scholarly journals Oxidative DNA Damage in Neurons: Implication of Ku in Neuronal Homeostasis and Survival

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Daniela De Zio ◽  
Matteo Bordi ◽  
Francesco Cecconi
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Oxidative Dna Damage ◽  
Strand Break ◽  
Dna Lesions ◽  
Mitochondrial Activity ◽  
End Joining ◽  
High Accumulation ◽  
Neuronal Homeostasis ◽  
Defective Dna Repair

Oxidative DNA damage is produced by reactive oxygen species (ROS) which are generated by exogenous and endogenous sources and continuously challenge the cell. One of the most severe DNA lesions is the double-strand break (DSB), which is mainly repaired by nonhomologous end joining (NHEJ) pathway in mammals. NHEJ directly joins the broken ends, without using the homologous template. Ku70/86 heterodimer, also known as Ku, is the first component of NHEJ as it directly binds DNA and recruits other NHEJ factors to promote the repair of the broken ends. Neurons are particularly metabolically active, displaying high rates of transcription and translation, which are associated with high metabolic and mitochondrial activity as well as oxygen consumption. In such a way, excessive oxygen radicals can be generated and constantly attack DNA, thereby producing several lesions. This condition, together with defective DNA repair systems, can lead to a high accumulation of DNA damage resulting in neurodegenerative processes and defects in neurodevelopment. In light of recent findings, in this paper, we will discuss the possible implication of Ku in neurodevelopment and in mediating the DNA repair dysfunction observed in certain neurodegenerations.

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 Databases and Bioinformatics Tools for the Study of DNA Repair

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Kaja Milanowska ◽  
Kristian Rother ◽  
Janusz M. Bujnicki
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Excision Repair ◽  
Uv Light ◽  
Dna Lesions ◽  
Environmental Chemicals ◽  
Nonhomologous End Joining ◽  
End Joining ◽  
Repair Mechanisms ◽  
Base Excision

DNA is continuously exposed to many different damaging agents such as environmental chemicals, UV light, ionizing radiation, and reactive cellular metabolites. DNA lesions can result in different phenotypical consequences ranging from a number of diseases, including cancer, to cellular malfunction, cell death, or aging. To counteract the deleterious effects of DNA damage, cells have developed various repair systems, including biochemical pathways responsible for the removal of single-strand lesions such as base excision repair (BER) and nucleotide excision repair (NER) or specialized polymerases temporarily taking over lesion-arrested DNA polymerases during the S phase in translesion synthesis (TLS). There are also other mechanisms of DNA repair such as homologous recombination repair (HRR), nonhomologous end-joining repair (NHEJ), or DNA damage response system (DDR). This paper reviews bioinformatics resources specialized in disseminating information about DNA repair pathways, proteins involved in repair mechanisms, damaging agents, and DNA lesions.

scholarly journals Distinct roles of XRCC1 in genome integrity in Xenopus egg extracts

2019 ◽  
Vol 476 (24) ◽  
pp. 3791-3804 ◽  
Author(s):  
Steven Cupello ◽  
Yunfeng Lin ◽  
Shan Yan
Keyword(s):  
Oxidative Stress ◽  
Dna Damage ◽  
Dna Repair ◽  
Oxidative Dna Damage ◽  
Dna Lesions ◽  
Genome Integrity ◽  
Polymerase Beta ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Xenopus Egg Extracts

Oxidative DNA damage represents one of the most abundant DNA lesions. It remains unclear how DNA repair and DNA damage response (DDR) pathways are co-ordinated and regulated following oxidative stress. While XRCC1 has been implicated in DNA repair, it remains unknown how exactly oxidative DNA damage is repaired and sensed by XRCC1. In this communication, we have demonstrated evidence that XRCC1 is dispensable for ATR-Chk1 DDR pathway following oxidative stress in Xenopus egg extracts. Whereas APE2 is essential for SSB repair, XRCC1 is not required for the repair of defined SSB and gapped plasmids with a 5′-OH or 5′-P terminus, suggesting that XRCC1 and APE2 may contribute to SSB repair via different mechanisms. Neither Polymerase beta nor Polymerase alpha is important for the repair of defined SSB structure. Nonetheless, XRCC1 is important for the repair of DNA damage following oxidative stress. Our observations suggest distinct roles of XRCC1 for genome integrity in oxidative stress in Xenopus egg extracts.

scholarly journals ADAR-mediated RNA editing of DNA:RNA hybrids is required for DNA double strand break repair

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sonia Jimeno ◽  
Rosario Prados-Carvajal ◽  
María Jesús Fernández-Ávila ◽  
Sonia Silva ◽  
Domenico Alessandro Silvestris ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Rna Editing ◽  
Genomic Stability ◽  
Strand Break ◽  
Dna Lesions ◽  
Dna Breaks ◽  
Dna Double Strand Break ◽  
Editing Enzyme

AbstractThe maintenance of genomic stability requires the coordination of multiple cellular tasks upon the appearance of DNA lesions. RNA editing, the post-transcriptional sequence alteration of RNA, has a profound effect on cell homeostasis, but its implication in the response to DNA damage was not previously explored. Here we show that, in response to DNA breaks, an overall change of the Adenosine-to-Inosine RNA editing is observed, a phenomenon we call the RNA Editing DAmage Response (REDAR). REDAR relies on the checkpoint kinase ATR and the recombination factor CtIP. Moreover, depletion of the RNA editing enzyme ADAR2 renders cells hypersensitive to genotoxic agents, increases genomic instability and hampers homologous recombination by impairing DNA resection. Such a role of ADAR2 in DNA repair goes beyond the recoding of specific transcripts, but depends on ADAR2 editing DNA:RNA hybrids to ease their dissolution.

BCR/ABL Kinase Elevates ROS-Mediated Oxidative DNA Damage in CML Stem/Progenitor Cells and Affects the Efficiency and Fidelity of DNA Repair To Induce Genetic Instability.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 34-34
Author(s):  
Margaret Nieborowska-Skorska ◽  
Artur Slupianek ◽  
Tomasz Stoklosa ◽  
Tomasz Poplawski ◽  
Kimberly Cramer ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Genomic Instability ◽  
Chromosomal Aberrations ◽  
Oxidative Dna Damage ◽  
Point Mutations ◽  
Dna Lesions ◽  
Leukemia Cells ◽  
Abl Kinase ◽  
Imatinib Resistant

Abstract BCR/ABL kinase transforms hematopoietic stem cells (HSCs) to induce chronic myelogenous leukemia in chronic phase (CML-CP), which eventually evolves into fatal blast crisis (CML-BC). CML is a stem cell-derived but a progenitor-driven disease. In CML-CP leukemia stem (LSCs) and progenitor (LPCs) cells reside in CD34+CD38− and CD34+CD38+ populations, respectively, whereas in CML-BC LSCs are found also in CD34+CD38+ population. BCR/ABL kinase stimulates genomic instability causing imatinib-resistant point mutations and chromosomal aberrations associated with progression to CML-BC. Genomic instability may result from enhanced DNA damage and/or aberrant DNA repair mechanisms. We showed that CD34+ stem/progenitor CML cells contain higher levels of reactive oxygen species (ROS) than these from healthy donors (CML-BC>CML-CP>Normal). In addition, ROS were elevated in CD34+CD38− and CD34+CD38+ sub-populations isolated from CML-BC and CML-CP patients in comparison to cells from healthy donor. Higher ROS levels induced more oxidative DNA lesions such as oxidized bases (e.g., 8-oxoG) and DNA double-strand breaks (DSBs). ROS and oxidative DNA damage in CML stem/progenitor cells could be diminished by an antioxidant N-acetyl-cysteine. Moreover, inhibition of ROS by vitamin E reduced the frequency of imatinib-resistant BCR/ABL point mutants and chromosomal aberrations in leukemia cells in SCID mice. Cellular DNA repair systems act to remove DNA damage and ultimately preserve the informational integrity of the genome. Base excision repair (BER) and mismatch repair (MMR) are responsible for removal of oxidized bases. BER was assessed using single- and double-stranded DNA substrates containing 5-OH-U (a derivative of ROS-damaged hydroxy-deoxycytidine). MMR activity was measured by restoration of the expression of GFP from the construct containing T-G mismatch in the start codon. BCR/ABL kinase severely inhibited BER and MMR in cell lines and CD34+ CML cells, and promoted accumulation of point mutations in genes encoding BCR/ABL kinase and Na+/K+ ATPase. Inhibition of BCR/ABL kinase by imatinib restored BER and MMR activities. Oxidized bases, if not repaired, may lead to accumulation of DSBs observed in LSCs and LPCs. DSBs may be processed by homologous recombination (HR), non-homologous and-joininig (NHEJ), and single-strand annealing (SSA). HR represents faithful repair, NHEJ usually produces small deletions, and SSA causes very large deletions. Genome-integrated repair-specific reporter cassettes containing two disrupted fragments of the gene encoding GFP were used where a single DSB induced by I-SceI endonuclease in one of the fragments stimulated HR, NHEJ, or SSA. In general, BCR/ABL kinase enhanced DSBs repair activities, however at the expense of their fidelity. Numerous point mutations were introduced in HR repair products. NHEJ generated larger than usual deletions. SSA, rather rare but very unfaithful, was also induced in BCR/ABL-positive leukemia cells. In summary, BCR/ABL kinase enhanced ROS-mediated oxidative DNA damage in LSCs and LPCs. In addition, BCR/ABL inhibited BER and MMR of usually non-lethal oxidized DNA lesions leading to accumulation of point mutations. Moreover, BCR/ABL kinase stimulated HR, NHEJ and SSA of lethal DSBs, but compromised the fidelity of repair.

scholarly journals HPF1-dependent histone ADP-ribosylation triggers chromatin relaxation to promote the recruitment of repair factors at sites of DNA damage

2021 ◽  
Author(s):  
Rebecca Smith ◽  
Siham Zentout ◽  
Catherine Chapuis ◽  
Gyula Timinszky ◽  
Sebastien Huet
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Damage Response ◽  
Dna Lesions ◽  
End Joining ◽  
Adp Ribosylation ◽  
Damage Response ◽  
Non Homologous End Joining ◽  
Chromatin Relaxation ◽  
The Impact

PARP1 activity is regulated by its cofactor HPF1. The binding of HPF1 on PARP1 controls the grafting of ADP-ribose moieties on serine residues of proteins nearby the DNA lesions, mainly PARP1 and histones. However, the impact of HPF1 on DNA repair regulated by PARP1 remains unclear. Here, we show that HPF1 controls both the number and the length of the ADP-ribose chains generated by PARP1 at DNA lesions. We demonstrate that HPF1-dependent histone ADP-ribosylation, rather than auto-modification of PARP1, triggers the rapid unfolding of the chromatin structure at the DNA damage sites and promotes the recruitment of the repair factors CHD4 and CHD7. Together with the observation that HPF1 contributes to efficient repair both by homologous recombination and non-homologous end joining, our findings highlight the key roles played by this PARP1 cofactor at early stages of the DNA damage response.

scholarly journals DNA Double Strand Break Repair Pathways in Response to Different Types of Ionizing Radiation

2021 ◽  
Vol 12 ◽  
Author(s):  
Gerarda van de Kamp ◽  
Tim Heemskerk ◽  
Roland Kanaar ◽  
Jeroen Essers
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Spatial Configuration ◽  
Strand Break ◽  
Dna Lesions ◽  
Particle Therapy ◽  
Photon Radiation ◽  
Particle Radiation ◽  
Dna Double Strand Break ◽  
Repair Mechanisms

The superior dose distribution of particle radiation compared to photon radiation makes it a promising therapy for the treatment of tumors. However, the cellular responses to particle therapy and especially the DNA damage response (DDR) is not well characterized. Compared to photons, particles are thought to induce more closely spaced DNA lesions instead of isolated lesions. How this different spatial configuration of the DNA damage directs DNA repair pathway usage, is subject of current investigations. In this review, we describe recent insights into induction of DNA damage by particle radiation and how this shapes DNA end processing and subsequent DNA repair mechanisms. Additionally, we give an overview of promising DDR targets to improve particle therapy.

scholarly journals PDTM-41. INHIBITION OF DNA DOUBLE STRAND BREAK REPAIR PATHWAYS AS A PROMISING THERAPEUTIC TARGET IN DIFFUSE INTRINSIC PONTINE GLIOMAS (DIPGs)

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi196-vi196
Author(s):  
Sharmistha Pal ◽  
Jie Bian ◽  
Brendan Price ◽  
Dipanjan Chowdhury ◽  
Daphne Haas-Kogan
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Strand Break ◽  
Repair Pathway ◽  
End Joining ◽  
Dsb Repair ◽  
Dna Double Strand Break ◽  
Repair Pathways ◽  
Diffuse Intrinsic Pontine Gliomas ◽  
Pathway Inhibition

Abstract New approaches to the treatment of diffuse intrinsic pontine gliomas (DIPGs) are desperately needed. DNA damage response is essential for cells to maintain genome integrity as DNA is damaged by both endogenous and exogenous stressors. Many cancer cells exhibit hyper-dependency on specific DNA repair pathways due to either defects in DNA repair mechanisms and/or high levels of endogenous stress leading to accumulation of DNA damage lesions. Identification of DIPG-specific DNA repair deficiencies and resultant dependencies may establish novel therapeutic strategies for DIPGs. METHODS To identify pathways critical for DIPG cell survival, genome wide CRISPR-Cas9 screen was performed on patient derived DIPG cell lines followed by gene set enrichment analyses. To monitor the effects of pathway inhibition on survival, apoptosis, DNA damage and repair, assays were performed to measure cell proliferation, cleaved-caspase3, gamma-H2AX and reporter based-DNA repair efficiency. RESULTS Our unbiased CRISPR approach to uncover vulnerabilities in DIPGs identified DNA double strand break (DSBs) repair pathways as essential for DIPG cell proliferation and survival. Further studies revealed high basal DSBs in DIPG cells compared to neural stem cells and primary astrocytes that suggest dependence of DIPG cell survival on specific DSB repair pathways. We confirmed the intrinsic reliance of DIPG cells on the specific DSB repair pathway of mutagenic end-joining, and defined a key role for DNA repair in suppressing endogenous DNA damage-induced apoptotic cell death. CONCLUSION DIPG cells have high endogenous DNA damage levels and escape catastrophic genomic instability and cell death by engaging DNA repair pathways, in particular the mutagenic end-joining DNA repair pathway. Inhibition of this specific DNA repair pathway represents a promising new avenue for the treatment of DIPGs.

Local DNA synthesis is critical for DNA repair during oocyte maturation

2021 ◽  
Author(s):  
Ajay K. Singh ◽  
S. Lava Kumar ◽  
Rohit Beniwal ◽  
Aradhana Mohanty ◽  
Bhawna Kushwaha ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Synthesis ◽  
Dna Polymerase ◽  
Oocyte Maturation ◽  
Spindle Assembly Checkpoint ◽  
End Joining ◽  
Non Homologous End Joining ◽  
Defective Dna Repair ◽  
Dna Synthesis Inhibition

Mammalian oocytes can be very long-lived cells and thereby very likely to encounter DNA damage during their lifetime. Defective DNA repair may result in oocytes that are developmentally incompetent or give rise to progeny with congenital disorders. During oocyte maturation, damaged DNA is repaired primarily by non-homologous end joining (NHEJ) or homologous recombination (HR). Although these repair pathways have been studied extensively, the associated DNA synthesis is poorly characterized. Using porcine oocytes, we demonstrate that the DNA synthesis machinery is present during oocyte maturation and dynamically recruited to sites of DNA damage. DNA polymerase δ is identified as being crucial for oocyte DNA synthesis. Further, inhibiting synthesis causes DNA damage to accumulate and delays the progression of oocyte maturation. Importantly, inhibition of the spindle assembly checkpoint (SAC) bypassed the delay of oocyte maturation caused by DNA synthesis inhibition. Finally, we found that ∼20% of unperturbed oocytes experienced spontaneously-arising damage during maturation. Cumulatively, our findings indicate that oocyte maturation requires damage-associated DNA synthesis that is monitored by the SAC.

Long-term efficacy of a new medical device containing Fernblock® and DNA repair enzyme complex in the treatment and prevention of cancerization field in patients with actinic keratosis.

2019 ◽  
Vol 2 (02) ◽  
pp. 80-89
Author(s):  
Blanca De Unamuno Bustos ◽  
Natalia Chaparr´´o Aguilera ◽  
Inmaculada Azorín García ◽  
Anaid Calle Andrino ◽  
Margarita Llavador Ros ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Medical Device ◽  
Actinic Keratosis ◽  
Statistical Significance ◽  
Dna Lesions ◽  
Enzyme Complex ◽  
Repair Enzyme ◽  
P53 Expression ◽  
Cancerization Field

Actinic keratosis (AKs) are part of the cancerization field, a region adjacent to AKs containing subclinical and histologically abnormal epidermal tissue due to Ultraviolet (UV)-induced DNA damage. The photoproducts as consequence of DNA damage induced by UV are mainly cyclobutane pyrimidine dimers (CPDs). Fernblock® demonstrated in previous studies significant reduction of the number of CPDs induced by UV radiation. Photolyases are a specific group of enzymes that remove the major UV-induced DNA lesions by a mechanism called photo-reactivation. A monocentric, prospective, controlled, and double blind interventional study was performed to evaluate the effect of a new medical device (NMD) containing a DNA-repair enzyme complex (photolyases, endonucleases and glycosilases), a combination of UV-filters, and Fernblock® in the treatment of the cancerization field in 30 AK patients after photodynamic therapy. Patients were randomized into two groups: patients receiving a standard sunscreen (SS) andpatients receiving the NMD. Clinical, dermoscopic, reflectance confocal microscopy (RCM) and histological evaluations were performed. An increase of AKs was noted in all groups after three months of PDT without significant differences between them (p=0.476). A significant increase in the number of AKs was observed in SS group after six (p=0.026) and twelve months of PDT (p=0.038); however, this increase did not reach statistical significance in the NMD group. Regarding RCM evaluation, honeycomb pattern assessment after twelve months of PDT showed significant differences in the extension and grade of the atypia in the NMD group compared to SS group (p=0.030 and p=0.026, respectively). Concerning histopathological evaluation, keratinocyte atypia grade improved from baseline to six months after PDT in all the groups, with no statistically significant differences between the groups. Twelve months after PDT, p53 expression was significantly lower in the NMD group compared to SS group (p=0.028). The product was well-tolerated, with no serious adverse events reported. Our results provide evidence of the utility of this NMD in the improvement of the cancerization field and in the prevention of the development of new AKs.  

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