Ku antigen is required to relieve G2 arrest caused by inhibition of DNA topoisomerase II activity by the bisdioxopiperazine ICRF-193.
Ku antigen is necessary for DNA double-strand break (DSB) repair through its ability to bind DNA ends with high affinity and to recruit the catalytic subunit of DNA-PK to the DSBs. Ku-deficient cells are hypersensitive to agents causing DSBs in DNA but also to the DNA topoisomerase II (topo II) inhibitor ICRF-193, which does not induce DSBs. This suggests a new role of Ku antigen, that is independent of DSB repair by DNA-PK. Here we characterize the basis for the hypersensitivity of Ku-deficient cells to ICRF-193. Chromosome condensation and segregation, which are dependent on topo II, but also the catalytic activity of topo II in late S-G2 were inhibited to a comparable extent when ICRF-193 was applied to Ku-deficient cells or wild-type cells. However, mutant cells arrested in G2 by ICRF-193 treatment were unable to progress into M phase upon drug removal, although drug-trapped topo II complexes were removed from DNA and the two isoforms of topo II recovered their catalytic activity as in wild-type cells. The reversibility of G2 arrest was recovered by complementation of mutant cells with a human Ku86 cDNA. Notably, chromosome condensation was abnormal in Ku-deficient cells after suppression of the G2 arrest by caffeine, even in the absence of ICRF-193. These results reflect the involvement of Ku-antigen in the cellular response to topo II inhibition, more particularly in relieving G2 arrest caused by topo II inhibition in late S/G2 and the subsequent recovery of chromosome condensation.
Muñoz
P
P
Institut de Génétique Moléculaire de Montpellier, UMR 5535, IFR 24, CNRS, 1919 route de Mende, 34293 Montpellier Cedex 5, France.
Baus
F
F
Piette
J
J
D000818:Animals; D034961:Antigens, Nuclear; D000970:Antineoplastic Agents / Q000494:pharmacology; D002875:Chromosomes / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D004265:DNA Helicases; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000502:physiology*; D054659:Diketopiperazines; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D016195:G2 Phase / Q000187:drug effects / Q000502:physiology*; D000072200:Ku Autoantigen; D009687:Nuclear Proteins / Q000172:deficiency / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology*; D016196:S Phase / Q000502:physiology; D059005:Topoisomerase II Inhibitors
D034961:Antigens, Nuclear; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D054659:Diketopiperazines; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D010879:Piperazines; D059005:Topoisomerase II Inhibitors; C070899:4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D004250:DNA Topoisomerases, Type II