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Relationship between benzo(a)pyrene-DNA adducts and somatic mutation and recombination in Drosophila melanogaster
M Zordan1, M Osti, S Pavanello
1Department of Biology, University of Padova, Italy.
Abstract:
The evaluation of the relationship between the dose to DNA of a mutagen/carcinogen and in vivo somatic cell mutagenesis may provide information on the mechanisms leading to induced mutational events. This can be achieved, for example, by coupling test systems that permit the detection of somatic mutation and recombination on the basis of phenotypic changes in cuticular structures of Drosophila melanogaster, with methods for the quantitation of carcinogen-DNA adducts such as the 32P-postlabeling technique. In this article, we evaluate the quantitative relationship between BaP-DNA adduct formation, determined by 32P-postlabeling, and the induction of mutant cells in the wing marker version of the somatic mutation and recombination test (SMART) in Drosophila melanogaster. The total single clones in the trans-heterozygous mwh/flr3 flies show a linear relationship with the BaP-DNA adduct levels, suggesting a single hit mechanism for the genetic damage giving rise to this type of clones. In contrast, the twin clones (which are of recombinational origin) display a linear-quadratic relationship with the adduct levels, suggesting that multiple hits may be involved in generating these clones. The total single clones in the mwh/TM3, Ser flies (in which mitotic recombination is suppressed) show a logarithmic relationship with the adduct levels. The discussion of these data in terms of the pathways that may be involved in the repair of the BaP-DNA adducts leads to the suggestion that in Drosophila melanogaster the repair of Bap metabolite-DNA adducts in somatic cells may proceed, in large part, via post-replicative recombinational repair.
Insights
This study links benzo[a]pyrene-DNA adducts to mutations in Drosophila melanogaster. Different mutation types suggest distinct DNA repair pathways, with post-replicative recombinational repair being significant for somatic cells.
Area of Science:
- Toxicology and Genetics
- Molecular Biology
- Carcinogenesis Research
Background:
- Understanding the relationship between DNA damage and mutations is crucial for carcinogenicity assessment.
- In vivo somatic cell mutagenesis studies in Drosophila melanogaster offer a model for investigating mutagenic mechanisms.
- Quantifying carcinogen-DNA adducts, like those from benzo[a]pyrene (BaP), provides a direct measure of exposure.
Purpose of the Study:
- To quantitatively assess the relationship between BaP-DNA adduct formation and the induction of somatic mutations in Drosophila melanogaster.
- To investigate the underlying mechanisms of genetic damage and repair following exposure to a model carcinogen.
- To differentiate between mutation types (single vs. twin clones) and their correlation with adduct levels.
Main Methods:
- Utilized the somatic mutation and recombination test (SMART) in Drosophila melanogaster wing assays.
- Quantified BaP-DNA adducts using the 32P-postlabeling technique.
- Analyzed dose-response relationships for different types of genetic events (single clones, twin clones).
Main Results:
- A linear relationship was observed between BaP-DNA adducts and total single clones, indicating a single-hit mechanism.
- Twin clones, arising from recombination, showed a linear-quadratic relationship with adducts, suggesting multiple-hit involvement.
- Single clones in a suppressed recombination background exhibited a logarithmic relationship with adduct levels.
Conclusions:
- The distinct dose-response relationships suggest different genetic mechanisms for various mutation types.
- Data support the hypothesis that post-replicative recombinational repair is a major pathway for repairing BaP metabolite-DNA adducts in Drosophila somatic cells.
- This study provides insights into DNA repair pathways and their role in mutagenesis by environmental carcinogens.
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