Characterization of the human p53 gene promoter.

Transcriptional deregulation of the p53 gene may play an important part in the genesis of some tumors. We report here an accurate determination of the transcriptional start sites of the human p53 gene and show that the majority of p53 mRNA molecules do not contain a postulated stem-loop structure at their 5' ends. Recombinant plasmids of the human p53 promoter-leader region fused to the bacterial chloramphenicol acetyltransferase gene (cat) were constructed. After transfection into rodent or human cells, a 350-base-pair fragment spanning the promoter region conferred 4% of the CAT activity mediated by the simian virus 40 early promoter/enhancer. We monitored the efficiency with which 15 3' and 5' promoter deletion constructs initiated transcription. Our results show that an 85-base-pair fragment, previously thought to have resided in exon 1, is all that is required for full promoter activity.