Estradiol and Tamoxifen Mediate Rescue of the Dominant-Negative Effects of Estrogen Response Element-Binding Protein in Vivo and in Vitro
AUTOR(ES)
Chen, Hong
FONTE
The Endocrine Society
RESUMO
Biological responses to estrogens are dependent on the integrated actions of proteins, including the estrogen receptor (ER)-α, that regulate the transcription of estrogen response element (ERE)-containing target genes. We have identified a naturally occurring ERE antagonist, termed an ERE-binding protein (BP). To verify that ERE-BP can induce estradiol (E2) resistance in vivo, we generated transgenic mice that overexpress this protein in breast tissue. Female transgenic mice with high levels of ERE-BP were unable to lactate, and we hypothesized that this effect was dependent on the relative levels of ERE-BP and ERα ligand. To test this hypothesis, wild-type and ERE-BP-expressing female mice were implanted with capsules containing E2, the selective estrogen receptor modulator tamoxifen, or placebo. Histological analysis of nonlactating mammary glands showed a 4.5-fold increase in gland branch number and 3.7-fold increase in ducts in ERE-BP mice treated with E2 (7.5 mg, 21 d) compared with placebo-treated ERE-BP mice. Wild-type mice showed a 5.3-fold increase in branches and 1.4-fold increase in ducts under the same conditions. Similar results were obtained with tissue from lactating mice, in which tamoxifen also increased mammary gland branch number. Studies using ERE-BP-expressing MCF-7 breast cells showed that high doses of E2 (1000 nm) restored normal ERα-chromatin interaction in these cells, whereas tamoxifen was able to achieve this effect at a dose of 10 nm. These data highlight the importance of ERE-BP as an attenuator of normal ERα signaling in vivo and further suggest that ERE-BP is a novel target for modulation by selective estrogen receptor modulators.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2671906Documentos Relacionados
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