Figure 3.

APE1 exonuclease activity on substrates containing oxidative lesions in the digested strand of the substrate. (A) Forked substrates (14 fmol, undamaged or containing a single lesion in the digested strand) were incubated with APE1 (50 fmol) for 15 min at 37°C. (B) Forked substrates (5 fmol, undamaged or containing 5OH-Ura) were incubated for 15 min at 37°C with APE1 (140 fmol) and Ku (45 fmol) as indicated. Positions of the lesions are indicated by arrows. Reactions were terminated and reaction products were processed as described for Figure 1. Und, undamaged; 8oxo-Ade, 8-oxoadenine; 8oxo-Gua, 8-oxoguanine; 5OH-Cyt, 5-hydroxycytosine; 5OH-Ura, 5-hydroxyuracil; 5OHMe-Ura, 5-hydroxymethyluracil; 2OH-Ade, 2-hydroxyadenine.