Figure 7.

β,δ-elimination cleavage at abasic site DNA by hFPG1. (A) Incision and (B) probing for covalent hFPG1 DNA intermediates by NaCNBH₃ of AP DNA by hFPG1. An aliquot of 30 ng of purified E.coli Apn1, Nei, Nth, Fpg, hOGG1, hFPG1 or no enzyme was incubated with 100 fmol of a 25 bp duplex oligodeoxyribonucleotide containing a single abasic site opposite C. Strand cleavage was analysed by 20% PAGE and phosphorimaging. Protein–DNA complexes were separated by 10% Tricine–SDS–PAGE. (C) Opposite base-independent AP DNA cleaving activity of hFPG1. An aliquot of 30 ng of purified hOGG1 (white) or hFPG1 (grey) was incubated with 500 fmol of a 24 bp duplex oligodeoxyribonucleotide containing a single abasic site opposite A, C, G or T as indicated. Strand cleavage was quantified by 20% denaturing PAGE and phosphorimaging. The results shown represent the averages of three independent experiments.