The SET8 H4K20 protein lysine methyltransferase has a long recognition sequence covering seven amino acid residues

► SET8 is a H4K20 specific monomethyltransferase. ► SET8 has a long recognition sequence comprising R H (RKY) K20 (VILFY) (LFY) R. ► SET8 is inhibited by methylation of the R at −3 position. ► We showed methylation of new peptide substrates. ► SET8 only methylates lysine residues within an unfolded part of the target protein.