title: Identification and characterization of a response element in the EGFR promoter that mediates transcriptional repression by 1,25-dihydroxyvitamin D3 in breast cancer cells.
abstract: Reduction of epidermal growth factor receptor (EGFR) mRNA and protein by 1,25-dihydroxyvitamin D3 has been documented in MCF7, T47D, and BT549 breast cancer cells. In the present report, functional mapping of the EGFR promoter in BT549 cells has revealed a sequence of DNA between nucleotide positions -536 and -478 that resembles a consensus vitamin D response element (VDRE) and confers a vitamin D response upon both the homologous and a minimal heterologous promoter. In vitro footprinting and gel shift assays demonstrate the presence of an unidentified nuclear factor that is required for strong binding of the vitamin D receptor (VDR) to this putative VDRE. An Sp1 binding site was also identified in close proximity and shown to bind Sp1 from nuclear extract. Mutational analysis and functional studies using a minimal heterologous promoter provide evidence that the VDR in concert with an unknown nuclear partner mediates basal EGFR repression through displacement of Sp1 which is augmented in the presence of a ligand.
authors.affiliation: Vincent T Lombardi Cancer Center, Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, DC 20007, USA. krmcgaffin@aol.com
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: McGaffin
authors.forename: Susan A
authors.initials: SA
authors.lastname: Chrysogelos
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002874:Chromosome Mapping; D018983:DNA Footprinting; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000378:metabolism; D012965:Sodium Chloride; D016329:Sp1 Transcription Factor / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D004273:DNA, Neoplasm; D008024:Ligands; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D018167:Receptors, Calcitriol; D016329:Sp1 Transcription Factor; D012965:Sodium Chloride; D066246:ErbB Receptors; D002117:Calcitriol