Figure 1. Autoradiogram of ³²P-labelled DNA fragments incubated with various histone protein-hydroperoxides in the presence of Cu(I).

The reaction mixtures contained the ³²P-5′-end-labelled 337 bp DNA fragment, calf thymus DNA (20 μM in DNA bases), 0.7 μM of histone protein-hydroperoxides (histone H1, H2A, H3 and H4) and 20 μM CuCl in 200 μl of 10 mM sodium phosphate buffer (pH 7.4) containing 5 μM DTPA. After incubation at 37 °C for 60 min, DNA fragments were treated with 10 units of Fpg protein at 37 °C for 120 min. The DNA fragments were electrophoresed on an 8% (w/v) polyacrylamide/8 M urea gel (12 cm×16 cm), and autoradiograms were obtained by exposing an X-ray film to the gel. Oligonucleotides generated by hydroperoxide-induced DNA damage are indicated by arrows. The bands above these oligonucleotides are single- and double-strand intact DNA fragments.