Figure 6.

Sequences immediately upstream of the transcriptional initiation site are sufficient for repression of p21^CIP1 by c-Myc. (A) Diagram of the p21^CIP1 promoter illustrating regions bound by some of the major regulatory proteins, as well as the TGFβ-responsive element. The TATA box, located at −45 bp relative to start of transcription, is indicated by the black bar. The arrow indicates the site of transcriptional initiation. (B) Diagrams of 5′ deletion constructs of p21^CIP1 promoter. Numbers in top three diagrams indicate 5′ end of the deletion construct relative to the transcription start site. The last diagram depicts deletion p21 pSmaΔ2, in which only the region from −114 to −62, including the TGFβ-responsive element, is deleted. (C) Luciferase activity for each promoter deletion construct depicted in B was determined, and fold luciferase activity in cells cotransfected with c-Myc expression vector (dark solid bars) was determined as compared to cells cotransfected with empty CMV vector (white solid bars). Error bars represent the standard deviation of the average of three independent experiments.