Both corepressor proteins SMRT and N-CoR exist in large protein complexes containing HDAC3.
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.
Pubmed ID: 10944117 RIS Download
Animals | Blotting, Western | Cell Nucleus | Chromatography, Affinity | Chromatography, Gel | Chromatography, Ion Exchange | Cloning, Molecular | DNA-Binding Proteins | HeLa Cells | Histone Deacetylases | Humans | Ligands | Nuclear Proteins | Nuclear Receptor Co-Repressor 1 | Nuclear Receptor Co-Repressor 2 | Oocytes | Plasmids | Protein Binding | Receptors, Retinoic Acid | Receptors, Thyroid Hormone | Recombinant Proteins | Repressor Proteins | Transcription, Genetic | Two-Hybrid System Techniques | Xenopus