Switching of transcriptional control from interferon regulatory factor 2 to interferon regulatory factor 1 drives innate immune cell activation.

Interferon regulatory factor 2 (IRF2) is a transcription factor that prevents skin inflammation in mice and humans but, paradoxically, promotes pyroptosis by upregulating gasdermin D. How IRF2 activates some proinflammatory genes but suppresses inflammation is unclear. We show that skin inflammation in Irf2-deficient mice is driven by IRF1 activation of interferon-stimulated genes (ISGs). Chromatin profiling reveals that IRF1 and IRF2 occupy the same ISG regulatory sites, but as a weaker transcriptional activator, IRF2 limits ISG transcription by IRF1. Toll-like receptor (TLR) signaling favors IRF1-driven transcription by inducing Irf1. In addition, IRF1 recruits the ubiquitin ligase SPOP to ISG sites, resulting in proteasomal degradation of IRF2. This shift from IRF2 to IRF1 occupancy enhances ISG transcription. Collectively, these findings define a hierarchical transcriptional circuit in which IRF2 limits IRF1 activity under homeostatic conditions but is displaced during an immune response, allowing IRF1-dependent gene programs central to innate immunity and autoinflammation.