Topoisomerase IIalpha-dependent induction of a persistent DNA damage response in response to transient etoposide exposure.
Cytotoxicity of the topoisomerase II (topoII) poison etoposide has been ascribed to the persistent covalent trapping of topoII in DNA cleavage complexes that become lethal as cells replicate their DNA. However, short term etoposide treatment also leads to subsequent cell death, suggesting that the lesions that lead to cytotoxicity arise rapidly and prior to the onset DNA replication. In the present study 1h treatment with 25muM etoposide was highly toxic and initiated a double-stranded DNA damage response as reflected by the recruitment of ATM, MDC1 and DNA-PKcs to gammaH2AX foci. While most DNA breaks were rapidly repaired upon withdrawal of the etoposide treatment, the repair machinery remained engaged in foci for at least 24h following withdrawal. TopoII siRNA ablation showed the etoposide toxicity and gammaH2AX response to correlate with the inability of the cell to correct topoIIalpha-initiated DNA damage. gammaH2AX induction was resistant to the inhibition of DNA replication and transcription, but was increased by pre-treatment with the histone deacetylase inhibitor trichostatin A. These results link the lethality of etoposide to the generation of persistent topoIIalpha-dependent DNA defects within topologically open chromatin domains.
The Ottawa Health Research Institute, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada.
Sébastien
S
Soubeyrand
Louise
L
Pope
Robert J G
RJ
Haché
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000951:Antigens, Neoplasm / Q000276:immunology* / Q000378:metabolism / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004247:DNA / Q000187:drug effects; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects* / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics*; D004261:DNA Replication / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000378:metabolism / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D005047:Etoposide; D005434:Flow Cytometry; D016195:G2 Phase / Q000187:drug effects / Q000235:genetics; D006801:Humans; D020014:K562 Cells; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D025521:Tumor Suppressor Proteins
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000951:Antigens, Neoplasm; D000972:Antineoplastic Agents, Phytogenic; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D005047:Etoposide; D004247:DNA; D004250:DNA Topoisomerases, Type II