This is the very C-terminal region of a subfamily of nuclear receptors that includes oestrogen receptors and other subfamily 3 group A members. The actual function of this region is not known, but the domain is absent from all the other types of nuclear receptors. Oestrogen receptors modulate AP-1-dependent transcription [1] through two distinct mechanisms: via protein-protein interactions on DNA; and via non-genomic actions. The mechanism used depends on the cellular localisation of the receptor. In addition to the more extensively studied cross-talk on DNA, additional non-genomic actions might be very important in target tissues in which membrane-associated ERs are found. These non-genomic actions probably contribute to the overall physiological responses mediated by ligand-bound ERs [2] and might possibly be mediated via this C-terminal domain.

1: Estrogen receptor interaction with co-activators and co-repressors. Klinge CM; Steroids. 2000;65:227-251. PMID:10751636

2: Estrogen receptor-dependent activation of AP-1 via non-genomic signalling. Bjornstrom L, Sjoberg M; Nucl Recept. 2004;2:3. PMID:15196329