Li-Weber M, Laur O, Hekele A, Coy J, Walczak H, Krammer P H
Tumor Immunology Program, German Cancer Research Center, Heidelberg.
Eur J Immunol. 1998 Aug;28(8):2373-83. doi: 10.1002/(SICI)1521-4141(199808)28:08<2373::AID-IMMU2373>3.0.CO;2-T.
Expression of the CD95 (APO-1/Fas) ligand (CD95L) in activated T cells is a major cause of T cell activation-induced apoptosis. To study the molecular mechanisms of transcriptional control of CD95L expression in T cells, we investigated the human CD95L promoter in Jurkat T cells. Deletion studies revealed that the CD95L proximal promoter sequence from -220 to the transcription start site is essential for T cell stimulation-induced expression of CD95L. In this study, we discovered a novel regulatory element located at -120 of the CD95L promoter which contains DNA binding sites for SP-1 and a yet unknown inducible factor. Mutation analysis demonstrated that binding of the inducible factor to the -120 region is crucial for the biological function of the CD95L promoter upon T cell stimulation. The DNA sequence at -120 also contains two DNA motifs homologous to the binding site for NF-AT. NF-AT does not directly bind to this element. However, cotransfection studies with an NF-AT expression vector showed that NF-AT may confer a strong inducible activity to the CD95L promoter at this regulatory region. Our data also show that the immunosuppressive agent cyclosporin A down-regulates CD95L transcription by inhibiting the function of this positive regulatory element.
活化T细胞中CD95（APO-1/Fas）配体（CD95L）的表达是T细胞活化诱导凋亡的主要原因。为了研究T细胞中CD95L表达的转录调控分子机制，我们在Jurkat T细胞中研究了人CD95L启动子。缺失研究表明，从-220到转录起始位点的CD95L近端启动子序列对于T细胞刺激诱导的CD95L表达至关重要。在本研究中，我们在CD95L启动子的-120处发现了一个新的调控元件，其包含SP-1和一个未知诱导因子的DNA结合位点。突变分析表明，诱导因子与-120区域的结合对于T细胞刺激后CD95L启动子的生物学功能至关重要。-120处的DNA序列还包含两个与NF-AT结合位点同源的DNA基序。NF-AT不直接结合该元件。然而，与NF-AT表达载体的共转染研究表明，NF-AT可能在该调控区域赋予CD95L启动子强大的诱导活性。我们的数据还表明，免疫抑制剂环孢素A通过抑制该正调控元件的功能来下调CD95L转录。
