Fig. 4.

SARS-CoV-2 nsp12 suppresses the nuclear translocation of IRF3. a Effect of SARS-CoV-2 nsp12 on SeV-induced nuclear translocation of IRF3. HEK293T cells were transfected with a control plasmid or an nsp12 expression plasmid. At 24 h post transfection, the cells were infected with SeV for 4 h and then immunostained with the indicated antibodies. Merge 1 and Merge 2 indicate the merged red and green channels and the merged red, green, and blue channels, respectively. Scale bar, 10 μM. The enlarged image is a magnified view of the corresponding box. b Quantitation of the nuclear translocation of IRF3. The percentage of nuclear IRF3-positive transfected cells was determined in three independent experiments. The two-tailed unpaired t-test was used for two-group comparisons, ***P < 0.001. c Immunoblot analysis of cytoplasmic and nuclear IRF3 after SeV infection. HEK293T cells were transfected with a control plasmid or an nsp12 expression plasmid. After 24 h, the cells were infected with SeV for 4 h and fractionated into cytoplasmic and nuclear fractions. The fractions were analyzed by western blotting for IRF3 and nsp12 detection. β-Tubulin and Lamin A were used as a cytoplasmic and a nuclear marker, respectively. The numbers under the lanes indicate the IRF3 band intensity, which was normalized to that of Lamin A. d Effect of SARS-CoV-2 nsp12 on RIG-IN-induced nuclear translocation of IRF3. HEK293T cells were transfected with RIG-IN or RIG-IN and nsp12 expression plasmids. At 24 h post transfection, the cells were immunostained with the indicated antibodies