FIG. 3.

Reversal of p300 repression of Myc by E1A is dependent on E1A binding to p300. Rat12 cells were transfected with a Myc promoter-reporter construct containing upstream 640-bp promoter sequences linked to a luciferase promoter-reporter construct (del6), as described in Materials and Methods, along with p300 and E1A expression plasmids as shown. The vector DNA was included wherever appropriate to maintain a constant DNA concentration. After overnight incubation with normal medium, cells were serum starved for 36 h and harvested and the luciferase (Luc) activities quantified. Luciferase units are shown for 5 μg of protein after normalization with Renilla luciferase activity. Samples represented by bars 3, 4, and 5 contained 0.25, 0.5, and 1.0 μg E1A plasmids, respectively. The experiment was repeated at least three times. Each experiment was carried out in triplicate, and the mean values ± standard deviations are shown.