A potential transcriptional activation element in the p53 protein.

The human p53 gene codes for a 393 amino acid nuclear phosphoprotein. p53 is most commonly described as a tumor suppressor, or anti-oncogene, although its role in vivo remains unclear. We report that GAL4-p53 fusion protein can activate transcription of a CAT reporter gene downstream of a GAL4-DNA binding site. We tested both the amino terminal 160 amino acids and the carboxyl terminal 233 amino acids of the p53 protein and found that the transcriptional activating (TA) region was restricted to the amino terminal fragment. These results imply that p53 may be a transcriptional activating factor (TAF); furthermore, these data lend support to the hypothesis of p53 as a positive regulator of transcription which might mediate its tumor suppressor role by inducing expression of a set of genes with a negative effect on cellular growth.