Gene expression profiling reveals that the regulation of estrogen-responsive element-independent genes by 17β-estradiol-estrogen receptor β is uncoupled from the induction of phenotypic changes in cell models

Abstract

Estrogen hormone 17β-estradiol (E2) is involved in the physiology and pathology of many tissues. E2 information is conveyed by the transcription factors estrogen receptors (ER) α and β that mediate a complex array of nuclear and non-nuclear events. The interaction of ER with specific DNA sequences, estrogen-responsive elements (EREs), constitutes a critical nuclear signaling pathway. In addition, E2-ER regulates transcription through interactions with transfactors bound to their cognate regulatory elements on DNA, hence the ERE-independent signaling pathway. However, the relative importance of the ERE-independent pathway in E2-ERβ signaling is unclear. To address this issue, we engineered an ERE-binding defective ERβ mutant (ERβEBD) by changing critical residues in the DNA-binding domain required for ERE binding. Biochemical and functional studies revealed that ERβEBD signaled exclusively through the ERE-independent pathway. Using the adenovirus infected ER-negative cancer cell models, we found that although E2-ERβEBD regulated the expression of a number of genes identified by microarrays, it was ineffective in altering cellular proliferation, motility, and death in contrast to E2-ERβ. Our results indicate that genomic responses from the ERE-independent pathway to E2-ERβ are not sufficient to alter the cellular phenotype. These findings suggest that the ERE-dependent pathway is a required signaling route for E2-ERβ to induce cellular responses.