Expression of human p53 requires synergistic activation of transcription from the p53 promoter by AP-1, NF-κB and Myc/Max

Transcriptional control of p53 expression participates in the generation of appropriate le, els of active p53 in response to mitogenic stimulation, This prompted us to study the role of a putative AP-1 and a NF-kappa B motif in the human p53 promoter for transcriptional regulation, We show that mutation of the AP-1 or the NF-kappa B motif abolishes transcription from the human p53 promoter in HeLa, HepG2 and adenovirus type 5 E1-transformed 293 cells, In comparison, mutation of the previously characterized Myc/Max/USF binding site in the human p53 promoter reduces the transcription rate fivefold. The AP-1 motif in the human p53 promoter binds c-Fos and c-Jun and the NF-kappa-B motif binds p50(NF-kappa B1) and p65(RelA). The cooperative nature of transcriptional activation by these factors was documented by repression of c-fos or NF-kappa B1 translation: Pretreatment of the cells,vith a c-fos or p50(NF-kappa B1) antisense oligonucleotide suppresses transcription from the human p53 promoter completely. In addition, we show that (a) the level of endogenous p53 mRNA and (b) transcription from the strictly p53-dependent human mdm2 promoter are reduced in the presence of c-fos, c-jun, p50(NF-kappa B1), p65(RelA) or c-myc antisense oligonucleotides, underscoring the importance of these transcription factors for the expression of functional p53.