This optimized protocol (including links to instruction videos) describes a comet-based in vitro DNA repair assay that is relatively simple, versatile, and inexpensive, enabling the detection of base and nucleotide excision repair activity. Protein extracts from samples are incubated with agarose-embedded substrate nucleoids ('naked' supercoiled DNA) containing specifically induced DNA lesions (e.g., resulting from oxidation, UVC radiation or benzo[a]pyrene-diol epoxide treatment). DNA incisions produced during the incubation reaction are quantified as strand breaks after electrophoresis, reflecting the extract's incision activity. The method has been applied in cell culture model systems, human biomonitoring and clinical investigations, and animal studies, using isolated blood cells and various solid tissues. Once extracts and substrates are prepared, the assay can be completed within 2 d.

Biomedical Center Medical Faculty in Pilsen Charles University Prague Czech Republic

Centre for Environmental Sciences Hasselt University Hasselt Belgium

Department of Environmental Chemistry Health Effects Laboratory NILU Norwegian Institute for Air Research Kjeller Norway

Department of Medical Genetics 3rd Faculty of Medicine Charles University Prague Czech Republic

Department of Molecular Biology of Cancer Institute of Experimental Medicine of the Czech Academy of Sciences Prague Czech Republic

Department of Nutrition University of Oslo Oslo Norway

Department of Pharmacology and Toxicology School for Nutrition and Translational Research in Metabolism Maastricht University Maastricht the Netherlands

Department of Pharmacology and Toxicology University of Navarra and IdiSNA Navarra Institute for Health Research Pamplona Spain

Genetics and Biotechnology Department and Veterinary and Animal Research Centre Universidade de Trás os Montes e Alto Douro Vila Real Portugal

Section of Environmental Health Department of Public Health University of Copenhagen Copenhagen Denmark

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Measuring DNA modifications with the comet assay: a compendium of protocols