scholarly journals Differential 9-cis-Retinoic Acid-dependent Transcriptional Activation by Murine Retinoid X Receptor (RXR) and RXR

1996 ◽  
Vol 271 (18) ◽  
pp. 10503-10507 ◽  
Author(s):  
Paul L. Hallenbeck ◽  
Saverio Minucci ◽  
Roland Lippoldt ◽  
Marcia Phyillaier ◽  
Valerie Horn ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Transcriptional Activation ◽  
Retinoid X Receptor

scholarly journals Mutations that alter ligand-induced switches and dimerization activities in the retinoid X receptor.

1994 ◽  
Vol 14 (6) ◽  
pp. 4311-4323 ◽  
Author(s):  
X K Zhang ◽  
G Salbert ◽  
M O Lee ◽  
M Pfahl
Keyword(s):  
Amino Acids ◽  
Retinoic Acid ◽  
Amino Acid ◽  
Dna Binding ◽  
Transcriptional Activation ◽  
Activation Function ◽  
Retinoid X Receptor ◽  
Single Amino Acid ◽  
Independent Manner ◽  
Present Evidence

The retinoid X receptor (RXR) heterodimerizes with a variety of nuclear receptors. In addition, RXR forms homodimers in the presence of its ligand, 9-cis-retinoic acid. From deletion and point mutation analysis we present evidence that a short region (amino acids 413 to 443) in the carboxy terminus of RXR alpha is critical for both homo- and heterodimeric interactions as well as for diverse functional activities. In addition, we present evidence that homo- and heterodimer functions can be separated. The deletion of 19 amino acids from the C-terminal end of RXR dramatically reduced the transcriptional activation function of RXR. The removal of 10 additional amino acids resulted in a receptor (delta RXR3) that had completely lost its ligand-dependent homodimer function but retained its heterodimer activities. Heterodimer function was abolished by the deletion of an additional 20 amino acids. Single amino acid substitutions in the region generated receptors with altered RXR homodimer DNA binding, while simultaneous mutation of three Leu residues (Leu-418, -419 and -422) completely abolished both RXR homodimer and heterodimer DNA binding activities. Mutation of Leu-430 to Phe (L430-F) resulted in a receptor that bound to DNA strongly as homodimers in a ligand-independent manner, while another single amino acid exchange (L422-Q) led to a mutant that behaved in a manner exactly opposite to that of wild-type RXR in that the homodimerization of the mutant occurred in the absence of ligand and was inhibited by 9-cis-retinoic acid. In transfection assays, both L422-Q and L430-F failed to act as homodimers but retained their heterodimer function. Our studies demonstrate the unique properties of the RXR ligand binding domain and point to specific residues that mediate homo- and heterodimer activities and ligand-induced conformational switches.

scholarly journals Natural vitamin D3 response elements formed by inverted palindromes: polarity-directed ligand sensitivity of vitamin D3 receptor-retinoid X receptor heterodimer-mediated transactivation.

1995 ◽  
Vol 15 (3) ◽  
pp. 1154-1161 ◽  
Author(s):  
M Schräder ◽  
S Nayeri ◽  
J P Kahlen ◽  
K M Müller ◽  
C Carlberg
Keyword(s):  
Retinoic Acid ◽  
Nuclear Receptor ◽  
Vitamin D3 ◽  
Transcriptional Activation ◽  
Thyroid Hormone Receptor ◽  
Retinoid X Receptor ◽  
Direct Repeats ◽  
Response Element ◽  
Response Elements ◽  
Ligand Sensitivity

VDR, the nuclear receptor for 1,25-dihydroxyvitamin D3 (VD), is a member of the superfamily of nuclear hormone receptors and controls multiple aspects of homeostasis, cell growth, and differentiation. VDR can function as a homodimer, but heterodimerization with the retinoid X receptor (RXR), retinoic acid receptor, or thyroid hormone receptor increases its affinity for response elements in the promoter of target genes. All natural VD response elements identified so far consist of direct repeats of a variety of hexameric core binding motifs with a preferential spacing of three nucleotides (DR3s). However, all four VD signalling pathways function also on response elements formed by inverted palindromes, although these sequences were not of natural origin. Here, we report the identification of two VD response elements consisting of inverted palindromes spaced by nine nucleotides (IP9s) in the promoters of the human calbindin D9k gene and the rat osteocalcin gene. Like most DR3-type VD response elements, both IP9s are preferentially bound by VDR-RXR heterodimers with a 5'-RXR-VDR-3' polarity, whose transcriptional activity can be enhanced by costimulation with 9-cis retinoic acid. We demonstrate that changing the response element orientation relatively to the basal promoter decreases the sensitivity of transcriptional activation by VD by about 10-fold. Our findings indicate that inverted palindromes are as functional as direct repeats. Furthermore, we suggest that the orientation of a nuclear receptor complex in relation to the basic transcriptional machinery, which is directed by heterodimer polarity and response element orientation, influences the ligand sensitivity of the respective target gene expression.

Mutations that alter ligand-induced switches and dimerization activities in the retinoid X receptor

1994 ◽  
Vol 14 (6) ◽  
pp. 4311-4323
Author(s):  
X K Zhang ◽  
G Salbert ◽  
M O Lee ◽  
M Pfahl
Keyword(s):  
Amino Acids ◽  
Retinoic Acid ◽  
Amino Acid ◽  
Dna Binding ◽  
Transcriptional Activation ◽  
Activation Function ◽  
Retinoid X Receptor ◽  
Single Amino Acid ◽  
Independent Manner ◽  
Present Evidence

The retinoid X receptor (RXR) heterodimerizes with a variety of nuclear receptors. In addition, RXR forms homodimers in the presence of its ligand, 9-cis-retinoic acid. From deletion and point mutation analysis we present evidence that a short region (amino acids 413 to 443) in the carboxy terminus of RXR alpha is critical for both homo- and heterodimeric interactions as well as for diverse functional activities. In addition, we present evidence that homo- and heterodimer functions can be separated. The deletion of 19 amino acids from the C-terminal end of RXR dramatically reduced the transcriptional activation function of RXR. The removal of 10 additional amino acids resulted in a receptor (delta RXR3) that had completely lost its ligand-dependent homodimer function but retained its heterodimer activities. Heterodimer function was abolished by the deletion of an additional 20 amino acids. Single amino acid substitutions in the region generated receptors with altered RXR homodimer DNA binding, while simultaneous mutation of three Leu residues (Leu-418, -419 and -422) completely abolished both RXR homodimer and heterodimer DNA binding activities. Mutation of Leu-430 to Phe (L430-F) resulted in a receptor that bound to DNA strongly as homodimers in a ligand-independent manner, while another single amino acid exchange (L422-Q) led to a mutant that behaved in a manner exactly opposite to that of wild-type RXR in that the homodimerization of the mutant occurred in the absence of ligand and was inhibited by 9-cis-retinoic acid. In transfection assays, both L422-Q and L430-F failed to act as homodimers but retained their heterodimer function. Our studies demonstrate the unique properties of the RXR ligand binding domain and point to specific residues that mediate homo- and heterodimer activities and ligand-induced conformational switches.

scholarly journals Immunological identification and functional quantitation of retinoic acid and retinoid X receptor proteins in human skin.

1994 ◽  
Vol 269 (32) ◽  
pp. 20629-20635 ◽  
Author(s):  
G.J. Fisher ◽  
H.S. Talwar ◽  
J.H. Xiao ◽  
S.C. Datta ◽  
A.P. Reddy ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Human Skin ◽  
Retinoid X Receptor ◽  
Receptor Proteins ◽  
Immunological Identification

scholarly journals Glucocorticoids increase retinoid-X receptor alpha (RXRalpha) expression and enhance thyroid hormone action in primary cultured rat hepatocytes

1999 ◽  
Vol 22 (1) ◽  
pp. 81-90 ◽  
Author(s):  
S Yamaguchi ◽  
Y Murata ◽  
T Nagaya ◽  
Y Hayashi ◽  
S Ohmori ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Binding Protein ◽  
Rat Hepatocytes ◽  
Retinoid X Receptor ◽  
Type I ◽  
Receptor Alpha ◽  
Primary Cultured Rat Hepatocytes ◽  
Spot 14 ◽  
Cultured Rat Hepatocytes ◽  
Retinoid X Receptor Alpha

We have previously demonstrated that dexamethasone (DEX) enhances the T3-dependent increase in type I 5'-deiodinase (5'DI) mRNA in primary cultured rat hepatocytes grown as spheroids. Here we report that DEX-enhanced T3-responsiveness also occurs in two other T3-regulated hepatic genes, Spot 14 and malic enzyme. This enhancement was inhibited by pretreatment with cycloheximide and the stability of 5'DI and Spot 14 mRNAs was not affected by DEX. We thus hypothesized that a factor(s) that augments T3-responsiveness is induced by DEX. Among the possible candidates examined, retinoid-X receptor alpha (RXRalpha), which is a main heterodimer partner with T3 receptor, appeared to be involved. Whereas DEX increased the amount of RXRalpha mRNA, it did not affect the expression of other possible factors such as steroid receptor coactivator-1 and the binding protein of cAMP response element-binding protein. Northern and Western blot analysis, and electrophoretic mobility shift assay revealed that DEX increased RXRalpha expression at both the mRNA and protein levels. Maximal increase in RXRalpha protein was achieved with the addition of physiological concentrations of DEX (10(-8) M). To test whether the DEX-induced increase in RXRalpha affects ligand-dependent transcriptional activation through other receptors that form heterodimer with RXR, we examined its effect on the retinoic acid (RA)/RA receptor (RAR) system. Indeed, DEX also enhanced the RA-dependent increase in RARbeta mRNA in a cycloheximide-sensitive manner. Increase in the level of RXRalpha in hepatocytes by infection with the RXRalpha-expressing adenovirus resulted in enhancement of the T3-dependent increase in 5'DI mRNA. These results strongly suggest that the DEX-induced augmentation of T3-responsiveness in cultured hepatocytes is mediated, in part, by the increased expression of RXRalpha.

Ligand-inducible retinoid X receptor-mediated protein: DNA interactions in the retinoic acid receptor β2 gene promoter in vivo

1998 ◽  
Vol 136 (2) ◽  
pp. 109-118 ◽  
Author(s):  
Masato Ikeda ◽  
Remco A Spanjaard ◽  
Elizabeth W Noordhoek ◽  
Akio Kawaguchi ◽  
Toshimasa Onaya ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Retinoic Acid Receptor ◽  
Gene Promoter ◽  
Retinoid X Receptor ◽  
Dna Interactions ◽  
Acid Receptor ◽  
Protein Dna Interactions ◽  
Retinoic Acid Receptor Β2

scholarly journals Induction of Apoptosis Without Differentiation by Retinoic Acid in PLB-985 Cells Requires the Activation of Both RAR and RXR

Blood ◽  
1997 ◽  
Vol 90 (9) ◽  
pp. 3345-3355 ◽  
Author(s):  
Yury Monczak ◽  
Michel Trudel ◽  
William W. Lamph ◽  
Wilson H. Miller
Keyword(s):  
Retinoic Acid ◽  
Cell Surface ◽  
Transcriptional Activation ◽  
Surface Marker ◽  
Cell Surface Marker ◽  
Retinoid Receptor ◽  
Color Flow ◽  
Nb4 Cells ◽  
Induction Of Apoptosis ◽  
Stimulation Of

Abstract Retinoic acid (RA) induces differentiation, followed by apoptosis in acute promyelocytic leukemia (APL) cells, both in vitro and in patients. One problem in understanding these mechanisms is to distinguish molecular events leading to differentiation from those leading to apoptosis. We have identified a leukemic cell line, PLB-985, where RA directly induces apoptosis with no morphologic, genetic, or cell-surface marker evidence of differentiation. These cells differentiate following dimethyl sulfoxide (DMSO), but not RA, treatment. Two-color flow cytometry showed no alteration of the cell cycle after RA treatment, and cell-surface marker analysis of CD11a, CD11b, and CD13 showed no modulation typical of differentiating cells. RNA expression of myeloblastin and transglutaminase, genes regulated by RA-induced differentiation in NB4 cells, was unchanged by RA treatment. Instead, RA induced apoptosis, as shown by typical apoptotic morphological features, genomic DNA laddering, and positive labeling in the TUNEL assay. We found that induction of apoptosis in this model requires a different pattern of retinoid receptor binding and transcriptional activation than is seen in APL cells. As previously described, treatment with retinoid receptor-selective ligands showed that stimulation of RAR alone is sufficient to induce differentiation and apoptosis in NB4 cells, and that stimulation of RXR has no effect on the parameters analyzed. In PLB-985 cells, on the other hand, apoptosis was induced only upon costimulation of both RAR and RXR. Stimulation of either receptor alone had no effect on the cells. Consistent with these findings, bcl-2 RNA and protein levels were downregulated after stimulation of both RAR and RXR, but not with an RAR-specific ligand alone, as in NB4 cells. The expression of several other bcl-2 family members (bcl-X, ich-1, bax, bag, and bak ) and retinoid receptors (RARα, RXRα, and RXRβ) was not affected by treatment with RAR- and/or RXR-activating retinoids; RARβ RNA was undetectable before and after retinoid treatment. Thus, our cell model provides a useful tool in determining the genetic events mediating apoptosis as a response to RA, unobscured by events implicated in differentiation.

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