ABSTRACT
RXR also forms heterodimcrs with COUP-TF (41), one of the structurally related "orphan" receptors that lack identified ligands. As in the case of the RAR-RXR complex, the COUP-TF-RXR heterodimer functions as a potent repressor of RXR-mediated transactivation through the CRBPU RXRE (31). vuunuuy, Widom et al. showed that an orphan closely related to COUP-TF also represses RXR-mediated transactivation through the formation of ARP-1-RXR heterodimers. These data a novel negative regulatory function to the COUP-TF family of orphan receptors and further illustrate that RXR heterodimers can function to negatively regulate gene expression.
