The ESR1 gene is a target of regulation by the cohesin and Mediator complexes. (A) A snapshot from the UCSC genome browser showing the structure of the ESR1 gene and cohesin binding sites previously identified by chromatin immunoprecipitation-sequencing (ChIP-Seq). The indicated positions shown for the investigated cohesin binding sites as well as the transcriptional start site (TSS) and the 3′ end. (B-E) MCF7 cells transfected with control, SMC3 or MED12 siRNAs for 24 h were grown in estrogen-free medium for an additional 48 h. SMC3 (B), MED12 (C), RNAPII (D) and RNAPII P-Ser2 (E) binding to the transcriptional start site (TSS), two different cohesin binding sites (Coh. A and B), and the 3′ end (A) was analyzed using specific antibodies by chromatin immunoprecipitation analysis. ChIP samples were normalized to input samples and expressed as % input; mean values + SD, n = 3. The dotted line indicates the background binding as measured by the average signal of non-specific IgG binding across all samples and sites.