Vertebrate receptors: molecular biology, dimerization and response elements.

The nuclear receptors are a large family of ligand sensitive transcriptional regulators. They bind specific DNA sequences (response elements) in the promoter region of responsive genes. While the steroid hormone receptors bind as homodimers just two basic response elements, the retinoid and thyroid hormone receptor family interacts with a diverse set of response elements as homo- and heterodimers. The retinoid X receptors have a central role, since they form heterodimers with a whole subclass of receptors, consistent with the pleiotropic effects of retinoids. Differences in the mechanism of actions between steroid hormone receptors and other members of the family are discussed.