title: Thyroid hormone receptor monomer, homodimer, and heterodimer (with retinoid-X receptor) contact different nucleotide sequences in thyroid hormone response elements.
abstract: Thyroid hormone receptors (TRs) bind as monomers, homodimers, and heterodimers with nuclear proteins such as retinoid-X receptors (RXRs) to thyroid hormone response elements (TREs). However, it is not known which nucleotides each TR complex contacts in a particular TRE. To identify the precise contact sites on a synthetic DR4 (TRE half-sites arranged as a direct repeat with a four-nucleotide spacer) and a chick lysoenzyme TRE, F2 (half-sites arranged as an inverted palindrome with a six-nucleotide spacer), for various TR complexes, mobility shift assays, and dimethylsulfate and KMnO4 DNA modification interference assays were employed. First, TR alpha monomer bound to the downstream half-site of these TREs, whereas TR alpha homodimer bound to both half-sites. TR alpha/RXR alpha heterodimer also bound to both half-sites, but "preferred" to contact the down-stream half-site. Second, the specific flanking and spacing sequences of DR4 influenced the contact sites and the binding of TR alpha monomer and homodimer, but not TR alpha/RXR alpha heterodimer. Finally, cotransfection studies, using reporter plasmids containing DR4 or F2 in both orientations with respect to the basal promoter, provide evidence that preferential contact with the down-stream half-site by TR/RXR heterodimer may be important for maximal transcriptional activation.
authors.affiliation: Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115.
authors.forename: M
authors.initials: M
authors.lastname: Ikeda
authors.forename: M
authors.initials: M
authors.lastname: Rhee
authors.forename: W W
authors.initials: WW
authors.lastname: Chin
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000032:analysis / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation; D008745:Methylation; D008969:Molecular Sequence Data; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D047488:Retinoid X Receptors; D014157:Transcription Factors; D015533:Transcriptional Activation
chemical_list: D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D047488:Retinoid X Receptors; D014157:Transcription Factors; D004247:DNA