Ye Jung Sook, Kim Nari, Lee Kyoung Jin, Nam Young Ran, Lee Uk, Joo Chul Hyun
Department of Microbiology, Cell Dysfunction Research Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
Department of Microbiology, Cell Dysfunction Research Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
J Virol. 2014 Nov;88(21):12765-76. doi: 10.1128/JVI.02037-14. Epub 2014 Aug 20.
Beta interferon (IFN-β) is involved in a wide range of cellular functions, and its secretion must be tightly controlled to inhibit viral spreading while minimizing cellular damage. Intracellular viral replication triggers cellular signaling cascades leading to the activation of the transcription factors NF-κB and interferon regulatory factor 3 (IRF3) and IRF7 (IRF3/7), which synergistically bind to the IFN-β gene promoter to induce its expression. The mitochondrial antiviral signaling protein (MAVS) is a governing adaptor protein that mediates signaling communications between virus-sensing proteins and transcription factors. The activity of MAVS in the regulation of IFN-β secretion is affected by many cellular factors. However, the mechanism of MAVS-mediated IRF3/7 activation is not completely understood. Here, we identified a highly conserved DLAIS motif at amino acid positions 438 to 442 of MAVS that is indispensable for IRF3/7 activation. Specifically, the L439S and A440R mutations suppress IRF3/7 activation. Pulldown experiments using wild-type and mutant MAVS showed that mindbomb E3 ubiquitin protein ligase 2 (MIB2) binds to the DLAIS motif. Furthermore, the DLAIS motif was found to be critical for MIB2 binding, the ligation of K63-linked ubiquitin to TANK-binding kinase 1, and phosphorylation-mediated IRF3/7 activation. Our results suggest that MIB2 plays a putative role in MAVS-mediated interferon signaling.
Mitochondrial antiviral signaling protein (MAVS) mediates signaling from virus-sensing proteins to transcription factors for the induction of beta interferon. However, the mechanism underlying activation of MAVS-mediated interferon regulatory factors 3 and 7 (IRF3/7) is not completely understood. We found a highly conserved DLAIS motif in MAVS that is indispensable for IRF3/7 activation through TANK-binding kinase 1 (TBK1) and identified it as the binding site for mindbomb E3 ubiquitin protein ligase 2 (MIB2). The mutations that targeted the DLAIS motif abolished MIB2 binding, attenuated the K63-linked ubiquitination of TBK1, and decreased the phosphorylation-mediated activation of IRF3/7.
β干扰素（IFN-β）参与多种细胞功能，其分泌必须受到严格控制，以抑制病毒传播，同时将细胞损伤降至最低。细胞内病毒复制触发细胞信号级联反应，导致转录因子核因子κB（NF-κB）以及干扰素调节因子3（IRF3）和IRF7（IRF3/7）激活，它们协同结合到IFN-β基因启动子以诱导其表达。线粒体抗病毒信号蛋白（MAVS）是一种关键衔接蛋白，介导病毒感应蛋白与转录因子之间的信号通讯。MAVS在调节IFN-β分泌中的活性受多种细胞因子影响。然而，MAVS介导的IRF3/7激活机制尚未完全阐明。在此，我们在MAVS的第438至442位氨基酸处鉴定出一个高度保守的DLAIS基序，它对于IRF3/7激活不可或缺。具体而言，L439S和A440R突变抑制IRF3/7激活。使用野生型和突变型MAVS进行的下拉实验表明，Mindbomb E3泛素蛋白连接酶2（MIB2）与DLAIS基序结合。此外，发现DLAIS基序对于MIB2结合、K63连接的泛素连接到TANK结合激酶1以及磷酸化介导的IRF3/7激活至关重要。我们的结果表明，MIB2在MAVS介导的干扰素信号传导中发挥推定作用。
线粒体抗病毒信号蛋白（MAVS）介导从病毒感应蛋白到转录因子的信号传导，以诱导β干扰素。然而，MAVS介导的干扰素调节因子3和7（IRF3/7）激活的潜在机制尚未完全阐明。我们在MAVS中发现一个高度保守的DLAIS基序，它通过TANK结合激酶1（TBK1）对IRF3/7激活不可或缺，并将其鉴定为Mindbomb E3泛素蛋白连接酶2（MIB2）的结合位点。靶向DLAIS基序的突变消除了MIB2结合，减弱了TBK1的K63连接泛素化，并降低了磷酸化介导的IRF3/7激活。
