Representative examples of SET-domain-containing structures. (a) Neurospora crassa DIM-5 (Protein DataBank (PDB) code 1PEG.pdb); (b) human SET7/9 (1O9S.pdb). The pre-SET, SET, and post-SET domains in DIM-5 and the N-SET, SET, and C-SET domains in SET7/9 are indicated. The pseudoknot formed by two conserved SET motifs and the bound histone H3 peptide are also illustrated. The reaction byproduct AdoHcy is in stick representation and the zinc ions are shown as balls. N, amino terminus; C, carboxyl terminus.