3 (ncRNA3) possessing "coremin" at its 5' end, a mandatory element for ncRNA3 accumulation. Expression of wild-type (wt) or mutated RNA3 in Saccharomyces cerevisiae allows for the accumulation of ncRNA3 species. Screening of S.cerevisiae ribonuclease mutants identified the 5'-to-3' exoribonuclease Xrn1 as a key enzyme in RNA3 processing that was recapitulated both in vitro and in insect cell extracts. Xrn1 stalled on ncRNA3-containing RNA substrates in these decay assays in a similar fashion as the flavivirus Xrn1-resistant structure (sfRNA). Substitution of the BNYVV-RNA3 'core' sequence by the sfRNA sequence led to the accumulation of an ncRNA species in yeast in vitro but not in planta and no viral long distance occurred. Interestingly, XRN4 knockdown reduced BNYVV RNA accumulation suggesting a dual role for the ribonuclease in the viral cycle.
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Affiliation(s)
- Alyssa Flobinus
- Institut de biologie moléculaire des plantes, CNRS UPR2357, Université de Strasbourg, 67084 Strasbourg, France.
| | - Nicolas Chevigny
- Institut de biologie moléculaire des plantes, CNRS UPR2357, Université de Strasbourg, 67084 Strasbourg, France.
| | - Phillida A Charley
- Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, CO 80523-168, USA.
| | - Tanja Seissler
- Institut de biologie moléculaire des plantes, CNRS UPR2357, Université de Strasbourg, 67084 Strasbourg, France.
| | - Elodie Klein
- Institut de biologie moléculaire des plantes, CNRS UPR2357, Université de Strasbourg, 67084 Strasbourg, France.
- SESVanderHave, B3300 Tienen, Belgium.
| | | | - Claudio Ratti
- DipSA-Plant Pathology, University of Bologna, 40127 Bologna, Italy.
| | - Salah Bouzoubaa
- Institut de biologie moléculaire des plantes, CNRS UPR2357, Université de Strasbourg, 67084 Strasbourg, France.
| | - Jeffrey Wilusz
- Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, CO 80523-168, USA.
| | - David Gilmer
- Institut de biologie moléculaire des plantes, CNRS UPR2357, Université de Strasbourg, 67084 Strasbourg, France.
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26
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Case JB, Li Y, Elliott R, Lu X, Graepel KW, Sexton NR, Smith EC, Weiss SR, Denison MR. Murine Hepatitis Virus nsp14 Exoribonuclease Activity Is Required for Resistance to Innate Immunity. J Virol 2018; 92:e01531-17. [PMID: 29046453 DOI: 10.1128/JVI.01531-17] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 10/12/2017] [Indexed: 12/21/2022] Open
Abstract
Coronaviruses (CoVs) are positive-sense RNA viruses that infect numerous mammalian and avian species and are capable of causing severe and lethal disease in humans. CoVs encode several innate immune antagonists that counteract the host innate immune response to facilitate efficient viral replication. CoV nonstructural protein 14 (nsp14) encodes 3'-to-5' exoribonuclease activity (ExoN), which performs a proofreading function and is required for high-fidelity replication. Outside of the order Nidovirales, arenaviruses are the only RNA viruses that encode an ExoN, which functions to degrade double-stranded RNA (dsRNA) replication intermediates. In this study, we tested the hypothesis that CoV ExoN also functions to antagonize the innate immune response. We demonstrate that viruses lacking ExoN activity [ExoN(-)] are sensitive to cellular pretreatment with interferon beta (IFN-β) in a dose-dependent manner. In addition, ExoN(-) virus replication was attenuated in wild-type bone marrow-derived macrophages (BMMs) and partially restored in interferon alpha/beta receptor-deficient (IFNAR-/-) BMMs. ExoN(-) virus replication did not result in IFN-β gene expression, and in the presence of an IFN-β-mediated antiviral state, ExoN(-) viral RNA levels were not substantially reduced relative to those of untreated samples. However, ExoN(-) virus generated from IFN-β-pretreated cells had reduced specific infectivity and decreased relative fitness, suggesting that ExoN(-) virus generated during an antiviral state is less viable to establish a subsequent infection. Overall, our data suggest murine hepatitis virus (MHV) ExoN activity is required for resistance to the innate immune response, and antiviral mechanisms affecting the viral RNA sequence and/or an RNA modification act on viruses lacking ExoN activity.IMPORTANCE CoVs encode multiple antagonists that prevent or disrupt an efficient innate immune response. Additionally, no specific antiviral therapies or vaccines currently exist for human CoV infections. Therefore, the study of CoV innate immune antagonists is essential for understanding how CoVs overcome host defenses and to maximize potential therapeutic interventions. Here, we sought to determine the contributions of nsp14 ExoN activity in the induction of and resistance to the innate immune response. We show that viruses lacking nsp14 ExoN activity are more sensitive than wild-type MHV to restriction by exogenous IFN-β and that viruses produced in the presence of an antiviral state are less capable of establishing a subsequent viral infection. Our results support the hypothesis that murine hepatitis virus ExoN activity is required for resistance to the innate immune response.
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27
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Graepel KW, Lu X, Case JB, Sexton NR, Smith EC, Denison MR. Proofreading-Deficient Coronaviruses Adapt for Increased Fitness over Long-Term Passage without Reversion of Exoribonuclease-Inactivating Mutations. mBio 2017; 8:e01503-17. [PMID: 29114026 PMCID: PMC5676041 DOI: 10.1128/mbio.01503-17] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 10/10/2017] [Indexed: 12/31/2022] Open
Abstract
The coronavirus (CoV) RNA genome is the largest among the single-stranded positive-sense RNA viruses. CoVs encode a proofreading 3'-to-5' exoribonuclease within nonstructural protein 14 (nsp14-ExoN) that is responsible for CoV high-fidelity replication. Alanine substitution of ExoN catalytic residues [ExoN(-)] in severe acute respiratory syndrome-associated coronavirus (SARS-CoV) and murine hepatitis virus (MHV) disrupts ExoN activity, yielding viable mutant viruses with defective replication, up to 20-fold-decreased fidelity, and increased susceptibility to nucleoside analogues. To test the stability of the ExoN(-) genotype and phenotype, we passaged MHV-ExoN(-) 250 times in cultured cells (P250), in parallel with wild-type MHV (WT-MHV). Compared to MHV-ExoN(-) P3, MHV-ExoN(-) P250 demonstrated enhanced replication and increased competitive fitness without reversion at the ExoN(-) active site. Furthermore, MHV-ExoN(-) P250 was less susceptible than MHV-ExoN(-) P3 to multiple nucleoside analogues, suggesting that MHV-ExoN(-) was under selection for increased replication fidelity. We subsequently identified novel amino acid changes within the RNA-dependent RNA polymerase and nsp14 of MHV-ExoN(-) P250 that partially accounted for the reduced susceptibility to nucleoside analogues. Our results suggest that increased replication fidelity is selected in ExoN(-) CoVs and that there may be a significant barrier to ExoN(-) reversion. These results also support the hypothesis that high-fidelity replication is linked to CoV fitness and indicate that multiple replicase proteins could compensate for ExoN functions during replication.IMPORTANCE Uniquely among RNA viruses, CoVs encode a proofreading exoribonuclease (ExoN) in nsp14 that mediates high-fidelity RNA genome replication. Proofreading-deficient CoVs with disrupted ExoN activity [ExoN(-)] either are nonviable or have significant defects in replication, RNA synthesis, fidelity, fitness, and virulence. In this study, we showed that ExoN(-) murine hepatitis virus can adapt during long-term passage for increased replication and fitness without reverting the ExoN-inactivating mutations. Passage-adapted ExoN(-) mutants also demonstrate increasing resistance to nucleoside analogues that is explained only partially by secondary mutations in nsp12 and nsp14. These data suggest that enhanced resistance to nucleoside analogues is mediated by the interplay of multiple replicase proteins and support the proposed link between CoV fidelity and fitness.
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Affiliation(s)
- Kevin W Graepel
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Xiaotao Lu
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - James Brett Case
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Nicole R Sexton
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Everett Clinton Smith
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Biology, the University of the South, Sewanee, Tennessee, USA
| | - Mark R Denison
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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28
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Abstract
In this review, Zinder and Lima highlight recent advances that have illuminated roles for the RNA exosome and its cofactors in specific biological pathways, alongside studies that attempted to dissect these activities through structural and biochemical characterization of nuclear and cytoplasmic RNA exosome complexes. The eukaryotic RNA exosome is an essential and conserved protein complex that can degrade or process RNA substrates in the 3′-to-5′ direction. Since its discovery nearly two decades ago, studies have focused on determining how the exosome, along with associated cofactors, achieves the demanding task of targeting particular RNAs for degradation and/or processing in both the nucleus and cytoplasm. In this review, we highlight recent advances that have illuminated roles for the RNA exosome and its cofactors in specific biological pathways, alongside studies that attempted to dissect these activities through structural and biochemical characterization of nuclear and cytoplasmic RNA exosome complexes.
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Affiliation(s)
- John C Zinder
- Tri-Institutional Training Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA.,Structural Biology Program, Sloan Kettering Institute, New York, New York, 10065, USA
| | - Christopher D Lima
- Structural Biology Program, Sloan Kettering Institute, New York, New York, 10065, USA.,Howard Hughes Medical Institute, New York, New York, 10065 USA
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29
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Tomecki R, Sikorski PJ, Zakrzewska-Placzek M. Comparison of preribosomal RNA processing pathways in yeast, plant and human cells - focus on coordinated action of endo- and exoribonucleases. FEBS Lett 2017; 591:1801-1850. [PMID: 28524231 DOI: 10.1002/1873-3468.12682] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 05/14/2017] [Accepted: 05/15/2017] [Indexed: 12/17/2022]
Abstract
Proper regulation of ribosome biosynthesis is mandatory for cellular adaptation, growth and proliferation. Ribosome biogenesis is the most energetically demanding cellular process, which requires tight control. Abnormalities in ribosome production have severe consequences, including developmental defects in plants and genetic diseases (ribosomopathies) in humans. One of the processes occurring during eukaryotic ribosome biogenesis is processing of the ribosomal RNA precursor molecule (pre-rRNA), synthesized by RNA polymerase I, into mature rRNAs. It must not only be accurate but must also be precisely coordinated with other phenomena leading to the synthesis of functional ribosomes: RNA modification, RNA folding, assembly with ribosomal proteins and nucleocytoplasmic RNP export. A multitude of ribosome biogenesis factors ensure that these events take place in a correct temporal order. Among them are endo- and exoribonucleases involved in pre-rRNA processing. Here, we thoroughly present a wide spectrum of ribonucleases participating in rRNA maturation, focusing on their biochemical properties, regulatory mechanisms and substrate specificity. We also discuss cooperation between various ribonucleolytic activities in particular stages of pre-rRNA processing, delineating major similarities and differences between three representative groups of eukaryotes: yeast, plants and humans.
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Affiliation(s)
- Rafal Tomecki
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.,Department of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Poland
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30
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Zhang Z, Hu F, Sung MW, Shu C, Castillo-González C, Koiwa H, Tang G, Dickman M, Li P, Zhang X. RISC-interacting clearing 3'- 5' exoribonucleases (RICEs) degrade uridylated cleavage fragments to maintain functional RISC in Arabidopsis thaliana. eLife 2017; 6. [PMID: 28463111 PMCID: PMC5451212 DOI: 10.7554/elife.24466] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 04/29/2017] [Indexed: 01/01/2023] Open
Abstract
RNA-induced silencing complex (RISC) is composed of miRNAs and AGO proteins. AGOs use miRNAs as guides to slice target mRNAs to produce truncated 5' and 3' RNA fragments. The 5' cleaved RNA fragments are marked with uridylation for degradation. Here, we identified novel cofactors of Arabidopsis AGOs, named RICE1 and RICE2. RICE proteins specifically degraded single-strand (ss) RNAs in vitro; but neither miRNAs nor miRNA*s in vivo. RICE1 exhibited a DnaQ-like exonuclease fold and formed a homohexamer with the active sites located at the interfaces between RICE1 subunits. Notably, ectopic expression of catalytically-inactive RICE1 not only significantly reduced miRNA levels; but also increased 5' cleavage RISC fragments with extended uridine tails. We conclude that RICEs act to degrade uridylated 5’ products of AGO cleavage to maintain functional RISC. Our study also suggests a possible link between decay of cleaved target mRNAs and miRNA stability in RISC. DOI:http://dx.doi.org/10.7554/eLife.24466.001 DNA contains all the information needed to build a body, yet molecules of RNA carry these instructions to the sites in the cell where they can be used. Cells must control how much RNA they produce in order to ensure that they develop properly and can respond well to their environment. RNA silencing refers to a collection of mechanisms that use smaller RNA molecules called microRNAs to incapacitate certain RNA molecules and selectively switch off the genes that encode them to stop more from being made. One key player in RNA silencing is the multi-protein complex called RISC, which contains microRNA and a group of proteins called AGOs. Once the microRNA has identified its RNA target, the AGOs cut the RNA into two pieces, known as the 5’ cleavage fragment and 3’ cleavage fragment. The two resulting fragments need to be cleared away swiftly, so that the RISC can move on to the next target. While it was known how the 3’ cleavage fragment was removed, it was less clear how the 5’ cleavage fragment was dealt with. Previous studies had shown that the 5’ cleavage fragment was marked with a chemical called uridine, which somehow signals to the RISC that this fragment needs to be destroyed. Now, using biochemical techniques, Zhang et al. have identified two new proteins in the model plant Arabidopsis that attach to the AGO proteins and degrade the 5’ cleavage fragments that are marked with uridine. The two proteins are named RICE1 and RICE2. Zhang et al. then analyzed the three-dimensional shape of RICE1 and identified the ‘active’ region that is responsible for degrading the RNA fragments. When these active regions were blocked, the microRNA levels were low, but the uridine-marked 5’ cleavage fragments were high. Also, the RISC complex could not work properly, which lead to problems during the development of the plant. These results suggest that RICE proteins degrade 5’ cleavage fragments modified with uridine to activate RISC. RICE proteins are conserved between plants and animals, and it is likely that their counterparts in humans will have a similar role to the plant proteins. The next challenge will be to explore how RICE proteins work in more details, which may lead to new ways to manipulate the levels of microRNAs to change the architecture of the plant and to improve their tolerance to various stress conditions. DOI:http://dx.doi.org/10.7554/eLife.24466.002
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Affiliation(s)
- Zhonghui Zhang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States.,Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, United States
| | - Fuqu Hu
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States.,Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, United States
| | - Min Woo Sung
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States
| | - Chang Shu
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States
| | - Claudia Castillo-González
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States.,Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, United States
| | - Hisashi Koiwa
- Department of Horticulture, Texas A&M University, College Station, United States
| | - Guiliang Tang
- Department of Biological Sciences, Michigan Technological University, Houghton, United States
| | - Martin Dickman
- Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, United States
| | - Pingwei Li
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States
| | - Xiuren Zhang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States.,Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, United States
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31
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Lin CJ, Wen J, Bejarano F, Hu F, Bortolamiol-Becet D, Kan L, Sanfilippo P, Kondo S, Lai EC. Characterization of a TUTase/RNase complex required for Drosophila gametogenesis. RNA 2017; 23:284-296. [PMID: 27974621 PMCID: PMC5311484 DOI: 10.1261/rna.059527.116] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 12/07/2016] [Indexed: 06/06/2023]
Abstract
Post-transcriptional regulatory strategies that involve coupling between terminal uridyltransferase (TUTase) and exoribonuclease enzymes have recently been characterized in diverse species. Of note, the 3' exoribonuclease Dis3L2 has received substantial attention as a factor that metabolizes uridylated substrates in contexts such as general mRNA degradation, turnover of specific miRNAs, and quality control of noncoding RNAs. To date, most studies of Dis3L2 have focused on fungi and mammalian cells. Here, we introduce Drosophila as a system that permits analysis of molecular mechanisms as well as the ability to interrogate organismal phenotypes. We started with a structure-function analysis of the Drosophila TUTase Tailor, which we recently identified to inhibit biogenesis of splicing-derived miRNA hairpins. Next, we show that Tailor/Dis3L2 form a complex via N-terminal domains in the respective proteins that are distinct from their catalytic domains. In vitro, Dis3L2 has nuclease activity, but substrate oligouridylation by Tailor stimulates their degradation by Dis3L2, especially for structured substrates. We analyzed mutants of Tailor and Dis3L2, which are viable and lack overt morphological defects. Instead, these mutants exhibit defects in female and male fertility, implying specific requirements in the germline. Dis3L2 defects are more severe than Tailor, and their requirements appear stronger in males than in females. In particular, loss of Dis3L2 completely blocks productive spermatogenesis, causing male sterility. RNA-seq analysis from single- and double-mutant testes reveals aberrant gene expression programs and suggests that noncoding RNAs may be preferentially affected by Dis3L2. Overall, our studies of a new tailing/trimming complex reveal unexpectedly specific requirements during gametogenesis.
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Affiliation(s)
- Ching-Jung Lin
- Sloan-Kettering Institute, Department of Developmental Biology, New York, New York 10065, USA
- Weill Graduate School of Medical Sciences, Cornell University, New York, New York 10065, USA
| | - Jiayu Wen
- Sloan-Kettering Institute, Department of Developmental Biology, New York, New York 10065, USA
| | - Fernando Bejarano
- Sloan-Kettering Institute, Department of Developmental Biology, New York, New York 10065, USA
| | - Fuqu Hu
- Sloan-Kettering Institute, Department of Developmental Biology, New York, New York 10065, USA
| | - Diane Bortolamiol-Becet
- Sloan-Kettering Institute, Department of Developmental Biology, New York, New York 10065, USA
| | - Lijuan Kan
- Sloan-Kettering Institute, Department of Developmental Biology, New York, New York 10065, USA
| | - Piero Sanfilippo
- Sloan-Kettering Institute, Department of Developmental Biology, New York, New York 10065, USA
- Louis V. Gerstner Jr. Graduate School of Biomedical Sciences, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA
| | - Shu Kondo
- Invertebrate Genetics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Eric C Lai
- Sloan-Kettering Institute, Department of Developmental Biology, New York, New York 10065, USA
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Hausmann S, Guimarães VA, Garcin D, Baumann N, Linder P, Redder P. Both exo- and endo-nucleolytic activities of RNase J1 from Staphylococcus aureus are manganese dependent and active on triphosphorylated 5'-ends. RNA Biol 2017; 14:1431-1443. [PMID: 28277929 DOI: 10.1080/15476286.2017.1300223] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
RNA decay and RNA maturation are important steps in the regulation of bacterial gene expression. RNase J, which is present in about half of bacterial species, has been shown to possess both endo- and 5' to 3' exo-ribonuclease activities. The exonucleolytic activity is clearly involved in the degradation of mRNA and in the maturation of at least the 5' end of 16S rRNA in the 2 Firmicutes Staphylococcus aureus and Bacillus subtilis. The endoribonuclease activity of RNase J from several species has been shown to be weak in vitro and 3-D structural data of different RNase J orthologs have not provided a clear explanation for the molecular basis of this activity. Here, we show that S. aureus RNase J1 is a manganese dependent homodimeric enzyme with strong 5' to 3' exo-ribonuclease as well as endo-ribonuclease activity. In addition, we demonstrated that SauJ1 can efficiently degrade 5' triphosphorylated RNA. Our results highlight RNase J1 as an important player in RNA turnover in S. aureus.
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Affiliation(s)
- Stéphane Hausmann
- a Department of Microbiology and Molecular Medicine , Medical Faculty, University of Geneva , Geneva , Switzerland
| | - Vanessa Andrade Guimarães
- a Department of Microbiology and Molecular Medicine , Medical Faculty, University of Geneva , Geneva , Switzerland
| | - Dominique Garcin
- a Department of Microbiology and Molecular Medicine , Medical Faculty, University of Geneva , Geneva , Switzerland
| | - Natalia Baumann
- a Department of Microbiology and Molecular Medicine , Medical Faculty, University of Geneva , Geneva , Switzerland
| | - Patrick Linder
- a Department of Microbiology and Molecular Medicine , Medical Faculty, University of Geneva , Geneva , Switzerland
| | - Peter Redder
- a Department of Microbiology and Molecular Medicine , Medical Faculty, University of Geneva , Geneva , Switzerland.,b Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative, Université de Toulouse III Toulouse , France
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Mermigka G, Helm JM, Vlatakis I, Schumacher HT, Vamvaka E, Kalantidis K. ERIL1, the plant homologue of ERI-1, is involved in the processing of chloroplastic rRNAs. Plant J 2016; 88:839-853. [PMID: 27531275 DOI: 10.1111/tpj.13304] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 08/05/2016] [Accepted: 08/09/2016] [Indexed: 06/06/2023]
Abstract
Proteins belonging to the enhancer of RNA interference-1 subfamily of 3'-5' exoribonucleases participate in divergent RNA pathways. They degrade small interfering RNAs (siRNAs), thus suppressing RNA interference, and are involved in the maturation of ribosomal RNAs and the degradation of histone messenger RNAs (mRNAs). Here, we report evidence for the role of the plant homologue of these proteins, which we termed ENHANCED RNA INTERFERENCE-1-LIKE-1 (ERIL1), in chloroplast function. In vitro assays with AtERIL1 proved that the conserved 3'-5' exonuclease activity is shared among all homologues studied. Confocal microscopy revealed that ERL1, a nucleus-encoded protein, is targeted to the chloroplast. To gain insight into its role in plants, we used Nicotiana benthamiana and Arabidopsis thaliana plants that constitutively overexpress or suppress ERIL1. In the mutant lines of both species we observed malfunctions in photosynthetic ability. Molecular analysis showed that ERIL1 participates in the processing of chloroplastic ribosomal RNAs (rRNAs). Lastly, our results suggest that the missexpression of ERIL1 may have an indirect effect on the microRNA (miRNA) pathway. Altogether our data point to an additional piece of the puzzle in the complex RNA metabolism of chloroplasts.
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Affiliation(s)
- Glykeria Mermigka
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion/Crete, GR-71409, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion/Crete, GR-71110, Greece
| | - Jutta Maria Helm
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion/Crete, GR-71110, Greece
| | - Ioannis Vlatakis
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion/Crete, GR-71409, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion/Crete, GR-71110, Greece
| | - Heiko Tobias Schumacher
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion/Crete, GR-71110, Greece
| | - Evgenia Vamvaka
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion/Crete, GR-71409, Greece
| | - Kriton Kalantidis
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion/Crete, GR-71409, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas, Heraklion/Crete, GR-71110, Greece
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Zinder JC, Wasmuth EV, Lima CD. Nuclear RNA Exosome at 3.1 Å Reveals Substrate Specificities, RNA Paths, and Allosteric Inhibition of Rrp44/Dis3. Mol Cell 2016; 64:734-745. [PMID: 27818140 DOI: 10.1016/j.molcel.2016.09.038] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 09/12/2016] [Accepted: 09/28/2016] [Indexed: 01/24/2023]
Abstract
The eukaryotic RNA exosome is an essential and conserved 3'-to-5' exoribonuclease complex that degrades or processes nearly every class of cellular RNA. The nuclear RNA exosome includes a 9-subunit non-catalytic core that binds Rrp44 (Dis3) and Rrp6 subunits to modulate their processive and distributive 3'-to-5' exoribonuclease activities, respectively. Here we utilize an engineered RNA with two 3' ends to obtain a crystal structure of an 11-subunit nuclear exosome bound to RNA at 3.1 Å. The structure reveals an extended RNA path to Rrp6 that penetrates into the non-catalytic core; contacts between the non-catalytic core and Rrp44, which inhibit exoribonuclease activity; and features of the Rrp44 exoribonuclease site that support its ability to degrade 3' phosphate RNA substrates. Using reconstituted exosome complexes, we show that 3' phosphate RNA is not a substrate for Rrp6 but is readily degraded by Rrp44 in the nuclear exosome.
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Affiliation(s)
- John C Zinder
- Tri-Institutional Training Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Structural Biology Program, Sloan Kettering Institute, 1275 York Avenue, New York, NY 10065, USA
| | - Elizabeth V Wasmuth
- Structural Biology Program, Sloan Kettering Institute, 1275 York Avenue, New York, NY 10065, USA
| | - Christopher D Lima
- Structural Biology Program, Sloan Kettering Institute, 1275 York Avenue, New York, NY 10065, USA; Howard Hughes Medical Institute, 1275 York Avenue, New York, NY 10065, USA.
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35
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Reimão-Pinto MM, Manzenreither RA, Burkard TR, Sledz P, Jinek M, Mechtler K, Ameres SL. Molecular basis for cytoplasmic RNA surveillance by uridylation-triggered decay in Drosophila. EMBO J 2016; 35:2417-2434. [PMID: 27729457 DOI: 10.15252/embj.201695164] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/10/2016] [Accepted: 09/14/2016] [Indexed: 01/01/2023] Open
Abstract
The posttranscriptional addition of nucleotides to the 3' end of RNA regulates the maturation, function, and stability of RNA species in all domains of life. Here, we show that in flies, 3' terminal RNA uridylation triggers the processive, 3'-to-5' exoribonucleolytic decay via the RNase II/R enzyme CG16940, a homolog of the human Perlman syndrome exoribonuclease Dis3l2. Together with the TUTase Tailor, dmDis3l2 forms the cytoplasmic, terminal RNA uridylation-mediated processing (TRUMP) complex that functionally cooperates in the degradation of structured RNA RNA immunoprecipitation and high-throughput sequencing reveals a variety of TRUMP complex substrates, including abundant non-coding RNA, such as 5S rRNA, tRNA, snRNA, snoRNA, and the essential RNase MRP Based on genetic and biochemical evidence, we propose a key function of the TRUMP complex in the cytoplasmic quality control of RNA polymerase III transcripts. Together with high-throughput biochemical characterization of dmDis3l2 and bacterial RNase R, our results imply a conserved molecular function of RNase II/R enzymes as "readers" of destabilizing posttranscriptional marks-uridylation in eukaryotes and adenylation in prokaryotes-that play important roles in RNA surveillance.
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Affiliation(s)
| | | | - Thomas R Burkard
- Institute of Molecular Biotechnology, IMBA, Vienna Biocenter Campus (VBC), Vienna, Austria
| | - Pawel Sledz
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Martin Jinek
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Karl Mechtler
- Institute of Molecular Biotechnology, IMBA, Vienna Biocenter Campus (VBC), Vienna, Austria
| | - Stefan L Ameres
- Institute of Molecular Biotechnology, IMBA, Vienna Biocenter Campus (VBC), Vienna, Austria
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Towler BP, Jones CI, Viegas SC, Apura P, Waldron JA, Smalley SK, Arraiano CM, Newbury SF. The 3'-5' exoribonuclease Dis3 regulates the expression of specific microRNAs in Drosophila wing imaginal discs. RNA Biol 2016; 12:728-41. [PMID: 25892215 PMCID: PMC4615222 DOI: 10.1080/15476286.2015.1040978] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Dis3 is a highly conserved exoribonuclease which degrades RNAs in the 3'-5' direction. Mutations in Dis3 are associated with a number of human cancers including multiple myeloma and acute myeloid leukemia. In this work, we have assessed the effect of a Dis3 knockdown on Drosophila imaginal disc development and on expression of mature microRNAs. We find that Dis3 knockdown severely disrupts the development of wing imaginal discs in that the flies have a “no wing” phenotype. Use of RNA-seq to quantify the effect of Dis3 knockdown on microRNA expression shows that Dis3 normally regulates a small subset of microRNAs, with only 11 (10.1%) increasing in level ≥2-fold and 6 (5.5%) decreasing in level ≥2-fold. Of these microRNAs, miR-252–5p is increased 2.1-fold in Dis3-depleted cells compared to controls while the level of the miR-252 precursor is unchanged, suggesting that Dis3 can act in the cytoplasm to specifically degrade this mature miRNA. Furthermore, our experiments suggest that Dis3 normally interacts with the exosomal subunit Rrp40 in the cytoplasm to target miR-252–5p for degradation during normal wing development. Another microRNA, miR-982–5p, is expressed at lower levels in Dis3 knockdown cells, while the miR-982 precursor remains unchanged, indicating that Dis3 is involved in its processing. Our study therefore reveals an unexpected specificity for this ribonuclease toward microRNA regulation, which is likely to be conserved in other eukaryotes and may be relevant to understanding its role in human disease.
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Affiliation(s)
- Benjamin P Towler
- a Brighton and Sussex Medical School; Medical Research Building; University of Sussex; Falmer , Brighton , UK
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Fazal FM, Koslover DJ, Luisi BF, Block SM. Direct observation of processive exoribonuclease motion using optical tweezers. Proc Natl Acad Sci U S A 2015; 112:15101-6. [PMID: 26598710 DOI: 10.1073/pnas.1514028112] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Bacterial RNases catalyze the turnover of RNA and are essential for gene expression and quality surveillance of transcripts. In Escherichia coli, the exoribonucleases RNase R and polynucleotide phosphorylase (PNPase) play critical roles in degrading RNA. Here, we developed an optical-trapping assay to monitor the translocation of individual enzymes along RNA-based substrates. Single-molecule records of motion reveal RNase R to be highly processive: one molecule can unwind over 500 bp of a structured substrate. However, enzyme progress is interrupted by pausing and stalling events that can slow degradation in a sequence-dependent fashion. We found that the distance traveled by PNPase through structured RNA is dependent on the A+U content of the substrate and that removal of its KH and S1 RNA-binding domains can reduce enzyme processivity without affecting the velocity. By a periodogram analysis of single-molecule records, we establish that PNPase takes discrete steps of six or seven nucleotides. These findings, in combination with previous structural and biochemical data, support an asymmetric inchworm mechanism for PNPase motion. The assay developed here for RNase R and PNPase is well suited to studies of other exonucleases and helicases.
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Robinson SR, Oliver AW, Chevassut TJ, Newbury SF. The 3' to 5' Exoribonuclease DIS3: From Structure and Mechanisms to Biological Functions and Role in Human Disease. Biomolecules 2015; 5:1515-39. [PMID: 26193331 PMCID: PMC4598762 DOI: 10.3390/biom5031515] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 07/01/2015] [Accepted: 07/06/2015] [Indexed: 12/03/2022] Open
Abstract
DIS3 is a conserved exoribonuclease and catalytic subunit of the exosome, a protein complex involved in the 3' to 5' degradation and processing of both nuclear and cytoplasmic RNA species. Recently, aberrant expression of DIS3 has been found to be implicated in a range of different cancers. Perhaps most striking is the finding that DIS3 is recurrently mutated in 11% of multiple myeloma patients. Much work has been done to elucidate the structural and biochemical characteristics of DIS3, including the mechanistic details of its role as an effector of RNA decay pathways. Nevertheless, we do not understand how DIS3 mutations can lead to cancer. There are a number of studies that pertain to the function of DIS3 at the organismal level. Mutant phenotypes in S. pombe, S. cerevisiae and Drosophila suggest DIS3 homologues have a common role in cell-cycle progression and microtubule assembly. DIS3 has also recently been implicated in antibody diversification of mouse B-cells. This article aims to review current knowledge of the structure, mechanisms and functions of DIS3 as well as highlighting the genetic patterns observed within myeloma patients, in order to yield insight into the putative role of DIS3 mutations in oncogenesis.
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Affiliation(s)
- Sophie R Robinson
- Medical Research Building, Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton BN1 9PS, UK.
| | - Antony W Oliver
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK.
| | - Timothy J Chevassut
- Medical Research Building, Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton BN1 9PS, UK.
| | - Sarah F Newbury
- Medical Research Building, Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton BN1 9PS, UK.
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Ma Y, Wu L, Shaw N, Gao Y, Wang J, Sun Y, Lou Z, Yan L, Zhang R, Rao Z. Structural basis and functional analysis of the SARS coronavirus nsp14-nsp10 complex. Proc Natl Acad Sci U S A 2015; 112:9436-41. [PMID: 26159422 DOI: 10.1073/pnas.1508686112] [Citation(s) in RCA: 331] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nonstructural protein 14 (nsp14) of coronaviruses (CoV) is important for viral replication and transcription. The N-terminal exoribonuclease (ExoN) domain plays a proofreading role for prevention of lethal mutagenesis, and the C-terminal domain functions as a (guanine-N7) methyl transferase (N7-MTase) for mRNA capping. The molecular basis of both these functions is unknown. Here, we describe crystal structures of severe acute respiratory syndrome (SARS)-CoV nsp14 in complex with its activator nonstructural protein10 (nsp10) and functional ligands. One molecule of nsp10 interacts with ExoN of nsp14 to stabilize it and stimulate its activity. Although the catalytic core of nsp14 ExoN is reminiscent of proofreading exonucleases, the presence of two zinc fingers sets it apart from homologs. Mutagenesis studies indicate that both these zinc fingers are essential for the function of nsp14. We show that a DEEDh (the five catalytic amino acids) motif drives nucleotide excision. The N7-MTase domain exhibits a noncanonical MTase fold with a rare β-sheet insertion and a peripheral zinc finger. The cap-precursor guanosine-P3-adenosine-5',5'-triphosphate and S-adenosyl methionine bind in proximity in a highly constricted pocket between two β-sheets to accomplish methyl transfer. Our studies provide the first glimpses, to our knowledge, into the architecture of the nsp14-nsp10 complex involved in RNA viral proofreading.
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Abstract
Ribonucleases (RNases) play an essential role in essentially every aspect of RNA metabolism, but they also can be destructive enzymes that need to be regulated to avoid unwanted degradation of RNA molecules. As a consequence, cells have evolved multiple strategies to protect RNAs against RNase action. They also utilize a variety of mechanisms to regulate the RNases themselves. These include post-transcriptional regulation, post-translational modification, trans-acting inhibitors, cellular localization, as well as others that are less well studied. In this review, I will briefly discuss how RNA molecules are protected and then examine in detail our current understanding of the mechanisms known to regulate individual RNases.
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Affiliation(s)
- Murray P Deutscher
- Biochemistry & Molecular Biology, University of Miami, Miami, FL 33136-6129, USA
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41
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Abstract
When judged by ubiquity, adaptation, and emergence of new diseases, RNA viruses are arguably the most successful biological organisms. This success has been attributed to a defect of sorts: high mutation rates (low fidelity) resulting in mutant swarms that allow rapid selection for fitness in new environments. Studies of viruses with small RNA genomes have identified fidelity determinants in viral RNA-dependent RNA polymerases and have shown that RNA viruses likely replicate within a limited fidelity range to maintain fitness. In this review we compare the fidelity of small RNA viruses with that of the largest RNA viruses, the coronaviruses. Coronaviruses encode the first known viral RNA proofreading exoribonuclease, a function that likely allowed expansion of the coronavirus genome and that dramatically increases replication fidelity and the range of tolerated variation. We propose models for regulation of coronavirus fidelity and discuss the implications of altered fidelity for RNA virus replication, pathogenesis, and evolution.
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Affiliation(s)
- Everett Clinton Smith
- Department of Pediatrics.,Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee 37232;
| | - Nicole R Sexton
- Department of Pathology, Microbiology, and Immunology, and.,Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee 37232;
| | - Mark R Denison
- Department of Pediatrics.,Department of Pathology, Microbiology, and Immunology, and.,Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee 37232;
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42
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Bouvet M, Imbert I, Ferron F, Canard B, Decroly E. Structures and exoribonuclease activity fonctions in arenavirus and coronavirus. Virologie (Montrouge) 2013; 17:317-330. [PMID: 31910588 DOI: 10.1684/vir.2013.0532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
RNA viruses encode dedicated protein machinery required through the viral life cycle. Some enzymatic activities are generally associated with RNA viruses such as RNA- or DNA-dependent RNA polymerases, RNA helicases or proteases. Some viral enzyme activities are however unique to some viral families. This is the case of two 3'-5' exoribonuclease activities identified in arenavirus and coronavirus proteomes. Arenaviruses have a segmented ambisense single stranded RNA genome of negative polarity while coronaviruses have a positive single-stranded genomic RNA. Although both enzymes belong to the same exo(ribo)nuclease superfamily, available data indicate that they are involved in very different pathways. Indeed, the exoribonuclease activity carried by the arenavirus nucleoprotein seems to counteract the innate immunity antiviral response while the exoribonuclease activity carried by the coronavirus nsp14 protein is likely involved in a unique RNA repair mechanism. In this review, we present our current knowledge about these two viral enzymes and their functions in the viral life cycle.
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Affiliation(s)
- Mickaël Bouvet
- UMR 7257 - CNRS et Aix-Marseille Université, laboratoire architecture et fonction des macromolécules biologiques (AFMB), ESIL Case 925, 13288 Marseille, France
| | - Isabelle Imbert
- UMR 7257 - CNRS et Aix-Marseille Université, laboratoire architecture et fonction des macromolécules biologiques (AFMB), ESIL Case 925, 13288 Marseille, France
| | - François Ferron
- UMR 7257 - CNRS et Aix-Marseille Université, laboratoire architecture et fonction des macromolécules biologiques (AFMB), ESIL Case 925, 13288 Marseille, France
| | - Bruno Canard
- UMR 7257 - CNRS et Aix-Marseille Université, laboratoire architecture et fonction des macromolécules biologiques (AFMB), ESIL Case 925, 13288 Marseille, France
| | - Etienne Decroly
- UMR 7257 - CNRS et Aix-Marseille Université, laboratoire architecture et fonction des macromolécules biologiques (AFMB), ESIL Case 925, 13288 Marseille, France
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43
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Jones CI, Grima DP, Waldron JA, Jones S, Parker HN, Newbury SF. The 5'-3' exoribonuclease Pacman (Xrn1) regulates expression of the heat shock protein Hsp67Bc and the microRNA miR-277-3p in Drosophila wing imaginal discs. RNA Biol 2013; 10:1345-55. [PMID: 23792537 PMCID: PMC3817156 DOI: 10.4161/rna.25354] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Pacman/Xrn1 is a highly conserved exoribonuclease known to play a critical role in gene regulatory events such as control of mRNA stability, RNA interference and regulation via miRNAs. Although Pacman has been well studied in Drosophila tissue culture cells, the biologically relevant cellular pathways controlled by Pacman in natural tissues are unknown. This study shows that a hypomorphic mutation in pacman (pcm5) results in smaller wing imaginal discs. These tissues, found in the larva, are known to grow and differentiate to form wing and thorax structures in the adult fly. Using microarray analysis, followed by quantitative RT-PCR, we show that eight mRNAs were increased in level by > 2-fold in the pcm5 mutant wing discs compared with the control. The levels of pre-mRNAs were tested for five of these mRNAs; four did not increase in the pcm5 mutant, showing that they are regulated at the post-transcriptional level and, therefore, could be directly affected by Pacman. These transcripts include one that encodes the heat shock protein Hsp67Bc, which is upregulated 11.9-fold at the post-transcriptional level and 2.3-fold at the protein level. One miRNA, miR-277-3p, is 5.6-fold downregulated at the post-transcriptional level in mutant discs, suggesting that Pacman affects its processing in this tissue. Together, these data show that a relatively small number of mRNAs and miRNAs substantially change in abundance in pacman mutant wing imaginal discs. Since Hsp67Bc is known to regulate autophagy and protein synthesis, it is possible that Pacman may control the growth of wing imaginal discs by regulating these processes.
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Affiliation(s)
- Christopher I Jones
- Brighton and Sussex Medical School; Medical Research Building; University of Sussex; Falmer, Brighton, UK
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Nagarajan VK, Jones CI, Newbury SF, Green PJ. XRN 5'→3' exoribonucleases: structure, mechanisms and functions. Biochim Biophys Acta 2013; 1829:590-603. [PMID: 23517755 PMCID: PMC3742305 DOI: 10.1016/j.bbagrm.2013.03.005] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Revised: 03/08/2013] [Accepted: 03/11/2013] [Indexed: 01/11/2023]
Abstract
The XRN family of 5'→3' exoribonucleases is critical for ensuring the fidelity of cellular RNA turnover in eukaryotes. Highly conserved across species, the family is typically represented by one cytoplasmic enzyme (XRN1/PACMAN or XRN4) and one or more nuclear enzymes (XRN2/RAT1 and XRN3). Cytoplasmic and/or nuclear XRNs have proven to be essential in all organisms tested, and deficiencies can have severe developmental phenotypes, demonstrating that XRNs are indispensable in fungi, plants and animals. XRNs degrade diverse RNA substrates during general RNA decay and function in specialized processes integral to RNA metabolism, such as nonsense-mediated decay (NMD), gene silencing, rRNA maturation, and transcription termination. Here, we review current knowledge of XRNs, highlighting recent work of high impact and future potential. One example is the breakthrough in our understanding of how XRN1 processively degrades 5' monophosphorylated RNA, revealed by its crystal structure and mutational analysis. The expanding knowledge of XRN substrates and interacting partners is outlined and the functions of XRNs are interpreted at the organismal level using available mutant phenotypes. Finally, three case studies are discussed in more detail to underscore a few of the most exciting areas of research on XRN function: XRN4 involvement in small RNA-associated processes in plants, the roles of XRN1/PACMAN in Drosophila development, and the function of human XRN2 in nuclear transcriptional quality control. This article is part of a Special Issue entitled: RNA Decay mechanisms.
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Affiliation(s)
- Vinay K. Nagarajan
- Delaware Biotechnology Institute, Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19711, USA
| | - Christopher I. Jones
- Medical Research Building, Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton BN1 9PS, UK
| | - Sarah F. Newbury
- Medical Research Building, Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton BN1 9PS, UK
| | - Pamela J. Green
- Delaware Biotechnology Institute, Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19711, USA
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45
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Abstract
The bacterial Hfq protein is a versatile modulator of RNA function and is particularly important for regulation mediated by small non-coding RNAs. Hfq is a bacterial Sm protein but bears more similarity to the eukaryotic Sm-like (Lsm) family of proteins than the prototypical Sm proteins. Hfq and Lsm proteins share the ability to chaperone RNA-RNA and RNA/protein interactions and an interesting penchant for protecting the 3′ end of a transcript from exonucleolytic decay while encouraging degradation through other pathways. Our view of Lsm function in eukaryotes has historically been informed by studies of Hfq structure and function but mutational analyses and structural studies of Lsm sub-complexes have given important insights as well. Here, we aim to compare and contrast the roles of these evolutionarily related complexes and to highlight areas for future investigation.
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Affiliation(s)
- Carol J Wilusz
- Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, CO, USA.
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Schmier BJ, Seetharaman J, Deutscher MP, Hunt JF, Malhotra A. The structure and enzymatic properties of a novel RNase II family enzyme from Deinococcus radiodurans. J Mol Biol 2012; 415:547-59. [PMID: 22133431 PMCID: PMC3269974 DOI: 10.1016/j.jmb.2011.11.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 11/14/2011] [Accepted: 11/16/2011] [Indexed: 01/07/2023]
Abstract
Exoribonucleases are vital in nearly all aspects of RNA metabolism, including RNA maturation, end-turnover, and degradation. RNase II and RNase R are paralogous members of the RNR superfamily of nonspecific, 3'→5', processive exoribonucleases. In Escherichia coli, RNase II plays a primary role in mRNA decay and has a preference for unstructured RNA. RNase R, in contrast, is capable of digesting structured RNA and plays a role in the degradation of both mRNA and stable RNA. Deinococcus radiodurans, a radiation-resistant bacterium, contains two RNR family members. The shorter of these, DrR63, includes a sequence signature typical of RNase R, but we show here that this enzyme is an RNase II-type exonuclease and cannot degrade structured RNA. We also report the crystal structure of this protein, now termed DrII. The DrII structure reveals a truncated RNA binding region in which the N-terminal cold shock domains, typical of most RNR family nucleases, are replaced by an unusual winged helix-turn-helix domain, where the "wing" is contributed by the C-terminal S1 domain. Consistent with its truncated RNA binding region, DrII is able to remove 3' overhangs from RNA molecules closer to duplexes than do other RNase II-type enzymes. DrII also displays distinct sensitivity to pyrimidine-rich regions of single-stranded RNA and is able to process tRNA precursors with adenosine-rich 3' extensions in vitro. These data indicate that DrII is the RNase II of D. radiodurans and that its structure and catalytic properties are distinct from those of other related enzymes.
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Affiliation(s)
- Brad J. Schmier
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, PO Box 016129, Miami, FL, 33101-6129, USA
| | - Jayaraman Seetharaman
- Northeast Structural Genomics Consortium (NESG) & Department of Biological Sciences, Columbia University, 1212 Amsterdam Avenue, New York, NY 10027
| | - Murray P. Deutscher
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, PO Box 016129, Miami, FL, 33101-6129, USA
| | - John F. Hunt
- Northeast Structural Genomics Consortium (NESG) & Department of Biological Sciences, Columbia University, 1212 Amsterdam Avenue, New York, NY 10027
| | - Arun Malhotra
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, PO Box 016129, Miami, FL, 33101-6129, USA
- Corresponding Author: Arun Malhotra: Ph: (305) 243-2826; Fax: (305) 243-3955;
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Christie M, Brosnan CA, Rothnagel JA, Carroll BJ. RNA decay and RNA silencing in plants: competition or collaboration? Front Plant Sci 2011; 2:99. [PMID: 22639621 PMCID: PMC3355627 DOI: 10.3389/fpls.2011.00099] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 11/30/2011] [Indexed: 05/25/2023]
Abstract
Initiation of RNA polymerase II transcription signals the beginning of a series of physically and functionally coupled pre-mRNA processing events that transform an RNA transcript into a highly structured, mature ribonucleoprotein complex. With such a complexity of co-transcriptional processes comes the need to identify and degrade improperly processed transcripts. Quality control of mRNA expression primarily involves exonucleolytic degradation of aberrant RNAs. RNA silencing, on the other hand, tends to be viewed separately as a pathway that primarily functions in regulating endogenous gene expression and in genome defense against transposons and viruses. Here, we review current knowledge of these pathways as they exist in plants and draw parallels to similar pathways in other eukaryotes. We then highlight some unexplored overlaps that exist between the RNA silencing and RNA decay pathways of plants, as evidenced by their shared RNA substrates and shared genetic requirements.
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Affiliation(s)
- Michael Christie
- School of Chemistry and Molecular Biosciences, The University of QueenslandBrisbane, QLD, Australia
| | - Christopher A. Brosnan
- School of Chemistry and Molecular Biosciences, The University of QueenslandBrisbane, QLD, Australia
| | - Joseph A. Rothnagel
- School of Chemistry and Molecular Biosciences, The University of QueenslandBrisbane, QLD, Australia
| | - Bernard J. Carroll
- School of Chemistry and Molecular Biosciences, The University of QueenslandBrisbane, QLD, Australia
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Sharwood RE, Halpert M, Luro S, Schuster G, Stern DB. Chloroplast RNase J compensates for inefficient transcription termination by removal of antisense RNA. RNA 2011; 17:2165-76. [PMID: 22033332 PMCID: PMC3222129 DOI: 10.1261/rna.028043.111] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 09/13/2011] [Indexed: 05/20/2023]
Abstract
Ribonuclease J is an essential enzyme, and the Bacillus subtilis ortholog possesses both endoribonuclease and 5' → 3' exoribonuclease activities. Chloroplasts also contain RNase J, which has been postulated to participate, as both an exo- and endonuclease, in the maturation of polycistronic mRNAs. Here we have examined recombinant Arabidopsis RNase J and found both 5' → 3' exoribonuclease and endonucleolytic activities. Virus-induced gene silencing was used to reduce RNase J expression in Arabidopsis and Nicotiana benthamiana, leading to chlorosis but surprisingly few disruptions in the cleavage of polycistronic rRNA and mRNA precursors. In contrast, antisense RNAs accumulated massively, suggesting that the failure of chloroplast RNA polymerase to terminate effectively leads to extensive symmetric transcription products that are normally eliminated by RNase J. Mung bean nuclease digestion and polysome analysis revealed that this antisense RNA forms duplexes with sense strand transcripts and prevents their translation. We conclude that a major role of chloroplast RNase J is RNA surveillance to prevent overaccumulation of antisense RNA, which would otherwise exert deleterious effects on chloroplast gene expression.
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Affiliation(s)
- Robert E. Sharwood
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA
| | - Michal Halpert
- Department of Biology, Technion–Israel Institute of Technology, Haifa 32000, Israel
| | - Scott Luro
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA
| | - Gadi Schuster
- Department of Biology, Technion–Israel Institute of Technology, Haifa 32000, Israel
| | - David B. Stern
- Boyce Thompson Institute for Plant Research, Ithaca, New York 14853, USA
- Corresponding author.E-mail .
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Hasenöhrl D, Konrat R, Bläsi U. Identification of an RNase J ortholog in Sulfolobus solfataricus: implications for 5'-to-3' directional decay and 5'-end protection of mRNA in Crenarchaeota. RNA 2011; 17:99-107. [PMID: 21115637 PMCID: PMC3004070 DOI: 10.1261/rna.2418211] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 10/07/2010] [Indexed: 05/29/2023]
Abstract
In both Bacteria and Eukaryotes, degradation is known to start at the 5' and at the 3' extremities of mRNAs. Until the recent discovery of 5'-to-3' exoribonucleases in hyperthermophilic Euryarchaeota, the exosome was assumed to be the key enzyme in mRNA degradation in Archaea. By means of zymogram assays and bioinformatics, we have identified a 5'-to-3' exoribonuclease activity in the crenarchaeum Sulfolobus solfataricus (Sso), which is affected by the phosphorylation state of the 5'-end of the mRNA. The protein comprises typical signature motifs of the β-CASP family of metallo-β-lactamases and was termed Sso-RNAse J. Thus, our study provides the first evidence for a 5'-to-3' directional mRNA decay pathway in the crenarchaeal clade of Archaea. In Bacteria the 5'-end of mRNAs is often protected by a tri-phosphorylated 5'-terminus and/or by stem-loop structures, while in Eukaryotes the cap-binding complex is responsible for this task. Here, we show that binding of translation initiation factor a/eIF2(γ) to the 5'-end of mRNA counteracts the 5'-to-3' exoribonucleolytic activity of Sso-RNase J in vitro. Hence, 5'-to-3' directional decay and 5'-end protection appear to be conserved features of mRNA turnover in all kingdoms of life.
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Affiliation(s)
- David Hasenöhrl
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, University of Vienna, 1030 Vienna, Austria
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Abstract
RNase R is an important exoribonuclease that participates in the degradation of structured RNAs in Escherichia coli. In earlier work, it was shown that RNase R levels increase dramatically under certain stress conditions, particularly during cold shock and stationary phase. However, the regulatory processes that lead to this elevation are not well understood. We show here that the increase in RNase R in stationary phase is unaffected by the global regulators, RpoS and (p)ppGpp, and that it occurs despite a major reduction in rnr message. Rather, we find that RNase R is a highly unstable protein in exponential phase, with a half-life of approximately 10 min, and that the protein is stabilized in stationary phase, leading to its relative increase. RNase R is also stabilized during cold shock and by growth in minimal medium, two other conditions that lead to its elevation. These data demonstrate that RNase R is subject to regulation by a novel, posttranslational mechanism that may have important implications for our complete understanding of RNA metabolism.
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Affiliation(s)
- Chenglu Chen
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, Florida 33101, USA
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