A novel mechanism of cell killing by anti-topoisomerase II bisdioxopiperazines.

Jensen LH, Nitiss KC, Rose A, Dong J, Zhou J, Hu T, Osheroff N, Jensen PB, Sehested M, Nitiss JL
J Biol Chem. 2000 275 (3): 2137-46

PMID: 10636919 · DOI:10.1074/jbc.275.3.2137

Bisdioxopiperazines are a unique class of topoisomerase II inhibitors that lock topoisomerase II at a point in the enzyme reaction cycle where the enzyme forms a closed clamp around DNA. We examined cell killing by ICRF-187 and ICRF-193 in yeast cells expressing human topoisomerase II alpha (htop-IIalpha). Expression of htop-IIalpha in yeast cells sensitizes them to both ICRF-187 and ICRF-193, compared with cells expressing yeast topoisomerase II. ICRF-193 is still able to exert growth inhibition in the presence of genes encoding both ICRF-193-resistant and ICRF-193-sensitive htop-IIalpha enzymes, indicating that sensitivity to bisdioxopiperazines is dominant. Killing by ICRF-193 occurs more rapidly, than the killing in yeast cells due to a temperature-sensitive yeast topoisomerase II incubated at the non-permissive temperature. These results are reminiscent of a top-II poison such as etoposide. However, the killing caused by ICRF-193 and ICRF-187 is not enhanced by mutations in the RAD52 pathway. The levels of drug-induced DNA cleavage observed with htop-IIalpha in vitro is insufficient to explain the sensitivity induced by this enzyme in yeast cells. Finally, arrest of cells in G(1) does not protect cells from ICRF-193 lethality, a result inconsistent with killing mechanisms due to catalytic inhibition of top-II or stabilization of a cleavable complex. We suggest that the observed pattern of cell killing is most consistent with a poisoning of htop-II by ICRF-193 by a novel mechanism. The accumulation of closed clamp conformations of htop-II induced by ICRF-193 that are trapped on DNA might interfere with transcription, or other DNA metabolic processes, resulting in cell death.

MeSH Terms (18)

Alleles Antineoplastic Agents Cell Cycle DNA Topoisomerases, Type II Dose-Response Relationship, Drug Drug Resistance, Microbial Enzyme Inhibitors Genes, Dominant Humans Microbial Sensitivity Tests Mutagenesis Piperazines Protein Conformation Razoxane Saccharomyces cerevisiae Time Factors Topoisomerase II Inhibitors Ultracentrifugation

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