FIGURE 2.

TDG excises fC and caC but not hmC. An electrophoretic assay of TDG activity for G·T, G·fC, G·caC, and G·hmC DNA substrates is shown. TDG (5 μm) was incubated with substrate DNA (0.5 μm) for 30 s at 37 °C followed by alkaline-induced quenching and cleavage of the DNA at TDG-generated abasic sites (S indicates substrate, and P indicates product). For G·hmC, reactions were also performed for 1 and 2 h at 37 °C and for 18 h at 22 °C.