Journal of Molecular Endocrinology

Domain organization of NRs and their interaction partners. (A) NR polypeptides have an N-terminal domain (NTD) that is variable in size and sequence, a conserved DBD, a variable hinge region, and a 12-helical LBD. Several NRs also contain a variable F-domain positioned at their C-termini. (B) Schematic showing how a dimeric NR uses different domains to bind to DNA and ligand. (C) NRs can be modulated by ligands that either activate or repress gene targets. Repression is mediated by complexes that have corepressors (SMRT/N-CoR and histone deacetylases (HDACs)), among other components. Activation requires the coactivator complexes (p160 family members and histone acetyltransferase (HAT)). The repressive and activating complexes block or promote transcription. (D) Oligomeric complexes of NRs and DNA response element repertoires. Receptors can be organized into distinct oligomeric states such as heterodimers with the common partner retinoid X receptor (RXR), homodimers, or monomers. The non-steroid receptor heterodimers and many homodimers bind to direct repeat response elements with various inter-half-site spacings. Steroid receptor homodimers mainly use palindromic DNA elements, where the two half sites are in an inverted repeat arrangement. Other receptors use monomeric sites extended at their 5′-end with short sequences used for selectivity. Several examples of receptors falling into each of these four categories are shown.