Fangliang Zheng

Interaction of avian influenza virus NS1 protein and nucleolar and coiled-body phosphoprotein 1.

Nonstructural protein 1 (NS1) is a non-structural protein of avian influenza virus. It can interact with a variety of proteins of the host cells, enhancing the expression of viral proteins and changing the growth and metabolism of the host cells, thereby enhancing the virus’ pathogenicity and virulence. To investigate whether there are more host proteins that can interact with NS1 during viral infection, T7-phage display system was used to screen human lung cell cDNA library for proteins that could interact with NS1. One positive and specific clone was obtained and identified as nucleolar and coiled-body phosphoprotein 1(NOLC1). The interaction between these two proteins was further demonstrated by His-pull-down and co-immunoprecipitation experiments. Co-expression of both proteins in HeLa cell showed that NS1 and NOLC1 were co-localized in the cell’s nucleus. Gene truncation experiments revealed that the effector domain of NS1 was sufficient to interact with NOLC1. The results demonstrated a positive interaction between a viral NS1 and NOLC1 of the host cells, and provided a new target for drug screening.

Discovery of novel influenza inhibitors targeting the interaction of dsRNA with the NS1 protein by structure-based virtual screening

Influenza A Non-structural protein 1 (NS1A) RNA-Binding Domain (RBD) bound to a double-stranded RNA (dsRNA), which can inhibit the activation of antiviral pathway. The chemical compound binding sites at this pocket have abilities to block NS1 protein to inhibit dsRNA-dependent activation transfected beta interferon promoter construct. The molecular docking program AUTODOCK was used for virtual screening of about 200,000 compounds. Two more typical compounds were selected as the starting point for predicting binding modes. Further analysis shows that these compounds candidates of antiinfluenza drug, which provide an important reference for discovering new influenza virus drugs.

Identification of NS1 domains of avian H5N1 influenza virus which influence the interaction with the NOLC1 protein.

Non-structural protein 1 (NS1) is an important virulence factor encoded by influenza A virus. NS1 can interact with a variety of host cell proteins to interfere with the host innate immune response and to promote effective viral replication. Our previous work has shown that only the effector domain of NS1 (amino acid residues 74-230/237) is sufficient to interact with nucleolar and coiled-body phosphoprotein 1 (NOLC1). To investigate the exact region of NS1 that interacts with NOLC1, we used only the effector domain of NS1 and constructed various mutants having different deletions, and then tested their ability to interact with NOLC1 via pull-down assay. Only the mutant containing amino acid residues 104–200 showed positive interaction with NOLC1. To further determine the key amino acids of the NS1 effector domain which are crucial for interaction with NOLC1, several mutants containing a single amino acid substitution were made and their interaction with NOLC1 was tested. Only the mutant D120A or R195A showed reduced binding with NOLC1, suggesting that D120 and R195 were crucial to the binding of NS1 to NOLC1. This study lays the foundation for further research aiming at furthering our understanding of the interaction between NS1 and host cells.

Structure-Based Virtual Screening for Potential Inhibitors of Influenza A Virus RNA Polymerase PA Subunit

The amino terminus of RNA polymerase A (PA-N) of influenza virus is an important target for the design of new antiviral agents. In this study, molecular docking was used to screen for compounds that specifically target the deep cleft at the endonuclease active site in N-terminus of the RNA polymerase. Four potential compounds (NCI100226, NCI122653, NCI625583, and NCI403587) with high binding affinity for the active site were identified. Structural analysis of the binding conformation of each of these compound-PA-N complexes revealed that hydrophobic interaction and manganese ion chelation comprised the main interaction between the compounds and enzyme. The binding configuration stability and the number of hydrogen and ionic bonds were investigated by molecular dynamic simulations. The results indicated that NCI403587 could be a promising PA-N inhibitor, and may represent a potential new agent for the treatment of influenza.

The interaction between NOLC1 and IAV NS1 protein promotes host cell apoptosis and reduces virus replication

NS1 of the influenza virus plays an important role in the infection ability of the influenza virus. Our previous research found that NS1 protein interacts with the NOLC1 protein of host cells, however, the function of the interaction is unknown. In the present study, the role of the interaction between the two proteins in infection was further studied. Several analyses, including the use of a pull-down assay, Co-IP, western blot analysis, overexpression, RNAi, flow cytometry, etc., were used to demonstrate that the NS1 protein of H3N2 influenza virus interacts with host protein NOLC1 and reduces the quantity of NOLC1. The interaction also promotes apoptosis in A549 host cells, while the suppression of NOLC1 protein reduces the proliferation of the H3N2 virus. Based on these data, it was concluded that during the process of infection, NS1 protein interacts with NOLC1 protein, reducing the level of NOLC1, and that the interaction between the two proteins promotes apoptosis of host cells, thus reducing the proliferation of the virus. These findings provide new information on the biological function of the interaction between NS1 and NOLC1.