Ku antigen is required to relieve G2 arrest caused by inhibition of DNA topoisomerase II activity by the bisdioxopiperazine ICRF-193.

Abstract

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.

• Authors: P Muñoz, F Baus, J Piette
• Journal: Oncogene (Oncogene) Vol. 20 Issue 16 Pg. 1990-9 (Apr 12 2001) ISSN: 0950-9232 [Print] England
• PMID: 11360183 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antigens, Nuclear
• Antineoplastic Agents
• DNA-Binding Proteins
• Diketopiperazines
• Enzyme Inhibitors
• Nuclear Proteins
• Piperazines
• Topoisomerase II Inhibitors
• 4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione
• DNA Helicases
• XRCC5 protein, human
• Xrcc6 protein, human
• Ku Autoantigen
• DNA Topoisomerases, Type II

Topics

• Animals
• Antigens, Nuclear
• Antineoplastic Agents (pharmacology)
• Chromosomes (physiology)
• Cricetinae
• Cricetulus
• DNA Helicases
• DNA Topoisomerases, Type II (metabolism)
• DNA-Binding Proteins (deficiency, physiology)
• Diketopiperazines
• Enzyme Inhibitors (pharmacology)
• Fibroblasts (drug effects, enzymology, ultrastructure)
• G2 Phase (drug effects, physiology)
• Ku Autoantigen
• Nuclear Proteins (deficiency, physiology)
• Piperazines (pharmacology)
• S Phase (physiology)
• Topoisomerase II Inhibitors