scholarly journals Determination of the DNA repair pathways utilised by acute lymphoblastic leukaemia cells following daunorubicin treatment

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Hussain Mubarak Al-Aamri ◽  
Helen R. Irving ◽  
Terri Meehan-Andrews ◽  
Christopher Bradley
Keyword(s):  
Dna Repair ◽  
Homologous Recombination ◽  
Cell Lines ◽  
Dna Lesions ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Histone H2ax ◽  
Repair Pathways ◽  
Non Homologous End Joining

Abstract Objective DNA double strand breaks (DNA-DSBs) are among the most lethal DNA lesions leading to genomic instability and repaired by either homologous recombination (HR) or the non-homologous end joining (NHEJ) mechanisms. The purpose of this study was to assess the importance and the level of activation of non-homologous end joining (NHEJ) and homologous recombination (HR) DNA repair pathways in three cell lines, CCRF-CEM and MOLT-4 derived from T lymphocytes and SUP-B15 derived from B lymphocytes following treatment with chemotherapy agent daunorubicin. Results The Gamma histone H2AX (γH2AX) assay was used assess the effects of DNA-PK inhibitor NU7026 and RAD51 inhibitor RI-2 on repair of DNA-DSB following treatment with daunorubicin. In all cell lines, the NHEJ DNA repair pathway appeared more rapid and efficient. MOLT-4 and CCFR-CEM cells utilised both NHEJ and HR pathways for DNA-DSB repair. Whereas, SUP-B15 cells utilised only NHEJ for DSB repair, suggestive of a deficiency in HR repair pathways.

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.

141 INDICATIONS FOR DNA DOUBLE-STRAND BREAK REPAIR IN EARLY BOVINE EMBRYOS

2007 ◽  
Vol 19 (1) ◽  
pp. 188
Author(s):  
A. Brero ◽  
D. Koehler ◽  
T. Cremer ◽  
E. Wolf ◽  
V. Zakhartchenko
Keyword(s):  
Dna Repair ◽  
Homologous Recombination ◽  
Strand Break ◽  
Dna Lesions ◽  
Homologous Recombination Repair ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Male And Female ◽  
Γh2ax Foci ◽  
Recombination Repair

DNA double-strand breaks (DSBs) are considered the most severe type of DNA lesions, because such lesions, if unrepaired, lead to a loss of genome integrity. Soon after induction of DSBs, chromatin surrounding the damage is modified by phosphorylation of the histone variant H2AX, generating so-called γH2AX, which is a hallmark of DSBs (Takahashi et al. 2005 Cancer Lett. 229, 171–179). γH2AX appears to be a signal for the recruitment of proteins constituting the DNA repair machinery. Depending on the type of damage and the cell cycle stage of the affected cell, DSBs are repaired either by nonhomologous end joining or by homologous recombination using the sister chromatid DNA as template (Hoeijmakers 2001 Nature 411, 366–374). We used immunofluorescence to analyze chromatin composition during bovine development and found γH2AX foci in both male and female pronuclei of IVF embryos. The number and size of foci varied considerably between embryos and between the male and female pronuclei. To test whether the observed γH2AX foci represented sites of active DNA repair, we co-stained IVF zygotes for γH2AX and 3 different proteins involved in homologous recombination repair of DSBs: NBS1 (phosphorylated at amino acid serine 343), 53BP1, and Rad51. We found co-localization of γH2AX foci with phosphorylated NBS1 as well as with Rad51 but did not observe the presence of 53BP1 at γH2AX foci in IVF zygotes. Our finding shows the presence of DSBs in IVF zygotes and suggests the capability of homologous recombination repair. The lack of 53BP1, a component of homologous recombination repair, which usually co-localizes with γH2AX foci at exogenously induced DSBs (Schultz et al. 2000 J. Cell. Biol. 151, 1381–1390) poses the possibility that the mechanism present in early embryos differs substantially from that involved in DNA repair of DSBs in somatic cells.

scholarly journals The Determinant of DNA Repair Pathway Choices in Ionising Radiation-Induced DNA Double-Strand Breaks

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Lei Zhao ◽  
Chengyu Bao ◽  
Yuxuan Shang ◽  
Xinye He ◽  
Chiyuan Ma ◽  
...  
Keyword(s):  
Dna Repair ◽  
Double Strand Breaks ◽  
Ionising Radiation ◽  
Repair Pathway ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Strand Breaks ◽  
Dna Dsbs ◽  
Repair Pathways

Ionising radiation- (IR-) induced DNA double-strand breaks (DSBs) are considered to be the deleterious DNA lesions that pose a serious threat to genomic stability. The major DNA repair pathways, including classical nonhomologous end joining, homologous recombination, single-strand annealing, and alternative end joining, play critical roles in countering and eliciting IR-induced DSBs to ensure genome integrity. If the IR-induced DNA DSBs are not repaired correctly, the residual or incorrectly repaired DSBs can result in genomic instability that is associated with certain human diseases. Although many efforts have been made in investigating the major mechanisms of IR-induced DNA DSB repair, it is still unclear what determines the choices of IR-induced DNA DSB repair pathways. In this review, we discuss how the mechanisms of IR-induced DSB repair pathway choices can operate in irradiated cells. We first briefly describe the main mechanisms of the major DNA DSB repair pathways and the related key repair proteins. Based on our understanding of the characteristics of IR-induced DNA DSBs and the regulatory mechanisms of DSB repair pathways in irradiated cells and recent advances in this field, We then highlight the main factors and associated challenges to determine the IR-induced DSB repair pathway choices. We conclude that the type and distribution of IR-induced DSBs, chromatin state, DNA-end structure, and DNA-end resection are the main determinants of the choice of the IR-induced DNA DSB repair pathway.

scholarly journals Beta Human Papillomavirus 8E6 Attenuates Non-Homologous End Joining by Hindering DNA-PKcs Activity

Cancers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2356
Author(s):  
Changkun Hu ◽  
Taylor Bugbee ◽  
Monica Gamez ◽  
Nicholas A. Wallace
Keyword(s):  
Dna Repair ◽  
Viral Infections ◽  
Dna Lesions ◽  
Human Papillomaviruses ◽  
Molecular Evidence ◽  
Repair Pathway ◽  
End Joining ◽  
Dsb Repair ◽  
Dependent Protein ◽  
Non Homologous End Joining

Cutaneous viral infections occur in a background of near continual exposure to environmental genotoxins, like UV radiation in sunlight. Failure to repair damaged DNA is an established driver of tumorigenesis and substantial cellular resources are devoted to repairing DNA lesions. Beta-human papillomaviruses (β-HPVs) attenuate DNA repair signaling. However, their role in human disease is unclear. Some have proposed that β-HPV promotes tumorigenesis, while others suggest that β-HPV protects against skin cancer. Most of the molecular evidence that β-HPV impairs DNA repair has been gained via characterization of the E6 protein from β-HPV 8 (β-HPV 8E6). Moreover, β-HPV 8E6 hinders DNA repair by binding and destabilizing p300, a transcription factor for multiple DNA repair genes. By reducing p300 availability, β-HPV 8E6 attenuates a major double strand DNA break (DSB) repair pathway, homologous recombination. Here, β-HPV 8E6 impairs another DSB repair pathway, non-homologous end joining (NHEJ). Specifically, β-HPV 8E6 acts by attenuating DNA-dependent protein kinase (DNA-PK) activity, a critical NHEJ kinase. This includes DNA-PK activation and the downstream of steps in the pathway associated with DNA-PK activity. Notably, β-HPV 8E6 inhibits NHEJ through p300 dependent and independent means. Together, these data expand the known genome destabilizing capabilities of β-HPV 8E6.

scholarly journals Cdc14A and Cdc14B Redundantly Regulate DNA Double-Strand Break Repair

2015 ◽  
Vol 35 (21) ◽  
pp. 3657-3668 ◽  
Author(s):  
Han Lin ◽  
Kyungsoo Ha ◽  
Guojun Lu ◽  
Xiao Fang ◽  
Ranran Cheng ◽  
...  
Keyword(s):  
Dna Repair ◽  
Strand Break ◽  
Mitotic Exit ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Downstream Target ◽  
Damage Repair ◽  
Repair Pathways ◽  
Repair Defect

Cdc14 is a phosphatase that controls mitotic exit and cytokinesis in budding yeast. In mammals, the two Cdc14 homologues, Cdc14A and Cdc14B, have been proposed to regulate DNA damage repair, whereas the mitotic exit and cytokinesis rely on another phosphatase, PP2A-B55α. It is unclear if the two Cdc14s work redundantly in DNA repair and which repair pathways they participate in. More importantly, their target(s) in DNA repair remains elusive. Here we report that Cdc14B knockout (Cdc14B−/−) mouse embryonic fibroblasts (MEFs) showed defects in repairing ionizing radiation (IR)-induced DNA double-strand breaks (DSBs), which occurred only at late passages when Cdc14A levels were low. This repair defect could occur at early passages if Cdc14A levels were also compromised. These results indicate redundancy between Cdc14B and Cdc14A in DSB repair. Further, we found that Cdc14B deficiency impaired both homologous recombination (HR) and nonhomologous end joining (NHEJ), the two major DSB repair pathways. We also provide evidence that Cdh1 is a downstream target of Cdc14B in DSB repair.

scholarly journals Genome Instability and Pressure on Non-Homologous end Joining drives Chemotherapy Resistance via a DNA Repair Crisis Switch in Triple Negative Breast Cancer.

2020 ◽  
Author(s):  
Adrian Wiegmans ◽  
Ambber Ward ◽  
Ekaterina Ivanova ◽  
Pascal H G Duijf ◽  
Romy VanOosterhout ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Dna Repair ◽  
Homologous Recombination ◽  
Triple Negative Breast Cancer ◽  
Triple Negative ◽  
Genome Instability ◽  
Chemotherapy Resistance ◽  
End Joining ◽  
Repair Pathways ◽  
Non Homologous End Joining

Abstract Background: Chemotherapy intensifies pressure on the DNA repair pathways that can lead to deregulation. There is an urgent clinical need to be able to track the emergence of chemotherapy resistance and tailor patient staging appropriately. This is especially evident in the triple negative breast cancer (TNBC) subtype, of which standard of care is chemotherapy with tumours displaying high levels of inherent genome instability. TNBC has an overall poor prognosis for survival. There have been numerous studies into single agent chemoresistance but to date no study has elucidated in detail the roles of the key DNA repair components in resistance associated with the frontline clinical combination of anthracyclines and taxanes together. Methods: In this study, we hypothesized that the emergence of chemotherapy resistance is driven by changes in functional signaling in the DNA repair pathways. We identified the importance of the DNA repair pathways in chemoresistant clinical samples and characterized the emergence of chemoresistance in TNBC cell lines. We utilized classical DNA repair assays and specific targeting of key DNA repair proteins to elucidate a new mechanism for adaptation to the combination of doxorubicin and docetaxel. Results: We identified that consistent pressure on the non-homologous end joining pathway in the presence of genome instability causes failure of the key kinase DNA-PK, loss of p53 and compensation by p73. In-turn a switch to reliance on the homologous recombination pathway and RAD51 recombinase occurs to repair residual double strand DNA breaks. Conclusions: We demonstrate that RAD51 is an actionable target for resensitization to chemotherapy in resistant cells with a matched gene expression profile of resistance highlighted by homologous recombination.

scholarly journals Impact of hypoxia on the double-strand break repair after photon and carbon ion irradiation of radioresistant HNSCC cells

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Anne-Sophie Wozny ◽  
Gersende Alphonse ◽  
Audrey Cassard ◽  
Céline Malésys ◽  
Safa Louati ◽  
...  
Keyword(s):  
Dna Repair ◽  
Ion Irradiation ◽  
Strand Break ◽  
Carbon Ions ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Photon Irradiation ◽  
Hypoxic Conditions ◽  
Non Homologous End Joining

AbstractDNA double-strand breaks (DSBs) induced by photon irradiation are the most deleterious damage for cancer cells and their efficient repair may contribute to radioresistance, particularly in hypoxic conditions. Carbon ions (C-ions) act independently of the oxygen concentration and trigger complex- and clustered-DSBs difficult to repair. Understanding the interrelation between hypoxia, radiation-type, and DNA-repair is therefore essential for overcoming radioresistance. The DSBs signaling and the contribution of the canonical non-homologous end-joining (NHEJ-c) and homologous-recombination (HR) repair pathways were assessed by immunostaining in two cancer-stem-cell (CSCs) and non-CSCs HNSCC cell lines. Detection and signaling of DSBs were lower in response to C-ions than photons. Hypoxia increased the decay-rate of the detected DSBs (γH2AX) in CSCs after photons and the initiation of DSB repair signaling (P-ATM) in CSCs and non-CSCs after both radiations, but not the choice of DSB repair pathway (53BP1). Additionally, hypoxia increased the NHEJ-c (DNA-PK) and the HR pathway (RAD51) activation only after photons. Furthermore, the involvement of the HR seemed to be higher in CSCs after photons and in non-CSCs after C-ions. Taken together, our results show that C-ions may overcome the radioresistance of HNSCC associated with DNA repair, particularly in CSCs, and independently of a hypoxic microenvironment.

scholarly journals ATM antagonizes NHEJ proteins assembly and DNA-ends synapsis at single-ended DNA double strand breaks

2020 ◽  
Vol 48 (17) ◽  
pp. 9710-9723
Author(s):  
Sébastien Britton ◽  
Pauline Chanut ◽  
Christine Delteil ◽  
Nadia Barboule ◽  
Philippe Frit ◽  
...  
Keyword(s):  
Dna Repair ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Repair Pathways ◽  
Non Homologous End Joining ◽  
Dna Strand ◽  
Dna Ends

Abstract Two DNA repair pathways operate at DNA double strand breaks (DSBs): non-homologous end-joining (NHEJ), that requires two adjacent DNA ends for ligation, and homologous recombination (HR), that resects one DNA strand for invasion of a homologous duplex. Faithful repair of replicative single-ended DSBs (seDSBs) is mediated by HR, due to the lack of a second DNA end for end-joining. ATM stimulates resection at such breaks through multiple mechanisms including CtIP phosphorylation, which also promotes removal of the DNA-ends sensor and NHEJ protein Ku. Here, using a new method for imaging the recruitment of the Ku partner DNA-PKcs at DSBs, we uncover an unanticipated role of ATM in removing DNA-PKcs from seDSBs in human cells. Phosphorylation of DNA-PKcs on the ABCDE cluster is necessary not only for DNA-PKcs clearance but also for the subsequent MRE11/CtIP-dependent release of Ku from these breaks. We propose that at seDSBs, ATM activity is necessary for the release of both Ku and DNA-PKcs components of the NHEJ apparatus, and thereby prevents subsequent aberrant interactions between seDSBs accompanied by DNA-PKcs autophosphorylation and detrimental commitment to Lig4-dependent end-joining.

scholarly journals Genome instability and pressure on non-homologous end joining drives chemotherapy resistance via a DNA repair crisis switch in triple negative breast cancer

NAR Cancer ◽  
2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Adrian P Wiegmans ◽  
Ambber Ward ◽  
Ekaterina Ivanova ◽  
Pascal H G Duijf ◽  
Mark N Adams ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Dna Repair ◽  
Homologous Recombination ◽  
Triple Negative Breast Cancer ◽  
Triple Negative ◽  
Genome Instability ◽  
Chemotherapy Resistance ◽  
End Joining ◽  
Repair Pathways ◽  
Non Homologous End Joining

Abstract Chemotherapy is used as a standard-of-care against cancers that display high levels of inherent genome instability. Chemotherapy induces DNA damage and intensifies pressure on the DNA repair pathways that can lead to deregulation. There is an urgent clinical need to be able to track the emergence of DNA repair driven chemotherapy resistance and tailor patient staging appropriately. There have been numerous studies into chemoresistance but to date no study has elucidated in detail the roles of the key DNA repair components in resistance associated with the frontline clinical combination of anthracyclines and taxanes together. In this study, we hypothesized that the emergence of chemotherapy resistance in triple negative breast cancer was driven by changes in functional signaling in the DNA repair pathways. We identified that consistent pressure on the non-homologous end joining pathway in the presence of genome instability causes failure of the key kinase DNA-PK, loss of p53 and compensation by p73. In-turn a switch to reliance on the homologous recombination pathway and RAD51 recombinase occurred to repair residual double strand DNA breaks. Further we demonstrate that RAD51 is an actionable target for resensitization to chemotherapy in resistant cells with a matched gene expression profile of resistance highlighted by homologous recombination in clinical samples.

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