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 peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily. These ligand-activated transcription factors are implicated in the regulation of lipid metabolism and adipocyte differentiation and in the regulation of anti-inflammatory processes. In order to bind to DNA and activate transcription PPAR requires the formation of heterodimers with the retinoid X receptor (RXR). We have previously reported that replacement of a single leucine by an arginine at position 433 of hPPAR alpha (L433R), located in a highly conserved region of the ninth heptad repeat of a leucine-zipper-like motif in the ligand binding domain, abolished heterodimerization of PPAR with RXR and hence its trans-activating capacity. The aim of our present work was to investigate if other conserved amino acids of the ligand binding domain are important for heterodimerization of PPAR with RXR. We found that conserved leucines, L370 and L391, in a leucine-zipper-like motif of hPPAR alpha, as well as a highly conserved aspartic acid (D304) in the tau(i) domain are necessary for heterodimerization with RXR. In contrast, mutations of non-conserved amino acids within the leucine-zipper-like motif do not affect PPAR:RXR heterodimerization. Surprisingly, we found that some mutants deficient in heterodimerization with RXR (hPPAR alpha-L370R and -L391R) were still functional on specific peroxisome proliferator-activator response elements (PPREs). Both mutants could trans-activate on a PPRE from the P450 cytochrome promoter CYP4A1, whereas only the hPPAR alpha-L391R mutant could trans-activate from the acyl-CoA oxidase PPRE (ACOA) and, when stimulated with the peroxisome proliferator Wy14643, also from the bifunctional enzyme PPRE. We therefore hypothesize either that: (i) these mutants might be able to heterodimerize with a protein other than RXR and the affinity for this novel partner may depend on the nature of the PPRE and to some degree on the choice of the activator, or alternatively; (ii) that additional nuclear proteins might compensate in vivo for the decreased binding of RXR to these mutant PPARs observed in vitro.
Mol Cell Endocrinol 1999 Jan 25
PMID:Conserved amino acids in the ligand-binding and tau(i) domains of the peroxisome proliferator-activated receptor alpha are necessary for heterodimerization with RXR. 1019 90

The multiple biologic activities of retinoic acid (RA) are mediated through RAR and retinoid X receptor (RXR) nuclear receptors that interact with specific DNA target sequences as heterodimers (RXR-RAR) or homodimers (RXR-RXR). RA receptor activation appears critical to regulating important aspects of hematopoiesis, since transducing a COOH-terminally truncated RARalpha exhibiting dominant-negative activity (RARalpha403) into normal mouse bone marrow generates hematopoietic growth factor-dependent cell lines frozen at the multipotent progenitor (EML) or committed promyelocyte (MPRO) stages. Nevertheless, relatively high, pharmacological concentrations of RA (1 to 10 microM) overcome these differentiation blocks and induce terminal granulocytic differentiation of the MPRO promyelocytes while potentiating interleukin-3 (IL-3)-induced commitment of EML cells to the granulocyte/monocyte lineage. In the present study, we utilized RXR- and RAR-specific agonists and antagonists to determine how RA overcomes the dominant-negative activity of the truncated RARalpha in these different myeloid developmental stages. Unexpectedly, we observed that an RXR-specific, rather than an RAR-specific, agonist induces terminal granulocytic differentiation of MPRO promyelocytes, and this differentiation is associated with activation of DNA response elements corresponding to RAR-RXR heterodimers rather than RXR-RXR homodimers. This RXR agonist activity is blocked by RAR-specific antagonists, suggesting extensive cross-talk between the partners of the RXR-RARalpha403 heterodimer. In contrast, in the more immature, multipotent EML cells we observed that this RXR-specific agonist is inactive either in potentiating IL-3-mediated commitment of EML cells to the granulocyte lineage or in transactivating RAR-RXR response elements. RA-triggered GALdbd-RARalpha hybrid activity in these cells indicates that the multipotent EML cells harbor substantial nuclear hormone receptor coactivator activity. However, the histone deacetylase (HDAC) inhibitor trichostatin A readily activates an RXR-RAR reporter construct in the multipotent EML cells but not in the committed MPRO promyelocytes, indicating that differences in HDAC-containing repressor complexes in these two closely related but distinct hematopoietic lineages might account for the differential activation of the RXR-RARalpha403 heterodimers that we observed at these different stages of myeloid development.
Mol Cell Biol 1999 May
PMID:Retinoid X receptor (RXR) agonist-induced activation of dominant-negative RXR-retinoic acid receptor alpha403 heterodimers is developmentally regulated during myeloid differentiation. 1020 61

Some members of nuclear hormone receptors, such as the thyroid hormone receptor (TR), silence gene expression in the absence of the hormone. Corepressors, which bind to the receptor's silencing domain, are involved in this repression. Hormone binding leads to dissociation of corepressors and binding of coactivators, which in turn mediate gene activation. Here, we describe the characteristics of Alien, a novel corepressor. Alien interacts with TR only in the absence of hormone. Addition of thyroid hormone leads to dissociation of Alien from the receptor, as shown by the yeast two-hybrid system, glutathione S-transferase pull-down, and coimmunoprecipitation experiments. Reporter assays indicate that Alien increases receptor-mediated silencing and that it harbors an autonomous silencing function. Immune staining shows that Alien is localized in the cell nucleus. Alien is a highly conserved protein showing 90% identity between human and Drosophila. Drosophila Alien shows similar activities in that it interacts in a hormone-sensitive manner with TR and harbors an autonomous silencing function. Specific interaction of Alien is seen with Drosophila nuclear hormone receptors, such as the ecdysone receptor and Seven-up, the Drosophila homologue of COUP-TF1, but not with retinoic acid receptor, RXR/USP, DHR 3, DHR 38, DHR 78, or DHR 96. These properties, taken together, show that Alien has the characteristics of a corepressor. Thus, Alien represents a member of a novel class of corepressors specific for selected members of the nuclear hormone receptor superfamily.
Mol Cell Biol 1999 May
PMID:Alien, a highly conserved protein with characteristics of a corepressor for members of the nuclear hormone receptor superfamily. 1020 62

Retinoids are therapeutically effective in the treatment of psoriasis, photoaging, acne, and certain cancers. Some of the therapeutic actions of retinoids can be ascribed to retinoic acid receptor (RAR)-mediated antagonism of AP1-dependent gene expression. The increased activity of transcription factor AP1, a complex of oncoproteins Jun and Fos, is associated with cell growth and proliferation. Retinoids, on the other hand, inhibit cell proliferation and affect differentiation, activities that possibly stem from an antagonism of AP1-mediated gene expression by RARs. To gain insight into the molecular mechanism of RAR-AP1 interaction, we have identified the regions of the RAR required for AP1 antagonism. We demonstrate that the AP1 antagonism domain of RAR is a complex of the core of the DNA binding domain and the hydrophobic zipper region. Further, both monomeric RAR and RAR-RXR heterodimers inhibit the expression of an AP1 reporter. CREB binding protein (CBP) has been described as a cofactor for AP1, various nuclear hormone receptor proteins including RARs, and certain other transcription factors and is required for their transactivation properties. Therefore, CBP has been proposed as a common limiting cofactor that can account for inhibition of AP1-dependent gene expression by RARs. Interestingly, however, our results along with previously reported observations suggest that in addition to CBP, there may be other limiting cofactor(s) responsible for mutual transrepression of RAR and AP1.
Mol Cell Biol Res Commun 1999 Apr
PMID:Identification of the AP1-antagonism domain of retinoic acid receptors. 1032 71

MHR3, a homolog of the retinoid orphan receptor (ROR), is a transcription factor in the nuclear hormone receptor family that is induced by 20-hydroxyecdysone (20E) in the epidermis of the tobacco hornworm, Manduca sexta. Its 2.7-kb 5' flanking region was found to contain four putative ecdysone receptor response elements (EcREs) and a monomeric (GGGTCA) nuclear receptor binding site. Activation of this promoter fused to a chloramphenicol acetyltransferase (CAT) reporter by 2 micrograms of 20E per ml in Manduca GV1 cells was similar to that of endogenous MHR3, with detectable CAT by 3 h. When the ecdysone receptor B1 (EcR-B1) and Ultraspiracle 1 (USP-1) were expressed at high levels under the control of a constitutive promoter, CAT levels after a 3-h exposure to 20E increased two- to sixfold. In contrast, high expression of EcR-B1 and USP-2 caused little increase in CAT levels in response to 20E. Moreover, expression of USP-2 prevented activation by EcR-B1-USP-1. Deletion experiments showed that the upstream region, including the three most proximal putative EcREs, was responsible for most of the 20E activation, with the EcRE3 at -671 and the adjacent GGGTCA being most critical. The EcRE1 at -342 was necessary but not sufficient for the activational response but was the only one of the three putative EcREs to bind the EcR-B1-USP-1 complex in gel mobility shift assays and was responsible for the silencing action of EcR-B1-USP-1 in the absence of hormone. EcRE2 and EcRE3 each specifically bound other protein(s) in the cell extract, but not EcR and USP, and so are not EcREs in this cellular context. When cell extracts were used, the EcR-B1-USP-2 heterodimer showed no binding to EcRE1, and the presence of excess USP-2 prevented the binding of EcR-B1-USP-1 to this element. In contrast, in vitro-transcribed-translated USP-1 and USP-2 both formed heterodimeric complexes with EcR-B1 that bound ponasterone A with the same Kd (7 x 10(-10) M) and bound to both EcRE1 and heat shock protein 27 EcRE. Thus, factors present in the cell extract appear to modulate the differential actions of the two USP isoforms.
Mol Cell Biol 1999 Jul
PMID:Activation of a delayed-early gene encoding MHR3 by the ecdysone receptor heterodimer EcR-B1-USP-1 but not by EcR-B1-USP-2. 1037 39

Nuclear orphan receptors are DNA-binding proteins that share the domain structure of the nuclear hormone receptor superfamily, although their ligands are unknown. Members of the nuclear receptor family are involved in the regulation of various developmental and reproductive processes. We have identified such a nuclear orphan receptor in the zebrafish and named it zebrafish germ cell nuclear factor (zfGCNF) based on its high sequence homology to previously described mouse, human, and Xenopus laevis GCNF. Detailed sequence comparison of zfGCNF with mouse, human, and frog GCNF revealed high homologies in the domains conserved in the nuclear receptor family. Homology in the DNA-binding domain is 97% for frog and even 98.5% for mouse and human when compared to the zebrafish sequence. Homology in the E III subdomain of the transactivation/ligand-binding E domain is 100% when compared to the mouse and human sequences. Transcripts of different size were detected by Northern blot analysis in the zebrafish ovary, whereas, in the testis only one transcript was present. In situ hybridization revealed that zfGCNF was predominantly expressed in previtellogenic oocytes in the ovary and in spermatocytes in the testis.
Mol Reprod Dev 1999 Aug
PMID:Cloning and expression of the zebrafish germ cell nuclear factor. 1039 11

The DAX-1 gene has been involved in the dosage sensitive sex reversal (DSS) phenotype, a male-to-female sex-reversal syndrome due to the duplication of a small region of human chromosome Xp21. Dax-1 and Sry have been shown to act antagonistically in the mouse system, where increasing expression of the former leads to female development and increasing activity of the latter to male development. Although these data strongly implicate DAX-1 in sex determination, the mouse and human proteins appear to behave differently. Absence of DAX-1 is responsible for adrenal hypoplasia congenita, a human inherited disorder characterized by adrenal insufficiency and hypogonadotropic hypogonadism. Unlike human patients, Dax-1-deficient XY mice have normal levels of corticotropins and adrenal hormones but are sterile. Dax-1-deficient females are fertile. The DAX-1 protein, an unusual member of the nuclear hormone receptor, may act as a transcriptional repressor. It has been shown to both repress transcriptional activators by direct protein-protein interactions and to bind DNA hairpin structures and repress target genes.
Cell Mol Life Sci 1999 Jun
PMID:DAX-1, an 'antitestis' gene. 1041 68

The DAX-1 (also known as AHC) gene encodes an unusual member of the nuclear hormone receptor superfamily. DAX-1 plays a critical role during gonadal and adrenal differentiation since mutations of the human DAX-1 gene cause X-linked adrenal hypoplasia congenita associated with hypogonadotropic hypogonadism. In recent studies, DAX-1 was reported to function as a transcriptional suppressor of Ad4BP/SF-1, a critical transcription factor in gonadal and adrenal differentiation. With respect to implication of Ad4BP/SF-1 in the transcriptional regulation of the DAX-1 gene, inconsistent findings have been previously reported. We investigated the upstream region of the mouse Dax-1 (also known as Ahch) gene and identified a novel Ad4/SF-1 site by transient transfection and electrophoretic mobility shift assays. In addition, immunohistochemical analyses with a specific antibody to Dax-1 indicated the presence of immunoreactive cells in steroidogenic tissues, pituitary gland, and hypothalamus. Although the distributions of Dax-1 and Ad4BP/SF-1 were very similar, they were not completely identical. The expression of Dax-1 was significantly impaired in knock-out mice of the Ftz-f1 gene, which encodes Ad4BP/ SF-1. Taken together, our findings indicate that Ad4BP/SF-1 controls the transcription of the Dax-1 gene.
Mol Endocrinol 1999 Aug
PMID:Dax-1 as one of the target genes of Ad4BP/SF-1. 1044 2

Normal endocrine development and function require nuclear hormone receptor SF-1 (steroidogenic factor 1). To understand the molecular mechanism of SF-1 action, we have investigated its domain function by mutagenesis and functional analyses. Our mutant studies show that the putative AF2 (activation function 2) helix located at the C-terminal end is indispensable for gene activation. SF-1 does not have an N-terminal AF1 domain. Instead, it contains a unique FP region, composed of the Ftz-F1 box and the proline cluster, after the zinc finger motif. The FP region interacts with transcription factor IIB (TFIIB) in vitro. This interaction requires residues 178-201 of TFIIB, a domain capable of binding several transcription factors. The FP region also mediates physical interaction with c-Jun, and this interaction greatly enhances SF-1 activity. The putative SF-1 ligand, 25-hydroxycholesterol, has no effects on these bindings. In addition, the Ftz-F1 box contains a bipartite nuclear localization signal (NLS). Removing the basic residues at either end of the key nuclear localization sequence NLS2.2 abolishes the nuclear transport. Expression of mutants containing only the FP region or lacking the AF2 domain blocks wild-type SF-1 activity in cells. By contrast, the mutant having a truncated nuclear localization signal lacks this dominant negative effect. These results delineate the importance of the FP and AF2 regions in nuclear localization, protein-protein interaction, and transcriptional activation.
Mol Endocrinol 1999 Sep
PMID:Function of steroidogenic factor 1 domains in nuclear localization, transactivation, and interaction with transcription factor TFIIB and c-Jun. 1047 48

Estrogen receptor-alpha is a member of the nuclear hormone receptor superfamily and is considered as a very important regulatory protein. Human estrogen receptor-alpha has been cloned into Saccharomyces cerevisiae as a fusion to ubiquitin and expression is controlled by a metallothionin promotor. Pilot scale quantities of receptor have been produced by a yeast strain transformed with expression plasmid YEpE13 [Graumann et al., J. Steroid Biochem. Mol. Biol. 57 (1996) 293] in a 14 l stirred tank reactor. The yeast extract contained 2-4 pmol of receptor protein per mg total protein. A purification scheme has been developed using heparin-affinity chromatography combined with affinity chromatography with immobilized 17beta-estradiol 17-hemisuccinate. Heparin-affinity chromatography was very efficient to remove host cell protein. Accompanying proteins that stabilize unoccupied receptor have not been dissociated during elution. The receptor could be purified 5-10-fold in ligand-free state. In contrast to previous reports, we did not find a difference of the binding affinity of liganded and unliganded receptor for heparin immobilized onto Sepharose. The unoccupied receptor could be further purified 100-fold with ligand-affinity chromatography using 17beta-estradiol 17-hemisuccinate-bovine serum albumin-Sepharose. The receptor could be kept in its native state, although saturated with 17beta-estradiol. The purification sequence allows an efficient production of receptor. Further improvement of productivity can be only accomplished by increasing the expression level.
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PMID:Affinity chromatography of human estrogen receptor-alpha expressed in Saccharomyces cerevisiae. Combination of heparin- and 17beta-estradiol-affinity chromatography. 1048 Feb 41


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