Figure 9.
SK residues found within the first helix of the bHLH domain of CeABF-1 help mediate repression of E47 activity. HeLa S3 cells were transiently transfected with 1 µg of (µE5-µE3-µE2)4-Luc reporter vector and different combinations of the E47 expression vector (0.5 µg), FLAG-CeABF-1, and FLAG-CeABF-1 SK-NE expression plasmids (0.25 µg). Twenty-five microliters of Superfect reagent was used for each transfection and equal amounts of protein extract were assayed for firefly luciferase activity. Experiments were performed in triplicate and represent the means of two independent assays. Luciferase activity was normalized to β-galactosidase levels as a control for transfection efficiency. The mean of the firefly luciferase value for E47 + CeABF-1 was 60 248 light units and E47 + CeABF-1 SK-NE was 198 818 light units.