Figure 3. Site specificity of DNA damage induced by histone H1-hydroperoxides in the presence of Cu(I).

The ³²P-5′-end-labelled 261 bp fragment (A) and 211 bp fragment (B) were exposed to 0.7 μM histone H1-hydroperoxides, 20 μM Cu(I) and calf thymus DNA (20 μM in DNA bases) 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% polyacrylamide/8 M urea gel using a DNA-sequencing system and visualized by autoradiography. The relative amounts of oligonucleotide were measured by scanning the autoradiogram with a laser densitometer. Horizontal axis: the nucleotide number of the human c-Ha-ras-1 proto-oncogene (A) and p53 tumour suppressor gene (B).