Fig. 2.

Knocking out APOBEC3B decreases the spontaneous mutation rate. (A) The mutation rates of HepG2 (filled circle), A3BKO (empty circle) and control Cas9-expressing cells (cross) were determined by plotting mutation frequencies vs population doublings and calculating the slope by linear regression. The slope of the curve yields the mutation rate (mutations/cell/generation). (B) Mutation frequencies of HepG2, A3BKO, A3B-tGFP and A3B-KO + A3B-tGFP cells were calculated as (number of colonies with 6-TG)/(number of colonies without 6-TG × number of seeded cells × plating efficiency). (C) Radiation dose–survival curves of HepG2, A3BKO, Mock and A3B cells plated immediately after treatment with 2, 5 and 10 Gy of irradiation. Data are presented as means ± SEM of at least three experiments; ^*P < 0.05. The same experiment was performed with two other independent clones of A3BKO cells and three independent clones of A3B-tGFP.