Histone-lysine N-methyltransferase EHMT1/EHMT2 mono- and dimethylate 'Lys-9' of histone H3 (H3K9me1 and H3K9me2, respectively) in euchromatin [1-5]. They interact to form an heterodimer. EHTM1 and EHTM2 contain ankyrin repeats (eight and seven ankyrin repeats, respectively), which bind the monomethylated RELA subunit of NF-kappa-B, a SET domain which interacts with WIZ and a pre-SET domain that binds three zinc ions via cysteine residues [1-5]. This entry represents a cysteine-rich region (CRR) found in the middle of the sequence, which is unique to EHTM1/2 and mediates protein-protein interactions and recruitment of the methyltransferases to specific sites in chromatin [5]. This domain adopts an unusual compact fold with four bound zinc atoms that contains an embedded RING domain [5], which represents a novel zinc-binding motif.

1: Histone H3 lysine 56 methylation regulates DNA replication through its interaction with PCNA. Yu Y, Song C, Zhang Q, DiMaggio PA, Garcia BA, York A, Carey MF, Grunstein M; Mol Cell. 2012;46:7-17. PMID:22387026

2: Zinc finger protein Wiz links G9a/GLP histone methyltransferases to the co-repressor molecule CtBP. Ueda J, Tachibana M, Ikura T, Shinkai Y; J Biol Chem. 2006;281:20120-20128. PMID:16702210

3: The ankyrin repeats of G9a and GLP histone methyltransferases are mono- and dimethyllysine binding modules. Collins RE, Northrop JP, Horton JR, Lee DY, Zhang X, Stallcup MR, Cheng X; Nat Struct Mol Biol. 2008;15:245-250. PMID:18264113

4: EHMT2/G9a as an Epigenetic Target in Pediatric and Adult Brain Tumors. Souza BK, Freire NH, Jaeger M, de Farias CB, Brunetto AL, Brunetto AT, Roesler R; Int J Mol Sci. 2021; [Epub ahead of print] PMID:34681949

5: The structure of the cysteine-rich region from human histone-lysine N-methyltransferase EHMT2 (G9a). Kerchner KM, Mou TC, Sun Y, Rusnac DV, Sprang SR, Briknarova K; J Struct Biol X. 2021;5:100050. PMID:34278292