Fig. 2. ChIP analysis of transcription factor recruitment upon IFN induction. HT1080 and STAT1-null U3A cells were treated with 200 IU/ml IFN at the times shown, and crosslinked with formaldehyde. Immunoprecipitated DNA and serial dilutions of genomic DNA were then subjected to quantitative RT-PCR. The fold enrichment was calculated relative to the non-induced levels. ChIP experiments were performed using antibodies recognizing P-STAT1, RNAP II, BRG1 and acetylated Histone H3. The mean values of at least three experiments are shown, together with standard error bars.