title: Ku regulates the non-homologous end joining pathway choice of DNA double-strand break repair in human somatic cells.
abstract: The repair of DNA double-strand breaks (DSBs) is critical for the maintenance of genomic integrity and viability for all organisms. Mammals have evolved at least two genetically discrete ways to mediate DNA DSB repair: homologous recombination (HR) and non-homologous end joining (NHEJ). In mammalian cells, most DSBs are preferentially repaired by NHEJ. Recent work has demonstrated that NHEJ consists of at least two sub-pathways-the main Ku heterodimer-dependent or "classic" NHEJ (C-NHEJ) pathway and an "alternative" NHEJ (A-NHEJ) pathway, which usually generates microhomology-mediated signatures at repair junctions. In our study, recombinant adeno-associated virus knockout vectors were utilized to construct a series of isogenic human somatic cell lines deficient in the core C-NHEJ factors (Ku, DNA-PK(cs), XLF, and LIGIV), and the resulting cell lines were characterized for their ability to carry out DNA DSB repair. The absence of DNA-PK(cs), XLF, or LIGIV resulted in cell lines that were profoundly impaired in DNA DSB repair activity. Unexpectedly, Ku86-null cells showed wild-type levels of DNA DSB repair activity that was dominated by microhomology joining events indicative of A-NHEJ. Importantly, A-NHEJ DNA DSB repair activity could also be efficiently de-repressed in LIGIV-null and DNA-PK(cs)-null cells by subsequently reducing the level of Ku70. These studies demonstrate that in human cells C-NHEJ is the major DNA DSB repair pathway and they show that Ku is the critical C-NHEJ factor that regulates DNA NHEJ DSB pathway choice.
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America.
authors.forename: Farjana
authors.initials: F
authors.lastname: Fattah
authors.forename: Eu Han
authors.initials: EH
authors.lastname: Lee
authors.forename: Natalie
authors.initials: N
authors.lastname: Weisensel
authors.forename: Yongbao
authors.initials: Y
authors.lastname: Wang
authors.forename: Natalie
authors.initials: N
authors.lastname: Lichter
authors.forename: Eric A
authors.initials: EA
authors.lastname: Hendrickson
mesh_terms: D000818:Animals; D006224:Cricetinae; D004247:DNA / Q000235:genetics; D053903:DNA Breaks, Double-Stranded; D004265:DNA Helicases / Q000378:metabolism*; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000172:deficiency; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000172:deficiency / Q000378:metabolism; D051747:DNA-Activated Protein Kinase / Q000172:deficiency / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000378:metabolism; D045325:HCT116 Cells; D006238:Haploidy; D006801:Humans; D000072200:Ku Autoantigen; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000172:deficiency / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011995:Recombination, Genetic; D015203:Reproducibility of Results
chemical_list: D004268:DNA-Binding Proteins; C508551:NHEJ1 protein, human; D009687:Nuclear Proteins; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D004265:DNA Helicases; C106893:XRCC5 protein, human; D000072200:Ku Autoantigen; D011088:DNA Ligases; D045643:DNA Repair Enzymes; D000072481:DNA Ligase ATP