FIG. 4.

The c-Myc 3′ enhancer activates transcription in a position- and orientation-independent manner. (Left) Diagram of reporter constructs with the SV40 promoter represented as green rectangles and the firefly luciferase gene shown as yellow rectangles. The rectangles labeled c-Myc 3′ EN (REV) correspond to the 615 bp c-Myc 3′ element inserted in reverse orientation relative to the SV40 promoter. DNA spacers corresponding to 1-kb fragments from the pBluescript plasmid are indicated. The firefly luciferase reporter plasmids and a control plasmid expressing Renilla luciferase were transfected into HCT116 cells. Luciferase levels were measured 24 h following transfection. Firefly luciferase values were normalized to Renilla luciferase values, and the data are represented as the change in expression relative to levels in cells transfected with the pGL3-promoter vector and control Renilla vector. Error bars indicate standard deviations.