Mitochondrial-localized activities of HHV-8 vIRF-1

描述(由申请人提供)：人类疱疹病毒8型(HHV-8)指定四种病毒干扰素调节因子同系物(vIRFs 1-4)，除了促进细胞周期停滞和细胞凋亡以应对病毒感染的细胞防御途径的其他组件外，它们还具有抑制细胞IRFs的功能。VIRF-1靶向抑制的细胞蛋白包括P53、ATM、GRIM19、Smad转录因子和IRF介导的反应所需的p300/CBP转录共激活因子。我们已经确定了一类全新的相互作用，即vIRF-1与应激反应、仅促凋亡的BH3蛋白(BOPS)Bim和Bid之间的相互作用。VIRF-1与Bim和Bid的相互作用是通过病毒蛋白的170-187残基(BOP结合域，BBD)和BOP的功能BH3结构域实现的。BIM和BID都是在HHV-8生产性复制过程中诱导的，每一个都被vIRF-1结合在功能上抑制，我们已经确定vIRF-1部分定位于线粒体，与 BOP在作用部位的直接靶向和失活的假设在生物学上是重要的。对于Bim，一个被证明是HHV-8复制的强大负调控者，我们还证明了vIRF-1结合导致核转位，代表了第二种失活模式。VIRF-1的这些特性代表了病毒控制宿主对感染的反应的新范例。这一应用着重于检测：(1)vIRF-1线粒体定位及其相关活性的结构要求；(2)vIRF-1靶向BOP/BH3的分子基础；(3)单个vIRF-1：BOP相互作用的功能意义以及vIRF-1线粒体在HHV-8生物学中的定位。该项目将表征vIRF-1的独特性质和活性，从而扩大对病毒逃避宿主细胞防御的理解，并可能使未来开发新型抗病毒药物成为可能。 公共卫生相关性：人类疱疹病毒8型(HHV-8)编码一种干扰素调节因子同系物vIRF-1，它有助于病毒抵抗先天性宿主细胞对病毒感染的防御。我们发现了vIRF-1功能的一种新机制，即直接与细胞前死亡蛋白(BH3-Only Proteins，BOPS)结合并抑制，这些蛋白被认为是病毒复制的关键负调控因子。这项研究的目的是阐明BOP识别和vIRF-1失活的分子决定因素和机制，从而表征这种以前未知的病毒操纵宿主细胞对感染的反应的方式。

DESCRIPTION (provided by applicant): Human herpesvirus 8 (HHV-8) specifies four viral interferon regulatory factor homologues (vIRFs 1-4) that function to inhibit cellular IRFs in addition to other components of cellular defense pathways that promote cell cycle arrest and apoptosis in response to virus infection. Cellular proteins targeted for inhibition by vIRF-1 include p53, ATM, GRIM19, Smad transcription factors, and p300/CBP transcriptional co-activators required for IRF-mediated responses. We have identified an entirely novel class of interaction, between vIRF-1 and stress-responsive, pro-apoptotic BH3-only proteins (BOPs) Bim and Bid. Interactions of vIRF-1 with Bim and Bid occur via residues 170-187 (BOP-binding domain, BBD) of the viral protein and the functional BH3 domains of the BOPs. Both Bim and Bid are induced during HHV-8 productive replication, each is inhibited functionally by vIRF-1 association, and we have identified partial localization of vIRF-1 to mitochondria, consistent with the hypothesis that direct targeting and inactivation of BOPs at their site of action is biologicaly important. For Bim, a demonstrated powerful negative regulator of HHV-8 replication, we have also shown that vIRF-1 binding leads to nuclear translocation, representing a secondary mode of inactivation. These properties of vIRF-1 represent new paradigms of viral control of host responses to infection. This application is focused on examining: (1) the structural requirements of vIRF-1 mitochondrial localization and associated activities; (2) the molecular basis of BOP/BH3 targeting by vIRF-1; (3) the functional significance of individual vIRF-1:BOP interactions and of vIRF-1 mitochondrial localization in HHV-8 biology. The project will characterize unique properties and activities of vIRF-1, thereby expand understanding of viral evasion from host cell defenses, and potentially enabling future development of novel antiviral agents. PUBLIC HEALTH RELEVANCE: Human herpesvirus 8 (HHV-8) encodes an interferon regulatory factor homologue, vIRF-1, that contributes to viral resistance to innate host cell defenses against viral infection. We have identified a novel mechanism of vIRF-1 function, namely the direct binding to and inhibition of cellular pro-death proteins (BH3- only proteins, BOPs), which are known to be critically important as negative regulators of virus replication. The goal of the proposed research is to elucidate the molecular determinants and mechanisms of BOP recognition and inactivation by vIRF-1, thereby characterizing this previously unknown means of virus manipulation of host cell responses to infection.