Putative ERβ primary targets. Left: Heatmap summarizing the effects of estrogen stimulation on 424 mRNAs encoded by genes showing one (left) or more (right) ERβ binding sites within 10 kb of the TU (primary response genes) transcriptome of MCF-7 cells, as changes in expression (log2 of the fold-change) after cell exposure to 10-8M E2 for the indicated times. Transcripts are grouped as follows: regulated only in wt MCF-7 cells (1), in both cell lines (2) and only in TAP-ERβ cells (3). Vertical bars to the right of each heatmap indicate the class of ERβ binding site present, as indicated in the legend. When a regulated gene showed multiple ERβ binding sites belonging to different classes it was included in a separate group, classified as 'combination of ERβ sites' (grey bar).Right: Genome Browser view of genomic loci representative of the different ERα and ERβ binding site categories identified. ChIP-Seq ERα and ChIP-Seq ERβ indicate sites identified in this study, ChIP-Seq ERα1, ChIP-Seq ERα2 and ChIP-on-chip indicates sites identified in MCF-7 cells by Cicatiello et al. , Fullwood et al. , and Hurtado et al. , respectively.