Table 1.

Single base substitution mutation spectrum resulting from ENU treatment

Species	Gene	Repair	Single base substitution, %a						Ref.
			G∶C→A∶T TSb (O6–G)c	G∶C→T∶A TVb	G∶C→C∶G TVb	A∶T→G∶C TSb (O4–T)c	A∶T→T∶A TVb (O2–T)c	A∶T→C∶G TVb
In Vivo
Mouse	lacI	AGT+	17	11	2	29	29	11	8
Mouse	HPRT	AGT+	4	2	0	28	55	12	9
Rat	HPRT	AGT+	10	4	0	25	48	13	10
Ratd	HPRT	AGT+	16	9	0	13	44	19	11
	Mean		12	7	0	24	44	13
	Mean			19 (G∶C)			81 (A∶T)
In Vitro
Ratd	HPRT	AGT+	27	5	0	14	45	9	12
Humane	HPRT	AGT+	21	0	6	12	52	9	13
Humanf	HPRT	AGT+	19	15	0	31	23	12	14
	Mean		22	7	2	19	40	10
	Mean			31 (G∶C)			69 (A∶T)
Humane	HPRT	AGT−	42	3	0	11	34	11	13
Humanf	HPRT	AGT−	50	1	7	7	21	11	14
	Mean		46	2	4	9	28	11
	Mean			52 (G∶C)			48 (A∶T)

^a G∶C→A∶T mutations occurring in CpG dinucleotides have not been included because they arise through a different mechanism involving the deamination of 5-methyl C. 

^bTS = transition mutation and TV = transversion mutation. 

^c In vitro treatment with ENU yields the following levels of specific DNA adducts (relative to N7-G = 1.00): O⁶–G = 0.93, O²–T = 0.33, N3–A = 0.23, O²–C = 0.14, and O⁴–T = 0.06. The O⁶–G adducts are removed through AGT. The O²–T adducts appear to persist. 

^dSame cells in vivo and in vitro. 

^eSame cells AGT⁺ and AGT⁻. 

^fSame cells AGT⁺ and AGT⁻.