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)

To examine the role of nuclear retinoic acid (RA) receptors (RARs) in the regulation of squamous differentiation in normal human epidermal keratinocytes (NHEK), we analyzed binding activity, mRNA expression, and transcriptional activity of the endogenously expressed RARs. Specific RA-binding activity eluted from size-exclusion HPLC with an apparent mol wt of 50 kilodaltons and was predominantly (greater than 95%) associated with the NHEK nuclear cell fraction. This RAR-binding activity represented in part the expression of RAR alpha and RAR gamma genes, whose transcripts were expressed in similar abundance in undifferentiated NHEK. Differentiation resulted in lower mRNA expression of RAR alpha relative to the mRNA expression of RAR gamma. Treatment of NHEK cells with 10(-6) M RA did not induce expression of RAR beta mRNA. Similarly, three squamous cell carcinoma cell lines derived from human skin and oral cavity expressed RAR alpha and RAR gamma transcripts, but not RAR beta transcripts. Transfection of NHEK with chloramphenicol acetyltransferase (CAT) reporter plasmids indicated that the endogenously expressed RARs could activate transcription through the RAR beta response element in a concentration-dependent manner with doses of 10(-9) M RA and higher. CAT expression was not activated through TRE, a palindromic thyroid hormone response element with purported RA responsiveness. The competitive binding of benzoic acid derivatives of RA to RAR correlated with the ability of each analog to suppress mRNA expression of the squamous cell markers, involucrin, type I transglutaminase, and SQ37, and to activate transcription of the RAR beta response element-CAT reporter. These results demonstrate that the control of NHEK differentiation by RA is consistent with the interaction of the retinoid with RAR and the regulation of transcription by that ligand-receptor complex.
Mol Endocrinol 1992 May
PMID:Retinoic acid receptors as regulators of human epidermal keratinocyte differentiation. 131 2

Thyroid hormone receptors (TRs) mediate the regulation of gene transcription by thyroid hormone (T3) by binding to T3-responsive elements (TREs) in target genes. c-erbA alpha 2 is a C-terminal TR variant which does not bind T3 and is a dominant inhibitor of T3 action. When synthesized in Escherichia Coli, alpha 2 formed two TRE-binding complexes similar to the monomeric and homodimeric forms of TR alpha 1. However, alpha 2 did not bind nearly as well as TR alpha 1. Furthermore, alpha 2 failed to bind DNA with proteins that heterodimerized with TR alpha 1. TR alpha 1 and alpha 2 also did not bind DNA as heterodimers with one another. The differences between TR alpha 1 and alpha 2 were further analyzed by studying a variety of C-terminal mutants synthesized in reticulocyte lysates. Deletion of the last 20 of the 122 unique amino acids (aa) of alpha 2 increased its DNA binding to approximately the level of TR alpha 1, indicating that the C-terminus of alpha 2 is an inhibitory domain. This alpha 2 mutant (alpha 2 delta C) was still unable to heterodimerize with nuclear proteins, as were C-terminal deletion mutants of TR alpha 1. We hypothesized that fusion of TR alpha 1-specific sequences to the C-terminus of alpha 2 delta C would transfer the property of heterodimerization. Indeed, although alpha 2/alpha 1 chimeras containing the last 40 and 70 aa of TR alpha 1 failed to heterodimerize with nuclear proteins, addition of the last 100 or 150 aa of TR alpha 1 did render alpha 2 delta C heterodimerization competent. Thus, TR alpha 1 contains a C-terminal structure which is necessary for heterodimerization and can confer this property on alpha 2, which lacks this domain. The effects of the unique C-termini of TR alpha 1 and alpha 2 on their in vitro DNA binding have important implications for their mechanisms of action in vivo.
Mol Endocrinol 1992 May
PMID:The unique C-termini of the thyroid hormone receptor variant, c-erbA alpha 2, and thyroid hormone receptor alpha 1 mediate different DNA-binding and heterodimerization properties. 131 5

Mammalian alcohol dehydrogenase (ADH) catalyzes the oxidation of retinol to retinaldehyde, the rate-limiting step in the synthesis of retinoic acid. There exists a family of ADH isozymes encoded by unique genes, and it is unclear which isozymes are most important for regulation of retinoic acid synthesis during differentiation or development. A region in the human ADH3 promoter from -328 to -272 base pairs was shown previously to function as a retinoic acid response element (RARE), prompting an hypothesis for a positive feedback mechanism controlling retinoic acid synthesis (Duester, G., Shean, M. L., McBride, M. S., and Stewart, M. J. (1991) Mol. Cell. Biol. 11, 1638-1646). The ADH3 RARE contains three direct AGGTCA repeats which constitute the critical nucleotides of RAREs present in other genes. We dissected the ADH3 RARE and determined that receptor binding as well as transactivation are dependent upon only the two downstream AGGTCA motifs separated by 5 base pairs, a structure noticed previously for a RARE in the promoter for the retinoic acid receptor beta (RAR beta) gene. ADH3 and RAR beta RAREs functioned similarly in transfection assays, suggesting that the feedback mechanisms controlling ADH3 and RAR beta utilize a common RARE. We also found that the normal functioning of the ADH3 RARE was abrogated by thyroid hormone receptor in the presence of thyroid hormone. A negative thyroid hormone response element in the human ADH3 promoter was found to colocalize with the RARE. Since ADH production in rat liver is known to be repressed by thyroid hormone, these findings suggest that human ADH production may also be subject to thyroid hormone repression and that the mechanism involves an interference with retinoic acid induction.
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PMID:Retinoic acid activation and thyroid hormone repression of the human alcohol dehydrogenase gene ADH3. 132 Nov 36

T4-binding globulin (TBG) shares a high degree of homology with two serpin antiproteases, alpha 1-antichymotrypsin (ACT) and alpha 1-antitrypsin (AT), whose synthesis is increased during the acute phase phenomenon, which accompanies trauma, infections, and neoplasms. Interleukin-6 (IL-6) is believed to be the main effector of the acute phase response. When evaluated in human hepatoblastoma-derived (Hep G2) cells exposed to different doses of the recombinant human cytokine for variable time intervals, IL-6 caused a dose- and time-dependent decrease in the secretion of [35S]methionine-labeled TBG, transthyretin (TTR), and albumin. The secretion of ACT and AT was increased. These changes were not due to alterations in the secretory process, since the kinetics of secretion of newly synthesized proteins were not modified. IL-6 did, however, cause a decrease in the steady state levels of mRNA for TTR, TBG, and albumin and an increase in ACT and AT mRNAs. In addition, nuclear run-off assay demonstrated a decrease in the transcription of TTR, TBG, and albumin genes and an increased transcription of the ACT gene. Quantitation of the results showed that changes in the secretion of proteins, in steady state mRNA levels, and in gene transcription were superimposable for each protein, indicating that IL-6 exerts its effect on thyroid hormone-binding proteins mostly at the transcriptional level and that TTR is the thyroid hormone-binding protein showing the most pronounced negative regulation by IL-6. The opposite effect of IL-6 on TBG and the antiproteases, despite their structural homology, underscores gene divergence among these proteins.
Mol Endocrinol 1992 Jun
PMID:Effects of interleukin-6 on the expression of thyroid hormone-binding protein genes in cultured human hepatoblastoma-derived (Hep G2) cells. 132 58

Alignment of natural chicken ovalbumin upstream promoter transcription factor (COUP-TF) response elements shows that, in addition to the predominant direct repeat of the GGTCA motif with a 2-bp spacing, there are other functional COUP elements with variations in the GGTCA orientation and spacing. We systematically analyzed the binding of in vitro-synthesized COUP-TFs and showed that COUP-TF is capable of binding to oligonucleotides containing both direct repeats and palindromes and with different spacings of the GGTCA repeats. Subsequently, we analyzed four possible mechanisms proposed to explain how COUP-TF could bind to these spatial variations of the GGTCA repeat. We demonstrated that the functional DNA-binding form of COUP-TF is a dimer which requires two GGTCA half-sites to bind DNA. We demonstrated that the COUP-TF dimer undergoes a remarkable structural adaptation to accommodate binding to these spatial variants of the GGTCA repeats. A functional consequence of the promiscuous DNA binding of COUP-TF is its ability to down-regulate hormonal induction of target gene expression by other members of the steroid-thyroid hormone receptor superfamily such as the vitamin D3, thyroid hormone, and retinoic acid receptors. Our data indicate that COUP-TF may have an important role in hormonal regulation of gene expression by these receptors.
Mol Cell Biol 1992 Sep
PMID:Chicken ovalbumin upstream promoter transcription factor (COUP-TF) dimers bind to different GGTCA response elements, allowing COUP-TF to repress hormonal induction of the vitamin D3, thyroid hormone, and retinoic acid receptors. 132 15

Previous studies have shown that thyroid hormone receptors can form homo- and heterodimeric complexes when binding to response elements. We report here the binding characteristics of thyroid hormone receptor (TR) homo- and heterodimers binding to synthetic oligonucleotides with directly and palindromically repeated consensus motifs (AGGTCA). Binding assays showed that TR homodimer formation on DNA had a low specificity and cooperativity, and very fast off rates. In contrast, TRs and retinoic acid receptors readily formed heterodimers with higher specificity and affinity on direct repeats of the AGGTCA motif spaced by four or five nucleotides, although these heterodimer/DNA complexes were only moderately stable when compared to DNA-bound TR/retinoid X receptor heterodimers. Also, TR/retinoic acid receptor heteromeric binding to other elements, including the synthetic T3RE-pal element, was of low specificity. These biochemical results suggest that TRs are unlikely to regulate transcription as homodimers in vivo, and that TR heterodimers mediate the effects of thyroid hormone.
Mol Endocrinol 1992 Jul
PMID:Binding characteristics of the thyroid hormone receptor homo- and heterodimers to consensus AGGTCA repeat motifs. 132 17

Various point mutations in the c-erbA thyroid hormone receptor (TR) beta gene of unrelated kindreds have been reported to be responsible for different phenotypes of generalized thyroid hormone resistance. We now report a new point mutation, Td, in one of two TR beta alleles of three affected members of one family, designated family T. In contrast to the previously described point mutations, all located in the T3-binding domain of the TR beta gene, mutation Td was identified in the carboxy-terminal part of the hinge domain. Direct sequencing of the polymerase chain reaction-amplified whole coding region of the patients' fibroblast TR beta genes displayed a single guanine to adenine transition at cDNA nucleotide position 985. This altered alanine (GCC) to threonine (ACC) in codon 229. Garnier prediction of the consequence of the mutation indicated an altered secondary structure. The G----A nucleotide substitution was not present in 80 random TR beta alleles, suggesting that this point mutation is responsible for generalized thyroid hormone resistance in family T. The in vitro expressed mutant TR beta was shown to bind with high affinity to various thyroid hormone response elements. However, the affinity of the TR beta to bind to T3 was reduced 3-fold, indicating that the hinge domain of the TR beta is important for full ligand-binding activity. Moreover, it seems that multiple subdomains of the TR beta interact cooperatively to achieve optimal T3 activity.
Mol Endocrinol 1992 Jul
PMID:A point mutation (Ala229 to Thr) in the hinge domain of the c-erbA beta thyroid hormone receptor gene in a family with generalized thyroid hormone resistance. 132 20

Thyroid hormone receptors (TRs) and retinoic acid receptors (RARs) have been shown to interact with nuclear auxiliary proteins resulting in heteromeric complexes that bind strongly to their responsive elements. Recently the retinoid X receptors (RXRs) have been identified as one class of these nuclear proteins. RXRs strongly increase binding of TRs and RARs to a synthetic thyroid hormone (and retinoic acid) responsive element. Here results show that the binding of the heteromeric complexes to various natural response elements is highly specific and dictated by the partner of RXR in the complex. TR alpha and TR beta formed complexes with RXR alpha that strongly and selectively bound to natural thyroid hormone responsive elements, i.e. those from the rat alpha-myosin heavy chain gene and the rat malic enzyme gene. RXR alpha complexes with RAR alpha, RAR beta, and RAR gamma bound selectively to retinoic acid responsive elements from the human RAR beta 2 gene (hRAR beta 2), the gene of the rat cellular retinol binding protein I and the human apolipoprotein A1 gene. Under the conditions used here RXR alpha by itself did not bind to any of the responsive elements tested. Although TRs and RARs formed heterodimers with RXR in solution, these complexes were strongly stabilized by specific, high affinity response elements, but not by low affinity response elements. Transfection analyses showed strong synergism between receptors that formed effective heterodimers in transcriptional activation on several but not all response elements. Overall, these data demonstrate that RARs and TRs are unlikely to function as monomers or homodimers on the response elements investigated here and require RXRs or comparable proteins for effective response element activation.
Mol Endocrinol 1992 Jul
PMID:Heterodimeric receptor complexes determine 3,5,3'-triiodothyronine and retinoid signaling specificities. 132 21

The vitamin hormone retinoic acid (RA) regulates many complex biological programs. The hormonal signals are mediated at the level of transcription by multiple nuclear receptors. These receptors belong to the steroid/thyroid hormone receptor superfamily that also includes a large number of orphan receptors whose biological roles have not yet been determined. Although much has been learned in recent years about RA receptor (RAR) functions, little is known about how specific RA response programs are restricted to certain tissues and cell types during development and in the adult. It has been recently shown that RAR activities are regulated by retinoid X receptors (RXR) through heterodimer formation. In an effort to isolate and further characterize nuclear receptors that modulate RAR and/or RXR activities, we have screened cDNA libraries by using a RXR alpha cDNA probe. Two clones, COUP alpha and COUP beta, identical and closely related to the orphan receptor COUP-TF, were obtained. We show that COUP proteins dramatically inhibit retinoid receptor activities on certain response elements that are activated by RAR/RXR heterodimers or RXR homodimers. COUP alpha and -beta bind strongly to these response elements, including a palindromic thyroid hormone response element and a direct repeat RA response element as well as an RXR-specific response element. In addition, we found that the previously identified COUP-TF binding site in the ovalbumin gene functions in vitro as an RA response element that is repressed in the presence of COUP. Our data suggest that the COUP receptors are a novel class of RAR and RXR regulators that can restrict RA signaling to certain elements. The COUP orphan receptors may thus play an important role in cell- or tissue-specific repression of subsets of RA-sensitive programs during development and in the adult.
Mol Cell Biol 1992 Oct
PMID:COUP orphan receptors are negative regulators of retinoic acid response pathways. 132 57

Biogenesis of mitochondria involves the expression of genes located on nuclear chromosomes as well as on mitochondrial DNA. We studied the coordination of the two genomes by measuring transcript levels for nuclear (IV, Va, and VIc) and mitochondrial (II and III) subunits of cytochrome-c oxidase after altering the mitochondrial content of rat muscle and liver by altering the thyroid state of the animals. Tissue levels of these mRNAs were generally decreased in hypothyroid animals and were up-regulated again after thyroid hormone (T3) treatment. However, significant increases in the levels of all nuclear transcripts were observed in the liver 24 h after T3 treatment, but were delayed or remained unaltered (VIc) in muscle. In contrast, levels of mitochondrial transcripts were elevated early in muscle and late in liver. The abundance of the corresponding polypeptides, which were analyzed by immunoblotting, changed in direction and magnitude according to the changes in their mRNAs, indicating pretranslational control. We conclude that the two genomes are regulated by T3 not through a common coordinating mechanism, but via two separate pathways, which respond to T3 with tissue-specific kinetics. S1-nuclease protection analysis showed that probably only one transcript for subunit VIc is present in both tissues, thus excluding the possibility that the tissue-specific response is due to the expression of two isogenes. The abundance of mitochondrial DNA was unaltered despite the observed changes in mitochondrial transcripts, indicating that mitochondrial gene expression is regulated by transcriptional mechanisms and not by gene dosage as has been postulated by others.
Mol Endocrinol 1992 Sep
PMID:Regulation by thyroid hormone of nuclear and mitochondrial genes encoding subunits of cytochrome-c oxidase in rat liver and skeletal muscle. 133 77


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