FIGURE 2.

Rhein as a selective RXRα antagonist. A, chemical structures of rhein. B, rhein repressing the 9-cis-retinoic acid-induced transcription of GAL4DBD-RXRαLBD by mammalian one hybrid. However, rhein exhibits no activities on the transcription of GAL4DBD-PPARγLBD, GAL4DBD-FXRLBD, and GAL4DBD-LXRαLBD. C, transactivation assays indicating that rhein represses all RXRα-involved dimeric transcription, including RXRE, PPRE, FXRE, and LXRE, mediated by RXRα/RXRα homodimer, RXRα/PPARγ, RXRα/FXR, and RXRα/LXRα heterodimers, respectively.