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Lavezzari D, Mori A, Pomari E, Deiana M, Fadda A, Bertoli L, Sinigaglia A, Riccetti S, Barzon L, Piubelli C, Delledonne M, Capobianchi MR, Castilletti C. Comparative analysis of bioinformatics tools to characterize SARS-CoV-2 subgenomic RNAs. Life Sci Alliance 2023; 6:e202302017. [PMID: 37748810 PMCID: PMC10520259 DOI: 10.26508/lsa.202302017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 09/27/2023] Open
Abstract
During the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), positive-sense genomic RNA and subgenomic RNAs (sgRNAs) are synthesized by a discontinuous process of transcription characterized by a template switch, regulated by transcription-regulating sequences (TRS). Although poorly known about makeup and dynamics of sgRNAs population and function of its constituents, next-generation sequencing approaches with the help of bioinformatics tools have made a significant contribution to expand the knowledge of sgRNAs in SARS-CoV-2. For this scope to date, Periscope, LeTRS, sgDI-tector, and CORONATATOR have been developed. However, limited number of studies are available to compare the performance of such tools. To this purpose, we compared Periscope, LeTRS, and sgDI-tector in the identification of canonical (c-) and noncanonical (nc-) sgRNA species in the data obtained with the Illumina ARTIC sequencing protocol applied to SARS-CoV-2-infected Caco-2 cells, sampled at different time points. The three software showed a high concordance rate in the identification and in the quantification of c-sgRNA, whereas more differences were observed in nc-sgRNA. Overall, LeTRS and sgDI-tector result to be adequate alternatives to Periscope to analyze Fastq data from sequencing platforms other than Nanopore.
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Affiliation(s)
- Denise Lavezzari
- Department of Infectious and Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Verona, Italy
| | - Antonio Mori
- Department of Infectious and Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Verona, Italy
| | - Elena Pomari
- Department of Infectious and Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Verona, Italy
| | - Michela Deiana
- Department of Infectious and Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Verona, Italy
| | - Antonio Fadda
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Luca Bertoli
- Department of Biotechnology, University of Verona, Verona, Italy
| | | | - Silvia Riccetti
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Luisa Barzon
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Chiara Piubelli
- Department of Infectious and Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Verona, Italy
| | | | - Maria Rosaria Capobianchi
- Department of Infectious and Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Verona, Italy
| | - Concetta Castilletti
- Department of Infectious and Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Verona, Italy
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Mori A, Lavezzari D, Pomari E, Deiana M, Piubelli C, Capobianchi MR, Castilletti C. sgRNAs: A SARS-CoV-2 emerging issue. ASPECTS OF MOLECULAR MEDICINE 2023; 1:100008. [PMID: 37519862 PMCID: PMC10105645 DOI: 10.1016/j.amolm.2023.100008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 04/14/2023] [Accepted: 04/15/2023] [Indexed: 08/01/2023]
Abstract
Like for other coronaviruses, SARS-CoV-2 gene expression strategy is based on the synthesis of a nested set of subgenomic mRNA species (sgRNAs). These sgRNA are synthesized using a "discontinuous transcription" mechanism that relies on template switching at Transcription Regulatory Sequences (TRS). Both canonical (c-sgRNA) and non-canonical (nc-sgRNA, less numerous) subgenomic RNA species can be produced. Currently, sgRNAs are investigated on the basis of sequence data obtained through next generation sequencing (NGS), and bioinformatic tools are crucial for their identification, characterization and quantification. To date, few software have been developed to this aim, whose reliability and applicability to all the available NGS platforms need to be established, to build confidence on the information resulting from such tools. In fact, these information may be crucial for the in depth elucidation of viral expression strategy, particularly in respect of the significance of nc-sgRNAs, and for the possible use of sgRNAs as potential markers of virus replicative activity in infected patients.
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Affiliation(s)
- Antonio Mori
- Department of Infectious, Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, 37024, Verona, Italy
| | - Denise Lavezzari
- Department of Infectious, Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, 37024, Verona, Italy
| | - Elena Pomari
- Department of Infectious, Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, 37024, Verona, Italy
| | - Michela Deiana
- Department of Infectious, Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, 37024, Verona, Italy
| | - Chiara Piubelli
- Department of Infectious, Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, 37024, Verona, Italy
| | - Maria Rosaria Capobianchi
- Department of Infectious, Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, 37024, Verona, Italy
| | - Concetta Castilletti
- Department of Infectious, Tropical Diseases and Microbiology, IRCCS Sacro Cuore Don Calabria Hospital, Negrar di Valpolicella, 37024, Verona, Italy
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Intragenomic rearrangements involving 5'-untranslated region segments in SARS-CoV-2, other betacoronaviruses, and alphacoronaviruses. Virol J 2023; 20:36. [PMID: 36829234 PMCID: PMC9957694 DOI: 10.1186/s12985-023-01998-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Accepted: 02/21/2023] [Indexed: 02/26/2023] Open
Abstract
BACKGROUND Variation of the betacoronavirus SARS-CoV-2 has been the bane of COVID-19 control. Documented variation includes point mutations, deletions, insertions, and recombination among closely or distantly related coronaviruses. Here, we describe yet another aspect of genome variation by beta- and alphacoronaviruses that was first documented in an infectious isolate of the betacoronavirus SARS-CoV-2, obtained from 3 patients in Hong Kong that had a 5'-untranslated region segment at the end of the ORF6 gene that in its new location translated into an ORF6 protein with a predicted modified carboxyl terminus. While comparing the amino acid sequences of translated ORF8 genes in the GenBank database, we found a subsegment of the same 5'-UTR-derived amino acid sequence modifying the distal end of ORF8 of an isolate from the United States and decided to carry out a systematic search. METHODS Using the nucleotide and in the case of SARS-CoV-2 also the translated amino acid sequence in three reading frames of the genomic termini of coronaviruses as query sequences, we searched for 5'-UTR sequences in regions other than the 5'-UTR in SARS-CoV-2 and reference strains of alpha-, beta-, gamma-, and delta-coronaviruses. RESULTS We here report numerous genomic insertions of 5'-untranslated region sequences into coding regions of SARS-CoV-2, other betacoronaviruses, and alphacoronaviruses, but not delta- or gammacoronaviruses. To our knowledge this is the first systematic description of such insertions. In many cases, these insertions would change viral protein sequences and further foster genomic flexibility and viral adaptability through insertion of transcription regulatory sequences in novel positions within the genome. Among human Embecorivus betacoronaviruses, for instance, from 65% to all of the surveyed sequences in publicly available databases contain inserted 5'-UTR sequences. CONCLUSION The intragenomic rearrangements involving 5'-untranslated region sequences described here, which in several cases affect highly conserved genes with a low propensity for recombination, may underlie the generation of variants homotypic with those of concern or interest and with potentially differing pathogenic profiles. Intragenomic rearrangements thus add to our appreciation of how variants of SARS-CoV-2 and other beta- and alphacoronaviruses may arise.
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Treffers EE, Tas A, Scholte FEM, de Ru AH, Snijder EJ, van Veelen PA, van Hemert MJ. The alphavirus nonstructural protein 2 NTPase induces a host translational shut-off through phosphorylation of eEF2 via cAMP-PKA-eEF2K signaling. PLoS Pathog 2023; 19:e1011179. [PMID: 36848386 PMCID: PMC9997916 DOI: 10.1371/journal.ppat.1011179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 03/09/2023] [Accepted: 02/03/2023] [Indexed: 03/01/2023] Open
Abstract
Chikungunya virus (CHIKV) is a reemerging alphavirus. Since 2005, it has infected millions of people during outbreaks in Africa, Asia, and South/Central America. CHIKV replication depends on host cell factors at many levels and is expected to have a profound effect on cellular physiology. To obtain more insight into host responses to infection, stable isotope labeling with amino acids in cell culture and liquid chromatography-tandem mass spectrometry were used to assess temporal changes in the cellular phosphoproteome during CHIKV infection. Among the ~3,000 unique phosphorylation sites analyzed, the largest change in phosphorylation status was measured on residue T56 of eukaryotic elongation factor 2 (eEF2), which showed a >50-fold increase at 8 and 12 h p.i. Infection with other alphaviruses (Semliki Forest, Sindbis and Venezuelan equine encephalitis virus (VEEV)) triggered a similarly strong eEF2 phosphorylation. Expression of a truncated form of CHIKV or VEEV nsP2, containing only the N-terminal and NTPase/helicase domains (nsP2-NTD-Hel), sufficed to induce eEF2 phosphorylation, which could be prevented by mutating key residues in the Walker A and B motifs of the NTPase domain. Alphavirus infection or expression of nsP2-NTD-Hel resulted in decreased cellular ATP levels and increased cAMP levels. This did not occur when catalytically inactive NTPase mutants were expressed. The wild-type nsP2-NTD-Hel inhibited cellular translation independent of the C-terminal nsP2 domain, which was previously implicated in directing the virus-induced host shut-off for Old World alphaviruses. We hypothesize that the alphavirus NTPase activates a cellular adenylyl cyclase resulting in increased cAMP levels, thus activating PKA and subsequently eukaryotic elongation factor 2 kinase. This in turn triggers eEF2 phosphorylation and translational inhibition. We conclude that the nsP2-driven increase of cAMP levels contributes to the alphavirus-induced shut-off of cellular protein synthesis that is shared between Old and New World alphaviruses. MS Data are available via ProteomeXchange with identifier PXD009381.
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Affiliation(s)
- Emmely E. Treffers
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
- Center for Proteomics & Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Ali Tas
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Florine E. M. Scholte
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Arnoud H. de Ru
- Center for Proteomics & Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Eric J. Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Peter A. van Veelen
- Center for Proteomics & Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
| | - Martijn J. van Hemert
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
- * E-mail:
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Abstract
Coronavirus disease (COVID-19) is an infectious airborne viral pneumonia caused by a novel virus belonging to the family coronaviridae. On February 11, 2019, the Internal Committee on Taxonomy of Virus (ICTV) announced the name of the novel virus as "severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). One of the proteins present on its membrane i.e. the Spike protein is responsible for the attachment of the virus to the host. It spreads through the salivary droplets released when an infected person sneezes or coughs. The best way to slow down the disease is by protecting self by washing hands and using the disinfectant. Most of the infected people experience mild to moderate breathing issues. Serious illness might develop in people with underlying cardiovascular problems, diabetes and other immuno-compromised diseases. To date, there is no effective medicine available in the market which is effective in COVID-19. However, healthcare professionals are using ritonavir, flavipiravir, lopinavir, hydroxychloroquine and remdesivir. Along with the medicines, some countries are using convalescent plasma and mesenchymal stem cells for treatment. Till date, it has claimed millions of death worldwide. In this detailed review, we have discussed the structure of SARS-CoV-2, essential proteins, its lifecycle, transmission, symptoms, pathology, clinical features, diagnosis, prevention, treatment and epidemiology of the disease.
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Affiliation(s)
- Heena Rehman
- Department of Biochemistry, Jamia Hamdard, New Delhi, India
| | - Md Iftekhar Ahmad
- Department of Pharmaceutics, Shri Gopichand College of Pharmacy, Baghpat, India
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Dong X, Penrice-Randal R, Goldswain H, Prince T, Randle N, Donovan-Banfield I, Salguero FJ, Tree J, Vamos E, Nelson C, Clark J, Ryan Y, Stewart JP, Semple MG, Baillie JK, Openshaw PJM, Turtle L, Matthews DA, Carroll MW, Darby AC, Hiscox JA. Analysis of SARS-CoV-2 known and novel subgenomic mRNAs in cell culture, animal model, and clinical samples using LeTRS, a bioinformatic tool to identify unique sequence identifiers. Gigascience 2022; 11:6593429. [PMID: 35639883 PMCID: PMC9154083 DOI: 10.1093/gigascience/giac045] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 12/08/2021] [Accepted: 04/07/2022] [Indexed: 12/30/2022] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has a complex strategy for the transcription of viral subgenomic mRNAs (sgmRNAs), which are targets for nucleic acid diagnostics. Each of these sgmRNAs has a unique 5' sequence, the leader-transcriptional regulatory sequence gene junction (leader-TRS junction), that can be identified using sequencing. High-resolution sequencing has been used to investigate the biology of SARS-CoV-2 and the host response in cell culture and animal models and from clinical samples. LeTRS, a bioinformatics tool, was developed to identify leader-TRS junctions and can be used as a proxy to quantify sgmRNAs for understanding virus biology. LeTRS is readily adaptable for other coronaviruses such as Middle East respiratory syndrome coronavirus or a future newly discovered coronavirus. LeTRS was tested on published data sets and novel clinical samples from patients and longitudinal samples from animal models with coronavirus disease 2019. LeTRS identified known leader-TRS junctions and identified putative novel sgmRNAs that were common across different mammalian species. This may be indicative of an evolutionary mechanism where plasticity in transcription generates novel open reading frames, which can then subject to selection pressure. The data indicated multiphasic abundance of sgmRNAs in two different animal models. This recapitulates the relative sgmRNA abundance observed in cells at early points in infection but not at late points. This pattern is reflected in some human nasopharyngeal samples and therefore has implications for transmission models and nucleic acid-based diagnostics. LeTRS provides a quantitative measure of sgmRNA abundance from sequencing data. This can be used to assess the biology of SARS-CoV-2 (or other coronaviruses) in clinical and nonclinical samples, especially to evaluate different variants and medical countermeasures that may influence viral RNA synthesis.
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Affiliation(s)
- Xiaofeng Dong
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Rebekah Penrice-Randal
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Hannah Goldswain
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Tessa Prince
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Nadine Randle
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - I'ah Donovan-Banfield
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
- NIHR Health Protection Research Unit in Emerging and Zoonotic Infections, Liverpool, Liverpool, L69 7BE, UK
| | | | - Julia Tree
- UK-Health Security Agency, Salisbury, SP4 0JG, UK
| | - Ecaterina Vamos
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Charlotte Nelson
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Jordan Clark
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Yan Ryan
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - James P Stewart
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Malcolm G Semple
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
- NIHR Health Protection Research Unit in Emerging and Zoonotic Infections, Liverpool, Liverpool, L69 7BE, UK
| | - J Kenneth Baillie
- The Roslin Institute, University of Edinburgh, Edinburgh, EH25 9RG, UK
| | - Peter J M Openshaw
- National Heart and Lung Institute, Imperial College London, London, SW3 6LY, UK
| | - Lance Turtle
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
- NIHR Health Protection Research Unit in Emerging and Zoonotic Infections, Liverpool, Liverpool, L69 7BE, UK
| | | | - Miles W Carroll
- NIHR Health Protection Research Unit in Emerging and Zoonotic Infections, Liverpool, Liverpool, L69 7BE, UK
- UK-Health Security Agency, Salisbury, SP4 0JG, UK
| | - Alistair C Darby
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, L3 5RF, UK
| | - Julian A Hiscox
- Correspondence address.Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, ic2 Building, Liverpool, L3 5RF, UK. E-mail:
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Chazal N. Coronavirus, the King Who Wanted More Than a Crown: From Common to the Highly Pathogenic SARS-CoV-2, Is the Key in the Accessory Genes? Front Microbiol 2021; 12:682603. [PMID: 34335504 PMCID: PMC8317507 DOI: 10.3389/fmicb.2021.682603] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 06/22/2021] [Indexed: 12/14/2022] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), that emerged in late 2019, is the etiologic agent of the current "coronavirus disease 2019" (COVID-19) pandemic, which has serious health implications and a significant global economic impact. Of the seven human coronaviruses, all of which have a zoonotic origin, the pandemic SARS-CoV-2, is the third emerging coronavirus, in the 21st century, highly pathogenic to the human population. Previous human coronavirus outbreaks (SARS-CoV-1 and MERS-CoV) have already provided several valuable information on some of the common molecular and cellular mechanisms of coronavirus infections as well as their origin. However, to meet the new challenge caused by the SARS-CoV-2, a detailed understanding of the biological specificities, as well as knowledge of the origin are crucial to provide information on viral pathogenicity, transmission and epidemiology, and to enable strategies for therapeutic interventions and drug discovery. Therefore, in this review, we summarize the current advances in SARS-CoV-2 knowledges, in light of pre-existing information of other recently emerging coronaviruses. We depict the specificity of the immune response of wild bats and discuss current knowledge of the genetic diversity of bat-hosted coronaviruses that promotes viral genome expansion (accessory gene acquisition). In addition, we describe the basic virology of coronaviruses with a special focus SARS-CoV-2. Finally, we highlight, in detail, the current knowledge of genes and accessory proteins which we postulate to be the major keys to promote virus adaptation to specific hosts (bat and human), to contribute to the suppression of immune responses, as well as to pathogenicity.
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Affiliation(s)
- Nathalie Chazal
- Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, CNRS, Montpellier, France
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8
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Yao S, Narayanan A, Majowicz SA, Jose J, Archetti M. A synthetic defective interfering SARS-CoV-2. PeerJ 2021; 9:e11686. [PMID: 34249513 PMCID: PMC8255065 DOI: 10.7717/peerj.11686] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 06/07/2021] [Indexed: 11/20/2022] Open
Abstract
Viruses thrive by exploiting the cells they infect, but in order to replicate and infect other cells they must produce viral proteins. As a result, viruses are also susceptible to exploitation by defective versions of themselves that do not produce such proteins. A defective viral genome with deletions in protein-coding genes could still replicate in cells coinfected with full-length viruses. Such a defective genome could even replicate faster due to its shorter size, interfering with the replication of the virus. We have created a synthetic defective interfering version of SARS-CoV-2, the virus causing the Covid-19 pandemic, assembling parts of the viral genome that do not code for any functional protein but enable the genome to be replicated and packaged. This synthetic defective genome replicates three times faster than SARS-CoV-2 in coinfected cells, and interferes with it, reducing the viral load of infected cells by half in 24 hours. The synthetic genome is transmitted as efficiently as the full-length genome, suggesting the location of the putative packaging signal of SARS-CoV-2. A version of such a synthetic construct could be used as a self-promoting antiviral therapy: by enabling replication of the synthetic genome, the virus would promote its own demise.
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Affiliation(s)
- Shun Yao
- Department of Biology, Pennsylvania State University, University Park, United States of America
| | - Anoop Narayanan
- Department of Biochemistry & Molecular Biology, Pennsylvania State University, University Park, United States of America
| | - Sydney A Majowicz
- Department of Biochemistry & Molecular Biology, Pennsylvania State University, University Park, United States of America
| | - Joyce Jose
- Department of Biochemistry & Molecular Biology, Pennsylvania State University, University Park, United States of America.,The Huck Institutes for the Life Sciences, Pennsylvania State University, University Park, United States of America
| | - Marco Archetti
- Department of Biology, Pennsylvania State University, University Park, United States of America.,The Huck Institutes for the Life Sciences, Pennsylvania State University, University Park, United States of America
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9
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Lauber C, Seifert M, Bartenschlager R, Seitz S. Discovery of highly divergent lineages of plant-associated astro-like viruses sheds light on the emergence of potyviruses. Virus Res 2018; 260:38-48. [PMID: 30452944 DOI: 10.1016/j.virusres.2018.11.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 11/15/2018] [Accepted: 11/15/2018] [Indexed: 01/06/2023]
Abstract
RNA viruses are believed to have originated from a common ancestor, but how this ancestral genome evolved into the large variety of genomic architectures and viral proteomes we see today remains largely unknown. Tackling this question is hindered by the lack of universally conserved proteins other than the RNA-dependent RNA polymerase (RdRp) as well as a limited RNA virus sampling. The latter is still heavily biased towards relatively few viral lineages from a non-representative collection of hosts, which complicates studies aiming to reveal possible trajectories during the evolution of RNA virus genomes that are favored over others. We report the discovery of 11 highly divergent lineages of viruses with genomic architectures that resemble those of the astroviruses. These genomes were initially identified through a sequence homology search in more than 6600 plant transcriptome projects from the Sequence Read Archive (SRA) using astrovirus representatives as query. Seed-based viral genome assembly of unprocessed SRA data for several dozens of the most promising hits resulted in two viral genome sequences with full-length coding regions, nine partial genomes and a much larger number of short sequence fragments. Genomic and phylogenetic characterization of the 11 discovered viruses, which we coined plastroviruses (plant-associated astro-like viruses), showed that they are related to both astro- and potyviruses and allowed us to identify divergent Serine protease, RdRp and viral capsid domains encoded in the plastrovirus genome. Interestingly, some of the plastroviruses shared different features with potyviruses including the replacement of the catalytic Ser by a Cys residue in the protease active site. These results suggest that plastroviruses may have reached different points on an evolutionary trajectory from astro-like to poty-like genomes. A model how potyviruses might have emerged from (pl)astro-like ancestors in a multi-step process is discussed.
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Affiliation(s)
- Chris Lauber
- Institute for Medical Informatics and Biometry, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, 01307 Dresden, Germany; Division of Virus-associated Carcinogenesis, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; European Virus Bioinformatics Center (EVBC), 07743 Jena, Germany.
| | - Michael Seifert
- Institute for Medical Informatics and Biometry, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, 01307 Dresden, Germany
| | - Ralf Bartenschlager
- Division of Virus-associated Carcinogenesis, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; Department of Infectious Diseases, Molecular Virology, Heidelberg University, 69120 Heidelberg, Germany
| | - Stefan Seitz
- Division of Virus-associated Carcinogenesis, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; Department of Infectious Diseases, Molecular Virology, Heidelberg University, 69120 Heidelberg, Germany
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10
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Xie Q, Cao Y, Su J, Wu J, Wu X, Wan C, He M, Ke C, Zhang B, Zhao W. Two deletion variants of Middle East respiratory syndrome coronavirus found in a patient with characteristic symptoms. Arch Virol 2017; 162:2445-2449. [PMID: 28421366 PMCID: PMC5506503 DOI: 10.1007/s00705-017-3361-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Accepted: 03/27/2017] [Indexed: 02/04/2023]
Abstract
Significant sequence variation of Middle East respiratory syndrome coronavirus (MERS CoV) has never been detected since it was first reported in 2012. A MERS patient came from Korea to China in late May 2015. The patient was 44 years old and had symptoms including high fever, dry cough with a little phlegm, and shortness of breath, which are roughly consistent with those associated with MERS, and had had close contact with individuals with confirmed cases of MERS.After one month of therapy with antiviral, anti-infection, and immune-enhancing agents, the patient recovered in the hospital and was discharged. A nasopharyngeal swab sample was collected for direct sequencing, which revealed two deletion variants of MERS CoV. Deletions of 414 and 419 nt occurred between ORF5 and the E protein, resulting in a partial protein fusion or truncation of ORF5 and the E protein. Functional analysis by bioinformatics and comparison to previous studies implied that the two variants might be defective in their ability to package MERS CoV. However, the mechanism of how these deletions occurred and what effects they have need to be further investigated.
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Affiliation(s)
- Qian Xie
- Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, No. 1023 Shatai Road, Guangzhou, 510515, People's Republic of China.,Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Public Health, Southern Medical University, Guangzhou, 510515, China
| | - Yujuan Cao
- Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, No. 1023 Shatai Road, Guangzhou, 510515, People's Republic of China.,Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Public Health, Southern Medical University, Guangzhou, 510515, China
| | - Juan Su
- Medical Key Laboratory for Repository and Application of Pathogenic Microbiology, Research Center for Pathogens Detection Technology of Emerging Infectious Diseases, Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
| | - Jie Wu
- Medical Key Laboratory for Repository and Application of Pathogenic Microbiology, Research Center for Pathogens Detection Technology of Emerging Infectious Diseases, Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China
| | - Xianbo Wu
- Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, No. 1023 Shatai Road, Guangzhou, 510515, People's Republic of China.,Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Public Health, Southern Medical University, Guangzhou, 510515, China
| | - Chengsong Wan
- Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, No. 1023 Shatai Road, Guangzhou, 510515, People's Republic of China.,Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Public Health, Southern Medical University, Guangzhou, 510515, China
| | - Mingliang He
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
| | - Changwen Ke
- Medical Key Laboratory for Repository and Application of Pathogenic Microbiology, Research Center for Pathogens Detection Technology of Emerging Infectious Diseases, Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China.
| | - Bao Zhang
- Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, No. 1023 Shatai Road, Guangzhou, 510515, People's Republic of China. .,Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Public Health, Southern Medical University, Guangzhou, 510515, China.
| | - Wei Zhao
- Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, No. 1023 Shatai Road, Guangzhou, 510515, People's Republic of China. .,Guangzhou Key Laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Public Health, Southern Medical University, Guangzhou, 510515, China.
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11
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Scholte FEM, Tas A, Martina BEE, Cordioli P, Narayanan K, Makino S, Snijder EJ, van Hemert MJ. Characterization of synthetic Chikungunya viruses based on the consensus sequence of recent E1-226V isolates. PLoS One 2013; 8:e71047. [PMID: 23936484 PMCID: PMC3731263 DOI: 10.1371/journal.pone.0071047] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 06/26/2013] [Indexed: 01/13/2023] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that re-emerged in 2004 and has caused massive outbreaks in recent years. The lack of a licensed vaccine or treatment options emphasize the need to obtain more insight into the viral life cycle and CHIKV-host interactions. Infectious cDNA clones are important tools for such studies, and for mechanism of action studies on antiviral compounds. Existing CHIKV cDNA clones are based on a single genome from an individual clinical isolate, which is expected to have evolved specific characteristics in response to the host environment, and possibly also during subsequent cell culture passaging. To obtain a virus expected to have the general characteristics of the recent E1-226V CHIKV isolates, we have constructed a new CHIKV full-length cDNA clone, CHIKV LS3, based on the consensus sequence of their aligned genomes. Here we report the characterization of this synthetic virus and a green fluorescent protein-expressing variant (CHIKV LS3-GFP). Their characteristics were compared to those of natural strain ITA07-RA1, which was isolated during the 2007 outbreak in Italy. In cell culture the synthetic viruses displayed phenotypes comparable to the natural isolate, and in a mouse model they caused lethal infections that were indistinguishable from infections with a natural strain. Compared to ITA07-RA1 and clinical isolate NL10/152, the synthetic viruses displayed similar sensitivities to several antiviral compounds. 3-deaza-adenosine was identified as a new inhibitor of CHIKV replication. Cyclosporin A had no effect on CHIKV replication, suggesting that cyclophilins -opposite to what was found for other +RNA viruses- do not play an essential role in CHIKV replication. The characterization of the consensus sequence-based synthetic viruses and their comparison to natural isolates demonstrated that CHIKV LS3 and LS3-GFP are suitable and representative tools to study CHIKV-host interactions, screen for antiviral compounds and unravel their mode of action.
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Affiliation(s)
- Florine E. M. Scholte
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Ali Tas
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Byron E. E. Martina
- Department of Viroscience, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Paolo Cordioli
- Istituto Zooprofilattico Sperimentale della Lombardia e dell’Emilia Romagna, Brescia, Italy
| | - Krishna Narayanan
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Shinji Makino
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Eric J. Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Martijn J. van Hemert
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
- * E-mail:
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12
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Crossley BM, Mock RE, Callison SA, Hietala SK. Identification and characterization of a novel alpaca respiratory coronavirus most closely related to the human coronavirus 229E. Viruses 2012; 4:3689-700. [PMID: 23235471 PMCID: PMC3528286 DOI: 10.3390/v4123689] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 11/13/2012] [Accepted: 11/23/2012] [Indexed: 12/27/2022] Open
Abstract
In 2007, a novel coronavirus associated with an acute respiratory disease in alpacas (Alpaca Coronavirus, ACoV) was isolated. Full-length genomic sequencing of the ACoV demonstrated the genome to be consistent with other Alphacoronaviruses. A putative additional open-reading frame was identified between the nucleocapsid gene and 3'UTR. The ACoV was genetically most similar to the common human coronavirus (HCoV) 229E with 92.2% nucleotide identity over the entire genome. A comparison of spike gene sequences from ACoV and from HCoV-229E isolates recovered over a span of five decades showed the ACoV to be most similar to viruses isolated in the 1960's to early 1980's. The true origin of the ACoV is unknown, however a common ancestor between the ACoV and HCoV-229E appears to have existed prior to the 1960's, suggesting virus transmission, either as a zoonosis or anthroponosis, has occurred between alpacas and humans.
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Affiliation(s)
- Beate M. Crossley
- California Animal Health and Food Safety Laboratory System, University of California-Davis, Davis, West Health Sciences Drive, CA 95616, USA; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: Tel.: +1-530-752-5662; Fax: +1-530-752-6253
| | - Richard E. Mock
- North Carolina Veterinary Diagnostic Laboratory System, Raleigh, NC 27699, USA; E-Mail:
| | | | - Sharon K. Hietala
- California Animal Health and Food Safety Laboratory System, University of California-Davis, Davis, West Health Sciences Drive, CA 95616, USA; E-Mail:
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13
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Brandão PE. Avian coronavirus spike glycoprotein ectodomain shows a low codon adaptation to Gallus gallus with virus-exclusive codons in strategic amino acids positions. J Mol Evol 2012; 75:19-24. [PMID: 22903606 PMCID: PMC7079877 DOI: 10.1007/s00239-012-9515-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 08/03/2012] [Indexed: 11/30/2022]
Abstract
This is a study on the Avian coronavirus IBV and chicken host-relationship from the codon usage point of view based on fifty-nine non-redundant IBV S1 sequences (nt 1–507) from strains detected worldwide and chicken tissue-specific protein genes sequences from IBV-replicating sites. The effective number of codons (ENC) values ranged from 36 to 47.8, indicating a high-to-moderate codon usage bias. The highest IBV codon adaptation index (CAI) value was 0.7, indicating a distant virus versus host synonymous codons usage. The ENC × GC3 % curve indicates that both mutational pressure and natural selection are the driving forces on codon usage pattern in S1. The low CAI values agree with a low S protein expression and considering that S protein is a determinant for attachment and neutralization, this could be a further mechanism besides mRNA transcription attenuation for a low expression of this protein leading to an immune camouflage.
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Affiliation(s)
- Paulo E Brandão
- Department of Preventive Veterinary Medicine and Animal Health, School of Veterinary Medicine, University of São Paulo, Brazil.
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14
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Alminaite A, Backström V, Vaheri A, Plyusnin A. Oligomerization of hantaviral nucleocapsid protein: charged residues in the N-terminal coiled-coil domain contribute to intermolecular interactions. J Gen Virol 2008; 89:2167-2174. [PMID: 18753226 DOI: 10.1099/vir.0.2008/004044-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The nucleocapsid (N) protein of hantaviruses (family Bunyaviridae) is the most abundant component of the virion; it encapsidates genomic RNA segments and participates in viral genome transcription and replication, as well as in virus assembly. During RNA encapsidation, the N protein forms intermediate trimers and then oligomers via 'head-to-head, tail-to-tail' interactions. In previous work, using Tula hantavirus (TULV) N protein as a model, it was demonstrated that an intact coiled-coil structure of the N terminus is crucial for the oligomerization capacity of the N protein and that the hydrophobic 'a' residues from the second alpha-helix are especially important. Here, the importance of charged amino acid residues located within the coiled-coil for trimer formation and oligomerization was analysed. To predict the interacting surfaces of the monomers, the previous in silico model of TULV coiled-coils was first upgraded, taking advantage of the recently published crystal structure of the N-terminal coiled-coil of the Sin Nombre virus N protein. The results obtained using a mammalian two-hybrid assay suggested that conserved, charged amino acid residues within the coiled-coil make a substantial contribution to N protein oligomerization. This contribution probably involves (i) the formation of interacting surfaces of the N monomers (residues D35 and D38, located at the tip of the coiled-coil loop, and R63 appear particularly important) and (ii) stabilization of the coiled-coil via intramolecular ionic bridging (with E55 as a key player). It is hypothesized that the tips of the coiled-coils are the first to come into direct contact and thus to initiate tight packing of the three structures.
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Affiliation(s)
- Agne Alminaite
- Department of Virology, Haartman Institute, PO Box 21, FIN-00014 University of Helsinki, Finland
| | - Vera Backström
- Department of Biochemistry and Pharmacy, Åbo Akademi University, Turku, Finland
| | - Antti Vaheri
- Department of Virology, Haartman Institute, PO Box 21, FIN-00014 University of Helsinki, Finland
| | - Alexander Plyusnin
- Department of Virology, Haartman Institute, PO Box 21, FIN-00014 University of Helsinki, Finland
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15
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Spencer KA, Dee M, Britton P, Hiscox JA. Role of phosphorylation clusters in the biology of the coronavirus infectious bronchitis virus nucleocapsid protein. Virology 2007; 370:373-81. [PMID: 17931676 PMCID: PMC7103301 DOI: 10.1016/j.virol.2007.08.016] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 08/11/2007] [Accepted: 08/16/2007] [Indexed: 01/15/2023]
Abstract
The coronavirus infectious bronchitis virus (IBV) nucleocapsid (N) protein is an RNA binding protein which is phosphorylated at two conserved clusters. Kinetic analysis of RNA binding indicated that the C-terminal phosphorylation cluster was involved in the recognition of viral RNA from non-viral RNA. The IBV N protein has been found to be essential for the successful recovery of IBV using reverse genetics systems. Rescue experiments indicated that phosphorylated N protein recovered infectious IBV more efficiently when compared to modified N proteins either partially or non-phosphorylated. Our data indicate that the phosphorylated form of the IBV N protein plays a role in virus biology.
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Affiliation(s)
- Kelly-Anne Spencer
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
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16
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Spencer KA, Hiscox JA. Characterisation of the RNA binding properties of the coronavirus infectious bronchitis virus nucleocapsid protein amino-terminal region. FEBS Lett 2006; 580:5993-8. [PMID: 17052713 PMCID: PMC7094245 DOI: 10.1016/j.febslet.2006.09.052] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Revised: 09/05/2006] [Accepted: 09/22/2006] [Indexed: 11/24/2022]
Abstract
The coronavirus nucleocapsid (N) protein binds viral RNA to form the ribonucleocapsid and regulate RNA synthesis. The interaction of N protein with viral RNA was investigated using circular dichroism and surface plasmon resonance. N protein underwent a conformational change upon binding viral RNA and the data indicated electrostatic interactions were involved in the binding of the protein to RNA. Kinetic analysis suggested the amino-terminal region facilitates long-range non-specific interactions between N protein and viral RNA, thus bringing the RNA into close proximity to N protein allowing specific contacts to form via a 'lure' and 'lock' mechanism.
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Affiliation(s)
- Kelly-Anne Spencer
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Julian A. Hiscox
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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17
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Abstract
Coronaviruses are large, enveloped RNA viruses of both medical and veterinary importance. Interest in this viral family has intensified in the past few years as a result of the identification of a newly emerged coronavirus as the causative agent of severe acute respiratory syndrome (SARS). At the molecular level, coronaviruses employ a variety of unusual strategies to accomplish a complex program of gene expression. Coronavirus replication entails ribosome frameshifting during genome translation, the synthesis of both genomic and multiple subgenomic RNA species, and the assembly of progeny virions by a pathway that is unique among enveloped RNA viruses. Progress in the investigation of these processes has been enhanced by the development of reverse genetic systems, an advance that was heretofore obstructed by the enormous size of the coronavirus genome. This review summarizes both classical and contemporary discoveries in the study of the molecular biology of these infectious agents, with particular emphasis on the nature and recognition of viral receptors, viral RNA synthesis, and the molecular interactions governing virion assembly.
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Affiliation(s)
- Paul S Masters
- Wadsworth Center, New York State Department of Health, Albany, 12201, USA
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18
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Pasternak AO, Spaan WJM, Snijder EJ. Nidovirus transcription: how to make sense...? J Gen Virol 2006; 87:1403-1421. [PMID: 16690906 DOI: 10.1099/vir.0.81611-0] [Citation(s) in RCA: 255] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Many positive-stranded RNA viruses use subgenomic mRNAs to express part of their genetic information. To produce structural and accessory proteins, members of the order Nidovirales (corona-, toro-, arteri- and roniviruses) generate a 3' co-terminal nested set of at least three and often seven to nine mRNAs. Coronavirus and arterivirus subgenomic transcripts are not only 3' co-terminal but also contain a common 5' leader sequence, which is derived from the genomic 5' end. Their synthesis involves a process of discontinuous RNA synthesis that resembles similarity-assisted RNA recombination. Most models proposed over the past 25 years assume co-transcriptional fusion of subgenomic RNA leader and body sequences, but there has been controversy over the question of whether this occurs during plus- or minus-strand synthesis. In the latter model, which has now gained considerable support, subgenomic mRNA synthesis takes place from a complementary set of subgenome-size minus-strand RNAs, produced by discontinuous minus-strand synthesis. Sense-antisense base-pairing interactions between short conserved sequences play a key regulatory role in this process. In view of the presumed common ancestry of nidoviruses, the recent finding that ronivirus and torovirus mRNAs do not contain a common 5' leader sequence is surprising. Apparently, major mechanistic differences must exist between nidoviruses, which raises questions about the functions of the common leader sequence and nidovirus transcriptase proteins and the evolution of nidovirus transcription. In this review, nidovirus transcription mechanisms are compared, the experimental systems used are critically assessed and, in particular, the impact of recently developed reverse genetic systems is discussed.
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Affiliation(s)
- Alexander O Pasternak
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, LUMC P4-26, PO Box 9600, 2300 RC Leiden, The Netherlands
| | - Willy J M Spaan
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, LUMC P4-26, PO Box 9600, 2300 RC Leiden, The Netherlands
| | - Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, LUMC P4-26, PO Box 9600, 2300 RC Leiden, The Netherlands
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19
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Sawicki SG, Sawicki DL, Younker D, Meyer Y, Thiel V, Stokes H, Siddell SG. Functional and genetic analysis of coronavirus replicase-transcriptase proteins. PLoS Pathog 2005; 1:e39. [PMID: 16341254 PMCID: PMC1298938 DOI: 10.1371/journal.ppat.0010039] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Accepted: 11/01/2005] [Indexed: 12/15/2022] Open
Abstract
The coronavirus replicase-transcriptase complex is an assembly of viral and cellular proteins that mediate the synthesis of genome and subgenome-sized mRNAs in the virus-infected cell. Here, we report a genetic and functional analysis of 19 temperature-sensitive (ts) mutants of Murine hepatitis virus MHV-A59 that are unable to synthesize viral RNA when the infection is initiated and maintained at the non-permissive temperature. Both classical and biochemical complementation analysis leads us to predict that the majority of MHV-A59 ORF1a replicase gene products (non-structural proteins nsp1-nsp11) form a single complementation group (cistron1) while the replicase gene products encoded in ORF1b (non-structural proteins nsp12-nsp16) are able to function in trans and comprise at least three, and possibly five, further complementation groups (cistrons II-VI). Also, we have identified mutations in the non-structural proteins nsp 4, nsp5, nsp10, nsp12, nsp14, and nsp16 that are responsible for the ts phenotype of eight MHV-A59 mutants, which allows us to conclude that these proteins are essential for the assembly of a functional replicase-transcriptase complex. Finally, our analysis of viral RNA synthesis in ts mutant virus-infected cells allows us to discriminate three phenotypes with regard to the inability of specific mutants to synthesize viral RNA at the non-permissive temperature. Mutant LA ts6 appeared to be defective in continuing negative-strand synthesis, mutant Alb ts16 appeared to form negative strands but these were not utilized for positive-strand RNA synthesis, and mutant Alb ts22 was defective in the elongation of both positive- and negative-strand RNA. On the basis of these results, we propose a model that describes a pathway for viral RNA synthesis in MHV-A59-infected cells. Further biochemical analysis of these mutants should allow us to identify intermediates in this pathway and elucidate the precise function(s) of the viral replicase proteins involved.
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Affiliation(s)
- Stanley G Sawicki
- Department of Medical Microbiology and Immunology, Medical University of Ohio, Toledo, Ohio, United States of America
| | - Dorothea L Sawicki
- Department of Medical Microbiology and Immunology, Medical University of Ohio, Toledo, Ohio, United States of America
| | - Diane Younker
- Department of Medical Microbiology and Immunology, Medical University of Ohio, Toledo, Ohio, United States of America
| | - Yvonne Meyer
- Institute of Virology, University of Würzburg, Würzburg, Germany
| | - Volker Thiel
- Institute of Virology, University of Würzburg, Würzburg, Germany
| | - Helen Stokes
- Department of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom
| | - Stuart G Siddell
- Department of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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20
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Abstract
At the VIth International Symposium on Corona and Related Viruses held in Quebec, Canada in 1994 we presented a new model for coronavirus transcription to explain how subgenome-length minus strands, which are used as templates for the synthesis of subgenomic mRNAs, might arise by a process involving discontinuous RNA synthesis. The old model explaining subgenomic mRNA synthesis, which was called leader-primed transcription, was based on erroneous evidence that only genome-length negative strands were present in replicative intermediates. To explain the discovery of subgenome-length minus strands, a related model, called the replicon model, was proposed: The subgenomic mRNAs would be produced initially by leader-primed transcription and then replicated into minus-strand templates that would in turn be transcribed into subgenomic mRNAs. We review the experimental evidence that led us to formulate a third model proposing that the discontinuous event in coronavirus RNA synthesis occurs during minus strand synthesis. With our model the genome is copied both continuously to produce minus-strand templates for genome RNA synthesis and discontinuously to produce minus-strand templates for subgenomic mRNA synthesis, and the subgenomic mRNAs do not function as templates for minus strand synthesis, only the genome does.
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Affiliation(s)
- S G Sawicki
- Department of Microbiology, Medical College of Ohio, Toledo, OH 43614, USA.
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21
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Sola I, Moreno JL, Zúñiga S, Alonso S, Enjuanes L. Role of nucleotides immediately flanking the transcription-regulating sequence core in coronavirus subgenomic mRNA synthesis. J Virol 2005; 79:2506-16. [PMID: 15681451 PMCID: PMC546574 DOI: 10.1128/jvi.79.4.2506-2516.2005] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Accepted: 09/23/2004] [Indexed: 11/20/2022] Open
Abstract
The generation of subgenomic mRNAs in coronavirus involves a discontinuous mechanism of transcription by which the common leader sequence, derived from the genome 5' terminus, is fused to the 5' end of the mRNA coding sequence (body). Transcription-regulating sequences (TRSs) precede each gene and include a conserved core sequence (CS) surrounded by relatively variable sequences (5' TRS and 3' TRS). Regulation of transcription in coronaviruses has been studied by reverse-genetics analysis of the sequences immediately flanking a unique CS in the Transmissible gastroenteritis virus genome (CS-S2), located inside the S gene, that does not lead to detectable amounts of the corresponding mRNA, in spite of its canonical sequence. The transcriptional inactivity of CS-S2 was genome position independent. The presence of a canonical CS was not sufficient to drive transcription, but subgenomic synthesis requires a minimum base pairing between the leader TRS (TRS-L) and the complement of the body TRS (cTRS-B) provided by the CS and its adjacent nucleotides. A good correlation was observed between the free energy of TRS-L and cTRS-B duplex formation and the levels of subgenomic mRNA S2, demonstrating that base pairing between the leader and body beyond the CS is a determinant regulation factor in coronavirus transcription. In TRS mutants with increasing complementarity between TRS-L and cTRS-B, a tendency to reach a plateau in DeltaG values was observed, suggesting that a more precise definition of the TRS limits might be proposed, specifically that it consists of the central CS and around 4 nucleotides flanking 5' and 3' the CS. Sequences downstream of the CS exert a stronger influence on the template-switching decision according to a model of polymerase strand transfer and template switching during minus-strand synthesis.
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Affiliation(s)
- Isabel Sola
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain
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22
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Enjuanes L, Sola I, Alonso S, Escors D, Zúñiga S. Coronavirus reverse genetics and development of vectors for gene expression. Curr Top Microbiol Immunol 2005; 287:161-97. [PMID: 15609512 PMCID: PMC7120368 DOI: 10.1007/3-540-26765-4_6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/23/2023]
Abstract
Knowledge of coronavirus replication, transcription, and virus-host interaction has been recently improved by engineering of coronavirus infectious cDNAs. With the transmissible gastroenteritis virus (TGEV) genome the efficient (>40 microg per 106 cells) and stable (>20 passages) expression of the foreign genes has been shown. Knowledge of the transcription mechanism in coronaviruses has been significantly increased, making possible the fine regulation of foreign gene expression. A new family of vectors based on single coronavirus genomes, in which essential genes have been deleted, has emerged including replication-competent, propagation-deficient vectors. Vector biosafety is being increased by relocating the RNA packaging signal to the position previously occupied by deleted essential genes, to prevent the rescue of fully competent viruses that might arise from recombination events with wild-type field coronaviruses. The large cloning capacity of coronaviruses (>5 kb) and the possibility of engineering the tissue and species tropism to target expression to different organs and animal species, including humans, has increased the potential of coronaviruses as vectors for vaccine development and, possibly, gene therapy.
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Affiliation(s)
- L Enjuanes
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma, 28049 Cantoblanco, Madrid, Spain.
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23
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Pasternak AO, Spaan WJM, Snijder EJ. Regulation of relative abundance of arterivirus subgenomic mRNAs. J Virol 2004; 78:8102-13. [PMID: 15254182 PMCID: PMC446141 DOI: 10.1128/jvi.78.15.8102-8113.2004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2003] [Accepted: 03/22/2004] [Indexed: 11/20/2022] Open
Abstract
The subgenomic (sg) mRNAs of arteriviruses (order Nidovirales) form a 5'- and 3'-coterminal nested set with the viral genome. Their 5' common leader sequence is derived from the genomic 5'-proximal region. Fusion of sg RNA leader and "body" segments involves a discontinuous transcription step. Presumably during minus-strand synthesis, the nascent RNA strand is transferred from one site in the genomic template to another, a process guided by conserved transcription-regulating sequences (TRSs) at these template sites. Subgenomic RNA species are produced in different but constant molar ratios, with the smallest RNAs usually being most abundant. Factors thought to influence sg RNA synthesis are size differences between sg RNA species, differences in sequence context between body TRSs, and the mutual influence (or competition) between strand transfer reactions occurring at different body TRSs. Using an Equine arteritis virus infectious cDNA clone, we investigated how body TRS activity affected sg RNA synthesis from neighboring body TRSs. Flanking sequences were standardized by head-to-tail insertion of several copies of an RNA7 body TRS cassette. A perfect gradient of sg RNA abundance, progressively favoring smaller RNA species, was observed. Disruption of body TRS function by mutagenesis did not have a significant effect on the activity of other TRSs. However, deletion of body TRS-containing regions enhanced synthesis of sg RNAs from upstream TRSs but not of those produced from downstream TRSs. The results of this study provide considerable support for the proposed discontinuous extension of minus-strand RNA synthesis as a crucial step in sg RNA synthesis.
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Affiliation(s)
- Alexander O Pasternak
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
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24
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Curtis KM, Yount B, Sims AC, Baric RS. Reverse genetic analysis of the transcription regulatory sequence of the coronavirus transmissible gastroenteritis virus. J Virol 2004; 78:6061-6. [PMID: 15141005 PMCID: PMC415797 DOI: 10.1128/jvi.78.11.6061-6066.2004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Coronavirus discontinuous transcription uses a highly conserved sequence (CS) in the joining of leader and body RNAs. Using a full-length infectious construct of transmissable gastroenteritis virus, the present study demonstrates that subgenomic transcription is heavily influenced by upstream flanking sequences and supports a mechanism of transcription attenuation that is regulated in part by a larger domain composed of primarily upstream flanking sequences which select appropriately positioned CS elements for synthesis of subgenomic RNAs.
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Affiliation(s)
- Kristopher M Curtis
- Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7435, USA.
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25
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de Haan CAM, van Genne L, Stoop JN, Volders H, Rottier PJM. Coronaviruses as vectors: position dependence of foreign gene expression. J Virol 2003; 77:11312-23. [PMID: 14557617 PMCID: PMC229330 DOI: 10.1128/jvi.77.21.11312-11323.2003] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2003] [Accepted: 08/05/2003] [Indexed: 01/12/2023] Open
Abstract
Coronaviruses are the enveloped, positive-stranded RNA viruses with the largest RNA genomes known. Several features make these viruses attractive as vaccine and therapeutic vectors: (i) deletion of their nonessential genes is strongly attenuating; (ii) the genetic space thus created allows insertion of foreign information; and (iii) their tropism can be modified by manipulation of the viral spike. We studied here their ability to serve as expression vectors by inserting two different foreign genes and evaluating systematically the genomic position dependence of their expression, using a murine coronavirus as a model. Renilla and firefly luciferase expression cassettes, each provided with viral transcription regulatory sequences (TRSs), were inserted at several genomic positions, both independently in different viruses and combined within one viral genome. Recombinant viruses were generated by using a convenient method based on targeted recombination and host cell switching. In all cases high expression levels of the foreign genes were observed without severe effects on viral replication in vitro. The expression of the inserted gene appeared to be dependent on its genomic position, as well as on the identity of the gene. Expression levels increased when the luciferase gene was inserted closer to the 3' end of the genome. The foreign gene insertions generally reduced the expression of upstream viral genes. The results are consistent with coronavirus transcription models in which the transcription from upstream TRSs is attenuated by downstream TRSs. Altogether, our observations clearly demonstrate the potential of coronaviruses as (multivalent) expression vectors.
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Affiliation(s)
- Cornelis A M de Haan
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine and Institute of Biomembranes, Utrecht University, 3584 CL Utrecht, The Netherlands
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26
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Thiel V, Karl N, Schelle B, Disterer P, Klagge I, Siddell SG. Multigene RNA vector based on coronavirus transcription. J Virol 2003; 77:9790-8. [PMID: 12941887 PMCID: PMC224574 DOI: 10.1128/jvi.77.18.9790-9798.2003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2003] [Accepted: 06/19/2003] [Indexed: 11/20/2022] Open
Abstract
Coronavirus genomes are the largest known autonomously replicating RNAs with a size of ca. 30 kb. They are of positive polarity and are translated to produce the viral proteins needed for the assembly of an active replicase-transcriptase complex. In addition to replicating the genomic RNA, a key feature of this complex is a unique transcription process that results in the synthesis of a nested set of six to eight subgenomic mRNAs. These subgenomic mRNAs are produced in constant but nonequimolar amounts and, in general, each is translated to produce a single protein. To take advantage of these features, we have developed a multigene expression vector based on human coronavirus 229E. We have constructed a prototype RNA vector containing the 5' and 3' ends of the human coronavirus genome, the entire human coronavirus replicase gene, and three reporter genes (i.e., the chloramphenicol acetyltransferase [CAT] gene, the firefly luciferase [LUC] gene, and the green fluorescent protein [GFP] gene). Each reporter gene is located downstream of a human coronavirus transcription-associated sequence, which is required for the synthesis of individual subgenomic mRNAs. The transfection of vector RNA and human coronavirus nucleocapsid protein mRNA into BHK-21 cells resulted in the expression of the CAT, LUC, and GFP reporter proteins. Sequence analysis confirmed the synthesis of coronavirus-specific mRNAs encoding CAT, LUC, and GFP. In addition, we have shown that human coronavirus-based vector RNA can be packaged into virus-like particles that, in turn, can be used to transduce immature and mature human dendritic cells. In summary, we describe a new class of eukaryotic, multigene expression vectors that are based on the human coronavirus 229E and have the ability to transduce human dendritic cells.
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Affiliation(s)
- Volker Thiel
- Institute of Virology and Immunology, University of Würzburg, Würzburg, Germany.
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27
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Xu J, Hu J, Wang J, Han Y, Hu Y, Wen J, Li Y, Ji J, Ye J, Zhang Z, Wei W, Li S, Wang J, Wang J, Yu J, Yang H. Genome organization of the SARS-CoV. GENOMICS, PROTEOMICS & BIOINFORMATICS 2003; 1:226-35. [PMID: 15629035 PMCID: PMC5172239 DOI: 10.1016/s1672-0229(03)01028-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Annotation of the genome sequence of the SARS-CoV (severe acute respiratory syndrome-associated coronavirus) is indispensable to understand its evolution and pathogenesis. We have performed a full annotation of the SARS-CoV genome sequences by using annotation programs publicly available or developed by ourselves. Totally, 21 open reading frames (ORFs) of genes or putative uncharacterized proteins (PUPs) were predicted. Seven PUPs had not been reported previously, and two of them were predicted to contain transmembrane regions. Eight ORFs partially overlapped with or embedded into those of known genes, revealing that the SARS-CoV genome is a small and compact one with overlapped coding regions. The most striking discovery is that an ORF locates on the minus strand. We have also annotated non-coding regions and identified the transcription regulating sequences (TRS) in the intergenic regions. The analysis of TRS supports the minus strand extending transcription mechanism of coronavirus. The SNP analysis of different isolates reveals that mutations of the sequences do not affect the prediction results of ORFs.
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Affiliation(s)
- Jing Xu
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
| | - Jianfei Hu
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
- College of Life Sciences, Peking University, Beijing 100871, China
| | - Jing Wang
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
- College of Life Sciences, Peking University, Beijing 100871, China
| | - Yujun Han
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
| | - Yongwu Hu
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
- Wenzhou Medical College, Wenzhou 325003, China
| | - Jie Wen
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
| | - Yan Li
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
| | - Jia Ji
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
| | - Jia Ye
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
- James D. Watson Institute of Genome Sciences, Zhijiang Campus, Zhejiang University and Hangzhou Genomics Institute, Hangzhou 310008, China
| | - Zizhang Zhang
- College of Materials Science and Chemical Engineering, Yuquan Campus, Zhejiang University, Hangzhou 310027, China
| | - Wei Wei
- James D. Watson Institute of Genome Sciences, Zhijiang Campus, Zhejiang University and Hangzhou Genomics Institute, Hangzhou 310008, China
| | - Songgang Li
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
- College of Life Sciences, Peking University, Beijing 100871, China
| | - Jun Wang
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
| | - Jian Wang
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
- James D. Watson Institute of Genome Sciences, Zhijiang Campus, Zhejiang University and Hangzhou Genomics Institute, Hangzhou 310008, China
| | - Jun Yu
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
- James D. Watson Institute of Genome Sciences, Zhijiang Campus, Zhejiang University and Hangzhou Genomics Institute, Hangzhou 310008, China
| | - Huanming Yang
- Beijing Genomics Institute, Chinese Academy of Sciences, Beijing 101300, China
- James D. Watson Institute of Genome Sciences, Zhijiang Campus, Zhejiang University and Hangzhou Genomics Institute, Hangzhou 310008, China
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28
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Sola I, Alonso S, Zúñiga S, Balasch M, Plana-Durán J, Enjuanes L. Engineering the transmissible gastroenteritis virus genome as an expression vector inducing lactogenic immunity. J Virol 2003; 77:4357-69. [PMID: 12634392 PMCID: PMC150661 DOI: 10.1128/jvi.77.7.4357-4369.2003] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2002] [Accepted: 01/07/2003] [Indexed: 11/20/2022] Open
Abstract
The genome of the coronavirus transmissible gastroenteritis virus (TGEV) has been engineered as an expression vector with an infectious cDNA. The vector led to the efficient (>40 micro g/10(6) cells) and stable (>20 passages) expression of a heterologous gene (green fluorescent protein [GFP]), driven by the transcription-regulating sequences (TRS) of open reading frame (ORF) 3a inserted in the site previously occupied by the nonessential ORFs 3a and 3b. Expression levels driven by this TRS were higher than those of an expression cassette under the control of regulating sequences engineered with the N gene TRS. The recombinant TGEV including the GFP gene was still enteropathogenic, albeit with a 10- to 10(2)-fold reduction in enteric tissue growth. Interestingly, a specific lactogenic immune response against the heterologous protein has been elicited in sows and their progeny. The engineering of an additional insertion site for the heterologous gene between viral genes N and 7 led to instability and to a new genetic organization of the 3' end of the recombinant viruses. As a consequence, a major species of subgenomic mRNA was generated from a TRS with the noncanonical core sequence 5'-CUAAAA-3'. Extension of the complementarity between the TRS and sequences at the 3' end of the viral leader was associated with transcriptional activation of noncanonical core sequences. The engineered vector led to expression levels as high as those of well-established vectors and seems very promising for the development of vaccines and, possibly, for gene therapy.
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Affiliation(s)
- Isabel Sola
- Centro Nacional de Biotecnología, CSIC, Department of Molecular and Cell Biology, Campus Universidad Autónoma, Cantoblanco, Madrid, Spain
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29
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Pasternak AO, van den Born E, Spaan WJM, Snijder EJ. The stability of the duplex between sense and antisense transcription-regulating sequences is a crucial factor in arterivirus subgenomic mRNA synthesis. J Virol 2003; 77:1175-83. [PMID: 12502834 PMCID: PMC140805 DOI: 10.1128/jvi.77.2.1175-1183.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2002] [Accepted: 10/07/2002] [Indexed: 11/20/2022] Open
Abstract
Subgenomic mRNAs of nidoviruses (arteriviruses and coronaviruses) are composed of a common leader sequence and a "body" part of variable size, which are derived from the 5'- and 3'-proximal part of the genome, respectively. Leader-to-body joining has been proposed to occur during minus-strand RNA synthesis and to involve transfer of the nascent RNA strand from one site in the template to another. This discontinuous step in subgenomic RNA synthesis is guided by short transcription-regulating sequences (TRSs) that are present at both these template sites (leader TRS and body TRS). Sense-antisense base pairing between the leader TRS in the plus strand and the body TRS complement in the minus strand is crucial for strand transfer. Here we show that extending the leader TRS-body TRS duplex beyond its wild-type length dramatically enhanced the subgenomic mRNA synthesis of the arterivirus Equine arteritis virus (EAV). Generally, the relative amount of a subgenomic mRNA correlated with the calculated stability of the corresponding leader TRS-body TRS duplex. In addition, various leader TRS mutations induced the generation of minor subgenomic RNA species that were not detected upon infection with wild-type EAV. The synthesis of these RNA species involved leader-body junction events at sites that bear only limited resemblance to the canonical TRS. However, with the mutant leader TRS, but not with the wild-type leader TRS, these sequences could form a duplex that was stable enough to direct subgenomic RNA synthesis, again demonstrating that the stability of the leader TRS-body TRS duplex is a crucial factor in arterivirus subgenomic mRNA synthesis.
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Affiliation(s)
- Alexander O Pasternak
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, The Netherlands
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30
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de Haan CAM, Volders H, Koetzner CA, Masters PS, Rottier PJM. Coronaviruses maintain viability despite dramatic rearrangements of the strictly conserved genome organization. J Virol 2002; 76:12491-502. [PMID: 12438575 PMCID: PMC136672 DOI: 10.1128/jvi.76.24.12491-12502.2002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2002] [Accepted: 09/03/2002] [Indexed: 01/16/2023] Open
Abstract
Despite their high frequency of RNA recombination, the plus-strand coronaviruses have a characteristic, strictly conserved genome organization with the essential genes occurring in the order 5'-polymerase (pol)-S-E-M-N-3'. We have investigated the significance of this remarkable conservation by rearrangement of the murine coronavirus genome through targeted recombination. Thus, viruses were prepared with the following gene order: 5'-pol-S-M-E-N-3', 5'-pol-S-N-E-M-3', 5'-pol-M-S-E-N-3', and 5'-pol-E-M-S-N-3'. All of these viruses were surprisingly viable, and most viruses replicated in cell culture with growth characteristics similar to those of the parental virus. The recombinant virus with the gene order 5'-pol-E-M-S-N-3' was also tested for the ability to replicate in the natural host, the mouse. The results indicate that the canonical coronavirus genome organization is not essential for replication in vitro and in vivo. Deliberate rearrangement of the viral genes may be useful in the generation of attenuated coronaviruses, which due to their reduced risk of generating viable viruses by recombination with circulating field viruses, would make safer vaccines.
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Affiliation(s)
- Cornelis A M de Haan
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, and Institute of Biomembranes, Utrecht University, Yalelaan 1, 3584 CL Utrecht, The Netherlands.
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31
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Molenkamp R, Rozier BC, Greve S, Spaan WJ, Snijder EJ. Characterization of an arterivirus defective interfering RNA. Replication and homologous recombination. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 494:519-25. [PMID: 11774517 DOI: 10.1007/978-1-4615-1325-4_75] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- R Molenkamp
- Department of Virology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
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32
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Enjuanes L, Sola I, Almazan F, Izeta A, Gonzalez JM, Alonso S. Coronavirus derived expression systems. Progress and problems. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 494:309-21. [PMID: 11774485 DOI: 10.1007/978-1-4615-1325-4_47] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- L Enjuanes
- Centro Nacional de Biotecnología, CSIC, Department of Molecular and Cell Biology, Campus Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain
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33
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Brian DA. Nidovirus genome replication and subgenomic mRNA synthesis. Pathways followed and cis-acting elements required. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 494:415-28. [PMID: 11774502 DOI: 10.1007/978-1-4615-1325-4_62] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- D A Brian
- Department of Microbiology, University of Tennessee, Knoxville, TN, USA
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34
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de Vries AAF, Horzinek MC, Rottier PJM, de Groot RJ. The Genome Organization of the Nidovirales: Similarities and Differences between Arteri-, Toro-, and Coronaviruses. ACTA ACUST UNITED AC 2002; 8:33-47. [PMID: 32288441 PMCID: PMC7128191 DOI: 10.1006/smvy.1997.0104] [Citation(s) in RCA: 196] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Viruses in the families Arteriviridae and Coronaviridae have enveloped virions which contain nonsegmented, positive-stranded RNA, but the constituent genera differ markedly in genetic complexity and virion structure. Nevertheless, there are striking resemblances among the viruses in the organization and expression of their genomes, and sequence conservation among the polymerase polyproteins strongly suggests that they have a common ancestry. On this basis, the International Committee on Taxonomy of Viruses recently established a new order, Nidovirales, to contain the two families. Here, the common traits and distinguishing features of the Nidovirales are reviewed.
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Affiliation(s)
- Antoine A F de Vries
- Virology Unit, Department of Infectious Diseases and Immunology, Veterinary Faculty, Utrecht University, Yalelaan 1, 3584 CL, Utrecht, The Netherlands
| | - Marian C Horzinek
- Virology Unit, Department of Infectious Diseases and Immunology, Veterinary Faculty, Utrecht University, Yalelaan 1, 3584 CL, Utrecht, The Netherlands
| | - Peter J M Rottier
- Virology Unit, Department of Infectious Diseases and Immunology, Veterinary Faculty, Utrecht University, Yalelaan 1, 3584 CL, Utrecht, The Netherlands
| | - Raoul J de Groot
- Virology Unit, Department of Infectious Diseases and Immunology, Veterinary Faculty, Utrecht University, Yalelaan 1, 3584 CL, Utrecht, The Netherlands
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35
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Abstract
Naturally occurring defective interfering RNAs have been found in 4 of 14 coronavirus species. They range in size from 2.2 kb to approximately 25 kb, or 80% of the 30-kb parent virus genome. The large DI RNAs do not in all cases appear to require helper virus for intracellular replication and it has been postulated that they may on their own function as agents of disease. Coronavirus DI RNAs appear to arise by internal deletions (through nonhomologous recombination events) on the virus genome or on DI RNAs of larger size by a polymerase strand-switching (copy-choice) mechanism. In addition to their use in the study of virus RNA replication and virus assembly, coronavirus DI RNAs are being used in a major way to study the mechanism of a high-frequency, site-specific RNA recombination event that leads to leader acquisition during virus replication (i.e., the leader fusion event that occurs during synthesis of subgenomic mRNAs, and the leader-switching event that can occur during DI RNA replication), a distinguishing feature of coronaviruses (and arteriviruses). Coronavirus DI RNAs are also being engineered as vehicles for the generation of targeted recombinants of the parent virus genome.
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Affiliation(s)
- David A Brian
- Department of Microbiology, College of Veterinary Medicine, M409 Walters Life Sciences Building, University of Tennessee, Knoxville, Tennessee, 37996-0845
| | - Willy J M Spaan
- Department of Virology, Institute of Medical Microbiology, Leiden University, 2300, RC Leiden, The Netherlands
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36
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Peremyslov VV, Dolja VV. Identification of the subgenomic mRNAs that encode 6-kDa movement protein and Hsp70 homolog of Beet yellows virus. Virology 2002; 295:299-306. [PMID: 12033789 DOI: 10.1006/viro.2002.1396] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A tandem arrangement of the genes encoding the approximately 6-kDa hydrophobic protein (p6) and Hsp70 homolog (Hsp70h) is conserved among the members of the Closterovirus genus. It was not known, however, if these movement proteins are expressed from one or two subgenomic (sg) RNAs. Here we employ RNA ligase-mediated RACE to show that the Beet yellows virus (BYV), a prototype Closterovius, produces separate sgRNAs encoding p6 and Hsp70h. This result is further supported by generation of the recombinant BYV in which the truncated variants of these sgRNAs are resolved by Northern analysis. The 5'-termini of the p6 and Hsp70h sgRNAs are localized to BYV nucleotides G-9402 and A-9467, respectively. Each of the sgRNAs was generated in vitro and found to direct the expected product upon translation in wheat germ extract. Inactivation of the first start codons in these sgRNAs abolished translation of the each product. The polyclonal antibodies raised to synthetic C-terminal peptides of p6 and Hsp70h specifically recognized corresponding translation products, as well as p6 and Hsp70h produced in BYV-infected plants. Taken together with the previous work, our data demonstrate that expression of the BYV genome involves the formation of as many as seven sgRNAs.
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Affiliation(s)
- Valera V Peremyslov
- Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331, USA
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37
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Verheije MH, Olsthoorn RCL, Kroese MV, Rottier PJM, Meulenberg JJM. Kissing interaction between 3' noncoding and coding sequences is essential for porcine arterivirus RNA replication. J Virol 2002; 76:1521-6. [PMID: 11773426 PMCID: PMC135790 DOI: 10.1128/jvi.76.3.1521-1526.2002] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We used an infectious cDNA clone of porcine reproductive and respiratory syndrome virus (PRRSV) to investigate the presence of essential replication elements in the region of the genome encoding the structural proteins. Deletion analysis showed that a stretch of 34 nucleotides (14653 to 14686) within ORF7, which encodes the nucleocapsid protein, is essential for RNA replication. Strand-specific reverse transcription-PCR analysis of viral RNA isolated from transfected BHK-21 cells revealed that this region is required for negative-strand genomic RNA synthesis. The 34-nucleotide stretch is highly conserved among PRRSV isolates and folds into a putative hairpin. A 7-base sequence within the loop of this structure was suggested to base-pair with a sequence present in the loop of a hairpin located in the 3' noncoding region, resulting in a kissing interaction. Mutational analyses confirmed that this kissing interaction is required for RNA replication.
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Affiliation(s)
- M H Verheije
- Department of Infectious Diseases and Food Chain Quality, Institute for Animal Science and Health, Lelystad, The Netherlands.
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38
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Ozdarendeli A, Ku S, Rochat S, Williams GD, Senanayake SD, Brian DA. Downstream sequences influence the choice between a naturally occurring noncanonical and closely positioned upstream canonical heptameric fusion motif during bovine coronavirus subgenomic mRNA synthesis. J Virol 2001; 75:7362-74. [PMID: 11462008 PMCID: PMC114971 DOI: 10.1128/jvi.75.16.7362-7374.2001] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2001] [Accepted: 05/16/2001] [Indexed: 11/20/2022] Open
Abstract
Mechanisms leading to subgenomic mRNA (sgmRNA) synthesis in coronaviruses are poorly understood but are known to involve a heptameric signaling motif, originally called the intergenic sequence. The intergenic sequence is the presumed crossover region (fusion site) for RNA-dependent RNA polymerase (RdRp) during discontinuous transcription, a process leading to sgmRNAs that are both 5' and 3' coterminal. In the bovine coronavirus, the major fusion site for synthesis of mRNA 5 (GGUAGAC) does not conform to the canonical motif (UC[U,C]AAAC) at three positions (underlined), yet it lies just 14 nucleotides downstream from such a sequence (UCCAAAC). The infrequently used canonical sequence, by computer prediction, is buried within the stem of a stable hairpin (-17.2 kcal/mol). Here we document the existence of this stem by enzyme probing and examine its influence and that of neighboring sequences on the unusual choice of fusion sites by analyzing transcripts made in vivo from mutated defective interfering RNA constructs. We learned that (i) mutations that were predicted to unfold the stem-loop in various ways did not switch RdRp crossover to the upstream canonical site, (ii) a totally nonconforming downstream motif resulted in no measurable transcription from either site, (iii) the canonical upstream site does not function ectopically to lend competence to the downstream noncanonical site, and (iv) altering flanking sequences downstream of the downstream noncanonical motif in ways that diminish sequence similarity with the virus genome 5' end caused a dramatic switch to the upstream canonical site. These results show that sequence elements downstream of the noncanonical site can dramatically influence the choice of fusion sites for synthesis of mRNA 5 and are interpreted as being most consistent with a mechanism of similarity-assisted RdRp strand switching during minus-strand synthesis.
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Affiliation(s)
- A Ozdarendeli
- Department of Microbiology, University of Tennessee, College of Veterinary Medicine, Knoxville, Tennessee 37996-0845, USA
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39
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Enjuanes L, Sola I, Almazan F, Ortego J, Izeta A, Gonzalez JM, Alonso S, Sanchez JM, Escors D, Calvo E, Riquelme C, Sanchez C. Coronavirus derived expression systems. J Biotechnol 2001; 88:183-204. [PMID: 11434966 PMCID: PMC7126887 DOI: 10.1016/s0168-1656(01)00281-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Both helper dependent expression systems, based on two components, and single genomes constructed by targeted recombination, or by using infectious cDNA clones, have been developed. The sequences that regulate transcription have been characterized mainly using helper dependent expression systems and it will now be possible to validate them using single genomes. The genome of coronaviruses has been engineered by modification of the infectious cDNA leading to an efficient (>20 microg ml(-1)) and stable (>20 passages) expression of the foreign gene. The possibility of engineering the tissue and species tropism to target expression to different organs and animal species, including humans, increases the potential of coronaviruses as vectors. Thus, coronaviruses are promising virus vectors for vaccine development and, possibly, for gene therapy.
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Affiliation(s)
- L Enjuanes
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma, Cantoblanco, 28049, Madrid, Spain.
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40
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Thiel V, Herold J, Schelle B, Siddell SG. Viral replicase gene products suffice for coronavirus discontinuous transcription. J Virol 2001; 75:6676-81. [PMID: 11413334 PMCID: PMC114390 DOI: 10.1128/jvi.75.14.6676-6681.2001] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2001] [Accepted: 04/23/2001] [Indexed: 12/23/2022] Open
Abstract
We have used vaccinia virus as a vector to clone a 22.5-kbp cDNA that represents the 5' and 3' ends of the human coronavirus 229E (HCoV 229E) genome, the HCoV 229E replicase gene, and a single reporter gene (coding for green fluorescent protein [GFP]) located downstream of a regulatory element for coronavirus mRNA transcription. When RNA transcribed from this cDNA was transfected into BHK-21 cells, a small percentage of cells displayed strong fluorescence. A region of the mRNA encoding GFP was amplified by PCR and shown to have the unique mRNA leader-body junction indicative of coronavirus-mediated transcription. These data show that the coronavirus replicase gene products suffice for discontinuous subgenomic mRNA transcription.
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Affiliation(s)
- V Thiel
- Institute of Virology and Immunology, University of Würzburg, 97078 Würzburg, Germany.
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41
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de Vries AA, Glaser AL, Raamsman MJ, Rottier PJ. Recombinant equine arteritis virus as an expression vector. Virology 2001; 284:259-76. [PMID: 11384225 DOI: 10.1006/viro.2001.0908] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Equine arteritis virus (EAV) is the prototypic member of the family Arteriviridae, which together with the Corona- and Toroviridae constitutes the order Nidovirales. A common trait of these positive-stranded RNA viruses is the 3'-coterminal nested set of six to eight leader-containing subgenomic mRNAs which are generated by a discontinuous transcription mechanism and from which the viral open reading frames downstream of the polymerase gene are expressed. In this study, we investigated whether the unique gene expression strategy of the Nidovirales could be utilized to convert them into viral expression vectors by introduction of an additional transcription unit into the EAV genome directing the synthesis of an extra subgenomic mRNA. To this end, an expression cassette consisting of the gene for a green fluorescent protein (GFP) flanked at its 3' end by EAV-specific transcription-regulating sequences was constructed. This genetic module was inserted into the recently obtained mutant infectious EAV cDNA clone pBRNX1.38-5/6 (A. A. F. de Vries, et al., 2000, Virology 270, 84-97) between the genes for the M and the G(L) proteins. Confocal fluorescence microscopy of BHK-21 cells electroporated with capped RNA transcripts derived from the resulting plasmid (pBRNX1.38-5/6-GFP) demonstrated that the GFP gene was expressed in the transfected cells, while the gradual spread of the infection through the cell monolayer showed that the recombinant virus was replication competent. The development of the cytopathic effect was, however, much slower than in cells that had received equivalent amounts of pBRNX1.38-5/6 RNA, indicating that the vector virus had a clear growth disadvantage compared to its direct precursor. Immunoprecipitation analyses of proteins from metabolically labeled BHK-21 cells infected with supernatant of the transfected cultures confirmed that the recombinant virus vector was viable and expressed viral genes as well as the GFP gene. Reverse transcription-PCR of the viral mRNAs extracted from cells infected with the vector virus revealed that it directed the synthesis of nine instead of eight different EAV RNAs. These findings were corroborated by hybridization analyses. Mapping of the leader-to-body junctions of the ninth mRNA indicated that the 3' part of the GFP gene contains cryptic transcription signals which gave rise to at least five different RNA species ranging in size from 1277 to 1439 nt [without oligo(A) tract]. Furthermore, translation of the unintended mRNA resulted in the production of an extended version of the EAV M protein. Serial passage of the recombinant virus vector led to its gradual replacement by viral mutants carrying deletions in the GFP gene. The reduction in viral fitness associated with the insertion of the expression cassette into the EAV genome apparently caused genetic instability of the recombinant virus.
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Affiliation(s)
- A A de Vries
- Virology Division, Department of Infectious Diseases and Immunology, Veterinary Faculty, Utrecht University, Yalelaan 1, Utrecht, 3584 CL, The Netherlands
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Lee YS, Hsu YH, Lin NS. Generation of subgenomic RNA directed by a satellite RNA associated with bamboo mosaic potexvirus: analyses of potexvirus subgenomic RNA promoter. J Virol 2000; 74:10341-8. [PMID: 11044078 PMCID: PMC110908 DOI: 10.1128/jvi.74.22.10341-10348.2000] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2000] [Accepted: 08/15/2000] [Indexed: 11/20/2022] Open
Abstract
Satellite RNA of bamboo mosaic potexvirus (satBaMV), a single-stranded positive-sense RNA encoding a nonstructural protein of 20 kDa (P20), depends on bamboo mosaic potexvirus (BaMV) for replication and encapsidation. A full-length cDNA clone of satBaMV was used to examine the sequences required for the synthesis of potexvirus subgenomic RNAs (sgRNAs). Subgenomic promoter-like sequences (SGPs), 107 nucleotides (nt) upstream from the capsid protein (CP) gene of BaMV-V, were inserted upstream of the start codon of the P20 gene of satBaMV. Insertion of SGPs gave rise to the synthesis of sgRNA of satBaMV in protoplasts of Nicotiana benthamiana and leaves of Chenopodium quinoa when coinoculated with BaMV-V genomic RNA. Moreover, both the satBaMV cassette and its sgRNA were encapsidated. From analysis of the SGPs by deletion mutation, we concluded that an SGP contains one core promoterlike sequence (nt -30 through +16), two upstream enhancers (nt -59 through -31 and -91 through -60), and one downstream enhancer (nt +17 through +52), when the transcription initiation site is taken as +1. Site-directed mutagenesis and compensatory mutation to disrupt and restore potential base pairing in the core promoter-like sequence suggest that the stem-loop structure is important for the function of SGP in vivo. Likewise, the insertion of a putative SGP of the BaMV open reading frame 2 gene or a heterologous SGP of potato virus X resulted in generation of an sgRNA. The satBaMV cassette should be a useful tool to gain insight into sequences required for the synthesis of potexvirus sgRNAs.
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Affiliation(s)
- Y S Lee
- Institute of Botany, Academia Sinica, Taipei, Taiwan
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43
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Molenkamp R, Greve S, Spaan WJ, Snijder EJ. Efficient homologous RNA recombination and requirement for an open reading frame during replication of equine arteritis virus defective interfering RNAs. J Virol 2000; 74:9062-70. [PMID: 10982351 PMCID: PMC102103 DOI: 10.1128/jvi.74.19.9062-9070.2000] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2000] [Accepted: 07/10/2000] [Indexed: 11/20/2022] Open
Abstract
Equine arteritis virus (EAV), the prototype arterivirus, is an enveloped plus-strand RNA virus with a genome of approximately 13 kb. Based on similarities in genome organization and protein expression, the arteriviruses have recently been grouped together with the coronaviruses and toroviruses in the newly established order Nidovirales. Previously, we reported the construction of pEDI, a full-length cDNA copy of EAV DI-b, a natural defective interfering (DI) RNA of 5.6 kb (R. Molenkamp et al., J. Virol. 74:3156-3165, 2000). EDI RNA consists of three noncontiguous parts of the EAV genome fused in frame with respect to the replicase gene. As a result, EDI RNA contains a truncated replicase open reading frame (EDI-ORF) and encodes a truncated replicase polyprotein. Since some coronavirus DI RNAs require the presence of an ORF for their efficient propagation, we have analyzed the importance of the EDI-ORF in EDI RNA replication. The EDI-ORF was disrupted at different positions by the introduction of frameshift mutations. These were found either to block DI RNA replication completely or to be removed within one virus passage, probably due to homologous recombination with the helper virus genome. Using recombination assays based on EDI RNA and full-length EAV genomes containing specific mutations, the rates of homologous RNA recombination in the 3'- and 5'-proximal regions of the EAV genome were studied. Remarkably, the recombination frequency in the 5'-proximal region was found to be approximately 100-fold lower than that in the 3'-proximal part of the genome.
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Affiliation(s)
- R Molenkamp
- Department of Virology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
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MESH Headings
- Genes, Viral/genetics
- Genome, Viral
- Models, Genetic
- Nucleic Acid Conformation
- Promoter Regions, Genetic/genetics
- RNA Viruses/genetics
- RNA, Messenger/biosynthesis
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Viral/biosynthesis
- RNA, Viral/chemistry
- RNA, Viral/genetics
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Affiliation(s)
- W A Miller
- Plant Pathology Department, Iowa State University, Ames, Iowa, 50011, USA
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Stirrups K, Shaw K, Evans S, Dalton K, Casais R, Cavanagh D, Britton P. Expression of reporter genes from the defective RNA CD-61 of the coronavirus infectious bronchitis virus. J Gen Virol 2000; 81:1687-98. [PMID: 10859373 DOI: 10.1099/0022-1317-81-7-1687] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
The defective RNA (D-RNA) CD-61, derived from the Beaudette strain of the avian coronavirus infectious bronchitis virus (IBV), was used as an RNA vector for the expression of two reporter genes, luciferase and chloramphenicol acetyltransferase (CAT). D-RNAs expressing the CAT gene were demonstrated to be capable of producing CAT protein in a helper-dependent expression system to about 1.6 microgram per 10(6) cells. The reporter genes were expressed from two different sites within the CD-61 sequence and expression was not affected by interruption of the CD-61-specific ORF. Expression of the reporter genes was under the control of a transcription-associated sequence (TAS) derived from the Beaudette gene 5, normally used for the transcription of IBV subgenomic mRNA 5. The Beaudette gene 5 TAS is composed of two tandem repeats of the IBV canonical consensus sequence involved in the acquisition of a leader sequence during the discontinuous transcription of IBV subgenomic mRNAs. It is demonstrated that only one canonical sequence is required for expression of mRNA 5 or for the expression of an mRNA from a D-RNA and that either sequence can function as an acceptor site for acquisition of the leader sequence.
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Affiliation(s)
- K Stirrups
- Division of Molecular Biology, Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN, UK
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46
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Koev G, Miller WA. A positive-strand RNA virus with three very different subgenomic RNA promoters. J Virol 2000; 74:5988-96. [PMID: 10846080 PMCID: PMC112095 DOI: 10.1128/jvi.74.13.5988-5996.2000] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/1999] [Accepted: 04/16/2000] [Indexed: 01/19/2023] Open
Abstract
Numerous RNA viruses generate subgenomic mRNAs (sgRNAs) for expression of their 3'-proximal genes. A major step in control of viral gene expression is the regulation of sgRNA synthesis by specific promoter elements. We used barley yellow dwarf virus (BYDV) as a model system to study transcriptional control in a virus with multiple sgRNAs. BYDV generates three sgRNAs during infection. The sgRNA1 promoter has been mapped previously to a 98-nucleotide (nt) region which forms two stem-loop structures. It was determined that sgRNA1 is not required for BYDV RNA replication in oat protoplasts. In this study, we show that neither sgRNA2 nor sgRNA3 is required for BYDV RNA replication. The promoters for sgRNA2 and sgRNA3 synthesis were mapped by using deletion mutagenesis. The minimal sgRNA2 promoter is approximately 143 nt long (nt 4810 to 4952) and is located immediately downstream of the putative sgRNA2 start site (nt 4809). The minimal sgRNA3 core promoter is 44 nt long (nt 5345 to 5388), with most of the sequence located downstream of sgRNA3 start site (nt 5348). For both promoters, additional sequences upstream of the start site enhanced sgRNA promoter activity. These promoters contrast to the sgRNA1 promoter, in which almost all of the promoter is located upstream of the transcription initiation site. Comparison of RNA sequences and computer-predicted secondary structures revealed little or no homology between the three sgRNA promoter elements. Thus, a small RNA virus with multiple sgRNAs can have very different subgenomic promoters, which implies a complex system for promoter recognition and regulation of subgenomic RNA synthesis.
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Affiliation(s)
- G Koev
- Plant Pathology Department, Iowa State University, Ames 50011-1020, USA
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Molenkamp R, Rozier BC, Greve S, Spaan WJ, Snijder EJ. Isolation and characterization of an arterivirus defective interfering RNA genome. J Virol 2000; 74:3156-65. [PMID: 10708432 PMCID: PMC111816 DOI: 10.1128/jvi.74.7.3156-3165.2000] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/1999] [Accepted: 01/05/2000] [Indexed: 11/20/2022] Open
Abstract
Equine arteritis virus (EAV), the type member of the family Arteriviridae, is a single-stranded RNA virus with a positive-stranded genome of approximately 13 kb. EAV uses a discontinuous transcription mechanism to produce a nested set of six subgenomic mRNAs from which its structural genes are expressed. We have generated the first documented arterivirus defective interfering (DI) RNAs by serial undiluted passaging of a wild-type EAV stock in BHK-21 cells. A cDNA copy of the smallest DI RNA (5.6 kb) was cloned. Upon transfection into EAV-infected BHK-21 cells, transcripts derived from this clone (pEDI) were replicated and packaged. Sequencing of pEDI revealed that the DI RNA was composed of three segments of the EAV genome (nucleotides 1 to 1057, 1388 to 1684, and 8530 to 12704) which were fused in frame with respect to the replicase reading frame. Remarkably, this DI RNA has retained all of the sequences encoding the structural proteins. By insertion of the chloramphenicol acetyltransferase reporter gene in the DI RNA genome, we were able to delimitate the sequences required for replication/DI-based transcription and packaging of EAV DI RNAs and to reduce the maximal size of a replication-competent EAV DI RNA to approximately 3 kb.
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Affiliation(s)
- R Molenkamp
- Department of Virology, Center for Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
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Nelson GW, Stohlman SA, Tahara SM. High affinity interaction between nucleocapsid protein and leader/intergenic sequence of mouse hepatitis virus RNA. J Gen Virol 2000; 81:181-8. [PMID: 10640556 DOI: 10.1099/0022-1317-81-1-181] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The nucleocapsid (N) protein of mouse hepatitis virus (MHV) is the major virion structural protein. It associates with both viral genomic RNA and subgenomic mRNAs and has structural and non-structural roles in replication including viral RNA-dependent RNA transcription, genome replication, encapsidation and translation. These processes all involve RNA-protein interactions between the N protein and viral RNAs. To better understand the RNA-binding properties of this multifunctional protein, the N protein was expressed in Escherichia coli as a chimeric protein fused to glutathione-S-transferase (GST). Biochemical analyses of RNA-binding properties were performed on full-length and partial N protein segments to define the RNA-binding domain. The full-length N protein and the GST-N protein fusion product had similar binding activities with a dissociation constant (K(d)) of 14 nM when the MHV 5'-leader sequence was used as ligand. The smallest N protein fragment which retained RNA-binding activity was a 55 aa segment containing residues 177-231 which bound viral RNA with a K(d) of 32 nM. A consensus viral sequence recognized by the N protein was inferred from these studies; AAUCYAAAC was identified to be the potential minimum ligand for the N protein. Although the core UCYAA sequence is often tandemly repeated in viral genomes, ligands containing one or more repeats of UCYAA showed no difference in binding to the N protein. Together these data demonstrate a high-affinity, specific interaction between the N protein and a conserved RNA sequence present at the 5'-ends of MHV mRNA.
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Affiliation(s)
- G W Nelson
- Departments of Molecular Microbiology and Immunology and Neurology(2), USC School of Medicine, 2011 Zonal Avenue, Los Angeles, CA 90033-1054, USA
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Hagiwara Y, Peremyslov VV, Dolja VV. Regulation of closterovirus gene expression examined by insertion of a self-processing reporter and by northern hybridization. J Virol 1999; 73:7988-93. [PMID: 10482546 PMCID: PMC112813 DOI: 10.1128/jvi.73.10.7988-7993.1999] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
A reporter open reading frame (ORF) coding for a fusion of bacterial beta-glucuronidase (GUS) with a proteinase domain (Pro) derived from tobacco etch potyvirus was utilized for tagging individual genes of beet yellows closterovirus (BYV). Insertion of this reporter ORF between the first and second codons of the BYV ORFs encoding the HSP70 homolog (HSP70h), a major capsid protein (CP), and a 20-kDa protein (p20) resulted in the expression of the processed GUS-Pro reporter from corresponding subgenomic RNAs. The high sensitivity of GUS assays permitted temporal analysis of reporter accumulation, revealing early expression from the HSP70h promoter, followed by the CP promoter and later the p20 promoter. The kinetics of transcription of the remaining BYV genes encoding a 64-kDa protein (p64), a minor capsid protein (CPm), and a 21-kDa protein (p21) were examined via Northern blot analysis. Taken together, the data indicated that the temporal regulation of BYV gene expression includes early (HSP70h, CPm, CP, and p21 promoters) and late (p64 and p20 promoters) phases. It was also demonstrated that the deletion of six viral genes that are nonessential for RNA amplification resulted in a dramatic increase in the level of transcription from one of the two remaining subgenomic promoters. Comparison with other positive-strand RNA viruses producing multiple subgenomic RNAs showed the uniqueness of the pattern of closterovirus transcriptional regulation.
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Affiliation(s)
- Y Hagiwara
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331, USA
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50
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van Marle G, van Dinten LC, Spaan WJ, Luytjes W, Snijder EJ. Characterization of an equine arteritis virus replicase mutant defective in subgenomic mRNA synthesis. J Virol 1999; 73:5274-81. [PMID: 10364273 PMCID: PMC112582 DOI: 10.1128/jvi.73.7.5274-5281.1999] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/1998] [Accepted: 03/29/1999] [Indexed: 11/20/2022] Open
Abstract
Equine arteritis virus (EAV) is a positive-stranded RNA virus that synthesizes a 5'- and 3'-coterminal nested set of six subgenomic mRNAs. These mRNAs all contain a common leader sequence which is derived from the 5' end of the genome. Subgenomic mRNA transcription and genome replication are directed by the viral replicase, which is expressed in the form of two polyproteins and subsequently processed into smaller nonstructural proteins (nsps). During the recent construction of an EAV infectious cDNA clone (pEAV030 [L. C. van Dinten, J. A. den Boon, A. L. M. Wassenaar, W. J. M. Spaan, and E. J. Snijder, Proc. Natl. Acad. Sci. USA 94:991-996, 1997]), a mutant cDNA clone (pEAV030F) which carries a single replicase point mutation was obtained. This substitution (Ser-2429-->Pro) is located in the nsp10 subunit and renders the EAV030F virus deficient in subgenomic mRNA synthesis. To obtain more insight into the role of nsp10 in transcription and the nature of the transcriptional defect, we have now analyzed the EAV030F mutant in considerable detail. The Ser-2429-->Pro mutation does not affect the proteolytic processing of the replicase but apparently affects the function of nsp10 in transcription. Furthermore, our study showed that EAV030F still produces subgenomic positive and negative strands, albeit at a very low level. Both subgenomic positive-strand synthesis and negative-strand synthesis are equally affected by the Ser-2429-->Pro mutation, suggesting that nsp10 plays an important role in an early step of EAV mRNA transcription.
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Affiliation(s)
- G van Marle
- Department of Virology, Leiden University Medical Center, Leiden, The Netherlands
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