HTLV-1 TAX1 AS AN EXTRACELLULAR CYTOKINE

人类嗜T淋巴细胞病毒I型（HTLV-I）与两种 成人T细胞白血病（ATL）和热带痉挛性 轻瘫/HTLV-I相关脊髓病（TSP/HAM）。 HTLV-I Tax 1是 从受感染的淋巴细胞中释放出来， 细胞因子，刺激基因表达和增殖， 未感染的淋巴细胞 人甲状旁腺激素相关蛋白 在HTLV-I感染和未感染的细胞中分析了PTHrP基因 作为细胞内或细胞外Tax 1的靶细胞基因。 的 PTHrP基因表达的分析是重要的，因为体液 恶性肿瘤的高钙血症（HHM）与PTHrP的合成密切相关 和分泌物。 几种类型的人类癌症，包括ATL， 常伴有高钙血症。 PTHrP与 甲状旁腺激素（PTH）与PTH/PTHrP相互作用的能力 受体，从而诱导骨吸收，并增加 肾脏中的钙重吸收，最终导致 血液中的钙含量增加。 PTHrP启动子被刺激 细胞外细胞因子和生长因子。 转录 因子Ets 1是PTHrP的Tax 1反式激活的主要靶点 启动子 为了确定Tax 1的合作机制 用Ets 1，测试Gal 4/Tax 1融合蛋白的能力， 反式激活PTHrP启动子，所述PTHrP启动子在所述启动子中含有Gal 4结合位点， Ets 1结合位点的邻近。 Gal 4/Tax 1能够反式激活 PTHrP/Gal 4启动子在Ets 1不存在的情况下。 而且 Ets 1的加入没有进一步增加启动子的活性 在Tax 1的存在下。相反，Gal 4/Tax 1需要Ets 1 野生型PTHrP启动子的反式激活。 这表明，tax 1 可能与Ets 1结合，将自身锚在DNA上，从而能够与 基础机械的因素。与此假设一致，Ets 1 在体外观察到与Tax 1的物理相互作用，如凝胶电泳所示。 转移试验和酵母双杂交系统所示的体内试验。的 调节Tax 1/Ets 1相互作用的Ets 1和Tax 1的结构域正在被 分析了

Human T-cell lymphotropic virus type I (HTLV-I) is associatred with two human diseases, adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-I associated myelopathy (TSP/HAM). HTLV-I Tax1 is released from infected lymphocytes and functions as an extracellular cytokine to stimulate gene expression in, and proliferation of, uninfected lymphocytes. The human parathyroid hormone related protein (PTHrP) gene has been analyzed in HTLV-I infected and uninfected cells as a target cellular gene for intracellular or extracellular Tax1. The analysis of PTHrP gene expression is important since humoral hypercalcemia of malignancy (HHM) is closely linked to PTHrP synthesis and secretion. Several types of human cancers, including ATL, are frequently associated with hypercalcemia. PTHrP shares with the parathyroid hormone (PTH) the ability to interact with the PTH/PTHrP receptor and, consequently, to induce bone absorption and increased calcium reabsorption in the kidney, which eventually results in an increased calcium level in the blood. The PTHrP promoter is stimulated by several extracellular cytokines and growth factors. The transcription factor Ets1 is the primary target for Tax1 transactivation of the PTHrP promoter. In order to determine the mechanism by which Tax1 cooperates with Ets1, a Gal4/Tax1 fusion protein was tested for its ability to transactivate the PTHrP promoter containing a Gal4 binding site in the proximity of the Ets1 binding site. Gal4/Tax1 was able to transactivate the PTHrP/Gal4 promoter in the absence of Ets1. Furthermore, the addition of Ets1 did not further increase the activity of the promoter in the presence of Tax1. In contrast, Ets1 was required for Gal4/Tax1 transactivation of the wild type PTHrP promoter. This suggests that Tax1 may bind to Ets1 to anchor itself to the DNA to be able to interact with factors of the basal machinery. In agreement with this hypothesis, Ets1 was observed to physically interact with Tax1 in vitro as shown by gel shift assays and in vivo as shown by the two-hybrid system in yeast. The domain of Ets1 and Tax1 that mediate the Tax1/Ets1 interaction are being analyzed.