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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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Rigby CV, Sabsay KR, Bisht K, Eggink D, Jalal H, te Velthuis AJW. Evolution of transient RNA structure-RNA polymerase interactions in respiratory RNA virus genomes. Virus Evol 2023; 9:vead056. [PMID: 37692892 PMCID: PMC10492445 DOI: 10.1093/ve/vead056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 08/02/2023] [Accepted: 08/24/2023] [Indexed: 09/12/2023] Open
Abstract
RNA viruses are important human pathogens that cause seasonal epidemics and occasional pandemics. Examples are influenza A viruses (IAV) and coronaviruses (CoV). When emerging IAV and CoV spill over to humans, they adapt to evade immune responses and optimize their replication and spread in human cells. In IAV, adaptation occurs in all viral proteins, including the viral ribonucleoprotein (RNP) complex. RNPs consist of a copy of the viral RNA polymerase, a double-helical coil of nucleoprotein, and one of the eight segments of the IAV RNA genome. The RNA segments and their transcripts are partially structured to coordinate the packaging of the viral genome and modulate viral mRNA translation. In addition, RNA structures can affect the efficiency of viral RNA synthesis and the activation of host innate immune response. Here, we investigated if RNA structures that modulate IAV replication processivity, so-called template loops (t-loops), vary during the adaptation of pandemic and emerging IAV to humans. Using cell culture-based replication assays and in silico sequence analyses, we find that the sensitivity of the IAV H3N2 RNA polymerase to t-loops increased between isolates from 1968 and 2017, whereas the total free energy of t-loops in the IAV H3N2 genome was reduced. This reduction is particularly prominent in the PB1 gene. In H1N1 IAV, we find two separate reductions in t-loop free energy, one following the 1918 pandemic and one following the 2009 pandemic. No destabilization of t-loops is observed in the influenza B virus genome, whereas analysis of SARS-CoV-2 isolates reveals destabilization of viral RNA structures. Overall, we propose that a loss of free energy in the RNA genome of emerging respiratory RNA viruses may contribute to the adaption of these viruses to the human population.
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Affiliation(s)
- Charlotte V Rigby
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
- Department of Pathology, Addenbrooke’s Hospital, University of Cambridge, Hills Road, Cambridge CB2 2QQ, UK
- Addenbrooke’s Hospital, Public Health England, Hills Road, Cambridge CB2 2QQ, UK
| | - Kimberly R Sabsay
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
- Carl Icahn Laboratory, Lewis-Sigler Institute, Princeton University, South Drive, Princeton, NJ 08544, USA
| | - Karishma Bisht
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Dirk Eggink
- Department of Medical Microbiology, Amsterdam UMC, Meibergdreef 9, Amsterdam 1105 AZ, The Netherlands
| | - Hamid Jalal
- Addenbrooke’s Hospital, Public Health England, Hills Road, Cambridge CB2 2QQ, UK
| | - Aartjan J W te Velthuis
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
- Center for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9, Bilthoven 3721 MA, the Netherlands
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3
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Rigby C, Sabsay K, Bisht K, Eggink D, Jalal H, te Velthuis AJ. Evolution of transient RNA structure-RNA polymerase interactions in respiratory RNA virus genomes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.25.542331. [PMID: 37292879 PMCID: PMC10245964 DOI: 10.1101/2023.05.25.542331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
RNA viruses are important human pathogens that cause seasonal epidemics and occasional pandemics. Examples are influenza A viruses (IAV) and coronaviruses (CoV). When emerging IAV and CoV spill over to humans, they adapt to evade immune responses and optimize their replication and spread in human cells. In IAV, adaptation occurs in all viral proteins, including the viral ribonucleoprotein (RNP) complex. RNPs consists of a copy of the viral RNA polymerase, a double-helical coil of nucleoprotein, and one of the eight segments of the IAV RNA genome. The RNA segments and their transcripts are partially structured to coordinate the packaging of the viral genome and modulate viral mRNA translation. In addition, RNA structures can affect the efficiency of viral RNA synthesis and the activation of host innate immune response. Here, we investigated if RNA structures that modulate IAV replication processivity, so called template loops (t-loops), vary during the adaptation of pandemic and emerging IAV to humans. Using cell culture-based replication assays and in silico sequence analyses, we find that the sensitivity of the IAV H3N2 RNA polymerase to t-loops increased between isolates from 1968 and 2017, whereas the total free energy of t-loops in the IAV H3N2 genome was reduced. This reduction is particularly prominent in the PB1 gene. In H1N1 IAV, we find two separate reductions in t-loop free energy, one following the 1918 pandemic and one following the 2009 pandemic. No destabilization of t-loops is observed in the IBV genome, whereas analysis of SARS-CoV-2 isolates reveals destabilization of viral RNA structures. Overall, we propose that a loss of free energy in the RNA genome of emerging respiratory RNA viruses may contribute to the adaption of these viruses to the human population.
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Affiliation(s)
- Charlotte Rigby
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, 08544 New Jersey, United States
- University of Cambridge, Department of Pathology, Addenbrooke’s Hospital, Cambridge CB2 2QQ, United Kingdom
- Public Health England, Addenbrooke’s Hospital, Cambridge CB2 2QQ, United Kingdom
| | - Kimberly Sabsay
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, 08544 New Jersey, United States
- Sigler Institute, Princeton University, Princeton, NJ 08544, United States
| | - Karishma Bisht
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, 08544 New Jersey, United States
| | - Dirk Eggink
- Department of Medical Microbiology, Amsterdam UMC, Amsterdam, The Netherlands
- Center for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | - Hamid Jalal
- Public Health England, Addenbrooke’s Hospital, Cambridge CB2 2QQ, United Kingdom
| | - Aartjan J.W. te Velthuis
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, 08544 New Jersey, United States
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4
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Gunnarsson PA, Babu MM. Predicting evolutionary outcomes through the probability of accessing sequence variants. SCIENCE ADVANCES 2023; 9:eade2903. [PMID: 37506212 PMCID: PMC10381947 DOI: 10.1126/sciadv.ade2903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 06/27/2023] [Indexed: 07/30/2023]
Abstract
Natural selection can only operate on available genetic variation. Thus, determining the probability of accessing different sequence variants from a starting sequence can help predict evolutionary trajectories and outcomes. We define the concept of "variant accessibility" as the probability that a set of genotypes encoding a particular protein function will arise through mutations before subject to natural selection. This probability is shaped by the mutational biases of nucleotides and the structure of the genetic code. Using the influenza A virus as a model, we discuss how a more accessible but less fit variant can emerge as an adaptation rather than a more fit variant. We describe a genotype-accessibility landscape, complementary to the genotype-fitness landscape, that informs the likelihood of a starting sequence reaching different parts of genotype space. The proposed framework lays the foundation for predicting the emergence of adaptive genotypes in evolving systems such as viruses and tumors.
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Affiliation(s)
- P. Alexander Gunnarsson
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
- Department of Structural Biology and Center of Excellence for Data-Driven Discovery, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - M. Madan Babu
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
- Department of Structural Biology and Center of Excellence for Data-Driven Discovery, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
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5
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Chung YT, Kuan CY, Liao GR, Albrecht RA, Tseng YY, Hsu YC, Ou SC, Hsu WL. A variant NS1 protein from H5N2 avian influenza virus suppresses PKR activation and promotes replication and virulence in mammals. Emerg Microbes Infect 2022; 11:2291-2303. [PMID: 35979918 PMCID: PMC9559317 DOI: 10.1080/22221751.2022.2114853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Highly pathogenic avian influenza viruses (HPAIVs) frequently receive global attention as threats to public health. The NS1 protein is a key virulence factor known to impair host antiviral responses. The study herein revealed HPAIV H5N2 NS gene encoded additional protein; a truncated NS1 variant, designated NS3, produced by alternative splicing of the NS transcript. To examine the function of NS3 during infection, we generated recombinant viruses expressing either full-length NS1 (RG-AIV-T375G) or NS3 (RG-AIV-NS3). Interestingly, RG-AIV-NS3 virus produced higher titres than RG-AIV-T375G in multiple mammalian cell lines. However, RG-AIV-T375G exhibited a replication advantage over RG-AIV-NS3 in chicken DF-1 cells, indicating that host cell identity dictates the effect of NS3 on viral replication. In mice and mammalian cells, RG-AIV-NS3 infection elicited higher level of cytokines, including IFN-β, MX and TNF-α, potentially due to its higher replication activity. Based on mini-genome assay, NS3 had pronounced effects on viral replication machinery. Surprisingly, NS3 retained an interaction with PKR and suppressed PKR activation despite its lack of amino-acid residues 126-167. The poor replication ability of RG-AIV-T375G was partially restored in cells deficient in PKR suggesting that full-length NS1 may be insufficient to suppress PKR function. Notably, virulence of the full-length NS1-expressing RG-AIV-T375G virus was highly attenuated in mice when compared to RG-AIV-NS3. In summary, our study reveals the existence and function of a previously unidentified H5N2 viral protein, NS3. We found that NS3 is functionally distinct from NS1 protein, as it enhances viral replication and pathogenicity in mammalian systems, potentially via suppression of PKR activity.
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Affiliation(s)
- Yun-Ting Chung
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung, Taiwan
| | - Chih-Ying Kuan
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung, Taiwan
| | - Guan-Ru Liao
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung, Taiwan
| | - Randy A Albrecht
- Department of Microbiology, Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Yeu-Yang Tseng
- WHO Collaborating Centre for Reference and Research on Influenza, VIDRL, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Victoria, Australia
| | - Yu-Chen Hsu
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung, Taiwan
| | - Shan-Chia Ou
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung, Taiwan
| | - Wei-Li Hsu
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung, Taiwan
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Ishida H, Murakami S, Kamiki H, Matsugo H, Katayama M, Sekine W, Ohira K, Takenaka-Uema A, Horimoto T. Construction of an Influenza D Virus with an Eight-Segmented Genome. Viruses 2021; 13:v13112166. [PMID: 34834971 PMCID: PMC8619389 DOI: 10.3390/v13112166] [Citation(s) in RCA: 1] [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: 09/29/2021] [Revised: 10/22/2021] [Accepted: 10/25/2021] [Indexed: 11/16/2022] Open
Abstract
Influenza D virus (IDV) may cause the bovine respiratory disease complex, which is the most common and costly disease affecting the cattle industry. Previously, we revealed that eight segments could be actively packaged in its single virion, suggesting that IDV with the seven-segmented genome shows an agnostic genome packaging mechanism. Herein, we engineered an eight-segmented recombinant IDV in which the NS1 or NS2 genes were separated from NS segment into independent segments (NS1 or NS2 segments, respectively), leading to monocistronic translation of each NS protein. We constructed two plasmids: one for the viral RNA (vRNA)-synthesis of the NS1 segment with a silent mutation at the splicing acceptor site, which controls NS2 transcription in the NS segment; and another for the RNA synthesis of the NS2 segment, with deletion of the intron in the NS segment. These plasmids and six other vRNA-synthesis plasmids were used to fabricate an infectious eight-segmented IDV via reverse genetics. This system enables analysis of the functions of NS1 or NS2. We tested the requirement of the N-terminal overlapping region (NOR) in these proteins for viral infectivity. We rescued a virus with NOR-deleted NS2 protein, which displayed a growth rate equivalent to that of the eight-segmented virus with intact NS2. Thus, the NOR may not influence viral growth. In contrast, a virus with NOR-deleted NS1 protein could not be rescued. These results indicate that the eight-segmented rescue system of IDV may provide an alternative method to analyze viral proteins at the molecular level.
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7
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Differential Modulation of Innate Immune Responses in Human Primary Cells by Influenza A Viruses Carrying Human or Avian Nonstructural Protein 1. J Virol 2019; 94:JVI.00999-19. [PMID: 31597767 PMCID: PMC6912104 DOI: 10.1128/jvi.00999-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 09/29/2019] [Indexed: 12/22/2022] Open
Abstract
Influenza A viruses (IAVs) cause seasonal epidemics which result in an important health and economic burden. Wild aquatic birds are the natural host of IAV. However, IAV can infect diverse hosts, including humans, domestic poultry, pigs, and others. IAVs circulating in animals occasionally cross the species barrier, infecting humans, which results in mild to very severe disease. In some cases, these viruses can acquire the ability to be transmitted among humans and initiate a pandemic. The nonstructural 1 (NS1) protein of IAV is an important antagonist of the innate immune response. In this study, using recombinant viruses and primary human cells, we show that NS1 proteins from human and avian hosts show intrinsic differences in the modulation of the innate immunity in human dendritic cells and epithelial cells, as well as different cellular localization dynamics in infected cells. The influenza A virus (IAV) nonstructural protein 1 (NS1) contributes to disease pathogenesis through the inhibition of host innate immune responses. Dendritic cells (DCs) release interferons (IFNs) and proinflammatory cytokines and promote adaptive immunity upon viral infection. In order to characterize the strain-specific effects of IAV NS1 on human DC activation, we infected human DCs with a panel of recombinant viruses with the same backbone (A/Puerto Rico/08/1934) expressing different NS1 proteins from human and avian origin. We found that these viruses induced a clearly distinct phenotype in DCs. Specifically, viruses expressing NS1 from human IAV (either H1N1 or H3N2) induced higher levels of expression of type I (IFN-α and IFN-β) and type III (IFN-λ1 to IFNλ3) IFNs than viruses expressing avian IAV NS1 proteins (H5N1, H7N9, and H7N2), but the differences observed in the expression levels of proinflammatory cytokines like tumor necrosis factor alpha (TNF-α) or interleukin-6 (IL-6) were not significant. In addition, using imaging flow cytometry, we found that human and avian NS1 proteins segregate based on their subcellular trafficking dynamics, which might be associated with the different innate immune profile induced in DCs by viruses expressing those NS1 proteins. Innate immune responses induced by our panel of IAV recombinant viruses were also characterized in normal human bronchial epithelial cells, and the results were consistent with those in DCs. Altogether, our results reveal an increased ability of NS1 from avian viruses to antagonize innate immune responses in human primary cells compared to the ability of NS1 from human viruses, which could contribute to the severe disease induced by avian IAV in humans. IMPORTANCE Influenza A viruses (IAVs) cause seasonal epidemics which result in an important health and economic burden. Wild aquatic birds are the natural host of IAV. However, IAV can infect diverse hosts, including humans, domestic poultry, pigs, and others. IAVs circulating in animals occasionally cross the species barrier, infecting humans, which results in mild to very severe disease. In some cases, these viruses can acquire the ability to be transmitted among humans and initiate a pandemic. The nonstructural 1 (NS1) protein of IAV is an important antagonist of the innate immune response. In this study, using recombinant viruses and primary human cells, we show that NS1 proteins from human and avian hosts show intrinsic differences in the modulation of the innate immunity in human dendritic cells and epithelial cells, as well as different cellular localization dynamics in infected cells.
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8
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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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9
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Kleinpeter AB, Jureka AS, Falahat SM, Green TJ, Petit CM. Structural analyses reveal the mechanism of inhibition of influenza virus NS1 by two antiviral compounds. J Biol Chem 2018; 293:14659-14668. [PMID: 30076219 DOI: 10.1074/jbc.ra118.004012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 08/03/2018] [Indexed: 11/06/2022] Open
Abstract
The influenza virus is a significant public health concern causing 250,000-500,000 deaths worldwide each year. Its ability to change quickly results in the potential for rapid generation of pandemic strains for which most individuals would have no antibody protection. This pandemic potential highlights the need for the continuous development of new drugs against influenza virus. As an essential component and well established virulence determinant, NS1 (nonstructural protein 1) of influenza virus is a highly prioritized target for the development of anti-influenza compounds. Here, we used NMR to determine that the NS1 effector domain (NS1ED) derived from the A/Brevig Mission/1/1918 (H1N1) strain of influenza (1918H1N1) binds to two previously described anti-influenza compounds A9 (JJ3297) and A22. We then used X-ray crystallography to determine the three-dimensional structure of the 1918H1N1 NS1ED Furthermore, we mapped the A9/A22-binding site onto our 1918H1N1 NS1ED structure and determined that A9 and A22 interact with the NS1ED in the hydrophobic pocket known to facilitate binding to the 30-kDa subunit of the cleavage and polyadenylation specificity factor (CPSF30), suggesting that the two compounds likely attenuate influenza replication by inhibiting the NS1ED-CPSF30 interaction. Finally, our structure revealed that NS1ED could dimerize via an interface that we termed the α3-α3 dimer. Taken together, the findings presented here provide strong evidence for the mechanism of action of two anti-influenza compounds that target NS1 and contribute significant structural insights into NS1 that we hope will promote and inform the development and optimization of influenza therapies based on A9/A22.
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Affiliation(s)
| | | | - Sally M Falahat
- From the Departments of Biochemistry and Molecular Genetics and
| | - Todd J Green
- Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Chad M Petit
- From the Departments of Biochemistry and Molecular Genetics and
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10
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Structure-Guided Functional Annotation of the Influenza A Virus NS1 Protein Reveals Dynamic Evolution of the p85β-Binding Site during Circulation in Humans. J Virol 2017; 91:JVI.01081-17. [PMID: 28814525 PMCID: PMC5640874 DOI: 10.1128/jvi.01081-17] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 08/13/2017] [Indexed: 01/28/2023] Open
Abstract
Rational characterization of virulence and host-adaptive markers in the multifunctional influenza A virus NS1 protein is hindered by a lack of comprehensive knowledge about NS1-host protein protein interfaces. Here, we surveyed the impact of amino acid variation in NS1 at its structurally defined binding site for host p85β, a regulator of phosphoinositide 3-kinase (PI3K) signaling. Structure-guided alanine scanning of all viral residues at this interface defined 10 positions contributing to the interaction, with residues 89, 95, 98, 133, 145, and 162 being the most important. A bioinformatic study of >24,000 publicly available NS1 sequences derived from viruses infecting different hosts highlighted several prevalent amino acid variants at the p85β interface that either enhanced (I95) or weakened (N135, T145, L161, Y161, S164) p85β binding. Interestingly, analysis of viruses circulating in humans since the 1918 pandemic revealed the temporal acquisition of functionally relevant variants at this interface. I95 (which enhanced p85β binding) quickly became prevalent in the 1940s and experimentally conferred a fitness advantage to a recombinant 1930s-based H1N1 virus in human lung epithelial cells. Surprisingly, H1N1 and H3N2 viruses recently acquired T145 or N135, respectively, which diminished p85β binding but apparently not the overall fitness in the human population. Evolutionary analyses revealed covariation of the NS1-p85β binding phenotype in humans with functional changes at multiple residues in other viral proteins, suggesting an unexplored compensatory or synergistic interplay between phenotypes in vivo. Overall, our data provide a resource to understand the consequences of the NS1-p85β binding spectrum of different influenza viruses and highlight the dynamic evolution of this property in viruses circulating in humans. IMPORTANCE In humans, influenza A viruses are responsible for causing seasonal epidemics and occasional pandemics. These viruses also circulate and evolve in other animal species, creating a reservoir from which novel viruses with distinct properties can emerge. The viral nonstructural protein NS1 is an important host range determinant and virulence factor that exhibits strain-specific interactions with several host factors, although few have been characterized extensively. In the study described here, we comprehensively surveyed the impact of natural and unnatural NS1 variations on the binding of NS1 to host p85β, a subunit of phosphoinositide 3-kinase that regulates intracellular metabolism and contributes to virus replication and virulence. We define the p85β-binding site on NS1 and provide a predictive resource to assess this ability of NS1 in viruses from different hosts. Strikingly, we uncover a spectrum of p85β binding by different NS1 proteins and reveal that viruses evolving in humans have undergone dynamic changes in this NS1 function over the last century.
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11
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Reintroduction of highly pathogenic avian influenza A/H5N8 virus of clade 2.3.4.4. in Russia. Arch Virol 2017; 162:1381-1385. [DOI: 10.1007/s00705-017-3246-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 01/09/2017] [Indexed: 01/13/2023]
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12
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Ylösmäki L, Fagerlund R, Kuisma I, Julkunen I, Saksela K. Nuclear Translocation of Crk Adaptor Proteins by the Influenza A Virus NS1 Protein. Viruses 2016; 8:101. [PMID: 27092521 PMCID: PMC4848595 DOI: 10.3390/v8040101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 03/31/2016] [Accepted: 04/04/2016] [Indexed: 12/18/2022] Open
Abstract
The non-structural protein-1 (NS1) of many influenza A strains, especially those of avian origin, contains an SH3 ligand motif, which binds tightly to the cellular adaptor proteins Crk (Chicken tumor virus number 10 (CT10) regulator of kinase) and Crk-like adapter protein (CrkL). This interaction has been shown to potentiate NS1-induced activation of the phosphatidylinositol 3-kinase (PI3K), but additional effects on the host cell physiology may exist. Here we show that NS1 can induce an efficient translocation of Crk proteins from the cytoplasm into the nucleus, which results in an altered pattern of nuclear protein tyrosine phosphorylation. This was not observed using NS1 proteins deficient in SH3 binding or engineered to be exclusively cytoplasmic, indicating a physical role for NS1 as a carrier in the nuclear translocation of Crk. These data further emphasize the role of Crk proteins as host cell interaction partners of NS1, and highlight the potential for host cell manipulation gained by a viral protein simply via acquiring a short SH3 binding motif.
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Affiliation(s)
- Leena Ylösmäki
- Department of Virology, University of Helsinki and Helsinki University Hospital, 00014 Helsinki, Finland.
| | - Riku Fagerlund
- Department of Virology, University of Helsinki and Helsinki University Hospital, 00014 Helsinki, Finland.
| | - Inka Kuisma
- Department of Virology, University of Helsinki and Helsinki University Hospital, 00014 Helsinki, Finland.
| | - Ilkka Julkunen
- Department of Virology, University of Turku, 20520 Turku, Finland and Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), 00300 Helsinki, Finland.
| | - Kalle Saksela
- Department of Virology, University of Helsinki and Helsinki University Hospital, 00014 Helsinki, Finland.
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Belanov SS, Bychkov D, Benner C, Ripatti S, Ojala T, Kankainen M, Kai Lee H, Wei-Tze Tang J, Kainov DE. Genome-Wide Analysis of Evolutionary Markers of Human Influenza A(H1N1)pdm09 and A(H3N2) Viruses May Guide Selection of Vaccine Strain Candidates. Genome Biol Evol 2015; 7:3472-83. [PMID: 26615216 PMCID: PMC4700966 DOI: 10.1093/gbe/evv240] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Here we analyzed whole-genome sequences of 3,969 influenza A(H1N1)pdm09 and 4,774 A(H3N2) strains that circulated during 2009–2015 in the world. The analysis revealed changes at 481 and 533 amino acid sites in proteins of influenza A(H1N1)pdm09 and A(H3N2) strains, respectively. Many of these changes were introduced as a result of random drift. However, there were 61 and 68 changes that were present in relatively large number of A(H1N1)pdm09 and A(H3N2) strains, respectively, that circulated during relatively long time. We named these amino acid substitutions evolutionary markers, as they seemed to contain valuable information regarding the viral evolution. Interestingly, influenza A(H1N1)pdm09 and A(H3N2) viruses acquired non-overlapping sets of evolutionary markers. We next analyzed these characteristic markers in vaccine strains recommended by the World Health Organization for the past five years. Our analysis revealed that vaccine strains carried only few evolutionary markers at antigenic sites of viral hemagglutinin (HA) and neuraminidase (NA). The absence of these markers at antigenic sites could affect the recognition of HA and NA by human antibodies generated in response to vaccinations. This could, in part, explain moderate efficacy of influenza vaccines during 2009–2014. Finally, we identified influenza A(H1N1)pdm09 and A(H3N2) strains, which contain all the evolutionary markers of influenza A strains circulated in 2015, and which could be used as vaccine candidates for the 2015/2016 season. Thus, genome-wide analysis of evolutionary markers of influenza A(H1N1)pdm09 and A(H3N2) viruses may guide selection of vaccine strain candidates.
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Affiliation(s)
- Sergei S Belanov
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Dmitrii Bychkov
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Christian Benner
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Samuli Ripatti
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland Department of Public Health, Hjelt Institute, University of Helsinki, Helsinki, Finland Welcome Trust Sanger Institute, Cambridgeshire, United Kingdom
| | - Teija Ojala
- Institute of Biomedicine, Pharmacology, University of Helsinki, Helsinki, Finland
| | - Matti Kankainen
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Hong Kai Lee
- Department of Laboratory Medicine, National University Hospital, National University Health System, Singapore
| | - Julian Wei-Tze Tang
- Clinical Microbiology, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom
| | - Denis E Kainov
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
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Marc D. Influenza virus non-structural protein NS1: interferon antagonism and beyond. J Gen Virol 2014; 95:2594-2611. [PMID: 25182164 DOI: 10.1099/vir.0.069542-0] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Most viruses express one or several proteins that counter the antiviral defences of the host cell. This is the task of non-structural protein NS1 in influenza viruses. Absent in the viral particle, but highly expressed in the infected cell, NS1 dramatically inhibits cellular gene expression and prevents the activation of key players in the IFN system. In addition, NS1 selectively enhances the translation of viral mRNAs and may regulate the synthesis of viral RNAs. Our knowledge of the virus and of NS1 has increased dramatically during the last 15 years. The atomic structure of NS1 has been determined, many cellular partners have been identified and its multiple activities have been studied in depth. This review presents our current knowledge, and attempts to establish relationships between the RNA sequence, the structure of the protein, its ligands, its activities and the pathogenicity of the virus. A better understanding of NS1 could help in elaborating novel antiviral strategies, based on either live vaccines with altered NS1 or on small-compound inhibitors of NS1.
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Affiliation(s)
- Daniel Marc
- Université François Rabelais, UMR1282 Infectiologie et Santé Publique, 37000 Tours, France.,Pathologie et Immunologie Aviaire, INRA, UMR1282 Infectiologie et Santé Publique, 37380 Nouzilly, France
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15
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Tanner LB, Chng C, Guan XL, Lei Z, Rozen SG, Wenk MR. Lipidomics identifies a requirement for peroxisomal function during influenza virus replication. J Lipid Res 2014; 55:1357-65. [PMID: 24868094 DOI: 10.1194/jlr.m049148] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Indexed: 12/13/2022] Open
Abstract
Influenza virus acquires a host-derived lipid envelope during budding, yet a convergent view on the role of host lipid metabolism during infection is lacking. Using a mass spectrometry-based lipidomics approach, we provide a systems-scale perspective on membrane lipid dynamics of infected human lung epithelial cells and purified influenza virions. We reveal enrichment of the minor peroxisome-derived ether-linked phosphatidylcholines relative to bulk ester-linked phosphatidylcholines in virions as a unique pathogenicity-dependent signature for influenza not found in other enveloped viruses. Strikingly, pharmacological and genetic interference with peroxisomal and ether lipid metabolism impaired influenza virus production. Further integration of our lipidomics results with published genomics and proteomics data corroborated altered peroxisomal lipid metabolism as a hallmark of influenza virus infection in vitro and in vivo. Influenza virus may therefore tailor peroxisomal and particularly ether lipid metabolism for efficient replication.
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Affiliation(s)
- Lukas Bahati Tanner
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117456 NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, Singapore 117456
| | - Charmaine Chng
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117456
| | - Xue Li Guan
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117456 Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, 4002 Basel, Switzerland
| | - Zhengdeng Lei
- Centre for Computational Biology, Duke-NUS Graduate Medical School, Singapore 169857 Stem Cell Biology Program, Duke-NUS Graduate Medical School, Singapore 169857 Research Resources Center, University of Illinois at Chicago, Chicago, IL 60612
| | - Steven G Rozen
- Centre for Computational Biology, Duke-NUS Graduate Medical School, Singapore 169857 Stem Cell Biology Program, Duke-NUS Graduate Medical School, Singapore 169857
| | - Markus R Wenk
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117456 NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, Singapore 117456 Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, 4002 Basel, Switzerland Department of Biological Sciences, National University of Singapore, Singapore 117597
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Lalime EN, Pekosz A. The R35 residue of the influenza A virus NS1 protein has minimal effects on nuclear localization but alters virus replication through disrupting protein dimerization. Virology 2014; 458-459:33-42. [PMID: 24928037 DOI: 10.1016/j.virol.2014.04.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 04/05/2014] [Accepted: 04/09/2014] [Indexed: 10/25/2022]
Abstract
The influenza A virus NS1 protein has a nuclear localization sequence (NLS) in the amino terminal region. This NLS overlaps sequences that are important for RNA binding as well as protein dimerization. To assess the significance of the NS1 NLS on influenza virus replication, the NLS amino acids were individually mutated to alanines and recombinant viruses encoding these mutations were rescued. Viruses containing NS1 proteins with mutations at R37, R38 and K41 displayed minimal changes in replication or NS1 protein nuclear localization. Recombinant viruses encoding NS1 R35A were not recovered but viruses containing second site mutations at position D39 in addition to the R35A mutation were isolated. The mutations at position 39 were shown to partially restore NS1 protein dimerization but had minimal effects on nuclear localization. These data indicate that the amino acids in the NS1 NLS region play a more important role in protein dimerization compared to nuclear localization.
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Affiliation(s)
- Erin N Lalime
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Suite E5132, Baltimore, MD 21205-2103, USA
| | - Andrew Pekosz
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Suite E5132, Baltimore, MD 21205-2103, USA.
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