Transcriptional regulation of the human GD3 synthase gene expression in Fas-induced Jurkat T cells: a critical role of transcription factor NF-kB in regulated expression

Abstract

The transcriptional regulation mechanisms involved in the up-regulation of Fas-induced GD3 synthase gene have not yet been elucidated. 5￠-Rapid amplification of cDNA end (5￠-RACE) using mRNA prepared from Fas-induced Jurkat T cells revealed the presence of multiple transcription start sites of human GD3 synthase gene, and the 5￠-end analysis of the longest of its product showed that transcription started from 650 nucleotides upstream of the translational initiation site. Promoter analyses of the 5￠-flanking region of the human GD3 synthase gene using luciferase gene reporter system showed strong promoter activity in Fas-induced Jurkat T cells. Deletion study revealed that the region from ?1146 to ?646 (A of the translational start ATG as position +1) was indispensable for the Fas response. This region lacks apparent TATA and CAAT boxes but contains putative binding sites for transcription factors c-Ets-1, cAMP-responsive element-binding (CREB) protein, activating protein 1 (AP-1), and NF-kB. Base-substitution experiment showed that only the NF-kB-binding site of putative binding sites is required for the maximal expression induced by Fas. Both DNase I footprint and electrophoretic mobility shift assays with the nuclear extract of Fas-induced Jurkat T cells revealed that NF-kB was bound specifically to the probe being mediated by its binding site in the promoter sequence. Taken together, these results indicate that NF-kB plays an essential role in the transcriptional activity of human GD3 synthase gene in Fas-induced Jurkat T cells. In addition, the translocation of NF-kB-binding protein to nucleus by Fas activation is also crucial for the increased expression of the GD3 synthase gene in Fas-activated Jurkat T cells.