Deficiency of G9a in MEFs enhances resistance to viral infection. (A) G9a^f/f and G9a^−/− MEFs were infected with VSV (MOI 0.01) or influenza A (MOI 1), followed by the analysis of Ifnβ mRNA expression levels by qPCR at 0 and 24 h after infection. (B) G9a^f/f or G9a^−/− MEFs were infected with VSV (MOI 0.01), followed by the analysis of Ifi44, Ifit1, Iigp1, and Oas2 mRNA (ISGs) by qPCR at 0 and 24 h after infection. (C) MEFs were stimulated with 500 U/ml recombinant IFN-β and expression of ISGs was determined by qPCR. Untreated is denoted as −. (D) G9a^f/f and G9a^−/− MEFs were infected with VSV or Sindbis viruses expressing GFP at the indicated MOIs. The infected cells were identified by flow cytometry at 14 h after infection by GFP fluorescence. The histograms show the levels of GFP expression, as well as frequencies, of infected GFP-positive cells. Data (A–D) are representative of at least three independent experiments. Error bars are SD.