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Differential regulation of glucocorticoid receptor transcriptional activation via AF-1-associated proteins
A B Hittelman1, D Burakov, J A Iñiguez-Lluhí
1Department of Microbiology and the Kaplan Comprehensive Cancer Center, NYU School of Medicine, 550 First Avenue, New York, NY 10016, USA.
Abstract:
The hormone-activated glucocorticoid receptor (GR), through its N- and C-terminal transcriptional activation functions AF-1 and AF-2, controls the transcription of target genes presumably through interaction(s) with transcriptional regulatory factors. Utilizing a modified yeast two-hybrid approach, we have identified the tumor susceptibility gene 101 (TSG101) and the vitamin D receptor-interacting protein 150 (DRIP150) as proteins that interact specifically with a functional GR AF-1 surface. In yeast and mammalian cells, TSG101 represses whereas DRIP150 enhances GR AF-1-mediated transactivation. Thus, GR AF-1 is capable of recruiting both positive and negative regulatory factors that differentially regulate GR transcriptional enhancement. In addition, we show that another member of the DRIP complex, DRIP205, interacts with the GR ligand binding domain in a hormone-dependent manner and facilitates GR transactivation in concert with DRIP150. These results suggest that DRIP150 and DRIP205 functionally link GR AF-1 and AF-2, and represent important mediators of GR transcriptional enhancement.
Insights
Glucocorticoid receptor (GR) transcriptional regulation involves interactions with TSG101 and DRIP150 proteins. These factors, including DRIP205, modulate GR
Area of Science:
- Molecular Biology
- Endocrinology
- Gene Regulation
Background:
- The glucocorticoid receptor (GR) is a key regulator of gene transcription.
- GR's transcriptional activity is mediated by its N-terminal (AF-1) and C-terminal (AF-2) activation functions.
- Understanding GR's interactions with regulatory factors is crucial for deciphering its function.
Purpose of the Study:
- To identify proteins interacting with the GR AF-1 activation function.
- To elucidate the roles of identified interacting proteins in GR-mediated transactivation.
- To investigate the functional linkage between GR's AF-1 and AF-2 domains.
Main Methods:
- Modified yeast two-hybrid screening to identify GR AF-1 interacting proteins.
- Co-transfection assays in yeast and mammalian cells to assess transactivation.
- Hormone-dependent interaction assays for DRIP205 and GR ligand binding domain.
Main Results:
- TSG101 and DRIP150 were identified as specific interactors of the GR AF-1 surface.
- TSG101 demonstrated repression, while DRIP150 showed enhancement of GR AF-1 activity.
- DRIP205 interacted with the GR ligand binding domain and, with DRIP150, facilitated GR transactivation.
Conclusions:
- GR AF-1 can recruit both positive (DRIP150) and negative (TSG101) regulatory factors.
- DRIP150 and DRIP205 link the GR AF-1 and AF-2 activation functions.
- These DRIP complex members are critical mediators of glucocorticoid receptor transcriptional enhancement.