Abstract
Histone methylation is an epigenetic mark essential for gene regulation and development. We introduce peptide SPOT synthesis to study sequence specificity of the Dim-5 histone-3 lysine-9 methyltransferase. Dim-5 recognizes R8-G12 of the H3 tail with T11 and G12 being the most important specificity determinants. Exchange of H3 tail residue S10 and T11 by E strongly reduced methylation by Dim-5, suggesting that phosphorylation of S10 or T11 may regulate the activity of Dim-5. In the Dim-5/peptide structure, E227 interacts with H3R8 and D209 with H3-S10. Mutations of E227 or D209 caused predictable changes in the substrate preference, illustrating that peptide recognition of histone methyltransferases can be altered by protein design. Comparative analyses of peptide arrays with wild-type and mutant enzymes, therefore, are well suited to investigate the target specificity of protein methyltransferases and study epigenetic crosstalk.