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Trans-repression of beta-catenin activity by nuclear receptors
Salimuddin Shah1, Andreas Hecht, Richard Pestell
1The Lombardi Cancer Center and the Department of Oncology, Georgetown University School of Medicine, Washington, DC 20057, USA.
Abstract:
The signaling/oncogenic activity of beta-catenin can be repressed by the activation of nuclear receptors such as the vitamin A, vitamin D, and androgen receptors. Although these receptors directly interact with beta-catenin and can sequester it away from its transcription factor partner T-cell factor, it is not known if this is the mechanism of trans-repression. Using several different promoter constructs and nuclear receptors and mammalian two-hybrid and mutation analyses we now show that interaction with the co-activator, p300, underlies the trans-repression of beta-catenin signaling by nuclear receptors and their ligands.
Insights
Nuclear receptors repress beta-catenin signaling by interacting with the co-activator p300. This interaction, not T-cell factor sequestration, is key to the trans-repression mechanism, impacting oncogenic pathways.
Area of Science:
- Molecular Biology
- Cell Signaling
- Cancer Research
Background:
- Beta-catenin signaling is crucial for cell growth and is often dysregulated in cancer.
- Nuclear receptors, including those for vitamin A, D, and androgens, can inhibit beta-catenin activity.
- The precise mechanism by which nuclear receptors repress beta-catenin signaling remains unclear.
Purpose of the Study:
- To elucidate the mechanism of trans-repression of beta-catenin signaling by nuclear receptors.
- To determine if T-cell factor sequestration or interaction with co-activators mediates this repression.
Main Methods:
- Utilized various promoter constructs and nuclear receptors.
- Employed mammalian two-hybrid assays.
- Conducted mutation analyses to investigate protein interactions.
Main Results:
- Demonstrated that nuclear receptors directly interact with the co-activator p300.
- Showed that this interaction with p300 underlies the trans-repression of beta-catenin signaling.
- Provided evidence against T-cell factor sequestration as the primary mechanism.
Conclusions:
- The interaction between nuclear receptors and the co-activator p300 is the primary mechanism for repressing beta-catenin signaling.
- This finding clarifies a key regulatory pathway in cell signaling and cancer.
- Highlights the role of co-activator recruitment in nuclear receptor-mediated gene repression.