Proteomic identification of p53-dependent protein phosphorylation

The p53 tumor suppressor regulates transcription of target genes. We have previously analysed the p53-dependent proteome and identified novel protein targets. Here we have examined p53-dependent phosphorylation using two-dimensional gel electrophoresis and staining with the fluorescent phosphoprotein dye Pro-Q Diamond. We report that p53 induces phosphorylation of a subset of proteins including Nm23, DJ-1, ANXA1 and PrxII. Our identification of p53-dependent phosphorylation of specific target proteins reveals new aspects of the p53-dependent cellular response and suggests that such posttranslational modi. cations may contribute to p53-mediated tumor suppression.