Modulation intrinsischer Immunität durch adenovirale Onkoproteine

腺病毒(Ad)癌蛋白E1B-55K和E4orf6是Ad复制的多功能调节者，参与了最大限度的病毒生产和Ad介导的肿瘤发生所需的许多过程。它们的生长促进活动与它们与细胞生长的一些关键调控因子相互作用和操纵的能力有关。突出的例子是肿瘤抑制因子(如P53)、DNA修复蛋白、泛素和相扑结合机制的组件，以及其他细胞限制因子，它们可能赋予对Ad感染的固有免疫力。本课题组最近的工作表明，这些因子是PML核体(PML-NBS)的不同组成部分，其抗病毒活性可能通过翻译后机制(如SUMO化)来调控。在拟议的项目中，我们计划进一步研究这些宿主因子，并在分子水平上揭示PML-NBS在抗病毒和细胞生长控制中的作用。工作将集中在PML-NB相关肿瘤抑制蛋白PML及其六种异构体的遗传和生化分析，以及裂解感染和转化细胞中病毒相互作用伙伴(E1B-55K和E4orf6)的研究。在这些研究的背景下，我们还将解决这个问题，即E1B-55K是否通过固有的E3相扑连接酶活性拮抗PML-NBS的抗病毒特性。最后，通过对特定亚型重组细胞系的分析，将阐明特定的PML亚型作为固有的抗病毒和/或抗癌基因屏障的介体的功能(S)。总之，本项目旨在了解致病性人类病毒侵占宿主细胞机制以获得高效的后代生产和细胞转化的分子机制。这些研究将揭示病毒复制和致病机制以及病毒介导的细胞转化的新策略，从而为抗病毒和抗癌治疗药物的设计提供一个平台。似乎对E1B-55K和E4orf6的分析特别适合作为模型系统，因为它们的裂解和致癌特性是病毒复制和病毒诱导的细胞转化的基本原理。

The adenovirus (Ad) oncoproteins E1B-55K and E4orf6 are multifunctional regulators of Ad replication participating in many processes required for maximal virus production and Ad-mediated oncogenesis. Their growth-promoting activities correlate with their ability to interact with and to manipulate a number of key regulators of cell growth. Prominent examples are tumor suppressors (e.g. p53), DNA repair proteins, components of the ubiquitin- and SUMO-conjugation machineries, and other cellular restriction factors, which may confer an intrinsic immunity against Ad infections. Recent work from our group indicates that these factors are different components of PML nuclear bodies (PML-NBs), whose antiviral activity is manipulated likely through posttranslational mechanisms (e.g. SUMOylation).In the proposed project we plan to further investigate these host factors and to uncover the role of PML-NBs in the antiviral and cellular growth control at the molecular level. Work will be focused on genetic and biochemical analyses of the PML-NB-associated tumor suppressor protein PML and its six isoforms as well on studies of the viral interaction partners (E1B-55K and E4orf6) in lytically infected and transformed cells. In the context of these studies we will also address the question, whether E1B-55K antagonizes the antiviral properties of the PML-NBs through an intrinsic E3 SUMO ligase activity. Finally the function(s) of the specific PML isoforms as mediators of an intrinsic antiviral and/or anti-oncogenic barrier will be clarified through the analyses of isoform-specific reconstituted cell lines.Overall, this project aims for an understanding of the molecular mechanism by which pathogenic human viruses usurp the host cell machinery for efficient progeny production and cell transformation. These studies should reveal novel strategies of viral replication and pathogenesis, as well as virus-mediated cell transformation, and thus provide a platform for the design of anti-viral as well as anti-cancer therapeutics. It appears that the analysis of the Ad oncoproteins E1B-55K and E4orf6 is particularly suitable as a model system because their lytic and oncogenic properties underlie fundamental principles of viral replication and virus-induced cell transformation.