The NS1 influenza protein (NS1) is a viral nonstructural protein encoded by the NS gene segments of type A, B and Cinfluenza viruses. Also encoded by this segment is the nuclear export protein (NEP), formally referred to as NS2 protein, which mediates the export of influenza virus ribonucleoprotein (RNP) complexes from the nucleus, where they are assembled.[1][2]
Dimer of the Influenzavirus A non-structural protein 1 from A/Vietnam/1203/2004(H5N1)
The NS1 of influenza A virus is a 26,000 Dalton protein. It prevents polyadenylation of cellular mRNAs to circumvent antiviral responses of the host, e.g., maturation and translation of interferon mRNAs. NS1 might also inhibit splicing of pre-mRNA by binding to a stem-bulge region in U6 small nuclear RNA (snRNA).[3] In addition, NS1 is probably able to suppress the interferon response in the virus-infected cell leading to unimpaired virus production.[4]
NS1 also binds dsRNA. Binding assays with NS1 protein mutants established that the RNA-binding domain of the NS1 protein is required for binding to dsRNA as well as for binding to polyA and U6 snRNA. In addition, dsRNA competed with U6 snRNA for binding to the NS1 protein, a result consistent with both RNAs sharing the same binding site on the protein. As a consequence of its binding to dsRNA, the NS1 protein blocks the activation of the dsRNA-activated protein kinase (PKR) in vitro. This kinase phosphorylates the alpha subunit of eukaryotic translation initiation factor 2 (elF-2 alpha), leading to a decrease in the rate of initiation of translation.[3] In the absence of NS1, this pathway is inhibited during anti-viral response to halt all protein translation – thus stopping the synthesis of viral proteins; however, the influenza virus' NS1 protein is an agent that circumvents host defenses to allows viral gene transcription to occur.
The NS1 protein can be divided into an N terminal (RNA binding) domain and C terminal (effector domain). The RNA binding domain is able to target RIG-I, and therefore prevent the activation of induction of interferon responses. At the effector domain, it interacts and inhibits cleavage and polyadenylation specificity factor (CPSF30). CPSF30 is part of processing pathway for cellular mRNAs, and its inhibition leads to inability of the cellular mRNA to be exported outside the nucleus for translation, thereby hindering the ability of host cell to produce Interferon-stimulated genes.[5]
Avianedit
The NS1 protein of the highly pathogenic avian H5N1 viruses circulating in poultry and waterfowl in Southeast Asia is currently believed to be responsible for the enhanced virulence of the strain. H5N1 NS1 is characterized by a single amino acid change at position 92. By changing the amino acid from glutamic acid to aspartic acid, researchers were able to annul the effect of the H5N1 NS1. This single amino acid change in the NS1 gene greatly increased the pathogenicity of the H5N1 influenza virus.[6] However, the effect of residue 92 on the function of H5N1 NS1 appears to be questionable as noted by Nature Medicine editors:
The above paper originally reported that H5N1 viruses are resistant to interferon in the SJPL cell line.[6] The editors wish to alert our readers about three facts that may affect this conclusion. First, Ngunjiri et al.[7] have recently found that aliquots of the SJPL cell line obtained from the American Type Culture Collection were heavily contaminated with mycoplasma. Although the mycoplasma status of the cells used in the original paper is unknown, it is not possible to rule out that they were contaminated. Second, SJPL cells were originally reported to be of porcine origin, but a recent analysis[8] has indicated that they are of simian origin. Third, Ngunjiri et al.[7] have found H5N1 viruses to be sensitive to interferons in all cell lines tested from multiple species.[9]
Pathogenicityedit
The fact that NS1 is involved in the pathogenicity of influenza A viruses makes it a good target to attenuate these viruses. Several studies demonstrated that influenza viruses with partial deletions in NS1 proteins are attenuated and do not cause disease, but induce a protective immune response in different species including mice,[10][11] pigs,[12][13] horses,[14] birds[15] and macaques.[16] Although it had been known for more than a decade that influenza viruses with partial deletions in NS1 proteins were attenuated, all but one[17] NS1 truncation variants of influenza A viruses were generated by in vitro mutagenesis. Wang et al. later demonstrated that the naturally truncated variant [17] had propensity to generate new variants when passaged in ovo.[18] Remarkably, the new variants were excellent live-attenuated influenza vaccine candidates.[18] The ability to attenuate influenza viruses by truncation of the NS1 protein presents a novel approach in design and development of the next generation live-attenuated influenza vaccines for both poultry and humans.
^Influenza B and C Virus NEP (NS2) Proteins Possess Nuclear Export Activities Journal of Virology, August 2001, p. 7375-7383, Vol. 75, No. 16
^O'Neill RE, Talon J, Palese P (1998). "The influenza virus NEP (NS2 protein) mediates the nuclear export of viral ribonucleoproteins". EMBO J. 17 (1): 288–296. doi:10.1093/emboj/17.1.288. PMC1170379. PMID 9427762.
^ abLu, Y et al., 1995. Binding of the influenza virus NS1 protein to double-stranded RNA inhibits the activation of the protein kinase that phosphorylates the elF-2 translation initiation factor. Virology. 1995 Dec 1;214(1):222-8.
^Kumar KU, Srivastava SP, Kaufman RJ (February 1999). "Double-stranded RNA-activated protein kinase (PKR) is negatively regulated by 60S ribosomal subunit protein L18". Mol Cell Biol. 19 (2): 1116–25. doi:10.1128/mcb.19.2.1116. PMC116041. PMID 9891046.
^Hale BG1, Randall RE, Ortín J, Jackson D (2008). "The multifunctional NS1 protein of influenza A viruses". J Gen Virol. 89 (10): 2359–76. doi:10.1099/vir.0.2008/004606-0. hdl:10023/3001. PMID 18796704.
^ abNgunjiri JM, Mohni KN, Sekellick MJ, Schultz-Cherry S, Webster RG, Marcus PI (2012). "Lethal H5N1 influenza viruses are not resistant to interferon action in human, simian, porcine or chicken cells". Nature Medicine. 18 (10): 1456–1457. doi:10.1038/nm.2879. PMID 23042343. S2CID 205389804.
^Silversides DW, Music N, Jacques M, Gagnon CA, Webby R (2010). "Investigation of the species origin of the St. Jude Porcine Lung epithelial cell line (SJPL) made available to researchers". J. Virol. 84 (10): 5454–5. doi:10.1128/jvi.00042-10. PMC2863845. PMID 20200241.
^Hai R, Martinez-Sobrido L, Fraser KA, Ayllon J, Garcia-Sastre A, Palese P (2008). "Influenza B virus NS1-truncated mutants: live-attenuated vaccine approach". J Virol. 82 (21): 10580–10590. doi:10.1128/jvi.01213-08. PMC2573209. PMID 18768976.
^Talon J, Salvatore M, O'Neill RE, Nakaya Y, Zheng H, Muster T, Garcia-Sastre A, Palese P (2000). "Influenza A and B viruses expressing altered NS1 proteins: A vaccine approach". Proc Natl Acad Sci U S A. 97 (8): 4309–4314. Bibcode:2000PNAS...97.4309T. doi:10.1073/pnas.070525997. PMC18238. PMID 10725408.
^Solorzano A, Webby RJ, Lager KM, Janke BH, Garcia-Sastre A, Richt JA (2005). "Mutations in the NS1 protein of swine influenza virus impair anti-interferon activity and confer attenuation in pigs". J Virol. 79 (12): 7535–7543. doi:10.1128/jvi.79.12.7535-7543.2005. PMC1143661. PMID 15919908.
^Vincent AL, Ma W, Lager KM, Janke BH, Webby RJ, Garcia-Sastre A, Richt JA (2007). "Efficacy of intranasal administration of a truncated NS1 modified live influenza virus vaccine in swine". Vaccine. 25 (47): 7999–8009. doi:10.1016/j.vaccine.2007.09.019. PMC2099695. PMID 17933442.
^Quinlivan M, Zamarin D, Garcia-Sastre A, Cullinane A, Chambers T, Palese P (2005). "Attenuation of equine influenza viruses through truncations of the NS1 protein". J Virol. 79 (13): 8431–8439. doi:10.1128/jvi.79.13.8431-8439.2005. PMC1143746. PMID 15956587.
^Steel J, Lowen AC, Pena L, Angel M, Solorzano A, Albrecht R, Perez DR, Garcia-Sastre A, Palese P (2009). "Live attenuated influenza viruses containing NS1 truncations as vaccine candidates against H5N1 highly pathogenic avian influenza". Journal of Virology. 83 (4): 1742–1753. doi:10.1128/jvi.01920-08. PMC2643794. PMID 19073731.
^Baskin CR, Bielefeldt-Ohmann H, Garcia-Sastre A, Tumpey TM, Hoeven N Van, Carter VS, Thomas MJ, Proll S, Solorzano A, Billharz R, Fornek JL, Thomas S, Chen CH, Clark EA, Murali-Krishna K, Katze MG (2007). "Functional genomic and serological analysis of the protective immune response resulting from vaccination of macaques with an NS1-truncated influenza virus". J Virol. 81 (21): 11817–11827. doi:10.1128/jvi.00590-07. PMC2168783. PMID 17715226.
^ abGarcía-Sastre A, Egorov A, Matassov D, Brandt S, Levy DE, Durbin JE, Palese P, Muster T (1998). "Influenza A virus lacking the NS1 gene replicates in interferon-deficient systems". Virology. 252 (2): 324–30. doi:10.1006/viro.1998.9508. PMID 9878611.
^ abWang L, Suarez DL, Pantin-Jackwood M, Mibayashi M, García-Sastre A, Saif YM, Lee CW (2008). "Characterization of Influenza Virus Variants with Different Sizes of the Non-structural (NS) Genes and Their Potential as a Live Influenza Vaccine in Poultry". Vaccine. 26 (29–30): 3580–3586. doi:10.1016/j.vaccine.2008.05.001. PMC2785844. PMID 18539366.
External linksedit
NCBI Flu Genome Database
January 01, 1970
influenza, protein, viral, nonstructural, protein, encoded, gene, segments, type, influenza, viruses, also, encoded, this, segment, nuclear, export, protein, formally, referred, protein, which, mediates, export, influenza, virus, ribonucleoprotein, complexes, . The NS1 influenza protein NS1 is a viral nonstructural protein encoded by the NS gene segments of type A B and C influenza viruses Also encoded by this segment is the nuclear export protein NEP formally referred to as NS2 protein which mediates the export of influenza virus ribonucleoprotein RNP complexes from the nucleus where they are assembled 1 2 Dimer of the Influenzavirus A non structural protein 1 from A Vietnam 1203 2004 H5N1 Contents 1 Characteristics 2 Avian 3 Pathogenicity 4 See also 5 References 6 External linksCharacteristics editThe NS1 of influenza A virus is a 26 000 Dalton protein It prevents polyadenylation of cellular mRNAs to circumvent antiviral responses of the host e g maturation and translation of interferon mRNAs NS1 might also inhibit splicing of pre mRNA by binding to a stem bulge region in U6 small nuclear RNA snRNA 3 In addition NS1 is probably able to suppress the interferon response in the virus infected cell leading to unimpaired virus production 4 NS1 also binds dsRNA Binding assays with NS1 protein mutants established that the RNA binding domain of the NS1 protein is required for binding to dsRNA as well as for binding to polyA and U6 snRNA In addition dsRNA competed with U6 snRNA for binding to the NS1 protein a result consistent with both RNAs sharing the same binding site on the protein As a consequence of its binding to dsRNA the NS1 protein blocks the activation of the dsRNA activated protein kinase PKR in vitro This kinase phosphorylates the alpha subunit of eukaryotic translation initiation factor 2 elF 2 alpha leading to a decrease in the rate of initiation of translation 3 In the absence of NS1 this pathway is inhibited during anti viral response to halt all protein translation thus stopping the synthesis of viral proteins however the influenza virus NS1 protein is an agent that circumvents host defenses to allows viral gene transcription to occur The NS1 protein can be divided into an N terminal RNA binding domain and C terminal effector domain The RNA binding domain is able to target RIG I and therefore prevent the activation of induction of interferon responses At the effector domain it interacts and inhibits cleavage and polyadenylation specificity factor CPSF30 CPSF30 is part of processing pathway for cellular mRNAs and its inhibition leads to inability of the cellular mRNA to be exported outside the nucleus for translation thereby hindering the ability of host cell to produce Interferon stimulated genes 5 Avian editThe NS1 protein of the highly pathogenic avian H5N1 viruses circulating in poultry and waterfowl in Southeast Asia is currently believed to be responsible for the enhanced virulence of the strain H5N1 NS1 is characterized by a single amino acid change at position 92 By changing the amino acid from glutamic acid to aspartic acid researchers were able to annul the effect of the H5N1 NS1 This single amino acid change in the NS1 gene greatly increased the pathogenicity of the H5N1 influenza virus 6 However the effect of residue 92 on the function of H5N1 NS1 appears to be questionable as noted by Nature Medicine editors The above paper originally reported that H5N1 viruses are resistant to interferon in the SJPL cell line 6 The editors wish to alert our readers about three facts that may affect this conclusion First Ngunjiri et al 7 have recently found that aliquots of the SJPL cell line obtained from the American Type Culture Collection were heavily contaminated with mycoplasma Although the mycoplasma status of the cells used in the original paper is unknown it is not possible to rule out that they were contaminated Second SJPL cells were originally reported to be of porcine origin but a recent analysis 8 has indicated that they are of simian origin Third Ngunjiri et al 7 have found H5N1 viruses to be sensitive to interferons in all cell lines tested from multiple species 9 Pathogenicity editThe fact that NS1 is involved in the pathogenicity of influenza A viruses makes it a good target to attenuate these viruses Several studies demonstrated that influenza viruses with partial deletions in NS1 proteins are attenuated and do not cause disease but induce a protective immune response in different species including mice 10 11 pigs 12 13 horses 14 birds 15 and macaques 16 Although it had been known for more than a decade that influenza viruses with partial deletions in NS1 proteins were attenuated all but one 17 NS1 truncation variants of influenza A viruses were generated by in vitro mutagenesis Wang et al later demonstrated that the naturally truncated variant 17 had propensity to generate new variants when passaged in ovo 18 Remarkably the new variants were excellent live attenuated influenza vaccine candidates 18 The ability to attenuate influenza viruses by truncation of the NS1 protein presents a novel approach in design and development of the next generation live attenuated influenza vaccines for both poultry and humans See also editH5N1 genetic structureReferences edit Influenza B and C Virus NEP NS2 Proteins Possess Nuclear Export Activities Journal of Virology August 2001 p 7375 7383 Vol 75 No 16 O Neill RE Talon J Palese P 1998 The influenza virus NEP NS2 protein mediates the nuclear export of viral ribonucleoproteins EMBO J 17 1 288 296 doi 10 1093 emboj 17 1 288 PMC 1170379 PMID 9427762 a b Lu Y et al 1995 Binding of the influenza virus NS1 protein to double stranded RNA inhibits the activation of the protein kinase that phosphorylates the elF 2 translation initiation factor Virology 1995 Dec 1 214 1 222 8 Kumar KU Srivastava SP Kaufman RJ February 1999 Double stranded RNA activated protein kinase PKR is negatively regulated by 60S ribosomal subunit protein L18 Mol Cell Biol 19 2 1116 25 doi 10 1128 mcb 19 2 1116 PMC 116041 PMID 9891046 Hale BG1 Randall RE Ortin J Jackson D 2008 The multifunctional NS1 protein of influenza A viruses J Gen Virol 89 10 2359 76 doi 10 1099 vir 0 2008 004606 0 hdl 10023 3001 PMID 18796704 a b Seo SH Hoffmann E Webster RG 2002 Lethal H5N1 influenza viruses escape host anti viral cytokine responses Nat Med 8 9 950 4 doi 10 1038 nm757 PMID 12195436 S2CID 8293109 a b Ngunjiri JM Mohni KN Sekellick MJ Schultz Cherry S Webster RG Marcus PI 2012 Lethal H5N1 influenza viruses are not resistant to interferon action in human simian porcine or chicken cells Nature Medicine 18 10 1456 1457 doi 10 1038 nm 2879 PMID 23042343 S2CID 205389804 Silversides DW Music N Jacques M Gagnon CA Webby R 2010 Investigation of the species origin of the St Jude Porcine Lung epithelial cell line SJPL made available to researchers J Virol 84 10 5454 5 doi 10 1128 jvi 00042 10 PMC 2863845 PMID 20200241 2012 Nature Medicine 18 1592 Hai R Martinez Sobrido L Fraser KA Ayllon J Garcia Sastre A Palese P 2008 Influenza B virus NS1 truncated mutants live attenuated vaccine approach J Virol 82 21 10580 10590 doi 10 1128 jvi 01213 08 PMC 2573209 PMID 18768976 Talon J Salvatore M O Neill RE Nakaya Y Zheng H Muster T Garcia Sastre A Palese P 2000 Influenza A and B viruses expressing altered NS1 proteins A vaccine approach Proc Natl Acad Sci U S A 97 8 4309 4314 Bibcode 2000PNAS 97 4309T doi 10 1073 pnas 070525997 PMC 18238 PMID 10725408 Solorzano A Webby RJ Lager KM Janke BH Garcia Sastre A Richt JA 2005 Mutations in the NS1 protein of swine influenza virus impair anti interferon activity and confer attenuation in pigs J Virol 79 12 7535 7543 doi 10 1128 jvi 79 12 7535 7543 2005 PMC 1143661 PMID 15919908 Vincent AL Ma W Lager KM Janke BH Webby RJ Garcia Sastre A Richt JA 2007 Efficacy of intranasal administration of a truncated NS1 modified live influenza virus vaccine in swine Vaccine 25 47 7999 8009 doi 10 1016 j vaccine 2007 09 019 PMC 2099695 PMID 17933442 Quinlivan M Zamarin D Garcia Sastre A Cullinane A Chambers T Palese P 2005 Attenuation of equine influenza viruses through truncations of the NS1 protein J Virol 79 13 8431 8439 doi 10 1128 jvi 79 13 8431 8439 2005 PMC 1143746 PMID 15956587 Steel J Lowen AC Pena L Angel M Solorzano A Albrecht R Perez DR Garcia Sastre A Palese P 2009 Live attenuated influenza viruses containing NS1 truncations as vaccine candidates against H5N1 highly pathogenic avian influenza Journal of Virology 83 4 1742 1753 doi 10 1128 jvi 01920 08 PMC 2643794 PMID 19073731 Baskin CR Bielefeldt Ohmann H Garcia Sastre A Tumpey TM Hoeven N Van Carter VS Thomas MJ Proll S Solorzano A Billharz R Fornek JL Thomas S Chen CH Clark EA Murali Krishna K Katze MG 2007 Functional genomic and serological analysis of the protective immune response resulting from vaccination of macaques with an NS1 truncated influenza virus J Virol 81 21 11817 11827 doi 10 1128 jvi 00590 07 PMC 2168783 PMID 17715226 a b Garcia Sastre A Egorov A Matassov D Brandt S Levy DE Durbin JE Palese P Muster T 1998 Influenza A virus lacking the NS1 gene replicates in interferon deficient systems Virology 252 2 324 30 doi 10 1006 viro 1998 9508 PMID 9878611 a b Wang L Suarez DL Pantin Jackwood M Mibayashi M Garcia Sastre A Saif YM Lee CW 2008 Characterization of Influenza Virus Variants with Different Sizes of the Non structural NS Genes and Their Potential as a Live Influenza Vaccine in Poultry Vaccine 26 29 30 3580 3586 doi 10 1016 j vaccine 2008 05 001 PMC 2785844 PMID 18539366 External links editNCBI Flu Genome Database Retrieved from https en wikipedia org w index php title NS1 influenza protein amp oldid 1222510324, wikipedia, wiki, book, books, library,
