DNA Repair of Benzo[A]Pyrene Diol Epoxide-DNA Adducts in the DHFR Gene of a Human Embryonic Kidney Cell Line

Abstract The repair of polycyclic aromatic hydrocarbon (PAH)-DNA adducts by nucleotide excision repair is a critical factor in the human response to exposure to these environmental carcinogens. In this study, we utilized a laser cleavage technique and Southern Blotting to measure the repair of benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) adducts in the transcribed and nontranscribed strands of a human cell line containing an amplified DHFR gene. Treatment of the cultures with 1.5 μM BPDE resulted in little adduct removal for 24 hours, whereas 1 μM BPDE-treated cells removed most of the adducts over a 24 hour period. Southern analyses of repair in individual strands of the human cell line revealed that adducts on the transcribed strand are repaired more rapidly than those on the non-transcribed strand during the first 8 hours after 1 μM BPDE treatment. These results suggest that human cells can repair BPDE-DNA adducts through a transcription-coupled repair process.

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