Lindholm P F, Reid R L, Brady J N
Laboratory of Molecular Virology, National Cancer Institute, Bethesda, Maryland 20892.
J Virol. 1992 Mar;66(3):1294-302. doi: 10.1128/JVI.66.3.1294-1302.1992.
The human T-cell leukemia virus type I tax1 gene product is responsible for the increased expression of several cytokine and cellular genes that contain NF-kappa B regulatory sequences. Our laboratory has previously demonstrated that purified, extracellular Tax1 protein induced the nuclear accumulation of NF-kappa B binding activity in lymphoid cells. Since HTLV-I infection causes increased levels of lymphotoxin tumor necrosis factor-beta [TNF-beta] and immunoglobulin secretion, we have studied the interaction of NF-kappa B proteins from Tax1-stimulated cells with the TNF-beta and immunoglobulin kappa (Ig kappa) light chain genes. Tax1 induction of NF-kappa B occurred in the presence of cycloheximide, and Tax1 stimulation did not result in increased levels of NF-kappa B or c-rel RNA. These results indicate that new synthesis of NF-kappa B proteins was not required for induction of NF-kappa B-binding activity. With use of the Ig kappa NF-kappa B-binding site as a probe, two distinct NF-kappa B gel shift complexes were induced by the Tax1 protein. A slower-migrating complex, C1, was inhibited by the addition of purified I kappa B. In contrast, the faster-migrating C2 complex was not inhibited by I kappa B, but C2 was increased by detergent treatment of cytoplasmic extracts, suggesting that its binding activity was also regulated by an inhibitor. The Tax1-stimulated proteins that interacted with the NF-kappa B-binding sites in the Ig kappa and TNF-beta promoters were distinct. A 75-kDa protein preferentially associated with the Ig kappa NF-kappa B-binding site. In contrast, a 59-kDa protein associated with the TNF-beta NF-kappa B-binding site. Tax1 stimulation led to increased levels of TNF-beta and Ig kappa mRNA, as measured by reverse transcription and polymerase chain reaction analysis. These results represent the first experimental evidence that extracellular Tax1 can regulate the expression of endogenous cellular genes.
人类I型T细胞白血病病毒tax1基因产物可使几种含有核因子κB（NF-κB）调控序列的细胞因子和细胞基因的表达增加。我们实验室先前已证明，纯化的细胞外Tax1蛋白可诱导淋巴样细胞中NF-κB结合活性的核内积累。由于人嗜T淋巴细胞病毒I型（HTLV-I）感染会导致淋巴毒素肿瘤坏死因子-β（TNF-β）水平升高和免疫球蛋白分泌增加，因此我们研究了Tax1刺激细胞中的NF-κB蛋白与TNF-β和免疫球蛋白κ（Igκ）轻链基因之间的相互作用。在存在放线菌酮的情况下，Tax1可诱导NF-κB的产生，并且Tax1刺激不会导致NF-κB或c-rel RNA水平升高。这些结果表明，诱导NF-κB结合活性并不需要NF-κB蛋白的重新合成。以IgκNF-κB结合位点为探针，Tax1蛋白可诱导出两种不同的NF-κB凝胶迁移复合物。迁移较慢的复合物C1可被添加的纯化IκB抑制。相比之下，迁移较快的C2复合物不受IκB抑制，但用去污剂处理细胞质提取物可使C2增加，这表明其结合活性也受一种抑制剂调控。与Igκ和TNF-β启动子中的NF-κB结合位点相互作用的Tax1刺激蛋白是不同的。一种75 kDa的蛋白优先与IgκNF-κB结合位点相关。相比之下，一种59 kDa的蛋白与TNF-βNF-κB结合位点相关。通过逆转录和聚合酶链反应分析测定，Tax1刺激导致TNF-β和IgκmRNA水平升高。这些结果代表了首个实验证据，表明细胞外Tax1可调节内源性细胞基因的表达。
