Suppressing proteasome mediated processing of topoisomerase II DNA-protein complexes preserves genome integrity

• Published in: eLife Vol. 9
• Main Authors: Sciascia, Nicholas, Wu, Wei, Zong, Dali, Sun, Yilun, Wong, Nancy, John, Sam, Wangsa, Darawalee, Ried, Thomas, Bunting, Samuel F, Pommier, Yves, Nussenzweig, André
• Format: Journal Article
• Language: English
• Published: England eLife Science Publications, Ltd 14.02.2020; eLife Sciences Publications Ltd; eLife Sciences Publications, Ltd
• Subjects: Animal experimentation; Animals; Cancer; Cancer cells; Cell cycle; Cell viability; Chemotherapy; Combination drug therapy; Deoxyribonucleic acid; DNA; DNA - metabolism; DNA Damage; DNA Repair; DNA topoisomerase (ATP-hydrolysing); DNA Topoisomerases, Type II - metabolism; Double-strand break repair; Drugs; Enzymes; Etoposide; Genetic research; Genetics and Genomics; Genome - genetics; genome instability; Genomes; Genomic instability; Genomics; Health aspects; Humans; Identity; Lymphocytes B; Mice, Inbred C57BL; Proteasome Endopeptidase Complex - metabolism; Proteasome inhibitors; Proteins; Proteolysis; Spleen; Stress management; topoisomerases; California; mouse; genetics; genome instability; DNA damage; genomics; cancer; topoisomerases; DNA repair; human
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/elife.53447

Topoisomerase II (TOP2) relieves topological stress in DNA by introducing double-strand breaks (DSBs) via a transient, covalently linked TOP2 DNA-protein intermediate, termed TOP2 cleavage complex (TOP2cc). TOP2ccs are normally rapidly reversible, but can be stabilized by TOP2 poisons, such as the chemotherapeutic agent etoposide (ETO). TOP2 poisons have shown significant variability in their therapeutic effectiveness across different cancers for reasons that remain to be determined. One potential explanation for the differential cellular response to these drugs is in the manner by which cells process TOP2ccs. Cells are thought to remove TOP2ccs primarily by proteolytic degradation followed by DNA DSB repair. Here, we show that proteasome-mediated repair of TOP2cc is highly error-prone. Pre-treating primary splenic mouse B-cells with proteasome inhibitors prevented the proteolytic processing of trapped TOP2ccs, suppressed the DNA damage response (DDR) and completely protected cells from ETO-induced genome instability, thereby preserving cellular viability. When degradation of TOP2cc was suppressed, the TOP2 enzyme uncoupled itself from the DNA following ETO washout, in an error-free manner. This suggests a potential mechanism of developing resistance to topoisomerase poisons by ensuring rapid TOP2cc reversal.