title: Estrogen-induced c-fos protooncogene expression in MCF-7 human breast cancer cells: role of estrogen receptor Sp1 complex formation.
abstract: 17Beta-estradiol (E2) induces c-fos protooncogene expression in MCF-7 human breast cancer cells, and previous studies in HeLa cells identified an imperfect palindromic estrogen-responsive element (-1212 to -1200) that was required for trans-activation. In contrast, the estrogen-responsive element was not required for E2 responsiveness in MCF-7 cells, and using a series of constructs containing wild-type (pF1) and mutant 5'-flanking sequences (-1220 to -1155) from the c-fos protooncogene promoter in transient transfection assays, it was shown that a GC-rich motif (5'-GGGGCGTGG) containing an imperfect Sp1-binding site was required for hormone-induced activity. This sequence also bound Sp1 protein in gel mobility shift assays, and coincubation with the estrogen receptor (ER) enhanced Sp1-DNA binding. E2 and 4'-hydroxytamoxifen, but not ICI 164,384, induced reporter gene activity in cells transiently transfected with pF1. E2 induced reporter gene activity in MDA-MB-231 breast cancer cells transiently cotransfected with pF1 and wild-type ER or variant ER in which the DNA-binding domain was deleted (HE11); plasmids expressing N-terminal or C-terminal domains of the ER containing activator function-1 or -2, respectively, were inactive in these assays. In contrast, only wild-type ER mediated 4'-hydroxytamoxifen-induced activity. Induction of c-fos protooncogene expression by E2 in MCF-7 cells is dependent on the formation of a transcriptionally active ER/Sp1 complex that binds to a GC-rich enhancer element.
authors.affiliation: Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station 77843-4466, USA.
authors.forename: R
authors.initials: R
authors.lastname: Duan
authors.forename: W
authors.initials: W
authors.lastname: Porter
authors.forename: S
authors.initials: S
authors.lastname: Safe
mesh_terms: D001665:Binding Sites; D001943:Breast Neoplasms / Q000378:metabolism*; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D017353:Gene Deletion; D015870:Gene Expression / Q000187:drug effects*; D016762:Genes, fos / Q000235:genetics*; D006801:Humans; D016296:Mutagenesis; D011401:Promoter Regions, Genetic; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D004965:Estrogen Antagonists; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol; D015500:Chloramphenicol O-Acetyltransferase