FIG. 2.

C/EBPα down-regulates c-Myc promoter activity. (A) The 6.5-kb c-Myc promoter and indicated 5′ deletions were cloned into the pXP2 luciferase reporter vector. (B) CV-1 cells were cotransfected with 200 ng of the indicated reporter gene and increasing amounts of C/EBPα expression plasmid (nanograms). Control transfection experiments indicated that C/EBPα had no effect on the pXP2 luciferase reporter vector (data not shown). (C) As a positive control for C/EBPα transactivation, CV-1 cells were cotransfected with the G-CSF receptor reporter gene containing four C/EBPα binding sites (pTK-G-CSFr). All transfection groups were normalized with a Renilla luciferase vector as an internal control. Results represent the percentages of luciferase activity with 0 ng of C/EBPα (vector alone) set to 100% activity. Results are given as the averages of at least three independent experiments, and error bars represent the standard errors of the means.