PARTICIPATION OF THE HUMAN P53 3'UTR IN TRANSLATIONAL REPRESSION AND ACTIVATION FOLLOWING GAMMA-IRRADIATION

p53 protein levels have been shown to increase in a number of cells af ter treatment with genotoxic agents through a post-transcriptional mec hanism. In gamma-irradiated human cells, the accumulation of p53 prote in is accompanied by an increase in the association of p53 mRNA with l arge polysomes without any change in the level of p53 mRNA, This redis tribution of p53 mRNA on polysomes in response to irradiation is consi stent with enhanced translational activity of p53 mRNA, We demonstrate that a region of the p53 3'-untranslated region (3'UTR) inhibits tran slation of a chimeric reporter mRNA in vivo. Induced elevation of repo rter activity after gamma-irradiation was seen in cells expressing chi meric reporter-p53 3'UTR transcripts, These data taken together demons trate translational control of p53 gene expression after gamma-irradia tion and denote a previously unsuspected and novel role for the p53 3' UTR in controlling translation.