Effect of the histone deacetylase inhibitors SB and TSA and the DNA methyltransferase inhibitor AZA on transcription of CpG-free reporter plasmids and on a TC620 clonal reporter cell line. A. The JCV early and late promoters were cloned into the pCpG reporter plasmid and transfected into TC620 cells, which were then treated with inhibitors (SB – 5, 10 and 15 mM; TSA – 0.2, 0.4 and 1 μM AZA – 10, 15 and 25 μM), harvested and assayed for luciferase activity as described in Methods. Activities were normalized to untreated controls. The bar represents one standard deviation. B. A clonal cell line derived from TC620 by stable transfection with a plasmid encoding the luciferase reporter gene driven by the JCV early promoter  was treated with inhibitors (EtOH – ethanol vehicle control; SB – 5 and 10 μM; AZA – 10 and 15 μM; TSA – 0.5 and 1 μM), harvested and assayed for luciferase activity. Activities were normalized to untreated controls. The bar represents one standard deviation. C. As for B except using a stable clone with the late promoter (SB – 5 μM; TSA – 0.5 μM). D. As for B using a stable clone with the early promoter except treating with inhibitors for three days, adding fresh inhibitor everyday (Aza – 10, 15 and 20 μM; TSA – 0.5 μM). E. As for D except using a stable clone with the late promoter.