Estrogen receptor target gene: an evolving concept.

Estrogen receptor (ER) functions as a transcription factor to induce gene expression events sufficient for cell division and breast cancer progression. A significant body of work exists on the identification of ER gene targets and the cofactors that contribute to these transcription events, yet surprisingly little is known of the cis-regulatory elements involved. In this review, we investigate the advances in technology that contribute to a comprehensive understanding of ER target genes and explore recent work identifying cis-regulatory domains that augment transcription of these targets. Specifically, we find that ER association with gene targets results from an association with the pioneer factor FoxA1, responsible for recruitment of ER to the genome. Recruitment of ER to the genome does not occur at promoter proximal regions, but instead involves distal enhancer elements that function to tether the ER complex to the target gene promoters. These advances in technology permit a more detailed investigation of ER activity and may aid in the development of superior drug interventions.