Reaction catalyzed by NAD+ ADP-ribosyltransferase (2.4.2.30)

	NAD+	+		histone H2A	=			+		(ADP-D-ribosyl)-histone H2A
	NAD+	+		histone H2A	=		nicotinamide	+		(ADP-D-ribosyl)-histone H2A