NS1 influenza protein
The NS1 influenza protein (NS1) is a viral nonstructural protein encoded by the NS gene segments of type A, B and C influenza viruses. Also encoded by this segment is the nuclear export protein (NEP), formally referred to as NS2 protein, which mediates the export of influenza virus ribonucleoprotein (RNP) complexes from the nucleus, where they are assembled. Characteristics The NS1 of influenza A virus is a 26,000 Dalton protein. It prevents polyadenylation of cellular mRNAs to circumvent antiviral responses of the host, e.g., maturation and translation of interferon mRNAs. NS1 might also inhibit splicing of pre-mRNA by binding to a stem-bulge region in U6 small nuclear RNA (snRNA). In addition, NS1 is probably able to suppress the interferon response in the virus-infected cell leading to unimpaired virus production. NS1 also binds dsRNA. Binding assays with NS1 protein mutants established that the RNA-binding domain of the NS1 protein is required for binding to dsRNA as well as for binding to polyA and U6 snRNA. In addition, dsRNA competed with U6 snRNA for binding to the NS1 protein, a result consistent with both RNAs sharing the same binding site on the protein. As a consequence of its binding to dsRNA, the