TSA suppresses IFNα-induced PML transcription. (A) Western blot analysis of PML, Sp100, and IRF1 proteins in HeLa cells. Cell lysates (50 μg total protein) were loaded on the SDS gels. Proteins were detected by the indicated antibodies; Coomassie- or Ponceau S–stained bands of actin were used as a loading control. (B-C) Real-time RT-PCR quantification of PML mRNA. (B) HeLa cells were treated with 1000 U/mL interferon-α (IFN), 500 ng/mL trichostatin A (TSA), or both (IFN + TSA) for 1, 4, 8, and 24 hours. PML mRNA levels were normalized to GAPDH; the same results were obtained using other 2 control genes—actin and 18S rRNA (not shown). (C) Various cell lines were treated with IFN, TSA, or IFN + TSA for 8 hours, and PML mRNA was quantified by real-time RT-PCR relative to GAPDH.