A translation repressor element resides in the 3 ' untranslated region of human p53 mRNA

The 3' untranslated region of human p53 mRNA represses translation both irt vitro and in vivo. Here, we identify a cis-acting 66-nucleotide U-rich seq uence in the human p53 mRNA 3' untranslated region that mediates translatio nal repression. Using UV crosslinking, we detect a 40 kDa protein that inte racts specifically with the p53 3'UTR containing the repressor element. Enh anced translation of p53 mRNA contributes to the accumulation of p53 protei n in cells exposed to gamma-radiation and could be a consequence of relievi ng the inhibition mediated by the repressor element.