Amino acid at position 176 was essential for porcine reproductive and respiratory syndrome virus (PRRSV) non-structural protein 1α (nsp1α) as an inhibitor to the induction of IFN-β

► The carboxyl-terminal extension was required for nsp1α as IFN-β antagonist. ► 1-176 of nsp1α is sufficient to inhibit the induction of IFN-β. ► The residue at 176 was essential for nsp1α to inhibit the induction of IFN-β. ► The residue at 176 is essential for nsp1 to release nsp1α. ► The residue at 176 was essential for nsp1 to inhibit the induction of IFN-β.