Mouzaki A, Serfling E, Zubler R H
Department of Medicine, Hôpital Cantonal Universitaire, Genève, Switzerland.
Eur J Immunol. 1995 Aug;25(8):2177-82. doi: 10.1002/eji.1830250809.
The regulation of interleukin (IL)-2 gene expression has been investigated mainly in T lymphocytes, the predominant producers of IL-2. However, B cells can also synthesize IL-2. In the present study we analyzed the control of IL-2 promoter activity in Epstein-Barr virus (EBV)-transformed B cell clones which are capable of secreting IL-2 at a low level after stimulation with phorbol 12-myristate 13-acetate and the Ca2+ ionophore ionomycin. Transient transfections using reporter constructs with multiples of transcription factor binding sites from the IL-2 promoter [distal nuclear factor (NF)-AT, proximal NF-AT, AP-1/Octamer (UPS) or NF-chi B (TCEd) sites] were performed. In EBV-transformed B clones, the chi B site exerted the strongest inducible activity; the NF-AT binding sites showed either no or only weak activity compared to Jurkat T cells. An IL-2 promoter bearing a defective NF-chi B site was completely inactive in EBV-transformed B cells, while it still had activity in Jurkat T cells. In seven EBV-B cell clones or lines differing in their capacity to secrete IL-2, the activity of the IL-2 promoter correlated well with the status of IL-2 secretion. Similarly, a human immunodeficiency virus promoter, whose activity is controlled through chi B factors, was found to be active in the IL-2 producing EBV-B cells, but inactive in the non-IL-2-producing cells. Electrophoretic mobility shift assays using protein extracts from EBV-B cells and the IL-2 NF-chi B probe revealed the constitutive generation of chi B complexes in IL-2-secreting cells consisting mainly of heterodimeric p50/p65 complexes. A weaker chi B complex formation and faster-migrating complexes were detected in non-IL-2-secreting cells. These results demonstrate that the IL-2 NF-chi B site is indispensable for the activity of the IL-2 promoter in EBV-transformed B cells, whereas other transcription factors appear to be less important for IL-2 expression in these cells.
白细胞介素（IL）-2基因表达的调控主要在T淋巴细胞中进行研究，T淋巴细胞是IL-2的主要产生者。然而，B细胞也能合成IL-2。在本研究中，我们分析了在爱泼斯坦-巴尔病毒（EBV）转化的B细胞克隆中IL-2启动子活性的调控情况，这些克隆在用佛波醇12-肉豆蔻酸酯13-乙酸酯和Ca2+离子载体离子霉素刺激后能够低水平分泌IL-2。使用含有来自IL-2启动子的多个转录因子结合位点（远端核因子（NF）-AT、近端NF-AT、AP-1/八聚体（UPS）或NF-κB（TCEd）位点）的报告基因构建体进行瞬时转染。在EBV转化的B克隆中，κB位点发挥最强的诱导活性；与Jurkat T细胞相比，NF-AT结合位点要么没有活性，要么只有微弱活性。带有缺陷NF-κB位点的IL-2启动子在EBV转化的B细胞中完全无活性，而在Jurkat T细胞中仍有活性。在七个分泌IL-2能力不同的EBV-B细胞克隆或细胞系中，IL-2启动子的活性与IL-2分泌状态密切相关。同样，一种其活性通过κB因子控制的人类免疫缺陷病毒启动子，在产生IL-2的EBV-B细胞中具有活性，但在不产生IL-2的细胞中无活性。使用来自EBV-B细胞的蛋白质提取物和IL-2 NF-κB探针进行的电泳迁移率变动分析显示，在分泌IL-2的细胞中组成型产生κB复合物，主要由异二聚体p50/p65复合物组成。在不分泌IL-2的细胞中检测到较弱的κB复合物形成和迁移较快的复合物。这些结果表明，IL-2 NF-κB位点对于EBV转化的B细胞中IL-2启动子的活性是不可或缺的，而其他转录因子在这些细胞中对IL-2表达似乎不太重要。
