ABSTRACT
Estrogen’s effects on endometrial tissue are mediated by the hormone-regulated transcription factor, the estrogen receptor (ER). Ligand-modulated nuclear transcription factors, including the ER, share a general domain structure, domains A-F1-3 (Figure 12.1). The C domain encodes the ER’s DNA-binding domain (DBD), which includes two zinc finger motifs responsible for recognition and binding to specific DNA sequences (estrogen responsive elements [EREs]). ER primarily binds as a symmetrical homodimer to ERE sequences, with each ER molecule contacting one arm of the 5 base pair inverted repeat.4-6 The consensus ERE sequence is a 13 base pair inverted repeat sequence, GGTCAnnnTGACC;5 however the majority of response element sequences contain one or more variations from the consensus. In addition, ER can interact with ERE half-sites when there is a nearby Sp1 site.7
