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Published on: December 6, 2013
Developmentally essential protein flightless I is a nuclear receptor coactivator with actin binding activity
Young-Ho Lee1, Hugh D Campbell, Michael R Stallcup
1Department of Pathology, University of Southern California, Los Angeles, California 90089-9092, USA.
Molecular and Cellular Biology
|February 18, 2004
Summary
Flightless I (Fli-I) enhances nuclear receptor (NR) gene transcription by interacting with coactivator complexes. This protein is crucial for hormone-stimulated gene expression and may link NR coactivators to actin-based structures.
Area of Science:
- Molecular Biology
- Gene Regulation
- Protein Interactions
Background:
- Nuclear receptors (NRs) activate gene transcription via coactivator complexes.
- Key coactivators include p160 proteins, histone acetyltransferases (p300/CBP), and CARM1.
- CARM1's coactivator function depends on its methyltransferase activity and binding partners.
Purpose of the Study:
- To identify novel proteins that bind to CARM1.
- To investigate the role of Flightless I (Fli-I) in NR-mediated transcription.
- To elucidate the mechanism by which Fli-I modulates coactivator complex function.
Main Methods:
- Yeast two-hybrid screening to identify CARM1-interacting proteins.
- Co-transfection assays to assess NR transcriptional activity.
- Small interfering RNA (siRNA) to reduce endogenous Fli-I levels.
- Chromatin immunoprecipitation (ChIP) to detect protein recruitment to promoters.
Main Results:
- Yeast two-hybrid screening identified Flightless I (Fli-I) as a CARM1-binding protein.
- Fli-I synergistically enhanced NR function with CARM1 and GRIP1, dependent on CARM1's methyltransferase activity.
- Endogenous Fli-I was recruited to the estrogen-responsive pS2 promoter and was essential for hormone-stimulated transcription.
- Fli-I's actin-binding domain was important for its coactivator function.
Conclusions:
- Flightless I (Fli-I) is a novel coactivator that enhances nuclear receptor activity.
- Fli-I's function is dependent on CARM1's methyltransferase activity and its interaction with p160 coactivators.
- Fli-I may bridge coactivator complexes to actin-related proteins, facilitating transcriptional activation.
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