Functional and physical interactions between the estrogen receptor Sp1 and nuclear aryl hydrocarbon receptor complexes.
17beta-Estradiol (E2) induces cathepsin D gene expression in MCF-7 human breast cancer cells and previous analyses of the proximal promoter region of this gene identified two functional enhancer sequences; namely an Sp1(N)23estrogen-responsive element (ERE) half-site (-199 to -165) and an imperfect palindromic ERE (-119 to -107). A third region of the cathepsin D gene promoter (CD/L, -145 to -119) was also E2 responsive in transient transfection assays. A GC-rich sequence which contains two overlapping Sp1 binding sites (-145 to -135) was responsible for ER-mediated transactivation and required formation of an ER/Sp1 complex in which only the Sp1 protein bound DNA. E2 responsiveness of the CD/L sequence was also dependent on an adjacent overlapping GCGTG motif corresponding to the dioxin-responsive element (DRE) core binding sequence, which is the cognate response element for the heterodimeric aryl hydrocarbon receptor (AhR)/AhR nuclear translocator (ARNT) transcription factor complex. The results show that ER-mediated transactivation of CD/L was associated with the Sp1(N)2-4DRE (core) motif and involved formation of a multiprotein ER/Sp1-AhR/ARNT complex. These results illustrate a unique example of an endogenous role for AhR/ARNT in the absence of added AhR agonist and indicate that the cathepsin D gene proximal promoter region contains at least three different functional motifs associated with ER-mediated transactivation.
Wang
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F
Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, USA.
Hoivik
D
D
Pollenz
R
R
Safe
S
S
D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001571:Benzoflavones / Q000494:pharmacology; D001667:Binding, Competitive; D001943:Breast Neoplasms; D002402:Cathepsin D / Q000235:genetics*; D002457:Cell Extracts; D004247:DNA / Q000378:metabolism*; D016373:DNA, Antisense; D004268:DNA-Binding Proteins; D004742:Enhancer Elements, Genetic / Q000235:genetics; D004958:Estradiol / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured
C497396:ARNT protein, human; D001571:Benzoflavones; D002457:Cell Extracts; D016373:DNA, Antisense; D004268:DNA-Binding Proteins; D018336:Receptors, Aryl Hydrocarbon; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D004958:Estradiol; C011512:alpha-naphthoflavone; D004247:DNA; D002402:Cathepsin D