1
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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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2
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Abstract
Many viruses induce shutoff of host gene expression (host shutoff) as a strategy to take over cellular machinery and evade host immunity. Without host shutoff activity, these viruses generally replicate poorly in vivo, attesting to the importance of this antiviral strategy. In this review, we discuss one particularly advantageous way for viruses to induce host shutoff: triggering widespread host messenger RNA (mRNA) decay. Viruses can trigger increased mRNA destruction either directly, by encoding RNA cleaving or decapping enzymes, or indirectly, by activating cellular RNA degradation pathways. We review what is known about the mechanism of action of several viral RNA degradation factors. We then discuss the consequences of widespread RNA degradation on host gene expression and on the mechanisms of immune evasion, highlighting open questions. Answering these questions is critical to understanding how viral RNA degradation factors regulate host gene expression and how this process helps viruses evade host responses and replicate.
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Affiliation(s)
- Léa Gaucherand
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, and Graduate Program in Molecular Microbiology, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, Massachusetts, USA;
| | - Marta Maria Gaglia
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, and Graduate Program in Molecular Microbiology, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, Massachusetts, USA;
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3
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Al-Rashedi NAM, Munahi MG, AH ALObaidi L. Prediction of potential inhibitors against SARS-CoV-2 endoribonuclease: RNA immunity sensing. J Biomol Struct Dyn 2022; 40:4879-4892. [PMID: 33357040 PMCID: PMC7784835 DOI: 10.1080/07391102.2020.1863265] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 12/07/2020] [Indexed: 02/03/2023]
Abstract
The World Health Organization has classified the COVID-19 outbreak a pandemic which is caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) and declared it a global health emergency. Repurposing drugs with minimum side effects are one approach to quickly respond in attempt to prevent the spread of COVID-19. SARS-CoV-2 encodes several RNA processing enzymes that are unusual and unique for single-stranded RNA viruses, including Nsp15, a hexameric endoribonuclease that discriminatory cleaves immediately 3' of uridines. The structure of SARS-CoV-2 Nsp15 is reported to be homologous to that of the Nsp15 endoribonucleases of SARS-CoV and MERS-CoV, but it exhibits differences that may contribute to the greater virulence of SARS-CoV-2. This study aimed to identify drugs that targeted SARS-COV-2 Nsp15 using a molecular docking-based virtual screening of a library containing 10,000 approved and experimental drugs. The molecular docking results revealed 19 medications that demonstrated a good ability to inhibit Nsp15. Among all the candidated 19 drugs only five FDA approved drugs were used for further investigation by molecular dynamics simulation, the stability of Nsp15-ligand system was evaluated by calculating the RMSD, RMSF, radius of gyration and hydrogen bond profile. Furthermore, MM-PBSA method was employed to validate the binding affinity. According to the obtained results of MD, the complex of Olaparib was showed more stability and lower binding free energy than the control inhibitor during MD simulation time. Finally, we suggest that Olaparib is a potential drug for treating patients infected with SARS-CoV-2 and provide insight into the host immune response to viral RNA.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
| | - Murad G. Munahi
- Department of Chemistry, College of Science, Al-Muthanna University, Samawah, Iraq
| | - Laith AH ALObaidi
- Department of Biology, College of Science, Al-Muthanna University, Samawah, Iraq
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4
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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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5
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Bakre AA, Jones LP, Murray J, Reneer ZB, Meliopoulos VA, Cherry S, Schultz-Cherry S, Tripp RA. Innate Antiviral Cytokine Response to Swine Influenza Virus by Swine Respiratory Epithelial Cells. J Virol 2021; 95:e0069221. [PMID: 33980596 PMCID: PMC8274599 DOI: 10.1128/jvi.00692-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 05/06/2021] [Indexed: 11/20/2022] Open
Abstract
Swine influenza virus (SIV) can cause respiratory illness in swine. Swine contribute to influenza virus reassortment, as avian, human, and/or swine influenza viruses can infect swine and reassort, and new viruses can emerge. Thus, it is important to determine the host antiviral responses that affect SIV replication. In this study, we examined the innate antiviral cytokine response to SIV by swine respiratory epithelial cells, focusing on the expression of interferon (IFN) and interferon-stimulated genes (ISGs). Both primary and transformed swine nasal and tracheal respiratory epithelial cells were examined following infection with field isolates. The results show that IFN and ISG expression is maximal at 12 h postinfection (hpi) and is dependent on cell type and virus genotype. IMPORTANCE Swine are considered intermediate hosts that have facilitated influenza virus reassortment events that have given rise pandemics or genetically related viruses have become established in swine. In this study, we examine the innate antiviral response to swine influenza virus in primary and immortalized swine nasal and tracheal epithelial cells, and show virus strain- and host cell type-dependent differential expression of key interferons and interferon-stimulated genes.
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Affiliation(s)
- Abhijeet A Bakre
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Les P Jones
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Jackelyn Murray
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Z Beau Reneer
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Victoria A Meliopoulos
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis Tennessee
| | - Sean Cherry
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis Tennessee
| | - Stacey Schultz-Cherry
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis Tennessee
| | - Ralph A Tripp
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
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6
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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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7
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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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8
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Kong M, Chen K, Zeng Z, Wang X, Gu M, Hu Z, Jiao X, Hu J, Liu X. The virulence modulator PA-X protein has minor effect on the pathogenicity of the highly pathogenic H7N9 avian influenza virus in mice. Vet Microbiol 2021; 255:109019. [PMID: 33676094 DOI: 10.1016/j.vetmic.2021.109019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 02/16/2021] [Indexed: 12/27/2022]
Abstract
PA-X is a novel discovered accessory protein encoded by the PA mRNA of the influenza A virus. Accumulated studies have demonstrated the crucial role of this protein in regulating the virulence of various subtypes of influenza virus, including H1N1, H5N1, H9N2, H1N2, H3N8 and H3N2 virus. However, the role of PA-X protein in regulating the virulence of the highly pathogenic avian H7N9 virus was unknown. In this study, we firstly generated two recombinant H7N9 viruses which have lower PA-X expression level than the parental H7N9 virus. We then systematically compared their difference in virus replication, polymerase activity, virulence and virus-induced host immune responses in mice. The results showed that the PA-X deficient viruses significantly increased viral replication in madin darby canine kidney cells and slightly increased viral replication in mouse lung. In addition, loss of PA-X expression significantly increased viral polymerase activity and alleviated the host-shutoff activity mediated by the parental PA protein. However, in contrast with the usual function of PA-X in regulating the virulence in different subtype influenza virus, no obvious effect on viral virulence in mice was observed by H7N9 PA-X protein. Furthermore, among the 12 kinds of cytokines and 2 kinds of complement derived components that we tested, the PA-X deficiency viruses only induced significantly higher expression levels of MX1 than the parental virus. Altogether, these results showed that PA-X has little effect on viral virulence and viral induced innate immune response of the H7N9 subtype virus. Our study adds further information for the growing understanding of the complexity of PA-X in regulating viral virulence and host innate immune response of different influenza virus.
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Affiliation(s)
- Ming Kong
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Kaibiao Chen
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Zixiong Zeng
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Xiaoquan Wang
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Min Gu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Zenglei Hu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Xinan Jiao
- Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China
| | - Jiao Hu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China.
| | - Xiufan Liu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China.
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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: 17] [Impact Index Per Article: 4.3] [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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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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11
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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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Narkpuk J, Jongkaewwattana A, Teeravechyan S. The avian influenza virus PA segment mediates strain-specific antagonism of BST-2/tetherin. Virology 2018; 525:161-169. [PMID: 30290311 PMCID: PMC7172379 DOI: 10.1016/j.virol.2018.09.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 09/19/2018] [Accepted: 09/21/2018] [Indexed: 12/26/2022]
Abstract
BST-2 is an antiviral protein described as a powerful cross-species transmission barrier for simian immunodeficiency viruses. Influenza viruses appear to interact with BST-2, raising the possibility that BST-2 may be a barrier for cross-species transmission. An MDCK-based cell line expressing human BST-2 was generated to study human-derived A/Puerto Rico/8/36 (H1N1; PR8) as well as two low pathogenic avian influenza viruses (subtypes H4N6 and H6N1). The H4N6 and H6N1 viruses were less affected by BST-2 expression than PR8, due to their ability to decrease BST-2 levels, a function localized to the PA segment of both avian viruses. Experiments with PA-mutant and -chimeric viruses confirmed that the avian PA segment conferred BST-2 downregulation and antagonism. These results indicate a species-specific ability of PA from low pathogenic avian viruses to mitigate human BST-2 antiviral activity, suggesting that BST-2 is unlikely to be a general cross-species barrier to transmission of such viruses to humans.
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Affiliation(s)
- Jaraspim Narkpuk
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand
| | - Anan Jongkaewwattana
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand
| | - Samaporn Teeravechyan
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
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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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Hu J, Ma C, Liu X. PA-X: a key regulator of influenza A virus pathogenicity and host immune responses. Med Microbiol Immunol 2018; 207:255-269. [PMID: 29974232 PMCID: PMC7086933 DOI: 10.1007/s00430-018-0548-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 06/28/2018] [Indexed: 02/07/2023]
Abstract
PA-X, a fusion protein belonging to influenza A viruses (IAVs), integrating the N-terminal 191 amino acids of PA gene and the ribosomal frame-shifting product that lengthens out to 41 or 61 amino acids. Since its discovery in 2012, multiple functions have been attributed to this small protein, including a process, where wide-spread protein synthesis in infected host cells is shut down (called host shutoff), and viral replication, polymerase activity, viral-induced cell apoptosis, PA nuclear localization, and virulence are modulated. However, many of its proposed functions may be specific to strain, subtype, host, or cell line. In this review, we start by describing the well-defined global host-shutoff ability of PA-X and the potential mechanisms underlying it. We move on to the role played by PA-X in modulating innate and acquired immune responses in the host. We then systematically discuss the role played by PA-X in modulating the virulence of influenza viruses of different subtypes and host origins, and finish with a general overview of the research advances made in identifying the host cell partners that interact with PA-X. To uncover possible clues about the differential effects of PA-X in modulating viral virulence, we focus on systemically evaluating polymorphisms in PA-X from various viral subtypes and hosts, including avian and human H5N1, H5N6, H9N2, and H7N9 viruses. Finally, we conclude with a proposition regarding the possible future research directions for this important protein.
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Affiliation(s)
- Jiao Hu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, 48 East Wenhui Road, Yangzhou, 225009, Jiangsu Province, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Chunxi Ma
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, 48 East Wenhui Road, Yangzhou, 225009, Jiangsu Province, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Xiufan Liu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, 48 East Wenhui Road, Yangzhou, 225009, Jiangsu Province, China.
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China.
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China.
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