Mapping Single-Nucleotide Level Damage from Exposure to a Carcinogen

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A new study published in ACS Central Science demonstrates the ability to measure single-nucleotide level damage from a harmful substance found in cigarette and industrial smoke exposure. The DNA damage patterns investigated were the result of the known carcinogen Benzo(a)pyrene (BaP). The team of researchers performing the study mapped the effects of BaP exposure in human lung cells.

The initial process of BaP exposure in humans is well understood. Once BaP enters a body, it is metabolized into a new compound that can irreversibly attach itself to guanosines. Normal cellular repair mechanisms can remove these metabolites from the DNA, but unremoved metabolites can lead to base mutations that are prevalent in many cancer-driver genes. Understanding the distribution of the damage across the cells’ genome was the primary goal of the investigation.

During the study, the researchers added metabolized BaP into cell cultures of human lung cells and investigated where it attached to guanosines. Using single-nucleotide-resolution DNA mapping, they could identify the BaP metabolite’s location. The mapping was performed with an antibody to enrich alkylated DNA fragments, and a high-fidelity polymerase to replicate the DNA, which stalled at adducts that marked the specific locations of the metabolite.

The results showed a stable damage pattern across the genome regardless of the BaP metabolite concentration. In addition, they indicated that the DNA damage maintained similar mutation patterns to smoke-related lung cancers.

This study is reportedly the first of its kind to provide a single-nucleotide resolution genome-wide map of damage patterns from the carcinogen BaP in human cells. These findings suggest that this type of sequencing could be used for the identification of substances causing chemically induced modifications in the human genome. Researchers hope to utilize this technique in the future to identify and predict exposures that can lead to cancer.