201
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Perez A, Kastner P, Sethi S, Lutz Y, Reibel C, Chambon P. PMLRAR homodimers: distinct DNA binding properties and heteromeric interactions with RXR. EMBO J 1993; 12:3171-82. [PMID: 8393784 PMCID: PMC413583 DOI: 10.1002/j.1460-2075.1993.tb05986.x] [Citation(s) in RCA: 240] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Fusion proteins (named PMLRAR) between PML and the retinoic acid receptor alpha (RAR alpha) are generated as a result of the t(15;17) chromosomal translocation found in acute promyelocytic leukemia (APL). We show here that PMLRAR proteins exist in solution as stable homodimers whose formation is mediated by a presumptive coiled coil in the PML moiety. In contrast to RAR alpha, which requires heterodimerization with RXR for efficient DNA binding, PMLRAR homodimers can bind to target sequences in the absence of RXR, and the binding pattern of PMLRAR homodimeric complexes to directly repeated motif (DR) response elements with 1-5 bp spacers is different from that of RAR/RXR heterodimeric complexes. We show that the presence of RXR induces the formation of PMLRAR/RXR heteromeric complexes which bind to DNA via one RAR DNA binding domain (DBD) and one RXR DBD, like 'classical' RAR/RXR heterodimers. PMLRAR interaction with RXR occurs in solution and in transfected cultured Cos cells, and PMLRAR is able to sequester RXR efficiently in the cytoplasm, suggesting that dominant 'inactivation' of RXR may be a possible mechanism of action for PMLRAR. Accordingly, we show that PMLRAR can both prevent the binding of the vitamin D3 receptor (VDR) to a target sequence in vitro and inhibit vitamin D3-dependent activation of a VDR-responsive reporter gene in transfected cells. These results suggest that both the distinct DNA binding properties of PMLRAR homodimers and the sequestration of RXR by PMLRARs may contribute to the molecular mechanisms which underlie the pathogenesis of APL. We also report that RXR alpha transcripts are down-regulated by RA-treatment in promyelocytic cells.
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Affiliation(s)
- A Perez
- Laboratoire de Génétique Moléculaire des Eucaryotes du CNRS, Unité 184 de Biologie Moléculaire et de Génie Génétique de l'INSERM, Faculté de Médecine, Strasbourg, France
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202
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Schräder M, Bendik I, Becker-André M, Carlberg C. Interaction between retinoic acid and vitamin D signaling pathways. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(17)46779-2] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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203
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Yu VC. Let me count the ways. Science 1993; 261:145. [PMID: 8327881 DOI: 10.1126/science.8327881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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204
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Jones KA, Fitzgibbon J, Woodward KJ, Goudie D, Ferguson-Smith MA, Povey S, Wolfe J, Solomon E. Localization of the retinoid X receptor alpha gene (RXRA) to chromosome 9q34. Ann Hum Genet 1993; 57:195-201. [PMID: 8257089 DOI: 10.1111/j.1469-1809.1993.tb01595.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The retinoid X receptor alpha is one of a number of retinoic acid receptors which are members of the steroid/thyroid hormone superfamily. Localization of RXRA was achieved using the polymerase chain reaction on a panel of somatic cell hybrids. A cosmid clone was isolated using the RXRA PCR product, and this was used to further localize the gene by fluorescence in situ hybridization to chromosome 9q34 distal to the dopamine beta hydroxylase gene (DBH). This mapping position was confirmed by PCR on a panel of translocation hybrids.
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Affiliation(s)
- K A Jones
- Somatic Cell Genetics Laboratory, Imperial Cancer Research Fund, London
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205
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Zhang XK, Kahl M. Regulation of retinoid and thyroid hormone action through homodimeric and heterodimeric receptors. Trends Endocrinol Metab 1993; 4:156-62. [PMID: 18407151 DOI: 10.1016/1043-2760(93)90105-n] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Biologic responses to retinoids and thyroid hormones are mediated by their intracellular receptor proteins. Many exciting advances have been made recently in understanding the molecular mechanism by which these receptor proteins operate. In contrast to the steroid hormone receptors that function predominantly as homodimers, thyroid hormone receptors (TRs)and retinoic acid receptors (RARs) require interaction with the retinoid X receptors (RXRs) for efficient DNA binding and transactivation. In addition, RXRs, in the presence of their specific ligands such as 9-cis RA, can form homodimers that recognize a subset of retinoic acid responsive elements (RAREs). The retinoid responses mediated by RXR homodimers and RAR-RXR heterodimers can be restricted by the COUP-TF orphan receptors that bind strongly to certain RAREs as homodimers. Thus, a complex network of receptor interaction has been unraveled that promises a better understanding of thyroid and retinoid hormone regulation of fundamental biologic processes and diseases.
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Affiliation(s)
- X K Zhang
- Cancer Center, La Jolla Cancer Research Foundation, La Jolla, CA 92037, USA
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206
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Keller H, Mahfoudi A, Dreyer C, Hihi AK, Medin J, Ozato K, Wahli W. Peroxisome proliferator-activated receptors and lipid metabolism. Ann N Y Acad Sci 1993; 684:157-73. [PMID: 8391237 DOI: 10.1111/j.1749-6632.1993.tb32279.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
PPARs are nuclear hormone receptors which, like the retinoid, thyroid hormone, vitamin D, and steroid hormone receptors, are ligand-activated transcription factors mediating the hormonal control of gene expression. Two lines of evidence indicate that PPARs have an important function in fatty acid metabolism. First, PPARs are activated by hypolipidemic drugs and physiological concentrations of fatty acids, and second, PPARs control the peroxisomal beta-oxidation pathway of fatty acids through transcriptional induction of the gene encoding the acyl-CoA oxidase (ACO), which is the rate-limiting enzyme of the pathway. Furthermore, the PPAR signaling pathway appears to converge with the 9-cis retinoic acid receptor (RXR) signaling pathway in the regulation of the ACO gene because heterodimerization between PPAR and RXR is essential for in vitro binding to the PPRE and because the strongest stimulation of this gene is observed when both receptors are exposed simultaneously to their activators. Thus, it appears that PPARs are involved in the 9-cis retinoic acid signaling pathway and that they play a pivotal role in the hormonal control of lipid metabolism.
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Affiliation(s)
- H Keller
- Institut de Biologie animale, Université de Lausanne, Switzerland
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207
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Leid M, Kastner P, Durand B, Krust A, Leroy P, Lyons R, Mendelsohn C, Nagpal S, Nakshatri H, Reibel C. Retinoic acid signal transduction pathways. Ann N Y Acad Sci 1993; 684:19-34. [PMID: 8317828 DOI: 10.1111/j.1749-6632.1993.tb32268.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Complexity in the retinoid signaling system arises from a combination of several forms of retinoic acid which possess differential activities, multiple cytoplasmic binding proteins and nuclear receptors that have distinct ligand specificities and functional properties, and the existence of polymorphic retinoic acid response elements. Additional diversity appears to be generated by heterodimeric interactions between the two classes of nuclear retinoic acid receptors and between retinoic acid receptors and some other members of the nuclear receptor superfamily. Thus, a complex array of combinatorial effects is beginning to emerge that may account for the pleiotropic effects of retinoids.
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Affiliation(s)
- M Leid
- Laboratoire de Génétique Moléculaire des Eucaryotes du CNRS U/184 de Biologie Moléculaire et de Génie Génétique de I'INSERM, Institut de Chimie Biologique-Faculté de Médecine, Strasbourg, France
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208
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Abstract
Steroid hormone receptors stimulate gene transcription by binding to DNA as homodimers, whereas many other members of the nuclear receptor family appear to function as heterodimers or as monomers. This is important for target gene recognition and, given that many of the receptors are expressed in multiple forms, generates many combinations of ligand-dependent transcription factors that regulate the expression of different genes in diverse pathways.
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209
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Nagpal S, Friant S, Nakshatri H, Chambon P. RARs and RXRs: evidence for two autonomous transactivation functions (AF-1 and AF-2) and heterodimerization in vivo. EMBO J 1993; 12:2349-60. [PMID: 8389696 PMCID: PMC413465 DOI: 10.1002/j.1460-2075.1993.tb05889.x] [Citation(s) in RCA: 209] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We have previously reported that the AB regions of retinoic acid receptors (RARs and RXRs) contain a transcriptional activation function capable of modulating the activity of the ligand-dependent activation function present in the C-terminal DE regions of these receptors. However, we could not demonstrate that these AB regions possess an autonomous activation function similar to the AF-1s found in the AB regions of steroid hormone receptors. Using the mouse CRBPII promoter as a reporter gene, we now report that the AB regions of RAR alpha, beta and gamma, as well as those of RXR alpha and gamma, contain an autonomous, ligand-independent activation function, AF-1, which can efficiently synergize with AF-2s. Moreover, AF-1s account for the ligand-independent, constitutive activation of transcription by RXR alpha and gamma. We also show that RARs and RXRs preferentially heterodimerize in solution in cultured cells in vivo, through the dimerization interface present in their E region, irrespective of the presence of all-trans or 9-cis retinoic acid. Furthermore, our results indicate that homodimeric interactions are not observed in cultured cells in vivo under conditions where heterodimeric interactions readily occur, which is in agreement with previous observations showing the preferential binding of RAR-RXR heterodimers to RA response elements in vitro.
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Affiliation(s)
- S Nagpal
- Laboratoire de Génétique Moléculaire des Eucaryotes du CNRS, Strasbourg, France
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210
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Rhodes SJ, Chen R, DiMattia GE, Scully KM, Kalla KA, Lin SC, Yu VC, Rosenfeld MG. A tissue-specific enhancer confers Pit-1-dependent morphogen inducibility and autoregulation on the pit-1 gene. Genes Dev 1993; 7:913-32. [PMID: 8504933 DOI: 10.1101/gad.7.6.913] [Citation(s) in RCA: 162] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Pit-1 is a tissue-specific POU domain factor obligatory for the appearance of three cell phenotypes in the anterior pituitary gland. Expression of the pit-1 gene requires the actions of a cell-specific 390-bp enhancer, located 10 kb 5' of the pit-1 transcription initiation site, within sequence that proves essential for effective pituitary targeting of transgene expression during murine development. The enhancer requires the concerted actions of a cell-specific cis-active element, Pit-1 autoregulatory sites, and atypical morphogen response elements. Pituitary ontogeny in the Pit-1-defective Snell dwarf mouse reveals that pit-1 autoregulation is not required for initial activation or continued expression during critical phases of Pit-1 target gene activation but, subsequently, is necessary for maintenance of pit-1 gene expression following birth. A potent 1,25-dihydroxyvitamin D3-responsive enhancer element defines a physiological site in which a single nucleotide alteration in the sequence of core binding motifs modulates the spacing rules for nuclear receptor response elements. Unexpectedly, the major retinoic acid response element is absolutely dependent on Pit-1 for retinoic acid receptor function. On this DNA element, Pit-1 appears to function as a coregulator of the retinoic acid receptor, suggesting an intriguing linkage between a cell-specific transcription factor and the actions of morphogen receptors that is likely to be prototypic of mechanisms by which other cell-specific transcription factors might confer morphogen receptor responsivity during mammalian organogenesis.
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Affiliation(s)
- S J Rhodes
- Eukaryotic Regulatory Biology Program, University of California, San Diego
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211
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Lohnes D, Kastner P, Dierich A, Mark M, LeMeur M, Chambon P. Function of retinoic acid receptor gamma in the mouse. Cell 1993; 73:643-58. [PMID: 8388780 DOI: 10.1016/0092-8674(93)90246-m] [Citation(s) in RCA: 438] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Null mutant mice for retinoic acid receptor gamma 2 (RAR gamma 2) or all RAR gamma isoforms were generated. RAR gamma 2 mutants appeared normal, whereas RAR gamma mutants exhibited growth deficiency, early lethality, and male sterility due to squamous metaplasia of the seminal vesicles and prostate. These defects were previously observed in vitamin A-deficient animals and could be prevented by RA administration, demonstrating that RAR gamma mediates some of the retinoid signal in vivo. Congenital defects included Harderian gland agenesis, tracheal cartilage malformations, and homeotic transformations along the rostral axial skeleton, establishing a direct link between RA and patterning of the axial skeleton. We also show that in utero RA-induced lumbosacral truncations are mediated by RAR gamma. The observed RAR gamma null phenotype suggests a high degree of functional redundancy among the RARs. The variable penetrance of some of the observed defects is discussed in light of this redundancy and stochastic variation of gene activity.
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Affiliation(s)
- D Lohnes
- Laboratoire de Génétique Moléculaire des Eucaryotes du CNRS, Institut de Chimie Biologique, Faculté de Médecine, Strasbourg, France
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212
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Lee MS, Kliewer SA, Provencal J, Wright PE, Evans RM. Structure of the retinoid X receptor alpha DNA binding domain: a helix required for homodimeric DNA binding. Science 1993; 260:1117-21. [PMID: 8388124 DOI: 10.1126/science.8388124] [Citation(s) in RCA: 198] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The three-dimensional solution structure of the DNA binding domain (DBD) of the retinoid X receptor alpha (RXR alpha) was determined by nuclear magnetic resonance spectroscopy. The two zinc fingers of the RXR DBD fold to form a single structural domain that consists of two perpendicularly oriented helices and that resembles the corresponding regions of the glucocorticoid and estrogen receptors (GR and ER, respectively). However, in contrast to the DBDs of the GR and ER, the RXR DBD contains an additional helix immediately after the second zinc finger. This third helix mediates both protein-protein and protein-DNA interactions required for cooperative, dimeric binding of the RXR DBD to DNA. Identification of the third helix in the RXR DBD thus defines a structural feature required for selective dimerization of the RXR on hormone response elements composed of half-sites (5'-AGGTCA-3') arranged as tandem repeats.
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Affiliation(s)
- M S Lee
- Department of Molecular Biology, Scripps Research Institute, La Jolla, CA 92037
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213
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Farrants AK, Nilsson A, Trøen G, Blomhoff R, Pedersen JI. The effect of retinoids and clofibric acid on the peroxisomal oxidation of palmitic acid and of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid in rat and rabbit hepatocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1168:100-7. [PMID: 8504135 DOI: 10.1016/0005-2760(93)90272-b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The effects of retinoids and the peroxisome proliferator clofibric acid on peroxisomal enzyme pathways were studied in hepatocytes from both rat and rabbit. Retinoic acid and retinol increased the activity of acyl-CoA oxidase in rabbit hepatocytes around 60% and around 30% in rat hepatocytes. Exposure to clofibric acid caused an increase in acyl-CoA oxidase activity of 115% in rat hepatocytes and of 40% in rabbit hepatocytes, indicating that rabbit is less sensitive to peroxisome proliferator than rat. Simultaneous exposure to clofibric acid and retinoids did not act additatively or synergistically. Both rabbit and rat hepatocytes expressed mRNA for the peroxisome proliferator activated receptor, (PPAR), although the transcript in rabbit was slightly smaller compared to that expressed in rat hepatocytes. The effect of retinoic acid in 7800 C1 Morris rat hepatoma cells, a cell line known to have an inducible peroxisomal beta-oxidation of fatty acids, was only slight with an increase of the acyl-CoA oxidase activity of 25% compared with control cells. As for clofibric acid, which gave a 2-fold induction of the acyl-CoA oxidase activity, the effect of retinoic acid was potentiated by dexamethasone. These cells also expressed mRNA for PPAR, with the same size as that found in rat hepatocytes. The oxidation of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid (THCA), an intermediate in bile acid formation, in rat hepatocytes increased 110% by clofibric acid and around 80% by retinoic acid. In rabbit hepatocytes, clofibric acid increased the oxidation rate 75% and retinoic acid 100%. The results presented here show similarities in the effects of retinoids and clofibric acid on the acyl-CoA oxidase activity and the oxidation rate of THCA, since they increase these two peroxisomal activities in hepatocytes in vitro. A decrease in both these enzyme activities occurs during cultivation time in untreated primary hepatocyte cultures. The present data may therefore either be explained by an increased expression or an induced stability of the enzymes involved.
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Affiliation(s)
- A K Farrants
- Institute for Nutrition Research, School of Medicine, University of Oslo, Norway
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214
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Abstract
Retinoids play an important role in development and differentiation. Their effect is mediated through nuclear receptors, RAR (alpha, beta and gamma) and RXR (alpha, beta and gamma), which are members of a distinct subclass (hereafter referred to as type II) of the nuclear receptor superfamily that includes the thyroid hormone receptor (T3R), the vitamin D3 receptor (VD3R) and the peroxisome proliferator activated receptor (PPAR). Type II receptors transactivate through binding sites composed of closely related half-sites (consensus sequence AGG/TTCA) arranged as direct repeats and, with the possible exception of RXR, do not bind to their cognate binding sites as homodimers but require RXR for high affinity binding. RXR thus provides a link between biologically distinct ligand induced pathways and is a potential target for cross-regulation. In addition, RAR can utilize alternative routes to enhance transcription initiation mediated through transcriptional co-activators which are expressed in a cell-type specific manner.
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215
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Thomas HE, Stunnenberg HG, Stewart AF. Heterodimerization of the Drosophila ecdysone receptor with retinoid X receptor and ultraspiracle. Nature 1993; 362:471-5. [PMID: 8385270 DOI: 10.1038/362471a0] [Citation(s) in RCA: 368] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Ecdysone in Drosophila has been a paradigm for steroid hormones since its ability to induce gene activity directly was demonstrated by its effects on moulting and polytene chromosome puffing. The ecdysone receptor (EcR) was recently confirmed as a member of the nuclear receptor superfamily by cloning and characterization in a Drosophila cell line. Here we show that EcR needs to heterodimerize with either the retinoid X receptor (RXR) or its Drosophila homologue, ultraspiracle (USP), for DNA binding and transactivation. These results place the ecdysone receptor in the heterodimerizing class of the nuclear receptor superfamily and demonstrate that the role of RXR/USP as a central and promiscuous partner in mediating the activity of these receptors is highly conserved. Whereas EcR-USP DNA-binding activity is unaffected by hormone, EcR-RXR DNA-binding activity is stimulated by either ecdysteroid or 9-cis-retinoic acid, demonstrating that hormone can play a role in heterodimer stabilization.
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Affiliation(s)
- H E Thomas
- Gene Expression Programme, EMBL, Heidelberg, Germany
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216
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Abstract
Induction of the retinoic acid receptor beta 2 (RAR beta 2) gene by retinoic acid (RA) is mediated by a RA response element (RARE), which represents a high affinity binding site for RAR/RXR heterodimers acting at this site as RA-inducible transcription activators. In RA resistant RAC65 cells, RAR beta 2 induction is blocked due to expression of a truncated RAR alpha acting as a dominant negative repressor. Here we show that exogenous expression of RAR but not RXR can restore RA-dependent RAR beta 2 promoter activation in RAC65 cells. Structure-function analysis of hRAR beta 2 mutants in RAC65 cells shows, that the transactivation function required to restore RAR beta 2 promoter activation is dependent on the DNA binding, dimerization and RA-dependent transactivation properties of hRAR beta 2, which are retained in a mutant (beta delta 409) lacking the F domain. By contrast, dominant repression of RA-dependent mRAR beta 2 promoter activation by hRAR beta 2 mutants is independent of the DNA binding or RA-dependent transactivation function but requires a region (residues 204-384) in hRAR beta 2 involved in heterodimerization with RXR. These data extend previous observations on structure-function of RARs and provides tools for studying the role of retinoids and RARs during vertebrate development.
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Affiliation(s)
- S Shen
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Utrecht
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217
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Yu VC, Näär AM, Rosenfeld MG. Transcriptional regulation by the nuclear receptor superfamily. Curr Opin Biotechnol 1993; 3:597-602. [PMID: 1369415 DOI: 10.1016/0958-1669(92)90002-z] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In the past year, additional experimental data have expanded our understanding of the molecular mechanisms that underlie nuclear receptor control of regulatory programs. It is increasingly clear that steroid members (e.g. glucocorticoid and estrogen) and non-steroid members (e.g. retinoic acid, thyroid hormone, and vitamin D) of the nuclear receptor superfamily may utilize distinct strategies in achieving their complex control of gene regulation.
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MESH Headings
- Animals
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cell Nucleus/metabolism
- Chromosomes, Human, Pair 15
- Chromosomes, Human, Pair 17
- Gene Expression Regulation
- Humans
- Leukemia, Promyelocytic, Acute
- Multigene Family
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, Retinoic Acid
- Retinoid X Receptors
- Retinoids/metabolism
- Transcription Factors
- Transcription, Genetic
- Translocation, Genetic
- Tretinoin/metabolism
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Affiliation(s)
- V C Yu
- Howard Hughes Medical Institute, School of Medicine, University of California, San Diego, La Jolla 92093-0648
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218
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Schmidt ED, van Beeren M, Glass CK, Wiersinga WM, Lamers WH. Interaction between the thyroid hormone receptor and co-factors on the promoter of the gene encoding phospho enol pyruvate carboxykinase. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1172:82-8. [PMID: 8382533 DOI: 10.1016/0167-4781(93)90272-f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Using transient transfection studies we localized a thyroid hormone-responsive element on the promoter of the rat phospho-enol pyruvate carboxykinase gene between 355 and 174 bp upstream of the transcription start site. DNAse 1 footprinting analysis within this region showed that a 28 bp fragment at position -324 to -297 was protected by the thyroid-hormone receptor. This receptor was overexpressed in HeLa cells using a vaccinia virus expression vector. DNA-binding assays with this receptor-enriched nuclear HeLa cell extract revealed that only 20% of the thyroid hormone receptor was able to bind the target-sequence with high affinity (4 nM). Titration with nuclear extract from hepatocytes increased the percentage of c-erbA molecules able to bind to this thyroid hormone-responsive element 4-fold without a change in affinity. Our data show that the complex of the thyroid hormone responsive element of the promoter of the phosphoenol pyruvate carboxykinase gene and the thyroid hormone receptor contains only a single receptor molecule suggesting the formation of a heterodimer complex. Accordingly, this thyroid hormone receptor/DNA complex is formed only in the presence of co-factors that are present in limiting amounts in the hepatocyte nucleus.
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Affiliation(s)
- E D Schmidt
- Department of Anatomy and Embryology, AMC, Amsterdam, Netherlands
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219
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Carlberg C, Bendik I, Wyss A, Meier E, Sturzenbecker LJ, Grippo JF, Hunziker W. Two nuclear signalling pathways for vitamin D. Nature 1993; 361:657-60. [PMID: 8382345 DOI: 10.1038/361657a0] [Citation(s) in RCA: 424] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The dihydroxylated form of vitamin D3 (1,25-dihydroxy-D3)mediates a biological response by binding to intracellular receptors which belong to the steroid receptor superfamily. These receptors act as ligand-dependent transcription factors that bind to specific DNA sequences (reviewed in refs 6-9). We have identified two classes of vitamin D response elements that are activated either by the vitamin D receptor (VDR) alone or by heterodimers of VDR and the retinoid-X receptor-alpha (RXR-alpha). The motif GGGTGA arranged as a direct repeat with a spacing of six nucleotides or as a palindrome without spacing, or as an inverted palindrome with a 12-nucleotide spacing, confers vitamin D inducibility mediated by VDR alone. A second class of response elements, composed of directly repeated pairs of motifs (GGTCCA, AGGTCA, or GGGTGA) spaced by three nucleotides, is synergistically activated by RXR and VDR, but only in the presence of both ligands. Thus, the RXR ligand and the nature of the response element determine whether a nuclear receptor is co-regulated by RXR.
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Affiliation(s)
- C Carlberg
- Department of Pharma Research New Technologies, F. Hoffmann-La Roche Ltd, Basel, Switzerland
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220
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Keidel S, Szardenings M, Mueller WH. In vivo biological activity of retinoids partially correlates to their affinity to recombinant retinoic-acid receptor alpha and recombinant-cellular retinoic-acid-binding protein I. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 212:13-26. [PMID: 8383035 DOI: 10.1111/j.1432-1033.1993.tb17627.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Several known and some new retinoids were synthesized and their in vivo activity was investigated by an assay, based on induction of alkaline phosphatase in P19 teratocarcinoma cells, human prostate carcinoma cells and primary cultures of neonatal rat heart cells. The assay used in this study was found to be reproducible and useful for rapid screening of retinoids for biological activity. Two newly synthesized compounds exhibit high biological activity. The biological potency of the compounds was compared to their ability to bind to recombinant retinoic-acid receptor alpha and to cellular retinoic-acid-binding protein I determined by Charsorb-binding assay. mRNA of both retinoic-acid-binding proteins could be detected in the three cell lines investigated. As expected from the number of different retinoic-acid receptors, the results suggest that retinoids do not need to bind retinoic-acid receptor alpha nor cellular retinoic-acid-binding protein I in order to exhibit biological activity, but most retinoids investigated show a clear correlation between binding to these proteins and their biological activity.
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Affiliation(s)
- S Keidel
- Department of Biochemistry, Medizinische Hochschule Hannover, Federal Republic of Germany
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221
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Cooney A, Leng X, Tsai S, O'Malley B, Tsai M. Multiple mechanisms of chicken ovalbumin upstream promoter transcription factor-dependent repression of transactivation by the vitamin D, thyroid hormone, and retinoic acid receptors. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53592-4] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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222
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Islam T, Bugge T, Bohm S. The long terminal repeat of VL30 retrotransposons contains sequences that determine retinoic acid-induced transcription in cultured keratinocytes. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53686-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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223
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Divergent effects of 9-cis-retinoic acid receptor on positive and negative thyroid hormone receptor-dependent gene expression. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53546-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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224
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Pohl J, LaFace D, Sands JF. Transcription of retinoic acid receptor genes in transgenic mice increases CD8 T-cell subset. Mol Biol Rep 1993; 17:135-42. [PMID: 8384693 DOI: 10.1007/bf00996221] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Retinoic acid (RA), a vitamin A derivative is known to have a number of effects on the immune system such as inducing cytotoxic T-lymphocytes in vivo and inducing the rejection of skin grafts. However, the molecular mechanisms of these actions are unclear. The retinoic acid receptors which belong to the steroid/thyroid receptor superfamily, are known to bind to regulatory elements of certain genes thereby regulating gene transcription. To determine if expression of retinoic acid receptors in vivo under normal physiological conditions is also regulating genes involved in immunological function, we assayed the human retinoic acid receptor gamma gene driven by a T-cell specific lck-promoter in transgenic mice. Using FACS analysis, we showed that mice expressing the RAR gamma-transgene had significantly increased numbers of CD4-/CD8+ cells compared to controls.
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Affiliation(s)
- J Pohl
- Department of Immunology, Research Institute of Scripps Clinic, La Jolla, Calif
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225
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Subramaniam A, Gulick J, Neumann J, Knotts S, Robbins J. Transgenic analysis of the thyroid-responsive elements in the alpha-cardiac myosin heavy chain gene promoter. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53614-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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226
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Tini M, Otulakowski G, Breitman ML, Tsui LC, Giguère V. An everted repeat mediates retinoic acid induction of the gamma F-crystallin gene: evidence of a direct role for retinoids in lens development. Genes Dev 1993; 7:295-307. [PMID: 8436299 DOI: 10.1101/gad.7.2.295] [Citation(s) in RCA: 131] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The vertebrate lens is a classical system for examining mechanisms of tissue determination and differentiation, yet little is known about the signaling molecules controlling its development. Here, we report that retinoic acid (RA), a substance known for its teratogenic effects on the eye and as a natural endogenous morphogenetic agent, acts as a regulator of gene expression in the lens. We have identified a novel type of RA response element (RARE) within the lens-specific mouse gamma F-crystallin promoter, consisting of two (A/G)GGTCA motifs in an everted arrangement spaced by 8 nucleotides. This element (gamma F-RARE) mediates activation of the gamma F-crystallin promoter by ligand-activated endogenous lens cell RA receptors (RARs) and confers RA responsiveness when linked to a heterologous promoter. gamma F-RARE is bound in vitro by RAR/RXR heterodimers, and both receptors cooperate in vivo to trans-activate this element. These observations demonstrate a direct effect of RA on lens-specific gene expression and reveal a novel role for retinoids in the development and homeostasis of the mammalian eye.
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Affiliation(s)
- M Tini
- Division of Endocrinology, Hospital for Sick Children, Toronto, Ontario, Canada
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227
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Freedman LP, Luisi BF. On the mechanism of DNA binding by nuclear hormone receptors: a structural and functional perspective. J Cell Biochem 1993; 51:140-50. [PMID: 8440748 DOI: 10.1002/jcb.240510205] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The nuclear hormone receptor DNA-binding domain consists of two zinc finger-like modules whose amino acids are highly conserved among the members of the receptor superfamily. In this review, we describe the various genetic, biochemical, and structural experiments that have been carried out primarily for the DNA-binding domains of the glucocorticoid and estrogen receptors. We describe how the structural and functional information have permitted us to predict properties of the DNA-binding domains of other nuclear receptors. We postulate how receptors discriminate closely related response elements through sequence-specific contacts and distinguish symmetry of target sites through protein-protein interactions. This mechanism explains in part how the receptors regulate diverse sets of genes from a limited repertoire of core response elements. Lastly, we describe the stereochemical basis of nuclear receptor dysfunction in certain clinical disorders.
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Affiliation(s)
- L P Freedman
- Cell Biology and Genetics Program, Sloan-Kettering Institute, New York, New York 10021
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228
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Mader S, Leroy P, Chen J, Chambon P. Multiple parameters control the selectivity of nuclear receptors for their response elements. Selectivity and promiscuity in response element recognition by retinoic acid receptors and retinoid X receptors. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)54192-2] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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229
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Affiliation(s)
- M W McBurney
- Department of Medicine, University of Ottawa, Ontario, Canada
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230
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The glucocorticoid receptor and a putative repressor protein coordinately modulate glucocorticoid responsiveness of the mouse mammary tumor virus promoter in the rat hepatoma cell line M1.19. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53933-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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231
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Abstract
While a great deal has been learned about APL over the last few years, many important questions remain unanswered. It has become clear that the PML/RAR-alpha fusion protein is expressed in most cases of APL, and this protein presumably contributes to leukaemia initiation and/or progression. PML/RAR-alpha appears to specifically block the further differentiation of myeloid progenitor cells, although the mechanism of its action is not known. It may inhibit the transcription of RAR- or PML-regulated genes, in which case expression must be restored in the presence of therapeutic RA concentrations. However, the possibility remains that PML/RAR-alpha may have a novel function. In order to elucidate the molecular pathogenesis of APL, several important questions remain to be answered. These include whether PML is a transcription factor; the identification of its target genes and response elements, and the role of PML/RAR-alpha and RA in their regulation. Also whether the expression of PML/RAR-alpha in bone marrow cells (either by itself or in combination with other oncogenes) alters their tumourigenicity or differentiation potential. It is also important to determine the function(s) of PLZF and PLZF/RAR-alpha, and determine whether other APL patients with mutations involving PML or RAR-alpha (but not both) respond to therapy with all-trans-RA. Finally, it is important both for the understanding of the molecular biology of APL and its therapy, to determine the effects of other regulatory factors involved in the control of myeloid cell differentiation such as granulocyte colony stimulation factor (G-CSF) and granulocyte macrophage colony stimulating factor (GM-CSF) on APL cells in vitro and in vivo, both at presentation and in the RA-resistant patients in relapse.
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Affiliation(s)
- I D Trayner
- Molecular Medicine Unit, Rayne Institute, King's College School of Medicine and Dentistry, London, U.K
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232
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Ragsdale CW, Gates PB, Hill DS, Brockes JP. Delta retinoic acid receptor isoform delta 1 is distinguished by its exceptional N-terminal sequence and abundance in the limb regeneration blastema. Mech Dev 1993; 40:99-112. [PMID: 8382939 DOI: 10.1016/0925-4773(93)90091-b] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In amphibian limb regeneration memory for position in the proximal-distal axis can be respecified by retinoic acid. The favoured candidates to mediate this effect are the retinoic acid receptors (RARs) and of the RARs identified in the regeneration blastema, the delta receptor is the most abundant. The presence in blastemal mesenchyme of at least two delta receptor isoforms, delta 1 and delta 2, alternatively spliced at the A-B junction, was demonstrated in expression studies and by PCR cloning. The delta 1 receptor is abundant in regenerative structures such as the limb and tail, whereas the delta 2 and alpha receptors show a more uniform pattern of expression across adult newt tissues. Full-length cloning of the delta 1 receptor established the presence of an unusually long open reading frame and N-terminal sequence that appears unique among vertebrate retinoic acid receptors. Transient transfection of expression constructs into COS cells followed by Western blotting confirmed the existence of at least three potential initiation sites for delta 1 translation. The possibility that delta 1 RAR expression may specify positional memory directly was tested in RNase protection experiments. delta 1 receptor message is increased on amputation, but does not exhibit a pronounced differential distribution along the proximal-distal axis in normal and regenerating limbs, nor does it show a persistent alteration in expression levels following a dose of retinoic acid sufficient to respecify position. The possibility that the morphogenetic effects of RA may be mediated through receptor interactions is raised by the finding that single mesenchymal blastemal cells in culture can express multiple RAR subtypes (delta 1 and alpha) and isoforms (delta 1 and delta 2).
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Affiliation(s)
- C W Ragsdale
- Ludwig Institute for Cancer Research, Middlesex Hospital/University College Branch, London, UK
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233
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Issemann I, Prince RA, Tugwood JD, Green S. The retinoid X receptor enhances the function of the peroxisome proliferator activated receptor. Biochimie 1993; 75:251-6. [PMID: 8389594 DOI: 10.1016/0300-9084(93)90084-6] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The peroxisome proliferator activated receptor (PPAR) is a member of the steroid hormone receptor superfamily and is activated by a variety of non-genotoxic rodent hepatocarcinogens termed peroxisome proliferators. A key marker of peroxisome proliferator action is the peroxisomal enzyme acyl-CoA oxidase that is elevated about 10-fold in the liver of treated rodents. We have shown previously that a peroxisome proliferator response element (PPRE) is located 570 bp upstream of the rat acyl-CoA oxidase gene and that PPAR binds to it. We show here that the retinoid X receptor (RXR) is required for PPAR to bind to the PPRE and that the RXR ligand, 9-cis retinoic acid, enhances PPAR action. These results therefore suggest that retinoids may modulate the action of peroxisome proliferators.
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Affiliation(s)
- I Issemann
- ZENECA Central Toxicology Laboratory, Macclesfield, Cheshire, UK
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234
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Lehmann JM, Jong L, Fanjul A, Cameron JF, Lu XP, Haefner P, Dawson MI, Pfahl M. Retinoids selective for retinoid X receptor response pathways. Science 1992; 258:1944-6. [PMID: 1335166 DOI: 10.1126/science.1335166] [Citation(s) in RCA: 267] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Retinoids have a broad spectrum of biological activities and are useful therapeutic agents. Their physiological activities are mediated by two types of receptors, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). RARs, as well as several related receptors, require heterodimerization with RXRs for effective DNA binding and function. However, in the presence of 9-cis-retinoic acid, a ligand for both RARs and RXRs, RXRs can also form homodimers. A series of retinoids is reported that selectively activates RXR homodimers but does not affect RAR-RXR heterodimers and thus demonstrates that both retinoid response pathways can be independently activated.
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Affiliation(s)
- J M Lehmann
- Cancer Center, La Jolla Cancer Research Foundation, La Jolla, CA 92037
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235
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236
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Miquel C, Clusel C, Semat A, Gerst C, Darmon M. Retinoic acid receptor isoform RAR gamma 1: an antagonist of the transactivation of the RAR beta RARE in epithelial cell lines and normal human keratinocytes. Mol Biol Rep 1992; 17:35-45. [PMID: 1337576 DOI: 10.1007/bf01006398] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The diversity of isoforms of retinoic acid (RA) receptors (RARs) and of DNA sequences of retinoic acid-responsive elements (RAREs) suggests the existence of selectivities in the RAR/RARE recognition or in the subsequent gene modulation. Such selectivities might be particularly important for RAREs involved in positive feedback, eg. the RAR beta RARE. In the present work we found that in several epithelial cell lines, reporter constructs containing the RAR beta RARE linked to the HSV-tk promoter were transactivated in the presence of RA by endogenous RARs and co-transfected RAR alpha 1 and RAR beta 2 isoforms, but not by RAR gamam 1. On the contrary, this latter isoform behaved towards the RAR beta RARE as an inhibitor of the transactivation produced by endogenous RARs and by cotransfected RAR alpha 1 and RAR beta 2. RAR gamma 1 also behaved as an antagonist of the transactivation produced by cotransfected RXR alpha. The natural RAR beta gene promoter or RAR beta RARE tk constructs were not activated by the endogenous receptors of normal human keratinocytes (NHK), which are known to contain predominantly RAR gamma 1. It was, however, possible to activate to a certain extent RAR beta RARE-reporter constructs in NHK by co-transfecting RAR alpha 1, RAR beta 2 or RXR alpha. The antagonist behavior of RAR gamma 1 towards the RAR beta RARE may explain why in certain cell types such as keratinocytes, RAR beta is neither expressed nor induced by RA.
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Affiliation(s)
- C Miquel
- Cell Biology Department, Centre International de Recherches Dermatologiques (CIRD Galderma), Valbonne, France
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237
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Yao TP, Segraves WA, Oro AE, McKeown M, Evans RM. Drosophila ultraspiracle modulates ecdysone receptor function via heterodimer formation. Cell 1992; 71:63-72. [PMID: 1327536 DOI: 10.1016/0092-8674(92)90266-f] [Citation(s) in RCA: 511] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The vertebrate retinoid X receptor (RXR) has been implicated in the regulation of multiple hormonal signaling pathways through the formation of heteromeric receptor complexes that bind DNA with high affinity. We now demonstrate that ultraspiracle (usp), a Drosophila RXR homolog, can substitute for RXR in stimulating the DNA binding of receptors for retinoic acid, T3, vitamin D, and peroxisome proliferator activators. These observations led to the search and ultimate identification of the ecdysone receptor (EcR) as a Drosophila partner of usp. Together, usp and EcR bind DNA in a highly cooperative fashion. Cotransfection of both EcR and usp expression vectors is required to render cultured mammalian cells ecdysone responsive. These results implicate usp as an integral component of the functional EcR. By demonstrating that receptor heterodimer formation precedes the divergence of vertebrate and invertebrate lineages, these data underscore a central role for RXR and its homolog usp in the evolution and control of the nuclear receptor-based endocrine system.
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Affiliation(s)
- T P Yao
- Howard Hughes Medical Institute, La Jolla, California
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238
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Durand B, Saunders M, Leroy P, Leid M, Chambon P. All-trans and 9-cis retinoic acid induction of CRABPII transcription is mediated by RAR-RXR heterodimers bound to DR1 and DR2 repeated motifs. Cell 1992; 71:73-85. [PMID: 1327537 DOI: 10.1016/0092-8674(92)90267-g] [Citation(s) in RCA: 351] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Two cooperating retinoic acid response elements (RAREs) in the cellular retinoic acid-binding protein II (CRABPII) gene mediate differential transcriptional transactivation by retinoic acid receptors (RARs) and retinoid X receptors (RXRs) in P19 embryonal carcinoma cells. RARE1 and RARE2 are direct repeats (DR) of two motifs separated by 2 bp (DR2) and 1 bp (DR1), respectively, and bind RAR-RXR heterodimers more efficiently than homodimers. Using all-trans and 9-cis RA, which differentially activate RARs and RXRs, and RAR and RXR dominant-negative mutants, RAR-RXR heterodimers bound to RARE1 and RARE2 are shown to be responsible for CRABPII promoter transactivation, arguing against a unique DR spacing specifying recognition by RARs. Within heterodimers, RAR and RXR independently and differentially transactivate, depending on the specific RARE. Consistent with these results, 9-cis RA increases CRABPII mRNA levels more efficiently than all-trans RA. In contrast, all-trans and 9-cis RA have identical effects on induction of RAR beta 2 transcripts.
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Affiliation(s)
- B Durand
- Laboratoire de Génétique Moléculaire des Eucaryotes, Centre National de la Recherche Scientifique, Faculté de Médecine, Strasbourg, France
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239
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Zhang XK, Lehmann J, Hoffmann B, Dawson MI, Cameron J, Graupner G, Hermann T, Tran P, Pfahl M. Homodimer formation of retinoid X receptor induced by 9-cis retinoic acid. Nature 1992; 358:587-91. [PMID: 1323763 DOI: 10.1038/358587a0] [Citation(s) in RCA: 444] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Retinoid response pathways are mediated by two classes of receptors, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). A central question is whether distinct response pathways are regulated by these two classes of receptors. The observation that the stereoisomer 9-cis-retinoic acid binds with high affinity to RXRs suggested that this retinoid has a distinct role in controlling RXR activity, but it was almost simultaneously discovered that RXRs function as auxiliary receptors for RARs and related receptors, and are essential for DNA binding and function of those receptors. Hence, although RARs seem to operate effectively only as heterodimeric RAR/RXR complexes, RXRs themselves apparently function predominantly, if not exclusively, as auxiliary receptors. Here we report that 9-cis-retinoic acid induces RXR homodimer formation. Our results demonstrate a new mechanism for retinoid action by which a ligand-induced homodimer mediates a distinct retinoid response pathway.
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Affiliation(s)
- X K Zhang
- Cancer Center, La Jolla Cancer Research Foundation, California
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240
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Goss GD, McBurney MW. Physiological and clinical aspects of vitamin A and its metabolites. Crit Rev Clin Lab Sci 1992; 29:185-215. [PMID: 1336957 DOI: 10.3109/10408369209114600] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Retinoids, including retinol and retinoic acid (RA), are a group of naturally occurring and synthetic compounds that exhibit vitamin A-like biological activity. They achieve their effects by binding to intracellular proteins. Important sites of action are the nuclear retinoic acid receptors (RAR). These receptors, namely, RAR alpha, RAR beta, and RAR gamma, function as transcription factors by binding to RA-responsive elements (RARE) of multiple genes. Retinoids play a role in vision, embryogenesis, immune modulation, growth and differentiation of normal, premalignant and malignant tissues, the suppression of carcinogenesis, and the inhibition of tumor growth in experimental systems and humans. Reports of the significant antitumor effect of all-trans-RA in acute promyelocytic leukemia and the synthesis of new, less toxic, and more potent retinoids has generated renewed interest in these compounds. Retinoids may have an important role to play in the chemoprevention and therapy of cancer.
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Affiliation(s)
- G D Goss
- Department of Medicine, University of Ottawa, Ontario, Canada
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