title: Functional analyses of an LXXLL motif in nuclear receptor corepressor (N-CoR).
abstract: Transcriptional repression is a major regulatory mechanism in cell differentiation, organogenesis, and oncogenesis. Two repressors of ligand-dependent transcription factors, nuclear receptor corepressor (N-CoR) and the related protein SMRT were identified as a silencing mediator for thyroid hormone receptor beta and as a silencing mediator for retinoic acid and thyroid hormone receptors, respectively. Nuclear receptor coactivators such as steroid receptor coactivator-1 (SRC-1) contain multiple LXXLL motifs, which are essential and sufficient for its ligand-dependent interaction with nuclear receptors. N-CoR also has an LXXLL motif, located between repressor domains 1 and 2, and conserved between mouse and man. In contrast, SMRT lacks this motif. This paper describes functional implications of the LXXLL motif in N-CoR. A 57-amino acid portion of N-CoR containing the LDNLL sequence (N-CoR(LDNLL)) fused to GST interacted with retinoic acid receptor alpha (RARalpha) and thyroid hormone receptor beta (TRbeta) in vitro. Similarly, [(35)S-methionine]N-CoR(LDNLL) interacted with a RARalpha fusion protein. N-CoR(LDNLL) also bound to RARalpha in vivo as determined in mammalian one-hybrid system in transfected CV-1 cells and by two-hybrid assays in bacteria. The interaction with RARalpha in vitro and in vivo was specific as determined by mutation of the sequence LDNLL to LDNAA. Our data suggest that the LDNLL motif in N-CoR has functional significance because it mediates interaction with nuclear receptors such as RARalpha and TRbeta.
authors.affiliation: Department of Biomedicine and Surgery, Division of Cell Biology, Linköping University, S-58185 Linköping, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Loinder
authors.forename: Mats
authors.initials: M
authors.lastname: Söderström
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D051548:Histone Acetyltransferases; D006801:Humans; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000502:physiology*; D056971:Nuclear Receptor Co-Repressor 1; D056985:Nuclear Receptor Co-Repressor 2; D056920:Nuclear Receptor Coactivator 1; D017434:Protein Structure, Tertiary; D018168:Receptors, Retinoic Acid / Q000502:physiology*; D011988:Receptors, Thyroid Hormone / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012097:Repressor Proteins / Q000502:physiology*; D000072482:Retinoic Acid Receptor alpha; D017386:Sequence Homology, Amino Acid; D037042:Thyroid Hormone Receptors beta; D015534:Trans-Activators / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology*; D020798:Two-Hybrid System Techniques
chemical_list: D004268:DNA-Binding Proteins; D008024:Ligands; C539127:NCOR1 protein, human; C539130:NCOR2 protein, human; C539128:Ncor1 protein, mouse; C539131:Ncor2 protein, mouse; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D056985:Nuclear Receptor Co-Repressor 2; C000607071:RARA protein, human; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D000072482:Retinoic Acid Receptor alpha; D037042:Thyroid Hormone Receptors beta; D015534:Trans-Activators; D014157:Transcription Factors; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1