title: Purification and functional characterization of the human N-CoR complex: the roles of HDAC3, TBL1 and TBLR1.
abstract: Corepressors N-CoR and SMRT participate in diverse repression pathways and exist in large protein complexes including HDAC3, TBL1 and TBLR1. However, the roles of these proteins in SMRT-N-CoR complex function are largely unknown. Here we report the purification and functional characterization of the human N-CoR complex. The purified N-CoR complex contains 10-12 associated proteins, including previously identified components and a novel actin-binding protein IR10. We show that TBL1/TBLR1 associates with N-CoR through two independent interactions: the N-terminal region and the C-terminal WD-40 repeats interact with the N-CoR RD1 and RD4 region, respectively. In vitro, TBL1/TBLR1 bind histones H2B and H4, and, importantly, repression by TBL1/TBLR1 correlates with their interaction with histones. By using specific small interference RNAs (siRNAs), we demonstrate that HDAC3 is essential, whereas TBL1 and TBLR1 are functionally redundant but essential for repression by unliganded thyroid hormone receptor. Together, our data reveal the roles of HDAC3 and TBL/TBLR1 and provide evidence for the functional importance of histone interaction in repression mediated by SMRT-N-CoR complexes.
authors.affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
authors.forename: Ho-Geun
authors.initials: HG
authors.lastname: Yoon
authors.forename: Doug W
authors.initials: DW
authors.lastname: Chan
authors.forename: Zhi-Qing
authors.initials: ZQ
authors.lastname: Huang
authors.forename: Jiwen
authors.initials: J
authors.lastname: Li
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Fondell
authors.forename: Jun
authors.initials: J
authors.lastname: Qin
authors.forename: Jiemin
authors.initials: J
authors.lastname: Wong
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification; D006367:HeLa Cells; D006655:Histone Deacetylases / Q000737:chemistry / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry; D009687:Nuclear Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D034741:RNA, Small Interfering / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D011988:Receptors, Thyroid Hormone / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015293:Transducin / Q000737:chemistry / Q000378:metabolism*; D000099186:Histone Deacetylase 3
chemical_list: D004268:DNA-Binding Proteins; D006655:Histone Deacetylases; D006657:Histones; D008840:Microfilament Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D021122:Protein Subunits; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D011988:Receptors, Thyroid Hormone; D011994:Recombinant Proteins; D012097:Repressor Proteins; D015293:Transducin; D000099186:Histone Deacetylase 3; C119542:TBL1X protein, human; C473691:TBL1XR1 protein, human; C072061:coronin proteins