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Truchon AR, Chase EE, Gann ER, Moniruzzaman M, Creasey BA, Aylward FO, Xiao C, Gobler CJ, Wilhelm SW. Kratosvirus quantuckense: the history and novelty of an algal bloom disrupting virus and a model for giant virus research. Front Microbiol 2023; 14:1284617. [PMID: 38098665 PMCID: PMC10720644 DOI: 10.3389/fmicb.2023.1284617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 10/30/2023] [Indexed: 12/17/2023] Open
Abstract
Since the discovery of the first "giant virus," particular attention has been paid toward isolating and culturing these large DNA viruses through Acanthamoeba spp. bait systems. While this method has allowed for the discovery of plenty novel viruses in the Nucleocytoviricota, environmental -omics-based analyses have shown that there is a wealth of diversity among this phylum, particularly in marine datasets. The prevalence of these viruses in metatranscriptomes points toward their ecological importance in nutrient turnover in our oceans and as such, in depth study into non-amoebal Nucleocytoviricota should be considered a focal point in viral ecology. In this review, we report on Kratosvirus quantuckense (née Aureococcus anophagefferens Virus), an algae-infecting virus of the Imitervirales. Current systems for study in the Nucleocytoviricota differ significantly from this virus and its relatives, and a litany of trade-offs within physiology, coding potential, and ecology compared to these other viruses reveal the importance of K. quantuckense. Herein, we review the research that has been performed on this virus as well as its potential as a model system for algal-virus interactions.
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Affiliation(s)
- Alexander R Truchon
- Department of Microbiology, University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Emily E Chase
- Department of Microbiology, University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Eric R Gann
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, MD, United States
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
- Surgical Critical Care Initiative (SC2i), Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Mohammad Moniruzzaman
- Department of Marine Biology and Ecology, University of Miami, Miami, FL, United States
| | - Brooke A Creasey
- Department of Microbiology, University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Frank O Aylward
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - Chuan Xiao
- Department of Chemistry and Biochemistry, The University of Texas at El Paso, El Paso, TX, United States
| | | | - Steven W Wilhelm
- Department of Microbiology, University of Tennessee, Knoxville, Knoxville, TN, United States
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2
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Unconventional viral gene expression mechanisms as therapeutic targets. Nature 2021; 593:362-371. [PMID: 34012080 DOI: 10.1038/s41586-021-03511-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 03/22/2021] [Indexed: 12/14/2022]
Abstract
Unlike the human genome that comprises mostly noncoding and regulatory sequences, viruses have evolved under the constraints of maintaining a small genome size while expanding the efficiency of their coding and regulatory sequences. As a result, viruses use strategies of transcription and translation in which one or more of the steps in the conventional gene-protein production line are altered. These alternative strategies of viral gene expression (also known as gene recoding) can be uniquely brought about by dedicated viral enzymes or by co-opting host factors (known as host dependencies). Targeting these unique enzymatic activities and host factors exposes vulnerabilities of a virus and provides a paradigm for the design of novel antiviral therapies. In this Review, we describe the types and mechanisms of unconventional gene and protein expression in viruses, and provide a perspective on how future basic mechanistic work could inform translational efforts that are aimed at viral eradication.
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Kurilla A, Szőke A, Auber A, Káldi K, Silhavy D. Expression of the translation termination factor eRF1 is autoregulated by translational readthrough and 3'UTR intron-mediated NMD in Neurospora crassa. FEBS Lett 2020; 594:3504-3517. [PMID: 32869294 DOI: 10.1002/1873-3468.13918] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/30/2020] [Accepted: 08/17/2020] [Indexed: 01/24/2023]
Abstract
Eukaryotic release factor 1 (eRF1) is a translation termination factor that binds to the ribosome at stop codons. The expression of eRF1 is strictly controlled, since its concentration defines termination efficiency and frequency of translational readthrough. Here, we show that eRF1 expression in Neurospora crassa is controlled by an autoregulatory circuit that depends on the specific 3'UTR structure of erf1 mRNA. The stop codon context of erf1 promotes readthrough that protects the mRNA from its 3'UTR-induced nonsense-mediated mRNA decay (NMD). High eRF1 concentration leads to inefficient readthrough, thereby allowing NMD-mediated erf1 degradation. We propose that eRF1 expression is controlled by similar autoregulatory circuits in many fungi and seed plants and discuss the evolution of autoregulatory systems of different translation termination factors.
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Affiliation(s)
- Anita Kurilla
- Department of Genetics, NARIC, Agricultural Biotechnology Institute, Gödöllő, Hungary
| | - Anita Szőke
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Andor Auber
- Department of Genetics, NARIC, Agricultural Biotechnology Institute, Gödöllő, Hungary
| | - Krisztina Káldi
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Dániel Silhavy
- Department of Genetics, NARIC, Agricultural Biotechnology Institute, Gödöllő, Hungary.,Biological Research Centre, Institute of Plant Biology, Szeged, Hungary
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4
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Zinoviev A, Kuroha K, Pestova TV, Hellen CUT. Two classes of EF1-family translational GTPases encoded by giant viruses. Nucleic Acids Res 2019; 47:5761-5776. [PMID: 31216040 PMCID: PMC6582330 DOI: 10.1093/nar/gkz296] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 04/10/2019] [Accepted: 04/12/2019] [Indexed: 01/31/2023] Open
Abstract
Giant viruses have extraordinarily large dsDNA genomes, and exceptionally, they encode various components of the translation apparatus, including tRNAs, aminoacyl-tRNA synthetases and translation factors. Here, we focused on the elongation factor 1 (EF1) family of viral translational GTPases (trGTPases), using computational and functional approaches to shed light on their functions. Multiple sequence alignment indicated that these trGTPases clustered into two groups epitomized by members of Mimiviridae and Marseilleviridae, respectively. trGTPases in the first group were more closely related to GTP-binding protein 1 (GTPBP1), whereas trGTPases in the second group were closer to eEF1A, eRF3 and Hbs1. Functional characterization of representative GTPBP1-like trGTPases (encoded by Hirudovirus, Catovirus and Moumouvirus) using in vitro reconstitution revealed that they possess eEF1A-like activity and can deliver cognate aa-tRNAs to the ribosomal A site during translation elongation. By contrast, representative eEF1A/eRF3/Hbs1-like viral trGTPases, encoded by Marseillevirus and Lausannevirus, have eRF3-like termination activity and stimulate peptide release by eRF1. Our analysis identified specific aspects of the functioning of these viral trGTPases with eRF1 of human, amoebal and Marseillevirus origin.
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Affiliation(s)
- Alexandra Zinoviev
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC 44, Brooklyn, NY 11203, USA
| | - Kazushige Kuroha
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC 44, Brooklyn, NY 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC 44, Brooklyn, NY 11203, USA
| | - Christopher U T Hellen
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, MSC 44, Brooklyn, NY 11203, USA
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5
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Stern-Ginossar N, Thompson SR, Mathews MB, Mohr I. Translational Control in Virus-Infected Cells. Cold Spring Harb Perspect Biol 2019; 11:a033001. [PMID: 29891561 PMCID: PMC6396331 DOI: 10.1101/cshperspect.a033001] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
As obligate intracellular parasites, virus reproduction requires host cell functions. Despite variations in genome size and configuration, nucleic acid composition, and their repertoire of encoded functions, all viruses remain unconditionally dependent on the protein synthesis machinery resident within their cellular hosts to translate viral messenger RNAs (mRNAs). A complex signaling network responsive to physiological stress, including infection, regulates host translation factors and ribosome availability. Furthermore, access to the translation apparatus is patrolled by powerful host immune defenses programmed to restrict viral invaders. Here, we review the tactics and mechanisms used by viruses to appropriate control over host ribosomes, subvert host defenses, and dominate the infected cell translational landscape. These not only define aspects of infection biology paramount for virus reproduction, but continue to drive fundamental discoveries into how cellular protein synthesis is controlled in health and disease.
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Affiliation(s)
- Noam Stern-Ginossar
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sunnie R Thompson
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Michael B Mathews
- Department of Medicine, Rutgers New Jersey Medical School, Newark, New Jersey 07103
| | - Ian Mohr
- Department of Microbiology, New York University School of Medicine, New York, New York 10016
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Experimental Analysis of Mimivirus Translation Initiation Factor 4a Reveals Its Importance in Viral Protein Translation during Infection of Acanthamoeba polyphaga. J Virol 2018. [PMID: 29514904 DOI: 10.1128/jvi.00337-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The Acanthamoeba polyphaga mimivirus is the first giant virus ever described, with a 1.2-Mb genome which encodes 979 proteins, including central components of the translation apparatus. One of these proteins, R458, was predicted to initiate translation, although its specific role remains unknown. We silenced the R458 gene using small interfering RNA (siRNA) and compared levels of viral fitness and protein expression in silenced versus wild-type mimivirus. Silencing decreased the growth rate, but viral particle production at the end of the viral cycle was unaffected. A comparative proteomic approach using two-dimensional difference-in-gel electrophoresis (2D-DIGE) revealed deregulation of the expression of 32 proteins in silenced mimivirus, which were defined as up- or downregulated. Besides revealing proteins with unknown functions, silencing R458 also revealed deregulation in proteins associated with viral particle structures, transcriptional machinery, oxidative pathways, modification of proteins/lipids, and DNA topology/repair. Most of these proteins belong to genes transcribed at the end of the viral cycle. Overall, our data suggest that the R458 protein regulates the expression of mimivirus proteins and, thus, that mimivirus translational proteins may not be strictly redundant in relation to those from the amoeba host. As is the case for eukaryotic initiation factor 4a (eIF4a), the R458 protein is the prototypical member of the ATP-dependent DEAD box RNA helicase mechanism. We suggest that the R458 protein is required to unwind the secondary structures at the 5' ends of mRNAs and to bind the mRNA to the ribosome, making it possible to scan for the start codon. These data are the first experimental evidence of mimivirus translation-related genes, predicted to initiate protein biosynthesis.IMPORTANCE The presence in the genome of a mimivirus of genes coding for many translational processes, with the exception of ribosome constituents, has been the subject of debate since its discovery in 2003. In this work, we focused on the R458 mimivirus gene, predicted to initiate protein biosynthesis. After silencing was performed, we observed that it has no major effect on mimivirus multiplication but that it affects protein expression and fitness. This suggests that it is effectively used by mimivirus during its developmental cycle. Until large-scale genetic manipulation of giant viruses becomes possible, the silencing strategy used here on mimivirus translation-related factors will open the way to understanding the functions of these translational genes.
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7
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Seligmann H, Raoult D. Stem-Loop RNA Hairpins in Giant Viruses: Invading rRNA-Like Repeats and a Template Free RNA. Front Microbiol 2018; 9:101. [PMID: 29449833 PMCID: PMC5799277 DOI: 10.3389/fmicb.2018.00101] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 01/16/2018] [Indexed: 12/31/2022] Open
Abstract
We examine the hypothesis that de novo template-free RNAs still form spontaneously, as they did at the origins of life, invade modern genomes, contribute new genetic material. Previously, analyses of RNA secondary structures suggested that some RNAs resembling ancestral (t)RNAs formed recently de novo, other parasitic sequences cluster with rRNAs. Here positive control analyses of additional RNA secondary structures confirm ancestral and de novo statuses of RNA grouped according to secondary structure. Viroids with branched stems resemble de novo RNAs, rod-shaped viroids resemble rRNA secondary structures, independently of GC contents. 5' UTR leading regions of West Nile and Dengue flavivirid viruses resemble de novo and rRNA structures, respectively. An RNA homologous with Megavirus, Dengue and West Nile genomes, copperhead snake microsatellites and levant cotton repeats, not templated by Mimivirus' genome, persists throughout Mimivirus' infection. Its secondary structure clusters with candidate de novo RNAs. The saltatory phyletic distribution and secondary structure of Mimivirus' peculiar RNA suggest occasional template-free polymerization of this sequence, rather than noncanonical transcriptions (swinger polymerization, posttranscriptional editing).
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Affiliation(s)
- Hervé Seligmann
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UMR MEPHI, Aix-Marseille Université, IRD, Assistance Publique-Hôpitaux de Marseille, Institut Hospitalo-Universitaire Méditerranée-Infection, Marseille, France
| | - Didier Raoult
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UMR MEPHI, Aix-Marseille Université, IRD, Assistance Publique-Hôpitaux de Marseille, Institut Hospitalo-Universitaire Méditerranée-Infection, Marseille, France
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8
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Loughran G, Jungreis I, Tzani I, Power M, Dmitriev RI, Ivanov IP, Kellis M, Atkins JF. Stop codon readthrough generates a C-terminally extended variant of the human vitamin D receptor with reduced calcitriol response. J Biol Chem 2018; 293:4434-4444. [PMID: 29386352 PMCID: PMC5868278 DOI: 10.1074/jbc.m117.818526] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 01/30/2018] [Indexed: 12/25/2022] Open
Abstract
Although stop codon readthrough is used extensively by viruses to expand their gene expression, verified instances of mammalian readthrough have only recently been uncovered by systems biology and comparative genomics approaches. Previously, our analysis of conserved protein coding signatures that extend beyond annotated stop codons predicted stop codon readthrough of several mammalian genes, all of which have been validated experimentally. Four mRNAs display highly efficient stop codon readthrough, and these mRNAs have a UGA stop codon immediately followed by CUAG (UGA_CUAG) that is conserved throughout vertebrates. Extending on the identification of this readthrough motif, we here investigated stop codon readthrough, using tissue culture reporter assays, for all previously untested human genes containing UGA_CUAG. The readthrough efficiency of the annotated stop codon for the sequence encoding vitamin D receptor (VDR) was 6.7%. It was the highest of those tested but all showed notable levels of readthrough. The VDR is a member of the nuclear receptor superfamily of ligand-inducible transcription factors, and it binds its major ligand, calcitriol, via its C-terminal ligand-binding domain. Readthrough of the annotated VDR mRNA results in a 67 amino acid-long C-terminal extension that generates a VDR proteoform named VDRx. VDRx may form homodimers and heterodimers with VDR but, compared with VDR, VDRx displayed a reduced transcriptional response to calcitriol even in the presence of its partner retinoid X receptor.
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Affiliation(s)
- Gary Loughran
- From the School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland,
| | - Irwin Jungreis
- Computer Science and Artificial Intelligence Laboratory (CSAIL), Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, and
| | - Ioanna Tzani
- From the School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Michael Power
- From the School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Ruslan I Dmitriev
- From the School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Ivaylo P Ivanov
- From the School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Manolis Kellis
- Computer Science and Artificial Intelligence Laboratory (CSAIL), Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, and
| | - John F Atkins
- From the School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland, .,Department of Human Genetics, University of Utah, Salt Lake City, Utah 84112-5330
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9
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Shukla A, Chatterjee A, Kondabagil K. The number of genes encoding repeat domain-containing proteins positively correlates with genome size in amoebal giant viruses. Virus Evol 2018; 4:vex039. [PMID: 29308275 PMCID: PMC5753266 DOI: 10.1093/ve/vex039] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Curiously, in viruses, the virion volume appears to be predominantly driven by genome length rather than the number of proteins it encodes or geometric constraints. With their large genome and giant particle size, amoebal viruses (AVs) are ideally suited to study the relationship between genome and virion size and explore the role of genome plasticity in their evolutionary success. Different genomic regions of AVs exhibit distinct genealogies. Although the vertically transferred core genes and their functions are universally conserved across the nucleocytoplasmic large DNA virus (NCLDV) families and are essential for their replication, the horizontally acquired genes are variable across families and are lineage-specific. When compared with other giant virus families, we observed a near–linear increase in the number of genes encoding repeat domain-containing proteins (RDCPs) with the increase in the genome size of AVs. From what is known about the functions of RDCPs in bacteria and eukaryotes and their prevalence in the AV genomes, we envisage important roles for RDCPs in the life cycle of AVs, their genome expansion, and plasticity. This observation also supports the evolution of AVs from a smaller viral ancestor by the acquisition of diverse gene families from the environment including RDCPs that might have helped in host adaption.
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Affiliation(s)
- Avi Shukla
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
| | - Anirvan Chatterjee
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
| | - Kiran Kondabagil
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
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10
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Nyikó T, Auber A, Szabadkai L, Benkovics A, Auth M, Mérai Z, Kerényi Z, Dinnyés A, Nagy F, Silhavy D. Expression of the eRF1 translation termination factor is controlled by an autoregulatory circuit involving readthrough and nonsense-mediated decay in plants. Nucleic Acids Res 2017; 45:4174-4188. [PMID: 28062855 PMCID: PMC5397192 DOI: 10.1093/nar/gkw1303] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/24/2016] [Accepted: 12/28/2016] [Indexed: 12/28/2022] Open
Abstract
When a ribosome reaches a stop codon, the eukaryotic Release Factor 1 (eRF1) binds to the A site of the ribosome and terminates translation. In yeasts and plants, both over- and underexpression of eRF1 lead to altered phenotype indicating that eRF1 expression should be strictly controlled. However, regulation of eRF1 level is still poorly understood. Here we show that expression of plant eRF1 is controlled by a complex negative autoregulatory circuit, which is based on the unique features of the 3΄untranslated region (3΄UTR) of the eRF1-1 transcript. The stop codon of the eRF1-1 mRNA is in a translational readthrough promoting context, while its 3΄UTR induces nonsense-mediated decay (NMD), a translation termination coupled mRNA degradation mechanism. We demonstrate that readthrough partially protects the eRF1-1 mRNA from its 3΄UTR induced NMD, and that elevated eRF1 levels inhibit readthrough and stimulate NMD. Thus, high eRF1 level leads to reduced eRF1-1 expression, as weakened readthrough fails to protect the eRF1-1 mRNA from the more intense NMD. This eRF1 autoregulatory circuit might serve to finely balance general translation termination efficiency.
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Affiliation(s)
- Tünde Nyikó
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
| | - Andor Auber
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
| | - Levente Szabadkai
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
| | - Anna Benkovics
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
| | - Mariann Auth
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
| | - Zsuzsanna Mérai
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
| | - Zoltán Kerényi
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
| | - Andrea Dinnyés
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
| | - Ferenc Nagy
- Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Temesvári 62, H-6726, Hungary
| | - Dániel Silhavy
- Department of Genetics, Agricultural Biotechnology Institute, Gödöllő, Szent-Györgyi 4, H-2100, Hungary
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Colson P, La Scola B, Levasseur A, Caetano-Anollés G, Raoult D. Mimivirus: leading the way in the discovery of giant viruses of amoebae. Nat Rev Microbiol 2017; 15:243-254. [PMID: 28239153 PMCID: PMC7096837 DOI: 10.1038/nrmicro.2016.197] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Acanthamoeba polyphaga mimivirus (APMV) and subsequently discovered giant viruses of amoebae challenge the previous definition of viruses and their classification. The replication cycle, structure, genomic make-up and plasticity of giant viruses differ from those of traditional viruses. They extend the definition of viruses into a broader range of biological entities, some of which are very simple and others of which have a complexity that is comparable to that of other microorganisms. Giant viruses of amoebae have virus particles as large as some microorganisms that are visible by light microscopy and that have a stunning level of complexity. Their genomes are mosaics and contain large repertoires of genes, some of which are hallmarks of cellular organisms, although the majority of which have unknown functions. Mimiviruses are associated with a specific mobilome and are parasitized by viruses that they can defend against. Several hypotheses on the ancient origin and evolutionary relationship between cellular organisms and giant viruses of amoebae have been proposed, and these topics continue to be debated. The detection of giant viruses of amoebae in humans and the study of their potential pathogenicity are emerging fields.
The discovery of the giant amoebal virus mimivirus, in 2003, opened up a new area of virology. Extended studies, including those of mimiviruses, have since revealed that these viruses have genetic, proteomic and structural features that are more complex than those of conventional viruses. The accidental discovery of the giant virus of amoeba — Acanthamoeba polyphaga mimivirus (APMV; more commonly known as mimivirus) — in 2003 changed the field of virology. Viruses were previously defined by their submicroscopic size, which probably prevented the search for giant viruses, which are visible by light microscopy. Extended studies of giant viruses of amoebae revealed that they have genetic, proteomic and structural complexities that were not thought to exist among viruses and that are comparable to those of bacteria, archaea and small eukaryotes. The giant virus particles contain mRNA and more than 100 proteins, they have gene repertoires that are broader than those of other viruses and, notably, some encode translation components. The infection cycles of giant viruses of amoebae involve virus entry by amoebal phagocytosis and replication in viral factories. In addition, mimiviruses are infected by virophages, defend against them through the mimivirus virophage resistance element (MIMIVIRE) system and have a unique mobilome. Overall, giant viruses of amoebae, including mimiviruses, marseilleviruses, pandoraviruses, pithoviruses, faustoviruses and molliviruses, challenge the definition and classification of viruses, and have increasingly been detected in humans.
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Affiliation(s)
- Philippe Colson
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), Aix-Marseille University, UM63, CNRS 7278, IRD 198, INSERM 1095, Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille, France
| | - Bernard La Scola
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), Aix-Marseille University, UM63, CNRS 7278, IRD 198, INSERM 1095, Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille, France
| | - Anthony Levasseur
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), Aix-Marseille University, UM63, CNRS 7278, IRD 198, INSERM 1095, Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille, France
| | - Gustavo Caetano-Anollés
- Evolutionary Bioinformatics Laboratory, Department of Crop Sciences, University of Illinois, 332 National Soybean Research Center, 1101 West Peabody Drive, Urbana, Illinois 61801, USA
| | - Didier Raoult
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), Aix-Marseille University, UM63, CNRS 7278, IRD 198, INSERM 1095, Institut Hospitalo-Universitaire (IHU) - Méditerranée Infection, AP-HM, 19-21 Boulevard Jean Moulin, 13385 Marseille, France
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12
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Abrahão JS, Araújo R, Colson P, La Scola B. The analysis of translation-related gene set boosts debates around origin and evolution of mimiviruses. PLoS Genet 2017; 13:e1006532. [PMID: 28207761 PMCID: PMC5313130 DOI: 10.1371/journal.pgen.1006532] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The giant mimiviruses challenged the well-established concept of viruses, blurring the roots of the tree of life, mainly due to their genetic content. Along with other nucleo-cytoplasmic large DNA viruses, they compose a new proposed order-named Megavirales-whose origin and evolution generate heated debate in the scientific community. The presence of an arsenal of genes not widespread in the virosphere related to important steps of the translational process, including transfer RNAs, aminoacyl-tRNA synthetases, and translation factors for peptide synthesis, constitutes an important element of this debate. In this review, we highlight the main findings to date about the translational machinery of the mimiviruses and compare their distribution along the distinct members of the family Mimiviridae. Furthermore, we discuss how the presence and/or absence of the translation-related genes among mimiviruses raises important insights to boost the debate on their origin and evolutionary history.
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Affiliation(s)
- Jônatas Santos Abrahão
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE) UM63 CNRS 7278 IRD 198 INSERM U1095, Aix-Marseille Univ., 27 boulevard Jean Moulin, Faculté de Médecine, Marseille, France.,Instituto de Ciências Biológicas, Departamento de Microbiologia, Laboratório de Vírus, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Rodrigo Araújo
- Instituto de Ciências Biológicas, Departamento de Microbiologia, Laboratório de Vírus, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Philippe Colson
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE) UM63 CNRS 7278 IRD 198 INSERM U1095, Aix-Marseille Univ., 27 boulevard Jean Moulin, Faculté de Médecine, Marseille, France
| | - Bernard La Scola
- Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE) UM63 CNRS 7278 IRD 198 INSERM U1095, Aix-Marseille Univ., 27 boulevard Jean Moulin, Faculté de Médecine, Marseille, France
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13
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Abstract
Translational readthrough (TR) has come into renewed focus because systems biology approaches have identified the first human genes undergoing functional translational readthrough (FTR). FTR creates functional extensions to proteins by continuing translation of the mRNA downstream of the stop codon. Here we review recent developments in TR research with a focus on the identification of FTR in humans and the systems biology methods that have spurred these discoveries.
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Affiliation(s)
- Fabian Schueren
- University Medical Center, Department of Child and Adolescent Health, University of Göttingen, Göttingen, Germany
| | - Sven Thoms
- University Medical Center, Department of Child and Adolescent Health, University of Göttingen, Göttingen, Germany
- * E-mail:
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14
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Jan E, Mohr I, Walsh D. A Cap-to-Tail Guide to mRNA Translation Strategies in Virus-Infected Cells. Annu Rev Virol 2016; 3:283-307. [PMID: 27501262 DOI: 10.1146/annurev-virology-100114-055014] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although viruses require cellular functions to replicate, their absolute dependence upon the host translation machinery to produce polypeptides indispensable for their reproduction is most conspicuous. Despite their incredible diversity, the mRNAs produced by all viruses must engage cellular ribosomes. This has proven to be anything but a passive process and has revealed a remarkable array of tactics for rapidly subverting control over and dominating cellular regulatory pathways that influence translation initiation, elongation, and termination. Besides enforcing viral mRNA translation, these processes profoundly impact host cell-intrinsic immune defenses at the ready to deny foreign mRNA access to ribosomes and block protein synthesis. Finally, genome size constraints have driven the evolution of resourceful strategies for maximizing viral coding capacity. Here, we review the amazing strategies that work to regulate translation in virus-infected cells, highlighting both virus-specific tactics and the tremendous insight they provide into fundamental translational control mechanisms in health and disease.
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Affiliation(s)
- Eric Jan
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada;
| | - Ian Mohr
- Department of Microbiology and New York University Cancer Institute, New York University School of Medicine, New York, NY 10016;
| | - Derek Walsh
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611;
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15
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Atkins JF, Loughran G, Bhatt PR, Firth AE, Baranov PV. Ribosomal frameshifting and transcriptional slippage: From genetic steganography and cryptography to adventitious use. Nucleic Acids Res 2016; 44:7007-78. [PMID: 27436286 PMCID: PMC5009743 DOI: 10.1093/nar/gkw530] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/26/2016] [Indexed: 12/15/2022] Open
Abstract
Genetic decoding is not ‘frozen’ as was earlier thought, but dynamic. One facet of this is frameshifting that often results in synthesis of a C-terminal region encoded by a new frame. Ribosomal frameshifting is utilized for the synthesis of additional products, for regulatory purposes and for translational ‘correction’ of problem or ‘savior’ indels. Utilization for synthesis of additional products occurs prominently in the decoding of mobile chromosomal element and viral genomes. One class of regulatory frameshifting of stable chromosomal genes governs cellular polyamine levels from yeasts to humans. In many cases of productively utilized frameshifting, the proportion of ribosomes that frameshift at a shift-prone site is enhanced by specific nascent peptide or mRNA context features. Such mRNA signals, which can be 5′ or 3′ of the shift site or both, can act by pairing with ribosomal RNA or as stem loops or pseudoknots even with one component being 4 kb 3′ from the shift site. Transcriptional realignment at slippage-prone sequences also generates productively utilized products encoded trans-frame with respect to the genomic sequence. This too can be enhanced by nucleic acid structure. Together with dynamic codon redefinition, frameshifting is one of the forms of recoding that enriches gene expression.
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Affiliation(s)
- John F Atkins
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland School of Microbiology, University College Cork, Cork, Ireland Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Gary Loughran
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Pramod R Bhatt
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Andrew E Firth
- Division of Virology, Department of Pathology, University of Cambridge, Hills Road, Cambridge CB2 0QQ, UK
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
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16
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Kumar S, Kumari R, Sharma V. Coevolution mechanisms that adapt viruses to genetic code variations implemented in their hosts. J Genet 2016; 95:3-12. [PMID: 27019427 DOI: 10.1007/s12041-016-0612-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sushil Kumar
- SKA Institution for Research, Education and Development, 4/11 SarvPriya Vihar, New Delhi 110016, India.
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17
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Abergel C, Legendre M, Claverie JM. The rapidly expanding universe of giant viruses: Mimivirus, Pandoravirus, Pithovirus and Mollivirus. FEMS Microbiol Rev 2015; 39:779-96. [PMID: 26391910 DOI: 10.1093/femsre/fuv037] [Citation(s) in RCA: 158] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2015] [Indexed: 12/31/2022] Open
Abstract
More than a century ago, the term 'virus' was introduced to describe infectious agents that are invisible by light microscopy and capable of passing through sterilizing filters. In addition to their extremely small size, most viruses have minimal genomes and gene contents, and rely almost entirely on host cell-encoded functions to multiply. Unexpectedly, four different families of eukaryotic 'giant viruses' have been discovered over the past 10 years with genome sizes, gene contents and particle dimensions overlapping with that of cellular microbes. Their ongoing analyses are challenging accepted ideas about the diversity, evolution and origin of DNA viruses.
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Affiliation(s)
- Chantal Abergel
- Structural and Genomic Information Laboratory, UMR 7256 (IMM FR 3479) Centre National de la Recherche Scientifique & Aix-Marseille University, 13288 Marseille, France
| | - Matthieu Legendre
- Structural and Genomic Information Laboratory, UMR 7256 (IMM FR 3479) Centre National de la Recherche Scientifique & Aix-Marseille University, 13288 Marseille, France
| | - Jean-Michel Claverie
- Structural and Genomic Information Laboratory, UMR 7256 (IMM FR 3479) Centre National de la Recherche Scientifique & Aix-Marseille University, 13288 Marseille, France Assistance Publique des Hôpitaux de Marseille, La Timone, 13005 Marseille, France
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18
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Silva LCF, Almeida GMF, Assis FL, Albarnaz JD, Boratto PVM, Dornas FP, Andrade KR, La Scola B, Kroon EG, da Fonseca FG, Abrahão JS. Modulation of the expression of mimivirus-encoded translation-related genes in response to nutrient availability during Acanthamoeba castellanii infection. Front Microbiol 2015; 6:539. [PMID: 26082761 PMCID: PMC4450173 DOI: 10.3389/fmicb.2015.00539] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 05/15/2015] [Indexed: 11/27/2022] Open
Abstract
The complexity of giant virus genomes is intriguing, especially the presence of genes encoding components of the protein translation machinery such as transfer RNAs and aminoacyl-tRNA-synthetases; these features are uncommon among other viruses. Although orthologs of these genes are codified by their hosts, one can hypothesize that having these translation-related genes might represent a gain of fitness during infection. Therefore, the aim of this study was to evaluate the expression of translation-related genes by mimivirus during infection of Acanthamoeba castellanii under different nutritional conditions. In silico analysis of amino acid usage revealed remarkable differences between the mimivirus isolates and the A. castellanii host. Relative expression analysis by quantitative PCR revealed that mimivirus was able to modulate the expression of eight viral translation-related genes according to the amoebal growth condition, with a higher induction of gene expression under starvation. Some mimivirus isolates presented differences in translation-related gene expression; notably, polymorphisms in the promoter regions correlated with these differences. Two mimivirus isolates did not encode the tryptophanyl-tRNA in their genomes, which may be linked with low conservation pressure based on amino acid usage analysis. Taken together, our data suggest that mimivirus can modulate the expression of translation-related genes in response to nutrient availability in the host cell, allowing the mimivirus to adapt to different hosts growing under different nutritional conditions.
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Affiliation(s)
- Lorena C F Silva
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Gabriel M F Almeida
- AQUACEN - Laboratório Nacional de Referencia para Doenças de Animais Aquáticos, Ministério da Pesca e Aquicultura, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Felipe L Assis
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Jonas D Albarnaz
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Paulo V M Boratto
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Fábio P Dornas
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Ketyllen R Andrade
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Bernard La Scola
- URMITE CNRS UMR 6236 - IRD 3R198, Aix Marseille Université Marseille, France
| | - Erna G Kroon
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Flávio G da Fonseca
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil ; Laboratório de Virologia Básica e Aplicada, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
| | - Jônatas S Abrahão
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais Belo Horizonte, Brazil
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19
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Abstract
Ribosome profiling is an emerging technique that uses deep sequencing to monitor translation in live cells. Studies using ribosome profiling have already provided novel insights into the identities and amounts of the proteins being produced in cells, as well as novel insights into the mechanism of protein synthesis and translation regulation. Application of ribosome profiling to cells infected with human cytomegalovirus and Kaposi's sarcoma-associated herpesvirus revealed unanticipated complexity in the coding capacity of herpesviruses. Here, I discuss these results and how the application of ribosome profiling to cells infected with other viruses can reveal novel insights into the process of infection.
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20
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Molecular Biosafety. APPLIED BIOSAFETY 2014. [DOI: 10.1177/153567601401900406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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21
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The megavirus chilensis Cu,Zn-superoxide dismutase: the first viral structure of a typical cellular copper chaperone-independent hyperstable dimeric enzyme. J Virol 2014; 89:824-32. [PMID: 25355875 DOI: 10.1128/jvi.02588-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Giant viruses able to replicate in Acanthamoeba castellanii penetrate their host through phagocytosis. After capsid opening, a fusion between the internal membranes of the virion and the phagocytic vacuole triggers the transfer in the cytoplasm of the viral DNA together with the DNA repair enzymes and the transcription machinery present in the particles. In addition, the proteome analysis of purified mimivirus virions revealed the presence of many enzymes meant to resist oxidative stress and conserved in the Mimiviridae. Megavirus chilensis encodes a predicted copper, zinc superoxide dismutase (Cu,Zn-SOD), an enzyme known to detoxify reactive oxygen species released in the course of host defense reactions. While it was thought that the metal ions are required for the formation of the active-site lid and dimer stabilization, megavirus chilensis SOD forms a very stable metal-free dimer. We used electron paramagnetic resonance (EPR) analysis and activity measurements to show that the supplementation of the bacterial culture with copper and zinc during the recombinant expression of Mg277 is sufficient to restore a fully active holoenzyme. These results demonstrate that the viral enzyme's activation is independent of a chaperone both for disulfide bridge formation and for copper incorporation and suggest that its assembly may not be as regulated as that of its cellular counterparts. A SOD protein is encoded by a variety of DNA viruses but is absent from mimivirus. As in poxviruses, the enzyme might be dispensable when the virus infects Acanthamoeba cells but may allow megavirus chilensis to infect a broad range of eukaryotic hosts. IMPORTANCE Mimiviridae are giant viruses encoding more than 1,000 proteins. The virion particles are loaded with proteins used by the virus to resist the vacuole's oxidative stress. The megavirus chilensis virion contains a predicted copper, zinc superoxide dismutase (Cu,Zn-SOD). The corresponding gene is present in some megavirus chilensis relatives but is absent from mimivirus. This first crystallographic structure of a viral Cu,Zn-SOD highlights the features that it has in common with and its differences from cellular SODs. It corresponds to a very stable dimer of the apo form of the enzyme. We demonstrate that upon supplementation of the growth medium with Cu and Zn, the recombinant protein is fully active, suggesting that the virus's SOD activation is independent of a copper chaperone for SOD generally used by eukaryotic SODs.
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22
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Loughran G, Chou MY, Ivanov IP, Jungreis I, Kellis M, Kiran AM, Baranov PV, Atkins JF. Evidence of efficient stop codon readthrough in four mammalian genes. Nucleic Acids Res 2014; 42:8928-38. [PMID: 25013167 PMCID: PMC4132726 DOI: 10.1093/nar/gku608] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 05/31/2014] [Accepted: 06/24/2014] [Indexed: 12/04/2022] Open
Abstract
Stop codon readthrough is used extensively by viruses to expand their gene expression. Until recent discoveries in Drosophila, only a very limited number of readthrough cases in chromosomal genes had been reported. Analysis of conserved protein coding signatures that extend beyond annotated stop codons identified potential stop codon readthrough of four mammalian genes. Here we use a modified targeted bioinformatic approach to identify a further three mammalian readthrough candidates. All seven genes were tested experimentally using reporter constructs transfected into HEK-293T cells. Four displayed efficient stop codon readthrough, and these have UGA immediately followed by CUAG. Comparative genomic analysis revealed that in the four readthrough candidates containing UGA-CUAG, this motif is conserved not only in mammals but throughout vertebrates with the first six of the seven nucleotides being universally conserved. The importance of the CUAG motif was confirmed using a systematic mutagenesis approach. One gene, OPRL1, encoding an opiate receptor, displayed extremely efficient levels of readthrough (∼31%) in HEK-293T cells. Signals both 5' and 3' of the OPRL1 stop codon contribute to this high level of readthrough. The sequence UGA-CUA alone can support 1.5% readthrough, underlying its importance.
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Affiliation(s)
- Gary Loughran
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Ming-Yuan Chou
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Ivaylo P Ivanov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Irwin Jungreis
- CSAIL, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
| | - Manolis Kellis
- CSAIL, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
| | - Anmol M Kiran
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - John F Atkins
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland Department of Human Genetics, University of Utah, Salt Lake City, UT 84112-5330, USA
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23
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Philippe N, Legendre M, Doutre G, Couté Y, Poirot O, Lescot M, Arslan D, Seltzer V, Bertaux L, Bruley C, Garin J, Claverie JM, Abergel C. Pandoraviruses: amoeba viruses with genomes up to 2.5 Mb reaching that of parasitic eukaryotes. Science 2013; 341:281-6. [PMID: 23869018 DOI: 10.1126/science.1239181] [Citation(s) in RCA: 393] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ten years ago, the discovery of Mimivirus, a virus infecting Acanthamoeba, initiated a reappraisal of the upper limits of the viral world, both in terms of particle size (>0.7 micrometers) and genome complexity (>1000 genes), dimensions typical of parasitic bacteria. The diversity of these giant viruses (the Megaviridae) was assessed by sampling a variety of aquatic environments and their associated sediments worldwide. We report the isolation of two giant viruses, one off the coast of central Chile, the other from a freshwater pond near Melbourne (Australia), without morphological or genomic resemblance to any previously defined virus families. Their micrometer-sized ovoid particles contain DNA genomes of at least 2.5 and 1.9 megabases, respectively. These viruses are the first members of the proposed "Pandoravirus" genus, a term reflecting their lack of similarity with previously described microorganisms and the surprises expected from their future study.
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Affiliation(s)
- Nadège Philippe
- Structural and Genomic Information Laboratory, UMR 7256 CNRS Aix-Marseille Université, 163 Avenue de Luminy, Case 934, 13288 Marseille cedex 9, France
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