Human and Mouse Fas (APO-1/CD95) Death Receptor Genes Each Contain a p53-responsive Element That Is Activated by p53 Mutants Unable to Induce Apoptosis

Abstract

p53 is a tumor suppressor protein that induces apoptosis at least in part through its ability to act as a sequence-specific transactivator. This work reports that intron 1 of the mouse Fas death receptor gene contains a p53-responsive element (p53RE) that matches the p53 consensus sequence and that is located between nucleotides +1704 and +1723 from the transcription initiation site. This element is specifically bound by p53 and functions as a p53-dependent enhancer in mammalian or in yeast reporter gene assays. Contrary to bax, another known pro-apoptotic p53-target gene, both mouse and human FAS p53REs are still activated by the discriminatory p53 mutants Pro-175 and Ala-143, a class of mutants unable to induce apoptosis. We propose that p53-dependent up-regulation of Fas does not induce apoptosis per se but sensitizes the cell to other pro-apoptotic signal(s). The functional conservation of p53-dependent Fas up-regulation argues strongly in favor of its biological importance and suggests that murine models may be used to study further the in vivo role of Fas in the p53 response.