Reaction catalyzed by [histone H3]-lysine27 N-trimethyltransferase (2.1.1.356)

		+		histone H3(K27)	=			+		N-methylated histone H3(K27)
	S-adenosyl-L-methionine	+		histone H3(K27)	=		S-adenosyl-L-homocysteine	+		N-methylated histone H3(K27)