Exploring How HTLV-1 Tax Induces T Cell Leukemia

描述（由申请人提供）：I型人T细胞白血病病毒（HTLV-I）是一种复杂的C型逆转录病毒，在病因学上与几种不同的人类疾病相关，包括：（1）成人T细胞白血病（ATL），一种活化的CD 4 + T淋巴细胞的侵袭性且通常致命的肿瘤性扩增;（2）热带痉挛性轻瘫/HTLV-I相关的脊髓病（TSP/HAM），一种涉及脊髓的进行性神经变性过程;和（3）影响包括眼睛、唾液腺、关节和肌肉在内的不同终末器官的各种知之甚少的自身免疫性或炎性疾病。HTLV-I转化人CD 4 + T淋巴细胞的分子基础尚不清楚，然而，pX编码的Tax基因产物似乎起着核心作用。Tax通过改变包括NF-κ B/Rel和CREB/ATF在内的选定宿主转录因子的活性，增强病毒复制并解除各种宿主细胞基因的表达。为了确定与完全T细胞转化相关的分子事件，我们将利用Tax表达转基因小鼠，其发展与ATL非常相似的T细胞淋巴瘤。将评价表达选择性损害NF-κ B/Rel或CREB/ATF依赖性基因表达的Tax突变体的转基因动物，以确定这些单个转录因子途径中的每一个在T细胞转化中所起的作用。我们将通过制备和研究条件性表达Tax或IkappaB α的不可降解突变体的转基因动物，进一步评估Tax或NF-κ B/Rel表达对Tax诱导的肿瘤维持的需求，所述突变体可有效抑制Tax激活NF-κ B/Rel（特定目标1）。在第二条研究线中，我们将探索税收如何激活NF-κ B/Rel家族的转录因子，在其与信号体复合物的IKK γ亚基的物理组装之后。将评估上游激酶通过Tax向信号体的潜在募集以及Tax寡聚化的潜在作用。在相关研究中，我们将测试Tax对p53肿瘤抑制因子的失活是否涉及IKK复合物的磷酸化。（具体目标2）。在第三线的实验中，我们将研究税收如何诱导持续的，长期的核表达NF-κ B，这与生理刺激引起的短暂反应截然不同。我们将专门研究税收是否颠覆了IKK复合体内的负信号的产生，通常终止signalsome行动。此外，我们将探讨Tax与一个新认识的核NF-κ B负调控途径的潜在相互作用，该途径涉及组蛋白去乙酰化酶3对RelA的去乙酰化作用。这种脱乙酰化促进RelA的快速核输出，并有助于终止NF-κ B反应（特异性目的3）。通过这些结合在体内和体外实验，我们希望获得关键的洞察HTLV-I Tax介导的白血病发生的分子事件。

DESCRIPTION (provided by applicant): The type I human T cell leukemia virus (HTLV-I) is a complex type C retrovirus etiologically linked with several diverse human diseases including: (1) the Adult T Cell Leukemia (ATL), an aggressive and usually fatal neoplastic expansion of activated CD4+ T lymphocytes; (2) Tropical Spastic Paraparesis/HTLV-I associated myelopathy (TSP/HAM), a progressive neurodegenerative process involving the spinal cord; and (3) a variety of poorly understood autoimmune or inflammatory diseases that affect different end organs including the eye, salivary glands, joints, and muscle. The molecular basis for HTLV-I transformation of human CD4+ T lymphocytes remains unclear, however, the pX-encoded Tax gene product appears to play a central role. Tax both enhances viral replication and deregulates the expression of various host cell genes by altering the activity of select host transcription factors including NF-kappaB/Rel and CREB/ATF. To define the molecular events associated with full T cell transformation, we will utilize Tax expressing transgenic mice that develop T-cell lymphomas closely resembling ATL. Transgenic animals expressing mutants of Tax that are selectively impaired for NF-kappaB/Rel or CREB/ATF dependent gene expression will be evaluated to define the role played by each of these individual transcription factor pathways in T cell transformation. We will further assess the requirement for continuous Tax or NF-kappaB/Rel expression for maintenance of Tax induced tumors by preparing and studying transgenic animals conditionally expressing Tax or a nondegradable mutant of IkappaBalpha that potently inhibits NF-kappaB/Rel activation by Tax (Specific Aim 1). In a second line of study, we will explore how Tax activates the NF-kappaB/Rel family of transcription factors, following its physical assembly with the IKKgamma subunit of the signalsome complex. The potential recruitment of upstream kinases to the signalsome by Tax and the potential role of Tax oligomerization will be assessed. In related studies, we will test whether the inactivation of the p53 tumor suppressor by Tax involves phosphorylation by the IKK complex. (Specific Aim 2). In a third line of experimentation, we will investigate how Tax induces the sustained, long-term nuclear expression of NF-kappaB, which differs sharply from transient response elicited by physiological stimuli. We will specifically examine whether Tax subverts the generation of negative signals within the IKK complex that normally terminates signalsome action. Additionally, we will explore the potential interplay of Tax with a newly recognized negative pathway of nuclear NF-kappaB regulation involving deacetylation of RelA by histone deacetylase 3. Such deacetylation promotes the rapid nuclear export of RelA and contributes to termination of the NF-kappaB response (Specific Aim 3). Through these combined in vivo and in vitro experiments, we hope to gain key insights into the molecular events underlying HTLV-I Tax mediated leukemogenesis.