Figure 3.

Human cells downregulating polβ are not sensitive to oxidative damaging agents. (A) MRC5-polι^KD and MRC5-NT cells were transfected with polβ-specific siRNAs (lanes 2 and 4) or scrambled siRNAs (lanes 1 and 3). After 72 h, cells were harvested and extracts were separated by SDS–PAGE, and incubated with anti-polι and anti-polβ antibodies. β-Actin detection was used as a loading control. (B) MRC5-polι^KD and MRC5-NT cells were transfected with a pool of polβ-specific siRNAs 24 h before treatment with increasing doses of H₂O₂ for 10 min at 4°C. Cells were counted 72 h later. Percentage of control growth was plotted for each data point, representing the mean of three independent experiments. (C) MRC5 cells were transfected with polβ-specific siRNA. After 48 h, they were exposed to hmdUrd for 24 h and surviving cells were counted 72 h later and plotted as described above.