E2F-6 is a transcriptional repressor. (A) A luciferase reporter plasmid with three E2F consensus binding sites (wt) or mutated binding sites (mut) was cotransfected with 1 μg of E2F-6 expression plasmid or empty vector. (B) A luciferase reporter with the E2F-1 promoter was cotransfected with 1 μg of E2F-6 expression plasmid, 1 μg of E2F-6E68 (E68, DNA-binding mutant, see Fig. 4), or 1 μg of empty vector (ctrl). (C) Five micrograms of E2F-reporter plasmid was cotransfected with empty vector or 1 μg of pCDNA-E2F-4 and 0.5 or 2.5 μg of E2F-6 expression plasmid, as indicated. In all transfections, 0.2 μg of CMV-β-gal was cotransfected as internal control, and luiciferase activity was normalized to β-galactosidase activity.