Journal
CHEMICAL RESEARCH IN TOXICOLOGY
Volume 32, Issue 4, Pages 753-761Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.chemrestox.8b00411
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Funding
- National Institute of Environmental Health Sciences [R01 ES-027059]
- National Center for Research Resources, National Institutes of Health (USA) [C06 RR-16572]
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The interchange between different repair mechanisms in human cells has long been a subject of interest. Here, we provide a direct demonstration that the oxidatively generated guanine lesions spiroiminodihydantoin (Sp) and 5-guanidinohydantoin (Gh) embedded in double-stranded DNA are substrates of both base excision repair (BER) and nucleotide excision repair (NER) mechanisms in intact human cells. Site-specifically modified, P-32-internally labeled double-stranded DNA substrates were transfected into fibroblasts or HeLa cells, and the BER and/or NER mono- and dual incision products were quantitatively recovered after 2-8 h incubation periods and lysis of the cells. DNA duplexes bearing single benzo[a]pyrene-derived guanine adduct were employed as positive controls of NER. The NER activities, but not the BER activities, were abolished in XPA(-/-) cells, while the BER yields were strongly reduced in NEIL1(-/-) cells. Co-transfecting different concentrations of analogous DNA sequences bearing the BER substrates 5-hydroxyuracil diminish the BER yields of Sp lesions and enhance the yields of NER products. These results are consistent with a model based on the local availability of BER and NER factors in human cells and their competitive binding to the same Sp or Gh BER/NER substrates.
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