E2F INHIBITS TRANSCRIPTIONAL ACTIVATION BY THE RETINOIC ACID RECEPTOR

The E2F transcription factors are thought to mediate growth-inducing s ignals by elevating transcription of genes required for cell prolifera tion. Retinoic acid receptors (RARs) mediate retinoic acid (RA)-induce d expression of genes with roles in cell differentiation. We found tha t E2F-1 inhibited expression from RA-responsive promoters. This inhibi tion was specific to transcription mediated by RARs. We found no direc t interaction between the E2F-1 protein and the RA response element in DNA or the RAR proteins. Our evidence suggests that E2F-1 reduces exp ression from RA-inducible promoters by interacting with an unidentifie d coactivator(s) that is required by the RARs.