p300 is involved in retinoblastoma gene promoter induction by MyoD
M. Caruso1, B. Polikar1, P. Fuschi2, C. Cenciarelli2, W. Yuan3, A. Giordano3, and A. Felsani2,4
1Istituto Biologia Cellulare and 2Istituto
Tecnologie Biomediche, CNR, Rome, Italy;
3Jefferson Cancer Institute, Thomas Jefferson
University, Philadelphia, USA;
4Istituto Regina Elena, Rome, Italy
Abstract
We have demonstrated that
the muscle-specific transcription factor MyoD induces the retinoblastoma
gene (Rb1) promoter. In the present work, we demonstrate that the
MyoD-mediated induction of the Rb1 promoter does not require new protein
synthesis. Moreover, we identified the minimal Rb1 promoter region
targeted by MyoD as a 50-bp sequence containing the binding sites of three
families of transcription factors: E2F, ATF/CREB and E4TF1. Site-directed
mutagenesis of these sites indicated that: 1. the E4TF1 binding site is
required for the promoter basal activity; 2. the ATF/CREB site is important
for both the basal and MyoD-induced promoter activity; 3. the E2F site
modulates the basal promoter activity
By means of band shift
experiments, we determined that the transcription factor CREB binds the
ATF/CREB site present in the Rb1 promoter and that both the CBP and p300
transcriptional coactivators participate to the DNA-bound complex.
These results togather with our previous finding that MyoD and p300 can
physically and functionally interact, suggest that MyoD might induce the
activity of CREB through binding to the p300 transcriptional coactivator.