Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The antiarrhythmic drug amiodarone has recently been characterized as the first known thyroid hormone antagonist. Its mode of interaction with the thyroid hormone receptor is therefore of interest. A computational analysis of the conformational flexibility of amiodarone using molecular mechanics and the semiempirical molecular orbital method AM1 has been performed. The molecular mechanics studies show that the low-energy conformations of the benzoylbenzofuran portion of amiodarone can be grouped into 4 distinct classes, while the diethylaminoethoxy side chain is extremely flexible. Conformers representative of the 4 low-energy classes were fitted to an extended thyroid hormone receptor model. Four independent modes in which amiodarone could bind to the thyroid hormone receptor site were evaluated.
J Comput Aided Mol Des 1992 Feb
PMID:Models for the binding of amiodarone to the thyroid hormone receptor. 158 37

Thyroid hormone response elements (T3REs) have been identified in a variety of promoters including those directing expression of rat GH (rGH), alpha-myosin heavy chain (rMHC), and malic enzyme (rME). A detailed biochemical and genetic analysis of the rGH element has shown that it consists of three hexamers related to the consensus [(A/G)GGT(C/A)A]. We have extended this analysis to the rMHC and rME elements. Binding of highly purified thyroid hormone receptor (T3R) to T3REs was determined using the gel shift assay, and thyroid hormone (T3) induction was measured in transient tranfections. We show that the wild type version of each of the three elements binds T3R dimers cooperatively. Mutational analysis of the rMHC and rME elements identified domains important for binding T3R dimers and allowed a direct determination of the relationship between T3R binding and function. In each element two hexamers are required for dimer binding, and mutations that interfere with dimer formation significantly reduce T3 induction. Similar to the rGH element, the rMHC T3RE contains three hexameric domains arranged as a direct repeat followed by an inverted copy, although the third domain is weaker than in rGH. All three are required for full function and T3R binding. The rME T3RE is a two-hexamer direct repeat T3RE, which also binds T3R monomer and dimer. Across a series of mutant elements, there was a strong correlation between dimer binding in vitro and function in vivo for rMHC (r = 0.99, P less than 0.01) and rME (r = 0.67, P less than 0.05) T3REs. Our results demonstrate a similar pattern of T3R dimer binding to a diverse array of hexameric sequences and arrangements in three wild type T3REs. Addition of nuclear protein enhanced T3R binding but did not alter the specificity of binding to wild type or mutant elements. Binding of purified T3R to T3REs was highly correlated with function, both with and without the addition of nuclear protein. T3R dimer formation is the common feature which defines the capacity of these elements to confer T3 induction.
Mol Endocrinol 1992 Apr
PMID:Capacity for cooperative binding of thyroid hormone (T3) receptor dimers defines wild type T3 response elements. 158 20

The epidermal growth factor (EGF) receptor (EGFR) promoter is negatively regulated by thyroid hormone and retinoic acid. This regulation can be mapped to a 36-basepair GC-rich region of the promoter (EGFR P/E) that functions autonomously as a promoter and an enhancer when placed in front of the thymidine kinase gene TATA element. Direct high affinity binding of the thyroid hormone receptor (T3R) to this element requires a nuclear protein. Through ion exchange chromatography and gel filtration of HeLa nuclear extract, this activity was identified as a protein of approximately 67 kilodaltons. This protein did not bind to DNA alone, but greatly augmented T3R binding to the EGFR P/E sequence in gel mobility shift and DNA precipitation assays. When combined with the T3R auxillary protein (TRAP), the T3R migrated as a larger complex on the DNA. Chemical cross-linking identified this complex as a heterodimer between T3R and TRAP. T3R-TRAP binds to a 7-basepair site in the EGFR P/E (GGGACTC) that has weak homology to a consensus thyroid response element half-site. Thus, on this element, T3R-TRAP heterodimers contact the DNA primarily on a single site that comprises an inhibitory thyroid response element.
Mol Endocrinol 1992 Apr
PMID:A nuclear protein is required for thyroid hormone receptor binding to an inhibitory half-site in the epidermal growth factor receptor promoter. 158 25

The rat GH (rGH) gene is expressed in the pituitary in a highly tissue-specific manner. A pituitary-specific transcription factor, Pit-1 (or GHF-1), and other, more tissue-general factors, including the thyroid hormone receptor (T3R), are important for regulating rGH promoter activity. The relative roles of Pit-1, T3R, and protein kinases in the activation of the rGH promoter were studied. Each component was supplied individually or in combination with the others to human monocyte U937 cells. The transfected rGH promoter was inactive in these cells even when it was cotransfected with either Pit-1 or T3R expression vectors. The rGH promoter carried in a truncated pUC vector could be activated by expression of the T3R if the cells were cultured with inducers of protein kinase-A (forskolin) and protein kinase-C [phorbol 12-myristate 13-acetate (PMA)] activity. By contrast, the PMA- and forskolin-dependent activation of the rGH promoter by Pit-1 expression was comparatively insignificant unless 1) the sequences deleted from the pUC vector (including a putative site for the transcription factor AP1) were restored to the plasmid carrying the rGH promoter; or 2) the T3R was coexpressed, which led to a marked synergistic response. These results indicate the relative inactivity of Pit-1 in isolation from other factors. Activation by forskolin and PMA did not require de novo protein synthesis. The synergistic activation by Pit-1 and the T3R was enhanced, but was not dependent upon, thyroid hormone (T3). The T3-dependent effect operated predominately through a thyroid hormone response element located up-stream of the two Pit-1-binding sites within the rGH promoter, whereas the T3-independent effect did not require any of the known T3R-binding sites on the rGH promoter. These results suggest a role for the more tissue-general T3R and protein kinases in the activation of the rGH promoter. They demonstrate the synergistic interplay between the T3R and Pit-1, underscore the dependence of Pit-1 action on other transcription factors, and implicate Pit-1 as a cofactor, rather than the dominant factor, influencing the tissue-specific expression of the rGH promoter.
Mol Endocrinol 1992 Apr
PMID:Synergistic activation of the rat growth hormone promoter by Pit-1 and the thyroid hormone receptor. 158 27

Mutations of the thyroid hormone receptor (TR) beta 1 gene have recently been detected in several unrelated families with generalized resistance to thyroid hormone (GRTH). We now report a novel point mutation in the TR beta 1 gene in a case of a Korean-Japanese kindred. The intracellular localization and the amount of TR proteins were considered to be normal by the immunocytochemical study of cultured skin fibroblasts from the patients using anti-T3 receptor antibody. The cDNA of the T3-binding domain of the TR beta 1 gene, synthesized from the total RNA of the patients' fibroblasts, was amplified by the polymerase chain reaction, and was sequenced. A point mutation, A to G, in one allele at 1612 resulting in an amino acid substitution from lysine 438 to glutamic acid was detected. The same mutation was identified in one allele in each of the affected members. In vitro translation products of the mutant TR beta 1 gene showed decreased T3-binding activity. These data suggest that a TR mutation is predominantly responsible for GRTH, irrespective of ethnic background.
Mol Cell Endocrinol 1992 Apr
PMID:A point mutation of the T3 receptor beta 1 gene in a kindred of generalized resistance to thyroid hormone. 158 88

DNA binding domain proteins (DBDP) were prepared using a pET construct containing an insert coding for amino acids 49-122 of human thyroid hormone receptor (hTR) alpha and 103-179 of hTR beta. These proteins were expressed in Escherichia coli strain BL21 (DE3)-plysS after induction by isopropyl-D-thiogalactopyranoside (IPTG). The hTR alpha and hTR beta DBDP contain respectively 79 and 82 amino acids, including an amino terminal 4 amino acid extension derived from pET-3a or the synthesized initiation codon. Using a gel shift assay, both DBDPs were found to bind to a DNA oligonucleotide containing a thyroid hormone response element (TRE). The DBDPs competed with full length hTR alpha 1 for binding to the oligonucleotide. Apo-DBDPs (Zn2+ released by low pH) failed to bind to the palindromic TRE. DNA binding is restored however if apo-DBDP is preincubated in 500 microM Zn2+. When the DBDPs were expressed in COS-7 cells using a pCB6+ expression vector, they did not induce expression of a TRE-CAT fusion gene. hTR DBDPs thus can bind to DNA, presumably as monomers, since they do not contain the leucine zipper-like motif for dimerization. In COS-7 cells, they fail to cause transactivation of a TRE-CAT fusion gene. It is inferred that this may be because the DBDPs are not translocated to the nucleus or lack a transactivation domain.
Mol Cell Endocrinol 1992 Apr
PMID:Expression and function of a human thyroid hormone receptor-derived DNA-binding domain protein. 158 92

The thyroid hormone receptor (TR) has the dual ability to activate or repress transcription of specific genes. A cell-free transcription system was used to study the effects of TR on transcription by positively (TREpMLP) and negatively (TSH alpha) regulated promoters. Receptor-deficient HeLa cell extracts were complemented with baculovirus-produced TR. TR stimulated transcription from the TREpMLP promoter by 3-fold, and trans-activation did not require hormone. Transcriptional stimulation by TR required the presence of the TRE sequence and was diminished by the addition of competitor TRE binding sites. Baculovirus-produced TR repressed transcription in vitro from the TSH alpha promoter by 30-50%, also in a hormone-independent manner. Transcription from a control adenovirus 2 major late promoter was unaffected by added TR. Receptor-specific antisera and competition with TRE binding sites impaired TR-mediated repression of the TSH alpha promoter. Unlike transcriptional stimulation, which was optimal when TR and HeLa extracts were added concomitantly, transcriptional repression by the TR was most effective when the receptor was preincubated with the alpha-promoter, suggesting that receptor binding to the promoter may block access of other proteins to cause transcriptional repression. These results indicate that baculovirus-expressed TR mediates transcriptional activation and repression in a promoter-specific manner in vitro. This system provides a valuable model for examining transcriptional control by the TR.
Mol Endocrinol 1992 May
PMID:Thyroid hormone receptor mediates transcriptional activation and repression of different promoters in vitro. 160 88

The rat pheochromocytoma cell line PC12 can be induced by growth factors to undergo proliferation and neuronal differentiation. These cells also have excitable membranes that can be depolarized by neurotransmitters or elevated levels of extracellular KCl. Treatment of PC12 cells with growth factors or membrane-depolarizing agents rapidly activates the expression of specific genes whose products are thought to mediate the subsequent biological responses. One such gene, nur77, is a member of the steroid and thyroid hormone receptor gene superfamily. We have identified the Nur77 protein and shown that it is synthesized rapidly and transiently in PC12 cells following stimulation, has a short half-life of 30 to 40 min, and is located in both the nucleus and the cytoplasm. Nur77 is posttranslationally modified, primarily by phosphorylation on serine residues. Phosphopeptide analysis reveals that Nur77 is modified differently upon membrane depolarization than after treatment with growth factors. We hypothesize that the activity of Nur77 is regulated by both differential gene expression and posttranslational modification and that these modes of regulation contribute to distinct downstream responses specific to membrane depolarization and growth factor treatment.
Mol Cell Biol 1991 Jun
PMID:Nur77 is differentially modified in PC12 cells upon membrane depolarization and growth factor treatment. 164 47

Different point mutations have been identified in the T3-binding domain of the c-erbA beta thyroid hormone receptor gene that are associated with variant phenotypes of generalized thyroid hormone resistance (GTHR). In most cases of GTHR, heterozygotes are affected; a single mutant allele results in the inhibition of the function of normal thyroid hormone receptors. We report here a novel genetic abnormality, a 3-basepair (bp) deletion in the T3-binding domain of the beta-receptor in a kindred, S, with GTHR. One patient, S1, was the product of a consanguineous union of two heterozygotes and was homozygous for this defect. Heterozygotes from kindred S harbored a CAC deletion at nucleotides 1295-1297, which resulted in the deduced loss of amino acid residue threonine at codon 332, and they displayed elevated free T4 levels and inappropriately normal TSH levels characteristic of other kindreds with GTHR. However, patient S1, who had two mutant alleles, had markedly elevated TSH and free T4 levels and displayed profound abnormalities in brain development and linear growth. A fibroblast c-erbA beta cDNA extending from codon 175 to stop codon 457 was cloned from patient S1, sequenced, and used to create a full-length mutant cDNA. The kindred S mutant receptor was synthesized in vitro and did not bind T3. This mutant receptor did bind with similar avidity as the wild-type human beta-receptor to thyroid hormone response elements of the human TSH beta (-12 to 43 bp) and rat GH (-188 to -160 bp) genes. Kindred S showed the effect in man of heterozygous and homozygous expression of a dominant negative form of c-erbA beta.
Mol Endocrinol 1991 Mar
PMID:A homozygous deletion in the c-erbA beta thyroid hormone receptor gene in a patient with generalized thyroid hormone resistance: isolation and characterization of the mutant receptor. 165 89

The identification of hormone response elements in the promoter regions of hormonally regulated genes has revealed a striking similarity between the estrogen response element (ERE) and a palindromic thyroid hormone response element (TRE) derived from the GH gene promoter. In addition, this TRE was described as a strong retinoic acid receptor response element for all three subtypes: alpha, beta, and gamma. We show here that the TRE in the absence of thyroid hormone receptor (TR) behaves similarly to imperfect EREs, which can synergize to mediate a strong estrogen-dependent activation of transcription. However, in the presence of TR, but the absence of T3, activation of the TRE constructs by estrogen receptor (ER) is inhibited. In vitro, ER and TR were found to bind to the TRE in the absence and presence of their respective ligands; however, TRs form a more stable complex with the TRE than does ER. To examine whether repression of ER activity on the TRE constructs by TR was due to heterodimer formation, we employed truncated TR mutants (tTR) that lacked the DNA-binding domain, but contained the ligand-binding/dimerization domain. The tTRs were shown to be efficient inhibitors of TR, but not of ER. Thus, inhibition of ER activity on TREs by TRs does not result from heterodimer formation. We discuss a mechanism in which TRs, in the absence of thyroid hormone, control TRE activation by related receptors by preventing their access to the TRE. This mechanism can greatly enhance the fidelity of the ligand-specific response from a TRE.
Mol Endocrinol 1991 Mar
PMID:Thyroid hormone receptors repress estrogen receptor activation of a TRE. 165 92


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