Key Points OTUD1 restricts IRF3 activity in a nonproteolytic manner. OTUD1 deubiquitinates and inhibits DNA binding capacity of IRF3. Virus-induced K6-linked ubiquitination of IRF3 is indispensable for its DNA binding capacity. Visual Abstract IFN regulatory factor 3 (IRF3) is critical for the transcription of type I IFNs in defensing virus and promoting inflammatory responses. Although several kinds of posttranslational modifications have been identified to modulate the activity of IRF3, whether atypical ubiquitination participates in the function regulation, especially the DNA binding capacity of IRF3, is unknown. In this study, we found that the ovarian tumor domain containing deubiquitinase OTUD1 deubiquitinated IRF3 and attenuated its function. An atypical ubiquitination, K6-linked ubiquitination, was essential for the DNA binding capacity of IRF3 and subsequent induction of target genes. Mechanistically, OTUD1 cleaves the viral infection–induced K6-linked ubiquitination of IRF3, resulting in the disassociation of IRF3 from the promoter region of target genes, without affecting the protein stability, dimerization, and nuclear translocation of IRF3 after a viral infection. Otud1−/− cells as well as Otud1−/− mice produced more type I IFNs and proinflammatory cytokines after viral infection. Otud1−/− mice were more resistant to lethal HSV-1 and VSV infection. Consistent with the former investigations that IRF3 promoted inflammatory responses in LPS-induced sepsis, Otud1−/− mice were more susceptible to LPS stimulation. Taken together, our findings revealed that the DNA binding capacity of IRF3 in the innate immune signaling pathway was modulated by atypical K6-linked ubiquitination and deubiquitination process, which was regulated by the deubiquitinase OTUD1.

中文翻译：

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OTUD1 通过破坏 IRF3 的非经典泛素化负向调节 I 型干扰素的诱导

要点 OTUD1 以非蛋白水解方式限制 IRF3 活性。OTUD1 去泛素化并抑制 IRF3 的 DNA 结合能力。病毒诱导的 K6 连接的 IRF3 泛素化对其 DNA 结合能力是必不可少的。视觉摘要 干扰素调节因子 3 (IRF3) 在防御病毒和促进炎症反应中对 I 型干扰素的转录至关重要。虽然已经确定了几种翻译后修饰来调节 IRF3 的活性，但非典型泛素化是否参与功能调节，尤其是 IRF3 的 DNA 结合能力尚不清楚。在这项研究中，我们发现含有去泛素化酶 OTUD1 的卵巢肿瘤结构域使 IRF3 去泛素化并减弱其功能。非典型泛素化，K6 连接的泛素化，对 IRF3 的 DNA 结合能力和随后的靶基因诱导至关重要。从机制上讲，OTUD1 切割病毒感染诱导的 K6 连接的 IRF3 泛素化，导致 IRF3 从靶基因的启动子区域解离，而不影响病毒感染后 IRF3 的蛋白质稳定性、二聚化和核易位。Otud1-/- 细胞以及 Otud1-/- 小鼠在病毒感染后产生更多的 I 型干扰素和促炎细胞因子。Otud1-/- 小鼠对致命的 HSV-1 和 VSV 感染更具抵抗力。与之前 IRF3 促进 LPS 诱导的败血症中的炎症反应的研究一致，Otud1-/- 小鼠更容易受到 LPS 刺激。综合起来，