STAT1 is a master regulator that orchestrates type 1 and 2 interferon (IFN)-induced IFN-stimulated gene (ISG) expression. The mechanisms by which STAT1 is phosphorylated and activated upon IFN signaling remain elusive. Our work demonstrated that ubiquitination of STAT1 mediated by the E3 ligase RNF220 contributed significantly to STAT1 activation and innate immune responses. Rnf220 gene deficiency resulted in the downregulation of IFN signaling and decreased expression of ISGs in response to type 1 and 2 IFNs stimulation and Acinetobacter baumannii and HSV-1 infection. Mechanistically, RNF220 interacted with STAT1 and mediated the K63-linked polyubiquitination of STAT1 at residue K110, which promoted the interaction between STAT1 and the kinase JAK1. The expression of RNF220 was induced by pathogenic infection and IFN signaling. RNF220 promoted STAT1 ubiquitination and phosphorylation through a positive feedback loop. RNF220 haploinsufficiency impaired IFN signaling, and RNF220-defective mice were more susceptible to A. baumannii and HSV-1 infection than WT mice. Our work offers novel insights into the mechanisms of STAT1 modulation and provides potential therapeutic targets against bacterial and viral infection and inflammatory diseases.

STAT1 是协调 1 型和 2 型干扰素 (IFN) 诱导的 IFN 刺激基因 (ISG) 表达的主要调节因子。STAT1 在 IFN 信号传导后被磷酸化和激活的机制仍然难以捉摸。我们的工作表明，由 E3 连接酶 RNF220 介导的 STAT1 泛素化对 STAT1 激活和先天免疫反应有显着贡献。Rnf220基因缺陷导致 1 型和 2 型 IFN 刺激和鲍曼不动杆菌引起的 IFN 信号下调和 ISG 表达降低和 HSV-1 感染。在机制上，RNF220 与 STAT1 相互作用并介导 STAT1 在残基 K110 处的 K63 连接的多泛素化，这促进了 STAT1 与激酶 JAK1 之间的相互作用。RNF220的表达是由病原体感染和IFN信号诱导的。RNF220 通过正反馈回路促进 STAT1 泛素化和磷酸化。RNF220 单倍体不足损害了 IFN 信号传导，RNF220 缺陷小鼠比 WT 小鼠更容易感染鲍曼不动杆菌和 HSV-1。我们的工作为 STAT1 调节机制提供了新的见解，并提供了针对细菌和病毒感染以及炎症性疾病的潜在治疗靶点。