Numerical data used in Figs 1–6.

The detection of cytosolic viral nucleic acids via pattern-recognition receptors (PRRs) activates multiple signaling pathways, leading to the production of interferons (IFNs), which are essential for host survival during viral infection. Precise control of PRR gene expression is crucial for maintaining immune homeostasis. Here, we showed that Mediator complex subunit 23 (Med23) is required for the precise production of the innate immune receptor RIG-I in response to RNA virus infection. Med23 deficiency markedly enhances the production of IFN-I, proinflammatory cytokines, and IFN-stimulated genes (ISGs) in both multiple cell lines (MEFs, RAW264.7 cells, and HeLa cells) and mouse primary macrophages (bone marrow-derived macrophages [BMDMs] and peritoneal macrophages [PEMs]) infected with RNA virus VSV or stimulated with poly(I:C). Myeloid-specific Med23 knockout mice were generated to test the critical role of Med23 in host resistance to VSV infection in vivo. Mechanistically, Med23 interacts with the transcription factor forkhead box O3 (Foxo3) to negatively regulate RIG-I, thereby modulating IFN-I signaling. Collectively, these findings elucidate a previously unrecognized role of Med23 as a gatekeeper of the RIG-I-mediated antiviral innate immune response and suggest a potential target for controlling viral infection.

通过模式识别受体（pattern-recognition receptors, PRRs）检测胞浆病毒核酸，可激活多条信号通路，进而诱导干扰素（interferons, IFNs）的产生——这是宿主在病毒感染期间存活的必需条件。精准调控模式识别受体基因的表达，对维持免疫稳态至关重要。本研究证实，中介体复合物亚基23（Mediator complex subunit 23, Med23）是RNA病毒感染过程中，先天免疫受体RIG-I（Retinoic acid-inducible gene I）精准表达所必需的调控因子。在感染RNA病毒水疱性口炎病毒（vesicular stomatitis virus, VSV）或经聚肌胞苷酸（poly(I:C)）刺激的多种细胞系（小鼠胚胎成纤维细胞[mouse embryonic fibroblasts, MEFs]、RAW264.7细胞、海拉细胞[HeLa cells]）以及小鼠原代巨噬细胞（涵盖骨髓来源巨噬细胞[bone marrow-derived macrophages, BMDMs]与腹腔巨噬细胞[peritoneal macrophages, PEMs]）中，Med23缺失会显著提升I型干扰素（IFN-I）、促炎细胞因子与干扰素刺激基因（IFN-stimulated genes, ISGs）的产生水平。我们构建了髓系特异性Med23敲除小鼠，以在体内验证Med23在宿主抵抗VSV感染过程中的关键作用。机制研究表明，Med23可与转录因子叉头框O3（forkhead box O3, Foxo3）相互作用，负向调控RIG-I的表达，进而调节I型干扰素信号通路。综上，本研究阐明了Med23作为RIG-I介导的抗病毒先天免疫应答守门人的全新功能，同时为病毒性感染的防控提供了潜在干预靶点。