DNA ligase III and DNA ligase IV carry out genetically distinct forms of end joining in human somatic cells |
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| Affiliation: | 1. Graduate Program in University of Brasilia, Health Sciences and Technologies, Brasilia, Brazil;2. JAXA/Institute of Space and Astronautical Science, Sagamihara, Japan;3. Department of Hard Tissue Engineering, Tokyo Medical and Dental University, Tokyo, Japan;1. INRA, Plateforme d’Analyse Intégrative des Biomolécules, Laboratoire de Spectrométrie de Masse, F-37380 Nouzilly, France;2. INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380 Nouzilly, France;3. CNRS, UMR7247, F-37380 Nouzilly, France;4. Université François Rabelais de Tours, F-37000 Tours, France;5. IFCE, F-37380 Nouzilly, France;6. INRA, UMR1282 Infectiologie et Santé Publique, F-37380 Nouzilly, France;7. Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000 Tours, France;3. From the Laboratory of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan;4. the Laboratory of Proteome Research, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka 567-0085, Japan;1. National Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, PR China;2. Department of Plant Sciences, North Dakota State University, Fargo, ND 58108, USA;1. Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers Robert Wood Johnson Medical School, 195 Little Albany Street, New Brunswick, NJ 08901, USA;2. Genome Editing Shared Resource, Rutgers Cancer Institute of New Jersey, Rutgers Robert Wood Johnson Medical School, 195 Little Albany Street, New Brunswick, NJ 08901, USA;3. Department of Chemistry and Chemical Biology, and Center for Biotechnology and Interdisciplinary Sciences, Rensselaer Polytechnic Institute, 110 8th St, Troy, NY 12180, USA |
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| Abstract: | Ku-dependent C-NHEJ (classic non-homologous end joining) is the primary DNA EJing (end joining) repair pathway in mammals. Recently, an additional EJing repair pathway (A-NHEJ; alternative-NHEJ) has been described. Currently, the mechanism of A-NHEJ is obscure although a dependency on LIGIII (DNA ligase III) is often implicated. To test the requirement for LIGIII in A-NHEJ we constructed a LIGIII conditionally-null human cell line using gene targeting. Nuclear EJing activity appeared unaffected by a deficiency in LIGIII as, surprisingly, so were random gene targeting integration events. In contrast, LIGIII was required for mitochondrial function and this defined the gene's essential activity. Human Ku:LIGIII and Ku:LIGIV (DNA ligase IV) double knockout cell lines, however, demonstrated that LIGIII is required for the enhanced A-NHEJ activity that is observed in Ku-deficient cells. Most unexpectedly, however, the majority of EJing events remained LIGIV-dependent. In conclusion, although human LIGIII has an essential function in mitochondrial maintenance, it is dispensable for most types of nuclear DSB repair, except for the A-NHEJ events that are normally suppressed by Ku. Moreover, we describe that a robust Ku-independent, LIGIV-dependent repair pathway exists in human somatic cells. |
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| Keywords: | Double-strand break repair Non-homologous end joining Ku Ligase III Ligase IV Gene targeting C-NHEJ A-NHEJ Homologous recombination |
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