Figure 9. Cross-linking of NMR and mouse cell extract proteins with AP DNA. 100 nM 5'-[32P] 32-mer AP DNA was incubated with 0.5 mg/ml of NMR (lanes 1–5) or mouse (lanes 6–10) cell extract proteins. The control probes contained buffer components and AP DNA (lane 12) or buffer components, AP DNA and 70 nM human recombinant PARP1 (lane 11). Samples represented in lanes 1 and 6 correspond to the extracts of non-irradiated cells. The reaction mixtures were incubated at 37ºC for 10 min. Then the probes were treated with 20 mM NaBH4. The products were then separated and analyzed as described in the section ‘Cross-linking of cell extract proteins with AP DNA’. The intensity of the 120-kDa product estimated as a part of cross-linked DNA (%) is shown at the top of the image.