Epigenetic modifications induced by Blimp-1 regulate CD8+ T cell memory progression during acute virus infection
Blimp-1 regulates the overall accumulation of virus-specific CD8+ T cells during acute viral infections.  Increased proliferation and survival of Blimp-1-deficient CD8+ T cells is promoted by persistent cytokine responsiveness, resulting from sustained expression of CD25 and CD27.  Knockdown of these genes reduced the Blimp-1-deficient CD8+ T cell response.  Genome-wide ChIP-sequencing analysis identified CD25 and CD27 genes as direct targets of Blimp-1.  At the peak of the anti-viral response, but not earlier, Blimp-1 recruited the histone modifying enzymes G9a and HDAC2 to the Il2ra and Cd27 loci, thereby repressing expression of these genes.  In the absence of Blimp-1, the Il2ra and Cd27 genes exhibited enhanced histone H3-acetylation and reduced histone H3K9-trimethylation.  These data elucidate a central mechanism by which Blimp-1 acts as an epigenetic regulator, enhancing the numbers of short-lived effector cells while suppressing the development of memory precursor CD8+ T cells. Overall design: Naïve CD8+ T cells from OT-I TCR transgenic Rag1-/- mice were stimulated with anti-CD3 and anti-CD28 for three days in vitro, in the presence of IL-2 to up-regulate Blimp-1 protein. Genome-wide mapping of Blimp-1 binding in mouse CD8+ T cells was conducted.