Proinflammatory cytokine gene transcription must be moderated to avoid the pathological consequences of excess cytokine production. The relationships between virus infection and the mechanisms that moderate cytokine transcription are incompletely understood. We investigated the influence of Keap1 on cytokine gene induction by Sendai virus infection in mouse embryo fibroblasts. Virus infection induced Keap1 binding to the Ifnb1, Tnf, and Il6 genes. Keap1 moderated viral induction of their transcription by mechanisms that did not require Nrf2. Keap1 was required for NF-κB p50 recruitment, but not for NF-κB p65 or IRF3 recruitment, to these genes. Keap1 formed complexes with NF-κB p50 and NF-κB p65, which were visualized using bimolecular fluorescence complementation analysis. These bimolecular fluorescence complementation complexes bound chromosomes in live cells, suggesting that Keap1 could bind chromatin in association with NF-κB proteins. Keap1 was required for viral induction of G9a-GLP lysine methyltransferase binding and H3K9me2 modification at cytokine genes. G9a-GLP inhibitors counteracted transcription repression by Keap1 and enhanced Keap1 and NF-κB recruitment to cytokine genes. The interrelationships among Keap1, NF-κB, and G9a-GLP recruitment, activities, and transcriptional effects suggest that they form a feedback circuit, which moderates viral induction of cytokine transcription. Nrf2 counteracted Keap1 binding to cytokine genes and the recruitment of NF-κB p50 and G9a-GLP by Keap1. Whereas Keap1 has been reported to influence cytokine expression indirectly through its functions in the cytoplasm, these findings provide evidence that Keap1 regulates cytokine transcription directly in the nucleus. Keap1 binds to cytokines genes upon virus infection and moderates their induction by recruiting NF-κB p50 and G9a-GLP.

必须调节促炎细胞因子基因转录以避免过量细胞因子产生的病理后果。病毒感染与调节细胞因子转录的机制之间的关系尚不完全清楚。我们研究了 Keap1 对仙台病毒感染小鼠胚胎成纤维细胞的细胞因子基因诱导的影响。病毒感染诱导 Keap1 与Ifnb1、Tnf和Il6 结合基因。Keap1 通过不需要 Nrf2 的机制调节病毒对其转录的诱导。Keap1 是这些基因募集 NF-κB p50 所必需的，但不是 NF-κB p65 或 IRF3 募集所必需的。Keap1 与 NF-κB p50 和 NF-κB p65 形成复合物，使用双分子荧光互补分析将其可视化。这些双分子荧光互补复合物结合活细胞中的染色体，表明 Keap1 可以结合染色质与 NF-κB 蛋白结合。Keap1 是病毒诱导 G9a-GLP 赖氨酸甲基转移酶结合和细胞因子基因 H3K9me2 修饰所必需的。G9a-GLP 抑制剂抵消了 Keap1 的转录抑制并增强了 Keap1 和 NF-κB 对细胞因子基因的募集。Keap1、NF-κB 和 G9a-GLP 募集、活动、和转录效应表明它们形成了一个反馈回路，可以调节病毒对细胞因子转录的诱导。Nrf2 抵消了 Keap1 与细胞因子基因的结合以及 Keap1 对 NF-κB p50 和 G9a-GLP 的募集。尽管据报道 Keap1 通过其在细胞质中的功能间接影响细胞因子的表达，但这些发现提供了 Keap1 直接在细胞核中调节细胞因子转录的证据。Keap1 在病毒感染后与细胞因子基因结合，并通过募集 NF-κB p50 和 G9a-GLP 来调节它们的诱导。尽管据报道 Keap1 通过其在细胞质中的功能间接影响细胞因子的表达，但这些发现提供了 Keap1 直接在细胞核中调节细胞因子转录的证据。Keap1 在病毒感染后与细胞因子基因结合，并通过募集 NF-κB p50 和 G9a-GLP 来调节它们的诱导。尽管据报道 Keap1 通过其在细胞质中的功能间接影响细胞因子的表达，但这些发现提供了 Keap1 直接在细胞核中调节细胞因子转录的证据。Keap1 在病毒感染后与细胞因子基因结合，并通过募集 NF-κB p50 和 G9a-GLP 来调节它们的诱导。