HMT_other: Human SET7/9 mono-methylates H3K4, whereas S. cerevisiae SET1 di- or tri-methylates the same residue. The strict lysine specificity of these enzymes is in distinct contrast to Drosophila ASH1 (a member of the SET1 family), mammalian G9a, human EZH1 and EZH2 and mouse NSD1, enzymes that can methylate two or more different lysine residues. In some cases, the functions of SET-domain enzymes are not confined to histone methylation. For instance, human SET7/9 has recently been reported to methylate Lys189 in the general transcription factor TAF10, resulting in an increased affinity for RNA polymerase II and transcriptional activation of certain TAF10-dependent genes. SET7/9 has also been reported to methylate p53, increasing the stability of this short lived tumor-suppressor protein. (1)

Reference
1. Dillon SC, Zhang X, Trievel RC, Cheng XD.The SET-domain protein superfamily: protein lysine methyltransferases.Genome Biol.2005;6:227. PMID: 16086857.