Ligand binding domain of chicken ovalbumin upstream promoter transcription factors, a member of the nuclear receptor family
The ligand binding domain of chicken ovalbumin upstream promoter transcription factors (COUP-TFs): COUP-TFs are orphan members of the steroid/thyroid hormone receptor superfamily. They are expressed in many tissues and are involved in the regulation of several important biological processes, such as neurogenesis, organogenesis, cell fate determination, and metabolic homeostasis. In mammals two isoforms named COUP-TFI and COUP-TFII have been identified. Both genes show an exceptional homology and overlapping expression patterns, suggesting that they may serve redundant functions. Although COUP-TF was originally characterized as a transcriptional activator of the chicken ovalbumin gene, COUP-TFs are generally considered to be repressors of transcription for other nuclear hormone receptors, such as retinoic acid receptor (RAR), thyroid hormone receptor (TR), vitamin D receptor (VDR), peroxisome proliferator activated receptor (PPAR), and hepatocyte nuclear factor 4 (HNF4). Like other members of the nuclear receptor (NR) superfamily of ligand-activated transcription factors, COUP-TFs have a central well cons erved DNA binding domain (DBD), a variable N-terminal domain, a flexible hinge and a C-terminal ligand binding domain (LBD).