An Sp1 binding site involves the transcription of the Fas ligand gene induced by PMA and ionomycin in Jurkat cells

The transcriptional regulation of the Fas ligand (FasL) gene in Jurkat cell s was investigated. We demonstrated that an Sp1 binding site, located betwe en -280 and -275 bp relative to the translational start site (+1) of the Fa st gene, was important for the transcription of the Fast gene by deletion a nd mutation analysis in Jurkat cells after phorbol 12-myristate 13-acetate (PMA) and ionomycin treatment. Nuclear extract of Jurkat cells formed compl exes with the oligonucleotides bearing the Spl site within -280 to -275 of the Fast promoter. Apart from the constitutive complexes, a new complex was observed after PMA and ionomycin stimulation. Plasmid containing the Sp1 s ite sequence with site-directed mutation reduced the Fast promoter activity in driving the expression of reporter luciferase gene expression in transf ected Jurkat cells after PMA and ionomycin stimulation. The binding of acti vated Jurkat cell nuclear extract to the mutated Spl binding site of the Fa st promoter was ablated. In addition, the oligomer containing the Spl site of the Fast promoter could compete with oligomer with conserved Spl binding sequence in nuclear protein binding of activated Jurkat cells. The data pr esented in this study suggest that the transactivation of the Fast promoter via the Spl binding sequence (-280 to -275) involves the PMA- and ionomyci n-induced expression of the Fast gene. Copyright (C) 2000 National Science Council, ROC and S. Karger AG, Basel.