Mol. Cell. Biol., Dec 1995, 6481-6487, Vol 15, No. 12
B Roy, R Taneja and P Chambon
Retinoic acid receptor (RAR)-retinoid X receptor (RXR) heterodimers bind to
cognate response elements in vitro more efficiently than do RAR or RXR
homodimers, and both RAR and RXR partners have been shown to activate
various promoters in transiently transfected cells. We have now
investigated whether ligand-dependent activation of both heterodimeric
partners is involved in induced expression of endogenous RA-responsive
genes and in P19 and F9 cell differentiation. On their own, low
concentrations of retinoids selective for either RAR alpha, RAR beta, or
RAR gamma did not induce or very inefficiently induced the expression of
several RA target genes or triggered differentiation. An RXR-specific
synthetic retinoid was similarly inefficient at any concentration. In
contrast, at the same concentrations, various combinations of RAR (RAR
alpha, RAR beta, or RAR gamma) and RXR selective retinoids resulted in
synergistic induction of all retinoic acid (RA) target genes examined, as
well as in cell differentiation. However, the magnitude of this synergistic
activation varied depending on both the RAR-RXR combination and the
promoter context of the responsive genes. Promiscuous activation of the
three RARs, or concomitant activation of RAR alpha and RAR gamma, at
selective retinoid concentrations also resulted in induction of gene
expression and cell differentiation. Taken together, our results are
consistent with the conclusion that the RAR and RXR partners of RAR-RXR
heterodimers can synergistically activate transcription of RA- responsive
genes and can induce differentiation of P19 and F9 cells.(ABSTRACT
TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Synergistic activation of retinoic acid (RA)-responsive genes and induction of embryonal carcinoma cell differentiation by an RA receptor alpha (RAR alpha)-, RAR beta-, or RAR gamma-selective ligand in combination with a retinoid X receptor-specific ligand
Institut de Genetique et de Biologie Moleculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Sante et de la Recherche Medicale/Universite Louis Pasteur, College de France, Illkirch, France.
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