Allosteric modulation of estrogen receptor conformation by different estrogen response elements

Estrogen-regulated gene expression is dependent on interaction of the estro gen receptor (ER) with the estrogen response element (ERE). We assessed the ability of the ER to activate transcription of reporter plasmids containin g either the consensus vitellogenin A2 ERE or the imperfect pS2, vitellogen in B1, or oxytocin (OT) ERE. The A2 ERE was the most potent activator of tr anscription. The OT ERE was significantly more effective in activating tran scription than either the pS2 or B1 ERE. In deoxyribonuclease 1 (DNase I) f ootprinting experiments, MCF-7 proteins protected A2 and OT EREs more effec tively than the pS2 and B1 EREs. limited protease digestion of the A2, pS2, B1, or OT ERE-bound receptor with V8 protease or proteinase K produced dis tinct cleavage products demonstrating that individual ERE sequences induce specific changes in ER conformation. Receptor interaction domains of glucoc orticoid receptor interacting protein 1 and steroid receptor coactivator 1 bound effectively to the A2, pS2, B1, and OT ERE-bound receptor and signifi cantly stabilised the receptor-DNA interaction. Similar levels of the full- length p160 protein amplified in breast cancer 1 were recruited from HeLa n uclear extracts by the A2, pS2, B1, and OT ERE-bound receptors. In contrast , significantly less transcriptional intermediary factor 2 was recruited by the B1 ERE-bound receptor than by the A2 ERE-bound receptor. These studies suggest that allosteric modulation of ER conformation by individual ERE se quences influences the recruitment of specific coactivator proteins and lea ds to differential expression of genes containing divergent ERE sequences.