title: U4 at the 3' UTR of PB1 segment of H5N1 influenza virus promotes RNA polymerase activity and contributes to viral pathogenicity.
abstract: The viral RNA-dependent RNA polymerase has been found to contribute to efficient replication in mammalian systems and to the high pathogenicity of H5N1 influenza A virus in humans and other mammals. The terminal untranslated regions of the viral segments perform functions such as polyadenylation and contain signals for genomic packaging and initiation of RNA synthesis. These sequences are highly conserved, apart from a U/C polymorphism at position 4 of the 3' end, most often seen in the polymerase gene segments. However, no study has yet tested whether the untranslated regions of H5N1 make any contribution to its high pathogenicity. Herein, the association of the fourth nucleotide at the 3' end of the untranslated region in segment 2 (PB1), of A/Vietnam/1194/2004 (H5N1), with pathogenicity was examined in mice. To this end, an RNA polymerase reporter system was constructed, and viruses with mutations at this site were rescued. Results showed the U4 in PB1 was found to contribute to greater amounts of RNA-dependent RNA polymerase activity and differentially regulate genomic transcription and replication. Although a recombinant H5N1 virus with the rarer C4 sequence in all eight segments was viable and replicated to high titers in vitro, replacing a single U4 at the 3' termini of the PB1 gene segment enhanced viral reproduction and more pathogenesis. In this way, these data showed the importance of untranslated regions of H5N1 influenza virus to pathogenicity.
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Han
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Yinhui
authors.initials: Y
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Kang
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Yuchang
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Jiaming
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Chengfeng
authors.initials: C
authors.lastname: Qin
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, PR China.
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Zhu
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D005260:Female; D015967:Gene Expression Regulation, Viral; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D051379:Mice; D008807:Mice, Inbred BALB C; D009976:Orthomyxoviridae Infections / Q000401:mortality / Q000821:virology*; D016019:Survival Analysis; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014779:Virus Replication
chemical_list: D020413:3' Untranslated Regions; D014764:Viral Proteins; C077346:influenza virus polymerase basic protein 1