Extended data figure 1. Protein purification of ERα and PR interacting proteins, using RIME, following treatment with a synthetic progestin.

T-47D and MCF-7 breast cancer cells were grown in SILAC-isotope containing media and treated with either vehicle control or R5020, a synthetic progestin for 3hr. PR (a) or ERα (b) RIME was conducted and the proteins that were quantitatively enriched in both cell lines are shown. Only proteins that were enriched with a FDR < 1% were included. c. Peptide coverage of the PR protein following ERα RIME in T-47D cells. The identified peptides are highlighted and one of the peptides covers the ‘Bus’ region representing the PR-B isoform. d. Comparison of binding at different time points and treatment of MCF-7 breast cancer cells with progesterone. ERα ChIP-seq at 3hr and 24hrs results in comparable binding. Correlation between Progesterone (PG) and R5020 (RO) at 3 and 24 hrs. e. MCF-7 cells were grown in estrogen rich complete media and treated with progesterone or vehicle control for 3hr. ERα ChIP was conducted and peaks that occurred in at least two of three independent replicates were considered. Venn diagram showing the changes in ERα binding following progesterone treatment of MCF-7 cells. f. Uncropped Western blots from Figure 1c.