Structure of SET domain proteins: a new twist on histone methylation.

The methylation of lysine residues on histone tails is catalyzed by proteins containing a conserved SET domain. A recent flurry of structures of SET domain proteins has revealed a new protein fold and a scaffold for understanding catalysis and substrate binding by these enzymes. The prospect that histone methylation might form an epigenetic code and the implicated involvement of SET domain proteins in cancer assures that structure-function studies of these enzymes will continue until their detailed mechanism of action is determined.