scholarly journals RB Regulates DNA Double Strand Break Repair Pathway Choice by Mediating CtIP Dependent End Resection

2020 ◽  
Vol 21 (23) ◽  
pp. 9176
Author(s):  
Yuning Jiang ◽  
Jason C. Yam ◽  
Clement C. Tham ◽  
Chi Pui Pang ◽  
Wai Kit Chu
Keyword(s):  
Genome Instability ◽  
Synthetic Lethality ◽  
Strand Break ◽  
Suppressor Gene ◽  
Repair Pathway ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Pathway Choice ◽  
End Resection

Inactivation of the retinoblastoma tumor suppressor gene (RB1) leads to genome instability, and can be detected in retinoblastoma and other cancers. One damaging effect is causing DNA double strand breaks (DSB), which, however, can be repaired by homologous recombination (HR), classical non-homologous end joining (C-NHEJ), and micro-homology mediated end joining (MMEJ). We aimed to study the mechanistic roles of RB in regulating multiple DSB repair pathways. Here we show that HR and C-NHEJ are decreased, but MMEJ is elevated in RB-depleted cells. After inducing DSB by camptothecin, RB co-localizes with CtIP, which regulates DSB end resection. RB depletion leads to less RPA and native BrdU foci, which implies less end resection. In RB-depleted cells, less CtIP foci, and a lack of phosphorylation on CtIP Thr847, are observed. According to the synthetic lethality principle, based on the altered DSB repair pathway choice, after inducing DSBs by camptothecin, RB depleted cells are more sensitive to co-treatment with camptothecin and MMEJ blocker poly-ADP ribose polymerase 1 (PARP1) inhibitor. We propose a model whereby RB can regulate DSB repair pathway choice by mediating the CtIP dependent DNA end resection. The use of PARP1 inhibitor could potentially improve treatment outcomes for RB-deficient cancers.

scholarly journals A role for the p53 tumour suppressor in regulating the balance between homologous recombination and non-homologous end joining

Open Biology ◽  
2016 ◽  
Vol 6 (9) ◽  
pp. 160225 ◽  
Author(s):  
Sylvie Moureau ◽  
Janna Luessing ◽  
Emma Christina Harte ◽  
Muriel Voisin ◽  
Noel Francis Lowndes
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Tumour Suppressor ◽  
Cycle Phase ◽  
Repair Pathway ◽  
End Joining ◽  
Dsb Repair ◽  
Pathway Choice ◽  
Non Homologous End Joining ◽  
End Resection

Loss of p53, a transcription factor activated by cellular stress, is a frequent event in cancer. The role of p53 in tumour suppression is largely attributed to cell fate decisions. Here, we provide evidence supporting a novel role for p53 in the regulation of DNA double-strand break (DSB) repair pathway choice. 53BP1, another tumour suppressor, was initially identified as p53 Binding Protein 1, and has been shown to inhibit DNA end resection, thereby stimulating non-homologous end joining (NHEJ). Yet another tumour suppressor, BRCA1, reciprocally promotes end resection and homologous recombination (HR). Here, we show that in both human and mouse cells, the absence of p53 results in impaired 53BP1 focal recruitment to sites of DNA damage induced by ionizing radiation. This effect is largely independent of cell cycle phase and the extent of DNA damage. In p53-deficient cells, diminished localization of 53BP1 is accompanied by a reciprocal increase in BRCA1 recruitment to DSBs. Consistent with these findings, we demonstrate that DSB repair via NHEJ is abrogated, while repair via homology-directed repair (HDR) is stimulated. Overall, we propose that in addition to its role as an ‘effector’ protein in the DNA damage response, p53 plays a role in the regulation of DSB repair pathway choice.

scholarly journals Multifunctional properties of Nej1XLF C-terminus promote end-joining and impact DNA double-strand break repair pathway choice

2022 ◽  
Author(s):  
Aditya Mojumdar ◽  
Nancy Adam ◽  
Jennifer A Cobb
Keyword(s):  
Strand Break ◽  
Double Strand Break ◽  
Repair Pathway ◽  
End Joining ◽  
C Terminus ◽  
Dna Double Strand Break ◽  
Canonical Pathways ◽  
Pathway Choice ◽  
Non Homologous End Joining ◽  
End Resection

A DNA double strand break (DSB) is primarily repaired by one of two canonical pathways, non-homologous end-joining (NHEJ) and homologous recombination (HR). NHEJ requires no or minimal end processing for ligation, whereas HR requires 5 end resection followed by a search for homology. The main event that determines the mode of repair is the initiation of 5 resection because if resection starts, then NHEJ cannot occur. Nej1 is a canonical NHEJ factor that functions at the cross-roads of repair pathway choice and prior to its function in stimulating Dnl4 ligase. Nej1 competes with Dna2, inhibiting its recruitment to DSBs and thereby inhibiting resection. The highly conserved C-terminal region (CTR) of Nej1 (330- 338) is important for two events that drive NHEJ, stimulating ligation and inhibiting resection, but it is dispensable for end-bridging. By combining nej1 point mutants with nuclease-dead dna2-1, we find that Nej1-F335 is essential for end-joining whereas V338 promotes NHEJ indirectly through inhibiting Dna2-mediated resection.

scholarly journals MSH2-MSH3 promotes DNA end resection during HR and blocks TMEJ through interaction with SMARCAD1 and EXO1

2021 ◽  
Author(s):  
Jung-Min Oh ◽  
Yujin Kang ◽  
Jumi Park ◽  
Yubin Sung ◽  
Dayoung Kim ◽  
...  
Keyword(s):  
Strand Break ◽  
Repair Pathway ◽  
End Joining ◽  
Dsb Repair ◽  
Direct Role ◽  
Dna Double Strand Break ◽  
Dna End Resection ◽  
Template Dna ◽  
End Resection

SUMMARYDNA double strand break (DSB) repair by Homologous recombination (HR) is initiated by the end resection, a process during which 3’ ssDNA overhangs are generated by the nucleolytic degradation. The extent of DNA end resection determines the choice of the DSB repair pathway. The role of several proteins including nucleases for end resection has been studied in detail. However, it is still unclear how the initial, nicked DNA generated by MRE11-RAD50-NBS1 is recognized and how subsequent proteins including EXO1 are recruited to DSB sites to facilitate extensive end resection. We found that the MutSβ (MSH2-MSH3) mismatch repair (MMR) complex is recruited to DSB sites by recognizing the initial nicked DNA at DSB sites through the interaction with the chromatin remodeling protein SMARCAD1. MSH2-MSH3 at DSB sites helps to recruit EXO1 for long-range resection and enhances its enzymatic activity. MSH2-MSH3 furthermore inhibits the access of DNA polymerase θ (POLQ), which promotes polymerase theta-mediated end-joining (TMEJ) of DSB. Collectively, our data show a direct role for MSH2-MSH3 in the initial stages of DSB repair by promoting end resection and influencing DSB repair pathway by favoring HR over TMEJ. Our findings extend the importance of MMR in DSB repair beyond established role in rejecting the invasion of sequences not perfectly homologous to template DNA during late-stage HR.

scholarly journals The (Lack of) DNA Double-Strand Break Repair Pathway Choice During V(D)J Recombination

2022 ◽  
Vol 12 ◽  
Author(s):  
Alice Libri ◽  
Timea Marton ◽  
Ludovic Deriano
Keyword(s):  
Dna Repair ◽  
Gene Diversity ◽  
Receptor Gene ◽  
Strand Break ◽  
Repair Pathway ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Homology Directed Repair ◽  
Pathway Choice ◽  
Non Homologous End Joining

DNA double-strand breaks (DSBs) are highly toxic lesions that can be mended via several DNA repair pathways. Multiple factors can influence the choice and the restrictiveness of repair towards a given pathway in order to warrant the maintenance of genome integrity. During V(D)J recombination, RAG-induced DSBs are (almost) exclusively repaired by the non-homologous end-joining (NHEJ) pathway for the benefit of antigen receptor gene diversity. Here, we review the various parameters that constrain repair of RAG-generated DSBs to NHEJ, including the peculiarity of DNA DSB ends generated by the RAG nuclease, the establishment and maintenance of a post-cleavage synaptic complex, and the protection of DNA ends against resection and (micro)homology-directed repair. In this physiological context, we highlight that certain DSBs have limited DNA repair pathway choice options.

scholarly journals Regulatory and Functional Involvement of Long Non-Coding RNAs in DNA Double-Strand Break Repair Mechanisms

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1506
Author(s):  
Angelos Papaspyropoulos ◽  
Nefeli Lagopati ◽  
Ioanna Mourkioti ◽  
Andriani Angelopoulou ◽  
Spyridon Kyriazis ◽  
...  
Keyword(s):  
Therapeutic Potential ◽  
Strand Break ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Repair Mechanisms ◽  
Non Coding Rnas ◽  
Repair Pathways ◽  
Non Homologous End Joining ◽  
Living Organisms

Protection of genome integrity is vital for all living organisms, particularly when DNA double-strand breaks (DSBs) occur. Eukaryotes have developed two main pathways, namely Non-Homologous End Joining (NHEJ) and Homologous Recombination (HR), to repair DSBs. While most of the current research is focused on the role of key protein players in the functional regulation of DSB repair pathways, accumulating evidence has uncovered a novel class of regulating factors termed non-coding RNAs. Non-coding RNAs have been found to hold a pivotal role in the activation of DSB repair mechanisms, thereby safeguarding genomic stability. In particular, long non-coding RNAs (lncRNAs) have begun to emerge as new players with vast therapeutic potential. This review summarizes important advances in the field of lncRNAs, including characterization of recently identified lncRNAs, and their implication in DSB repair pathways in the context of tumorigenesis.

scholarly journals RAP80 suppresses the vulnerability of R-loops during DNA double-strand break repair

2021 ◽  
Author(s):  
Takaaki Yasuhara ◽  
Reona Kato ◽  
Motohiro Yamauchi ◽  
Yuki Uchihara ◽  
Lee Zou ◽  
...  
Keyword(s):  
Active Regions ◽  
Strand Break ◽  
Double Strand Breaks ◽  
Critical Component ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Strand Breaks ◽  
Chromosome Translocations ◽  
Dna Double Strand Break

AbstractR-loops, consisting of ssDNA and DNA-RNA hybrids, are potentially vulnerable unless they are appropriately processed. Recent evidence suggests that R-loops can form in the proximity of DNA double-strand breaks (DSBs) within transcriptionally active regions. Yet, how the vulnerability of R-loops is overcome during DSB repair remains unclear. Here, we identify RAP80 as a factor suppressing the vulnerability of ssDNA in R-loops and chromosome translocations and deletions during DSB repair. Mechanistically, RAP80 prevents unscheduled nucleolytic processing of ssDNA in R-loops by CtIP. This mechanism promotes efficient DSB repair via transcription-associated end-joining dependent on BRCA1, Polθ, and LIG1/3. Thus, RAP80 suppresses the vulnerability of R-loops during DSB repair, thereby precluding genomic abnormalities in a critical component of the genome caused by deleterious R-loop processing.

scholarly journals The Dystonia Gene THAP1 Controls DNA Double Strand Break Repair Choice

2020 ◽  
Author(s):  
Kenta Shinoda ◽  
Dali Zong ◽  
Elsa Callen ◽  
Wei Wu ◽  
Lavinia C. Dumitrache ◽  
...  
Keyword(s):  
Dna Damage ◽  
Genome Instability ◽  
Parp Inhibitor ◽  
Progression Free Survival ◽  
Strand Break ◽  
Transcriptional Network ◽  
Cross Resistance ◽  
Dna Double Strand Breaks ◽  
Dsb Repair ◽  
Protein Levels

AbstractThe Shieldin complex, consisting of SHLD1, SHLD2, SHLD3 and REV7, shields DNA double strand breaks (DSBs) from nucleolytic resection. The end-protecting activity of Shieldin promotes productive non-homologous end joining (NHEJ) in G1 but can threaten genome integrity during S-phase by blocking homologous recombination (HR). Curiously, the penultimate Shieldin component, SHLD1 is one of the least abundant mammalian proteins. Here, we report that the transcription factors THAP1, YY1 and HCF1 bind directly to the SHLD1 promoter, where they cooperatively maintain the low basal expression of SHLD1. Functionally, this transcriptional network ensures that SHLD1 protein levels are kept in check to enable a proper balance between end protection and end resection during physiological DSB repair. In the context of BRCA1 deficiency, loss of THAP1 dependent SHLD1 expression confers cross resistance to PARP inhibitor and cisplatin, and shorter progression free survival in ovarian cancer patients. In contrast, loss of THAP1 in BRCA2 deficient cells increases genome instability and correlates with improved responses to chemotherapy. Pathogenic THAP1 mutations are causatively linked to the adult-onset torsion dystonia type 6 (DYT6) movement disorder, but the critical disease targets are unknown. We further demonstrate that murine models of Thap1-associated dystonia show reduced Shld1 expression concomitant with elevated levels of unresolved DNA damage in the brain. In summary, our study provides the first example of a transcriptional network that directly controls DSB repair choice and reveals a previously unsuspected link between DNA damage and dystonia.

scholarly journals Histone chaperone Anp32e removes H2A.Z from DNA double-strand breaks and promotes nucleosome reorganization and DNA repair

2015 ◽  
Vol 112 (24) ◽  
pp. 7507-7512 ◽  
Author(s):  
Ozge Gursoy-Yuzugullu ◽  
Marina K. Ayrapetov ◽  
Brendan D. Price
Keyword(s):  
Dna Damage ◽  
Double Strand Breaks ◽  
Histone H4 ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Strand Breaks ◽  
Nucleosome Dynamics ◽  
Chromatin Template ◽  
End Resection

The repair of DNA double-strand breaks (DSBs) requires open, flexible chromatin domains. The NuA4–Tip60 complex creates these flexible chromatin structures by exchanging histone H2A.Z onto nucleosomes and promoting acetylation of histone H4. Here, we demonstrate that the accumulation of H2A.Z on nucleosomes at DSBs is transient, and that rapid eviction of H2A.Z is required for DSB repair. Anp32e, an H2A.Z chaperone that interacts with the C-terminal docking domain of H2A.Z, is rapidly recruited to DSBs. Anp32e functions to remove H2A.Z from nucleosomes, so that H2A.Z levels return to basal within 10 min of DNA damage. Further, H2A.Z removal by Anp32e disrupts inhibitory interactions between the histone H4 tail and the nucleosome surface, facilitating increased acetylation of histone H4 following DNA damage. When H2A.Z removal by Anp32e is blocked, nucleosomes at DSBs retain elevated levels of H2A.Z, and assume a more stable, hypoacetylated conformation. Further, loss of Anp32e leads to increased CtIP-dependent end resection, accumulation of single-stranded DNA, and an increase in repair by the alternative nonhomologous end joining pathway. Exchange of H2A.Z onto the chromatin and subsequent rapid removal by Anp32e are therefore critical for creating open, acetylated nucleosome structures and for controlling end resection by CtIP. Dynamic modulation of H2A.Z exchange and removal by Anp32e reveals the importance of the nucleosome surface and nucleosome dynamics in processing the damaged chromatin template during DSB repair.

scholarly journals cGAS guards against chromosome end-to-end fusions during mitosis and facilitates replicative senescence

2021 ◽  
Author(s):  
Xiaocui Li ◽  
Xiaojuan Li ◽  
Chen Xie ◽  
Sihui Cai ◽  
Mengqiu Li ◽  
...  
Keyword(s):  
Genome Stability ◽  
Mitotic Chromosome ◽  
Replicative Senescence ◽  
Genome Instability ◽  
Strand Break ◽  
End Joining ◽  
Dsb Repair ◽  
End To End ◽  
Non Homologous End Joining ◽  
Sting Pathway

AbstractAs a sensor of cytosolic DNA, the role of cyclic GMP-AMP synthase (cGAS) in innate immune response is well established, yet how its functions in different biological conditions remain to be elucidated. Here, we identify cGAS as an essential regulator in inhibiting mitotic DNA double-strand break (DSB) repair and protecting short telomeres from end-to-end fusion independent of the canonical cGAS-STING pathway. cGAS associates with telomeric/subtelomeric DNA during mitosis when TRF1/TRF2/POT1 are deficient on telomeres. Depletion of cGAS leads to mitotic chromosome end-to-end fusions predominantly occurring between short telomeres. Mechanistically, cGAS interacts with CDK1 and positions them to chromosome ends. Thus, CDK1 inhibits mitotic non-homologous end joining (NHEJ) by blocking the recruitment of RNF8. cGAS-deficient human primary cells are defective in entering replicative senescence and display chromosome end-to-end fusions, genome instability and prolonged growth arrest. Altogether, cGAS safeguards genome stability by controlling mitotic DSB repair to inhibit mitotic chromosome end-to-end fusions, thus facilitating replicative senescence.

scholarly journals Nucleosome disassembly during human non-homologous end joining followed by concerted HIRA- and CAF-1-dependent reassembly

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Xuan Li ◽  
Jessica K Tyler
Keyword(s):  
Strand Break ◽  
End Joining ◽  
Efficient Removal ◽  
Dsb Repair ◽  
Dna Double Strand Break ◽  
Dna End Resection ◽  
Non Homologous End Joining ◽  
Nucleosome Disassembly ◽  
End Resection ◽  
Assembly Pathways

The cell achieves DNA double-strand break (DSB) repair in the context of chromatin structure. However, the mechanisms used to expose DSBs to the repair machinery and to restore the chromatin organization after repair remain elusive. Here we show that induction of a DSB in human cells causes local nucleosome disassembly, apparently independently from DNA end resection. This efficient removal of histone H3 from the genome during non-homologous end joining was promoted by both ATM and the ATP-dependent nucleosome remodeler INO80. Chromatin reassembly during DSB repair was dependent on the HIRA histone chaperone that is specific to the replication-independent histone variant H3.3 and on CAF-1 that is specific to the replication-dependent canonical histones H3.1/H3.2. Our data suggest that the epigenetic information is re-established after DSB repair by the concerted and interdependent action of replication-independent and replication-dependent chromatin assembly pathways.

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