Figure 5.
Effects of alkylated purines on the cleavage activity of human type II topoisomerases. Individual DNA substrates containing O6-methylguanine at the indicated positions of the Site I oligonucleotide (left) or N6-methyladenine at the indicated positions of the Site II oligonucleotide (right) were characterized. DNA cleavage enhancement was calculated relative to the level of scission observed for the wild-type substrate (None, set to 1). Reactions contained either topoisomerase IIα (closed bars) or topoisomerase IIβ (open bars). Data represent the averages of three independent experiments and standard deviations are indicated by error bars.