Proteomics Analysis of the Estrogen Receptor Receptosome*□S

The estrogen receptors (ERs) are ligand-dependent transcription factors that activate transcription by binding to estrogen response elements. Estrogen-mediated effects are tissueand cell type-specific, determined by the cofactor recruitment to the ERs among other factors. To understand these differences in estrogen action, it is important to identify the various compositions of the ER complexes (ER receptosomes). In this report, we describe a fast and efficient method for the isolation of the ER receptosome for proteomics analysis. Using immobilized estrogen response element on a Sepharose column in combination with two-dimensional electrophoresis and MALDI-TOF MS, significant amounts of proteins could be isolated and identified. Differences in ER complex composition with the ER ligands 17 -estradiol, 4-hydroxytamoxifen, and ICI-182,780 could also be observed. Thus, this approach provides an easy and relevant way of identifying ER cofactor and transcription factor recruitment under different conditions. Molecular & Cellular Proteomics 9:1411–1422, 2010.