DEREGULATION OF NF-KB/REL BY TAX & ADULT T-CELL LEUKEMIA

通过税收放松 NF-KB/REL 的管制

• 批准号: 2712745
• 负责人: Shao-Cong Sun
• 金额: $ 18万
• 依托单位: PENNSYLVANIA STATE UNIV HERSHEY MED CTR
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-08-01 至 2000-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2712745
• 关键词: biological signal transduction; gene mutation; genetic promoter element; genetic regulation; genetic regulatory element; human T cell leukemia; human T cell lymphotropic virus type 1; human genetic material tag; inhibitor /antagonist; molecular cloning; nuclear factor kappa beta; phosphorylation; protein kinase; proteins; protooncogene; site directed mutagenesis; virus protein

Adult T-cell leukemia (ATL) is a very aggressive and often fatal T-cell malignancy that is caused by infection of the type I human T-cell leukemia virus (HTLV-I). The HTLV-I encoded Tax protein appears to play a central role in the initiation of this virally induced T-cell malignancy. Tax acts by activating cellular transcription factors, including members of the NF- 1kappaBalpha/Rel family, which in turn induces various cellular genes involved in lymphocyte activation and growth. In resting T cells, NF- kappaB/Rel factors are sequestered m the cytoplasm by various inhibitory proteins including I-kappaB-alpha, a 37 kD protein containing multiple ankyrin-like repeats. HTLV-I Tax expression results in the constitutive nuclear expression of these kappaB-enhancer binding proteins, leading to the deregulated expression the various cellular growth-related genes, which have been proposed to induce the polyclonal T-cell proliferation, a prelude to the establishment of ATL. Our recent studies suggest that Tax activation of NF-kappaB is associated with the phosphorylation and degradation of I-kappaB-alpha and the activated nuclear NF-kappaB seems, together with other yet to be identified transcriptional enhancers or silencers, to mediate the Tax-induced transcriptional induction of the c- rel proto-oncogene. We have further observed that these Tax-induced cellular events can be blocked by various inhibitors of cellular signal transduction. Together, these results raise the possibility that Tax may induce a specific cellular signal transduction pathway leading to a cascade of both cytoplasmic and nuclear reactions with phosphorylation of IkBa serving as a molecular trigger. This specific action of Tax results in the nuclear expression of both NF-kB and c-Rel. Based on these results, the overall objective of this grant proposal is a fundamental understanding of the Tax-mediated NF-kappaB/Rel induction signaling pathway. To approach this overall objective, a set of biochemical studies will be undertaken to precisely map the sites of Tax-induced phosphorylation within I-kappaB-alpha. In turn, site-directed mutations will be sequentially introduced into these sites to examine the functional significance of these phosphorylation events on Tax-mediated I-kappaB- alpha degradation. In conjunction with these site-directed mutagenesis, progressive deletional analyses will also be performed to completely define the sequences within I-kappaB-alpha that are required for protease attack. To explore the Tax-mediated signaling pathway, different strategies will be used to identify and characterize the cellular molecular components, including I-kappaB-alpha-specific kinases and the more proximal signaling molecules, involved in the Tax-mediated activation of NF-kappaB/Rel. Finally, the precise mechanism of Tax-induced transcriptional induction of c-rel gene will be explored by isolation and functional analyses of the human c-rel gene promoter.

成人T细胞白血病（ATL）是一种非常具有侵袭性且通常致命的T细胞白血病。 由I型人类T细胞白血病感染引起的恶性肿瘤 病毒（HTLV-I）。HTLV-I编码的Tax蛋白似乎起着中心作用， 在这种病毒诱导的T细胞恶性肿瘤的起始中起作用。税收法案 通过激活细胞转录因子，包括NF-κ B的成员， 1 kappaB α/Rel家族，其反过来诱导各种细胞基因 参与淋巴细胞的活化和生长。在静息T细胞中，NF- kappaB/Rel因子通过各种抑制性的细胞因子被隔离在细胞质中。 蛋白质，包括I-kappaB-α，一种37 kD的蛋白质，含有多个 类似脚踝的重复。HTLV-I Tax表达导致组成性 这些κ B增强子结合蛋白的核表达，导致 各种细胞生长相关基因的表达失调， 已经提出诱导多克隆T细胞增殖， 这是建立ATL的前奏。我们最近的研究表明， NF-κ B的活化与磷酸化有关， I-κ B-α和活化的核NF-κ B的降解似乎， 与其他尚未鉴定的转录增强子一起， 沉默子，以介导Tax诱导的c- rel原癌基因我们进一步观察到，这些税收诱导的 细胞事件可被细胞信号的各种抑制剂阻断 转导总之，这些结果提高了税收可能 诱导特异性细胞信号转导途径， 细胞质和细胞核反应的级联反应， IkBa作为分子触发器。这一具体行动的税收结果 NF-κ B和c-Rel的核表达。基于这些结果， 这项赠款提案总体目标是 Tax介导的NF-κ B/Rel诱导信号的理解 通路为了达到这一总体目标，一系列生物化学研究 将进行精确地绘制税收诱导的网站， I-κ B-α内的磷酸化。反过来，定点突变 将依次引入这些网站，以检查功能 这些磷酸化事件对Tax介导的I-kappaB- α降解结合这些定点诱变， 还将进行渐进式删除分析， 定义蛋白酶所需的I-kappaB-α内的序列 攻击为了探索Tax介导的信号通路， 策略将用于识别和表征细胞 分子组分，包括I-κ B-α特异性激酶和 更近端的信号分子，参与Tax介导的激活 NF-κ B/Rel.最后，税收诱导的确切机制 将通过分离来探索c-rel基因的转录诱导， 人c-rel基因启动子的功能分析。