Figure 5.

Alkaline-agarose gel electrophoresis of DNA from DB[a,l]P-treated MCF-7 cells. MCF-7 cells in culture were treated with DB[a,l]P for 24 hr (see Materials and Methods). (A) KpnI-restricted DNA from MCF-7 cell cultures treated with: DMSO (lanes 1 and 2); 1 or 2 μM DB[a,l]P (lanes 3–6; without or with methoxyamine). All samples underwent electrophoresis on a 0.5% alkaline-agarose gel and were probed with a ³²P riboprobe for the transcribed strand of the 20-kb fragment of the human DHFR gene. (B) Intensity of the 20-kb band of the DHFR gene of the DNA samples. All band intensities were normalized for the efficiency of sample loading on the gel through the use of a plasmid loading control.