Transcriptional regulation of fas gene expression by GA-binding protein and AP-1 in T cell antigen receptor CD3 complex-stimulated T cells

Fas (CD95 or APO-1), a transmembrane cell surface receptor of the tumor nec rosis factor receptor family, is up-regulated in activated T lymphocytes. O ur present study identified an upstream enhancer element (between nucleotid e positions -862 and -682) containing a GA-binding protein (GABP) site and a low affinity activating protein-1 (AP-l)-binding site. T cell activation increased the DNA binding of GABP and AP-1 to this enhancer site. The speci ficity of GABP and AP-1 binding was demonstrated by competition electrophor etic mobility shift assay and supershift electrophoretic mobility shift ass ay with antibodies against GABP and AP-1, respectively. Mutational analysis of Fas promoter revealed that both GABP- and AP-l-binding sites were requi red for initiating Fas gene transcription. We further show that anti-CD3 mA b, phorbol 12-myristate 13-acetate, and phorbol l2-myristate 13-acetate/ion omycin strongly activated promoters carrying multiple copies of the Fas enh ancer, and mutation of either the GABP or AP-1 binding site severely reduce d transcriptional activity. Taken together, these results suggest that the transcription factors GABP and AP-1 play a critical role in the induction o f Fas gene expression in T cell antigen receptor CD3-stimulated Jurkat cell s.