Fig. 1

N proteins dually regulate production of IFN-I and inflammatory cytokines. a, b HEK293T cells in 24-well plate were co-transfected with an IFN-β promoter (a) or ISRE reporter plasmid (b), along with control plasmid pGL4.74 and 0.25, 0.5, or 1 μg SARS-CoV-2 or SARS-CoV N (2N or N) plasmids, then treated with or without poly(I:C), the empty vector as a control. At 24 h post-transfection (hpt), cells were harvested and luciferase activity was measured (upper); the expression of 2N and N proteins was detected by western blot, GAPDH as a loading control (down). c–e HEK293T cells in 24-well plate were transfected with 0.25, 0.5, or 1 μg 2N or N plasmids, then treated with or without poly(I:C). At 24 hpt, the mRNA expression of IFNA (c), IFNB1 (d), and interferon-stimulated genes ISG15 and OAS1 (e) were examined using qPCR. f HEK293T cells in 24-well plate were transfected with a dose-gradient 2N plasmid, then treated with or without poly(I:C). At 24 hpt, the mRNA expression of IL1B, IL6, and TNFA were examined using qPCR. Results shown are the mean ± SD of at least three independent experiments