ESR1 and breast cancer: ENCODE ChIP-Seq data reveals binding of several transcription factors (TFs) within 500 bp of the transcriptional start site (TSS) of promoter A. FOXA1, GATA3 and ERα interact with the promoter in the T-47D BC cell line and CTCF, MYC and POLR2A interact in the MCF-7 cell line.