Deregulation of Cellular IkB Kinases by HTLV1 Tax

描述（由申请人提供）：感染人类t细胞白血病病毒1型（HTLV1）可导致不适当的生长信号转导，失去细胞周期控制，并发展为侵袭性恶性肿瘤，表现为成人t细胞白血病（ATL）。转化表型的获得取决于HTLV1 Tax癌蛋白与转录因子NF-kB的相互作用，后者通常有助于启动炎症和免疫的遗传程序。与促炎介质如肿瘤坏死因子- α (TNF)引起的NF-kB作用的短暂模式相反，NF-kB在表达Tax的细胞中具有组成性活性。Tax通过与IKK（一种tnf诱导的IkB激酶）形成稳定的复合物来劫持宿主信号通路。反过来，Tax将IKK转化为一种组成活性激酶，该激酶指定NF-kB的细胞质抑制剂用于蛋白水解破坏。这是一个继续项目的申请，以解剖病理机制的税收作用IKK。在本资助期内进行的研究表明，这种机制涉及税收诱导的IKK磷酸化和泛素化。这两种翻译后修饰是生物化学耦合的。此外，在表达YopJ（一种抑制NF-kB信号转导的Ub样蛋白蛋白酶）的细胞中，泛素（Ub）与IKK的税依赖偶联被破坏。研究的中心假设是IKK泛素化在正常和病理生理NF-kB信号的调节中起关键作用。为了验证中心假设，我们提出了实验来确定(i) IKK中的Ub受体位点在响应Tax癌蛋白和促炎激动剂时被修饰，（ii） IKK的生化机制和功能

DESCRIPTION (provided by applicant): Infection with human T-cell leukemia virus type 1 (HTLV1) can lead to inappropriate growth-signal transduction, the loss of cell cycle control, and the development of an aggressive malignancy manifested as adult T-cell leukemia (ATL). Acquisition of the transformed phenotype is contingent upon the interplay of the HTLV1 Tax oncoprotein with transcription factor NF-kB, which normally helps initiate the genetic programs for inflammation and immunity. In contrast to the transient pattern of NF-kB action elicited by proinflammatory mediators such as tumor necrosis factor-alpha (TNF), NF-kB is constitutively active in cells expressing Tax. Tax hijacks this host signaling pathway by forming stable complexes with IKK, a TNF-inducible IkB kinase. In turn, Tax converts IKK into a constitutively active kinase that earmarks cytoplasmic inhibitors of NF-kB for proteolytic destruction. This is an application for continuation of a project to dissect the pathologic mechanism of Tax action on IKK. Studies conducted during the present funding period indicate that this mechanism involves Tax-induced phosphorylation and ubiquitination of IKK. These two post-translational modifications are biochemically coupled. Moreover, Tax-dependent conjugation of ubiquitin (Ub) to IKK is disrupted in cells expressing YopJ, a Ub-like protein protease that inhibits NF-kB signal transduction. The central hypothesis under investigation is that IKK ubiquitination plays a critical role in the regulation of both normal and pathophysiologic NF-kB signaling. To test the central hypothesis, experiments are proposed to determine (i) the Ub acceptor sites in IKK that are modified in response to the Tax oncoprotein and proinflammatory agonists, (ii) the biochemical mechanism and function of IKK ubiquitination in NF-kB signal transduction, and (iii) the in vivo role of IKK ubiquitination in Tax-associated disease and immunobiology. Results from these studies may facilitate the identification of new molecular targets involved in IKK ubiquitination for therapeutic intervention in cancer, inflammation, and autoimmunity. The workscope of this application is responsive to Program Announcement PA-03-145, entitled "Ubiquitin and ubiquitin-like modifications regulating disease processes".