Genomic responses from the estrogen-responsive element-dependent signaling pathway mediated by estrogen receptor α are required to elicit cellular alterations

Abstract

Estrogen (E2) signaling is conveyed by the transcription factors estrogen receptor (ER) α and β. ERs modulate the expression of genes involved in cellular proliferation, motility, and death. The regulation of transcription by E2-ERα through binding to estrogen-responsive elements (EREs) in DNA constitutes the ERE-dependent signaling pathway. E2-ERα also modulates gene expression by interacting with transregulators bound to cognate DNA-regulatory elements, and this regulation is referred to as the ERE-independent signaling pathway. The relative im portance of the ERE-independent pathway in E2-ERα signaling is unclear. To address this issue, we engineered an ERE-binding defective ERα mutant (ERα EBD) by changing residues in an α-helix of the protein involved in DNA binding to render the receptor functional only through the ERE-independent signaling pathway. Using recombinant adenovirus-infected ER-negative MDA-MB-231 cells derived from a breast adenocarcinoma, we found that E2-ERαEBD modulated the expression of a subset of ERα-responsive genes identified by microarrays and verified by quantitative PCR. However, E2-ERα EBD did not affect cell cycle progression, cellular growth, death, or motility in contrast to E2-ERα. ERα EBD in the presence of E2 was also ineffective in inducing phenotypic alterations in ER-negative U-2OS cells derived from an osteosarcoma. E2-ERα, on the other hand, effectively repressed growth in this cell line. Our findings suggest that genomic responses from the ERE-dependent signaling pathway are required for E2-ERα to induce alterations in cellular responses. © 2009 by The American Society for Biochemistry and Molecular Biology, Inc.