Chinese Academy of Sciences Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, 100101 Beijing, People's Republic of China.
J Immunol. 2013 Sep 1;191(5):2614-23. doi: 10.4049/jimmunol.1203143. Epub 2013 Aug 5.
The intracellular RIG-I-like receptors recognize 5'-triphosphate viral genomic RNA and initiate the production of cytokines through mitochondria adaptor VISA. The regulation of this signal pathway is largely unknown. In this study, we report that the histone methyltransferase enhancer of zeste homolog 2 (EZH2) inhibits RIG-I signal pathway in an methyltransferase-independent manner. Knockdown EZH2 expression enhances VISA-induced activation of IFN-β promoter and NF-κB signaling. Cytosolic distributed EZH2 colocalizes with VISA and binds to its caspase recruitment domain (CARD), thus blocking its association with RIG-I. During the infection of influenza A virus (IAV) strain A/WSN/33 (WSN), EZH2 translocates to RIG-I and continuously interferes the interaction between RIG-I and VISA. Both N and C termini of EZH2 interact with VISA and attenuate its downstream signaling. WSN virus infection-induced expression of TNF-α, IFN-β, and IL-8 is inhibited by EZH2 and its catalytic dead form ΔSET. EZH2 overexpression facilitates the replications of IAV strains WSN and A/Puerto Rico/8/34 influenza virus. Knockdown EZH2 expression activates infection-induced IFN-β transcription and inhibits virus replication. We further provided evidence to show that pharmacological disruption of EZH2 expression by its inhibitor 3-deazaneplanocin A activates innate immune responses and attenuates the replication of WSN virus in HeLa, MDCK, and mouse primary bone marrow-derived macrophages, but not in IFN-deficient Vero cells. Collectively, these results revealed that EZH2 binds to VISA and interferes with the interaction between VISA and RIG-I. Targeting EZH2 activates mitochondria-mediated antiviral innate immune responses, and thus represses the replication of IAV in cells.
细胞内的 RIG-I 样受体识别 5'-三磷酸病毒基因组 RNA，并通过线粒体衔接蛋白 VISA 启动细胞因子的产生。这个信号通路的调节在很大程度上是未知的。在这项研究中，我们报告组蛋白甲基转移酶增强子的锌指蛋白 2（EZH2）以非甲基转移酶依赖的方式抑制 RIG-I 信号通路。EZH2 表达的敲低增强了 VISA 诱导的 IFN-β 启动子和 NF-κB 信号的激活。细胞质中分布的 EZH2 与 VISA 共定位，并与它的半胱氨酸天冬氨酸蛋白酶募集结构域（CARD）结合，从而阻止其与 RIG-I 结合。在流感病毒 A 株（IAV）A/WSN/33（WSN）感染过程中，EZH2 易位到 RIG-I 并持续干扰 RIG-I 和 VISA 之间的相互作用。EZH2 的 N 和 C 末端与 VISA 相互作用，并减弱其下游信号。EZH2 和其催化失活形式 ΔSET 抑制了 WSN 病毒感染诱导的 TNF-α、IFN-β 和 IL-8 的表达。EZH2 的过表达促进了 IAV 株 WSN 和 A/Puerto Rico/8/34 流感病毒的复制。敲低 EZH2 表达激活了感染诱导的 IFN-β 转录并抑制了病毒复制。我们进一步提供了证据表明，EZH2 表达的药理学抑制通过其抑制剂 3-去氮杂胞苷 A 激活先天免疫反应，并减弱 WSN 病毒在 HeLa、MDCK 和小鼠原代骨髓来源巨噬细胞中的复制，但在 IFN 缺陷的 Vero 细胞中没有。总之，这些结果表明 EZH2 与 VISA 结合并干扰 VISA 和 RIG-I 之间的相互作用。靶向 EZH2 激活了线粒体介导的抗病毒先天免疫反应，从而抑制了 IAV 在细胞中的复制。
