title: Estrogen up-regulation of p53 gene expression in MCF-7 breast cancer cells is mediated by calmodulin kinase IV-dependent activation of a nuclear factor kappaB/CCAAT-binding transcription factor-1 complex.
abstract: This study investigates the mechanism of hormonal regulation of p53 gene expression in MCF-7 human breast cancer cells. 17beta-Estradiol (E2) induced a 2-fold increase in p53 mRNA levels and a 2- to 3-fold increase in p53 protein. Analysis of the p53 gene promoter has identified a minimal E2-responsive region at -106 to -40, and mutation/deletion analysis of the promoter showed that motifs that bind CCAAT-binding transcription factor-1 (CTF-1) and nuclear factor kappaB (NFkappaB) proteins are required for hormone responsiveness. The p65 subunit of NFkappaB was identified in both nuclear and cytosolic fractions of untreated MCF-7 cells; however, formation of the nuclear NFkappaB complex was E2 independent. Hormonal activation of constructs containing p53 promoter inserts (-106 to -40) and the GAL4-p65 fusion proteins was inhibited by the intracellular Ca2+ ion chelator EGTA-AM and Ca2+/calmodulin-dependent protein kinase (CaMK) inhibitor KN-93. Constitutively active CaMKIV but not CaMKI activated p65, and treatment of MCF-7 cells with E2 induced phosphorylation of CaMKIV but not CaMKI. The results indicate that hormonal activation of p53 though nongenomic pathways was CaMKIV-dependent and involved cooperative p65-CTF-1 interactions.
authors.affiliation: Department of Veterinary Physiology & Pharmacology, Texas A&M University, College Station, Texas 77843-4466, USA.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Qin
authors.forename: Thu
authors.initials: T
authors.lastname: Nguyen
authors.forename: Jessica
authors.initials: J
authors.lastname: Stewart
authors.forename: Ismael
authors.initials: I
authors.lastname: Samudio
authors.forename: Robert
authors.initials: R
authors.lastname: Burghardt
authors.forename: Stephen
authors.initials: S
authors.lastname: Safe
mesh_terms: D001483:Base Sequence; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D016158:Genes, p53 / Q000187:drug effects*; D006801:Humans; D046911:Macromolecular Substances; D016328:NF-kappa B / Q000378:metabolism*; D051839:NFI Transcription Factors; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D051996:Transcription Factor RelA; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; C077305:CTF-1 transcription factor; D004273:DNA, Neoplasm; D046911:Macromolecular Substances; D016328:NF-kappa B; D051839:NFI Transcription Factors; D051996:Transcription Factor RelA; D014157:Transcription Factors; D004958:Estradiol; D017871:Calcium-Calmodulin-Dependent Protein Kinases