Polycomb group (PcG) protein (By similarity). Catalytic subunit of the prc2/eed-ezh2 complex, which methylates 'Lys-9' and 'Lys-27' of histone H3, leading to transcriptional repression of the affected target gene (By similarity). May repress transcription of the egr2 and en2 genes. May regulate the circadian clock via histone methylation at the promoter of the circadian genes (By similarity). L-lysyl(27)-[histone H3] + 3 S-adenosyl-L-methionine = 3 H(+) + N(6),N(6),N(6)-trimethyl-L-lysyl(27)-[histone H3] + 3 S-adenosyl-L-homocysteine Component of the prc2/eed-ezh2 complex. Does not appear to be maternally expressed. Zygotic expression begins at late blastula, increases at mid and late gastrula, and peaks in the early neurula. Expression is restricted to the anterior nervous system. Induced by inhibition of BMP signaling. Belongs to the class V-like SAM-binding methyltransferase superfamily. Histone-lysine methyltransferase family. EZ subfamily.