DNA Binding by Estrogen Receptor-α Is Essential for the Transcriptional Response to Estrogen in the Liver and the Uterus

The majority of the biological effects of estrogens in the reproductive tract are mediated by estrogen receptor (ER)alpha, which regulates transcription by several mechanisms. Because the tissue-specific effects of some ER alpha ligands may be caused by tissue-specific transcriptional mechanisms of ER alpha, 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 ER alpha. The EAAE mutant harbors amino acid exchanges at four positions of the DNA-binding domain (DBD) of ER alpha. This construct was knocked in the ER alpha gene locus to produce ER alpha((EAAE/ EAAE)) mice devoid of a functional ER alpha DBD. The phenotype of the ER alpha((EAAE/EAAE)) mice resembles the general loss-of-function phenotype of alpha ER knockout mutant mice with hypoplastic uteri, hemorrhagic ovaries, and impaired mammary gland development. In agreement with this phenotype, the expression pattern of the ER alpha((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 ER alpha rely on an intact DBD in vivo. (Molecular Endocrinology 23: 1544-1555, 2009)