Figure 3.

Effect of DNA-PKcs on 5′dRP/AP lyase activity. A. 1 nM radiolabeled AP substrate containing an abasic site was incubated at 37°C for 10 min with 2 nM Ku or the 2A/6A mutant Ku described in Figure 2. 2nM DNA-PKcs was included as noted. Mg&ATP, reactions were supplemented with 5mM MgCl₂ and 100 μM ATP. Average velocities and standard deviations were determined from three independent experiments, and expressed relative to the activity observed with WT Ku heterodimer alone. B. Reactions were performed as in panel A, but supplemented with NaBH₄, and analyzed by SDS-PAGE and phosphorimaging. *, unknown adducting species.