Interaction of human T-cell lymphotropic virus type I Tax, Ets1, and Sp1 in transactivation of the PTHrP P2 promoter
Interaction of human T-cell lymphotropic virus type I Tax, Ets1, and Sp1 in transactivation of the PTHrP P2 promoter
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DOI：
10.1074/jbc.272.8.4953
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发表时间：
1997-02-21
影响因子：
4.8
通讯作者：
Brady, JN
中科院分区：
文献类型：
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作者：
Dittmer, J;PiseMasison, CA;Brady, JN
我们先前已经证明甲状旁腺激素相关蛋白(PTHrP)启动子包含转录因子Ets1和SPL的结合位点，并且人类T细胞嗜淋巴病毒I型(HTLV I)Tax与Ets1合作反式激活PTHrP P2启动子。利用酵母双杂交相互作用系统，我们现在提供了Tax与Ets1相互作用的证据。此外，Tax蛋白的双突变(D22A，C23S)取消了Tax/Ets1的相互作用，也抑制了Tax/Ets1的协同作用，表明Tax和Ets1之间的相互作用对PTHrP启动子的反式激活是重要的。在免疫共沉淀实验中，我们发现Tax促进了Ets1和SPL之间的相互作用，形成了一个三元复合体。当PTHrP启动子中的SPL位点发生突变时，Tax/Ets1的协同作用显著降低。这表明SPL在依赖Ets1的PTHrP P2启动子的Tax反式激活中起重要作用。最后，我们证明Gal4-Tax是Gal PTHrP启动子的强大激活剂，这意味着Tax直接参与了启动子的转录激活。我们提出了一个模型，其中Tax/Ets1对PTHrP P2启动子的协同作用是基于Tax、Ets1和Sp1在模板DNA上形成三元复合体的能力，Tax促进Ets1/Sp1的相互作用并直接参与转录启动过程。
We have previously shown that the parathyroid hormone-related protein (PTHrP) promoter contains binding sites for transcription factors Ets1 and Spl and that human T-cell lymphotropic virus type I (HTLV I) Tax cooperates with Ets1 to transactivate the PTHrP P2 promoter. Using the yeast two-hybrid interaction system, we now provide evidence that Tax interacts with Ets1. Moreover, a double mutation (D22A,C23S) in the Tax protein that abrogated the Tax/Ets1 interaction also inhibited the Tax/Ets1 cooperative effect, suggesting that the interaction between Tax and Ets1 is important for transactivation of the PTHrP promoter. In coimmunoprecipitation assays, we find that Tax facilitates the interaction between Ets1 and Spl, forming a ternary complex. When the Spl site in the PTHrP promoter was mutated, the Tax/Ets1 cooperative effect was dramatically decreased. This suggests that Spl plays an important role in the Ets1-dependent Tax transactivation of the PTHrP P2 promoter, Finally, we demonstrate that Gal4-Tax is a strong activator of the Gal PTHrP promoter, implying that Tax contributes directly to the transcriptional activation of the promoter. We propose a model in which the Tax/Ets1 cooperative effect on the PTHrP P2 promoter is based on the ability of Tax, Ets1, and Sp1 to form a ternary complex on the template DNA, Tax facilitates the interaction of Ets1/Sp1 and participates directly in the transcription initiation process.