Impact of the interferon regulated proteins XAF1 and ZNF313 on innate immunity

描述（由申请人提供）：为了控制病毒感染，宿主已经形成了包括先天性和适应性免疫应答的综合防御网络。对病毒感染的初始反应主要涉及先天反应和用细胞毒性杀死感染细胞。一旦病毒侵入细胞，宿主介导的反应由单链和双链病毒RNA触发，其诱导包括干扰素（IFN）的应激细胞因子的表达。IFN通过诱导许多细胞内基因，即IFN刺激基因（ISG），对启动和协调成功的抗病毒应答至关重要，这些基因可防止病毒复制/细胞溶解并刺激免疫系统的适应性臂。防止病毒复制、传播或持续感染的细胞机制包括蛋白质合成的全面抑制、蛋白质转运的阻断和细胞凋亡的诱导。许多细胞蛋白质被认为是病毒诱导的细胞凋亡的介质，包括我们最初提出的两种蛋白质，TRAIL/Apo-2L和X连锁的凋亡相关因子-1（XAF 1）抑制剂。IFN还通过上调病毒检测系统的组分（包括toll样受体、RIG-I和下游信号传导分子）来有效地调节细胞对病毒和其他细胞病原体的应答。最近，我们已经表明，XAF 1增强细胞对凋亡剂如TRAIL的敏感性，也可以增强细胞的抗病毒反应。本文显示XAF 1影响由TNF家族配体和dsRNA信号传导级联引发的信号传导级联。该基金旨在从功能上剖析XAF 1活性的机制。重点将放在XAF 1活性的下游调节因子上，包括一种新鉴定的蛋白质ZNF 313，我们现在证明它是一种XAF 1结合的RING指蛋白，由IFN后调节。这种推定的E3泛素连接酶在调节IFN、病毒和其他先天性免疫应答中的作用将如以下目标中所概述的那样进行。我们还将追踪最近的数据，将XAF 1与其他调节泛素连接的信号分子（包括TRAF 2和RIP 2）联系起来，并证明TRIP 6（另一种XAF 1结合伴侣）可能代表TNF/dsRNA途径中的一种新型泛素化调节剂。

DESCRIPTION (provided by applicant): To control viral infections the host has developed an integrated defense network that comprises both innate and adaptive immune responses. Initial responses to viral infection involve primarily the innate response and the killing of infected cells with cytotoxicity. Once the virus has invaded the cell, host-mediated responses are triggered by single stranded and doubled stranded viral RNAs that induce expression of stress cytokines including interferons (IFNs). IFNs are essential for initiating and coordinating a successful antiviral response by inducing a number of intracellular genes, the IFN-stimulated genes (ISGs), which prevent virus replication/cytolysis and stimulate the adaptive arm of the immune system. Cellular mechanisms that prevent viral replication, dissemination or persistent infections include global inhibition of protein synthesis, blockage of protein transport and induction of apoptosis. A number of cellular proteins have been implicated as mediators of virus-induced apoptosis, including two of the proteins that were the focus of our original proposal, TRAIL/Apo-2L and X-linked inhibitor of apoptosis-associated factor-1 (XAF1). IFNs also potently regulate cellular responsiveness to virus and other cellular pathogens by upregulating components of the virus detection system, including toll-like receptors, RIG-I and downstream signaling molecules. Recently, we have shown that XAF1 augments cellular sensitivity to apoptotic agents such as TRAIL, and can also enhance cellular antiviral responses. XAF1 is shown herein to impact signaling cascades initiated by TNF family ligands and dsRNA signaling cascades. This grant is designed to functionally dissect the mechanism of XAF1 activity. Emphasis will be on downstream regulators of XAF1 activity, including a newly identified protein, ZNF313, which we now show to be a XAF1-binding RING finger protein that is post-translationally regulated by IFNs. The role of this putative E3 ubiquitin ligase in regulating IFN, viral and other innate immune responses will be pursued as outlined in the following aims. We will also pursue recent data linking XAF1 to other signaling molecules that regulate ubiquitin ligation, including TRAF2 and RIP2, and demonstrate that TRIP6, another XAF1 binding partner, may represent a novel ubiquitination regulator in the TNF/dsRNA pathway.