ATR safeguards replication forks against APOBEC3B-induced toxic PARP1 trapping DOI Creative Commons
Pedro Ortega, Elodie Bournique, Junyi Li

et al.

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 15, 2024

ATR is the master safeguard of genomic integrity during DNA replication. Acute inhibition with inhibitor (ATRi) triggers a surge in origin firing, leading to increased levels single-stranded (ssDNA) that rapidly deplete all available RPA. This leaves ssDNA unprotected and susceptible breakage, phenomenon known as replication catastrophe. However, mechanism by which breaks remains unclear. Here, we reveal APOBEC3B key enzyme targeting at forks, triggering reaction cascade induces fork collapse PARP1 hyperactivation. Mechanistically, demonstrate uracils generated forks are removed UNG2, creating abasic sites subsequently cleaved APE1 endonuclease. Moreover, APE1-mediated cleavage critical enzymatic step for trapping hyperactivation cells, regardless how on DNA. Finally, show APOBEC3B-induced toxic response ATRi drives cell sensitivity inhibition, context synthetic lethality when combined PARP inhibitors. Together, these findings mechanisms cause break catastrophe explain why ATRi-treated cells particularly sensitive

Language: Английский

APOBEC3A deaminates CTG hairpin loops to promote fragility and instability of expanded CAG/CTG repeats DOI Creative Commons
Rebecca E. Brown,

Margo Coxon,

Bianca Larsen

et al.

Proceedings of the National Academy of Sciences, Journal Year: 2025, Volume and Issue: 122(2)

Published: Jan. 7, 2025

CAG/CTG repeats are prone to expansion, causing several inherited human diseases. The initiating sources of DNA damage which lead inaccurate repair the repeat tract cause expansions not fully understood. Expansion-prone actively transcribed and forming stable R-loops with hairpin structures on displaced single-stranded (S-loops). We previously determined that by Saccharomyces cerevisiae cytosine deaminase, Fcy1, was required for both fragility instability tracts engaged in R-loops. To determine whether this mechanism is more universal, we expressed cytidine deaminases APOBEC3A (A3A), APOBEC3B (A3B), or activation-induced deaminase (AID) our yeast system. show mutagenic activity Apolipoprotein B messenger RNA-editing enzyme, catalytic polypeptides causes instability, A3A having greatest effect followed A3B least from AID. A3A-induced exacerbated enrichment at site. A3B-induced dependent MutLγ nuclease a lesser extent, base excision factors. Deaminase assays substrates containing CTG GTC triplet sequences revealed prefers cytidines within loop, bulges stem alter preferred locations. Analysis RNA expression levels cortex samples brain tissue exhibits its elevated Huntington’s disease (HD) patient samples. These results implicate deamination as potential source HD other expansion disorders.

Language: Английский

Citations

2
Unprocessed genomic uracil as a source of DNA replication stress in cancer cells DOI
Sneha Saxena, Christopher S. Nabel, Turner W. Seay

et al.

Molecular Cell, Journal Year: 2024, Volume and Issue: 84(11), P. 2036 - 2052.e7

Published: April 29, 2024

Language: Английский

Citations

15
BRCAness, DNA gaps, and gain and loss of PARP inhibitor–induced synthetic lethality DOI Creative Commons
Xin Li, Lee Zou

Journal of Clinical Investigation, Journal Year: 2024, Volume and Issue: 134(14)

Published: July 14, 2024

Mutations in the tumor-suppressor genes BRCA1 and BRCA2 resulting BRCA1/2 deficiency are frequently identified breast, ovarian, prostate, pancreatic, other cancers. Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPis) selectively kill BRCA1/2-deficient cancer cells by inducing synthetic lethality, providing an effective biomarker-guided strategy for targeted therapy. However, a substantial fraction of patients carrying mutations do not respond to PARPis, most develop resistance PARPis over time, highlighting major obstacle PARPi therapy clinic. Recent studies have revealed that changes specific functional defects cells, particularly their suppressing protecting single-stranded DNA gaps, contribute gain or loss PARPi-induced lethality. These findings only shed light on mechanism action but also lead revised models explain how BRCA-deficient cells. Furthermore, new mechanistic principles sensitivity emerged from these studies, generating potentially useful guidelines predicting response design therapies overcoming resistance. In this Review, we will discuss recent put them context with classic views aiming stimulate development therapeutic strategies overcome improve

Language: Английский

Citations

13
The SMC5/6 complex prevents genotoxicity upon APOBEC3A-mediated replication stress DOI Creative Commons

Dylan Fingerman,

David O’Leary,

Ava R Hansen

et al.

The EMBO Journal, Journal Year: 2024, Volume and Issue: 43(15), P. 3240 - 3255

Published: June 17, 2024

Abstract Mutational patterns caused by APOBEC3 cytidine deaminase activity are evident throughout human cancer genomes. In particular, the APOBEC3A family member is a potent genotoxin that causes substantial DNA damage in experimental systems and tumors. However, mechanisms ensure genome stability cells with active unknown. Through an unbiased genome-wide screen, we define Structural Maintenance of Chromosomes 5/6 (SMC5/6) complex as essential for cell viability when active. We observe absence mutagenesis tumors SMC5/6 dysfunction, consistent synthetic lethality. Cancer depleted incur from during replication. Further, results replication tract lengthening which dependent on PrimPol, re-initiation synthesis downstream APOBEC3A-induced lesions. Loss abrogates elongated tracts increases breaks upon activity. Our findings indicate fork reflects response to promotes SMC5/6-dependent manner. Therefore, presents potential therapeutic vulnerability APOBEC3A.

Language: Английский

Citations

5
Nucleolytic processing of abasic sites underlies PARP inhibitor hypersensitivity in ALC1-deficient BRCA mutant cancer cells DOI Creative Commons
Natasha Ramakrishnan, Tyler Weaver,

Lindsey N Aubuchon

et al.

Nature Communications, Journal Year: 2024, Volume and Issue: 15(1)

Published: July 27, 2024

Clinical success with poly (ADP-ribose) polymerase inhibitors (PARPi) is impeded by inevitable resistance and associated cytotoxicity. Depletion of Amplified in Liver Cancer 1 (ALC1), a chromatin-remodeling enzyme, can overcome these limitations hypersensitizing BReast CAncer genes 1/2 (BRCA1/2) mutant cells to PARPi. Here, we demonstrate that PARPi hypersensitivity upon ALC1 loss reliant on its role promoting the repair chromatin buried abasic sites. We show enhances ability site processing Apurinic/Apyrimidinic endonuclease (APE1) cleave nucleosome-occluded However, unrepaired sites ALC1-deficient are readily accessed APE1 at nucleosome-free replication forks. cleavage leads fork breakage trapping PARP1/2 treatment, resulting hypersensitivity. Collectively, our studies reveal how barrier lesions uncover as mechanism Loss (ALC1) has been shown confer PARP inhibitor BRCA-mutant cells. authors cells, cleaves forks DNA breaks thereby sensitivity.

Language: Английский

Citations

5
Mechanisms and regulation of DNA end resection in the maintenance of genome stability DOI
Raphaël Ceccaldi, Petr Ćejka

Nature Reviews Molecular Cell Biology, Journal Year: 2025, Volume and Issue: unknown

Published: March 25, 2025

Language: Английский

Citations

0
Mechanism of DNA replication fork breakage and PARP1 hyperactivation during replication catastrophe DOI Creative Commons
Pedro Ortega, Elodie Bournique,

Junyi Li

et al.

Science Advances, Journal Year: 2025, Volume and Issue: 11(16)

Published: April 16, 2025

Ataxia telangiectasia and Rad3-related (ATR) inhibition triggers a surge in origin firing, resulting increased levels of single-stranded DNA (ssDNA) that rapidly deplete all available RPA. This leaves ssDNA unprotected susceptible to breakage, phenomenon known as replication catastrophe. However, the mechanism by which breaks remains unclear. Here, we reveal APOBEC3B is key enzyme targeting at forks, initiating reaction cascade induces fork collapse poly(ADP-ribose) polymerase 1 (PARP1) hyperactivation. Mechanistically, demonstrate uracils generated forks are removed UNG2, abasic sites subsequently cleaved APE1 endonuclease. Moreover, show APE1-mediated cleavage critical enzymatic step for PARP1 hyperactivation cells, regardless how on DNA. Last, APOBEC3B-induced trapping double-strand drive cell sensitivity ATR inhibition, creating context synthetic lethality when coupled with PARP inhibitors.

Language: Английский

Citations

0
Loss of POLE3-POLE4 unleashes replicative gap accumulation upon treatment with PARP inhibitors DOI Creative Commons

Bethany Rebekah Hill,

Meryem Ozgencil,

Lauryn Buckley-Benbow

et al.

Cell Reports, Journal Year: 2024, Volume and Issue: 43(5), P. 114205 - 114205

Published: May 1, 2024

The advent of PARP inhibitors (PARPis) has profoundly changed the treatment landscape BRCA1/BRCA2-mutated cancers. Despite this, development resistance to these compounds become a major challenge. Hence, detailed understanding mechanisms underlying PARPi sensitivity is crucially needed. Here, we show that loss POLE3-POLE4 subunits DNA polymerase epsilon (Polε) strongly sensitizes cancer cells PARPis in Polε level-independent manner. Loss not associated with defective RAD51 foci formation, excluding defect homologous recombination. On contrary, triggers replicative gap accumulation knockout (KO) PRIMPOL-dependent In addition further BRCA1-silenced PARPis. Importantly, knockdown 53BP1 does rescue KO cells, bypassing common mechanism and outlining potential strategy sensitize

Language: Английский

Citations

2
APOBEC3 upregulation drives gemcitabine resistance DOI
John Maciejowski,

Taha Mohamed

Nature Cancer, Journal Year: 2024, Volume and Issue: 5(6), P. 818 - 820

Published: May 22, 2024

Language: Английский

Citations

2
Regulation, Functional Impact, and Therapeutic Targeting of APOBEC3A in Cancer DOI
Ajinkya S. Kawale, Lee Zou

DNA repair, Journal Year: 2024, Volume and Issue: 141, P. 103734 - 103734

Published: July 20, 2024

Language: Английский

Citations

2