KMT5C/SUV4-20h2 is a histone methyltransferase that specifically trimethylates Lys-20 of histone H4. H4 Lys-20 trimethylation represents a specific tag for epigenetic transcriptional repression. KMT5C/SUV4-20h2 mainly functions in pericentric heterochromatin regions, thereby playing a central role in the establishment of constitutive heterochromatin in these regions.