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）指定了四种病毒干扰素调节因子同源物（vIRFs 1-4），其功能除了抑制细胞IRFs外，还抑制细胞防御途径的其他组分，这些组分促进细胞周期停滞和细胞凋亡以响应病毒感染。被vIRF-1抑制的靶向细胞蛋白包括IRF介导的应答所需的p53、ATM、GRIM 19、Smad转录因子和p300/CBP转录共激活因子。我们已经确定了一个全新的类之间的相互作用，vIRF-1和应激反应，促凋亡的BH 3-唯一的蛋白质（BOP）Bim和Bid。vIRF-1与Bim和Bid的相互作用通过病毒蛋白的残基170-187（BOP结合结构域，BBD）和BOP的功能性BH 3结构域发生。Bim和Bid在HHV-8生产性复制过程中均被诱导，每一种都在功能上被vIRF-1结合所抑制，我们已经确定了vIRF-1在线粒体的部分定位，这与 假设BOP在其作用位点的直接靶向和失活具有生物学重要性。对于Bim，一种已证实的HHV-8复制的强大负调节因子，我们还表明vIRF-1结合导致核转位，代表了二级失活模式。vIRF-1的这些特性代表了病毒控制宿主对感染反应的新范例。本申请的重点是检查：（1）vIRF-1线粒体定位和相关活性的结构要求;（2）vIRF-1靶向BOP/BH 3的分子基础;（3）单个vIRF-1：BOP相互作用和vIRF-1线粒体定位在HHV-8生物学中的功能意义。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剂成为可能。 公共卫生相关性：人类疱疹病毒8型（HHV-8）编码干扰素调节因子同源物vIRF-1，其有助于病毒抵抗先天宿主细胞对病毒感染的防御。我们已经确定了vIRF-1功能的一种新机制，即直接结合和抑制细胞促死亡蛋白（BH 3- only蛋白，BOP），已知其作为病毒复制的负调节因子至关重要。拟议研究的目标是阐明vIRF-1识别和灭活BOP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反应的手段。

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.