title: A HOXA10 estrogen response element (ERE) is differentially regulated by 17 beta-estradiol and diethylstilbestrol (DES).
abstract: The molecular mechanisms by which estrogens regulate developmental gene expression are poorly understood. While 17 beta-estradiol is normally present at high concentrations in pregnancy, exposure to the estrogen diethylstilbestrol (DES) in utero induces developmental anomalies of the female reproductive tract. HOX gene expression is altered by DES, leading to abnormal Müllerian duct differentiation. The mechanism of ligand-specific regulation of HOX gene expression by estrogens has not been characterized. To elucidate the molecular mechanism underlying ligand-specific estrogen regulation of HOXA10 expression, we characterized regulatory regions of the human HOXA10 gene. We identified an estrogen response element (ERE) in the human HOXA10 gene that mediated differential ligand-specific estrogen-responsive transcriptional activation. Deletional analysis and reporter expression assays identified two EREs, ERE1 and ERE2, each of which drove estrogen-responsive reporter expression in the Ishikawa human uterine endometrial adenocarcinoma cell line. ERE1 drove reporter expression maximally. This ERE bound ERalpha and ERbeta, and formed a complex that included SRC-1, but not CBP, N-CoR or SMRT. HOXA10 ERE1 drove luciferase reporter activity to eightfold the level driven by the consensus ERE in response to estradiol in Ishikawa cells. While most EREs demonstrate similar transcriptional activity in response to DES or estradiol, here estradiol induced four- to sevenfold greater reporter activity than did DES from HOXA10 ERE1. DES did not alter ER or SRC-1 binding to HOXA10 ERE1. HOXA10 ERE1 therefore demonstrated ligand specificity distinct from the consensus ERE, and unrelated to changes in ER or coactivator/corepressor binding. The ligand specificity of the HOXA10 ERE may explain the molecular mechanism by which DES leads to reproductive anomalies; differential ligand-specific activation of HOX genes may be a molecular mechanism by which DES signaling leads to inappropriate HOX expression and to developmental patterning distinct from that induced by estradiol.
authors.affiliation: Yale University School of Medicine, Division of Reproductive Endocrinology, P.O. Box 208063, 333 Cedar Street, New Haven, CT 06520-8063, USA.
authors.forename: G Eda
authors.initials: GE
authors.lastname: Akbas
authors.forename: Joon
authors.initials: J
authors.lastname: Song
authors.forename: Hugh S
authors.initials: HS
authors.lastname: Taylor
mesh_terms: D001483:Base Sequence; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D004054:Diethylstilbestrol / Q000378:metabolism / Q000494:pharmacology*; D024202:Electrophoretic Mobility Shift Assay; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology*; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D005786:Gene Expression Regulation / Q000187:drug effects*; D000080905:Homeobox A10 Proteins; D018398:Homeodomain Proteins; D006801:Humans; D008024:Ligands; D011485:Protein Binding; D011960:Receptors, Estrogen / Q000378:metabolism; D020218:Response Elements / Q000235:genetics*; D013379:Substrate Specificity
chemical_list: D004268:DNA-Binding Proteins; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D000080905:Homeobox A10 Proteins; D018398:Homeodomain Proteins; D008024:Ligands; D011960:Receptors, Estrogen; C069634:HOXA10 protein, human; D004958:Estradiol; D004054:Diethylstilbestrol