scholarly journals Transcription-associated topoisomerase 2α activity is a major effector of cytotoxicity induced by G-quadruplex ligands

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Madeleine Bossaert ◽  
Angélique Pipier ◽  
Jean-Francois Riou ◽  
Céline Noirot ◽  
Linh-Trang Nguyễn ◽  
...  
Keyword(s):  
Small Molecules ◽  
Double Strand Breaks ◽  
Transcriptional Elongation ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Dna Structures ◽  
Topoisomerase 1 ◽  
G Quadruplex ◽  
Topoisomerase 2 ◽  
Topoisomerase 2 Alpha

G-quadruplexes (G4) are non-canonical DNA structures found in the genome of most species including human. Small molecules stabilizing these structures, called G4 ligands, have been identified and, for some of them, shown to induce cytotoxic DNA double-strand breaks. Through the use of an unbiased genetic approach, we identify here topoisomerase 2-alpha (TOP2A) as a major effector of cytotoxicity induced by two clastogenic G4 ligands, pyridostatin and CX-5461, the latter molecule currently undergoing phase I/II clinical trials in oncology. We show that both TOP2 activity and transcription account for DNA break production following G4 ligand treatments. In contrast, clastogenic activity of these G4 ligands is countered by topoisomerase 1 (TOP1), which limits co-transcriptional G4 formation, and by factors promoting transcriptional elongation. Altogether our results support that clastogenic G4 ligands act as DNA structure-driven TOP2-poisons at transcribed regions bearing G4 structures.

scholarly journals Spatial chromosome folding and active transcription drive DNA fragility and formation of oncogenic MLL translocations

2018 ◽  
Author(s):  
Henrike Johanna Gothe ◽  
Britta Annika Maria Bouwman ◽  
Eduardo Gade Gusmao ◽  
Rossana Piccinno ◽  
Sergi Sayols ◽  
...  
Keyword(s):  
Hot Spots ◽  
Double Strand Breaks ◽  
Genome Integrity ◽  
Transcriptional Elongation ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Physiological Relevance ◽  
Topoisomerase 2 ◽  
Active Transcription ◽  
Transcriptional Output

How spatial chromosome organization influences genome integrity is still poorly understood. Here we show that DNA double-strand breaks (DSBs) mediated by topoisomerase 2 (TOP2) activities, are enriched at chromatin loop anchors with high transcriptional activity. Recurrent DSBs occur at CTCF/cohesin bound sites at the bases of chromatin loops and their frequency positively correlates with transcriptional output and directionality. The physiological relevance of this preferential positioning is indicated by the finding that genes recurrently translocating to drive leukemias, are highly transcribed and are enriched at loop anchors. These genes accumulate DSBs at recurrent hot spots that give rise to chromosomal fusions relying on the activity of both TOP2 isoforms and on transcriptional elongation. We propose that transcription and 3D chromosome folding jointly pose a threat to genomic stability, and are key contributors to the occurrence of genome rearrangements that drive cancer.

scholarly journals Transcription-associated topoisomerase activities control DNA-breaks production by G-quadruplex ligands

2020 ◽  
Author(s):  
A. Pipier ◽  
M. Bossaert ◽  
J.F. Riou ◽  
C. Noirot ◽  
L-T. Nguyễn ◽  
...  
Keyword(s):  
Point Mutations ◽  
Telomere Maintenance ◽  
Cross Resistance ◽  
Cell Cytotoxicity ◽  
Dna Breaks ◽  
Topoisomerase 1 ◽  
G Quadruplex ◽  
Topoisomerase 2 ◽  
Topoisomerase 2 Alpha ◽  
Almost All

AbstractG-quadruplexes (G4), non-canonical DNA structures, are involved in several essential processes. Stabilization of G4 structures by small compounds (G4 ligands) affects almost all DNA transactions, including telomere maintenance and genomic stability. Here, thanks to a powerful and unbiased genetic approach, we identify topoisomerase 2-alpha (TOP2A) as the main effector of cell cytotoxicity induced by CX5461, a G4 ligand currently undergoing phase I/II clinical trials. This approach also allowed to identify new point mutations affecting TOP2A activity without compromising cell viability. Moreover, based on cross-resistance studies and siRNA-based protein depletion we report that TOP2A plays a major role in cell cytotoxicity induced by two unrelated clastogenic G4 ligands, CX5461 and pyridostatin (PDS). We also report that cytotoxic effects induced by both compounds are associated with topoisomerase 2-mediated DNA breaks production. Finally, we show that TOP2-mediated DNA breaks production is strongly associated with RNA Pol II-dependent transcription and is countered by topoisomerase 1 (TOP1). Altogether our results indicate that clastogenic G4 ligands act as DNA structure-driven TOP2-poisons at transcribed regions bearing G-quadruplex structures.

scholarly journals Probing the Potential Role of Non-B DNA Structures at Yeast Meiosis-Specific DNA Double-Strand Breaks

2017 ◽  
Vol 112 (10) ◽  
pp. 2056-2074 ◽  
Author(s):  
Rucha Kshirsagar ◽  
Krishnendu Khan ◽  
Mamata V. Joshi ◽  
Ramakrishna V. Hosur ◽  
K. Muniyappa
Keyword(s):  
Potential Role ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Dna Structures ◽  
Yeast Meiosis

Repair pathway choice for double-strand breaks

2020 ◽  
Vol 64 (5) ◽  
pp. 765-777 ◽  
Author(s):  
Yixi Xu ◽  
Dongyi Xu
Keyword(s):  
Cell Cycle ◽  
Double Strand Breaks ◽  
Homologous Region ◽  
Gene Repair ◽  
Repair Pathway ◽  
Dna Double Strand Breaks ◽  
Environmental Radiation ◽  
Strand Breaks ◽  
Dna End Resection ◽  
End Resection

Abstract Deoxyribonucleic acid (DNA) is at a constant risk of damage from endogenous substances, environmental radiation, and chemical stressors. DNA double-strand breaks (DSBs) pose a significant threat to genomic integrity and cell survival. There are two major pathways for DSB repair: nonhomologous end-joining (NHEJ) and homologous recombination (HR). The extent of DNA end resection, which determines the length of the 3′ single-stranded DNA (ssDNA) overhang, is the primary factor that determines whether repair is carried out via NHEJ or HR. NHEJ, which does not require a 3′ ssDNA tail, occurs throughout the cell cycle. 53BP1 and the cofactors PTIP or RIF1-shieldin protect the broken DNA end, inhibit long-range end resection and thus promote NHEJ. In contrast, HR mainly occurs during the S/G2 phase and requires DNA end processing to create a 3′ tail that can invade a homologous region, ensuring faithful gene repair. BRCA1 and the cofactors CtIP, EXO1, BLM/DNA2, and the MRE11–RAD50–NBS1 (MRN) complex promote DNA end resection and thus HR. DNA resection is influenced by the cell cycle, the chromatin environment, and the complexity of the DNA end break. Herein, we summarize the key factors involved in repair pathway selection for DSBs and discuss recent related publications.

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