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CIR, a corepressor linking the DNA binding factor CBF1 to the histone deacetylase complex
1Molecular Virology Laboratories, Department of Pharmacology and Molecular Sciences and Department of Oncology, Johns Hopkins School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA.
Summary
CBF1 DNA binding factors mediate gene expression. A novel corepressor, CBF1 interacting corepressor (CIR), links CBF1 to histone deacetylase, revealing a key mechanism in transcriptional repression.
Area of Science:
- Molecular Biology
- Epigenetics
- Cell Signaling
Background:
- CBF1 is a CSL family DNA binding factor involved in Notch signaling and Epstein-Barr virus (EBV) functions.
- Notch signaling regulates cell-fate decisions, with its intracellular domain (NotchIC) interacting with CBF1.
- EBV protein EBNA2 mimics NotchIC to activate gene expression by targeting CBF1.
Purpose of the Study:
- To elucidate the mechanism of CBF1-mediated transcriptional repression.
- To identify and characterize novel proteins interacting with CBF1 during repression.
Main Methods:
- Investigated CBF1 interactions using biochemical assays.
- Utilized mutant CBF1 proteins to assess the functional role of interactions.
- Employed Gal4 fusion protein assays to evaluate the repressive activity of identified interactors.
Main Results:
- Identified a novel corepressor, CBF1 interacting corepressor (CIR), that specifically binds to CBF1.
- Demonstrated that CIR is evolutionarily conserved, with a homolog in Caenorhabditis elegans.
- Showed that CBF1 mutants unable to bind CIR lose their repressive function.
- CIR directly binds to histone deacetylase (HDAC) and SAP30, acting as a molecular bridge.
Conclusions:
- CIR is essential for CBF1-mediated transcriptional repression.
- CIR functions as a linker, connecting CBF1 to the histone deacetylase complex.
- This interaction highlights a conserved mechanism for epigenetic gene regulation involving CBF1.