Symmetric dimethylation of H3R2 is a newly identified histone mark that supports euchromatin maintenance.

Although the asymmetric dimethylation of histone H3R2 acts as a repressive mark, new studies reveal that symmetrically dimethylated H3R2 (H3R2me2s) is a functional histone mark in vivo. The RBBP7 co-repressor is excluded from binding H3R2me2s in favor of the coactivator WDR5, which poises euchromatic genes for transcription activation upon cell-cycle exit and differentiation.