1
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Vlasenok M, Margasyuk S, Pervouchine DD. Transcriptome sequencing suggests that pre-mRNA splicing counteracts widespread intronic cleavage and polyadenylation. NAR Genom Bioinform 2023; 5:lqad051. [PMID: 37260513 PMCID: PMC10227441 DOI: 10.1093/nargab/lqad051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 05/09/2023] [Accepted: 05/17/2023] [Indexed: 06/02/2023] Open
Abstract
Alternative splicing (AS) and alternative polyadenylation (APA) are two crucial steps in the post-transcriptional regulation of eukaryotic gene expression. Protocols capturing and sequencing RNA 3'-ends have uncovered widespread intronic polyadenylation (IPA) in normal and disease conditions, where it is currently attributed to stochastic variations in the pre-mRNA processing. Here, we took advantage of the massive amount of RNA-seq data generated by the Genotype Tissue Expression project (GTEx) to simultaneously identify and match tissue-specific expression of intronic polyadenylation sites with tissue-specific splicing. A combination of computational methods including the analysis of short reads with non-templated adenines revealed that APA events are more abundant in introns than in exons. While the rate of IPA in composite terminal exons and skipped terminal exons expectedly correlates with splicing, we observed a considerable fraction of IPA events that lack AS support and attributed them to spliced polyadenylated introns (SPI). We hypothesize that SPIs represent transient byproducts of a dynamic coupling between APA and AS, in which the spliceosome removes the intron while it is being cleaved and polyadenylated. These findings indicate that cotranscriptional pre-mRNA splicing could serve as a rescue mechanism to suppress premature transcription termination at intronic polyadenylation sites.
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Affiliation(s)
- Maria Vlasenok
- Center for Molecular and Cellular Biology, Skolkovo Institute of Science and Technology, Bolshoy Bulvar 30, Moscow 121205, Russia
| | - Sergey Margasyuk
- Center for Molecular and Cellular Biology, Skolkovo Institute of Science and Technology, Bolshoy Bulvar 30, Moscow 121205, Russia
| | - Dmitri D Pervouchine
- Center for Molecular and Cellular Biology, Skolkovo Institute of Science and Technology, Bolshoy Bulvar 30, Moscow 121205, Russia
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2
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Evseev D, Magor KE. Molecular Evolution of the Influenza A Virus Non-structural Protein 1 in Interspecies Transmission and Adaptation. Front Microbiol 2021; 12:693204. [PMID: 34671321 PMCID: PMC8521145 DOI: 10.3389/fmicb.2021.693204] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 09/06/2021] [Indexed: 12/03/2022] Open
Abstract
The non-structural protein 1 (NS1) of influenza A viruses plays important roles in viral fitness and in the process of interspecies adaptation. It is one of the most polymorphic and mutation-tolerant proteins of the influenza A genome, but its evolutionary patterns in different host species and the selective pressures that underlie them are hard to define. In this review, we highlight some of the species-specific molecular signatures apparent in different NS1 proteins and discuss two functions of NS1 in the process of viral adaptation to new host species. First, we consider the ability of NS1 proteins to broadly suppress host protein expression through interaction with CPSF4. This NS1 function can be spontaneously lost and regained through mutation and must be balanced against the need for host co-factors to aid efficient viral replication. Evidence suggests that this function of NS1 may be selectively lost in the initial stages of viral adaptation to some new host species. Second, we explore the ability of NS1 proteins to inhibit antiviral interferon signaling, an essential function for viral replication without which the virus is severely attenuated in any host. Innate immune suppression by NS1 not only enables viral replication in tissues, but also dampens the adaptive immune response and immunological memory. NS1 proteins suppress interferon signaling and effector functions through a variety of protein-protein interactions that may differ from host to host but must achieve similar goals. The multifunctional influenza A virus NS1 protein is highly plastic, highly versatile, and demonstrates a diversity of context-dependent solutions to the problem of interspecies adaptation.
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Affiliation(s)
| | - Katharine E. Magor
- Department of Biological Sciences, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada
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3
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Wang Y, Zhou J, Mackintosh SG, Du Y. RuvB-Like Protein 2 Interacts with the NS1 Protein of Influenza A Virus and Affects Apoptosis That Is Counterbalanced by Type I Interferons. Viruses 2021; 13:v13061038. [PMID: 34072766 PMCID: PMC8229658 DOI: 10.3390/v13061038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/12/2021] [Accepted: 05/28/2021] [Indexed: 11/29/2022] Open
Abstract
The NS1 protein of influenza A virus (IAV) plays important roles in viral pathogenesis and host immune response. Through a proteomic approach, we have identified RuvB-like proteins 1 and 2 (RuvBL1 and RuvBL2) as interacting partners of the NS1 protein of IAVs. Infection of human lung A549 cells with A/PR/8/34 (PR8) virus resulted in reductions in the protein levels of RuvBL2 but not RuvBL1. Further studies with RuvBL2 demonstrated that the NS1-RuvBL2 interaction is RNA-independent, and RuvBL2 binds the RNA-binding domain of the NS1. Infection of interferon (IFN)-deficient Vero cells with wild-type or delNS1 PR8 virus reduced RuvBL2 protein levels and induced apoptosis; delNS1 virus caused more reductions in RuvBL2 protein levels and induced more apoptosis than did wild-type virus. Knockdown of RuvBL2 by siRNAs induced apoptosis and overexpression of RuvBL2 resulted in increased resistance to infection-induced apoptosis in Vero cells. These results suggest that a non-NS1 viral element or elements induce apoptosis by suppressing RuvBL2 protein levels, and the NS1 inhibits the non-NS1 viral element-induced apoptosis by maintaining RuvBL2 abundance in infected cells in the absence of IFN influence. In contrast to Vero cells, infection of IFN-competent A549 cells with PR8 virus caused reductions in RuvBL2 protein levels but did not induce apoptosis. Concomitantly, pretreatment of Vero cells with a recombinant IFN resulted in resistance to infection-induced apoptosis. These results demonstrate that the infection-induced, RuvBL2-regulated apoptosis in infected cells is counterbalanced by IFN survival signals. Our results reveal a novel mechanism underlying the infection-induced apoptosis that can be modulated by the NS1 and type I IFN signaling in IAV-infected cells.
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Affiliation(s)
- Yimeng Wang
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA; (Y.W.); (J.Z.)
| | - Jianhong Zhou
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA; (Y.W.); (J.Z.)
| | - Samuel G. Mackintosh
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA;
| | - Yuchun Du
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA; (Y.W.); (J.Z.)
- Correspondence: ; Tel.: +1-479-575-6944
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4
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Lee K, Zheng Q, Lu Q, Xu F, Qin G, Zhai Q, Hong R, Chen M, Deng W, Wang S. CPSF4 promotes triple negative breast cancer metastasis by upregulating MDM4. Signal Transduct Target Ther 2021; 6:184. [PMID: 34006850 PMCID: PMC8131696 DOI: 10.1038/s41392-021-00565-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 01/26/2021] [Accepted: 02/27/2021] [Indexed: 11/30/2022] Open
Affiliation(s)
- Kaping Lee
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China
| | - Qiufan Zheng
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China
| | - Qianyi Lu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China
| | - Fei Xu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China
| | - Ge Qin
- The Sixth Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China
| | - Qinglian Zhai
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China
| | - Ruoxi Hong
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China
| | - Miao Chen
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
| | - Wuguo Deng
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
| | - Shusen Wang
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China.
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5
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Alpert T, Straube K, Carrillo Oesterreich F, Herzel L, Neugebauer KM. Widespread Transcriptional Readthrough Caused by Nab2 Depletion Leads to Chimeric Transcripts with Retained Introns. Cell Rep 2020; 33:108324. [PMID: 33113357 DOI: 10.1016/j.celrep.2020.108324] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 09/15/2020] [Accepted: 10/07/2020] [Indexed: 01/26/2023] Open
Abstract
Nascent RNA sequencing has revealed that pre-mRNA splicing can occur shortly after introns emerge from RNA polymerase II (RNA Pol II). Differences in co-transcriptional splicing profiles suggest regulation by cis- and/or trans-acting factors. Here, we use single-molecule intron tracking (SMIT) to identify a cohort of regulators by machine learning in budding yeast. Of these, Nab2 displays reduced co-transcriptional splicing when depleted. Unexpectedly, these splicing defects are attributable to aberrant "intrusive" transcriptional readthrough from upstream genes, as revealed by long-read sequencing. Transcripts that originate from the intron-containing gene's own transcription start site (TSS) are efficiently spliced, indicating no direct role of Nab2 in splicing per se. This work highlights the coupling between transcription, splicing, and 3' end formation in the context of gene organization along chromosomes. We conclude that Nab2 is required for proper 3' end processing, which ensures gene-specific control of co-transcriptional RNA processing.
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Affiliation(s)
- Tara Alpert
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Korinna Straube
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | | | - Lydia Herzel
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Karla M Neugebauer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
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6
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He Y, Fu W, Cao K, He Q, Ding X, Chen J, Zhu L, Chen T, Ding L, Yang Y, Zhu C, Yuan S, Li Z, Zhao C, Zhang X, Xu J. IFN-κ suppresses the replication of influenza A viruses through the IFNAR-MAPK-Fos-CHD6 axis. Sci Signal 2020; 13:13/626/eaaz3381. [PMID: 32265337 DOI: 10.1126/scisignal.aaz3381] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Type I interferons (IFNs) are the first line of defense against viral infection. Using a mouse model of influenza A virus infection, we found that IFN-κ was one of the earliest responding type I IFNs after infection with H9N2, a low-pathogenic avian influenza A virus, whereas this early induction did not occur upon infection with the epidemic-causing H7N9 virus. IFN-κ efficiently suppressed the replication of various influenza viruses in cultured human lung cells, and chromodomain helicase DNA binding protein 6 (CHD6) was the major effector for the antiviral activity of IFN-κ, but not for that of IFN-α or IFN-β. The induction of CHD6 required both of the type I IFN receptor subunits IFNAR1 and IFNAR2, the mitogen-activated protein kinase (MAPK) p38, and the transcription factor c-Fos but was independent of signal transducer and activator of transcription 1 (STAT1) activity. In addition, we showed that pretreatment with IFN-κ protected mice from lethal influenza viral challenge. Together, our findings identify an IFN-κ-specific pathway that constrains influenza A virus and provide evidence that IFN-κ may have potential as a preventative and therapeutic agent against influenza A virus.
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Affiliation(s)
- Yongquan He
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Weihui Fu
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Kangli Cao
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Qian He
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Xiangqing Ding
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Jian Chen
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Lingyan Zhu
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Tianyue Chen
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Longfei Ding
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Yu Yang
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Cuisong Zhu
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Songhua Yuan
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China
| | - Zejun Li
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, P. R. China
| | - Chen Zhao
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China.
| | - Xiaoyan Zhang
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China. .,State Key Laboratory for Infectious Disease Prevention and Control, China Centers for Disease Control and Prevention, Beijing 102206, P. R. China
| | - Jianqing Xu
- Shanghai Public Health Clinical Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 201508, P. R. China. .,State Key Laboratory for Infectious Disease Prevention and Control, China Centers for Disease Control and Prevention, Beijing 102206, P. R. China
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7
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Rosário-Ferreira N, Preto AJ, Melo R, Moreira IS, Brito RMM. The Central Role of Non-Structural Protein 1 (NS1) in Influenza Biology and Infection. Int J Mol Sci 2020; 21:E1511. [PMID: 32098424 PMCID: PMC7073157 DOI: 10.3390/ijms21041511] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 01/23/2020] [Accepted: 01/24/2020] [Indexed: 01/07/2023] Open
Abstract
Influenza (flu) is a contagious viral disease, which targets the human respiratory tract and spreads throughout the world each year. Every year, influenza infects around 10% of the world population and between 290,000 and 650,000 people die from it according to the World Health Organization (WHO). Influenza viruses belong to the Orthomyxoviridae family and have a negative sense eight-segment single-stranded RNA genome that encodes 11 different proteins. The only control over influenza seasonal epidemic outbreaks around the world are vaccines, annually updated according to viral strains in circulation, but, because of high rates of mutation and recurrent genetic assortment, new viral strains of influenza are constantly emerging, increasing the likelihood of pandemics. Vaccination effectiveness is limited, calling for new preventive and therapeutic approaches and a better understanding of the virus-host interactions. In particular, grasping the role of influenza non-structural protein 1 (NS1) and related known interactions in the host cell is pivotal to better understand the mechanisms of virus infection and replication, and thus propose more effective antiviral approaches. In this review, we assess the structure of NS1, its dynamics, and multiple functions and interactions, to highlight the central role of this protein in viral biology and its potential use as an effective therapeutic target to tackle seasonal and pandemic influenza.
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Affiliation(s)
- Nícia Rosário-Ferreira
- Coimbra Chemistry Center, Chemistry Department, Faculty of Science and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
- CNC—Center for Neuroscience and Cell Biology. University of Coimbra, UC Biotech Building, 3060-197 Cantanhede, Portugal
| | - António J. Preto
- CNC—Center for Neuroscience and Cell Biology. University of Coimbra, UC Biotech Building, 3060-197 Cantanhede, Portugal
| | - Rita Melo
- CNC—Center for Neuroscience and Cell Biology. University of Coimbra, UC Biotech Building, 3060-197 Cantanhede, Portugal
- Centro de Ciências e Tecnologias Nucleares and Departamento de Engenharia e Ciências Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela LRS, Portugal
| | - Irina S. Moreira
- CNC—Center for Neuroscience and Cell Biology. University of Coimbra, UC Biotech Building, 3060-197 Cantanhede, Portugal
- Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
| | - Rui M. M. Brito
- Coimbra Chemistry Center, Chemistry Department, Faculty of Science and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
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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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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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10
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A Naturally Occurring Deletion in the Effector Domain of H5N1 Swine Influenza Virus Nonstructural Protein 1 Regulates Viral Fitness and Host Innate Immunity. J Virol 2018; 92:JVI.00149-18. [PMID: 29563291 DOI: 10.1128/jvi.00149-18] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 03/14/2018] [Indexed: 01/02/2023] Open
Abstract
Nonstructural protein 1 (NS1) of influenza A virus regulates innate immune responses via various mechanisms. We previously showed that a naturally occurring deletion (the EALQR motif) in the NS1 effector domain of an H5N1 swine-origin avian influenza virus impairs the inhibition of type I interferon (IFN) in chicken fibroblasts and attenuates virulence in chickens. Here we found that the virus bearing this deletion in its NS1 effector domain showed diminished inhibition of IFN-related cytokine expression and attenuated virulence in mice. We further showed that deletion of the EALQR motif disrupted NS1 dimerization, impairing double-stranded RNA (dsRNA) sequestration and competitive binding with RIG-I. In addition, the EALQR-deleted NS1 protein could not bind to TRIM25, unlike full-length NS1, and was less able to block TRIM25 oligomerization and self-ubiquitination, further impairing the inhibition of TRIM25-mediated RIG-I ubiquitination compared to that with full-length NS1. Our data demonstrate that the EALQR deletion prevents NS1 from blocking RIG-I-mediated IFN induction via a novel mechanism to attenuate viral replication and virulence in mammalian cells and animals.IMPORTANCE H5 highly pathogenic avian influenza viruses have infected more than 800 individuals across 16 countries, with an overall case fatality rate of 53%. Among viral proteins, nonstructural protein 1 (NS1) of influenza virus is considered a key determinant for type I interferon (IFN) antagonism, pathogenicity, and host range. However, precisely how NS1 modulates virus-host interaction, facilitating virus survival, is not fully understood. Here we report that a naturally occurring deletion (of the EALQR motif) in the NS1 effector domain of an H5N1 swine-origin avian influenza virus disrupted NS1 dimerization, which diminished the blockade of IFN induction via the RIG-I signaling pathway, thereby impairing virus replication and virulence in the host. Our study demonstrates that the EALQR motif of NS1 regulates virus fitness to attain a virus-host compromise state in animals and identifies this critical motif as a potential target for the future development of small molecular drugs and attenuated vaccines.
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11
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Vasin AV, Petrova-Brodskaya AV, Plotnikova MA, Tsvetkov VB, Klotchenko SA. EVOLUTIONARY DYNAMICS OF STRUCTURAL AND FUNCTIONAL DOMAINS OF INFLUENZA A VIRUS NS1 PROTEIN. Vopr Virusol 2017; 62:246-258. [PMID: 36494956 DOI: 10.18821/0507-4088-2017-62-6-246-258] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Indexed: 12/13/2022]
Abstract
Influenza A virus (IAV) NS1 protein is one of the key viral factors responsible for virus-host interactions. NS1 counteracts host antiviral defense, participates in the processing and export of cellular mRNAs, regulates the activity of viral RNA polymerase and the expression of viral genes, and influences the cellular signaling systems. Multiple NS1 functions are carried out due to the interactions with cellular factors, the number of which exceeds one hundred. It is noteworthy that only two segments of IAV genome - NS and NP - did not undergo reassortment and evolved in the course of genetic drift, beginning with the pandemic of 1918 to the present. This fact may indicate the importance of NS1 and its numerous interactions with cellular factors in the interspecific adaptation of the virus. The review presents data on the evolution of the human IAV NS1 protein and analysis of the amino acid substitutions in the main structural and functional domains of NS1 protein during evolution.
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Affiliation(s)
- A V Vasin
- Research Institute of Influenza.,Peter the Great St. Petersburg Polytechnic University
| | - A V Petrova-Brodskaya
- Research Institute of Influenza.,Peter the Great St. Petersburg Polytechnic University
| | | | - V B Tsvetkov
- Research Institute of Influenza.,A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences.,Federal Research and Clinical Center of Physical-Chemical Medicine
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12
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Tsai CF, Lin HY, Hsu WL, Tsai CH. The novel mitochondria localization of influenza A virus NS1 visualized by FlAsH labeling. FEBS Open Bio 2017; 7:1960-1971. [PMID: 29226082 PMCID: PMC5715299 DOI: 10.1002/2211-5463.12336] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 10/06/2017] [Accepted: 10/08/2017] [Indexed: 12/11/2022] Open
Abstract
The nonstructural protein 1 (NS1) of the influenza A virus (IAV) is a multifunctional protein that counteracts host cell antiviral responses and inhibits host cell pre‐mRNA processing. NS1 contains two nuclear localization signals that facilitate NS1 shuttling between cytoplasm and nucleus. In this study, we initially observed the novel mitochondria localization of NS1 in a subset of transfected cells. We then further monitored the localization dynamics of the NS1 protein in live cells infected with IAV expressing NS1 with insertion of a tetracysteine‐tag. The resulting mutant virus showed similar levels of infectivity and expression pattern of NS1 to those of wild‐type IAV. Pulse labeling using a biarsenical compound (fluorescein arsenical hairpin binder) allowed us to visualize the dynamic subcellular distribution of NS1 real time. We detected NS1 in mitochondria at a very early infection time point [1.5 h postinfection (hpi)] and observed the formation of a granular structure pattern in the nucleus at 4 hpi. This is the first identification of the novel mitochondria localization of NS1. The possible role of NS1 at an early infection time point is discussed.
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Affiliation(s)
- Chuan-Fu Tsai
- Graduate Institute of Biotechnology National Chung Hsing University Taichung Taiwan
| | - Hsin-Yi Lin
- Graduate Institute of Biotechnology National Chung Hsing University Taichung Taiwan
| | - Wei-Li Hsu
- Graduate Institute of Microbiology and Public Health National Chung Hsing University Taichung Taiwan
| | - Ching-Hsiu Tsai
- Graduate Institute of Biotechnology National Chung Hsing University Taichung Taiwan
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13
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Wang BX, Brown EG, Fish EN. Residues F103 and M106 within the influenza A virus NS1 CPSF4-binding region regulate interferon-stimulated gene translation initiation. Virology 2017; 508:170-179. [PMID: 28554059 DOI: 10.1016/j.virol.2017.05.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/10/2017] [Accepted: 05/11/2017] [Indexed: 11/25/2022]
Abstract
Influenza A virus (IAV) non-structural protein 1 (NS1) suppresses host innate immune responses by inhibiting type I interferon (IFN) production. We provide evidence that residues F103 and M106 in the CPSF4-binding domain of A/HK/1/68 [H3N2] NS1 contribute to post-transcriptional inhibition of antiviral IFN-stimulated genes (ISGs), thereby suppressing an antiviral type I IFN response. Recombinant (r) IAVs encoding F103L and M106I mutations in NS1 replicate to significantly lower viral titers in human A549 lung epithelial cells and primary type II alveolar cells. In A549 cells, rIAVs encoding these mutant NS1s induce higher levels of IFN-β production and are more sensitive to the antiviral effects of IFN-β treatment. qPCR characterization of polysomal mRNA, in the presence or absence of IFN-β treatment, identified a greater proportion of heavy polysome-associated ISGs including EIF2AK2, OAS1, and MxA in A549 cells infected with rIAVs encoding these CPSF4-binding mutant NS1s, in contrast to rIAV encoding wildtype NS1.
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Affiliation(s)
- Ben X Wang
- Department of Immunology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8; Toronto General Hospital Research Institute, University Health Network, 67 College Street, Room 424, Toronto, Ontario, Canada M5G 2M1
| | - Earl G Brown
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
| | - Eleanor N Fish
- Department of Immunology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8; Toronto General Hospital Research Institute, University Health Network, 67 College Street, Room 424, Toronto, Ontario, Canada M5G 2M1.
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14
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Verbeeren J, Verma B, Niemelä EH, Yap K, Makeyev EV, Frilander MJ. Alternative exon definition events control the choice between nuclear retention and cytoplasmic export of U11/U12-65K mRNA. PLoS Genet 2017; 13:e1006824. [PMID: 28549066 PMCID: PMC5473595 DOI: 10.1371/journal.pgen.1006824] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 06/16/2017] [Accepted: 05/16/2017] [Indexed: 12/20/2022] Open
Abstract
Cellular homeostasis of the minor spliceosome is regulated by a negative feed-back loop that targets U11-48K and U11/U12-65K mRNAs encoding essential components of the U12-type intron-specific U11/U12 di-snRNP. This involves interaction of the U11 snRNP with an evolutionarily conserved splicing enhancer giving rise to unproductive mRNA isoforms. In the case of U11/U12-65K, this mechanism controls the length of the 3′ untranslated region (3′UTR). We show that this process is dynamically regulated in developing neurons and some other cell types, and involves a binary switch between translation-competent mRNAs with a short 3′UTR to non-productive isoforms with a long 3′UTR that are retained in the nucleus or/and spliced to the downstream amylase locus. Importantly, the choice between these alternatives is determined by alternative terminal exon definition events regulated by conserved U12- and U2-type 5′ splice sites as well as sequence signals used for pre-mRNA cleavage and polyadenylation. We additionally show that U11 snRNP binding to the U11/U12-65K mRNA species with a long 3′UTR is required for their nuclear retention. Together, our studies uncover an intricate molecular circuitry regulating the abundance of a key spliceosomal protein and shed new light on the mechanisms limiting the export of non-productively spliced mRNAs from the nucleus to the cytoplasm. The cellular homeostasis of many components of the eukaryotic RNA processing machinery is regulated via negative feed-back pathways that result in the formation of both productive and non-productive mRNA species. Typically, the formation of non-productive mRNAs species results from changes in alternative splicing that disrupt the reading frame of the protein coding region and leads to destabilization of the mRNA. Here, we have investigated the homeostasis regulation of the U11/U12-65K mRNA that encodes an essential protein component of the minor (U12-dependent) spliceosome intron recognition complex. We show that homeostasis is regulated at the level of nuclear mRNA export and mRNA 3′-end formation, and that it can be further regulated during neuronal differentiation. We describe a multilayered regulatory system utilizing alternative exon definition interactions that use the input from both spliceosomes and the polyadenylation machinery to decide between productive and non-productive mRNA formation. Because the 65K protein is an essential component of the minor spliceosome, this regulatory pathway can potentially affect the expression of ~700 genes containing U12-type introns.
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Affiliation(s)
- Jens Verbeeren
- Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland
| | - Bhupendra Verma
- Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland
| | - Elina H. Niemelä
- Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland
| | - Karen Yap
- Centre for Developmental Neurobiology, King’s College London, London, United Kingdom
| | - Eugene V. Makeyev
- Centre for Developmental Neurobiology, King’s College London, London, United Kingdom
| | - Mikko J. Frilander
- Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland
- * E-mail:
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15
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A Conserved Residue, Tyrosine (Y) 84, in H5N1 Influenza A Virus NS1 Regulates IFN Signaling Responses to Enhance Viral Infection. Viruses 2017; 9:v9050107. [PMID: 28498306 PMCID: PMC5454420 DOI: 10.3390/v9050107] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 05/10/2017] [Indexed: 01/24/2023] Open
Abstract
The non-structural protein, NS1, is a virulence factor encoded by influenza A viruses (IAVs). In this report, we provide evidence that the conserved residue, tyrosine (Y) 84, in a conserved putative SH2-binding domain in A/Duck/Hubei/2004/L-1 [H5N1] NS1 is critical for limiting an interferon (IFN) response to infection. A phenylalanine (F) substitution of this Y84 residue abolishes NS1-mediated downregulation of IFN-inducible STAT phosphorylation, and surface IFNAR1 expression. Recombinant IAV (rIAV) [H1N1] expressing A/Grey Heron/Hong Kong/837/2004 [H5N1] NS1-Y84F (rWSN-GH-NS1-Y84F) replicates to lower titers in human lung epithelial cells and is more susceptible to the antiviral effects of IFN-β treatment compared with rIAV expressing the intact H5N1 NS1 (rWSN-GH-NS1-wt). Cells infected with rWSN-GH-NS1-Y84F express higher levels of IFN stimulated genes (ISGs) associated with an antiviral response compared with cells infected with rWSN-GH-NS1-wt. In mice, intranasal infection with rWSN-GH-NS1-Y84F resulted in a delay in onset of weight loss, reduced lung pathology, lower lung viral titers and higher ISG expression, compared with mice infected with rWSN-GH-NS1-wt. IFN-β treatment of mice infected with rWSN-GH-NS1-Y84F reduced lung viral titers and increased lung ISG expression, but did not alter viral titers and ISG expression in mice infected with rWSN-GH-NS1-wt. Viewed altogether, these data suggest that the virulence associated with this conserved Y84 residue in NS1 is, in part, due to its role in regulating the host IFN response.
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16
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Stegeman R, Spreacker PJ, Swanson SK, Stephenson R, Florens L, Washburn MP, Weake VM. The Spliceosomal Protein SF3B5 is a Novel Component of Drosophila SAGA that Functions in Gene Expression Independent of Splicing. J Mol Biol 2016; 428:3632-49. [PMID: 27185460 PMCID: PMC5011000 DOI: 10.1016/j.jmb.2016.05.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 04/19/2016] [Accepted: 05/08/2016] [Indexed: 12/16/2022]
Abstract
The interaction between splicing factors and the transcriptional machinery provides an intriguing link between the coupled processes of transcription and splicing. Here, we show that the two components of the SF3B complex, SF3B3 and SF3B5, that form part of the U2 small nuclear ribonucleoprotein particle (snRNP) are also subunits of the Spt-Ada-Gcn5 acetyltransferase (SAGA) transcriptional coactivator complex in Drosophila melanogaster. Whereas SF3B3 had previously been identified as a human SAGA subunit, SF3B5 had not been identified as a component of SAGA in any species. We show that SF3B3 and SF3B5 bind to SAGA independent of RNA and interact with multiple SAGA subunits including Sgf29 and Spt7 in a yeast two-hybrid assay. Through analysis of sf3b5 mutant flies, we show that SF3B5 is necessary for proper development and cell viability but not for histone acetylation. Although SF3B5 does not appear to function in SAGA's histone-modifying activities, SF3B5 is still required for expression of a subset of SAGA-regulated genes independent of splicing. Thus, our data support an independent function of SF3B5 in SAGA's transcription coactivator activity that is separate from its role in splicing.
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Affiliation(s)
- Rachel Stegeman
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Peyton J Spreacker
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Selene K Swanson
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA
| | - Robert Stephenson
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Laurence Florens
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA
| | - Michael P Washburn
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, MO 64110, USA; Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Vikki M Weake
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA; Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA.
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17
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Ogorodnikov A, Kargapolova Y, Danckwardt S. Processing and transcriptome expansion at the mRNA 3' end in health and disease: finding the right end. Pflugers Arch 2016; 468:993-1012. [PMID: 27220521 PMCID: PMC4893057 DOI: 10.1007/s00424-016-1828-3] [Citation(s) in RCA: 30] [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: 04/12/2016] [Accepted: 04/19/2016] [Indexed: 01/09/2023]
Abstract
The human transcriptome is highly dynamic, with each cell type, tissue, and organ system expressing an ensemble of transcript isoforms that give rise to considerable diversity. Apart from alternative splicing affecting the "body" of the transcripts, extensive transcriptome diversification occurs at the 3' end. Transcripts differing at the 3' end can have profound physiological effects by encoding proteins with distinct functions or regulatory properties or by affecting the mRNA fate via the inclusion or exclusion of regulatory elements (such as miRNA or protein binding sites). Importantly, the dynamic regulation at the 3' end is associated with various (patho)physiological processes, including the immune regulation but also tumorigenesis. Here, we recapitulate the mechanisms of constitutive mRNA 3' end processing and review the current understanding of the dynamically regulated diversity at the transcriptome 3' end. We illustrate the medical importance by presenting examples that are associated with perturbations of this process and indicate resulting implications for molecular diagnostics as well as potentially arising novel therapeutic strategies.
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Affiliation(s)
- Anton Ogorodnikov
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center Mainz, Langenbeckstr 1, 55131, Mainz, Germany
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz, Langenbeckstr 1, 55131, Mainz, Germany
| | - Yulia Kargapolova
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center Mainz, Langenbeckstr 1, 55131, Mainz, Germany
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz, Langenbeckstr 1, 55131, Mainz, Germany
| | - Sven Danckwardt
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center Mainz, Langenbeckstr 1, 55131, Mainz, Germany.
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz, Langenbeckstr 1, 55131, Mainz, Germany.
- German Center for Cardiovascular Research (DZHK), Langenbeckstr 1, 55131, Mainz, Germany.
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18
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Kuo RL, Li ZH, Li LH, Lee KM, Tam EH, Liu HM, Liu HP, Shih SR, Wu CC. Interactome Analysis of the NS1 Protein Encoded by Influenza A H1N1 Virus Reveals a Positive Regulatory Role of Host Protein PRP19 in Viral Replication. J Proteome Res 2016; 15:1639-48. [PMID: 27096427 DOI: 10.1021/acs.jproteome.6b00103] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Influenza A virus, which can cause severe respiratory illnesses in infected individuals, is responsible for worldwide human pandemics. The NS1 protein encoded by this virus plays a crucial role in regulating the host antiviral response through various mechanisms. In addition, it has been reported that NS1 can modulate cellular pre-mRNA splicing events. To investigate the biological processes potentially affected by the NS1 protein in host cells, NS1-associated protein complexes in human cells were identified using coimmunoprecipitation combined with GeLC-MS/MS. By employing software to build biological process and protein-protein interaction networks, NS1-interacting cellular proteins were found to be related to RNA splicing/processing, cell cycle, and protein folding/targeting cellular processes. By monitoring spliced and unspliced RNAs of a reporter plasmid, we further validated that NS1 can interfere with cellular pre-mRNA splicing. One of the identified proteins, pre-mRNA-processing factor 19 (PRP19), was confirmed to interact with the NS1 protein in influenza A virus-infected cells. Importantly, depletion of PRP19 in host cells reduced replication of influenza A virus. In summary, the interactome of influenza A virus NS1 in host cells was comprehensively profiled, and our findings reveal a novel regulatory role for PRP19 in viral replication.
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Affiliation(s)
| | | | | | | | | | - Helene M Liu
- Department of Clinical Laboratory Sciences and Medical Technology, College of Medicine, National Taiwan University , Taipei 10617, Taiwan
| | - Hao-Ping Liu
- Department of Veterinary Medicine, National Chung Hsing University , Taichung 40227, Taiwan
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19
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Misra A, Green MR. From polyadenylation to splicing: Dual role for mRNA 3' end formation factors. RNA Biol 2015; 13:259-64. [PMID: 26891005 DOI: 10.1080/15476286.2015.1112490] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Recent genome-wide protein-RNA interaction studies have significantly reshaped our understanding of the role of mRNA 3' end formation factors in RNA biology. Originally thought to function solely in mediating cleavage and polyadenylation of mRNAs during their maturation, 3' end formation factors have now been shown to play a role in alternative splicing, even at internal introns--an unanticipated role for factors thought only to act at the 3' end of the mRNA. Here, we discuss the recent advances in our understanding of the role of 3' end formation factors in promoting global changes in alternative splicing at internal exon-intron junctions and how they act as cofactors for well known splicing regulators. Additionally, we review the mechanism by which these factors affect the recruitment of early intron recognition components to the 5' and 3' splice site. Our understanding of the roles of 3' end formation factors is still evolving, and the final picture might be more complex than originally envisioned.
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Affiliation(s)
- Ashish Misra
- a Howard Hughes Medical Institute and Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School , Worcester , MA USA
| | - Michael R Green
- a Howard Hughes Medical Institute and Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School , Worcester , MA USA
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20
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Jureka AS, Kleinpeter AB, Cornilescu G, Cornilescu CC, Petit CM. Structural Basis for a Novel Interaction between the NS1 Protein Derived from the 1918 Influenza Virus and RIG-I. Structure 2015; 23:2001-10. [PMID: 26365801 PMCID: PMC4635043 DOI: 10.1016/j.str.2015.08.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 08/12/2015] [Accepted: 08/14/2015] [Indexed: 10/23/2022]
Abstract
The influenza non-structural protein 1 (NS1) plays a critical role in antagonizing the innate immune response to infection. One interaction that facilitates this function is between NS1 and RIG-I, one of the main sensors of influenza virus infection. While NS1 and RIG-I are known to interact, it is currently unclear whether this interaction is direct or if it is mediated by other biomolecules. Here we demonstrate a direct, strain-dependent interaction between the NS1 RNA binding domain (NS1(RBD)) of the influenza A/Brevig Mission/1918 H1N1 (1918(H1N1)) virus and the second caspase activation and recruitment domain of RIG-I. Solving the solution structure of the 1918(H1N1) NS1(RBD) revealed features in a functionally novel region that may facilitate the observed interaction. The biophysical and structural data herein suggest a possible mechanism by which strain-specific differences in NS1 modulate influenza virulence.
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Affiliation(s)
- Alexander S Jureka
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Alex B Kleinpeter
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Gabriel Cornilescu
- National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Claudia C Cornilescu
- National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Chad M Petit
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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21
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Cheong WC, Kang HR, Yoon H, Kang SJ, Ting JPY, Song MJ. Influenza A Virus NS1 Protein Inhibits the NLRP3 Inflammasome. PLoS One 2015; 10:e0126456. [PMID: 25978411 PMCID: PMC4433236 DOI: 10.1371/journal.pone.0126456] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 04/02/2015] [Indexed: 12/23/2022] Open
Abstract
The inflammasome is a molecular platform that stimulates the activation of caspase-1 and the processing of pro-interleukin (IL)-1β and pro-IL-18 for secretion. The NOD-like receptor family, pyrin domain containing 3 (NLRP3) protein is activated by diverse molecules and pathogens, leading to the formation of the NLRP3 inflammasome. Recent studies showed that the NLRP3 inflammasome mediates innate immunity against influenza A virus (IAV) infection. In this study, we investigated the function of the IAV non-structural protein 1 (NS1) in the modulation of NLRP3 inflammasome. We found that NS1 proteins derived from both highly pathogenic and low pathogenic strains efficiently decreased secretion of IL-1β and IL-18 from THP-1 cells treated with LPS and ATP. NS1 overexpression significantly impaired the transcription of proinflammatory cytokines by inhibiting transactivation of the nuclear factor-κB (NF-κB), a major transcription activator. Furthermore, NS1 physically interacted with endogenous NLRP3 and activation of the NLRP3 inflammasome was abrogated in NS1-expressing THP-1 cells. These findings suggest that NS1 downregulates NLRP3 inflammasome activation by targeting NLRP3 as well as NF-κB, leading to a reduction in the levels of inflammatory cytokines as a viral immune evasion strategy.
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Affiliation(s)
- Woo-Chang Cheong
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 136–713, Republic of Korea
| | - Hye-Ri Kang
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 136–713, Republic of Korea
| | - Hyunyee Yoon
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 136–713, Republic of Korea
- Laboratory of Protein Immunology, Biomedical Research Institute, Seoul National University Hospital, Seoul, 110–744, Republic of Korea
| | - Suk-Jo Kang
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, 305–701, Republic of Korea
| | - Jenny P.-Y. Ting
- Departments of Genetics, Microbiology and Immunology, Center for Translational Immunology and Inflammatory Disease Institute, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, United States of America
| | - Moon Jung Song
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 136–713, Republic of Korea
- * E-mail:
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22
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Poly(A) Polymerase and the Nuclear Poly(A) Binding Protein, PABPN1, Coordinate the Splicing and Degradation of a Subset of Human Pre-mRNAs. Mol Cell Biol 2015; 35:2218-30. [PMID: 25896913 PMCID: PMC4456446 DOI: 10.1128/mcb.00123-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 04/11/2015] [Indexed: 12/13/2022] Open
Abstract
Most human protein-encoding transcripts contain multiple introns that are removed by splicing. Although splicing catalysis is frequently cotranscriptional, some introns are excised after polyadenylation. Accumulating evidence suggests that delayed splicing has regulatory potential, but the mechanisms are still not well understood. Here we identify a terminal poly(A) tail as being important for a subset of intron excision events that follow cleavage and polyadenylation. In these cases, splicing is promoted by the nuclear poly(A) binding protein, PABPN1, and poly(A) polymerase (PAP). PABPN1 promotes intron excision in the context of 3′-end polyadenylation but not when bound to internal A-tracts. Importantly, the ability of PABPN1 to promote splicing requires its RNA binding and, to a lesser extent, PAP-stimulatory functions. Interestingly, an N-terminal alanine expansion in PABPN1 that is thought to cause oculopharyngeal muscular dystrophy cannot completely rescue the effects of PABPN1 depletion, suggesting that this pathway may have relevance to disease. Finally, inefficient polyadenylation is associated with impaired recruitment of splicing factors to affected introns, which are consequently degraded by the exosome. Our studies uncover a new function for polyadenylation in controlling the expression of a subset of human genes via pre-mRNA splicing.
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23
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Machinaga A, Takase-Yoden S. Polyadenylation of Friend murine leukemia virus env-mRNA is affected by its splicing. Microbiol Immunol 2015; 58:474-82. [PMID: 24935657 DOI: 10.1111/1348-0421.12170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 05/19/2014] [Accepted: 06/10/2014] [Indexed: 01/27/2023]
Abstract
As splicing was previously found to be important for increasing Friend murine leukemia virus env-mRNA stability and translation, we investigated whether splicing of env-mRNA affected the poly(A) tail length using env expression vectors that yielded unspliced or spliced env-mRNA. Incomplete polyadenylation was detected in a fraction of the unspliced env-mRNA products in an env gene-dependent manner, showing that splicing of Friend murine leukemia virus plays an important role in the efficiency of complete polyadenylation of env-mRNA. These results suggested that the promotion of complete polyadenylation of env-mRNA by splicing might partially explain up-regulation of Env protein expression as a result of splicing.
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Affiliation(s)
- Akihito Machinaga
- Department of Bioinformatics, Faculty of Engineering, Soka University, 1-236, Tangi-machi, Hachioji-shi, Tokyo, 192-8577, Japan
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24
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Abstract
The non-structural protein 1 of influenza virus (NS1) is a relatively small polypeptide with an outstanding number of ascribed functions. NS1 is the main viral antagonist of the innate immune response during influenza virus infection, chiefly by inhibiting the type I interferon system at multiple steps. As such, its role is critical to overcome the first barrier the host presents to halt the viral infection. However, the pro-viral activities of this well-studied protein go far beyond and include regulation of viral RNA and protein synthesis, and disruption of the host cell homeostasis by dramatically affecting general gene expression while tweaking the PI3K signaling network. Because of all of this, NS1 is a key virulence factor that impacts influenza pathogenesis, and adaptation to new hosts, making it an attractive target for control strategies. Here, we will overview the many roles that have been ascribed to the NS1 protein, and give insights into the sequence features and structural properties that make them possible, highlighting the need to understand how NS1 can actually perform all of these functions during viral infection.
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Affiliation(s)
- Juan Ayllon
- Department of Microbiology, Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
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25
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Influenza A virus acquires enhanced pathogenicity and transmissibility after serial passages in swine. J Virol 2014; 88:11981-94. [PMID: 25100840 DOI: 10.1128/jvi.01679-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Genetic and phylogenetic analyses suggest that the pandemic H1N1/2009 virus was derived from well-established swine influenza lineages; however, there is no convincing evidence that the pandemic virus was generated from a direct precursor in pigs. Furthermore, the evolutionary dynamics of influenza virus in pigs have not been well documented. Here, we subjected a recombinant virus (rH1N1) with the same constellation makeup as the pandemic H1N1/2009 virus to nine serial passages in pigs. The severity of infection sequentially increased with each passage. Deep sequencing of viral quasispecies from the ninth passage found five consensus amino acid mutations: PB1 A469T, PA 1129T, NA N329D, NS1 N205K, and NEP T48N. Mutations in the hemagglutinin (HA) protein, however, differed greatly between the upper and lower respiratory tracts. Three representative viral clones with the five consensus mutations were selected for functional evaluation. Relative to the parental virus, the three viral clones showed enhanced replication and polymerase activity in vitro and enhanced replication, pathogenicity, and transmissibility in pigs, guinea pigs, and ferrets in vivo. Specifically, two mutants of rH1N1 (PB1 A469T and a combination of NS1 N205K and NEP T48N) were identified as determinants of transmissibility in guinea pigs. Crucially, one mutant viral clone with the five consensus mutations, which also carried D187E, K211E, and S289N mutations in its HA, additionally was able to infect ferrets by airborne transmission as effectively as the pandemic virus. Our findings demonstrate that influenza virus can acquire viral characteristics that are similar to those of the pandemic virus after limited serial passages in pigs. Importance: We demonstrate here that an engineered reassortant swine influenza virus, with the same gene constellation pattern as the pandemic H1N1/2009 virus and subjected to only nine serial passages in pigs, acquired greatly enhanced virulence and transmissibility. In particular, one representative pathogenic passaged virus clone, which carried three mutations in the HA gene and five consensus mutations in PB1, PA, NA, NS1, and NEP genes, additionally was able to confer respiratory droplet transmission as effectively as the pandemic H1N1/2009 virus. Our findings suggest that pigs can readily induce adaptive mutational changes to a precursor pandemic-like virus to transform it into a highly virulent and infectious form akin to that of the pandemic H1N1/2009 virus, which underlines the potential direct role of pigs in promoting influenza A virus pathogenicity and transmissibility.
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Goka EA, Vallely PJ, Mutton KJ, Klapper PE. Mutations associated with severity of the pandemic influenza A(H1N1)pdm09 in humans: a systematic review and meta-analysis of epidemiological evidence. Arch Virol 2014; 159:3167-83. [PMID: 25078388 DOI: 10.1007/s00705-014-2179-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 07/12/2014] [Indexed: 10/25/2022]
Abstract
Mutations in the haemagglutinin (HA), non-structural protein 1 (NS1) and polymerase basic protein 2 (PB2) of influenza viruses have been associated with virulence. This study investigated the association between mutations in these genes in influenza A(H1N1)pdm09 virus and the risk of severe or fatal disease. Searches were conducted on the MEDLINE, EMBASE and Web of Science electronic databases and the reference lists of published studies. The PRISMA and STROBE guidelines were followed in assessing the quality of studies and writing-up. Eighteen (18) studies, from all continents, were included in the systematic review (recruiting patients 0 - 77 years old). The mutation D222G was associated with a significant increase in severe disease (pooled RD: 11 %, 95 % CI: 3.0 % - 18.0 %, p = 0.004) and the risk of fatality (RD: 23 %, 95 % CI: 14.0 %-31.0 %, p = < 0.0001). No association was observed between the mutations HA-D222N, D222E, PB2-E627K and NS1-T123V and severe/fatal disease. The results suggest that no virus quasispecies bearing virulence-conferring mutations in the HA, PB2 and NS1 predominated. However issues of sampling bias, and bias due to uncontrolled confounders such as comorbidities, and viral and bacterial coinfection, should be born in mind. Influenza A viruses should continue to be monitored for the occurrence of virulence-conferring mutations in HA, PB2 and NS1. There are suggestions that respiratory virus coinfections also affect virus virulence. Studies investigating the role of genetic mutations on disease outcome should make efforts to also investigate the role of respiratory virus coinfections.
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Affiliation(s)
- E A Goka
- Institute of Inflammation and Repair, Faculty of Medical and Human Sciences, University of Manchester, 1st Floor Stopford building, Oxford Road, Manchester, M13 9PL, UK,
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Pérez-Cidoncha M, Killip MJ, Asensio VJ, Fernández Y, Bengoechea JA, Randall RE, Ortín J. Generation of replication-proficient influenza virus NS1 point mutants with interferon-hyperinducer phenotype. PLoS One 2014; 9:e98668. [PMID: 24887174 PMCID: PMC4041880 DOI: 10.1371/journal.pone.0098668] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 05/05/2014] [Indexed: 12/24/2022] Open
Abstract
The NS1 protein of influenza A viruses is the dedicated viral interferon (IFN)-antagonist. Viruses lacking NS1 protein expression cannot multiply in normal cells but are viable in cells deficient in their ability to produce or respond to IFN. Here we report an unbiased mutagenesis approach to identify positions in the influenza A NS1 protein that modulate the IFN response upon infection. A random library of virus ribonucleoproteins containing circa 40 000 point mutants in NS1 were transferred to infectious virus and amplified in MDCK cells unable to respond to interferon. Viruses that activated the interferon (IFN) response were subsequently selected by their ability to induce expression of green-fluorescent protein (GFP) following infection of A549 cells bearing an IFN promoter-dependent GFP gene. Using this approach we isolated individual mutant viruses that replicate to high titers in IFN-compromised cells but, compared to wild type viruses, induced higher levels of IFN in IFN-competent cells and had a reduced capacity to counteract exogenous IFN. Most of these viruses contained not previously reported NS1 mutations within either the RNA-binding domain, the effector domain or the linker region between them. These results indicate that subtle alterations in NS1 can reduce its effectiveness as an IFN antagonist without affecting the intrinsic capacity of the virus to multiply. The general approach reported here may facilitate the generation of replication-proficient, IFN-inducing virus mutants, that potentially could be developed as attenuated vaccines against a variety of viruses.
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Affiliation(s)
- Maite Pérez-Cidoncha
- Department of Molecular and Cellular Biology, Centro Nacional de Biotecnología (CSIC), Madrid, Spain
- Ciber de Enfermedades Respiratorias (ISCIII), Madrid, Spain
| | - Marian J. Killip
- School of Biology, Centre for Biomolecular Sciences, University of St Andrews, St Andrews, United Kingdom
| | - Víctor J. Asensio
- Fundació d'Investigació Sanitària de les Illes Balears (FISIB), Bunyola, Mallorca, Spain
| | - Yolanda Fernández
- Department of Molecular and Cellular Biology, Centro Nacional de Biotecnología (CSIC), Madrid, Spain
- Ciber de Enfermedades Respiratorias (ISCIII), Madrid, Spain
| | - José A. Bengoechea
- Laboratory Microbial Pathogenesis, Fundació d'Investigació Sanitària de les Illes Balears (FISIB), Bunyola, Mallorca, Spain
- Ciber de Enfermedades Respiratorias (ISCIII), Madrid, Spain
| | - Richard E. Randall
- School of Biology, Centre for Biomolecular Sciences, University of St Andrews, St Andrews, United Kingdom
| | - Juan Ortín
- Department of Molecular and Cellular Biology, Centro Nacional de Biotecnología (CSIC), Madrid, Spain
- Ciber de Enfermedades Respiratorias (ISCIII), Madrid, Spain
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An unbiased genetic screen reveals the polygenic nature of the influenza virus anti-interferon response. J Virol 2014; 88:4632-46. [PMID: 24574395 PMCID: PMC3993829 DOI: 10.1128/jvi.00014-14] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Influenza A viruses counteract the cellular innate immune response at several steps, including blocking RIG I-dependent activation of interferon (IFN) transcription, interferon (IFN)-dependent upregulation of IFN-stimulated genes (ISGs), and the activity of various ISG products; the multifunctional NS1 protein is responsible for most of these activities. To determine the importance of other viral genes in the interplay between the virus and the host IFN response, we characterized populations and selected mutants of wild-type viruses selected by passage through non-IFN-responsive cells. We reasoned that, by allowing replication to occur in the absence of the selection pressure exerted by IFN, the virus could mutate at positions that would normally be restricted and could thus find new optimal sequence solutions. Deep sequencing of selected virus populations and individual virus mutants indicated that nonsynonymous mutations occurred at many phylogenetically conserved positions in nearly all virus genes. Most individual mutants selected for further characterization induced IFN and ISGs and were unable to counteract the effects of exogenous IFN, yet only one contained a mutation in NS1. The relevance of these mutations for the virus phenotype was verified by reverse genetics. Of note, several virus mutants expressing intact NS1 proteins exhibited alterations in the M1/M2 proteins and accumulated large amounts of deleted genomic RNAs but nonetheless replicated to high titers. This suggests that the overproduction of IFN inducers by these viruses can override NS1-mediated IFN modulation. Altogether, the results suggest that influenza viruses replicating in IFN-competent cells have tuned their complete genomes to evade the cellular innate immune system and that serial replication in non-IFN-responsive cells allows the virus to relax from these constraints and find a new genome consensus within its sequence space. IMPORTANCE In natural virus infections, the production of interferons leads to an antiviral state in cells that effectively limits virus replication. The interferon response places considerable selection pressure on viruses, and they have evolved a variety of ways to evade it. Although the influenza virus NS1 protein is a powerful interferon antagonist, the contributions of other viral genes to interferon evasion have not been well characterized. Here, we examined the effects of alleviating the selection pressure exerted by interferon by serially passaging influenza viruses in cells unable to respond to interferon. Viruses that grew to high titers had mutations at many normally conserved positions in nearly all genes and were not restricted to the NS1 gene. Our results demonstrate that influenza viruses have fine-tuned their entire genomes to evade the interferon response, and by removing interferon-mediated constraints, viruses can mutate at genome positions normally restricted by the interferon response.
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Genomewide analysis of reassortment and evolution of human influenza A(H3N2) viruses circulating between 1968 and 2011. J Virol 2013; 88:2844-57. [PMID: 24371052 DOI: 10.1128/jvi.02163-13] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Influenza A(H3N2) viruses became widespread in humans during the 1968 H3N2 virus pandemic and have been a major cause of influenza epidemics ever since. These viruses evolve continuously by reassortment and genomic evolution. Antigenic drift is the cause for the need to update influenza vaccines frequently. Using two data sets that span the entire period of circulation of human influenza A(H3N2) viruses, it was shown that influenza A(H3N2) virus evolution can be mapped to 13 antigenic clusters. Here we analyzed the full genomes of 286 influenza A(H3N2) viruses from these two data sets to investigate the genomic evolution and reassortment patterns. Numerous reassortment events were found, scattered over the entire period of virus circulation, but most prominently in viruses circulating between 1991 and 1998. Some of these reassortment events persisted over time, and one of these coincided with an antigenic cluster transition. Furthermore, selection pressures and nucleotide and amino acid substitution rates of all proteins were studied, including those of the recently discovered PB1-N40, PA-X, PA-N155, and PA-N182 proteins. Rates of nucleotide and amino acid substitutions were most pronounced for the hemagglutinin, neuraminidase, and PB1-F2 proteins. Selection pressures were highest in hemagglutinin, neuraminidase, matrix 1, and nonstructural protein 1. This study of genotype in relation to antigenic phenotype throughout the period of circulation of human influenza A(H3N2) viruses leads to a better understanding of the evolution of these viruses. IMPORTANCE Each winter, influenza virus infects approximately 5 to 15% of the world's population, resulting in significant morbidity and mortality. Influenza A(H3N2) viruses evolve continuously by reassortment and genomic evolution. This leads to changes in antigenic recognition (antigenic drift) which make it necessary to update vaccines against influenza A(H3N2) viruses frequently. In this study, the relationship of genetic evolution to antigenic change spanning the entire period of A(H3N2) virus circulation was studied for the first time. The results presented in this study contribute to a better understanding of genetic evolution in correlation with antigenic evolution of influenza A(H3N2) viruses.
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Evsyukova I, Bradrick SS, Gregory SG, Garcia-Blanco MA. Cleavage and polyadenylation specificity factor 1 (CPSF1) regulates alternative splicing of interleukin 7 receptor (IL7R) exon 6. RNA (NEW YORK, N.Y.) 2013; 19:103-115. [PMID: 23151878 PMCID: PMC3527722 DOI: 10.1261/rna.035410.112] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 10/13/2012] [Indexed: 06/01/2023]
Abstract
Interleukin 7 receptor, IL7R, is expressed exclusively on cells of the lymphoid lineage, and its expression is crucial for the development and maintenance of T cells. Alternative splicing of IL7R exon 6 results in membrane-bound (exon 6 included) and soluble (exon 6 skipped) IL7R isoforms. Interestingly, the inclusion of exon 6 is affected by a single-nucleotide polymorphism associated with the risk of developing multiple sclerosis. Given the potential association of exon 6 inclusion with multiple sclerosis, we investigated the cis-acting elements and trans-acting factors that regulate exon 6 splicing. We identified multiple exonic and intronic cis-acting elements that impact inclusion of exon 6. Moreover, we utilized RNA affinity chromatography followed by mass spectrometry to identify trans-acting protein factors that bind exon 6 and regulate its splicing. These experiments identified cleavage and polyadenylation specificity factor 1 (CPSF1) among protein-binding candidates. A consensus polyadenylation signal AAUAAA is present in intron 6 of IL7R directly downstream from the 5' splice site. Mutations to this site and CPSF1 knockdown both resulted in an increase in exon 6 inclusion. We found no evidence that this site is used to produce cleaved and polyadenylated mRNAs, suggesting that CPSF1 interaction with intronic IL7R pre-mRNA interferes with spliceosome binding to the exon 6 5' splice site. Our results suggest that competing mRNA splicing and polyadenylation regulate exon 6 inclusion and consequently determine the ratios of soluble to membrane-bound IL7R. This may be relevant for both T cell ontogeny and function and development of multiple sclerosis.
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Affiliation(s)
| | | | - Simon G. Gregory
- Department of Molecular Genetics and Microbiology
- Center for Human Genetics, and
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
| | - Mariano A. Garcia-Blanco
- Center for RNA Biology
- Department of Molecular Genetics and Microbiology
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
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Melén K, Tynell J, Fagerlund R, Roussel P, Hernandez-Verdun D, Julkunen I. Influenza A H3N2 subtype virus NS1 protein targets into the nucleus and binds primarily via its C-terminal NLS2/NoLS to nucleolin and fibrillarin. Virol J 2012; 9:167. [PMID: 22909121 PMCID: PMC3493336 DOI: 10.1186/1743-422x-9-167] [Citation(s) in RCA: 39] [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: 05/16/2012] [Accepted: 08/08/2012] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Influenza A virus non-structural protein 1 (NS1) is a virulence factor, which is targeted into the cell cytoplasm, nucleus and nucleolus. NS1 is a multi-functional protein that inhibits host cell pre-mRNA processing and counteracts host cell antiviral responses. Previously, we have shown that the NS1 protein of the H3N2 subtype influenza viruses possesses a C-terminal nuclear localization signal (NLS) that also functions as a nucleolar localization signal (NoLS) and targets the protein into the nucleolus. RESULTS Here, we show that the NS1 protein of the human H3N2 virus subtype interacts in vitro primarily via its C-terminal NLS2/NoLS and to a minor extent via its N-terminal NLS1 with the nucleolar proteins, nucleolin and fibrillarin. Using chimeric green fluorescence protein (GFP)-NS1 fusion constructs, we show that the nucleolar retention of the NS1 protein is determined by its C-terminal NLS2/NoLS in vivo. Confocal laser microscopy analysis shows that the NS1 protein colocalizes with nucleolin in nucleoplasm and nucleolus and with B23 and fibrillarin in the nucleolus of influenza A/Udorn/72 virus-infected A549 cells. Since some viral proteins contain NoLSs, it is likely that viruses have evolved specific nucleolar functions. CONCLUSION NS1 protein of the human H3N2 virus interacts primarily via the C-terminal NLS2/NoLS and to a minor extent via the N-terminal NLS1 with the main nucleolar proteins, nucleolin, B23 and fibrillarin.
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Affiliation(s)
- Krister Melén
- Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), Mannerheimintie 166, FIN-00300, Helsinki, Finland
| | - Janne Tynell
- Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), Mannerheimintie 166, FIN-00300, Helsinki, Finland
| | - Riku Fagerlund
- Signaling Systems Laboratory, Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Pascal Roussel
- Functional Organization of the Nucleolus, RNA Biology-FRE 3402 CNRS, Université Pierre et Marie Curie, 75252, Paris cedex 5, France
| | - Danièle Hernandez-Verdun
- Nuclei and Cell Cycle, Institut Jacques Monod-UMR 7592 CNRS, Université Paris Diderot, 75205, Paris cedex 13, France
| | - Ilkka Julkunen
- Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), Mannerheimintie 166, FIN-00300, Helsinki, Finland
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Vickers TA, Crooke ST. siRNAs targeted to certain polyadenylation sites promote specific, RISC-independent degradation of messenger RNAs. Nucleic Acids Res 2012; 40:6223-34. [PMID: 22422842 PMCID: PMC3401429 DOI: 10.1093/nar/gks239] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
While most siRNAs induce sequence-specific target mRNA cleavage and degradation in a process mediated by Ago2/RNA-induced silencing complex (RISC), certain siRNAs have also been demonstrated to direct target RNA reduction through deadenylation and subsequent degradation of target transcripts in a process which involves Ago1/RISC and P-bodies. In the current study, we present data suggesting that a third class of siRNA exist, which are capable of promoting target RNA reduction that is independent of both Ago and RISC. These siRNAs bind the target messenger RNA at the polyA signal and are capable of redirecting a small amount of polyadenylation to downstream polyA sites when present, however, the majority of the activity appears to be due to inhibition of polyadenylation or deadenylation of the transcript, followed by exosomal degradation of the immature mRNA.
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Affiliation(s)
- Timothy A Vickers
- Department of Core Antisense Research, ISIS Pharmaceuticals, Inc. 2855 Gazelle Court, Carlsbad, CA 92010, USA.
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Identification of RNA helicase A as a cellular factor that interacts with influenza A virus NS1 protein and its role in the virus life cycle. J Virol 2011; 86:1942-54. [PMID: 22171255 DOI: 10.1128/jvi.06362-11] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Influenza A virus NS1 protein has multiple functions in the infected cell during the virus life cycle. Identification of novel cellular factors that interact with NS1 and understanding their functions in virus infection are of great interest. Recombinant viruses carrying a tagged NS1 are valuable for investigation of interactions between NS1 and cellular factors in the context of virus infection. Here, we report the generation of replication-competent recombinant influenza A viruses bearing a Strep tag in the NS1 protein. Purification of a protein complex associated with Strep-tagged NS1 from virus-infected cells followed by mass spectrometry revealed a number of attractive host factors. Among them, we focused our study on RNA helicase A (RHA) in this report. Through biomedical and functional analyses, we demonstrated that RHA interacts with NS1 in an RNA-dependent manner. Knockdown of RHA resulted in a significant reduction on virus yield and polymerase activity in a minigenome assay. Our cell-free viral genome replication assay showed that viral RNA replication and transcription can be enhanced by addition of RHA, and the enhanced effect of RHA required its ATP-dependent helicase activity. In summary, we established a system to identify cellular factors that interact with NS1 protein during virus infection and furthermore demonstrated that RHA interacts with NS1 and enhances viral replication and transcription.
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Bogoyavlenskiy A, Berezin V, Prilipov A, Korotetskiy I, Zaitseva I, Kydyrmanov A, Karamedin K, Ishmukhametova N, Asanova S, Sayatov M, Zhumatov K. Phylogenetic analysis of the non-structural (NS) gene of influenza A viruses isolated in Kazakhstan in 2002-2009. Virol Sin 2011; 26:376-85. [PMID: 22160937 DOI: 10.1007/s12250-011-3208-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 10/21/2011] [Indexed: 10/14/2022] Open
Abstract
Although the important role of the non-structural (NS1 and NEP) gene of influenza A in virulence of the virus is well established, our knowledge about the extent of variation in the NS gene pool of influenza A viruses in their natural reservoirs in Kazakhstan is incomplete. 17 influenza A viruses of different subtypes were studied in this paper. Seven types of haemagglutinin and five different neuraminidase subtypes in eight combinations were found among the isolated viruses. A comparison of nucleotide sequences of isolated viruses revealed a substantial number of silent mutations, which results in high degree of homology in amino acid sequences. By phylogenetic analysis it was shown that two distinct gene pools, corresponding to both NS allele A with 5 Clades and B, were present at the same time in Kazakhstan. The degree of variation within the alleles was very low. In our study allele A viruses had a maximum of 5% amino acid divergence in Clade while allele B viruses had only 4% amino acid divergence.
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Affiliation(s)
- Andrey Bogoyavlenskiy
- Institute of Microbiology & Virology, 103, Bogenbay batyr Str, Almaty 050010, Kazakhstan,
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Tu J, Guo J, Zhang A, Zhang W, Zhao Z, Zhou H, Liu C, Chen H, Jin M. Effects of the C-terminal truncation in NS1 protein of the 2009 pandemic H1N1 influenza virus on host gene expression. PLoS One 2011; 6:e26175. [PMID: 22022552 PMCID: PMC3192165 DOI: 10.1371/journal.pone.0026175] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 09/21/2011] [Indexed: 11/18/2022] Open
Abstract
The 2009 pandemic H1N1 influenza virus encodes an NS1 protein with 11 amino acids (aa) truncation at the C-terminus. The C-terminal tail of influenza virus NS1 protein constitutes a nucleolar localization signal (NoLS) and is the binding domain of the cellular pre-mRNA processing protein, poly(A)-binding protein II (PABII). Here, our studies showed that the C-terminal-truncated NS1 of the 2009 pandemic virus was inefficient at blocking host gene expression, extension of the truncated NS1 to its full length increased the inhibition of host gene expression. Mechanistically, this increased inhibition of host gene expression by the full-length NS1 was not associated with nucleolar localization, but was due to the restoration of NS1's binding capacity to PABII. Furthermore, in vitro and in vivo characterization of two recombinant viruses encoding either the C-terminal 11-aa truncated or full-length NS1 of the 2009 pandemic virus showed that the C-terminal 11-aa truncation in NS1 did not significantly alter virus replication, but increased virus pathogenicity in mice.
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Affiliation(s)
- Jiagang Tu
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Jing Guo
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Anding Zhang
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Wenting Zhang
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Zongzheng Zhao
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Hongbo Zhou
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Cheng Liu
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Huanchun Chen
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Meilin Jin
- Unit of Animal Infectious Diseases, National Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, People's Republic of China
- * E-mail:
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Munir M, Zohari S, Metreveli G, Baule C, Belák S, Berg M. Alleles A and B of non-structural protein 1 of avian influenza A viruses differentially inhibit beta interferon production in human and mink lung cells. J Gen Virol 2011; 92:2111-2121. [DOI: 10.1099/vir.0.031716-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Non-structural protein 1 (NS1) counteracts the production of host type I interferons (IFN-α/β) for the efficient replication and pathogenicity of influenza A viruses. Here, we reveal another dimension of the NS1 protein of avian influenza A viruses in suppressing IFN-β production in cultured cell lines. We found that allele A NS1 proteins of H6N8 and H4N6 have a strong capacity to inhibit the activation of IFN-β production, compared with allele B from corresponding subtypes, as measured by IFN stimulatory response element (ISRE) promoter activation, IFN-β mRNA transcription and IFN-β protein expression. Furthermore, the ability to suppress IFN-β promoter activation was mapped to the C-terminal effector domain (ED), while the RNA-binding domain (RBD) alone was unable to suppress IFN-β promoter activation. Chimeric studies indicated that when the RBD of allele A was fused to the ED of allele B, it was a strong inhibitor of IFN-β promoter activity. This shows that well-matched ED and RBD are crucial for the function of the NS1 protein and that the RBD could be one possible cause for this differential IFN-β inhibition. Notably, mutagenesis studies indicated that the F103Y and Y103F substitutions in alleles A and B, respectively, do not influence the ISRE promoter activation. Apart from dsRNA signalling, differences were observed in the expression pattern of NS1 in transfected human and mink lung cells. This study therefore expands the versatile nature of the NS1 protein in inhibiting IFN responses at multiple levels, by demonstrating for the first time that it occurs in a manner dependent on allele type.
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Affiliation(s)
- Muhammad Munir
- Department of Biomedical Sciences and Veterinary Public Health, Division of Virology, and Joint Research and Development, Department of Virology, Immunobiology and Parasitology of the National Veterinary Institute (SVA) and Swedish University of Agricultural Sciences (SLU), Ulls väg 2B, SE-751 89 Uppsala, Sweden
| | - Siamak Zohari
- R&D Unit for Virology, Department of Virology, Immunobiology and Parasitology of the National Veterinary Institute (SVA), Ulls väg 2B, SE-751 89 Uppsala, Sweden
- Department of Biomedical Sciences and Veterinary Public Health, Division of Virology, and Joint Research and Development, Department of Virology, Immunobiology and Parasitology of the National Veterinary Institute (SVA) and Swedish University of Agricultural Sciences (SLU), Ulls väg 2B, SE-751 89 Uppsala, Sweden
| | - Giorgi Metreveli
- Department of Biomedical Sciences and Veterinary Public Health, Division of Virology, and Joint Research and Development, Department of Virology, Immunobiology and Parasitology of the National Veterinary Institute (SVA) and Swedish University of Agricultural Sciences (SLU), Ulls väg 2B, SE-751 89 Uppsala, Sweden
| | - Claudia Baule
- R&D Unit for Virology, Department of Virology, Immunobiology and Parasitology of the National Veterinary Institute (SVA), Ulls väg 2B, SE-751 89 Uppsala, Sweden
| | - Sándor Belák
- R&D Unit for Virology, Department of Virology, Immunobiology and Parasitology of the National Veterinary Institute (SVA), Ulls väg 2B, SE-751 89 Uppsala, Sweden
- Department of Biomedical Sciences and Veterinary Public Health, Division of Virology, and Joint Research and Development, Department of Virology, Immunobiology and Parasitology of the National Veterinary Institute (SVA) and Swedish University of Agricultural Sciences (SLU), Ulls väg 2B, SE-751 89 Uppsala, Sweden
| | - Mikael Berg
- Department of Biomedical Sciences and Veterinary Public Health, Division of Virology, and Joint Research and Development, Department of Virology, Immunobiology and Parasitology of the National Veterinary Institute (SVA) and Swedish University of Agricultural Sciences (SLU), Ulls väg 2B, SE-751 89 Uppsala, Sweden
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37
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Idler RK, Yan W. Control of messenger RNA fate by RNA-binding proteins: an emphasis on mammalian spermatogenesis. ACTA ACUST UNITED AC 2011; 33:309-37. [PMID: 21757510 DOI: 10.2164/jandrol.111.014167] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Posttranscriptional status of messenger RNAs (mRNA) can be affected by many factors, most of which are RNA-binding proteins (RBP) that either bind mRNA in a nonspecific manner or through specific motifs, usually located in the 3' untranslated regions. RBPs can also be recruited by small noncoding RNAs (sncRNA), which have been shown to be involved in posttranscriptional regulations and transposon repression (eg, microRNAs or P-element-induced wimpy testis-interacting RNA) as components of the sncRNA effector complex. Non-sncRNA-binding RBPs have much more diverse effects on their target mRNAs. Some can cause degradation of their target transcripts and/or repression of translation, whereas others can stabilize and/or activate translation. The splicing and exportation of transcripts from the nucleus to the cytoplasm are often mediated by sequence-specific RBPs. The mechanisms by which RBPs regulate mRNA transcripts involve manipulating the 3' poly(A) tail, targeting the transcript to polysomes or to other ribonuclear protein particles, recruiting regulatory proteins, or competing with other RBPs. Here, we briefly review the known mechanisms of posttranscriptional regulation mediated by RBPs, with an emphasis on how these mechanisms might control spermatogenesis in general.
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Affiliation(s)
- R Keegan Idler
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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Zohari S, Munir M, Metreveli G, Belák S, Berg M. Differences in the ability to suppress interferon β production between allele A and allele B NS1 proteins from H10 influenza A viruses. Virol J 2010; 7:376. [PMID: 21194454 PMCID: PMC3022685 DOI: 10.1186/1743-422x-7-376] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Accepted: 12/31/2010] [Indexed: 12/25/2022] Open
Abstract
Background In our previous study concerning the genetic relationship among H10 avian influenza viruses with different pathogenicity in mink (Mustela vison), we found that these differences were related to amino acid variations in the NS1 protein. In this study, we extend our previous work to further investigate the effect of the NS1 from different gene pools on type I IFN promoter activity, the production of IFN-β, as well as the expression of the IFN-β mRNA in response to poly I:C. Results Using a model system, we first demonstrated that NS1 from A/mink/Sweden/84 (H10N4) (allele A) could suppress an interferon-stimulated response element (ISRE) reporter system to about 85%. The other NS1 (allele B), from A/chicken/Germany/N/49 (H10N7), was also able to suppress the reporter system, but only to about 20%. The differences in the abilities of the two NS1s from different alleles to suppress the ISRE reporter system were clearly reflected by the protein and mRNA expressions of IFN-β as shown by ELISA and RT-PCR assays. Conclusions These studies reveal that different non-structural protein 1 (NS1) of influenza viruses, one from allele A and another from allele B, show different abilities to suppress the type I interferon β expression. It has been hypothesised that some of the differences in the different abilities of the alleles to suppress ISRE were because of the interactions and inhibitions at later stages from the IFN receptor, such as the JAK/STAT pathway. This might reflect the additional effects of the immune evasion potential of different NS1s.
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Affiliation(s)
- Siamak Zohari
- Swedish University of Agricultural Sciences (SLU), Department of Biomedical Sciences and Veterinary Public Health, Section of Virology, SLU, Ulls Väg 2B, SE-75189 Uppsala, Sweden.
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39
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Martinson HG. An active role for splicing in 3′-end formation. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 2:459-70. [DOI: 10.1002/wrna.68] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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40
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Han H, Cui ZQ, Wang W, Zhang ZP, Wei HP, Zhou YF, Zhang XE. New regulatory mechanisms for the intracellular localization and trafficking of influenza A virus NS1 protein revealed by comparative analysis of A/PR/8/34 and A/Sydney/5/97. J Gen Virol 2010; 91:2907-17. [PMID: 20826615 DOI: 10.1099/vir.0.024943-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During influenza A virus infection, the NS1 protein is engaged in different functions in different intracellular compartments. In this study, we showed that the NS1 of A/PR/8/34 localized in different positions from that of A/Sydney/5/97 when transiently expressed in Madin-Darby canine kidney cells. Residue 221 of NS1 was identified to be a new key residue involved in the C-terminal nuclear localization signal (NLS) and nucleolar localization signal (NoLS) of NS1 from A/Sydney/5/97. Analysis of chimeric NS1 and further mutants showed that residues responsible for the binding between NS1 and the cleavage and polyadenylation specificity factor (CPSF) are correlated with the intracellular localization of transiently expressed NS1 proteins. Fluorescence loss in photobleaching imaging revealed that the NS1 protein with both functional NLSs and nuclear export signal (NES) was able to shuttle between the nucleus and cytoplasm. Drug inhibition experiments and fluorescence resonance energy transfer analysis suggested that NS1 was exported out of the cell nuclei via a Crm1-independent pathway. Moreover, it is likely that another cytoplasmic localization-related sequence exists in the NS1 protein other than the leucine-rich NES. These findings provide new insights into the mechanism of intracellular localization and trafficking of influenza A virus NS1 protein, which is important for understanding its function.
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Affiliation(s)
- Han Han
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences Wuhan 430071, PR China
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41
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Molecular characterization and comparative analysis of pandemic H1N1/2009 strains with co-circulating seasonal H1N1/2009 strains from eastern India. Arch Virol 2010; 156:207-17. [PMID: 20981560 DOI: 10.1007/s00705-010-0842-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Accepted: 10/15/2010] [Indexed: 10/18/2022]
Abstract
During the peak outbreak (July-September 2009), a total 1886 patients were screened in eastern India, of which 139 (7.37%) and 52 (2.76%) were positive for pH1N1 and seasonal H1N1, respectively. Full-length HA1, NA, NS1 and PB1-F2 genes of representative strains were sequenced. Phylogenetic analysis of deduced amino acid sequences of pH1N1 strains revealed HA1 and NS1 to be of North American swine lineage, and the NA gene of Eurasian swine lineage. Consistent with previous reports, the PB1-F2 gene of pH1N1 strains was unique due to a mutation resulting in a truncated protein of 11 aa. The HA, NA and NS1 genes of H1N1/2009 strains clustered with H1N1 strains of 2000-2009, whereas a subset of strains contained a pH1N1-like truncated PB1-F2. The truncated PB1-F2 may confer the advantage of lower pathogenicity but higher replication and infectivity to the human H1N1 strains. This is the first report of seasonal H1N1/2009 strains with a pH1N1/2009-like gene segment.
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NS reassortment of an H7-type highly pathogenic avian influenza virus affects its propagation by altering the regulation of viral RNA production and antiviral host response. J Virol 2010; 84:11323-35. [PMID: 20739516 DOI: 10.1128/jvi.01034-10] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Highly pathogenic avian influenza viruses (HPAIV) with reassorted NS segments from H5- and H7-type avian virus strains placed in the genetic background of the A/FPV/Rostock/34 HPAIV (FPV; H7N1) were generated by reverse genetics. Virological characterizations demonstrated that the growth kinetics of the reassortant viruses differed from that of wild-type (wt) FPV and depended on whether cells were of mammalian or avian origin. Surprisingly, molecular analysis revealed that the different reassortant NS segments were not only responsible for alterations in the antiviral host response but also affected viral genome replication and transcription as well as nuclear ribonucleoprotein (RNP) export. RNP reconstitution experiments demonstrated that the effects on accumulation levels of viral RNA species were dependent on the specific NS segment as well as on the genetic background of the RNA-dependent RNA polymerase (RdRp). Beta interferon (IFN-β) expression and the induction of apoptosis were found to be inversely correlated with the magnitude of viral growth, while the NS allele, virus subtype, and nonstructural protein NS1 expression levels showed no correlation. Thus, these results demonstrate that the origin of the NS segment can have a dramatic effect on the replication efficiency and host range of HPAIV. Overall, our data suggest that the propagation of NS reassortant influenza viruses is affected at multiple steps of the viral life cycle as a result of the different effects of the NS1 protein on multiple viral and host functions.
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43
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Shepherd A, Wesley U, Wesley C. Notch and delta mRNAs in early-stage and mid-stage drosophila embryos exhibit complementary patterns of protein-producing potentials. Dev Dyn 2010; 239:1220-33. [PMID: 20201103 DOI: 10.1002/dvdy.22262] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Notch and Delta proteins generate Notch signaling that specifies cell fates during animal development. There is an intriguing phenomenon in Drosophila embryogenesis that has not received much attention and whose significance to embryogenesis is unknown. Notch and Delta mRNAs expressed in early-stage embryos are shorter than their counterparts in mid-stage embryos. We show here that the difference in sizes is due to mRNA 3' processing at alternate polyadenylation sites. While the early-stage Notch mRNA has a lower protein-producing potential than the mid-stage Notch mRNA, the early-stage Delta mRNA has a higher protein-producing potential than the mid-stage Delta mRNA. Our data can explain the complementary patterns of Notch and Delta protein levels in early- and mid-stage embryos. Our data also raise the possibility that the manner and regulation of Notch signaling change in the course of embryogenesis and that this change is effected by 3' UTR and mRNA 3' processing factors.
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Affiliation(s)
- Andrew Shepherd
- Department of Biology, University of Vermont, Burlington, Vermont 05405, USA
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44
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Zohari S, Metreveli G, Kiss I, Belák S, Berg M. Full genome comparison and characterization of avian H10 viruses with different pathogenicity in Mink (Mustela vison) reveals genetic and functional differences in the non-structural gene. Virol J 2010; 7:145. [PMID: 20591155 PMCID: PMC2909961 DOI: 10.1186/1743-422x-7-145] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 06/30/2010] [Indexed: 01/14/2023] Open
Abstract
Background The unique property of some avian H10 viruses, particularly the ability to cause severe disease in mink without prior adaptation, enabled our study. Coupled with previous experimental data and genetic characterization here we tried to investigate the possible influence of different genes on the virulence of these H10 avian influenza viruses in mink. Results Phylogenetic analysis revealed a close relationship between the viruses studied. Our study also showed that there are no genetic differences in receptor specificity or the cleavability of the haemagglutinin proteins of these viruses regardless of whether they are of low or high pathogenicity in mink. In poly I:C stimulated mink lung cells the NS1 protein of influenza A virus showing high pathogenicity in mink down regulated the type I interferon promoter activity to a greater extent than the NS1 protein of the virus showing low pathogenicity in mink. Conclusions Differences in pathogenicity and virulence in mink between these strains could be related to clear amino acid differences in the non structural 1 (NS1) protein. The NS gene of mink/84 appears to have contributed to the virulence of the virus in mink by helping the virus evade the innate immune responses.
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Affiliation(s)
- Siamak Zohari
- Swedish University of Agricultural Sciences (SLU), Department of Biomedical Sciences and Public Health, Section of Virology, SLU, SE-751 89 Uppsala, Sweden.
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Toledo JS, Ferreira TR, Defina TPA, Dossin FDM, Beattie KA, Lamont DJ, Cloutier S, Papadopoulou B, Schenkman S, Cruz AK. Cell homeostasis in a Leishmania major mutant overexpressing the spliced leader RNA is maintained by an increased proteolytic activity. Int J Biochem Cell Biol 2010; 42:1661-71. [PMID: 20601086 DOI: 10.1016/j.biocel.2010.06.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Revised: 06/04/2010] [Accepted: 06/16/2010] [Indexed: 10/19/2022]
Abstract
Although several stage-specific genes have been identified in Leishmania, the molecular mechanisms governing developmental gene regulation in this organism are still not well understood. We have previously reported an attenuation of virulence in Leishmania major and L. braziliensis carrying extra-copies of the spliced leader RNA gene. Here, we surveyed the major differences in proteome and transcript expression profiles between the spliced leader RNA overexpressor and control lines using two-dimensional gel electrophoresis and differential display reverse transcription PCR, respectively. Thirty-nine genes related to stress response, cytoskeleton, proteolysis, cell cycle control and proliferation, energy generation, gene transcription, RNA processing and post-transcriptional regulation have abnormal patterns of expression in the spliced leader RNA overexpressor line. The evaluation of proteolytic pathways in the mutant revealed a selective increase of cysteine protease activity and an exacerbated ubiquitin-labeled protein population. Polysome profile analysis and measurement of cellular protein aggregates showed that protein translation in the spliced leader RNA overexpressor line is increased when compared to the control line. We found that L. major promastigotes maintain homeostasis in culture when challenged with a metabolic imbalance generated by spliced leader RNA surplus through modulation of intracellular proteolysis. However, this might interfere with a fine-tuned gene expression control necessary for the amastigote multiplication in the mammalian host.
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Affiliation(s)
- Juliano S Toledo
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade Medicina de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
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Robb NC, Jackson D, Vreede FT, Fodor E. Splicing of influenza A virus NS1 mRNA is independent of the viral NS1 protein. J Gen Virol 2010; 91:2331-40. [PMID: 20519456 DOI: 10.1099/vir.0.022004-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
RNA segment 8 (NS) of influenza A virus encodes two proteins. The NS1 protein is translated from the unspliced primary mRNA transcript, whereas the second protein encoded by this segment, NS2/NEP, is translated from a spliced mRNA. Splicing of influenza NS1 mRNA is thought to be regulated so that the levels of NS2 spliced transcripts are approximately 10 % of total NS mRNA. Regulation of splicing of the NS1 mRNA has been studied at length, and a number of often-contradictory control mechanisms have been proposed. In this study, we used (32)P-labelled gene-specific primers to investigate influenza A NS1 mRNA splicing regulation. It was found that the efficiency of splicing of NS1 mRNA was maintained at similar levels in both virus infection and ribonucleoprotein-reconstitution assays, and NS2 mRNA comprised approximately 15 % of total NS mRNA in both assays. The effect of NS1 protein expression on the accumulation of viral NS2 mRNA and spliced cellular beta-globin mRNA was analysed, and it was found that NS1 protein expression reduced spliced beta-globin mRNA levels, but had no effect on the accumulation of NS2 mRNA. We conclude that the NS1 protein specifically inhibits the accumulation of cellular RNA polymerase II-driven mRNAs, but does not affect the splicing of its own viral NS1 mRNA.
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Affiliation(s)
- Nicole C Robb
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
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Genetically engineered, biarsenically labeled influenza virus allows visualization of viral NS1 protein in living cells. J Virol 2010; 84:7204-13. [PMID: 20463066 DOI: 10.1128/jvi.00203-10] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Real-time fluorescence imaging of viral proteins in living cells provides a valuable means to study virus-host interactions. The challenge of generating replication-competent fluorescent influenza A virus is that the segmented genome does not allow fusion of a fluorescent protein gene to any viral gene. Here, we introduced the tetracysteine (TC) biarsenical labeling system into influenza virus in order to fluorescently label viral protein in the virus life cycle. We generated infectious influenza A viruses bearing a small TC tag (CCPGCC) in the loop/linker regions of the NS1 proteins. In the background of A/Puerto Rico/8/34 (H1N1) (PR8) virus, the TC tag can be inserted into NS1 after amino acid 52 (AA52) (PR8-410), AA79 (PR8-412), or AA102 (PR8-413) or the TC tag can be inserted and replace amino acids 79 to 84 (AA79-84) (PR8-411). Although PR8-410, PR8-411, and PR8-412 viruses are attenuated than the wild-type (WT) virus to some extent in multiple-cycle infection, their growth potential is similar to that of the WT virus during a single cycle of infection, and their NS1 subcellular localization and viral protein synthesis rate are quite similar to those of the WT virus. Furthermore, labeling with membrane-permeable biarsenical dye resulted in fluorescent NS1 protein in the context of virus infection. We could exploit this strategy on NS1 protein of A/Texas/36/91 (H1N1) (Tx91) by successfully rescuing a TC-tagged virus, Tx91-445, which carries the TC tag replacement of AA79-84. The infectivity of Tx91-445 virus was similar to that of WT Tx91 during multiple cycles of replication and a single cycle of replication. The NS1 protein derived from Tx91-445 can be fluorescently labeled in living cells. Finally, with biarsenical labeling, the engineered replication-competent virus allowed us to visualize NS1 protein nuclear import in virus-infected cells in real time.
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Inefficient control of host gene expression by the 2009 pandemic H1N1 influenza A virus NS1 protein. J Virol 2010; 84:6909-22. [PMID: 20444891 DOI: 10.1128/jvi.00081-10] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In 2009, a novel swine-origin H1N1 influenza A virus emerged. Here, we characterize the multifunctional NS1 protein of this human pandemic virus in order to understand factors that may contribute to replication efficiency or pathogenicity. Although the 2009 H1N1 virus NS1 protein (2009/NS1) is an effective interferon antagonist, we found that this NS1 (unlike those of previous human-adapted influenza A viruses) is unable to block general host gene expression in human or swine cells. This property could be restored in 2009/NS1 by replacing R108, E125, and G189 with residues corresponding to human virus consensus. Mechanistically, these previously undescribed mutations acted by increasing binding of 2009/NS1 to the cellular pre-mRNA processing protein CPSF30. A recombinant 2009 H1N1 influenza A virus (A/California/04/09) expressing NS1 with these gain-of-function substitutions was more efficient than the wild type at antagonizing host innate immune responses in primary human epithelial cells. However, such mutations had no significant effect on virus replication in either human or swine tissue culture substrates. Surprisingly, in a mouse model of pathogenicity, the mutant virus appeared to cause less morbidity, and was cleared faster, than the wild type. The mutant virus also demonstrated reduced titers in the upper respiratory tracts of ferrets; however, contact and aerosol transmissibility of the virus was unaffected. Our data highlight a potential human adaptation of NS1 that seems absent in "classically derived" swine-origin influenza A viruses, including the 2009 H1N1 virus. We discuss the impact that a natural future gain of this NS1 function may have on the new pandemic virus in humans.
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Hale BG, Steel J, Manicassamy B, Medina RA, Ye J, Hickman D, Lowen AC, Perez DR, García-Sastre A. Mutations in the NS1 C-terminal tail do not enhance replication or virulence of the 2009 pandemic H1N1 influenza A virus. J Gen Virol 2010; 91:1737-42. [PMID: 20237225 PMCID: PMC3052525 DOI: 10.1099/vir.0.020925-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The 'classical' swine H1N1 influenza A virus lineage was established after the devastating 1918 human pandemic virus entered domestic pig herds. A descendent of this lineage recently re-emerged in humans as the 2009 pandemic H1N1 virus. Adaptation in pigs has led to several changes in the multifunctional viral NS1 protein as compared with the parental 1918 virus, most notably a K217E substitution that abolishes binding to host Crk/CrkL signalling adapters, and an 11 aa C-terminal truncation. Using reverse genetics, we reintroduced both these features into a prototype 2009 H1N1 strain, A/California/04/09. Restoration of Crk/CrkL binding or extension of NS1 to 230 aa had no impact on virus replication in human or swine cells. In addition, minimal effects on replication, pathogenicity and transmission were observed in mouse and ferret models. Our data suggest that the currently circulating 2009 H1N1 virus is optimized to replicate efficiently without requiring certain NS1 functions.
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Affiliation(s)
- Benjamin G Hale
- Department of Microbiology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA
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Abstract
Influenza viruses are globally important human respiratory pathogens. These viruses cause seasonal epidemics and occasional worldwide pandemics, both of which can vary significantly in disease severity. The virulence of a particular influenza virus strain is partly determined by its success in circumventing the host immune response. This article briefly reviews the innate mechanisms that host cells have evolved to resist virus infection, and outlines the plethora of strategies that influenza viruses have developed in order to counteract such powerful defences. The molecular details of this virus-host interplay are summarized, and the ways in which research in this area is being applied to the rational design of protective vaccines and novel antivirals are discussed.
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Affiliation(s)
- Benjamin G Hale
- Department of Microbiology, Mount Sinai School of Medicine, One Gustave L Levy Place, New York, NY 10029, USA, Tel.: +1 212 241 5732, Fax: +1 212 534 1684,
| | - Randy A Albrecht
- Department of Microbiology, Mount Sinai School of Medicine, One Gustave L Levy Place, New York, NY 10029, USA, Tel.: +1 212 241 8255, Fax: +1 212 534 1684,
| | - Adolfo García-Sastre
- Department of Microbiology, Department of Medicine and Global Health & Emerging Pathogens Institute, Mount Sinai School of Medicine, One Gustave L Levy Place, New York, NY 10029, USA, Tel.: +1 212 241 7769, Fax: +1 212 534 1684,
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