Host Protein PIAS1 Interacts With Polymerase And NP Protein Of Influenza A Virus And Thereby Regulates Viral Replication

Influenza A virus(IAV)is an important zoonotic pathogen that is responsible for the annual seasonal epidemics,causing substantial morbidity and mortality in humans and a considerable financial burden worldwide every year.Although vaccines are available to prevent infections in humans,the haemagglutinin(HA)proteins of circulating viruses rapidly acquire mutations,which prevent their recognition by the host immune system and necessitate replacement of the vaccine strains every 1–3years.Antiviral compounds are available for prophylaxis and therapeutic treatment of IAV infections,but antiviral resistance is a continuing problem.Given the centrality of vRNP to every aspect of the IAV life cycle,a clearer understanding of their fundamental roles during infection has enormous potential for revealing mechanisms of pathogenesis and understanding host adaptation,and for developing new methods to prevent or treat IAV disease.Nucleoprotein(NP)is one of the most abundant structural proteins of influenza virus particle,and is involved in multiple processes of the virus life cycle.To screen for host interacting partners of NP protein,we applied a yeast two-hybrid strategy by using NP as bait.PIAS1 was identified and its interaction with NP was further demonstrated by co-immunoprecipitation(Co-IP),GST pull-down and confocal microscopy.We found that overexpression of PIAS1 inhibited the virus replication,whereas knockdown of PIAS1 promoted the virus growth.Dual luciferase reporter assay indicated that PIAS1 expression reduced viral RNP activity.We also found that PIAS1 interacted with PB1 and PB2,and overexpression of PIAS1 suppressed vRNP complex assembly.In addition,PIAS1 mutants C351 S and W372 A that lose the E3 ligase activity were unable to suppress the RNP activity of IAV.Strikingly,PIAS1 expression was considerably increased in A549 cells and mouse lungs infected with IAV.PIAS1 is an inhibitor of JAK/STAT1 and NF-?B signaling pathway.To determine the effect of PIAS1 in these pathways,A549 cells infected with WSN virus were stimulated with TNF/IFN-beta.The Q-PCR data showed that IAV infection could increase PIAS1 sensitive genes expression.Further study demonstrated that the interaction between PIAS1 and STAT1 or P65 was reduced in virus infected cells.In conclusion,our study identified that host cellular protein PIAS1 interacted with the vRNP complex proteins of IAV,and further revealed the role of PIAS1 on the regulation of viral replication.Our findings enriched the understanding on the regulation of IAV life cycle,and deepened the knowledge on host immune response against IAV infection.