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Interactions of nuclear receptor coactivator/corepressor proteins with the aryl hydrocarbon receptor complex
T A Nguyen1, D Hoivik, J E Lee
1Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas, 77843-4466, USA.
Abstract:
MCF-7 human breast cancer cells express the aryl hydrocarbon receptor (AhR), and treatment with AhR agonists such as 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) inhibits estrogen receptor (ER)-mediated responses. This study investigates physical and functional interactions of the AhR complex with a prototypical coactivator (estrogen receptor associating protein 140, ERAP 140) and corepressor (silencing mediator for retinoic acid and thyroid hormone receptor, SMRT) for ER and other members of the nuclear receptor superfamily. The AhR, AhR nuclear translocator (Arnt), and AhR/Arnt proteins were coimmunoprecipitated with 35S-ERAP 140 and 35S-SMRT and, in gel mobility shift assays, AhR/Arnt binding to 32P-dioxin response element (DRE) was enhanced by ERAP-140 and inhibited by SMRT; supershifted bands were not observed. In transactivation assays, coactivator and corepressor proteins enhanced or inhibited AhR-mediated gene expression; however, these responses varied with the amount of coactivator/corepressor expression. These results confirmed functional and physical interactions of AhR/Arnt with ERAP 140 and SMRT in breast cancer cells.
Insights
The aryl hydrocarbon receptor (AhR) interacts with coactivator ERAP 140 and corepressor SMRT in breast cancer cells. These interactions modulate estrogen receptor activity and AhR-mediated gene expression.
Area of Science:
- Molecular biology
- Cell biology
- Endocrinology
Background:
- MCF-7 human breast cancer cells express the aryl hydrocarbon receptor (AhR).
- AhR agonists, like TCDD, inhibit estrogen receptor (ER)-mediated responses.
- Investigating interactions with coactivators and corepressors is crucial for understanding nuclear receptor function.
Purpose of the Study:
- To investigate physical and functional interactions of the AhR complex with ERAP 140 and SMRT.
- To determine the role of these interactions in ER and other nuclear receptor superfamily members' function.
- To elucidate the mechanisms by which AhR modulates ER activity in breast cancer cells.
Main Methods:
- Coimmunoprecipitation assays to detect protein interactions.
- Gel mobility shift assays to assess DNA binding.
- Transactivation assays to measure gene expression modulation.
Main Results:
- AhR, Arnt, and AhR/Arnt proteins were coimmunoprecipitated with ERAP 140 and SMRT.
- ERAP-140 enhanced AhR/Arnt binding to the DRE, while SMRT inhibited it.
- Coactivator and corepressor proteins modulated AhR-mediated gene expression in a dose-dependent manner.
Conclusions:
- Confirmed functional and physical interactions between AhR/Arnt and ERAP 140/SMRT in breast cancer cells.
- ERAP 140 and SMRT play significant roles in regulating AhR activity.
- These findings provide insights into the complex regulatory network of nuclear receptors in breast cancer.