Figure 3.

Requirement of the signal tranducer and activator of transcription 1 transactivating domain and its phosphorylation at Ser727 for the expression of interferon-β-induced genes. Stat1-deficient fibroblasts, and cells that express Stat1-α, Stat1-β or Stat1-S727A were treated with interferon-β (IFN-β) for 4 h or 6 h. Expression of the Irf1, Gbp1 and Mx1 genes was determined by quantitative real-time PCR of reverse-transcribed messenger RNA. For normalization to input quantities, the amount of Hprt mRNA was determined. (A) Inducibility in response to treatment with IFN-β (that is, the ratio of expression in IFN-β-treated and untreated cells) after 4 h and 6 h in one of three independent experiments. (B) The results of three independent experiments are shown, expressed as the percentage induction ± s.d. in cells that express Stat1-β, Stat1-S727A or that express no Stat1, compared with the values measured in cells that express Stat1-α (100%).