FIG 4.

hHB regulates the RIG-I- and MDA5-mediated antiviral response to RNA viruses. (A and B) The effects of hHB overexpression on the replication of SeV, VSV, and NDV in MDA5^−/− and RIG-I^−/− cells. MDA5^−/− or RIG-I^−/− cells were transfected with p3×Flag-hHB for 24 h and then were infected with SeV for 24 h or with VSV-GFP or NDV-GFP for 48 h. The viral titers of SeV in the supernatants, the RNA level of the SeV N protein in cells, or GFP expression and fluorescence of VSV-GFP or NDV-GFP were determined. (C and D) The effect of hHB-overexpression on the replication of EMCV in MDA5^−/− and RIG-I^−/− cells. MDA5^−/− or RIG-I^−/− cells were infected with EMCV for 24 h. Then the titers in the supernatants and the RNA level of the EMCV 3D protein in the cells were determined. (E and F) Deficiency of hHB differently affected the replication of SeV, VSV, and NDV in RIG-I^−/− and MDA5^−/− cells. MDA5^−/− hHB^−/− cells and MDA5^−/− or RIG-I^−/− hHB^−/− and RIG-I^−/− cells, as indicated, were infected with SeV for 24 h or with VSV-GFP or NDV-GFP for 48 h. Then the viral titers of SeV in the supernatants, the RNA level of the SeV N protein in the cells, or the GFP expression and fluorescence of VSV-GFP or NDV-GFP were analyzed. (G and H) Deficiency of hHB differently affected the replication of EMCV in RIG-I^−/− and MDA5^−/− cells. MDA5^−/− hHB^−/− cells and MDA5^−/− cells or RIG-I^−/− hHB^−/− and RIG-I^−/− cells, as indicated, were infected with EMCV for 24 h. The titers in the supernatants and the RNA level of the EMCV 3D protein in the cells were determined. The data represent the means ± standard deviations from three independent experiments. Significant differences are denoted as follows: *, P < 0.05; **, P < 0.01; ***, P < 0.001; NS, not significant (P > 0.05).