title: Truncated forms of the PA protein containing only the C-terminal domains are associated with the ribonucleoprotein complex within H1N1 influenza virus particles.
abstract: We have examined the expression profile of the influenza virus PA protein in pH1N1/2009 virus-infected cells. Immunoblotting analysis of virus-infected MDCK cells revealed the presence of full-length PA protein from 8 h post-infection, together with the simultaneous appearance of PA protein species of approximately 50, 35/39 and 20/25 kDa (collectively referred to as PA*). PA* was also detected in H1N1/WSN-virus-infected cells, indicating that its presence was not virus-specific, and it was also observed in virus-infected A549 and chick embryo fibroblast (CEF) cells, indicating that its presence was not cell-type-specific. PA* was detected in cells expressing the recombinant PA protein, indicating that the PA* formation occurred in the absence of virus infection. These data collectively indicated that PA* formation is an intrinsic property of PA gene expression. The association of PA* with purified influenza virus particles was demonstrated by immunoblotting, and a protease protection assay provided evidence that PA* was packaged into virus particles. The ribonucleoprotein (RNP) complex was isolated from purified influenza virus particles using glycerol gradient centrifugation, which demonstrated that PA* was associated with the RNP complex. To the best of our knowledge, this is the first report to demonstrate that PA protein species containing only segments of the C-terminal domain form during influenza virus infection. Furthermore, these truncated PA protein species are subsequently packaged into virus particles as part of the functional RNP complex.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
authors.forename: Myint Zu
authors.initials: MZ
authors.lastname: Myaing
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
authors.forename: Muhammad Raihan
authors.initials: MR
authors.lastname: Jumat
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
authors.forename: Tra Nguyen
authors.initials: TN
authors.lastname: Huong
authors.affiliation: Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, Singapore 117510, Singapore.
authors.forename: Boon Huan
authors.initials: BH
authors.lastname: Tan
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Sugrue
keywords: H1N1; PA protein; influenza virus; polymerase complex