Transcriptional Activation of the Nuclear Receptor Corepressor RIP140 by Retinoic Acid: A Potential Negative-Feedback Regulatory Mechanism

Through the use of microarray analysis it was discovered that the nuclear receptor coregulator, receptor interacting protein 140 (RIP140), was induced early during all-trans retinoic acid (RA)-induced differentiation of human embryonal carcinoma cells. A rapid, fourfold induction of RIP140 mRNA was detected within 3 h of RA treatment in human embryonal carcinoma and MCF-7 human breast cancer cells. RIP140 protein levels were induced within 6 h of RA treatment. The RA induction of RIP140 mRNA did not require de novo protein synthesis, consistent with RIP140 being a direct transcriptional target of retinoid receptors. Promoter/enhancer elements directly upstream of the RIP140 coding region supported RA-induced transcription of a luciferase gene. In addition the ability of overexpressed RIP140 to repress ligand activated retinoid receptors was confirmed. The finding that RIP140 is a direct transcriptional target of RA is one of the first examples of acute transcriptional regulation of a nuclear receptor coactivator or corepressor. These data are consistent with a model by which RA induction of RIP140 supplies a negative feedback signal toward ligand-activated retinoid receptors.