Abstract
We present evidence that both corepressors SMRT and N-CoR exist in large protein complexes with estimated sizes of 1.5-2 MDa in HeLa nuclear extracts. Using a combination of conventional and immunoaffinity chromatography, we have successfully isolated a SMRT complex and identified histone deacetylase 3 (HDAC3) and transducin (beta)-like I (TBL1), a WD-40 repeat-containing protein, as the subunits of the purified SMRT complex. We show that the HDAC3-containing SMRT and N-CoR complexes can bind to unliganded thyroid hormone receptors (TRs) in vitro. We demonstrate further that in Xenopus oocytes, both SMRT and N-CoR also associate with HDAC3 in large protein complexes and that injection of antibodies against HDAC3 or SMRT/N-CoR led to a partial relief of repression by unliganded TR/RXR. These findings thus establish both SMRT and N-CoR complexes as bona fide HDAC-containing complexes and shed new light on the molecular pathways by which N-CoR and SMRT function in transcriptional repression.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Blotting, Western
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Cell Nucleus / metabolism
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Chromatography, Affinity
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Chromatography, Gel
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Chromatography, Ion Exchange
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Cloning, Molecular
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / isolation & purification
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DNA-Binding Proteins / metabolism*
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HeLa Cells
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Histone Deacetylases / chemistry
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Histone Deacetylases / metabolism*
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Humans
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Ligands
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Nuclear Proteins / chemistry
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Nuclear Receptor Co-Repressor 1
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Nuclear Receptor Co-Repressor 2
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Oocytes / metabolism
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Plasmids / metabolism
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Protein Binding
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Receptors, Retinoic Acid / metabolism
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Receptors, Thyroid Hormone / metabolism
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Recombinant Proteins / metabolism
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Repressor Proteins / chemistry
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Repressor Proteins / genetics
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Repressor Proteins / isolation & purification
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Repressor Proteins / metabolism*
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Transcription, Genetic
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Two-Hybrid System Techniques
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Xenopus
Substances
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DNA-Binding Proteins
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Ligands
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NCOR1 protein, human
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NCOR2 protein, human
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Nuclear Proteins
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Nuclear Receptor Co-Repressor 1
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Nuclear Receptor Co-Repressor 2
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Receptors, Retinoic Acid
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Receptors, Thyroid Hormone
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Recombinant Proteins
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Repressor Proteins
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Histone Deacetylases
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histone deacetylase 3