Mitochondrial-localized activities of HHV-8 vIRF-1

描述（由申请人提供）：人疱疹病毒8 （HHV-8）指定四种病毒干扰素调节因子同源物（vIRFs 1-4），其功能是抑制细胞IRFs以及其他细胞防御途径的成分，这些途径促进细胞周期阻滞和细胞凋亡，以响应病毒感染。被vIRF-1抑制的细胞蛋白包括p53、ATM、GRIM19、Smad转录因子和irf介导应答所需的p300/CBP转录共激活因子。我们已经确定了一种全新的相互作用，在vIRF-1和应激反应，促凋亡的bh3蛋白（BOPs） Bim和Bid之间。vIRF-1与Bim和Bid的相互作用发生在病毒蛋白的残基170-187 （bop结合域，BBD）和BOPs的功能BH3结构域。Bim和Bid都是在HHV-8高产复制过程中被诱导的，它们都被vIRF-1关联在功能上抑制，我们已经确定了vIRF-1在线粒体的部分定位，与

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.