Phosphorylation of Estrogen Receptor α at Serine 118 Directs Recruitment of Promoter Complexes and Gene-Specific Transcription

Phosphorylation of estrogen receptor alpha (ER alpha) is important for receptor function, although the role of specific ER alpha phosphorylation sites in ER alpha-mediated transcription remains to be fully evaluated. Transcriptional activation by ER alpha involves dynamic, coordinate interactions with coregulators at promoter enhancer elements to effect gene expression. To determine whether ER alpha phosphorylation affects recruitment of unique protein complexes at gene-specific promoters, changes in ER alpha Ser118 phosphorylation were assessed for effects on receptor and coregulator recruitment and transcription of ER alpha-regulated genes. Chromatin immunoprecipitation assays to measure promoter association found a 17 beta-estradiol (E2)-dependent recruitment of ER alpha at 150 min to ER alpha-regulated promoters, whereas ER alpha phosphorylated at Ser118 was dissociated from promoters after E2 treatment. Mutation of Ser118 to alanine (S118A) altered unliganded and ligand-induced association of ER alpha and p160 coregulators with E target promoters when compared with wild-type (WT)-ER alpha transfection. S118A and WT-ER alpha exhibited a similar level of recruitment to the estrogen response element-driven pS2 promoter and induced pS2 mRNA after E2 treatment. Although WT-ER alpha was recruited to c-myc and cyclin D1 promoters after E2 treatment and induced mRNA expression, S118A exhibited reduced interaction with c-myc and cyclin D1 promoters, and E2 did not induce c-myc and cyclin D1 mRNA. In addition, S118A resulted in increased recruitment of steroid receptor coactivator-1, glucocorticoid receptor interacting protein-1, and activated in breast cancer-1 to pS2, c-myc, and cyclin D1 irrespective of the presence of E2. Together, these data indicate that site specific phosphorylation of ER alpha directs gene-specific recruitment of ER alpha and transcriptional coregulators to ER alpha target gene promoters. (Endocrinology 152: 2517-2526, 2011)