title: In vivo interaction of steroid receptor coactivator (SRC)-1 and the activation function-2 domain of the thyroid hormone receptor (TR) beta in TRbeta E457A knock-in and SRC-1 knockout mice.
abstract: The activation function-2 (AF-2) domain of the thyroid hormone (TH) receptor (TR)-beta is a TH-dependent binding site for nuclear coactivators (NCoA), which modulate TH-dependent gene transcription. In contrast, the putative AF-1 domain is a TH-independent region interacting with NCoA. We determined the specificity of the AF-2 domain and NCoA interaction by evaluating thyroid function in mice with combined disruption of the AF-2 domain in TRbeta, due to a point mutation (E457A), and deletion of one of the NCoAs, steroid receptor coactivator (SRC)-1. The E457A mutation was chosen because it abolishes NCoA recruitment in vitro while preserving normal TH binding and corepressor interactions resulting in resistance to TH. At baseline, disruption of SRC-1 in the homozygous knock-in (TRbeta(E457A/E457A)) mice worsened the degree of resistance to TH, resulting in increased serum T(4) and TSH. During TH deprivation, disruption of AF-2 and SRC-1 resulted in a TSH rise 50% of what was seen when AF-2 alone was removed, suggesting that SRC-1 was interacting outside of the AF-2 domain. Therefore, 1) during TH deprivation, SRC-1 is necessary for activating the hypothalamic-pituitary-thyroid axis; 2) ligand-dependent repression of TSH requires an intact AF-2; and 3) SRC-1 may interact with the another region of the TRbeta or the TRalpha to regulate TH action in the pituitary. This report demonstrates the dual interaction of NCoA in vivo: the TH-independent up-regulation possibly through another domain and TH-dependent down-regulation through the AF-2 domain.
authors.affiliation: Department of Medicine, Committees on Genetics, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Manuela
authors.initials: M
authors.lastname: Alonso
authors.forename: Charles
authors.initials: C
authors.lastname: Goodwin
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Liao
authors.forename: Tania
authors.initials: T
authors.lastname: Ortiga-Carvalho
authors.forename: Danielle S
authors.initials: DS
authors.lastname: Machado
authors.forename: Fredric E
authors.initials: FE
authors.lastname: Wondisford
authors.forename: Samuel
authors.initials: S
authors.lastname: Refetoff
authors.forename: Roy E
authors.initials: RE
authors.lastname: Weiss
mesh_terms: D000818:Animals; D051548:Histone Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D056920:Nuclear Receptor Coactivator 1; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013960:Thyroid Function Tests; D037021:Thyroid Hormone Receptors alpha / Q000235:genetics / Q000378:metabolism; D037042:Thyroid Hormone Receptors beta / Q000235:genetics / Q000378:metabolism*; D013963:Thyroid Hormones / Q000097:blood / Q000172:deficiency / Q000494:pharmacology; D013972:Thyrotropin / Q000097:blood / Q000235:genetics; D013974:Thyroxine / Q000097:blood; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014284:Triiodothyronine / Q000494:pharmacology
chemical_list: D037021:Thyroid Hormone Receptors alpha; D037042:Thyroid Hormone Receptors beta; D013963:Thyroid Hormones; D014157:Transcription Factors; D014284:Triiodothyronine; D013972:Thyrotropin; D051548:Histone Acetyltransferases; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1; D013974:Thyroxine