TY - JOUR
T1 - Retinoid-dependent in vitro transcription mediated by the RXR/RAR heterodimer
AU - Valcárcel, Rafael
AU - Holz, Herbert
AU - García-Jiménez, Custodia
AU - Barettino, Domingo
AU - Stunnenberg, Hendrik G.
PY - 1994/12/15
Y1 - 1994/12/15
N2 - The effects of retinoids on gene regulation are mediated by retinoic acid receptors (RARs) and retinoid X receptors (RXRs). Here, we provide the first biochemical evidence that, in vitro, ligand governs the transcriptional activity of RXRα/RARα by inducing conformational changes in the ligand- binding domains. Using limited proteolytic digestion we show that binding of the cognate ligand causes a conformational change in the carboxy-terminal part of the receptor. We also show that recombinant RXRα/RARα is partially active in the absence of exogenously added ligand. Trans-activation depends critically on the ligand-dependent transcriptional activation function AF-2 of RARα. Full activation by recombinant RXRα/RARα, however, requires the addition of either all-trans RA, 9-cis RA, or other RAR-specific agonists, whereas an RARα-specific antagonist abolishes trans-activation. Intriguingly, the ligand-dependent AF-2 of RXR does not contribute to the level of transcription from the RARβ2 promoter in vitro even when the cognate ligand (9-cis RA) is bound. Thus, the major role of RXR in trans- activation of the RARβ2 promoter is to serve as an auxiliary factor required for the binding of RAR which, in turn, is directly responsible for transcriptional activity.
AB - The effects of retinoids on gene regulation are mediated by retinoic acid receptors (RARs) and retinoid X receptors (RXRs). Here, we provide the first biochemical evidence that, in vitro, ligand governs the transcriptional activity of RXRα/RARα by inducing conformational changes in the ligand- binding domains. Using limited proteolytic digestion we show that binding of the cognate ligand causes a conformational change in the carboxy-terminal part of the receptor. We also show that recombinant RXRα/RARα is partially active in the absence of exogenously added ligand. Trans-activation depends critically on the ligand-dependent transcriptional activation function AF-2 of RARα. Full activation by recombinant RXRα/RARα, however, requires the addition of either all-trans RA, 9-cis RA, or other RAR-specific agonists, whereas an RARα-specific antagonist abolishes trans-activation. Intriguingly, the ligand-dependent AF-2 of RXR does not contribute to the level of transcription from the RARβ2 promoter in vitro even when the cognate ligand (9-cis RA) is bound. Thus, the major role of RXR in trans- activation of the RARβ2 promoter is to serve as an auxiliary factor required for the binding of RAR which, in turn, is directly responsible for transcriptional activity.
KW - gene regulation
KW - RAR-specific agonists
KW - RXR/RAR heterodimer
KW - trans-activation
UR - http://www.scopus.com/inward/record.url?scp=0028569041&partnerID=8YFLogxK
U2 - 10.1101/gad.8.24.3068
DO - 10.1101/gad.8.24.3068
M3 - Article
C2 - 8001825
AN - SCOPUS:0028569041
SN - 0890-9369
VL - 8
SP - 3068
EP - 3079
JO - Genes and Development
JF - Genes and Development
IS - 24
ER -