Related Experiment Video
Updated: Aug 29, 2026

Prediction and Validation of Gene Regulatory Elements Activated During Retinoic Acid Induced Embryonic Stem Cell Differentiation
Published on: June 21, 2016
Role of mediator in transcriptional activation by the aryl hydrocarbon receptor
Song Wang1, Kai Ge, Robert G Roeder
1Department of Pathology and Laboratory Medicine, Jonsson Comprehensive Cancer Center, Molecular Biology Institute, University of California, Los Angeles, California 90095, USA.
Abstract:
The aryl hydrocarbon receptor (AHR) binds many aromatic hydrocarbon compounds and mediates their carcinogenesis. We demonstrate that the endogenous AHR physically associates with the endogenous TRAP/DRIP/ARC/Mediator complex in a ligand-dependent manner. The Med220 subunit, which is known to interact with several nuclear hormone receptors through its LXXLL motifs, potentiates AHR-dependent reporter gene activity in an LXXLL-independent manner. Depletion of Med220 substantially reduces endogenous AHR-mediated transcription from the mouse cytochrome P4501A1 gene (CYP1A1). Both Med220 and CDK8 (another subunit of TRAP/DRIP/ARC/Mediator) are recruited to the CYP1A1 enhancer in a TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin)-dependent fashion in vivo, and Med220 LXXLL motifs are not required. Med220 rapidly and persistently associates with the enhancer but not the promoter of the CYP1A1 gene after TCDD treatment with similar kinetics as AHR and the coactivators p300 and p/CIP. Our findings demonstrate a novel role for Med220 in AHR-regulated transcription that differs mechanistically from its role in transcriptional regulation by other previously studied transcription factors.
Related Concept Videos
Co-activators and Co-repressors
Co-activators and Co-repressors
RNA Polymerase II Accessory Proteins
Eukaryotic Transcription Activators
The binding domains are capable of recognizing and interacting with regulatory sequences on the DNA. These domains are...
Master Transcription Regulators
Master Transcription Regulators
