TABLE 2.

Decreased mutation frequency of SupF tRNA gene in the plasmid pZ189 replicated in the FL cells with Polη knocked down

	siRNA control		siRNA-Polη
	EV	IRF1	IRF1
Transformants	11,012	11,284	10,844
Mutants	3	16	4
Mutation frequencya (×10−4)	2.7	14.2b	3.7
Induced mutation frequencyc (×10−4)		32.2	1.0

^a Mutation frequency: No. of mutants/No. of transformants.

^b p < 0.01 versus EV-transfected FL cells (χ²-test).

^c Induecd mutation frequency: mutation frequency of IRF1 minus mutaion frequency of EV.