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Mol. Cell. Biol., Aug 1996, 4137-4146, Vol 16, No. 8
N La Vista-Picard, PD Hobbs, M Pfahl, MI Dawson and M Pfahl
To obtain insights into the principles governing the complex biological
responses to retinoids, we have analyzed the ligand sensitivities of
various retinoid receptor-DNA complexes. We find that different retinoid
receptor heterodimers show distinct activation patterns with various
response elements while a given heterodimer can be activated at different
retinoic acid concentrations on different response elements. In vitro
binding experiments suggest that the same retinoic acid receptor-retinoid X
receptor (RAR-RXR) heterodimer can have different ligand affinities,
depending on the response element it is bound to. The differential
responses of a particular receptor heterodimer with various retinoic acid
responsive elements can be enhanced through the use of conformationally
restricted retinoids. RAR- and RXR-selective retinoids can also
synergistically activate the receptor heterodimers, indicating that both
partners in the heterodimer can contribute to ligand-induced
transcriptional activation. However, the relative influence of the RAR or
RXR partner is specific for each response element. Together, our data
demonstrate that it is the receptor-DNA complex and not the receptor alone
that determines the ligand response. This flexibility allows for a highly
pleiotropic retinoid response. Furthermore, conformationally restricted
retinoids can accentuate the differential responses and exhibit a certain
degree of gene selectivity by differentially activating the RAR or RXR
component in the context of a given response element.
Copyright © 1996, American Society for Microbiology
The receptor-DNA complex determines the retinoid response: a mechanism for the diversification of the ligand signal
Sidney Kimmel Cancer Center, La Jolla, California 92037, USA.
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