PDZ Binding Motif of NS1 Proteins of  Influenza A Viruses: : A Virulent Factor in the Expression of Interferon-β?

Abstract: Background:  The PDZ domain is a peptide sequence of 80-90 amino acids and can be found in e.g. bacteria, animals and plants. These domains are commonly part of the cytoplasmic and membrane adapter proteins and its function are important in protein-protein interactions. The NS1 proteins of influenza A viruses play an important role in inhibiting the IFN-β production in many ways. In the C-terminus of the NS1 protein, a peptide sequence of four amino acids had been demonstrated to bind to the PDZ domain termed as PDZ binding motif (PBM). Objective:  The aim of this study is to determine whether the PBM sequence of the NS1 protein of influenza A virus plays a key roll in the expression of interferon-β. Methods:  The open reading frame of the NS1 protein was amplified and cloned into expressing vector and transfected into A549 cells along with a reporter plasmid containing ISRE promoter, driving expression of firefly luciferase. Dual luciferase reporter assay was performed to measure luciferase activity which represented expression of IFN-β. The assay was performed only once and unfortunately the result can not be trusted since the negative control showed positive value. Therefore, to understand the interaction between the PBM sequence of NS1 proteins and the production of IFN-β, further experiments are needed.