FIG. 7.

Schematic representation of estrogen-dependent transcription factor assembly on the CCND1 gene promoter in hormone-responsive hBC cells and their interactions with each other, the distal regulatory sites, and the basal promoter. In hormone-deprived, quiescent cells, HDAC1 is present in a complex with YY1 on the ERGE. Upon estrogen (or progesterone) stimulation, these trans-repressors are displaced from DNA by a composite AP-1/ER (or PR) complex and Oct-1, inducing physical interactions of ERGE-bound complexes with the basal transcriptional machinery. At a later time (>1 h), the cyclin D1 (Cyc D1)/Cdk4 holoenzyme associates with the complex, presumably relieving the promoter from trans-repression and thereby inducing a second, longer-lasting enhancement of transcription. This event may be accompanied by Oct-1 release from ERGE. Ac, acetylated histone tails.