title: The phosphotyrosyl phosphatase activator gene is a novel p53 target gene.
abstract: The minimal promoter of the phosphotyrosyl phosphatase activator (PTPA) gene, encoding a regulator of protein phosphatase 2A contains two yin-yang 1 (YY1)-binding sites, positively regulating promoter activity. We now describe a role for p53 in the regulation of PTPA expression. Luciferase reporter assays in Saos-2 cells revealed that p53 could down-regulate PTPA promoter activity in a dose-dependent manner, whereas four different p53 mutants could not. The p53-responsive region mapped to the minimal promoter. Overexpression of YY1 reverses the repressive effect of p53, suggesting a functional antagonism between p53 and YY1. The latter does not involve competition for YY1 binding, but rather direct control of YY1 function. Inhibition of PTPA expression by endogenous p53 was demonstrated in UVB-irradiated HepG2 cells, both on the mRNA and protein level. Also basal PTPA levels are higher in p53-negative (Saos-2) versus p53-positive (HepG2, U2OS) cells, suggesting "latent" p53 can control PTPA expression as well. The higher PTPA levels in U2OS cells, programmed to overexpress constitutively a dominant-negative p53 mutant, corroborate this finding. Thus, PTPA expression is negatively regulated by p53 in normal conditions and in conditions where p53 is up-regulated, via an as yet unknown mechanism involving the negative control of YY1.
authors.affiliation: Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: V
authors.initials: V
authors.lastname: Janssens
authors.forename: C
authors.initials: C
authors.lastname: Van Hoof
authors.forename: I
authors.initials: I
authors.lastname: De Baere
authors.forename: W
authors.initials: W
authors.lastname: Merlevede
authors.forename: J
authors.initials: J
authors.lastname: Goris
mesh_terms: D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism; D050981:Erythroid-Specific DNA-Binding Factors; D005786:Gene Expression Regulation / Q000528:radiation effects; D017930:Genes, Reporter; D006801:Humans; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D054648:Protein Phosphatase 2; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism / Q000528:radiation effects; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays; D050986:YY1 Transcription Factor
chemical_list: D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D011506:Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D050986:YY1 Transcription Factor; C494698:YY1 protein, human; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; C087440:PTPA protein, human