α-CoV nsp1 reduces interferon (IFN)-related gene expression. (A,B) HEK-293T cells were transfected with a Luc reporter plasmid ([A]; IFN-β promoter, [B]; ISRE promoter) and an expression plasmid encoding a full-length α-CoV nsp1 protein of SADS-CoV, TGEV, FIPV, porcine respiratory coronavirus (PRCV), PEDV, HCoV-NL63 or HcoV-229E. At 8 h post-transfection, the cells were treated with a viral poly(I:C) (A) or IFN-α (B), and the luciferase activity was measured 16 h later. The data are presented as the means ± SD (n = 3). Asterisks indicate statistical significance as determined by Student’s t-test. ***, p < 0.001. (C) Transfected HEK-293T cells were fixed at 24 h post-transfection, and indirect immunofluorescence assays were performed with a monoclonal antibody against the HA protein. Original magnification × 200 (scale bars 100 μm). (D) Western blot analysis of extracts from HEK-293T cells that were transfected with the mock control or α-CoV nsp1 for 24 h. The analysis was performed with antibodies against STAT1, STAT1 phosphorylation on S727, STAT1 phosphorylation on Y701, HA, and GAPDH (left). The gray scale values of the protein bands were analyzed with ImageJ (right). The data are presented as the means ± SD (n = 3). Asterisks indicate statistical significance as determined by Student’s t-test. Ns: Not significant; *, p < 0.05.