Abstract
Cells must moderate transcription that is induced by virus infection to mitigate deleterious consequences of inflammation. We investigated the mechanisms whereby Keap1 moderates the transcription of genes that are induced by Sendai virus infection in mouse embryo fibroblasts (MEFs). Virus infection induced Keap1 to bind Ifnb1, Tnf and Il6, and reduced Keap1 binding at Cdkn1a and Ccng1. Keap1 was required for G9a and GLP to bind and to deposit H3K9me2 at these genes upon virus infection. Keap1 moderated the transcription of genes that were induced by virus infection in concert with G9a, GLP, and NFкB p50 recruitment. G9a-GLP lysine methyltransferase activity was required for Keap1 to moderate the transcription of virus induced genes. G9a-GLP inhibitors enhanced the transcription of virus induced genes, and they augmented Keap1 and NFкB p50 recruitment, in parallel with the inhibition of H3K9me2 deposition. The interdependent effects of Keap1 and G9a-GLP on transcription and on the recruitment of each other constitute a feedback circuit that moderates the transcription of virus induced genes. G9a-GLP inhibitors augmented Keap1 binding to different genes in virus infected and in uninfected MEFs, whereas they inhibited H3K9me2 deposition that was induced by virus infection selectively. G9a-GLP inhibitors stabilized Keap1 retention in permeabilized MEFs and augmented Keap1 binding to specific genes in parallel. Keap1 was required for NFкB p50 recruitment, and for the augmentation of NFкB binding by G9a-GLP inhibitors. Keap1 and the electrophile tBHQ attenuated virus induced gene transcription through independent mechanisms, and they regulated the recruitment of different NFкB subunits.
Importance Excess and maladaptive immune responses to virus infections are a major contributing factor to the morbidity and mortality of COVID-19 and other diseases. Conversely, inadequate immune responses to vaccines and pathogens by individuals with suppressed immune function expose them to infections. Currently available drugs that enable therapeutic management of immune responses have low specificity and can blunt beneficial immune functions. The molecular mechanisms that moderate the transcription of genes that are induced by virus infection are incompletely understood. Characterization of the mechanisms whereby Keap1, G9a-GLP and NFкB p50 moderate virus induced gene transcription in mouse embryo fibroblasts represents the first step toward the identification of new targets for therapeutic agents that can modulate immune responsiveness.
Competing Interest Statement
The authors have declared no competing interest.
