Characterization of interferon regulatory factor 3 stability and negative regulation in mammalian antiviral innate immunity 2751

Abstract Description The general paradigm of mammalian antiviral response involves the detection of viral pathogen-associated molecular patterns (PAMPs) by host Pattern Recognition Receptors (PRRs), which activate Interferon Regulatory Factors (especially IRF3 and IRF7). These IRFs trigger Interferon (IFN) transcription which induces a battery of antiviral genes, collectively called Interferon Stimulated Genes (ISGs). Type-I IFN expression, primarily driven by IRF3, is critical to mounting an antiviral response. However, tight regulation of the IFN-β response is essential within cells, as unchecked IFN-β expression can lead to immune pathologies. One mechanism of negative regulation of the IFN-β response is the degradation of IRF3. Our study aims to explore IRF3’s role in IFN induction and how its degradation modulates the IFN-β response to maintain immune homeostasis. We found that IRF3 undergoes proteasomal and autophagic degradation, partially dependent on IFN. Additionally, we investigated the role of ubiquitination on IRF3 stability and function, discovering that K33-linked ubiquitination stabilizes IRF3 but inhibits its transcriptional activity by preventing its nuclear translocation. Using a genome-wide CRISPR knockout screen and a proteomics screen, we identified cellular factors that regulate IRF3 stability in mammalian systems. Overall, this study reveals new fundamental knowledge about mammalian antiviral immunity and will facilitate the development of novel antiviral strategies. Funding Sources Supported by Prime Minister’s Research Fellowship (PMRF); INFOSYS Young Investigator Award for Research. Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)