title: Molecular characterization of human thyroid hormone receptor β isoform 4.
abstract: Thyroid hormone exerts a pleiotropic effect on development, differentiation, and metabolism through thyroid hormone receptor (TR). A novel thyroid hormone receptor β isoform (TRβ4) was cloned using PCR from a human pituitary cDNA library as a template. We report here the characterization of TRβ4 from a molecular basis. Temporal expression of TRβ4 during the fetal period is abundant in the brain and kidney, comparable with the adult pattern. Western blot analysis revealed that TRs are ubiquitination labile proteins, while TRβ1 is potentially stable. TRβ1, peroxisome proliferator-activated receptors (PPAR), and vitamin D receptor (VDR), which belong to class II transcription factors that function via the formation of heterodimeric complexes with retinoid X receptor (RXR), were suppressed by TRβ4 in a dose-dependent manner. Thus, TRβ4 exhibits ligand-independent transcriptional silencing, possibly as a substitute for dimerized RXR. In this study, TRβ1 and TRβ4 transcripts were detected in several cell lines. Quantitative RT-PCR assay showed that the expression of TRβ4 in human embryonic carcinoma cells of the testis was suppressed by sex hormone in a reciprocal manner to TRβ1. In contrast, TRβ4 was expressed under a high dose of triiodothyronine (T3) in a reciprocal manner to TRβ1. Finally, in transiently transfected NIH-3T3 cells, green fluorescence protein (GFP)-tagged TRβ4 was mostly nuclear in both the absence and the presence of T3. By mutating defined regions of both TRβs, we found that both TRβ1 and TRβ4 had altered nuclear/cytoplasmic distribution as compared with wild-type, and different to T3 and the nuclear receptor corepressor (NCoR). Thus, site-specific DNA binding is not essential for maintaining TRβs within the nucleus.
authors.affiliation: a Department of Medicine and Clinical Science , Graduate School of Pharmaceutical Sciences, Mukogawa Women's University , Nishinomiya , Japan .|b Division of Endocrinology , Metabolism and Hypertension, Clinical Research Institute for Endocrine and Metabolic Diseases, National Hospital Organization, Kyoto Medical Center , Kyoto , Japan , and.|c Department of Nephrology and Blood Purification , Institute of Biomedical Research and Innovation, Kobe Medical Frontier Center , Kobe , Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Moriyama
authors.affiliation: a Department of Medicine and Clinical Science , Graduate School of Pharmaceutical Sciences, Mukogawa Women's University , Nishinomiya , Japan .|b Division of Endocrinology , Metabolism and Hypertension, Clinical Research Institute for Endocrine and Metabolic Diseases, National Hospital Organization, Kyoto Medical Center , Kyoto , Japan , and.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamamoto
authors.affiliation: a Department of Medicine and Clinical Science , Graduate School of Pharmaceutical Sciences, Mukogawa Women's University , Nishinomiya , Japan .
authors.forename: Kumi
authors.initials: K
authors.lastname: Futawaka
authors.affiliation: a Department of Medicine and Clinical Science , Graduate School of Pharmaceutical Sciences, Mukogawa Women's University , Nishinomiya , Japan .
authors.forename: Asami
authors.initials: A
authors.lastname: Atake
authors.affiliation: c Department of Nephrology and Blood Purification , Institute of Biomedical Research and Innovation, Kobe Medical Frontier Center , Kobe , Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kasahara
authors.affiliation: b Division of Endocrinology , Metabolism and Hypertension, Clinical Research Institute for Endocrine and Metabolic Diseases, National Hospital Organization, Kyoto Medical Center , Kyoto , Japan , and.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tagami
mesh_terms: D000328:Adult; D000818:Animals; D002478:Cells, Cultured; D003001:Cloning, Molecular; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D010902:Pituitary Gland / Q000737:chemistry / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D037042:Thyroid Hormone Receptors beta / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D037042:Thyroid Hormone Receptors beta
keywords: Thyroid hormone receptor β; dominant negative effect; subcellular localization; tissue distribution