Nuclear receptors are one of the most abundant classes of transcriptional regulators in animals (metazoans). They regulate diverse functions, such as homeostasis, reproduction, development and metabolism (for a review, seeLaudet and Gronemeyer, 2002). Nuclear hormone receptors function as ligand-activated transcription factors,and thus provide a direct link between signaling molecules that control these processes and transcriptional responses. A large number of nuclear receptors have been identified through sequence similarity to known receptors, but have no identified natural ligand, and are referred to as `nuclear orphan receptors'. As nuclear receptors bind small molecules that can easily be modified by drug design, and control functions associated with major diseases(e.g. cancer, osteoporosis and diabetes), they are promising pharmacological targets. The search for ligands for orphan receptors and the identification of novel signaling pathways has become a very active research field(Gustafsson, 1999;Kliewer et al., 1999).FIG1
Nuclear receptors share...
