Screening Host Factors To Interact With NS1 By Yeast Two-hybrid System

The NS1 protein, a non-structural protein of Avian Influenza Virus, is about 230 amino acids in length. Its molecular weight is about 26 KDa. The protein has two functional domains: an RNA binding domain in the amino terminal and an effector domain in the carboxyl terminal. As a multifunctional viral protein, the NS1 protein can not only influence the expression of other genes of the virus, but also counteract host defense system by interacting with many cellular proteins. Therefore, the NS1 protein is regarded as a crucial virulent factor for Avian Influenza Virus. To find other cellular proteins that interact with NS1, to explore new functions of NS1 and then to elucidate the possible mechanism of NS1 pathogenicity, a human thymus cDNA library was screened using yeast two-hybrid system and eight genes were found to interact with NS1. We chose U protein as our object protein and did yeast point to point back-hybrid to identify its interaction. We also found that U interacts with NS1 RNA binding domain. The interaction of these two proteins was further confirmed by GST pull down. From our study, we also found that the 80-84aa deletion of HPAIV NS1 may be very important for NS1 pathogenicity. This indicates a new drug target for lethal H5N1.