scholarly journals Mutant huntingtin impairs Ku70-mediated DNA repair

2010 ◽  
Vol 189 (3) ◽  
pp. 425-443 ◽  
Author(s):  
Yasushi Enokido ◽  
Takuya Tamura ◽  
Hikaru Ito ◽  
Anup Arumughan ◽  
Akihiko Komuro ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Double Strand Breaks ◽  
Nonhomologous End Joining ◽  
Abnormal Behavior ◽  
Mutant Huntingtin ◽  
End Joining ◽  
Strand Breaks ◽  
Damage Repair ◽  
Dependent Protein

DNA repair defends against naturally occurring or disease-associated DNA damage during the long lifespan of neurons and is implicated in polyglutamine disease pathology. In this study, we report that mutant huntingtin (Htt) expression in neurons causes double-strand breaks (DSBs) of genomic DNA, and Htt further promotes DSBs by impairing DNA repair. We identify Ku70, a component of the DNA damage repair complex, as a mediator of the DNA repair dysfunction in mutant Htt–expressing neurons. Mutant Htt interacts with Ku70, impairs DNA-dependent protein kinase function in nonhomologous end joining, and consequently increases DSB accumulation. Expression of exogenous Ku70 rescues abnormal behavior and pathological phenotypes in the R6/2 mouse model of Huntington’s disease (HD). These results collectively suggest that Ku70 is a critical regulator of DNA damage in HD pathology.

scholarly journals Loss of autophagy causes a synthetic lethal deficiency in DNA repair

2015 ◽  
Vol 112 (3) ◽  
pp. 773-778 ◽  
Author(s):  
Emma Y. Liu ◽  
Naihan Xu ◽  
Jim O’Prey ◽  
Laurence Y. Lao ◽  
Sanket Joshi ◽  
...  
Keyword(s):  
Dna Repair ◽  
Repair Process ◽  
Double Strand Breaks ◽  
Nonhomologous End Joining ◽  
Cytoplasmic Process ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Synthetic Lethal ◽  
Strand Breaks ◽  
Genomic Damage

(Macro)autophagy delivers cellular constituents to lysosomes for degradation. Although a cytoplasmic process, autophagy-deficient cells accumulate genomic damage, but an explanation for this effect is currently unclear. We report here that inhibition of autophagy causes elevated proteasomal activity leading to enhanced degradation of checkpoint kinase 1 (Chk1), a pivotal factor for the error-free DNA repair process, homologous recombination (HR). We show that loss of autophagy critically impairs HR and that autophagy-deficient cells accrue micronuclei and sub-G1 DNA, indicators of diminished genomic integrity. Moreover, due to impaired HR, autophagy-deficient cells are hyperdependent on nonhomologous end joining (NHEJ) for repair of DNA double-strand breaks. Consequently, inhibition of NHEJ following DNA damage in the absence of autophagy results in persistence of genomic lesions and rapid cell death. Because autophagy deficiency occurs in several diseases, these findings constitute an important link between autophagy and DNA repair and highlight a synthetic lethal strategy to kill autophagy-deficient cells.

scholarly journals Persistent DNA Repair Signaling and DNA Polymerase Theta Promote Broken Chromosome Segregation

2021 ◽  
Author(s):  
Delisa E Clay ◽  
Heidi S Bretscher ◽  
Erin Jezuit ◽  
Korie Bush ◽  
Donald T Fox
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Polymerase ◽  
Chromosome Segregation ◽  
Genome Instability ◽  
Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Alternative End Joining ◽  
Segregation Of Chromosomes

Cycling cells must respond to double-strand breaks (DSBs) to avoid genome instability. Mis-segregation of chromosomes with DSBs during mitosis results in micronuclei, aberrant structures linked to disease. How cells respond to DSBs during mitosis is incompletely understood. We previously showed that Drosophila papillar cells lack DSB checkpoints (as observed in many cancer cells). Here, we show that papillar cells still recruit early-acting repair machinery (Mre11 and RPA3) to DSBs. This machinery persists as foci on DSBs as cells enter mitosis. Repair foci are resolved in a step-wise manner during mitosis. Repair signaling kinetics at DSBs depends on both monoubiquitination of the Fanconi Anemia (FA) protein Fancd2 and the alternative end- joining protein DNA Polymerase Theta. Disruption of either or both of these factors causes micronuclei after DNA damage, which disrupts intestinal organogenesis. This study reveals a mechanism for how cells with inactive DSB checkpoints can respond to DNA damage that persists into mitosis.

scholarly journals Congenital bone marrow failure in DNA-PKcs mutant mice associated with deficiencies in DNA repair

2011 ◽  
Vol 193 (2) ◽  
pp. 295-305 ◽  
Author(s):  
Shichuan Zhang ◽  
Hirohiko Yajima ◽  
HoangDinh Huynh ◽  
Junke Zheng ◽  
Elsa Callen ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Dna Damage ◽  
Dna Repair ◽  
Bone Marrow Failure ◽  
Genotoxic Stress ◽  
Nonhomologous End Joining ◽  
End Joining ◽  
Hematopoietic Stem ◽  
Dependent Protein ◽  
P53 Activation

The nonhomologous end-joining (NHEJ) pathway is essential for radioresistance and lymphocyte-specific V(D)J (variable [diversity] joining) recombination. Defects in NHEJ also impair hematopoietic stem cell (HSC) activity with age but do not affect the initial establishment of HSC reserves. In this paper, we report that, in contrast to deoxyribonucleic acid (DNA)–dependent protein kinase catalytic subunit (DNA-PKcs)–null mice, knockin mice with the DNA-PKcs3A/3A allele, which codes for three alanine substitutions at the mouse Thr2605 phosphorylation cluster, die prematurely because of congenital bone marrow failure. Impaired proliferation of DNA-PKcs3A/3A HSCs is caused by excessive DNA damage and p53-dependent apoptosis. In addition, increased apoptosis in the intestinal crypt and epidermal hyperpigmentation indicate the presence of elevated genotoxic stress and p53 activation. Analysis of embryonic fibroblasts further reveals that DNA-PKcs3A/3A cells are hypersensitive to DNA cross-linking agents and are defective in both homologous recombination and the Fanconi anemia DNA damage response pathways. We conclude that phosphorylation of DNA-PKcs is essential for the normal activation of multiple DNA repair pathways, which in turn is critical for the maintenance of diverse populations of tissue stem cells in mice.

scholarly journals Role of PRKDC in cancer initiation, progression, and treatment

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Yu Chen ◽  
Yi Li ◽  
Jiani Xiong ◽  
Bin Lan ◽  
Xuefeng Wang ◽  
...  
Keyword(s):  
Checkpoint Inhibitors ◽  
Double Strand Breaks ◽  
Nonhomologous End Joining ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Cancer Initiation ◽  
Different Types ◽  
Dependent Protein

AbstractThe PRKDC gene encodes the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) protein. DNA-PKcs plays an important role in nonhomologous end joining (NHEJ) of DNA double-strand breaks (DSBs) and is also closely related to the establishment of central immune tolerance and the maintenance of chromosome stability. The occurrence and development of different types of tumors and the results of their treatment are also influenced by DNA-PKcs, and it may also predict the results of radiotherapy, chemotherapy, and therapy with immune checkpoint inhibitors (ICIs). Here, we discuss and review the structure and mechanism of action of PRKDC and DNA-PKcs and their relationship with cancer.

scholarly journals Recent Perspectives in Radiation-Mediated DNA Damage and Repair: Role of NHEJ and Alternative Pathways

2021 ◽  
Author(s):  
Ajay Kumar Sharma ◽  
Priyanka Shaw ◽  
Aman Kalonia ◽  
M.H. Yashavarddhan ◽  
Pankaj Chaudhary ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Double Strand Breaks ◽  
Single Strand ◽  
End Joining ◽  
Strand Breaks ◽  
Single Strand Annealing ◽  
Repair Pathways ◽  
Non Homologous End Joining ◽  
Alternative Nhej

Radiation is one of the causative agents for the induction of DNA damage in biological systems. There is various possibility of radiation exposure that might be natural, man-made, intentional, or non-intentional. Published literature indicates that radiation mediated cell death is primarily due to DNA damage that could be a single-strand break, double-strand breaks, base modification, DNA protein cross-links. The double-strand breaks are lethal damage due to the breakage of both strands of DNA. Mammalian cells are equipped with strong DNA repair pathways that cover all types of DNA damage. One of the predominant pathways that operate DNA repair is a non-homologous end-joining pathway (NHEJ) that has various integrated molecules that sense, detect, mediate, and repair the double-strand breaks. Even after a well-coordinated mechanism, there is a strong possibility of mutation due to the flexible nature in joining the DNA strands. There are alternatives to NHEJ pathways that can repair DNA damage. These pathways are alternative NHEJ pathways and single-strand annealing pathways that also displayed a role in DNA repair. These pathways are not studied extensively, and many reports are showing the relevance of these pathways in human diseases. The chapter will very briefly cover the radiation, DNA repair, and Alternative repair pathways in the mammalian system. The chapter will help the readers to understand the basic and applied knowledge of radiation mediated DNA damage and its repair in the context of extensively studied NHEJ pathways and unexplored alternative NHEJ pathways.

scholarly journals Ubiquitylation of Ku80 by RNF126 Promotes Completion of Nonhomologous End Joining-Mediated DNA Repair

2016 ◽  
Vol 37 (4) ◽  
Author(s):  
Noriko Ishida ◽  
Tadashi Nakagawa ◽  
Shun-Ichiro Iemura ◽  
Akira Yasui ◽  
Hiroki Shima ◽  
...  
Keyword(s):  
Dna Repair ◽  
Ubiquitin Ligase ◽  
Double Strand Breaks ◽  
Nonhomologous End Joining ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Arginine Residues ◽  
Prolonged Retention ◽  
Damaged Dna

ABSTRACT Repair of damaged DNA is critical for maintenance of genetic information. In eukaryotes, DNA double-strand breaks (DSBs) are recognized by the Ku70-Ku80 heterodimer, which then recruits proteins that mediate repair by nonhomologous end joining (NHEJ). Prolonged retention of Ku70/80 at DSBs prevents completion of repair, however, with ubiquitylation of Ku80 having been implicated in Ku70/80 dissociation from DNA. Here, we identify RNF126 as a ubiquitin ligase that is recruited to DSBs and ubiquitylates Ku80, with UBE2D3 serving as an E2 enzyme. Knockdown of RNF126 prevented Ku70/80 dissociation from DSBs and inhibited break repair. Attenuation of Ku80 ubiquitylation by replacement of ubiquitylation site lysines with arginine residues delayed Ku70/80 release from chromatin after DSB induction by genotoxic insults. Together, our data indicate that RNF126 is a novel regulator of NHEJ that promotes completion of DNA repair by ubiquitylating Ku80 and releasing Ku70/80 from damaged DNA.

scholarly journals PARP regulates nonhomologous end joining through retention of Ku at double-strand breaks

2011 ◽  
Vol 194 (3) ◽  
pp. 367-375 ◽  
Author(s):  
C. Anne-Marie Couto ◽  
Hong-Yu Wang ◽  
Joanna C.A. Green ◽  
Rhian Kiely ◽  
Robert Siddaway ◽  
...  
Keyword(s):  
Dna Damage ◽  
Adenosine Diphosphate ◽  
Early Response ◽  
Double Strand Breaks ◽  
Nonhomologous End Joining ◽  
Dna Double Strand Breaks ◽  
Concomitant Increase ◽  
End Joining ◽  
Strand Breaks ◽  
Single Strand Breaks

Poly adenosine diphosphate (ADP)–ribosylation (PARylation) by poly ADP-ribose (PAR) polymerases (PARPs) is an early response to DNA double-strand breaks (DSBs). In this paper, we exploit Dictyostelium discoideum to uncover a novel role for PARylation in regulating nonhomologous end joining (NHEJ). PARylation occurred at single-strand breaks, and two PARPs, Adprt1b and Adprt2, were required for resistance to this kind of DNA damage. In contrast, although Adprt1b was dispensable for PARylation at DSBs, Adprt1a and, to a lesser extent, Adprt2 were required for this event. Disruption of adprt2 had a subtle impact on the ability of cells to perform NHEJ. However, disruption of adprt1a decreased the ability of cells to perform end joining with a concomitant increase in homologous recombination. PAR-dependent regulation of NHEJ was achieved through promoting recruitment and/or retention of Ku at DSBs. Furthermore, a PAR interaction motif in Ku70 was required for this regulation and efficient NHEJ. These data illustrate that PARylation at DSBs promotes NHEJ through recruitment or retention of repair factors at sites of DNA damage.

scholarly journals Nickel Carcinogenesis Mechanism: DNA Damage

2019 ◽  
Vol 20 (19) ◽  
pp. 4690 ◽  
Author(s):  
Hongrui Guo ◽  
Huan Liu ◽  
Hongbin Wu ◽  
Hengmin Cui ◽  
Jing Fang ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Molecular Mechanisms ◽  
Excision Repair ◽  
Nonhomologous End Joining ◽  
End Joining ◽  
Damage Repair ◽  
Occupational And Environmental Exposure ◽  
Base Excision

Nickel (Ni) is known to be a major carcinogenic heavy metal. Occupational and environmental exposure to Ni has been implicated in human lung and nasal cancers. Currently, the molecular mechanisms of Ni carcinogenicity remain unclear, but studies have shown that Ni-caused DNA damage is an important carcinogenic mechanism. Therefore, we conducted a literature search of DNA damage associated with Ni exposure and summarized known Ni-caused DNA damage effects. In vitro and vivo studies demonstrated that Ni can induce DNA damage through direct DNA binding and reactive oxygen species (ROS) stimulation. Ni can also repress the DNA damage repair systems, including direct reversal, nucleotide repair (NER), base excision repair (BER), mismatch repair (MMR), homologous-recombination repair (HR), and nonhomologous end-joining (NHEJ) repair pathways. The repression of DNA repair is through direct enzyme inhibition and the downregulation of DNA repair molecule expression. Up to now, the exact mechanisms of DNA damage caused by Ni and Ni compounds remain unclear. Revealing the mechanisms of DNA damage from Ni exposure may contribute to the development of preventive strategies in Ni carcinogenicity.

scholarly journals A game of musical chairs: Pro- and anti-resection factors compete for TOPBP1 binding after DNA damage

2017 ◽  
Vol 216 (3) ◽  
pp. 535-537 ◽  
Author(s):  
Kenji Shimada ◽  
Susan M. Gasser
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Binding Sites ◽  
Double Strand Breaks ◽  
Nonhomologous End Joining ◽  
Repair Pathway ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Strand Breaks ◽  
Pathway Regulation

DNA double strand breaks (DSBs) are generally repaired through nonhomologous end joining or homologous recombination. In this issue, Liu et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201607031) report that the conserved scaffold protein TOPBP1Dpb11 provides binding sites for both pro- and anti-resection factors at DSBs, providing insights into repair pathway regulation.

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