Journal Article

Presence of benzo[<i>a</i>]pyrene diol epoxide adducts in target DNA leads to an increase in UV-induced DNA single strand breaks and <i>supF</i> gene mutations

Michael N. Routledge, Keith I. E. McLuckie, George D. D. Jones, Peter B. Farmer and Elizabeth A. Martin

in Carcinogenesis

Volume 22, issue 8, pages 1231-1238
Published in print August 2001 | ISSN: 0143-3334
Published online August 2001 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/22.8.1231
Presence of benzo[a]pyrene diol epoxide adducts in target DNA leads to an increase in UV-induced DNA single strand breaks and supF gene mutations

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Exposure to DNA damaging agents and mutagens often occurs as combinations of agents, or as complex mixtures of chemicals. We found that plasmid DNA adducted with benzo[a]pyrene diol epoxide (BPDE) was more susceptible to UV-induced single strand breaks than was control DNA. To determine whether the increase in DNA damage also applied to mutagenic lesions, the supF gene forward mutation assay was used to compare mutations induced by BPDE alone, UVB, UVC, BPDE followed by UVB and BPDE followed by UVC. It was found that the mutation frequency for BPDE + UVB (1167 in 104 transformants) was higher than BPDE alone (12 in 104 transformants) or UVB alone (446 in 104 transformants), and the mutation frequency for BPDE + UVC (197 in 104 transformants) was higher than BPDE alone or UVC alone (26 in 104 transformants). For BPDE + UVB and BPDE + UVC there was a significant increase in plasmids with multiple mutations. Whilst these indicate error prone repair due to the single strand breaks, the different mutation frequencies in plasmids treated to give similar levels of strand breaks suggest other mechanisms for the mutations in plasmids with single mutation events. The spectrum of non-multiple mutations in the two combined treatments included both UV signature mutations (GC→AT as the most common mutation) and BPDE signature mutations (GC→TA and GC→CG as the most common mutations). However, the increase in absolute mutation frequency of BPDE signature mutations between BPDE treatment and BPDE + UV treatment was greater than the increase in absolute mutation frequency of UV signature mutations, even though the level of BPDE adducts was identical in each case. These results suggest two possibilities: (i) the BPDE adducts are photoactivated to a more mutagenic lesion, or (ii) the presence of UV lesions lead to the BPDE adducts becoming more mutagenic.

Keywords: BPDE, benzo[a]pyrene diol epoxide; PAH, polycyclic aromatic hydrocarbon; HRP, horseradish peroxidase.

Journal Article.  7335 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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