Mechanism of HTLV-1 activation of the SRF pathway.

描述(申请人提供)：人类T细胞淋巴营养病毒I型(HTLV-I)是两种疾病的病原体：HTLV-I相关性脊髓病/热带痉挛麻痹(HAM/TSP)和成人T细胞白血病(ATL)。病毒的3‘端编码一个353个氨基酸，40千道尔顿，被称为Tax的磷蛋白。TAX通过调节识别CREB、NF-kappaB和SRF启动子元件的转录因子的活性，以某种方式激活病毒和宿主基因的转录。在每种情况下，Tax不仅与转录因子-DNA复合体相互作用，还与相关因子相互作用。例如，TAX与CREB和辅活化子CBP相互作用，导致病毒基因表达。有强有力的证据表明，TAX在ATL患者的病毒肿瘤形成中起着关键作用。ATL是一种侵袭性很强且对化疗耐药的T细胞癌，最终导致患者在平均6个月内死亡。据估计，世界上有1000-2000万人感染HTLV-I，传播主要通过母乳，其次是输血、静脉注射药物和性接触。一旦患者被诊断出患有ATL，患者的存活概率就非常小，因为这种癌症还没有已知的治疗方法。实验室研究表明，Tax可诱导原代细胞永生化，并导致裸鼠体内软琼脂集落和肿瘤的形成。该提案的目的是确定SRF转录途径的税收激活机制(S)。已发表的数据表明，TAX-CREB相互作用对于病毒基因表达是重要的，并且TAX-NF-kappaB相互作用对于维持转化的表型是重要的。我们假设Tax-SRF相互作用是启动转化表型所必需的。为了了解TAX在SRF途径中的作用，我们将确定TAX激活血清反应元件(SRE)的机制。含有SRE的促进者的税收激活必须要求积极的监管机构是活跃的，消极监管机构是不活跃的，并且事件必须符合条件地发生。我们的方法是研究TAX对SRF功能的三个方面的影响：碱性转录复合体在启动子上的组装，MAPK途径(正调节因子)的活性，以及抑制因子ID(负调节因子)的活性。

DESCRIPTION (provided by applicant): Human T cell lymphotrophic virus type I (HTLV-I) is the etiologic agent of two diseases: HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T cell leukemia (ATL). The 3' end of the virus encodes a 353 amino acid, 40 kiloDalton, phosphoprotein known as Tax. Tax activates the transcription of viral and host genes somehow by modulating the activity of transcription factors which recognize the CREB, NF-kappaB, and SRF promoter elements. In each case, Tax not only interacts with the transcription factor-DNA complex but also with associated factors. For example, Tax interacts with both CREB and the coactivator CBP, resulting in viral gene expression. There is strong evidence that Tax plays a critical role in viral oncogenesis in ATL patients. ATL is rapidly aggressive and chemotherapy-resistant T cell cancer, ultimately resulting in the patient's death within an average of 6 months. An estimated 10-20 million people in the world are infected with HTLV-I, and transmission primarily occurs through human breast milk and to a lesser extent, blood transfusions, IV drug use, and sexual contact. Once the patient is diagnosed with ATL, the survival probability of the patient is extremely small since there is no known cure for the cancer. Laboratory studies have shown that Tax induces the immortalization of primary cells and causes the formation of soft agar colonies and tumors in nude mice. The goal of the proposal is to determine the mechanism(s) of Tax activation of the SRF transcription pathway. Published data indicates that the Tax-CREB interactions are important for viral gene expression and that the Tax-NF-kappaB interactions are important for maintenance of the transformed phenotype. We hypothesize that the Tax-SRF interactions are essential for initiation of the transformed phenotype. To understand the role of Tax in the SRF pathway, we will determine the mechanism of Tax activation of the serum response element (SRE). Tax activation of promoters containing an SRE must require that the positive regulators are active and negative regulators are inactive, and the events must occur constitutively. Our approach will be to examine the effects of Tax on three aspects of SRF function: assembly of the basic transcription complex on the promoter, activity of the MAPK pathway (positive regulator), and activity of the inhibitor Id (negative regulator).