title: Atypical characteristics of nucleoprotein of pandemic influenza virus H1N1 and their roles in reassortment restriction.
abstract: Sequence analysis of the nucleoprotein (NP) of swine-origin influenza virus H1N1 (S-OIV) reveals a number of atypical characteristics including an early start codon and a highly conserved, non-aromatic residue at position 313. Using an in vitro viral polymerase reconstitution assay, we found that the polymerase complex containing the NP of S-OIV (NP(S-OIV)) yielded substantially lower activity than those assayed with NP derived from other influenza virus strains. Moreover, alteration of the early start codon or introduction of an aromatic residue at position 313 (V313Y) did not increase but instead exacerbated the poor polymerase activity. Interestingly, when NP(S-OIV) was allowed to compete with that of a mouse-adapted influenza virus (A/PR/8/34) to form progeny virions, only progeny bearing NP(S-OIV) were produced, despite the low polymerase activity associated with NP(S-OIV). Our results indicated that NP(S-OIV) requires both the early start codon and the V313 residue for its optimal function. These characteristics are required for a strong compatibility between the S-OIV polymerase subunits and its indigenous NP over that of other strains, which might explain why productive reassortment between S-OIV and seasonal influenza viruses has yet to occur in nature.
authors.affiliation: Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), 113 Phaholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Asawin
authors.initials: A
authors.lastname: Wanitchang
authors.forename: Prasatha
authors.initials: P
authors.lastname: Patarasirin
authors.forename: Juggragarn
authors.initials: J
authors.lastname: Jengarn
authors.forename: Anan
authors.initials: A
authors.lastname: Jongkaewwattana
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D018387:Codon, Initiator; D004285:Dogs; D057809:HEK293 Cells; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics* / Q000502:physiology; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology; D009154:Mutation; D019590:Nucleocapsid Proteins; D058873:Pandemics; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*; D016865:Reassortant Viruses / Q000235:genetics* / Q000502:physiology; D011995:Recombination, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012261:Ribonucleoproteins / Q000378:metabolism*; D014758:Viral Core Proteins / Q000235:genetics* / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D018387:Codon, Initiator; C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D014758:Viral Core Proteins; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase