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Bougon J, Kadijk E, Gallot-Lavallee L, Curtis BA, Landers M, Archibald JM, Khaperskyy DA. Influenza A virus NS1 effector domain is required for PA-X-mediated host shutoff in infected cells. J Virol 2024; 98:e0190123. [PMID: 38629840 PMCID: PMC11092343 DOI: 10.1128/jvi.01901-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 03/28/2024] [Indexed: 05/15/2024] Open
Abstract
Many viruses inhibit general host gene expression to limit innate immune responses and gain preferential access to the cellular translational apparatus for their protein synthesis. This process is known as host shutoff. Influenza A viruses (IAVs) encode two host shutoff proteins: nonstructural protein 1 (NS1) and polymerase acidic X (PA-X). NS1 inhibits host nuclear pre-messenger RNA maturation and export, and PA-X is an endoribonuclease that preferentially cleaves host spliced nuclear and cytoplasmic messenger RNAs. Emerging evidence suggests that in circulating human IAVs NS1 and PA-X co-evolve to ensure optimal magnitude of general host shutoff without compromising viral replication that relies on host cell metabolism. However, the functional interplay between PA-X and NS1 remains unexplored. In this study, we sought to determine whether NS1 function has a direct effect on PA-X activity by analyzing host shutoff in A549 cells infected with wild-type or mutant IAVs with NS1 effector domain deletion. This was done using conventional quantitative reverse transcription polymerase chain reaction techniques and direct RNA sequencing using nanopore technology. Our previous research on the molecular mechanisms of PA-X function identified two prominent features of IAV-infected cells: nuclear accumulation of cytoplasmic poly(A) binding protein (PABPC1) and increase in nuclear poly(A) RNA abundance relative to the cytoplasm. Here we demonstrate that NS1 effector domain function augments PA-X host shutoff and is necessary for nuclear PABPC1 accumulation. By contrast, nuclear poly(A) RNA accumulation is not dependent on either NS1 or PA-X-mediated host shutoff and is accompanied by nuclear retention of viral transcripts. Our study demonstrates for the first time that NS1 and PA-X may functionally interact in mediating host shutoff.IMPORTANCERespiratory viruses including the influenza A virus continue to cause annual epidemics with high morbidity and mortality due to the limited effectiveness of vaccines and antiviral drugs. Among the strategies evolved by viruses to evade immune responses is host shutoff-a general blockade of host messenger RNA and protein synthesis. Disabling influenza A virus host shutoff is being explored in live attenuated vaccine development as an attractive strategy for increasing their effectiveness by boosting antiviral responses. Influenza A virus encodes two proteins that function in host shutoff: the nonstructural protein 1 (NS1) and the polymerase acidic X (PA-X). We and others have characterized some of the NS1 and PA-X mechanisms of action and the additive effects that these viral proteins may have in ensuring the blockade of host gene expression. In this work, we examined whether NS1 and PA-X functionally interact and discovered that NS1 is required for PA-X to function effectively. This work significantly advances our understanding of influenza A virus host shutoff and identifies new potential targets for therapeutic interventions against influenza and further informs the development of improved live attenuated vaccines.
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Affiliation(s)
- Juliette Bougon
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Eileigh Kadijk
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Lucie Gallot-Lavallee
- Department of Biochemistry & Molecular Biology, Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Bruce A. Curtis
- Department of Biochemistry & Molecular Biology, Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Matthew Landers
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - John M. Archibald
- Department of Biochemistry & Molecular Biology, Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Denys A. Khaperskyy
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
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2
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Beniston E, Skittrall JP. Locations and structures of influenza A virus packaging-associated signals and other functional elements via an in silico pipeline for predicting constrained features in RNA viruses. PLoS Comput Biol 2024; 20:e1012009. [PMID: 38648223 PMCID: PMC11034665 DOI: 10.1371/journal.pcbi.1012009] [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: 11/04/2023] [Accepted: 03/18/2024] [Indexed: 04/25/2024] Open
Abstract
Influenza A virus contains regions of its segmented genome associated with ability to package the segments into virions, but many such regions are poorly characterised. We provide detailed predictions of the key locations within these packaging-associated regions, and their structures, by applying a recently-improved pipeline for delineating constrained regions in RNA viruses and applying structural prediction algorithms. We find and characterise other known constrained regions within influenza A genomes, including the region associated with the PA-X frameshift, regions associated with alternative splicing, and constraint around the initiation motif for a truncated PB1 protein, PB1-N92, associated with avian viruses. We further predict the presence of constrained regions that have not previously been described. The extra characterisation our work provides allows investigation of these key regions for drug target potential, and points towards determinants of packaging compatibility between segments.
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Affiliation(s)
- Emma Beniston
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
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3
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Avanthay R, Garcia-Nicolas O, Zimmer G, Summerfield A. NS1 and PA-X of H1N1/09 influenza virus act in a concerted manner to manipulate the innate immune response of porcine respiratory epithelial cells. Front Cell Infect Microbiol 2023; 13:1222805. [PMID: 37565063 PMCID: PMC10410561 DOI: 10.3389/fcimb.2023.1222805] [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: 05/16/2023] [Accepted: 07/05/2023] [Indexed: 08/12/2023] Open
Abstract
Live-attenuated influenza A viruses (LAIV) may be superior to inactivated or subunit vaccines since they can be administered via mucosal routes to induce local immunity in the respiratory tract. In addition, LAIV are expected to trigger stronger T-cell responses that may protect against a broader range of antigen-drifted viruses. However, the development of LAIV is challenging since a proper balance between immunogenicity and safety has to be reached. In this study, we took advantage of reverse genetics to generate three LAIV based on the pandemic H1N1 2009 (pH1N1/09) virus strain: ΔPA-X, which is defective in the synthesis of the accessory PA-X protein, NS1(1-126) lacking 93 amino acids at the C-terminus of the NS1 protein, and a combination of both. Characterization of these recombinant viruses using a novel porcine bronchiolar epithelial cell line (T3) revealed that the ΔPA-X mutant replicated similar to wild type (WT) virus. However, in contrast to the parental virus the ΔPA-X mutant allowed transcription of genes involved in cell cycle progression and limits apoptosis. The NS1(1-126) mutant also replicated comparable to WT virus, but triggered the release of type I and III IFN and several chemokines and cytokines. Surprisingly, only the NS1(1-126)/ΔPA-X double mutant was significantly attenuated on T3 cells, and this was associated with enhanced transcription of genes of the innate immune system and complete absence of apoptosis induction. In conclusion, these findings indicate that NS1 and PA-X act in a concerted manner to manipulate the host cell response, which may help to develop swine LAIV vaccine with a more favorable balance of safety and immunogenicity.
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Affiliation(s)
- Robin Avanthay
- Institute of Virology and Immunology, Mittelhäusern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Obdulio Garcia-Nicolas
- Institute of Virology and Immunology, Mittelhäusern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Gert Zimmer
- Institute of Virology and Immunology, Mittelhäusern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Artur Summerfield
- Institute of Virology and Immunology, Mittelhäusern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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4
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Gaucherand L, Iyer A, Gilabert I, Rycroft CH, Gaglia MM. Cut site preference allows influenza A virus PA-X to discriminate between host and viral mRNAs. Nat Microbiol 2023; 8:1304-1317. [PMID: 37349586 PMCID: PMC10690756 DOI: 10.1038/s41564-023-01409-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 05/10/2023] [Indexed: 06/24/2023]
Abstract
Many viruses block host gene expression to take over the infected cell. This process, termed host shutoff, is thought to promote viral replication by preventing antiviral responses and redirecting cellular resources to viral processes. Several viruses from divergent families accomplish host shutoff through RNA degradation by endoribonucleases. However, viruses also need to ensure expression of their own genes. The influenza A virus endoribonuclease PA-X solves this problem by sparing viral mRNAs and some host RNAs necessary for viral replication. To understand how PA-X distinguishes between RNAs, we characterized PA-X cut sites transcriptome-wide using 5' rapid amplification of complementary DNA ends coupled to high-throughput sequencing. This analysis, along with RNA structure predictions and validation experiments using reporters, shows that PA-Xs from multiple influenza strains preferentially cleave RNAs at GCUG tetramers in hairpin loops. Importantly, GCUG tetramers are enriched in the human but not the influenza transcriptome. Moreover, optimal PA-X cut sites inserted in the influenza A virus genome are quickly selected against during viral replication in cells. This finding suggests that PA-X evolved these cleavage characteristics to preferentially target host over viral mRNAs in a manner reminiscent of cellular self versus non-self discrimination.
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Affiliation(s)
- Lea Gaucherand
- Program in Molecular Microbiology, Tufts University Graduate School of Biomedical Sciences, Boston, MA, USA
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
- Architecture et Réactivité de l'ARN, Institut de Biologie Moléculaire et Cellulaire du CNRS, Université de Strasbourg, Strasbourg, France
| | - Amrita Iyer
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Isabel Gilabert
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
- Faculty of Experimental Sciences, Universidad Francisco de Vitoria, Madrid, Spain
| | - Chris H Rycroft
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Mathematics, University of Wisconsin-Madison, Madison, WI, USA
| | - Marta M Gaglia
- Program in Molecular Microbiology, Tufts University Graduate School of Biomedical Sciences, Boston, MA, USA.
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.
- Institute for Molecular Virology and Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA.
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5
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Hu Y, Chen X, Ling Y, Zhou K, Han M, Wang X, Yue M, Li Y. Influenza A virus inhibits TET2 expression by endoribonuclease PA-X to attenuate type I interferon signaling and promote viral replication. PLoS Pathog 2023; 19:e1011550. [PMID: 37498975 PMCID: PMC10409264 DOI: 10.1371/journal.ppat.1011550] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Revised: 08/08/2023] [Accepted: 07/10/2023] [Indexed: 07/29/2023] Open
Abstract
Influenza A virus (IAV) expresses several accessory proteins to limit host anti-viral restriction factors to facilitate viral replication. The Ten-Eleven Translocation 2 (TET2) is a methylcytosine dioxygenase that promotes DNA demethylation by catalyzing the oxidation of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC), which plays a vital role in hematopoiesis and immunity. Here we report that TET2 is a host restriction factor that limits IAV replication. But IAV endoribonuclease PA-X is able to remove the replication restriction by binding to TET2 mRNA and driving TET2 mRNA degradation to reduce TET2 expression during infection. Genetic inactivation of TET2 markedly enhances IAV replication in vitro and in vivo. Mechanistically, we found that TET2 regulates demethylation and transcription of STAT1 and some interferon-stimulated genes (ISGs), including ISG15, ISG20, and IFIT5, so the loss of TET2 greatly impairs type I Interferon signaling. Furthermore, we confirmed that TET2-mediated demethylation of the STAT1 gene is critical for interferon anti-viral activity. Our study demonstrates that the host TET2 is essential to the innate immune response against IAV infection.
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Affiliation(s)
- Yixiang Hu
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Hainan Institute of Zhejiang University, Sanya, Hainan, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Xinru Chen
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Yuehuan Ling
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Kun Zhou
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Meiqing Han
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Hainan Institute of Zhejiang University, Sanya, Hainan, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Xingbo Wang
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
| | - Min Yue
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Hainan Institute of Zhejiang University, Sanya, Hainan, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, National Medical Center for Infectious Diseases, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yan Li
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Hainan Institute of Zhejiang University, Sanya, Hainan, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
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6
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Antonov IV, O’Loughlin S, Gorohovski AN, O’Connor PB, Baranov PV, Atkins JF. Streptomyces rare codon UUA: from features associated with 2 adpA related locations to candidate phage regulatory translational bypassing. RNA Biol 2023; 20:926-942. [PMID: 37968863 PMCID: PMC10732093 DOI: 10.1080/15476286.2023.2270812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 10/02/2023] [Indexed: 11/17/2023] Open
Abstract
In Streptomyces species, the cell cycle involves a switch from an early and vegetative state to a later phase where secondary products including antibiotics are synthesized, aerial hyphae form and sporulation occurs. AdpA, which has two domains, activates the expression of numerous genes involved in the switch from the vegetative growth phase. The adpA mRNA of many Streptomyces species has a UUA codon in a linker region between 5' sequence encoding one domain and 3' sequence encoding its other and C-terminal domain. UUA codons are exceptionally rare in Streptomyces, and its functional cognate tRNA is not present in a fully modified and acylated form, in the early and vegetative phase of the cell cycle though it is aminoacylated later. Here, we report candidate recoding signals that may influence decoding of the linker region UUA. Additionally, a short ORF 5' of the main ORF has been identified with a GUG at, or near, its 5' end and an in-frame UUA near its 3' end. The latter is commonly 5 nucleotides 5' of the main ORF start. Ribosome profiling data show translation of that 5' region. Ten years ago, UUA-mediated translational bypassing was proposed as a sensor by a Streptomyces phage of its host's cell cycle stage and an effector of its lytic/lysogeny switch. We provide the first experimental evidence supportive of this proposal.
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Affiliation(s)
- Ivan V. Antonov
- Russian Academy of Science, Institute of Bioengineering, Research Center of Biotechnology, Moscow, Russia
- Laboratory of Bioinformatics, Faculty of Computer Science, National Research University Higher School of Economics, Moscow, Russia
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Sinéad O’Loughlin
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Alessandro N. Gorohovski
- Russian Academy of Science, Institute of Bioengineering, Research Center of Biotechnology, Moscow, Russia
- Structural Biology and BioComputing Program, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | | | - Pavel V. Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - John F. Atkins
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
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Strategies of Influenza A Virus to Ensure the Translation of Viral mRNAs. Pathogens 2022; 11:pathogens11121521. [PMID: 36558855 PMCID: PMC9783940 DOI: 10.3390/pathogens11121521] [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: 11/23/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 12/14/2022] Open
Abstract
Viruses are obligatorily intracellular pathogens. To generate progeny virus particles, influenza A viruses (IAVs) have to divert the cellular machinery to ensure sufficient translation of viral mRNAs. To this end, several strategies have been exploited by IAVs, such as host gene shutoff, suppression of host innate immune responses, and selective translation of viral mRNAs. Various IAV proteins are responsible for host gene shutoff, e.g., NS1, PA-X, and RdRp, through inhibition of cellular gene transcription, suppression of cellular RNA processing, degradation of cellular RNAs, and blockage of cellular mRNA export from the nucleus. Host shutoff should suppress the innate immune responses and also increase the translation of viral mRNAs indirectly due to the reduced competition from cellular mRNAs for cellular translational machinery. However, many other mechanisms are also responsible for the suppression of innate immune responses by IAV, such as prevention of the detection of the viral RNAs by the RLRs, inhibition of the activities of proteins involved in signaling events of interferon production, and inhibition of the activities of interferon-stimulated genes, mainly through viral NS1, PB1-F2, and PA-X proteins. IAV mRNAs may be selectively translated in favor of cellular mRNAs through interacting with viral and/or cellular proteins, such as NS1, PABPI, and/or IFIT2, in the 5'-UTR of viral mRNAs. This review briefly summarizes the strategies utilized by IAVs to ensure sufficient translation of viral mRNAs focusing on recent developments.
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Sidharthan VK, Rajeswari V, Vanamala G, Baranwal VK. Revisiting the amalgaviral landscapes in plant transcriptomes expands the host range of plant amalgaviruses. Virology 2022; 577:65-73. [PMID: 36308887 DOI: 10.1016/j.virol.2022.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 10/09/2022] [Accepted: 10/16/2022] [Indexed: 11/19/2022]
Abstract
Plant amalgaviruses are monopartite, double-stranded RNA viruses, capable of vertical transmission through seeds. An attempt to revisit plant transcriptome-assembled contigs for amalgaviral sequences identified 40 putative novel amalgaviruses in 35 plant species, nearly doubling the number of plant amalgaviruses. Of the 35 plant species, 33 are reported to host amalgaviruses for the first time, including a pteridophytic and two gymnospermic species. Coding-complete genomes of all identified viruses were recovered and the putative +1 programmed ribosomal frameshift (PRF) sites were determined. Genomes of 35 identified amalgaviruses contained the conserved +1 PRF motif 'UUU_CGN', while variant versions were predicted in five genomes. Phylogenetic analysis grouped pteridophyte- and gymnosperm-infecting amalgaviruses together in divergent sub-clades while few of the related angiosperm-infecting amalgaviruses infect members of the same plant family, reiterating the co-evolution of plant amalgaviruses and their hosts. The current study paves way for further studies on understanding biological properties of identified viruses.
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Affiliation(s)
- V Kavi Sidharthan
- Division of Genetics and Tree Improvement, Institute of Forest Biodiversity (ICFRE), Hyderabad, India.
| | - V Rajeswari
- Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore, India
| | - Gayatri Vanamala
- Division of Genetics and Tree Improvement, Institute of Forest Biodiversity (ICFRE), Hyderabad, India
| | - V K Baranwal
- Division of Plant Pathology, ICAR-Indian Agricultural Research Institute, New Delhi, India.
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9
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Geneticin shows selective antiviral activity against SARS-CoV-2 by interfering with programmed −1 ribosomal frameshifting. Antiviral Res 2022; 208:105452. [PMID: 36341734 PMCID: PMC9617636 DOI: 10.1016/j.antiviral.2022.105452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 10/18/2022] [Accepted: 10/21/2022] [Indexed: 11/21/2022]
Abstract
SARS-CoV-2 is currently causing an unprecedented pandemic. While vaccines are massively deployed, we still lack effective large-scale antiviral therapies. In the quest for antivirals targeting conserved structures, we focused on molecules able to bind viral RNA secondary structures. Aminoglycosides are a class of antibiotics known to interact with the ribosomal RNA of both prokaryotes and eukaryotes and have previously been shown to exert antiviral activities by interacting with viral RNA. Here we show that the aminoglycoside geneticin is endowed with antiviral activity against all tested variants of SARS-CoV-2, in different cell lines and in a respiratory tissue model at non-toxic concentrations. The mechanism of action is an early inhibition of RNA replication and protein expression related to a decrease in the efficiency of the −1 programmed ribosomal frameshift (PRF) signal of SARS-CoV-2. Using in silico modeling, we have identified a potential binding site of geneticin in the pseudoknot of frameshift RNA motif. Moreover, we have selected, through virtual screening, additional RNA binding compounds, interacting with the same site with increased potency.
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10
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Li Y, Liu S, Guo K, Ding W, Wang R. Virome of Pseudostellaria heterophylla: Identification and characterization of three novel carlaviruses and one novel amalgavirus associated with viral diseases of Pseudostellaria heterophylla. Front Microbiol 2022; 13:955089. [PMID: 36246219 PMCID: PMC9559581 DOI: 10.3389/fmicb.2022.955089] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 09/12/2022] [Indexed: 11/30/2022] Open
Abstract
Pseudostellaria heterophylla is a traditional Chinese herbal medicine, which has been cultivated for hundreds of years. Viral diseases of P. heterophylla occur widely and limit the yield and quality of this medicinal plant. In this study, five leaf samples of P. heterophylla with typical viral symptoms were collected from four main producing regions that are distributed in Fujian, Guizhou, and Anhui Provinces in China and analyzed by next-generation sequencing. Comprehensive bioinformatics analyses revealed that nine viruses in five genera Carlavirus, Potyvirus, Fabavirus, Cucumovirus, and Amalgavirus infected P. heterophylla. Among these viruses, three novel and two known carlaviruses, tentatively designated Pseudostellaria heterophylla carlavirus 1, 2, and 3 (PhCV1, PhCV2, and PhCV3), Jasmine virus C isolate Ph (Ph-JVC) and Stevia carlavirus 1 isolate Ph (Ph-StCV1), respectively, were first identified in P. heterophylla. PhCV1-3 share a similar genomic organization and clear sequence homology with members in the genus Carlavirus and could potentially be classified as new species of this genus. One novel amalgavirus, tentatively designated P. heterophylla amalgavirus 1 (PhAV1), was first identified in P. heterophylla. It had a typical genomic organization of the genus Amalgavirus. In PhAV1, the + 1 programmed ribosomal frameshifting, which is prevalent in most amalgaviruses, was identified and used in the expression of RNA-dependent RNA polymerase (RdRp). Combined with a phylogenetic analysis, PhAV1 could potentially be classified as new species of the genus Amalgavirus. In addition, multiple Broad bean wilt virus 2 (BBWV2) variants, Turnip mosaic virus (TuMV), and Cucumber mosaic virus (CMV), which have been reported in P. heterophylla, were also detected in this study. The distribution of PhCV1-3, Ph-JVC, Ph-StCV1, TuMV, BBWV2, and CMV in four production regions in Fujian, Guizhou, and Anhui Provinces was determined. This study increased our understanding of P. heterophylla virome and provided valuable information for the development of a molecular diagnostic technique and control of viral diseases in P. heterophylla.
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11
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Varricchio C, Mathez G, Pillonel T, Bertelli C, Kaiser L, Tapparel C, Brancale A, Cagno V. Geneticin shows selective antiviral activity against SARS-CoV-2 by interfering with programmed -1 ribosomal frameshifting. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2022:2022.03.08.483429. [PMID: 35291297 PMCID: PMC8923105 DOI: 10.1101/2022.03.08.483429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
SARS-CoV-2 is currently causing an unprecedented pandemic. While vaccines are massively deployed, we still lack effective large-scale antiviral therapies. In the quest for antivirals targeting conserved structures, we focused on molecules able to bind viral RNA secondary structures. Aminoglycosides are a class of antibiotics known to interact with the ribosomal RNA of both prokaryotes and eukaryotes and have previously been shown to exert antiviral activities by interacting with viral RNA. Here we show that the aminoglycoside geneticin is endowed with antiviral activity against all tested variants of SARS-CoV-2, in different cell lines and in a respiratory tissue model at non-toxic concentrations. The mechanism of action is an early inhibition of RNA replication and protein expression related to a decrease in the efficiency of the -1 programmed ribosomal frameshift (PRF) signal of SARS-CoV-2. Using in silico modelling, we have identified a potential binding site of geneticin in the pseudoknot of frameshift RNA motif. Moreover, we have selected, through virtual screening, additional RNA binding compounds, interacting with the same site with increased potency.
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Affiliation(s)
- Carmine Varricchio
- Cardiff School of Pharmacy and Pharmaceutical Sciences, Cardiff, King Edward VII Avenue, Cardiff, UK
| | - Gregory Mathez
- Institute of Microbiology, Lausanne University Hospital, University of Lausanne, Switzerland
| | - Trestan Pillonel
- Institute of Microbiology, Lausanne University Hospital, University of Lausanne, Switzerland
| | - Claire Bertelli
- Institute of Microbiology, Lausanne University Hospital, University of Lausanne, Switzerland
| | - Laurent Kaiser
- Laboratory of Virology, Division of Infectious Diseases and Division of Laboratory Medicine, University Hospitals of Geneva, University of Geneva, Geneva, Switzerland
- Center for Emerging Viruses, Geneva University Hospitals, 1205 Geneva, Switzerland
| | - Caroline Tapparel
- Department of Microbiology and Molecular Medicine, University of Geneva, 1206 Geneva, Switzerland
| | - Andrea Brancale
- Cardiff School of Pharmacy and Pharmaceutical Sciences, Cardiff, King Edward VII Avenue, Cardiff, UK
| | - Valeria Cagno
- Institute of Microbiology, Lausanne University Hospital, University of Lausanne, Switzerland
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12
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The full-length genome sequence of a novel amalgavirus in Lilium spp. in China. Arch Virol 2022; 167:2103-2107. [PMID: 35834002 DOI: 10.1007/s00705-022-05523-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 05/22/2022] [Indexed: 11/02/2022]
Abstract
We report for the first time the complete genome sequence of a novel amalgavirus, tentatively designated as 'lily amalgavirus 1' (LAV-1), isolated from Lilium spp. in China. LAV-1 is a 3448-nt double-stranded RNA virus that encodes two putative proteins. Open reading frame 1 (ORF1) encodes a 394-aa protein with unknown function. ORF2 encodes a putative RNA-dependent RNA polymerase (RdRp) of 895 aa. The two ORFs putatively encode a '1 + 2' fusion protein generated by a '+1' programmed ribosomal frameshift (PRF). BLASTp analysis revealed that the complete genome sequence of LAV-1 shares 48.23-59.80% sequence identity (query sequence coverage > 77%) with those of members of the genus Amalgavirus, with the highest nucleotide sequence identity of 59.80% with that of Allium cepa amalgavirus 1 (query sequence coverage, 87%). The genome structure, phylogenetic relationships, and sequence similarities to other plant amalgaviruses suggest that LAV-1 is a new member of the genus Amalgavirus.
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Wang X, Lai J, Hu H, Yang J, Zang K, Zhao F, Zeng G, Liao Q, Gu Z, Du Z. Infection of Nigrospora nonsegmented RNA Virus 1 Has Important Biological Impacts on a Fungal Host. Viruses 2022; 14:v14040795. [PMID: 35458525 PMCID: PMC9029208 DOI: 10.3390/v14040795] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/04/2022] [Accepted: 04/06/2022] [Indexed: 01/27/2023] Open
Abstract
Nigrospora nonsegmented RNA virus 1 (NoNRV1) has been reported previously in the fungus Nigrospora oryzae, but its biological effects on its host are unknown. In this work, we isolated a strain 9-1 of N. oryzae from a chrysanthemum leaf and identified NoNRV1 infection in the isolated strain. The genome sequence of NoNRV1 identified here is highly homologous to that of the isolate HN-21 of NoNRV1 previously reported; thus, we tentatively designated the newly identified NoNRV1 as NoNRV1-ZJ. Drug treatment with Ribavirin successfully removed NoNRV1-ZJ from the strain 9-1, which provided us with an ideal control to determine the biological impacts of NoNRV1 infection on host fungi. By comparing the virus-carrying (9-1) and virus-cured (9-1C) strains, our results indicated that infection with NoNRV1 promoted the pigmentation of the host cells, while it had no discernable effects on host growth on potato dextrose agar plates when subjected to osmotic or oxidative stress. Interestingly, we observed inhibitory impacts of virus infection on the thermotolerance of N. oryzae and the pathogenicity of the host fungus in cotton leaves. Collectively, our work provides clear evidence of the biological relevance of NoNRV1 infection in N. oryzae, including pigmentation, hypovirulence, and thermotolerance.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Zhouhang Gu
- Correspondence: (Z.G.); (Z.D.); Tel.: +86-571-8684-3195 (Z.D.)
| | - Zhiyou Du
- Correspondence: (Z.G.); (Z.D.); Tel.: +86-571-8684-3195 (Z.D.)
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14
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Abstract
Influenza A virus has long been known to encode 10 major polypeptides, produced, almost without exception, by every natural isolate of the virus. These polypeptides are expressed in readily detectable amounts during infection and are either fully essential or their loss severely attenuates virus replication. More recent work has shown that this core proteome is elaborated by expression of a suite of accessory gene products that tend to be expressed at lower levels through noncanonical transcriptional and/or translational events. Expression and activity of these accessory proteins varies between virus strains and is nonessential (sometimes inconsequential) for virus replication in cell culture, but in many cases has been shown to affect virulence and/or transmission in vivo. This review describes, when known, the expression mechanisms and functions of this influenza A virus accessory proteome and discusses its significance and evolution.
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Affiliation(s)
- Rute M Pinto
- The Roslin Institute, University of Edinburgh, Midlothian EH25 9RG, United Kingdom
| | - Samantha Lycett
- The Roslin Institute, University of Edinburgh, Midlothian EH25 9RG, United Kingdom
| | - Eleanor Gaunt
- The Roslin Institute, University of Edinburgh, Midlothian EH25 9RG, United Kingdom
| | - Paul Digard
- The Roslin Institute, University of Edinburgh, Midlothian EH25 9RG, United Kingdom
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15
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Priyadarshi H, Das R. Complexities in viral replication strategies as a potential explanation for prevalence of asymptomatic carriers in Covid-19 infections: analytical observation on SARS-Cov2 genome characteristics. Theory Biosci 2021; 140:241-247. [PMID: 34114198 PMCID: PMC8191711 DOI: 10.1007/s12064-021-00349-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 05/18/2021] [Indexed: 11/29/2022]
Abstract
Analytical observations (in silico) indicate molecular features of SARS-Cov2 genome that potentially explains the high prevalence of asymptomatic cases in Covid-19 pandemic. We observed that the virus maintains a low preference for 'GGG' codon for glycine (3%) in its genome. We also observed multiple putative introns of 26-44 nucleotide (nt) length in the genomic region between the coding regions of Nsp10 and RPol in the viral ORF1ab, like several other beta-coronaviruses of similar infectivity levels. It appears that the virus employs a dual strategy to ensure unhindered replication within the host. One of the strategies employ a (- )1 frameshift translation event through programmed ribosomal slippage at the ribosomal slippage site in the ORF1ab. The alternate strategy relies on intron excision to generate a read through frame. The presence of 'GGG' in this conserved ribosomal slippage site ensures adequate tRNA in cytoplasm to match the codon, implying no additional frameshift translation due to ribosomal stalling. With fewer replication events, viral load remains low and resulting in asymptomatic cases. We suggest that this strategy is the primary reason for the prevalence of asymptomatic cases in the disease, enabling the virus to spread rapidly.
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Affiliation(s)
- Himanshu Priyadarshi
- Department of Genetics and Reproduction, College of Fisheries, Central Agricultural University (Imphal), Lembucherra, Agartala, Tripura, 799210, India.
| | - Rekha Das
- ICAR Research Complex for NEH Region, Tripura Regional Centre, Lembucherra, Agartala, Tripura, 799210, India
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16
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Mazel-Sanchez B, Iwaszkiewicz J, Bonifacio JPP, Silva F, Niu C, Strohmeier S, Eletto D, Krammer F, Tan G, Zoete V, Hale BG, Schmolke M. Influenza A viruses balance ER stress with host protein synthesis shutoff. Proc Natl Acad Sci U S A 2021; 118:e2024681118. [PMID: 34479996 PMCID: PMC8433552 DOI: 10.1073/pnas.2024681118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 07/15/2021] [Indexed: 02/06/2023] Open
Abstract
Excessive production of viral glycoproteins during infections poses a tremendous stress potential on the endoplasmic reticulum (ER) protein folding machinery of the host cell. The host cell balances this by providing more ER resident chaperones and reducing translation. For viruses, this unfolded protein response (UPR) offers the potential to fold more glycoproteins. We postulated that viruses could have developed means to limit the inevitable ER stress to a beneficial level for viral replication. Using a relevant human pathogen, influenza A virus (IAV), we first established the determinant for ER stress and UPR induction during infection. In contrast to a panel of previous reports, we identified neuraminidase to be the determinant for ER stress induction, and not hemagglutinin. IAV relieves ER stress by expression of its nonstructural protein 1 (NS1). NS1 interferes with the host messenger RNA processing factor CPSF30 and suppresses ER stress response factors, such as XBP1. In vivo viral replication is increased when NS1 antagonizes ER stress induction. Our results reveal how IAV optimizes glycoprotein expression by balancing folding capacity.
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Affiliation(s)
- Beryl Mazel-Sanchez
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva, Switzerland
| | - Justyna Iwaszkiewicz
- Molecular Modelling Group, Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Joao P P Bonifacio
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva, Switzerland
| | - Filo Silva
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva, Switzerland
| | - Chengyue Niu
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva, Switzerland
| | - Shirin Strohmeier
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Davide Eletto
- Institute of Medical Virology, University of Zürich, 8057 Zürich, Switzerland
| | - Florian Krammer
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Gene Tan
- Infectious Diseases, J. Craig Venter Institute, La Jolla, CA 92037
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Vincent Zoete
- Molecular Modelling Group, Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Benjamin G Hale
- Institute of Medical Virology, University of Zürich, 8057 Zürich, Switzerland
| | - Mirco Schmolke
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva, Switzerland;
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17
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Nogales A, Villamayor L, Utrilla-Trigo S, Ortego J, Martinez-Sobrido L, DeDiego ML. Natural Selection of H5N1 Avian Influenza A Viruses with Increased PA-X and NS1 Shutoff Activity. Viruses 2021; 13:v13091760. [PMID: 34578340 PMCID: PMC8472985 DOI: 10.3390/v13091760] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/28/2021] [Accepted: 08/31/2021] [Indexed: 12/01/2022] Open
Abstract
Influenza A viruses (IAV) can infect a broad range of mammalian and avian species. However, the host innate immune system provides defenses that restrict IAV replication and infection. Likewise, IAV have evolved to develop efficient mechanisms to counteract host antiviral responses to efficiently replicate in their hosts. The IAV PA-X and NS1 non-structural proteins are key virulence factors that modulate innate immune responses and virus pathogenicity during infection. To study the determinants of IAV pathogenicity and their functional co-evolution, we evaluated amino acid differences in the PA-X and NS1 proteins of early (1996–1997) and more recent (since 2016) H5N1 IAV. H5N1 IAV have zoonotic and pandemic potential and represent an important challenge both in poultry farming and human health. The results indicate that amino acid changes occurred over time, affecting the ability of these two non-structural H5N1 IAV proteins to inhibit gene expression and affecting virus pathogenicity. These results highlight the importance to monitor the evolution of these two virulence factors of IAV, which could result in enhanced viral replication and virulence.
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Affiliation(s)
- Aitor Nogales
- Center for Animal Health Research, CISA-INIA-CSIC, Valdeolmos, 28130 Madrid, Spain; (S.U.-T.); (J.O.)
- Correspondence: (A.N.); (M.L.D.)
| | - Laura Villamayor
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain;
| | - Sergio Utrilla-Trigo
- Center for Animal Health Research, CISA-INIA-CSIC, Valdeolmos, 28130 Madrid, Spain; (S.U.-T.); (J.O.)
| | - Javier Ortego
- Center for Animal Health Research, CISA-INIA-CSIC, Valdeolmos, 28130 Madrid, Spain; (S.U.-T.); (J.O.)
| | - Luis Martinez-Sobrido
- Department of Disease Intervention and Prevention, Texas Biomedical Research Institute, San Antonio, TX 78227, USA;
| | - Marta L. DeDiego
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain;
- Correspondence: (A.N.); (M.L.D.)
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18
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Burnham AJ, Miller JR, Singh I, Billings EA, Rush MA, Air GM, Bour S. Novel isoforms of influenza virus PA-X and PB1-F2 indicated by automatic annotation. Virus Res 2021; 304:198545. [PMID: 34391827 DOI: 10.1016/j.virusres.2021.198545] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 04/02/2021] [Accepted: 08/04/2021] [Indexed: 12/18/2022]
Abstract
The influenza A virus genome contains 8 gene segments encoding 10 commonly recognized proteins. Additional protein products have been identified, including PB1-F2 and PA-X. We report the in-silico identification of novel isoforms of PB1-F2 and PA-X in influenza virus genomes sequenced from avian samples. The isoform observed in PA-X includes a mutated stop codon that should extend the protein product by 8 amino acids. The isoform observed in PB1-F2 includes two nonsense mutations that should truncate the N-terminal region of the protein product and remove the entire mitochondrial targeting domain. Both isoforms were uncovered during automatic annotation of CEIRS sequence data. Nominally termed PA-X8 and PB1-F2-Cterm, both predicted isoforms were subsequently found in other annotated influenza genomes previously deposited in GenBank. Both isoforms were noticed due to discrepant annotations output by two annotation engines, indicating a benefit of incorporating multiple algorithms during gene annotation.
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Affiliation(s)
- Andrew J Burnham
- CEIRS Data Processing and Coordinating Center, United States; Gryphon Scientific, United States
| | - Jason Rafe Miller
- CEIRS Data Processing and Coordinating Center, United States; Shepherd University, United States
| | - Indresh Singh
- CEIRS Data Processing and Coordinating Center, United States; J. Craig Venter Institute, United States
| | - Emily A Billings
- CEIRS Data Processing and Coordinating Center, United States; Gryphon Scientific, United States
| | - Margaret A Rush
- CEIRS Data Processing and Coordinating Center, United States; Gryphon Scientific, United States
| | - Gillian M Air
- CEIRS Data Processing and Coordinating Center, United States; University of Oklahoma Health Sciences Center, United States
| | - Stephan Bour
- CEIRS Data Processing and Coordinating Center, United States; Digital Infuzion, United States.
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19
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Hatakeyama D, Shoji M, Ogata S, Masuda T, Nakano M, Komatsu T, Saitoh A, Makiyama K, Tsuneishi H, Miyatake A, Takahira M, Nishikawa E, Ohkubo A, Noda T, Kawaoka Y, Ohtsuki S, Kuzuhara T. Acetylation of the influenza A virus polymerase subunit PA in the N-terminal domain positively regulates its endonuclease activity. FEBS J 2021; 289:231-245. [PMID: 34270849 DOI: 10.1111/febs.16123] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 06/07/2021] [Accepted: 07/15/2021] [Indexed: 01/06/2023]
Abstract
The post-translational acetylation of lysine residues is found in many nonhistone proteins and is involved in a wide range of biological processes. Recently, we showed that the nucleoprotein of the influenza A virus is acetylated by histone acetyltransferases (HATs), a phenomenon that affects viral transcription. Here, we report that the PA subunit of influenza A virus RNA-dependent RNA polymerase is acetylated by the HATs, P300/CREB-binding protein-associated factor (PCAF), and general control nonderepressible 5 (GCN5), resulting in accelerated endonuclease activity. Specifically, the full-length PA subunit expressed in cultured 293T cells was found to be strongly acetylated. Moreover, the partial recombinant protein of the PA N-terminal region containing the endonuclease domain was also acetylated by PCAF and GCN5 in vitro, which facilitated its endonuclease activity. Mass spectrometry analyses identified K19 as a candidate acetylation target in the PA N-terminal region. Notably, the substitution of the lysine residue at position 19 with glutamine, a mimic of the acetyl-lysine residue, enhanced its endonuclease activity in vitro; this point mutation also accelerated influenza A virus RNA-dependent RNA polymerase activity in the cell. Our findings suggest that PA acetylation is important for the regulation of the endonuclease and RNA polymerase activities of the influenza A virus.
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Affiliation(s)
- Dai Hatakeyama
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Masaki Shoji
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Seiryo Ogata
- Department of Pharmaceutical Microbiology, Graduate School of Pharmaceutical Sciences, Kumamoto University, Japan
| | - Takeshi Masuda
- Department of Pharmaceutical Microbiology, Graduate School of Pharmaceutical Sciences, Kumamoto University, Japan
| | - Masahiro Nakano
- Institute for Frontier Life and Medical Sciences, Kyoto University, Japan
| | - Tsugunori Komatsu
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Ayaka Saitoh
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Kyoko Makiyama
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Hazuki Tsuneishi
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Asuka Miyatake
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Mizuki Takahira
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Erina Nishikawa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Ayana Ohkubo
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
| | - Takeshi Noda
- Institute for Frontier Life and Medical Sciences, Kyoto University, Japan
| | - Yoshihiro Kawaoka
- Institute of Medical Science, University of Tokyo, Japan.,School of Veterinary Medicine, University of Wisconsin-Madison, WI, USA
| | - Sumio Ohtsuki
- Department of Pharmaceutical Microbiology, Graduate School of Pharmaceutical Sciences, Kumamoto University, Japan
| | - Takashi Kuzuhara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan
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20
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Atkins JF, O’Connor KM, Bhatt PR, Loughran G. From Recoding to Peptides for MHC Class I Immune Display: Enriching Viral Expression, Virus Vulnerability and Virus Evasion. Viruses 2021; 13:1251. [PMID: 34199077 PMCID: PMC8310308 DOI: 10.3390/v13071251] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/11/2021] [Accepted: 06/19/2021] [Indexed: 01/02/2023] Open
Abstract
Many viruses, especially RNA viruses, utilize programmed ribosomal frameshifting and/or stop codon readthrough in their expression, and in the decoding of a few a UGA is dynamically redefined to specify selenocysteine. This recoding can effectively increase viral coding capacity and generate a set ratio of products with the same N-terminal domain(s) but different C-terminal domains. Recoding can also be regulatory or generate a product with the non-universal 21st directly encoded amino acid. Selection for translation speed in the expression of many viruses at the expense of fidelity creates host immune defensive opportunities. In contrast to host opportunism, certain viruses, including some persistent viruses, utilize recoding or adventitious frameshifting as part of their strategy to evade an immune response or specific drugs. Several instances of recoding in small intensively studied viruses escaped detection for many years and their identification resolved dilemmas. The fundamental importance of ribosome ratcheting is consistent with the initial strong view of invariant triplet decoding which however did not foresee the possibility of transitory anticodon:codon dissociation. Deep level dynamics and structural understanding of recoding is underway, and a high level structure relevant to the frameshifting required for expression of the SARS CoV-2 genome has just been determined.
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Affiliation(s)
- John F. Atkins
- Schools of Biochemistry and Microbiology, University College Cork, T12 XF62 Cork, Ireland; (K.M.O.); (P.R.B.); (G.L.)
| | - Kate M. O’Connor
- Schools of Biochemistry and Microbiology, University College Cork, T12 XF62 Cork, Ireland; (K.M.O.); (P.R.B.); (G.L.)
| | - Pramod R. Bhatt
- Schools of Biochemistry and Microbiology, University College Cork, T12 XF62 Cork, Ireland; (K.M.O.); (P.R.B.); (G.L.)
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, 8093 Zurich, Switzerland
| | - Gary Loughran
- Schools of Biochemistry and Microbiology, University College Cork, T12 XF62 Cork, Ireland; (K.M.O.); (P.R.B.); (G.L.)
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21
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Marucci G, Zullino I, Bertuccini L, Camerini S, Cecchetti S, Pietrantoni A, Casella M, Vatta P, Greenwood AD, Fiorillo A, Lalle M. Re-Discovery of Giardiavirus: Genomic and Functional Analysis of Viruses from Giardia duodenalis Isolates. Biomedicines 2021; 9:654. [PMID: 34201207 PMCID: PMC8230311 DOI: 10.3390/biomedicines9060654] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/01/2021] [Accepted: 06/02/2021] [Indexed: 12/29/2022] Open
Abstract
Giardiasis, caused by the protozoan parasite Giardia duodenalis, is an intestinal diarrheal disease affecting almost one billion people worldwide. A small endosymbiotic dsRNA viruses, G. lamblia virus (GLV), genus Giardiavirus, family Totiviridae, might inhabit human and animal isolates of G. duodenalis. Three GLV genomes have been sequenced so far, and only one was intensively studied; moreover, a positive correlation between GLV and parasite virulence is yet to be proved. To understand the biological significance of GLV infection in Giardia, the characterization of several GLV strains from naturally infected G. duodenalis isolates is necessary. Here we report high-throughput sequencing of four GLVs strains, from Giardia isolates of human and animal origin. We also report on a new, unclassified viral sequence (designed GdRV-2), unrelated to Giardiavirus, encoding and expressing for a single large protein with an RdRp domain homologous to Totiviridae and Botybirnaviridae. The result of our sequencing and proteomic analyses challenge the current knowledge on GLV and strongly suggest that viral capsid protein translation unusually starts with a proline and that translation of the RNA-dependent RNA polymerase (RdRp) occurs via a +1/-2 ribosomal frameshift mechanism. Nucleotide polymorphism, confirmed by mass-spectrometry analysis, was also observed among and between GLV strains. Phylogenetic analysis indicated the occurrence of at least two GLV subtypes which display different phenotypes and transmissibility in experimental infections of a GLV naïve Giardia isolate.
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Affiliation(s)
- Gianluca Marucci
- Unit of Foodborne and Neglected Parasitic Disease, Department of Infectious Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (G.M.); (I.Z.); (P.V.)
| | - Ilaria Zullino
- Unit of Foodborne and Neglected Parasitic Disease, Department of Infectious Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (G.M.); (I.Z.); (P.V.)
| | - Lucia Bertuccini
- Core Facilities, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (L.B.); (S.C.); (S.C.); (A.P.); (M.C.)
| | - Serena Camerini
- Core Facilities, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (L.B.); (S.C.); (S.C.); (A.P.); (M.C.)
| | - Serena Cecchetti
- Core Facilities, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (L.B.); (S.C.); (S.C.); (A.P.); (M.C.)
| | - Agostina Pietrantoni
- Core Facilities, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (L.B.); (S.C.); (S.C.); (A.P.); (M.C.)
| | - Marialuisa Casella
- Core Facilities, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (L.B.); (S.C.); (S.C.); (A.P.); (M.C.)
| | - Paolo Vatta
- Unit of Foodborne and Neglected Parasitic Disease, Department of Infectious Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (G.M.); (I.Z.); (P.V.)
| | - Alex D. Greenwood
- Leibniz Institute for Zoo and Wildlife Research, 10315 Berlin, Germany;
- Department of Veterinary Medicine, Freie Universität Berlin, 14195 Berlin, Germany
| | - Annarita Fiorillo
- Department of Biochemical Science “A. Rossi-Fanelli”, Sapienza University, 00185 Rome, Italy;
| | - Marco Lalle
- Unit of Foodborne and Neglected Parasitic Disease, Department of Infectious Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy; (G.M.); (I.Z.); (P.V.)
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22
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Identification of amino acid residues required for inhibition of host gene expression by influenza A/Viet Nam/1203/2004 H5N1 PA-X. J Virol 2021; 96:e0040821. [PMID: 33853954 DOI: 10.1128/jvi.00408-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PA-X is a non-structural protein of influenza A virus (IAV), which is encoded by the polymerase acidic (PA) N-terminal region that contains a C-terminal +1 frameshifted sequence. IAV PA-X protein modulates virus-induced host innate immune responses and viral pathogenicity via suppression of host gene expression or cellular shutoff, through cellular mRNA cleavage. Highly pathogenic avian influenza viruses (HPAIV) of the H5N1 subtype naturally infect different avian species, they have an enormous economic impact in the poultry farming, and they also have zoonotic and pandemic potential, representing a risk to human public health. In the present study, we describe a novel bacteria-based approach to identify amino acid residues in the PA-X protein of the HPAIV A/Viet Nam/1203/2004 H5N1 that are important for its ability to inhibit host protein expression or cellular shutoff activity. Identified PA-X mutants displayed a reduced shutoff activity as compared to that of the wild-type (WT) A/Viet Nam/1203/2004 H5N1 PA-X protein. Notably, this new bacteria-based screening allowed us to identify amino acid residues widely distributed over the entire N-terminal region of PA-X. Furthermore, we found that some of the residues affecting A/Viet Nam/1203/2004 H5N1 PA-X host shutoff activity also affect PA polymerase activity in a minigenome assay. This information could be used for the rational design of new and more effective compounds with antiviral activity against IAV. Moreover, our results demonstrate the feasibility of using this bacteria-based approach to identify amino acid residues important for the activity of viral proteins to inhibit host gene expression. IMPORTANCE Highly pathogenic avian influenza viruses (HPAIV) continue to pose a huge threat to global animal and human health. Despite of the limited genome size of Influenza A virus (IAV), the virus encodes eight main viral structural proteins and multiple accessory non-structural proteins, depending on the IAV type, subtype or strain. One of the IAV accessory proteins, PA-X, is encoded by the polymerase acidic (PA) protein and is involved in pathogenicity through the modulation of IAV-induced host inflammatory and innate immune responses. However, the molecular mechanism(s) of IAV PA-X regulation of the host immune response is not well understood. In this work, we used, for the first time, a bacteria-based approach for the identification of amino acids important for the ability of IAV PA-X to induce host shutoff activity and describe novel residues relevant for its ability to inhibit host gene expression, and their contribution in PA polymerase activity.
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23
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The influenza A virus host shutoff factor PA-X is rapidly turned over in a strain-specific manner. J Virol 2021; 95:JVI.02312-20. [PMID: 33504608 PMCID: PMC8103685 DOI: 10.1128/jvi.02312-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The influenza A endoribonuclease PA-X regulates virulence and transmission of the virus by reducing host gene expression and thus regulating immune responses to influenza A virus. Despite this key function in viral biology, the levels of PA-X protein remain markedly low during infection, and previous results suggest that these low levels are not solely the result of regulation of the level of translation and RNA stability. How PA-X is regulated post-translationally remains unknown. We now report that the PA-X protein is rapidly turned over. PA-X from multiple viral strains are short-lived, although the half-life of PA-X ranges from ∼30 minutes to ∼3.5 hours depending on the strain. Moreover, sequences in the variable PA-X C-terminal domain are primarily responsible for regulating PA-X half-life, although the N-terminal domain also accounts for some differences among strains. Interestingly, we find that the PA-X from the 2009 pandemic H1N1 strain has a longer half-life compared to the other variants we tested. This PA-X isoform has been reported to have a higher host shutoff activity, suggesting a role for protein turnover in regulating PA-X activity. Collectively, this study reveals a novel regulatory mechanism of PA-X protein levels that may impact host shutoff activity during influenza A virus infection.IMPORTANCE The PA-X protein from influenza A virus reduces host immune responses to infection through suppressing host gene expression, including genes encoding the antiviral response. Thus, it plays a central role in influenza A virus biology. Despite its key function, PA-X was only discovered in 2012 and much remains to be learned including how PA-X activity is regulated to promote optimal levels of viral infection. In this study, we reveal that PA-X protein levels are very low likely because of rapid turnover. We show that instability is a conserved property among PA-X variants from different strains of influenza A virus, but that the half-lives of PA-X variants differ. Moreover, the longer half-life of PA-X from the 2009 pandemic H1N1 strain correlates with its reported higher activity. Therefore, PA-X stability may be a way to regulate its activity and may contribute to the differential virulence of influenza A virus strains.
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24
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McKellar J, Rebendenne A, Wencker M, Moncorgé O, Goujon C. Mammalian and Avian Host Cell Influenza A Restriction Factors. Viruses 2021; 13:522. [PMID: 33810083 PMCID: PMC8005160 DOI: 10.3390/v13030522] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/12/2021] [Accepted: 03/15/2021] [Indexed: 12/27/2022] Open
Abstract
The threat of a new influenza pandemic is real. With past pandemics claiming millions of lives, finding new ways to combat this virus is essential. Host cells have developed a multi-modular system to detect incoming pathogens, a phenomenon called sensing. The signaling cascade triggered by sensing subsequently induces protection for themselves and their surrounding neighbors, termed interferon (IFN) response. This response induces the upregulation of hundreds of interferon-stimulated genes (ISGs), including antiviral effectors, establishing an antiviral state. As well as the antiviral proteins induced through the IFN system, cells also possess a so-called intrinsic immunity, constituted of antiviral proteins that are constitutively expressed, creating a first barrier preceding the induction of the interferon system. All these combined antiviral effectors inhibit the virus at various stages of the viral lifecycle, using a wide array of mechanisms. Here, we provide a review of mammalian and avian influenza A restriction factors, detailing their mechanism of action and in vivo relevance, when known. Understanding their mode of action might help pave the way for the development of new influenza treatments, which are absolutely required if we want to be prepared to face a new pandemic.
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Affiliation(s)
- Joe McKellar
- Institut de Recherche en Infectiologie de Montpellier, CNRS, Université de Montpellier, CEDEX 5, 34293 Montpellier, France; (J.M.); (A.R.)
| | - Antoine Rebendenne
- Institut de Recherche en Infectiologie de Montpellier, CNRS, Université de Montpellier, CEDEX 5, 34293 Montpellier, France; (J.M.); (A.R.)
| | - Mélanie Wencker
- Centre International de Recherche en Infectiologie, INSERM/CNRS/UCBL1/ENS de Lyon, 69007 Lyon, France;
| | - Olivier Moncorgé
- Institut de Recherche en Infectiologie de Montpellier, CNRS, Université de Montpellier, CEDEX 5, 34293 Montpellier, France; (J.M.); (A.R.)
| | - Caroline Goujon
- Institut de Recherche en Infectiologie de Montpellier, CNRS, Université de Montpellier, CEDEX 5, 34293 Montpellier, France; (J.M.); (A.R.)
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25
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Clements AL, Peacock TP, Sealy JE, Lee HM, Hussain S, Sadeyen JR, Shelton H, Digard P, Iqbal M. PA-X is an avian virulence factor in H9N2 avian influenza virus. J Gen Virol 2021; 102:001531. [PMID: 33544070 PMCID: PMC8515854 DOI: 10.1099/jgv.0.001531] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 11/03/2020] [Indexed: 12/12/2022] Open
Abstract
Influenza A viruses encode several accessory proteins that have host- and strain-specific effects on virulence and replication. The accessory protein PA-X is expressed due to a ribosomal frameshift during translation of the PA gene. Depending on the particular combination of virus strain and host species, PA-X has been described as either acting to reduce or increase virulence and/or virus replication. In this study, we set out to investigate the role PA-X plays in H9N2 avian influenza viruses, focusing on the natural avian host, chickens. We found that the G1 lineage A/chicken/Pakistan/UDL-01/2008 (H9N2) PA-X induced robust host shutoff in both mammalian and avian cells and increased virus replication in mammalian, but not avian cells. We further showed that PA-X affected embryonic lethality in ovo and led to more rapid viral shedding and widespread organ dissemination in vivo in chickens. Overall, we conclude PA-X may act as a virulence factor for H9N2 viruses in chickens, allowing faster replication and wider organ tropism.
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Affiliation(s)
- Anabel L. Clements
- The Pirbright Institute, Pirbright, Woking, GU24 0NF, UK
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, EH25 9RG, UK
| | - Thomas P. Peacock
- The Pirbright Institute, Pirbright, Woking, GU24 0NF, UK
- Department of Infectious Diseases, Imperial College London, W2 1PG, UK
| | | | - Hui Min Lee
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, EH25 9RG, UK
| | - Saira Hussain
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, EH25 9RG, UK
- Present address: The Francis Crick Institute, London, NW1 1AT, UK
| | | | - Holly Shelton
- The Pirbright Institute, Pirbright, Woking, GU24 0NF, UK
| | - Paul Digard
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, EH25 9RG, UK
| | - Munir Iqbal
- The Pirbright Institute, Pirbright, Woking, GU24 0NF, UK
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26
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Li M, Qi W, Chang Q, Chen R, Zhen D, Liao M, Wen J, Deng Y. Influenza A virus protein PA-X suppresses host Ankrd17-mediated immune responses. Microbiol Immunol 2021; 65:48-59. [PMID: 33241870 DOI: 10.1111/1348-0421.12863] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 11/16/2020] [Accepted: 11/19/2020] [Indexed: 11/30/2022]
Abstract
Influenza A virus (IAV) PA-X is a critical ribonuclease protein involved in host cell shutoff but its role in modulating the host immune response to IAV infection remains to be addressed. In this study, host cellular proteins that directly interact with PA-X were screened to investigate the biological function of PA-X in the pathogenesis of IAV infection. The protein ankyrin repeat domain 17 (Ankrd17), a positive regulator of inflammatory responses via the retinoic acid-inducible gene-I (RIG-I)-like receptor (RLR) signaling pathway, was identified as a specific PA-X binding partner that preferred PA-X to the PA protein. The N-terminal ankyrin repeats of Ankrd17 are the key domain for the interaction with PA-X rather than PA, which is required for the function of Ankrd17 in elevating the host immune response. Using Ankrd17 knockout and overexpression, we confirmed that PA-X significantly affected the Ankrd17-mediated response to infection in host cells. Our data therefore reveal a novel function for PA-X in the regulation of innate immune pathways via the interaction between PA-X and Ankrd17.
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Affiliation(s)
- Mai Li
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Guangdong Food and Drug Vocational College, Guangzhou, China.,Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China
| | - Wenbao Qi
- Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China.,National and Regional Joint Engineering Laboratory for Medicament of Zoonoses Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Qing Chang
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Ruohong Chen
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China
| | - Danlin Zhen
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Ming Liao
- Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China.,National and Regional Joint Engineering Laboratory for Medicament of Zoonoses Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Jikai Wen
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China
| | - Yiqun Deng
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China
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27
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Burrows JTA, Depierreux D, Nibert ML, Pearson BJ. A Novel Taxon of Monosegmented Double-Stranded RNA Viruses Endemic to Triclad Flatworms. J Virol 2020; 94:e00623-20. [PMID: 32907972 PMCID: PMC7592200 DOI: 10.1128/jvi.00623-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 09/01/2020] [Indexed: 12/12/2022] Open
Abstract
Freshwater planarians, flatworms from order Tricladida, are experimental models of stem cell biology and tissue regeneration. An aspect of their biology that remains less well studied is their relationship with viruses that may infect them. In this study, we identified a taxon of monosegmented double-stranded RNA (dsRNA) viruses in five planarian species, including the well-characterized model Schmidtea mediterranea Sequences for the S. mediterranea virus (abbreviated SmedTV for S. mediterranea tricladivirus) were found in public transcriptome data from multiple institutions, indicating that SmedTV is prevalent in S. mediterranea lab colonies, though without causing evident disease. The presence of SmedTV in discrete cells was shown through in situ hybridization methods for detecting the viral RNA. SmedTV-staining cells were found to be concentrated in neural structures (eyes and brain) but were also scattered in other worm tissues as well. In contrast, few SmedTV-staining cells were seen in stem cell compartments (also consistent with RNA sequencing data) or early blastema tissue. RNA interference (RNAi) targeted to the SmedTV sequence led to apparent cure of infection, though effects on worm health or behavior were not observed. Efforts to transmit SmedTV horizontally through microinjection were unsuccessful. Based on these findings, we conclude that SmedTV infects S. mediterranea in a persistent manner and undergoes vertical transmission to progeny worms during serial passage in lab colonies. The utility of S. mediterranea as a regeneration model, coupled with the apparent capacity of SmedTV to evade normal host immune/RNAi defenses under standard conditions, argues that further studies are warranted to explore this newly recognized virus-host system.IMPORTANCE Planarians are freshwater flatworms, related more distantly to tapeworms and flukes, and have been developed as models to study the molecular mechanisms of stem cell biology and tissue regeneration. These worms live in aquatic environments, where they are likely to encounter a variety of viruses, bacteria, and eukaryotic organisms with pathogenic potential. How the planarian immune system has evolved to cope with these potential pathogens is not well understood, and only two types of planarian viruses have been described to date. Here, we report discovery and inaugural studies of a novel taxon of dsRNA viruses in five different planarian species. The virus in the best-characterized model species, Schmidtea mediterranea, appears to persist long term in that host while avoiding endogenous antiviral or RNAi mechanisms. The S. mediterranea virus-host system thus seems to offer opportunity for gaining new insights into host defenses and their evolution in an important lab model.
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Affiliation(s)
- Jeffrey T A Burrows
- The Hospital for Sick Children, Program in Developmental and Stem Cell Biology, Toronto, Ontario, Canada
- Ontario Institute for Cancer Research, Toronto, Ontario, Canada
| | - Delphine Depierreux
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Max L Nibert
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Bret J Pearson
- The Hospital for Sick Children, Program in Developmental and Stem Cell Biology, Toronto, Ontario, Canada
- Ontario Institute for Cancer Research, Toronto, Ontario, Canada
- University of Toronto, Department of Molecular Genetics, Toronto, Ontario, Canada
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28
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Roles of the Non-Structural Proteins of Influenza A Virus. Pathogens 2020; 9:pathogens9100812. [PMID: 33023047 PMCID: PMC7600879 DOI: 10.3390/pathogens9100812] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 09/29/2020] [Accepted: 10/01/2020] [Indexed: 12/11/2022] Open
Abstract
Influenza A virus (IAV) is a segmented, negative single-stranded RNA virus that causes seasonal epidemics and has a potential for pandemics. Several viral proteins are not packed in the IAV viral particle and only expressed in the infected host cells. These proteins are named non-structural proteins (NSPs), including NS1, PB1-F2 and PA-X. They play a versatile role in the viral life cycle by modulating viral replication and transcription. More importantly, they also play a critical role in the evasion of the surveillance of host defense and viral pathogenicity by inducing apoptosis, perturbing innate immunity, and exacerbating inflammation. Here, we review the recent advances of these NSPs and how the new findings deepen our understanding of IAV–host interactions and viral pathogenesis.
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29
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Clements AL, Sealy JE, Peacock TP, Sadeyen JR, Hussain S, Lycett SJ, Shelton H, Digard P, Iqbal M. Contribution of Segment 3 to the Acquisition of Virulence in Contemporary H9N2 Avian Influenza Viruses. J Virol 2020; 94:e01173-20. [PMID: 32727875 PMCID: PMC7527061 DOI: 10.1128/jvi.01173-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 07/27/2020] [Indexed: 12/16/2022] Open
Abstract
H9N2 avian influenza viruses (AIVs) circulate in poultry throughout much of Asia, the Middle East, and Africa. These viruses cause huge economic damage to poultry production systems and pose a zoonotic threat both in their own right and in the generation of novel zoonotic viruses, for example, H7N9. In recent years, it has been observed that H9N2 viruses have further adapted to gallinaceous poultry, becoming more highly transmissible and causing higher morbidity and mortality. Here, we investigate the molecular basis for this increased virulence, comparing a virus from the 1990s and a contemporary field strain. The modern virus replicated to higher titers in various systems, and this difference mapped to a single amino acid polymorphism at position 26 of the endonuclease domain shared by the PA and PA-X proteins. This change was responsible for increased replication and higher morbidity and mortality rates along with extended tissue tropism seen in chickens. Although the PA K26E change correlated with increased host cell shutoff activity of the PA-X protein in vitro, it could not be overridden by frameshift site mutations that block PA-X expression and therefore increased PA-X activity could not explain the differences in replication phenotype. Instead, this indicates that these differences are due to subtle effects on PA function. This work gives insight into the ongoing evolution and poultry adaptation of H9N2 and other avian influenza viruses and helps us understand the striking morbidity and mortality rates in the field, as well as the rapidly expanding geographical range seen in these viruses.IMPORTANCE Avian influenza viruses, such as H9N2, cause huge economic damage to poultry production worldwide and are additionally considered potential pandemic threats. Understanding how these viruses evolve in their natural hosts is key to effective control strategies. In the Middle East and South Asia, an older H9N2 virus strain has been replaced by a new reassortant strain with greater fitness. Here, we take representative viruses and investigate the genetic basis for this "fitness." A single mutation in the virus was responsible for greater fitness, enabling high growth of the contemporary H9N2 virus in cells, as well as in chickens. The genetic mutation that modulates this change is within the viral PA protein, a part of the virus polymerase gene that contributes to viral replication as well as to virus accessory functions-however, we find that the fitness effect is specifically due to changes in the protein polymerase activity.
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Affiliation(s)
- Anabel L Clements
- The Pirbright Institute, Pirbright, Woking, United Kingdom
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Joshua E Sealy
- The Pirbright Institute, Pirbright, Woking, United Kingdom
| | - Thomas P Peacock
- The Pirbright Institute, Pirbright, Woking, United Kingdom
- Department of Infectious Diseases, Imperial College London, United Kingdom
| | | | - Saira Hussain
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Samantha J Lycett
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Holly Shelton
- The Pirbright Institute, Pirbright, Woking, United Kingdom
| | - Paul Digard
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Munir Iqbal
- The Pirbright Institute, Pirbright, Woking, United Kingdom
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30
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Malik G, Zhou Y. Innate Immune Sensing of Influenza A Virus. Viruses 2020; 12:E755. [PMID: 32674269 PMCID: PMC7411791 DOI: 10.3390/v12070755] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/09/2020] [Accepted: 07/10/2020] [Indexed: 12/18/2022] Open
Abstract
Influenza virus infection triggers host innate immune response by stimulating various pattern recognition receptors (PRRs). Activation of these PRRs leads to the activation of a plethora of signaling pathways, resulting in the production of interferon (IFN) and proinflammatory cytokines, followed by the expression of interferon-stimulated genes (ISGs), the recruitment of innate immune cells, or the activation of programmed cell death. All these antiviral approaches collectively restrict viral replication inside the host. However, influenza virus also engages in multiple mechanisms to subvert the innate immune responses. In this review, we discuss the role of PRRs such as Toll-like receptors (TLRs), Retinoic acid-inducible gene I (RIG-I), NOD-, LRR-, pyrin domain-containing protein 3 (NLRP3), and Z-DNA binding protein 1 (ZBP1) in sensing and restricting influenza viral infection. Further, we also discuss the mechanisms influenza virus utilizes, especially the role of viral non-structure proteins NS1, PB1-F2, and PA-X, to evade the host innate immune responses.
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Affiliation(s)
- Gaurav Malik
- Vaccine and Infectious Disease Organization-International Vaccine Centre (VIDO-InterVac), University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada;
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
| | - Yan Zhou
- Vaccine and Infectious Disease Organization-International Vaccine Centre (VIDO-InterVac), University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada;
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
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31
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Penn WD, Harrington HR, Schlebach JP, Mukhopadhyay S. Regulators of Viral Frameshifting: More Than RNA Influences Translation Events. Annu Rev Virol 2020; 7:219-238. [PMID: 32600156 DOI: 10.1146/annurev-virology-012120-101548] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Programmed ribosomal frameshifting (PRF) is a conserved translational recoding mechanism found in all branches of life and viruses. In bacteria, archaea, and eukaryotes PRF is used to downregulate protein production by inducing a premature termination of translation, which triggers messenger RNA (mRNA) decay. In viruses, PRF is used to drive the production of a new protein while downregulating the production of another protein, thus maintaining a stoichiometry optimal for productive infection. Traditionally, PRF motifs have been defined by the characteristics of two cis elements: a slippery heptanucleotide sequence followed by an RNA pseudoknot or stem-loop within the mRNA. Recently, additional cis and new trans elements have been identified that regulate PRF in both host and viral translation. These additional factors suggest PRF is an evolutionarily conserved process whose function and regulation we are just beginning to understand.
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Affiliation(s)
- Wesley D Penn
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
| | - Haley R Harrington
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
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32
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Gaucherand L, Porter BK, Levene RE, Price EL, Schmaling SK, Rycroft CH, Kevorkian Y, McCormick C, Khaperskyy DA, Gaglia MM. The Influenza A Virus Endoribonuclease PA-X Usurps Host mRNA Processing Machinery to Limit Host Gene Expression. Cell Rep 2020; 27:776-792.e7. [PMID: 30995476 PMCID: PMC6499400 DOI: 10.1016/j.celrep.2019.03.063] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 02/08/2019] [Accepted: 03/15/2019] [Indexed: 12/29/2022] Open
Abstract
Many viruses shut off host gene expression to inhibit antiviral responses. Viral proteins and host proteins required for viral replication are typically spared in this process, but the mechanisms of target selectivity during host shutoff remain poorly understood. Using transcriptome-wide and targeted reporter experiments, we demonstrate that the influenza A virus endoribonuclease PA-X usurps RNA splicing to selectively target host RNAs for destruction. Proximity-labeling proteomics reveals that PA-X interacts with cellular RNA processing proteins, some of which are partially required for host shutoff. Thus, PA-X taps into host nuclear pre-mRNA processing mechanisms to destroy nascent mRNAs shortly after their synthesis. This mechanism sets PA-X apart from other viral host shutoff proteins that target actively translating mRNAs in the cytoplasm. Our study reveals a unique mechanism of host shutoff that helps us understand how influenza viruses suppress host gene expression. Influenza A virus PA-X targets the majority of host mRNAs for destruction Downregulation by PA-X correlates with the number of splice sites in a transcript Splicing renders RNAs susceptible to PA-X The cellular CFIm complex interacts with PA-X and contributes to PA-X activity
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Affiliation(s)
- Lea Gaucherand
- Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, USA; Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Brittany K Porter
- Department of Microbiology & Immunology, Dalhousie University, Halifax, NS, Canada
| | - Rachel E Levene
- Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, USA; Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Emma L Price
- Department of Microbiology & Immunology, Dalhousie University, Halifax, NS, Canada
| | - Summer K Schmaling
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Chris H Rycroft
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA; Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Yuzo Kevorkian
- Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, USA; Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Craig McCormick
- Department of Microbiology & Immunology, Dalhousie University, Halifax, NS, Canada.
| | - Denys A Khaperskyy
- Department of Microbiology & Immunology, Dalhousie University, Halifax, NS, Canada.
| | - Marta M Gaglia
- Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, USA; Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.
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33
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Comparative Genomics of Two New HF1-like Haloviruses. Genes (Basel) 2020; 11:genes11040405. [PMID: 32276506 PMCID: PMC7230728 DOI: 10.3390/genes11040405] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/03/2020] [Accepted: 04/06/2020] [Indexed: 12/14/2022] Open
Abstract
Few genomes of the HF1-group of viruses are currently available, and further examples would enhance the understanding of their evolution, improve their gene annotation, and assist in understanding gene function and regulation. Two novel HF1-group haloviruses, Serpecor1 and Hardycor2, were recovered from widely separated hypersaline lakes in Australia. Both are myoviruses with linear dsDNA genomes and infect the haloarchaeon Halorubrum coriense. Both genomes possess long, terminal direct repeat (TDR) sequences (320 bp for Serpecor1 and 306 bp for Hardycor2). The Serpecor1 genome is 74,196 bp in length, 57.0% G+C, and has 126 annotated coding sequences (CDS). Hardycor2 has a genome of 77,342 bp, 55.6% G+C, and 125 annotated CDS. They show high nucleotide sequence similarity to each other (78%) and with HF1 (>75%), and carry similar intergenic repeat (IR) sequences to those originally described in HF1 and HF2. Hardycor2 carries a DNA methyltransferase gene in the same genomic neighborhood as the methyltransferase genes of HF1, HF2 and HRTV-5, but is in the opposite orientation, and the inferred proteins are only distantly related. Comparative genomics allowed us to identify the candidate genes mediating cell attachment. The genomes of Serpecor1 and Hardycor2 encode numerous small proteins carrying one or more CxxC motifs, a signature feature of zinc-finger domain proteins that are known to participate in diverse biomolecular interactions.
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34
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Lutz MM, Dunagan MM, Kurebayashi Y, Takimoto T. Key Role of the Influenza A Virus PA Gene Segment in the Emergence of Pandemic Viruses. Viruses 2020; 12:v12040365. [PMID: 32224899 PMCID: PMC7232137 DOI: 10.3390/v12040365] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 03/24/2020] [Indexed: 12/18/2022] Open
Abstract
Influenza A viruses (IAVs) are a significant human pathogen that cause seasonal epidemics and occasional pandemics. Avian waterfowl are the natural reservoir of IAVs, but a wide range of species can serve as hosts. Most IAV strains are adapted to one host species and avian strains of IAV replicate poorly in most mammalian hosts. Importantly, IAV polymerases from avian strains function poorly in mammalian cells but host adaptive mutations can restore activity. The 2009 pandemic H1N1 (H1N1pdm09) virus acquired multiple mutations in the PA gene that activated polymerase activity in mammalian cells, even in the absence of previously identified host adaptive mutations in other polymerase genes. These mutations in PA localize within different regions of the protein suggesting multiple mechanisms exist to activate polymerase activity. Additionally, an immunomodulatory protein, PA-X, is expressed from the PA gene segment. PA-X expression is conserved amongst many IAV strains but activity varies between viruses specific for different hosts, suggesting that PA-X also plays a role in host adaptation. Here, we review the role of PA in the emergence of currently circulating H1N1pdm09 viruses and the most recent studies of host adaptive mutations in the PA gene that modulate polymerase activity and PA-X function.
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Affiliation(s)
- Michael M. Lutz
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
| | - Megan M. Dunagan
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
| | - Yuki Kurebayashi
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka-shi 422-8526, Japan
| | - Toru Takimoto
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
- Correspondence: ; Tel.: +1-585-273-2856
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N-Terminal Acetylation by NatB Is Required for the Shutoff Activity of Influenza A Virus PA-X. Cell Rep 2020; 24:851-860. [PMID: 30044982 DOI: 10.1016/j.celrep.2018.06.078] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 03/26/2018] [Accepted: 06/18/2018] [Indexed: 12/17/2022] Open
Abstract
N-terminal acetylation is a major posttranslational modification in eukaryotes catalyzed by N-terminal acetyltransferases (NATs), NatA through NatF. Although N-terminal acetylation modulates diverse protein functions, little is known about its roles in virus replication. We found that NatB, which comprises NAA20 and NAA25, is involved in the shutoff activity of influenza virus PA-X. The shutoff activity of PA-X was suppressed in NatB-deficient cells, and PA-X mutants that are not acetylated by NatB showed reduced shutoff activities. We also evaluated the importance of N-terminal acetylation of PA, because PA-X shares its N-terminal sequence with PA. Viral polymerase activity was reduced in NatB-deficient cells. Moreover, mutant PAs that are not acetylated by NatB lost their function in the viral polymerase complex. Taken together, our findings demonstrate that N-terminal acetylation is required for the shutoff activity of PA-X and for viral polymerase activity.
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Dawson WK, Lazniewski M, Plewczynski D. RNA structure interactions and ribonucleoprotein processes of the influenza A virus. Brief Funct Genomics 2019; 17:402-414. [PMID: 29040388 PMCID: PMC6252904 DOI: 10.1093/bfgp/elx028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In one more years, we will ‘celebrate’ an exact centenary of the Spanish flu pandemic. With the rapid evolution of the influenza virus, the possibility of novel pandemic remains ever a concern. This review covers our current knowledge of the influenza A virus: on the role of RNA in translation, replication, what is known of the expressed proteins and the protein products generated from alternative splicing, and on the role of base pairing in RNA structure. We highlight the main events associated with viral entry into the cell, the transcription and replication process, an export of the viral genetic material from the nucleus and the final release of the virus. We discuss the observed potential roles of RNA secondary structure (the RNA base-pairing arrangement) and RNA/RNA interactions in this scheme.
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Affiliation(s)
- Wayne K Dawson
- Bio-information Lab, University of Tokyo.,University of Warsaw, Center of New Technologies (CeNT), Warsaw, Poland
| | - Michal Lazniewski
- University of Warsaw, Center of New Technologies (CeNT), Warsaw, Poland
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Detection and Characterization of Cucumis melo Cryptic Virus, Cucumis melo Amalgavirus 1, and Melon Necrotic Spot Virus in Cucumis melo. Viruses 2019; 11:v11010081. [PMID: 30669373 PMCID: PMC6356274 DOI: 10.3390/v11010081] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 01/06/2019] [Accepted: 01/11/2019] [Indexed: 12/15/2022] Open
Abstract
Three RNA viruses—Cucumis melo cryptic virus (CmCV), Cucumis melo amalgavirus 1 (CmAV1), and melon necrotic spot virus (MNSV)—were identified from a melon (Cucumis melo) transcriptome dataset. CmCV has two dsRNA genome segments; dsRNA-1 is 1592 bp in size, containing a conserved RNA-dependent RNA polymerase (RdRp), and dsRNA-2 is 1715 bp in size, and encodes a coat protein (CP). The sequence alignment and phylogenetic analyses of the CmCV RdRp and CP indicated CmCV clusters with approved or putative deltapartitiviruses in well-supported monophyletic clade. The RdRp of CmCV shared an amino acid sequence identity of 60.7% with the closest RdRp of beet cryptic virus 3, and is <57% identical to other partitiviruses. CmAV1 is a nonsegmented dsRNA virus with a genome of 3424 bp, including two partially overlapping open reading frames (ORFs) encoding a putative CP and RdRp. The sequence alignment and phylogenetic analyses of CmAV1 RdRp revealed that it belongs to the genus Amalgavirus in the family Amalgaviridae. The RdRp of CmAV1 shares 57.7% of its amino acid sequence identity with the most closely related RdRp of Phalaenopsis equestris amalgavirus 1, and is <47% identical to the other reported amalgaviruses. These analyses suggest that CmCV and CmAV1 are novel species in the genera Amalgavirus and Deltapartitivirus, respectively. These findings enrich our understanding of new plant dsRNA virus species.
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Mutation of Influenza A Virus PA-X Decreases Pathogenicity in Chicken Embryos and Can Increase the Yield of Reassortant Candidate Vaccine Viruses. J Virol 2019; 93:JVI.01551-18. [PMID: 30381488 PMCID: PMC6321911 DOI: 10.1128/jvi.01551-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 10/25/2018] [Indexed: 01/08/2023] Open
Abstract
Influenza A virus is a widespread pathogen that affects both humans and a variety of animal species, causing regular epidemics and sporadic pandemics, with major public health and economic consequences. A better understanding of virus biology is therefore important. The primary control measure is vaccination, which for humans mostly relies on antigens produced in eggs from PR8-based viruses bearing the glycoprotein genes of interest. However, not all reassortants replicate well enough to supply sufficient virus antigen for demand. The significance of our research lies in identifying that mutation of the PA-X gene in the PR8 strain of virus can improve antigen yield, potentially by decreasing the pathogenicity of the virus in embryonated eggs. The PA-X protein of influenza A virus has roles in host cell shutoff and viral pathogenesis. While most strains are predicted to encode PA-X, strain-dependent variations in activity have been noted. We found that PA-X protein from the A/PR/8/34 (PR8) strain had significantly lower repressive activity against cellular gene expression than PA-X proteins from the avian strains A/turkey/England/50-92/91 (H5N1) (T/E) and A/chicken/Rostock/34 (H7N1). Loss of normal PA-X expression, either by mutation of the frameshift site or by truncating the X open reading frame (ORF), had little effect on the infectious virus titer of PR8 or PR8 7:1 reassortants with T/E segment 3 grown in embryonated hens’ eggs. However, in both virus backgrounds, mutation of PA-X led to decreased embryo mortality and lower overall pathology, effects that were more pronounced in the PR8 strain than in the T/E reassortant, despite the low shutoff activity of the PR8 PA-X. Purified PA-X mutant virus particles displayed an increased ratio of hemagglutinin (HA) to nucleoprotein (NP) and M1 compared to values for their wild-type (WT) counterparts, suggesting altered virion composition. When the PA-X gene was mutated in the background of poorly growing PR8 6:2 vaccine reassortant analogues containing the HA and neuraminidase (NA) segments from H1N1 2009 pandemic viruses or from an avian H7N3 strain, HA yield increased up to 2-fold. This suggests that the PR8 PA-X protein may harbor a function unrelated to host cell shutoff and that disruption of the PA-X gene has the potential to improve the HA yield of vaccine viruses. IMPORTANCE Influenza A virus is a widespread pathogen that affects both humans and a variety of animal species, causing regular epidemics and sporadic pandemics, with major public health and economic consequences. A better understanding of virus biology is therefore important. The primary control measure is vaccination, which for humans mostly relies on antigens produced in eggs from PR8-based viruses bearing the glycoprotein genes of interest. However, not all reassortants replicate well enough to supply sufficient virus antigen for demand. The significance of our research lies in identifying that mutation of the PA-X gene in the PR8 strain of virus can improve antigen yield, potentially by decreasing the pathogenicity of the virus in embryonated eggs.
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Nogales A, Martinez-Sobrido L, Topham DJ, DeDiego ML. Modulation of Innate Immune Responses by the Influenza A NS1 and PA-X Proteins. Viruses 2018; 10:v10120708. [PMID: 30545063 PMCID: PMC6315843 DOI: 10.3390/v10120708] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 12/06/2018] [Accepted: 12/08/2018] [Indexed: 12/14/2022] Open
Abstract
Influenza A viruses (IAV) can infect a broad range of animal hosts, including humans. In humans, IAV causes seasonal annual epidemics and occasional pandemics, representing a serious public health and economic problem, which is most effectively prevented through vaccination. The defense mechanisms that the host innate immune system provides restrict IAV replication and infection. Consequently, to successfully replicate in interferon (IFN)-competent systems, IAV has to counteract host antiviral activities, mainly the production of IFN and the activities of IFN-induced host proteins that inhibit virus replication. The IAV multifunctional proteins PA-X and NS1 are virulence factors that modulate the innate immune response and virus pathogenicity. Notably, these two viral proteins have synergistic effects in the inhibition of host protein synthesis in infected cells, although using different mechanisms of action. Moreover, the control of innate immune responses by the IAV NS1 and PA-X proteins is subject to a balance that can determine virus pathogenesis and fitness, and recent evidence shows co-evolution of these proteins in seasonal viruses, indicating that they should be monitored for enhanced virulence. Importantly, inhibition of host gene expression by the influenza NS1 and/or PA-X proteins could be explored to develop improved live-attenuated influenza vaccines (LAIV) by modulating the ability of the virus to counteract antiviral host responses. Likewise, both viral proteins represent a reasonable target for the development of new antivirals for the control of IAV infections. In this review, we summarize the role of IAV NS1 and PA-X in controlling the antiviral response during viral infection.
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Affiliation(s)
- Aitor Nogales
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- Centro de Investigación en Sanidad Animal (CISA)-INIA, Valdeolmos, 28130 Madrid, Spain.
| | - Luis Martinez-Sobrido
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
| | - David J Topham
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
| | - Marta L DeDiego
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain.
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Pavesi A, Vianelli A, Chirico N, Bao Y, Blinkova O, Belshaw R, Firth A, Karlin D. Overlapping genes and the proteins they encode differ significantly in their sequence composition from non-overlapping genes. PLoS One 2018; 13:e0202513. [PMID: 30339683 PMCID: PMC6195259 DOI: 10.1371/journal.pone.0202513] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 08/03/2018] [Indexed: 11/19/2022] Open
Abstract
Overlapping genes represent a fascinating evolutionary puzzle, since they encode two functionally unrelated proteins from the same DNA sequence. They originate by a mechanism of overprinting, in which point mutations in an existing frame allow the expression (the "birth") of a completely new protein from a second frame. In viruses, in which overlapping genes are abundant, these new proteins often play a critical role in infection, yet they are frequently overlooked during genome annotation. This results in erroneous interpretation of mutational studies and in a significant waste of resources. Therefore, overlapping genes need to be correctly detected, especially since they are now thought to be abundant also in eukaryotes. Developing better detection methods and conducting systematic evolutionary studies require a large, reliable benchmark dataset of known cases. We thus assembled a high-quality dataset of 80 viral overlapping genes whose expression is experimentally proven. Many of them were not present in databases. We found that overall, overlapping genes differ significantly from non-overlapping genes in their nucleotide and amino acid composition. In particular, the proteins they encode are enriched in high-degeneracy amino acids and depleted in low-degeneracy ones, which may alleviate the evolutionary constraints acting on overlapping genes. Principal component analysis revealed that the vast majority of overlapping genes follow a similar composition bias, despite their heterogeneity in length and function. Six proven mammalian overlapping genes also followed this bias. We propose that this apparently near-universal composition bias may either favour the birth of overlapping genes, or/and result from selection pressure acting on them.
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Affiliation(s)
- Angelo Pavesi
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, Italy
| | - Alberto Vianelli
- Department of Theoretical and Applied Sciences, University of Insubria, Varese, Italy
| | - Nicola Chirico
- Department of Theoretical and Applied Sciences, University of Insubria, Varese, Italy
| | - Yiming Bao
- BIG Data Center, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Olga Blinkova
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, United States of America
| | - Robert Belshaw
- School of Biomedical & Healthcare Sciences, Plymouth University Peninsula Schools of Medicine and Dentistry (PUPSMD), Plymouth, United Kingdom
| | - Andrew Firth
- Department of Pathology, Division of Virology, University of Cambridge, Cambridge, United Kingdom
| | - David Karlin
- Department of Zoology, University of Oxford, Oxford, United Kingdom
- Division of Structural Biology, University of Oxford, Oxford, United Kingdom
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Levene RE, Gaglia MM. Host Shutoff in Influenza A Virus: Many Means to an End. Viruses 2018; 10:E475. [PMID: 30189604 PMCID: PMC6165434 DOI: 10.3390/v10090475] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 08/31/2018] [Accepted: 09/01/2018] [Indexed: 12/21/2022] Open
Abstract
Influenza A virus carries few of its own proteins, but uses them effectively to take control of the infected cells and avoid immune responses. Over the years, host shutoff, the widespread down-regulation of host gene expression, has emerged as a key process that contributes to cellular takeover in infected cells. Interestingly, multiple mechanisms of host shutoff have been described in influenza A virus, involving changes in translation, RNA synthesis and stability. Several viral proteins, notably the non-structural protein NS1, the RNA-dependent RNA polymerase and the endoribonuclease PA-X have been implicated in host shutoff. This multitude of host shutoff mechanisms indicates that host shutoff is an important component of the influenza A virus replication cycle. Here we review the various mechanisms of host shutoff in influenza A virus and the evidence that they contribute to immune evasion and/or viral replication. We also discuss what the purpose of having multiple mechanisms may be.
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Affiliation(s)
- Rachel Emily Levene
- Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA 02111, USA.
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Ave, Boston, MA 02111, USA.
| | - Marta Maria Gaglia
- Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA 02111, USA.
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Ave, Boston, MA 02111, USA.
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A novel monopartite dsRNA virus isolated from the phytopathogenic fungus Ustilaginoidea virens strain GZ-2. Arch Virol 2018; 163:3427-3431. [DOI: 10.1007/s00705-018-3976-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 07/23/2018] [Indexed: 10/28/2022]
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Park D, Goh CJ, Kim H, Hahn Y. Identification of Two Novel Amalgaviruses in the Common Eelgrass ( Zostera marina) and in Silico Analysis of the Amalgavirus +1 Programmed Ribosomal Frameshifting Sites. THE PLANT PATHOLOGY JOURNAL 2018; 34:150-156. [PMID: 29628822 PMCID: PMC5880360 DOI: 10.5423/ppj.nt.11.2017.0243] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 01/18/2018] [Accepted: 01/18/2018] [Indexed: 06/08/2023]
Abstract
The genome sequences of two novel monopartite RNA viruses were identified in a common eelgrass (Zostera marina) transcriptome dataset. Sequence comparison and phylogenetic analyses revealed that these two novel viruses belong to the genus Amalgavirus in the family Amalgaviridae. They were named Zostera marina amalgavirus 1 (ZmAV1) and Zostera marina amalgavirus 2 (ZmAV2). Genomes of both ZmAV1 and ZmAV2 contain two overlapping open reading frames (ORFs). ORF1 encodes a putative replication factory matrix-like protein, while ORF2 encodes a RNA-dependent RNA polymerase (RdRp) domain. The fusion protein (ORF1+2) of ORF1 and ORF2, which mediates RNA replication, was produced using the +1 programmed ribosomal frameshifting (PRF) mechanism. The +1 PRF motif sequence, UUU_CGN, which is highly conserved among known amalgaviruses, was also found in ZmAV1 and ZmAV2. Multiple sequence alignment of the ORF1+2 fusion proteins from 24 amalgaviruses revealed that +1 PRF occurred only at three different positions within the 13-amino acid-long segment, which was surrounded by highly conserved regions on both sides. This suggested that the +1 PRF may be constrained by the structure of fusion proteins. Genome sequences of ZmAV1 and ZmAV2, which are the first viruses to be identified in common eelgrass, will serve as useful resources for studying evolution and diversity of amalgaviruses.
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Affiliation(s)
| | | | | | - Yoonsoo Hahn
- Corresponding author. Phone) +82-2-820-5812, FAX) +82-2-825-5206, E-mail)
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Harwig A, Landick R, Berkhout B. The Battle of RNA Synthesis: Virus versus Host. Viruses 2017; 9:v9100309. [PMID: 29065472 PMCID: PMC5691660 DOI: 10.3390/v9100309] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 10/19/2017] [Accepted: 10/20/2017] [Indexed: 12/13/2022] Open
Abstract
Transcription control is the foundation of gene regulation. Whereas a cell is fully equipped for this task, viruses often depend on the host to supply tools for their transcription program. Over the course of evolution and adaptation, viruses have found diverse ways to optimally exploit cellular host processes such as transcription to their own benefit. Just as cells are increasingly understood to employ nascent RNAs in transcription regulation, recent discoveries are revealing how viruses use nascent RNAs to benefit their own gene expression. In this review, we first outline the two different transcription programs used by viruses, i.e., transcription (DNA-dependent) and RNA-dependent RNA synthesis. Subsequently, we use the distinct stages (initiation, elongation, termination) to describe the latest insights into nascent RNA-mediated regulation in the context of each relevant stage.
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Affiliation(s)
- Alex Harwig
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
| | - Robert Landick
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
| | - Ben Berkhout
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands.
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Dinan AM, Atkins JF, Firth AE. ASXL gain-of-function truncation mutants: defective and dysregulated forms of a natural ribosomal frameshifting product? Biol Direct 2017; 12:24. [PMID: 29037253 PMCID: PMC5644247 DOI: 10.1186/s13062-017-0195-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 10/04/2017] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Programmed ribosomal frameshifting (PRF) is a gene expression mechanism which enables the translation of two N-terminally coincident, C-terminally distinct protein products from a single mRNA. Many viruses utilize PRF to control or regulate gene expression, but very few phylogenetically conserved examples are known in vertebrate genes. Additional sex combs-like (ASXL) genes 1 and 2 encode important epigenetic and transcriptional regulatory proteins that control the expression of homeotic genes during key developmental stages. Here we describe an ~150-codon overlapping ORF (termed TF) in ASXL1 and ASXL2 that, with few exceptions, is conserved throughout vertebrates. RESULTS Conservation of the TF ORF, strong suppression of synonymous site variation in the overlap region, and the completely conserved presence of an EH[N/S]Y motif (a known binding site for Host Cell Factor-1, HCF-1, an epigenetic regulatory factor), all indicate that TF is a protein-coding sequence. A highly conserved UCC_UUU_CGU sequence (identical to the known site of +1 ribosomal frameshifting for influenza virus PA-X expression) occurs at the 5' end of the region of enhanced synonymous site conservation in ASXL1. Similarly, a highly conserved RG_GUC_UCU sequence (identical to a known site of -2 ribosomal frameshifting for arterivirus nsp2TF expression) occurs at the 5' end of the region of enhanced synonymous site conservation in ASXL2. CONCLUSIONS Due to a lack of appropriate splice forms, or initiation sites, the most plausible mechanism for translation of the ASXL1 and 2 TF regions is ribosomal frameshifting, resulting in a transframe fusion of the N-terminal half of ASXL1 or 2 to the TF product, termed ASXL-TF. Truncation or frameshift mutants of ASXL are linked to myeloid malignancies and genetic diseases, such as Bohring-Opitz syndrome, likely at least in part as a result of gain-of-function or dominant-negative effects. Our hypothesis now indicates that these disease-associated mutant forms represent overexpressed defective versions of ASXL-TF. REVIEWERS This article was reviewed by Laurence Hurst and Eugene Koonin.
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Affiliation(s)
- Adam M Dinan
- Department of Pathology, Division of Virology, University of Cambridge, Cambridge, CB2 1QP, UK
| | - John F Atkins
- School of Biochemistry and Cell Biology, University College Cork, T12 YT57, Cork, Ireland.,Department of Human Genetics, University of Utah, Salt Lake City, UT, 84112, USA
| | - Andrew E Firth
- Department of Pathology, Division of Virology, University of Cambridge, Cambridge, CB2 1QP, UK.
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Pyle JD, Keeling PJ, Nibert ML. Amalga-like virus infecting Antonospora locustae, a microsporidian pathogen of grasshoppers, plus related viruses associated with other arthropods. Virus Res 2017; 233:95-104. [PMID: 28267607 DOI: 10.1016/j.virusres.2017.02.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/18/2017] [Accepted: 02/21/2017] [Indexed: 12/16/2022]
Abstract
A previously reported Expressed Sequence Tag (EST) library from spores of microsporidian Antonospora locustae includes a number of clones with sequence similarities to plant amalgaviruses. Reexamining the sequence accessions from that library, we found additional such clones, contributing to a 3247-nt contig that approximates the length of an amalga-like virus genome. Using A. locustae spores stored from that previous study, and new ones obtained from the same source, we newly visualized the putative dsRNA genome of this virus and obtained amplicons yielding a 3387-nt complete genome sequence. Phylogenetic analyses suggested it as prototype strain of a new genus in family Amalgaviridae. The genome contains two partially overlapping long ORFs, with downstream ORF2 in the +1 frame relative to ORF1 and a proposed motif for +1 ribosomal frameshifting in the region of overlap. Subsequent database searches using the predicted fusion protein sequence of this new amalga-like virus identified related sequences in the transcriptome of a basal hexapod, the springtail species Tetrodontophora bielanensis. We speculate that this second new amalga-like virus (contig length, 3475 nt) likely also derived from a microsporidian, or related organism, which was associated with the springtail specimens at the time of sampling for transcriptome analysis. Other findings of interest include evidence that the ORF1 translation products of these two new amalga-like viruses contain a central region of predicted α-helical coiled coil, as recently reported for plant amalgaviruses, and transcriptome-based evidence for another new amalga-like virus in the transcriptome of another basal hexapod, the two-pronged bristletail species Campodea augens.
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Affiliation(s)
- Jesse D Pyle
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA; Harvard Ph.D. Program in Virology, Division of Medical Sciences, Harvard University, Boston, MA 02115, USA
| | - Patrick J Keeling
- Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Max L Nibert
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA; Harvard Ph.D. Program in Virology, Division of Medical Sciences, Harvard University, Boston, MA 02115, USA.
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47
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Wang R, Zhang Z, Du J, Fu Y, Liang A. Large-scale mass spectrometry-based analysis of Euplotes octocarinatus supports the high frequency of +1 programmed ribosomal frameshift. Sci Rep 2016; 6:33020. [PMID: 27597422 PMCID: PMC5011710 DOI: 10.1038/srep33020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 08/17/2016] [Indexed: 12/30/2022] Open
Abstract
Programmed ribosomal frameshifting (PRF) is commonly used to express many viral and some cellular genes. We conducted a genome-wide investigation of +1 PRF in ciliate Euplotes octocarinatus through genome and transcriptome sequencing and our results demonstrated that approximately 11.4% of genes require +1 PRF to produce complete gene products. While nucleic acid-based evidence for candidate genes with +1 PRF is strong, only very limited information is available at protein levels to date. In this study, E. octocarinatus was subjected to large-scale mass spectrometry-based analysis to verify the high frequency of +1 PRF and 226 +1 PRF gene products were identified. Based on the amino acid sequences of the peptides spanning the frameshift sites, typical frameshift motif AAA-UAR for +1 PRF in Euplotes was identified. Our data in this study provide very useful insight into the understanding of the molecular mechanism of +1 PRF.
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Affiliation(s)
- Ruanlin Wang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Zhiyun Zhang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Jun Du
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Yuejun Fu
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
| | - Aihua Liang
- Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China.,Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, China
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48
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Nibert ML, Pyle JD, Firth AE. A +1 ribosomal frameshifting motif prevalent among plant amalgaviruses. Virology 2016; 498:201-208. [PMID: 27596539 PMCID: PMC5052127 DOI: 10.1016/j.virol.2016.07.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 06/30/2016] [Accepted: 07/01/2016] [Indexed: 11/28/2022]
Abstract
Sequence accessions attributable to novel plant amalgaviruses have been found in the Transcriptome Shotgun Assembly database. Sixteen accessions, derived from 12 different plant species, appear to encompass the complete protein-coding regions of the proposed amalgaviruses, which would substantially expand the size of genus Amalgavirus from 4 current species. Other findings include evidence for UUU_CGN as a +1 ribosomal frameshifting motif prevalent among plant amalgaviruses; for a variant version of this motif found thus far in only two amalgaviruses from solanaceous plants; for a region of α-helical coiled coil propensity conserved in a central region of the ORF1 translation product of plant amalgaviruses; and for conserved sequences in a C-terminal region of the ORF2 translation product (RNA-dependent RNA polymerase) of plant amalgaviruses, seemingly beyond the region of conserved polymerase motifs. These results additionally illustrate the value of mining the TSA database and others for novel viral sequences for comparative analyses. A number of new plant amalgavirus sequences have been found in the TSA database. They provide support for a prevalent +1 frameshifting motif in amalgaviruses. A variant motif is identified in a subset of these viruses from related plants. The ORF1 product of amalgaviruses has propensity to form α-helical coiled coil. The TSA database is a useful source of new viral sequences for comparative analyses.
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Affiliation(s)
- Max L Nibert
- Department of Microbiology & Immunobiology, Harvard Medical School, Boston, MA 02115, USA; Harvard Ph.D. Program in Virology, Division of Medical Sciences, Harvard University, Boston, MA 02115, USA.
| | - Jesse D Pyle
- Harvard Ph.D. Program in Virology, Division of Medical Sciences, Harvard University, Boston, MA 02115, USA.
| | - Andrew E Firth
- Division of Virology, Department of Pathology, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 0QQ, UK.
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A novel monopartite dsRNA virus isolated from the entomopathogenic and nematophagous fungus Purpureocillium lilacinum. Arch Virol 2016; 161:3375-3384. [DOI: 10.1007/s00705-016-3045-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 08/31/2016] [Indexed: 12/01/2022]
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50
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Atkins JF, Loughran G, Bhatt PR, Firth AE, Baranov PV. Ribosomal frameshifting and transcriptional slippage: From genetic steganography and cryptography to adventitious use. Nucleic Acids Res 2016; 44:7007-78. [PMID: 27436286 PMCID: PMC5009743 DOI: 10.1093/nar/gkw530] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/26/2016] [Indexed: 12/15/2022] Open
Abstract
Genetic decoding is not ‘frozen’ as was earlier thought, but dynamic. One facet of this is frameshifting that often results in synthesis of a C-terminal region encoded by a new frame. Ribosomal frameshifting is utilized for the synthesis of additional products, for regulatory purposes and for translational ‘correction’ of problem or ‘savior’ indels. Utilization for synthesis of additional products occurs prominently in the decoding of mobile chromosomal element and viral genomes. One class of regulatory frameshifting of stable chromosomal genes governs cellular polyamine levels from yeasts to humans. In many cases of productively utilized frameshifting, the proportion of ribosomes that frameshift at a shift-prone site is enhanced by specific nascent peptide or mRNA context features. Such mRNA signals, which can be 5′ or 3′ of the shift site or both, can act by pairing with ribosomal RNA or as stem loops or pseudoknots even with one component being 4 kb 3′ from the shift site. Transcriptional realignment at slippage-prone sequences also generates productively utilized products encoded trans-frame with respect to the genomic sequence. This too can be enhanced by nucleic acid structure. Together with dynamic codon redefinition, frameshifting is one of the forms of recoding that enriches gene expression.
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Affiliation(s)
- John F Atkins
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland School of Microbiology, University College Cork, Cork, Ireland Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Gary Loughran
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Pramod R Bhatt
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Andrew E Firth
- Division of Virology, Department of Pathology, University of Cambridge, Hills Road, Cambridge CB2 0QQ, UK
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
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