Background：

Ligand-activated transcription factor. Receptor for bile acids such as chenodeoxycholic acid， lithocholic acid， deoxycholic acid and allocholic acid. Plays a essential role in BA homeostasis through the regulation of genes involved in BA synthesis， conjugation and enterohepatic circulation. Also regulates lipid and glucose homeostasis and is involved innate immune response. The FXR-RXR heterodimer binds predominantly to farnesoid X receptor response elements (FXREs) containing two inverted repeats of the consensus sequence 5’-AGGTCA-3’ in which the monomers are spaced by 1 nucleotide (IR-1) but also to tandem repeat DR1 sites with lower affinity， and can be activated by either FXR or RXR-specific ligands.