SETD6 lysine methylation of RelA couples GLP activity at chromatin to tonic repression of NF-κB signaling

Protein lysine methylation signaling is implicated in diverse biological and disease processes. Yet the catalytic activity and substrate specificity are unknown for many human protein lysine methyltransferases (PKMTs). We screened over forty candidate PKMTs and identified SETD6 as a methyltransferase that monomethylates chromatin-associated NF-κB RelA at lysine 310 (RelAK310me1). SETD6-mediated methylation rendered RelA inert and attenuated RelA-driven transcriptional programs, including inflammatory responses in primary immune cells. RelAK310me1 was recognized by the ankryin repeat of GLP, which under basal conditions, promoted a repressed chromatin state at RelA target genes through GLP-mediated H3K9 methylation. NF-κB activation-linked phosphorylation of RelA by PKCζ at serine 311 blocked GLP binding to RelAK310me1 and relieved target gene repression. Our findings establish a new mechanism by which chromatin signaling regulates inflammation programs.