Proteasome inhibition blocks estrogen-dependent gene transcription by decreasing histone H2B monoubiquitination in human breast cancer cells

The estrogen receptor-alpha (ERα) determines breast cancer cell phenotype and is a prognostic indicator. A better understanding of the mechanisms controlling ERα function may uncover improved strategies for the treatment of breast cancer. Proteasome inhibition was previously reported to regulate estrogen-induced transcription but the mechanisms by which it influences ERα function remain controversial. In this study we investigated the transcriptome-wide effects of the proteasome inhibitor Velcade on estrogen-regulated transcription in MCF7 human breast cancer cells and demonstrate a specific global decrease in estrogen-induced transcription. This set contains 12 microarray samples. 3 controls, 3 estrogen stimulated, 3 Bortezomib stimulated, 3 Bortezomib + estrogen stimulated