| Retinoids are metabolites of vitamin A (retinol) that represent an important group of signaling molecules during vertebrate development and tissue differentiation. Retinoic acid receptors (RARs) include RARi, RARi and RARi, each of which has a high affinity for all transretinoic acids. Members of the retinoid X receptor (RXR) family, RXRi, RXRi1, RXRi2 and RXRi, are activated by 9-cis-retinoic acid, a stereo- and photoisomer of all transretinoic acids that is expressed in vivo in both liver and kidney and may represent a widely used hormone. The RAR-related orphan nuclear receptors (ROR) bind DNA as monomers and include RORi, RORi and RORi. DAX-1 binds to retinoic acid response elements to mediate transcription. FXR (activated by farnesol and related metabolites) binds RXR to form a heterodimer, which subsequently binds IR-1 elements. |
