Viral infection triggers the activation of transcription factor IRF3, and its activity is precisely regulated for robust antiviral immune response and effective pathogen clearance. However, how full activation of IRF3 is achieved has not been well defined. Herein, we identified BLK as a key kinase that positively modulates IRF3-dependent signaling cascades and executes a pre-eminent antiviral effect. BLK deficiency attenuates RNA or DNA virus-induced ISRE activation, interferon production and the cellular antiviral response in human and murine cells, whereas overexpression of BLK has the opposite effects. BLK-deficient mice exhibit lower serum cytokine levels and higher lethality after VSV infection. Moreover, BLK deficiency impairs the secretion of downstream antiviral cytokines and promotes Senecavirus A (SVA) proliferation, thereby supporting SVA-induced oncolysis in an in vivo xenograft tumor model. Mechanistically, viral infection triggers BLK autophosphorylation at tyrosine 309. Subsequently, activated BLK directly binds and phosphorylates IRF3 at tyrosine 107, which further promotes TBK1-induced IRF3 S386 and S396 phosphorylation, facilitating sufficient IRF3 activation and downstream antiviral response. Collectively, our findings suggest that targeting BLK enhances viral clearance via specifically regulating IRF3 phosphorylation by a previously undefined mechanism.

中文翻译：

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BLK 对 IRF3 的酪氨酸磷酸化促进其充分激活和先天抗病毒反应。

病毒感染会触发转录因子 IRF3 的激活，其活性受到精确调节，以实现强大的抗病毒免疫反应和有效的病原体清除。然而，如何实现 IRF3 的完全激活尚未明确。在此，我们确定 BLK 是一种关键激酶，可正向调节 IRF3 依赖性信号级联并执行卓越的抗病毒作用。BLK 缺乏会减弱 RNA 或 DNA 病毒诱导的 ISRE 激活、干扰素产生以及人和小鼠细胞中的细胞抗病毒反应，而 BLK 过度表达则具有相反的作用。BLK 缺陷小鼠在 VSV 感染后表现出较低的血清细胞因子水平和较高的致死率。此外，BLK 缺陷会损害下游抗病毒细胞因子的分泌并促进塞内卡病毒 A (SVA) 增殖，从而支持体内异种移植肿瘤模型中 SVA 诱导的溶瘤作用。从机制上讲，病毒感染触发 BLK 在酪氨酸 309 处自磷酸化。随后，激活的 BLK 直接结合并磷酸化 IRF3 在酪氨酸 107 处，这进一步促进 TBK1 诱导的 IRF3 S386 和 S396 磷酸化，促进充分的 IRF3 激活和下游抗病毒反应。总的来说，我们的研究结果表明，靶向 BLK 通过以前未定义的机制特异性调节 IRF3 磷酸化来增强病毒清除。