Effect Of The Interaction Of Avian Influenza Virus NS1Protein With NOLC1Protein On Apoptosis Of Host Cells

Avian influenza virus is a fulminating infectious disease caused by type Ainfluenza viruses that regularly cause outbreaks of influenza in birds, but infectionscan occur in humans. Infection with avian influenza viruses in domestic poultrycauses two main forms of disease that are distinguished by low and high extremes ofvirulence. The highly pathogenic form spreads more rapidly through flocks ofpoultry. Highly pathogenic Influenza A (H5N1)–also called "HPAI " is recognized ascategory A infectious disease by the World Organisation for Animal Health (OIE).The non-structural (NS1) protein of influenza A viruses is a uniquenon-structural protein that has multiple accessory functions during viral infection.NS1protein of influenza A virus interacts with varieties of cellular multifunctionalprotein during infection. NS1also acts directly to modulate other important aspects ofthe virus replication cycle, including viral RNA replication, viral protein synthesis,and general host-cell physiology,thereby enhacing virus pathogenicity. To gain furtherinsight into the various roles NS1has in regulating viral replication mechanisms andthe host signaling cascade. We have used T7-phage display technology to screennovel cellular factors that interact with NS1, which is human nucleolar andcoiled-body phosphoprotein1(NOLC1). We researched the functional interactionof NS1with NOLC1by co-immunoprecipitation and GST pull-down assays, andproved the interaction of NS1and NOLC1directly.Nucleolar and coiled-body phosphoprotein1previously named Nopp140orp130, is a140kDa nucleolar phosphoprotein that has been shown to exist in multipleforms with different sizes. Nopp140functions both as a chaperone for import and/orexport from the nucleolus and as a transcription factor. It is related to nucleologenesis,may play a role in the maintenance of the fundamental structure of the fibrillar centerand dense fibrillar component in the nucleolus. It has intrinsic GTPase and ATPaseactivities, may play an important role in transcription catalyzed by RNA polymerase I.In our study, to test the effect of interaction of influenza A virus NS1with NOLC1on the host cell apoptosis during viral infection. NS1gene was respectively subclonedinto pEGFP-N1vector to construct euaryotic expression vectors pEGFP-N1-NS1, andwe depleted endogenous NOLC1using small interference RNA(siRNA)-mediatedknockdown technoloy, or upregulated NOLC1in A549cells by exogenoustransfection with pDsRed-N1-NOLC1plasmid. They were respectively co-transfectedinto A549cells.Apoptosis in the transfected A549cells were tested by Hoechst33258Staining and Annexin V-PI respectively. The results demonstrated that the interactionof influenza A virus NS1with NOLC1is sufficient to inhibit apoptosis in A549cells.These data suggest that the pathogenesis of highly pathogenic influenza A virusmay depend on the interaction of NOLC1in host cell. The conclusion provided us agood foundation for further studying the biological function of NS1of highlypathogenic Influenza A interacting with the host cells. Given a new perspective tounderstand the host antiviral defense machine.