Regulation of cytochrome P450 (CYP) genes by nuclear receptors

Members of the nuclear-receptor superfamily mediate crucial physiological f unctions by regulating the synthesis of their target genes. Nuclear recepto rs are usually activated by ligand binding. Cytochrome P450 (CYP) isoforms often catalyse both formation and degradation of these ligands. CYPs also m etabolize many exogenous compounds, some of which may act as activators of nuclear receptors and disrupters of endocrine and cellular homoeostasis. Th is review summarizes recent findings that indicate that major classes of CY P genes are selectively regulated by certain ligand-activated nuclear recep tors, thus creating tightly controlled networks.