E3 ubiquitin-protein ligase. May participate in methylation-dependent transcriptional regulation. Mediates ubiquitination with the E2 ubiquitin-conjugating enzyme UBC11. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. The RING fingers are required for ubiquitin ligase activity. The YDG domain mediates the interaction with histone H3.