Year: 2005
Type: article
Abstract: Biochemical and genetic studies support the view that the majority of DNA double-strand breaks induced in the genome of higher eukaryotes by ionizing radiation are removed by two pathways of nonhomologous end joining (NHEJ) termed D-NHEJ and B-NHEJ. Whereas D-NHEJ depends on the activities of the DNA-dependent protein kinase and DNA ligase IV/XRCC4, components of B-NHEJ have not been identified. Using extract fractionation, we show that the majority of DNA end joining activity in extracts of HeLa cells derives from DNA ligase III. DNA ligase III fractionates through two columns with the maximum in DNA end joining activity and its depletion from the extract causes loss of activity that can be recovered by the addition of purified enzyme. The same fractionation protocols provide evidence for an additional factor strongly enhancing DNA end joining and shifting the product spectrum from circles to multimers. An in vivo plasmid assay shows that DNA ligase IV-deficient mouse embryo fibroblasts retain significant DNA end joining activity that can be reduced by up to 80% by knocking down DNA ligase III using RNA interference. These in vivo and in vitro observations identify DNA ligase III as a candidate component for B-NHEJ and point to additional factors contributing to NHEJ efficiency.
Source: Cancer Research
Institutions: Sidney Kimmel Cancer Center, University of Duisburg-Essen
Language: English
Topic: DNA Repair Mechanisms
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: bronze
Funders: U.S. Department of Health and Human Services, University of Rochester, University of Cambridge, European Commission, University of Sussex, Deutsche Forschungsgemeinschaft, Volkswagen Foundation, Institut National de la Santé et de la Recherche Médicale, Institut Gustave-Roussy, Universität Duisburg-Essen, National Institutes of Health, Medical Research Council, National Cancer Institute
OpenAlex ID: W1987369963