Characterization of receptor interaction and transcriptional repression by the corepressor SMRT.
SMRT (silencing mediator of retinoic acid and thyroid hormone receptor) and N-CoR (nuclear receptor corepressor) are two related transcriptional corepressors that contain separable domains capable of interacting with unliganded nuclear receptors and repressing basal transcription. To decipher the mechanisms of receptor interaction and transcriptional repression by SMRT/N-CoR, we have characterized protein-protein interacting surfaces between SMRT and nuclear receptors and defined transcriptional repression domains of both SMRT and N-CoR. Deletional analysis reveals two individual nuclear receptor domains necessary for stable association with SMRT and a C-terminal helix essential for corepressor dissociation. Coordinately, two SMRT domains are found to interact independently with the receptors. Functional analysis reveals that SMRT contains two distinct repression domains, and the corresponding regions in N-CoR also repress basal transcription. Both repression domains in SMRT and N-CoR interact weakly with mSin3A, which in turn associates with a histone deacetylase HDAC1 in a mammalian two-hybrid assay. Far-Western analysis demonstrates a direct protein-protein interaction between two N-CoR repression domains with mSin3A. Finally we demonstrate that overexpression of full-length SMRT further represses basal transcription from natural promoters. Together, these results support a role of SMRT/N-CoR in corepression through the utilization of multiple mechanisms for receptor interactions and transcriptional repression.
Li
H
H
Department of Pharmacology and Molecular Toxicology, University of Massachusetts Medical School, Worcester 01655-0126, USA.
Leo
C
C
Schroen
D J
DJ
Chen
J D
JD
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D056971:Nuclear Receptor Co-Repressor 1; D056985:Nuclear Receptor Co-Repressor 2; D011401:Promoter Regions, Genetic / Q000187:drug effects; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D000072482:Retinoic Acid Receptor alpha; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
D004268:DNA-Binding Proteins; C539127:NCOR1 protein, human; C539130:NCOR2 protein, human; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D056985:Nuclear Receptor Co-Repressor 2; C000607071:RARA protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D012097:Repressor Proteins; D000072482:Retinoic Acid Receptor alpha