Abstract
SET domain methyltransferases deposit methyl marks on specific histone tail lysine residues and play a major role in epigenetic regulation of gene transcription. We solved the structures of the catalytic domains of GLP, G9a, Suv39H2 and PRDM2, four of the eight known human H3K9 methyltransferases in their apo conformation or in complex with the methyl donating cofactor, and peptide substrates. We analyzed the structural determinants for methylation state specificity, and designed a G9a mutant able to tri-methylate H3K9. We show that the I-SET domain acts as a rigid docking platform, while induced-fit of the Post-SET domain is necessary to achieve a catalytically competent conformation. We also propose a model where long-range electrostatics bring enzyme and histone substrate together, while the presence of an arginine upstream of the target lysine is critical for binding and specificity.Enhanced version This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3D representations and animated transitions. Please note that a web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1.
Highlights
Post-translational modifications of histone proteins regulate chromatin compaction, mediate epigenetic regulation of transcription, and control cellular differentiation in health and disease [1,2]
Methylation of H3K27 and H4K20 are associated with a repressed state of chromatin, whereas expressed genes are methylated at H3K4, H3K36 and H3K79 ([3,6] for review)
Overall Structure We have solved the crystal structures of the catalytic domain of four H3K9 methyltransferases: (1) the complexes of GLP/ EHMT1 co-crystallized with the co-factor product S-adenosyl-L
Summary
Post-translational modifications of histone proteins regulate chromatin compaction, mediate epigenetic regulation of transcription, and control cellular differentiation in health and disease [1,2]. We report the high-resolution crystal structures of the methyltransferase domains of GLP, G9a, SUV39H2 and PRDM2, and propose a structural mechanism for substrate recognition.
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