Regulation of xenobiotic metabolism by orphan nuclear receptors

Nuclear receptors control gene transcription by binding to specific promote r regions of DNA in the presence of ligand. Orphan nuclear receptors, are n uclear receptors for which the endogenous ligand(s) has yet to be identifie d. Systematic evaluation of orphan nuclear receptors can elucidate species differences in xenobiotic metabolism in addition to aiding in identificatio n of endogenous ligands. The receptor-binding affinity and specificity of v arious chemicals, with subsequent determination of the genes controlled by nuclear receptors. are goals of investigations into orphan nuclear receptor structure/function and can provide valuable tools in predicting drug inter actions and toxicity.