Pfeuffer I, Klein-Hessling S, Heinfling A, Chuvpilo S, Escher C, Brabletz T, Hentsch B, Schwarzenbach H, Matthias P, Serfling E
Institute of Pathology, University of Würzburg, Germany.
J Immunol. 1994 Dec 15;153(12):5572-85.
The promoters of IL-2 and IL-4 genes contain multiple binding sites for octamer factors. In peripheral T lymphocytes and several T cell lines, both the ubiquitous Oct factor Oct-1 and the lymphocyte-specific factor Oct-2 are expressed and bind to the IL-2 and IL-4 promoters. Prominent octamer binding sites of IL-2 and IL-4 promoters are their upstream promoter sites (UPS) which share 14 identical nucleotides. Multiple copies of the IL-2 and IL-4 UPS act as inducible enhancers in T cells, and their induction is inhibited by the immunosuppressant cyclosporin A (CsA). Closely linked to the octamer site, the IL-2 UPS contains a non-canonical AP-1 binding (TRE) site, and mutation in either site to a non-functional factor binding site impairs the induction of the IL-2 promoter. The binding of AP-1 and octamer factors to the IL-2 UPS DNA overlaps, and the tight association and functional cooperation of octamer with AP-1 factors is of crucial importance for the inducible IL-2 UPS activity. Introduction of five or ten spacer nucleotides between both IL-2 UPS sites results in a drastic reduction of inducible UPS activity, both in the loss of suppression by CsA and stimulation by the Ca(2+)-dependent phosphatase calcineurin. Within the IL-4 UPS the Oct and TRE-like motifs are separated by a binding site of nuclear factor of activated T cells (NF-AT). This site shares nine out of ten bp with an IL-2 NF-AT site. The strong binding of NF-ATp to the IL-4 UPS site suppresses the simultaneous binding of Oct factors to the IL-4 UPS. Because the two other Oct binding sites of IL-4 promoter show a similar sequence configuration, the binding of NF-AT seems to prevent the simultaneous binding of Oct factors to the IL-4 promoter. By contrast, both classes of factors bind simultaneously to the IL-2 promoter, and their tight association with AP-1 enhances the IL-2 promoter activity.
白细胞介素-2（IL-2）和白细胞介素-4（IL-4）基因的启动子含有多个八聚体因子结合位点。在外周血T淋巴细胞和几种T细胞系中，普遍存在的八聚体因子Oct-1和淋巴细胞特异性因子Oct-2均有表达，并与IL-2和IL-4启动子结合。IL-2和IL-4启动子显著的八聚体结合位点是它们的上游启动子位点（UPS），这些位点共有14个相同的核苷酸。IL-2和IL-4的UPS多拷贝在T细胞中充当诱导型增强子，其诱导作用受到免疫抑制剂环孢素A（CsA）的抑制。与八聚体位点紧密相连，IL-2的UPS含有一个非典型的激活蛋白-1（AP-1）结合（TRE）位点，任一该位点突变为无功能的因子结合位点都会损害IL-2启动子的诱导作用。AP-1和八聚体因子与IL-2的UPS DNA的结合相互重叠，八聚体与AP-1因子的紧密关联和功能协作对于诱导型IL-2的UPS活性至关重要。在IL-2的两个UPS位点之间引入5个或10个间隔核苷酸会导致诱导型UPS活性急剧降低，这在CsA抑制作用丧失以及钙调神经磷酸酶（一种依赖钙离子的磷酸酶）刺激作用丧失方面均有体现。在IL-4的UPS内，Oct基序和类TRE基序被活化T细胞核因子（NF-AT）的一个结合位点隔开。该位点与IL-2的NF-AT位点在10个碱基对中有9个相同。NF-ATp与IL-4的UPS位点的强结合会抑制Oct因子同时与IL-4的UPS结合。由于IL-4启动子的另外两个Oct结合位点显示出相似的序列结构，NF-AT的结合似乎会阻止Oct因子同时与IL-4启动子结合。相比之下，这两类因子会同时与IL-2启动子结合，并且它们与AP-1的紧密关联会增强IL-2启动子活性。
