MODULATION OF ESTROGEN-RECEPTOR ACTIVITY BY ESTROGENS AND ANTIESTROGENS

The oestrogen receptor is a member of a supergene family that includes receptors for steroid and thyroid hormones, vitamin D3, and retinoic acid. A number of additional members of the family have been cloned where the putative ligand remains to be identified. The oestrogen receptor is a ligand-activated transcription factor that modulates specific gene expression by binding to short DNA sequences (oestrogen response elements) located in the vicinity of oestrogen-regulated genes. Regions of the receptor responsible for hormone-binding, DNA-binding and activation of transcription, have been identified. The anti-oestrogen, tamoxifen (Nolvadex), behaves as a weak oestrogen agonist. A model, based upon our current understanding of the molecular mechanism of oestrogen action, will be presented to explain the cell and gene specific effects of some anti-oestrogens.