Study On The Interaction Between Influenza Virus NP Protein And Host SNRPA Protein

Influenza virus is an important causative agent of disease and death in humans.It is classified within the family of Orthomyxoviridae.According to the antigenic of NP and M1,the influenza virus can be divided into type A,type B and C.Type A influenza is a kind of acute contagious disease of the poultry and wild birds.It’s also a zoonosis that can infect and kill humans.Therefore,influenza virus is a serious threat for both human health and development of animal husbandry.Influenza A virus is negative-sense,single-stranded,enveloped ribonucleic acid(RNA)viruses with a segmented genome.The eight vRNA segments encode 10 kinds of essential proteins.Nucleoprotein(NP)is a major structural protein encoded by the 5th segment of viral genome,which associates with viral RNA and three polymerase proteins(PB1,PB2,PA)to form viral ribonucleoprotein(vRNP)complex,the basic functional unit for transcription and replication of the viral genome.NP plays a critical role during the transcription and replication of viral genome and the nuclear-cytoplasmic shuttling of vRNP complex.Moreover,NP plays a significant role in virus replication through regulating different signal pathway by interacting with various host proteins.The in-depth study on the interactions between NP and host proteins will deepen our understanding on the mechanisms of influenza virus pathogenesis,and can also provide scientific basis for the development of novel anti-influenza drugs.In this study,we identified host protein SNRPA(U1 small nuclear ribonucleoprotein A)as an interacting partner of NP protein by using yeast two-hybrid screening.SNRPA is a kind of spliceosome protein and has a variety of functions.It binds with high affinity to stem-loop II of U1 snRNA and plays a role in the process of pre-mRNA splicing and polymerization.Moreover,SNRPA can interact with NS5 protein of the yellow fever virus and influence NS5 protein shuttling between nucleus and cytoplasm.The interaction between NP and SNRPA was further validated by yeast backcross verification,co-immunoprecipitation(Co-IP)and GST pull-down assay.The confocal microscopy further revealed that NP and SNRPA clearly colocalized in the cytoplasm of A549 cell.To understand the biological significance of NP-SNRPA interaction,we established a stable SNRPA-overexpressing A549 cell line or downregulated SNRPA with specific siRNA.The results showed that the down regulation of SNRPA by siRNA reduced the replication of influenza virus,whereas the overexpression of SNRPA promoted the virus growth.Collectively,these data demonstrated that the NP-SNRPA interaction positively regulates the replication of influenza virus.This study enriched the interaction network formed between influenza viral proteins and host cellular proteins,and laid a foundation to further reveal the pathogenesis of influenza virus and to develop novel anti-influenza drugs.