Histone Methyltransferase Ash1l Suppresses Interleukin-6 Production and Inflammatory Autoimmune Diseases by Inducing the Ubiquitin-Editing Enzyme A20

•Ash1l attenuates inflammatory autoimmune disease by suppressing IL-6 production•Ash1l suppresses TLR-induced IL-6 production by enhancing A20 via SET domain•Ash1l facilitates H3K4 modification at Tnfaip3 promoter to induce its expression•Ash1l impairs TLR signaling by promoting A20-mediated NEMO and TRAF6 deubiquitination

SummaryHistone modifications play important roles in multiple physiological processes by regulating gene expression. However, the roles of histone modifications in immunity remain poorly understood. Here we report that Ash1l, a H3K4 methyltransferase, suppressed interleukin-6 (IL-6), and tumor necrosis factor (TNF) production in Toll-like receptor (TLR)-triggered macrophages, protecting mice from sepsis. Ash1l-silenced mice were more susceptible to autoimmune disease as a result of enhanced IL-6 production. Ash1l enhanced A20 expression through induction of H3K4 modification at the Tnfaip3 promoter via H3K4 methyltransferase activity of Ash1l SET (Su[var]3-9, E[z] and trithorax) domain. Ash1l suppressed NF-κB, mitogen-activated protein kinase (MAPK) pathways, and subsequent IL-6 production via facilitating A20-mediated NF-κB signal modulator NEMO and transducer TRAF6 deubiquitination. Therefore, Ash1l-mediated H3K4 methylation at the Tnfaip3 promoter is required for controlling innate IL-6 production and suppressing inflammatory autoimmune diseases, providing mechanistic insight into epigenetic modulation of immune responses and inflammation.