DNA binding by estrogen receptor-α is essential for the transcriptional response to estrogen in the liver and the uterus

Abstract

The majority of the biological effects of estrogens in the reproductive tract are mediated by estrogen receptor (ER)α, which regulates transcription by several mechanisms. Because the tissue-specific effects of some ERα ligands may be caused by tissue-specific transcriptional mechanisms of ERα, we aimed to identify the contribution of DNA recognition to these mechanisms in two clinically important target organs, namely uterus and liver. We used a genetic mouse model that dissects DNA binding-dependent vs. independent transcriptional regulation elicited by ERα. The EAAE mutant harbors amino acid exchanges at four positions of the DNA-binding domain (DBD) of ERα. This construct was knocked in the ERα gene locus to produce ERα (EAAE/EAAE) mice devoid of a functional ERα DBD. The phenotype of the ERα (EAAE/EAAE) mice resembles the general loss-of-function phenotype of αER knockout mutant mice with hypoplastic uteri, hemorrhagic ovaries, and impaired mammary gland development. In agreement with this phenotype, the expression pattern of the ERα (EAAE/EAAE) mutant mice in liver obtained by genome-wide gene expression profiling supports the observation of a near-complete loss of estrogen-dependent gene regulation in comparison with the wild type. Further gene expression analyses to validate the results of the microarray data were performed by quantitative RT-PCR. The analyses indicate that both gene activation and repression by estrogen-bound ERα rely on an intact DBD in vivo. Copyright © 2009 by The Endocrine Society.