RNAi Screen and Proteomics Reveal NXF1 as a Novel Regulator of IRF5 Signaling

Interferon regulatory factor 5 (IRF5) is a key transcription factor of innate immunity, which plays an important role in host restriction to viral infection and inflammation. Genome-wide association studies have implied the association of IRF5 with several autoimmune diseases, including systemic lupus erythematosus (SLE), Sjogren’s syndrome, inflammatory bowel disease and multiple sclerosis. However, the regulation of IRF5-mediated immunity is not well understood. To uncover new regulators in IRF5 pathway, we used two “omics” approaches: affinity purification coupled with mass spectrometry and a high throughput RNAi screen. Proteomics identified 16 new IRF5 interactors while RNAi-mediated knockdown found 43 regulators of the TLR7-dependent IRF5 signaling pathway. NXF1 was identified in both screens. Stimulation with TLR7 ligand enhances formation of IRF5-NXF1 protein complexes. Gain or loss-of-function experiments revealed NXF1 selectively regulates TLR7-driven IRF5 transcriptional activity, suggesting a new role for NXF1 in the IRF5 signaling pathway.