PROJECT SUMMARY Type I interferons (IFN-I) provide the first line of defense against viruses and play a pivotal role in coordinating the innate and adaptive immune responses. The presence of infectious viruses triggers a cascade of events leading to the activation of IFN-I genes that further induce the expression of a large battery of antiviral proteins. This antiviral program is something that must be selectively induced only when appropriate as chronic signaling is associated with severe inflammatory phenotypes and autoimmunity. These so called ‘interferonopathies’ are a clinically heterogenic group of diseases that are becoming increasingly recognized and speak to the importance of silencing the IFN-I locus in the absence of infection. Here we propose to define how a conserved gene called Kelch-Like Family Member 9 (KLHL9), which is found in the center of the IFN-I gene cluster, ensures the transcriptional repression of the region in the absence of virus infection. This proposed research will advance the understanding of how the IFN system functions at the center of immune and inflammatory diseases, and should also lead to a better understanding as to the molecular cause of at least a subset of interferonopathies.