FIG. 3.
Transcriptional activation of p21Cip1 and TrkB by RA requires E-box elements. (A) Schematic representation of the p21Cip1 and TrkB promoter fusions to luciferase used in the present study (see Materials and Methods), showing wild-type and mutated E-box and RARE regulatory sequences. (B) Transcriptional activation of the p21Cip1 and TrkB promoter constructs by RA. Normalized expression levels produced by the respective promoter constructs after 5 days of RA treatment were made relative to those obtained in cycling cells. Average values and standard deviations obtained from three independent transfection experiments are shown. (C) Transcriptional activation driven by a three synthetic E-box construct (E-box synthetic), the wild-type p21Cip1 promoter, and a shorter fragment of the p21Cip1 promoter containing the E-box elements (p21Cip1 E-box region) in cells treated with RA for 5 days. Normalized expression levels were obtained as in panel B.