title: Characteristic amino acid changes of influenza A(H1N1)pdm09 virus PA protein enhance A(H7N9) viral polymerase activity.
abstract: Human coinfection with a novel H7N9 influenza virus and the 2009 pandemic A(H1N1) influenza virus, H1N1pdm09, has recently been reported in China. Because reassortment can occur during coinfection, it is necessary to clarify the effects of gene reassortment between these two viruses. Among the viral ribonucleoprotein complex (vRNP) genes, only the PA gene of H1N1pdm09 enhances the avian influenza viral polymerase activity. Based on a phylogenetic analysis, we show a special evolutionary feature of the H1N1pdm09 PA gene, which clustered with those of the novel H7N9 virus and related H9N2 viruses, rather than in the outgroup as the H1N1pdm09 genes do on the phylogenetic trees of other vRNP genes. Using a minigenome system of the novel H7N9 virus, we further demonstrate that replacement of its PA gene significantly enhanced its polymerase activity, whereas replacement of the other vRNP genes reduced its polymerase activity. We also show that the residues of PA evolutionarily conserved between H1N1pdm09 and the novel H7N9 virus are associated with attenuated or neutral polymerase activity. The mutations associated with the increased activity of the novel H7N9 polymerase are characteristic of the H1N1pdm09 gene, and are located almost adjacent to the surface of the PA protein. Our results suggest that the novel H7N9 virus has more effective PB1, PB2, and NP genes than H1N1pdm09, and that H1N1pdm09-like PA mutations enhance the novel H7N9 polymerase function.
authors.affiliation: Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou, 510080, Guangdong, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou, 510080, Guangdong, China.|Department of Respiration, Affiliated Guangzhou Women and Children's Hospital, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, Guangdong, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Huang
authors.affiliation: Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou, 510080, Guangdong, China.
authors.forename: Junsong
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou, 510080, Guangdong, China.
authors.forename: Likai
authors.initials: L
authors.lastname: Tan
authors.affiliation: Department of Respiration, Affiliated Guangzhou Women and Children's Hospital, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, Guangdong, China.
authors.forename: Gen
authors.initials: G
authors.lastname: Lu
authors.affiliation: Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou, 510080, Guangdong, China. zhxu22@mail.sysu.edu.cn.
authors.forename: Xu
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou, 510080, Guangdong, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000596:Amino Acids / Q000235:genetics / Q000378:metabolism*; D002681:China; D060085:Coinfection / Q000821:virology; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004789:Enzyme Activation; D019143:Evolution, Molecular; D005814:Genes, Viral; D016679:Genome, Viral; D057809:HEK293 Cells; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D064766:Influenza A Virus, H7N9 Subtype / Q000201:enzymology / Q000378:metabolism*; D053127:Influenza A Virus, H9N2 Subtype / Q000201:enzymology / Q000235:genetics; D007251:Influenza, Human / Q000821:virology; D009154:Mutation; D019590:Nucleocapsid Proteins; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D012367:RNA, Viral / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016865:Reassortant Viruses / Q000145:classification / Q000235:genetics; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000596:Amino Acids; C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; C061290:PA protein, influenza viruses; C502893:PB2 protein, influenza virus; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D014758:Viral Core Proteins; D014764:Viral Proteins; C077346:influenza virus polymerase basic protein 1; D012324:RNA-Dependent RNA Polymerase; D012321:DNA-Directed RNA Polymerases
keywords: H7N9; Influenza A virus; Mutation; PA; Polymerase activity; Reassortment