The rapid activation of pattern recognition receptor (PRR)-mediated type I interferon (IFN) signaling is crucial for the host response to infection. In turn, human cytomegalovirus (HCMV) must evade this potent response to establish life-long infection. Here, we reveal that the HCMV tegument protein UL35 antagonizes the activation of type I IFN transcription downstream of the DNA and RNA sensors cGAS and RIG-I, respectively. We show that ectopic expression of UL35 diminishes the type I IFN response, while infection with a recombinant HCMV lacking UL35 induces an elevated type I IFN response compared to wildtype HCMV. With a series of luciferase reporter assays and the analysis of signaling kinetics upon HCMV infection, we observed that UL35 downmodulates PRR signaling at the level of the key signaling factor TANK-binding kinase 1 (TBK1). Finally, we demonstrate that UL35 and TBK1 co-immunoprecipitate when co-expressed in HEK293T cells. In addition, we show that a previously reported cellular binding partner of UL35, O-GlcNAc transferase (OGT), post-translationally GlcNAcylates UL35, but that this modification is not required for the antagonizing effect of UL35 on PRR signaling. In summary, we have identified UL35 as the first HCMV protein to antagonize the type I IFN response at the level of TBK1, thereby enriching our understanding of how this important herpesvirus escapes host immune responses.

中文翻译：

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巨细胞病毒外皮蛋白UL35拮抗模式识别受体介导的I型IFN转录。

模式识别受体（PRR）介导的I型干扰素（IFN）信号传导的快速激活对于宿主对感染的反应至关重要。反过来，人类巨细胞病毒（HCMV）必须规避这种有效的反应才能建立终生感染。在这里，我们揭示了HCMV外壳蛋白UL35分别拮抗DNA和RNA传感器cGAS和RIG-I下游I型IFN转录的激活。我们显示，UL35的异位表达减少了I型IFN反应，而与缺少UL35的重组HCMV感染相比，野生型HCMV引起了I型IFN反应的升高。通过一系列荧光素酶报告基因测定和HCMV感染后信号动力学的分析，我们观察到UL35在关键信号因子TANK结合激酶1（TBK1）的水平上下调了PRR信号。最后，我们证明当在HEK293T细胞中共同表达时，UL35和TBK1共同免疫沉淀。另外，我们显示了先前报道的UL35的细胞结合伴侣，O-GlcNAc转移酶（OGT），翻译后的GlcNAcylates UL35，但对于UL35对PRR信号的拮抗作用，不需要此修饰。总之，我们已将UL35确定为第一个在TBK1水平拮抗I型IFN反应的HCMV蛋白，从而丰富了我们对这种重要疱疹病毒如何逃脱宿主免疫反应的理解。但是对于UL35对PRR信号的拮抗作用，不需要进行此修饰。总之，我们已将UL35确定为第一个在TBK1水平拮抗I型IFN反应的HCMV蛋白，从而丰富了我们对这种重要疱疹病毒如何逃脱宿主免疫反应的理解。但是对于UL35对PRR信号的拮抗作用，不需要进行此修饰。总之，我们已将UL35确定为第一个在TBK1水平拮抗I型IFN反应的HCMV蛋白，从而丰富了我们对这种重要疱疹病毒如何逃脱宿主免疫反应的理解。