Restraint of IFN-γ expression through a distal silencer CNS–28 for tissue homeostasis

Abstract

Interferon-g (IFN-g) is a key cytokine in response to viral or intracellular bacterial infection in mammals. While a number of enhancers are described to promote IFN-g responses, no silencers for the Ifng gene have been identified. By examining H3K4me1 histone modification in naïve CD4 +T cells within Ifng locus, we identified an unrecognized silencer (CNS–28) that is responsible for restraining Ifng expression. Mechanistic study further demonstrates that CNS–28 maintains Ifng silence by diminishing enhancer-promoter interactions within Ifng locus in a T-bet independent manner. Functionally, CNS–28 restrains Ifng transcription in Th1, Tc1, and NK cells during both innate and adaptive immune responses. Moreover, CNS–28 deficiency resulted in repressed type 2 responses due to elevated IFN-g expression, shifting Th1 and Th2 paradigm. Thus, CNS–28 activity ensures immune cell quiescence by cooperating with other regulatory cis elements within the Ifng gene locus to minimize autoimmunity. This research was supported by the Intramural Research Programs of National Heart, Lung and Blood Institute, National Cancer Institute, and National Institute of Allergy and Infectious Diseases of National Institutes of Health.