Figure 1.

Summary of the steroid hormone receptor family and visualization of hormone receptor dimerization. (A) Hormone receptors include estrogen receptor (ER), progesterone receptor (PR), glucocorticoid receptor (GR), androgen receptor (AR), and mineralocorticoid receptor (MR). The hormone receptor is composed of the N-terminal domain (A/B), a flexible hinge region (D), and a C-terminal ligand-binding domain (LBD, E). ER, which has two isoforms, ERα and ERβ, is unique in that it contains an additional C-terminal F domain. PR has two isoforms PRA and PRB. The number of amino acid sequences is shown on the right. They have the two transcriptional activation functions through the AF-1, located in the N-terminal domain, and through the AF-2, located in the ligand-binding domain. This is important for forming the coregulator binding site as well as mediating direct interactions between the N-terminal and ligand-binding domains that form and function as homodimers or heterodimers. (B) ER splice variant ERα36 retains the DNA-binding domain but lacks both transactivation domains, AF-1 and AF-2, and differs with the unique C-terminal domain. (C) AR splice variants AR-V7 that contain the N-terminal domain and DNA-binding domain and lacks the LBD; however, the unique C-terminal domain, alternative splicing of the gene truncates the protein leaving only cryptic exon 3 (CE3) at the C-terminus.