Analysis of the Phosphorylated Estrogen Receptor-α Cistrome Reveals Association with Direct ER-DNA Binding and the Transcription Factor GRHL2. Analysis of the Phosphorylated Estrogen Receptor-α Cistrome Reveals Association with Direct ER-DNA Binding and the Transcription Factor GRHL2

Phosphorylation of the estrogen receptor-α (ER) at serine 118 (pS118-ER) is involved in modulating ER-dependent gene transcription and recruitment of ER to certain gene promoters. While the effects of pS118 on ER-DNA interactions have been investigated at specific sites, the genome-wide binding profile (cistrome) of pS118-ER remains to be studied. To characterize the pS118-ER cistrome, ChIP-seq was performed on pS118-ER and pan-ER in MCF-7 cells. A subset of ER sites was occupied by pS118-ER and these sites were associated with the active enhancer mark H3K27ac. Additionally, pS118-ER sites were found to be enriched in the DNA binding motif for GRHL2 as well as the estrogen response element relative to all ER sites. Utilizing a DNA binding microarray, pS118-ER was found to be more commonly associated with direct DNA binding events compared to indirect binding events. These results suggest a role for pS118-ER at active enhancers and as a regulator of direct ER-DNA interactions. Overall design: MCF-7 cells were treated with 10 nM 17ß-estradiol for 30 min prior to ChIP assay, library creating, and sequencing