title: Nonhomologous end-joining deficiency of L5178Y-S cells is not associated with mutation in the ABCDE autophosphorylation cluster.
abstract: Cells with mutated autophosphorylation sites in the ABCDE cluster of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) are defective in the repair of ionising radiation-induced DSB, but show in an in vitro test the same DNA-PK activity as the cells possessing wild type enzyme. Nevertheless, the mutated DNA-PK is able to undergo ATP-dependent autophosphorylation and inactivation. This characteristics correspond well with the phenotypic features of the L5178Y-S (LY-S) cell line that is defective in DSB repair, shows a pronounced G1 phase radiosensitivity, but in which the level of DNA-PK activity present in total cell extracts is similar to that of its radioresistant counterpart L5178Y-R (LY-R) cell line. The purpose of this work was to examine the possible alterations in the sequence encoding the cluster of autophosphorylation sites in the DNA-dependent protein kinase in LY-S cells. Despite the presence of phenotypic features indicating the possibility of such alterations, no differences were found between the sequences coding for the autophosphorylation sites in L5178Y-R and L5178Y-S cells. In conclusion, the repair defect in LY-S cells is not related to the structure of the DNA-PK autophosphorylation sites (ABCDE casette).
authors.affiliation: Department of Radiobiology and Health Protection, Institute of Nuclear Chemistry and Technology, Warszawa, Poland.
authors.forename: Kamil
authors.initials: K
authors.lastname: Brzóska
authors.forename: Marcin
authors.initials: M
authors.lastname: Kruszewski
authors.forename: Irena
authors.initials: I
authors.lastname: Szumiel
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D004249:DNA Damage; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry*; D010766:Phosphorylation; D011839:Radiation, Ionizing; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051747:DNA-Activated Protein Kinase; C497264:Prkdc protein, mouse