Fig. 2. VPA relieves HDAC-mediated transcriptional repression. (A) HeLa cells were co-transfected with a UAS-TK-luciferase reporter, an SV40 β-Gal control reporter and vectors expressing either the GAL4 DNA-binding domain (amino acids 1–147) or GAL4 fusions of N-CoR (amino acids 1–2453) or the ligand-binding domains of TRβ (amino acids 165–456) with or without TRIAC, or PPARδ (amino acids 138–440) with or without cPGI₂, respectively. At 24 h after transfection, cells were treated with trapoxin (10 nM), TSA (100 nM) or VPA (1 mM) for 16–20 h. Subsequently, cells were harvested and luciferase and β-galactosidase activities were measured. Results are represented as fold repression relative to GAL4. Values are means ± SD from triplicate determinations in two independent experiments. (B) Phoenix cells were co-transfected with the indicated expression vectors, using a luciferase reporter based on the human RARβ2 promoter (de Thé et al., 1990). VPA (1 or 3 mM) was added 18 h after transfections, and cells were analyzed for reporter activity after an additional 24 h.