title: Ku80-deleted cells are defective at base excision repair.
abstract: Ku80 forms a heterodimer with Ku70, called Ku, that repairs DNA double-strand breaks (DSBs) via the nonhomologous end joining (NHEJ) pathway. As a consequence of deleting NHEJ, Ku80-mutant cells are hypersensitive to agents that cause DNA DSBs like ionizing radiation. Here we show that Ku80 deletion also decreased resistance to ROS and alkylating agents that typically cause base lesions and single-strand breaks (SSBs). This is unusual since base excision repair (BER), not NHEJ, typically repairs these types of lesions. However, we show that deletion of another NHEJ protein, DNA ligase IV (Lig4), did not cause hypersensitivity to these agents. In addition, the ROS and alkylating agents did not induce γ-H2AX foci that are diagnostic of DSBs. Furthermore, deletion of Ku80, but not Lig4 or Ku70, reduced BER capacity. Ku80 deletion also impaired BER at the initial lesion recognition/strand scission step; thus, involvement of a DSB is unlikely. Therefore, our data suggests that Ku80 deletion impairs BER via a mechanism that does not repair DSBs.
authors.affiliation: The Department of Molecular Medicine, The University of Texas Health Science Center, San Antonio, TX 78245-3207, USA.
authors.forename: Han
authors.initials: H
authors.lastname: Li
authors.forename: Teresa
authors.initials: T
authors.lastname: Marple
authors.forename: Paul
authors.initials: P
authors.lastname: Hasty
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology; D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D059766:DNA End-Joining Repair / Q000235:genetics; D045647:DNA Glycosylases / Q000235:genetics / Q000378:metabolism; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics*; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D000072200:Ku Autoantigen; D051379:Mice; D008969:Molecular Sequence Data; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D010269:Paraquat / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000477:Alkylating Agents; D034961:Antigens, Nuclear; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; C000607893:LIG4 protein, human; D009153:Mutagens; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen; D011088:DNA Ligases; D000072481:DNA Ligase ATP; D010269:Paraquat