title: DeltaN133p53 expression levels in relation to haplotypes of the TP53 internal promoter region.
abstract: The transcription of the DeltaN133p53 isoform of the TP53 gene is controlled by an internal promoter region (IPR) containing eight polymorphisms in 11 common haplotypes, following a resequencing of 47 Caucasians. We assayed the functional effects of the commonest six haplotypes on the promoter activity with a luciferase reporter system, in HeLa and 293T cells. These studies showed that different IPR haplotypes are associated with differences in the promoter activity resulting in marked variation in the baseline expression of DeltaN133p53. In vivo quantitative-polymerase chain reaction (PCR) on human tissues confirmed that the baseline levels of DeltaN133p53 showed haplotype specific differences that paralleled those seen in vitro. When cell lines were treated with camptothecin, the fold-increase in DeltaN133p53 levels was dose-dependent but haplotype-independent (i.e., similar for all the haplotypes). Finally, we used an electrophoretic mobility shift assay to analyze the rs1794287 polymorphism and found changes in the pattern of protein binding. This partially confirmed our in silico analysis showing that the polymorphism rs1794287 can affect the function of the internal promoter by changing its affinity for several transcription factors. Thus, we showed that the expression of DeltaN133p53 is under genetic control, and suggested the presence of interindividual differences underlying this mechanism.
authors.affiliation: Department of Biology, University of Pisa, Via Derna 1, Pisa, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Bellini
authors.forename: Letizia
authors.initials: L
authors.lastname: Pitto
authors.forename: Maria G
authors.initials: MG
authors.lastname: Marini
authors.forename: Loredana
authors.initials: L
authors.lastname: Porcu
authors.forename: Paolo
authors.initials: P
authors.lastname: Moi
authors.forename: Sonia
authors.initials: S
authors.lastname: Garritano
authors.forename: Laura
authors.initials: L
authors.lastname: Boldrini
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rainaldi
authors.forename: Gabriella
authors.initials: G
authors.lastname: Fontanini
authors.forename: Massimo
authors.initials: M
authors.lastname: Chiarugi
authors.forename: Roberto
authors.initials: R
authors.lastname: Barale
authors.forename: Federica
authors.initials: F
authors.lastname: Gemignani
authors.forename: Stefano
authors.initials: S
authors.lastname: Landi
mesh_terms: D019295:Computational Biology; D004247:DNA / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D006239:Haplotypes / Q000235:genetics*; D006367:HeLa Cells; D006720:Homozygote; D006801:Humans; D007438:Introns / Q000235:genetics; D008156:Luciferases / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
chemical_list: D050505:Mutant Proteins; D020033:Protein Isoforms; D016159:Tumor Suppressor Protein p53; D004247:DNA; D008156:Luciferases