FIGURE 3.

Iron/copper-induced inhibition of both base excision and AP lyase activities for NEILs. A, AP lyase activity in the presence of iron and copper. a, the AP site substrate was generated by treating U-containing 51-nt duplex with Udg (E. coli). The effect of CuCl₂ (0.1 or 0.5 μm), FeSO₄ (1 or 10 μm) and FeCl₃ (1 or 10 μm) on the AP lyase activity of NEIL1 (b), NEIL2 (c), and OGG1 (d) was analyzed as described under “Experimental Procedures.” Lower panels, relative activity as in Fig. 1. B, analysis of trapped complexes. 50 fmol each of NEIL1 (a), NEIL2 (b), or OGG1 (c) was incubated with the substrate (upper panel) and metals (copper, 0.1 or 0.5 μm; iron, 1 or 10 μm) in the presence of 100 mm NaBH₄ at 37 °C for 45 min and analyzed by 12% SDS-PAGE. Lane 1, substrate alone. S, substrate; P, product; Error bars, S.E.