G9a (BAT8 or Histone-lysine N-methyltransferase) is thought to be involved in intracellular protein-protein interaction and is a lysine-preferring histone methyltransferase. H3 Lys-9 methylation represents a specific tag for epigenetic transcriptional repression by recruiting HP1 proteins to methylated histones. The presence of the ankyrin repeats also suggests that G9a is involved in intracellular protein-protein interaction. Like Suv39h1, G9a transfers methyl groups to the lysine residues of histone H3, but with a 10- to 20-fold higher activity. G9a is localized to the nucleus but not in the repressive chromatin domains of centromeric loci, in which Suv39h1 family proteins were localized. This protein is probably targeted to histone H3 by different DNA-binding proteins like E2F6, MGA, MAX and/or DP1. G9a also methylates histone H1.