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Nonhomologous end joining

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https://www.readbyqxmd.com/read/29136592/human-sirtuin-3-sirt3-deacetylates-histone-h3-lysine-56-to-promote-nonhomologous-end-joining-repair
#1
Amrita Sengupta, Devyani Haldar
Human sirtuin 3 (SIRT3) is a conserved NAD(+) dependent deacetylase, which functions in important cellular processes including transcription, metabolism, oxidative stress response. It is a robust mitochondrial deacetylase; however, few studies have indicated its nuclear functions. Here we report interaction of SIRT3 with core histones and identified acetylated histone H3 lysine 56 (H3K56ac) as its novel substrate, in addition to known substrates acetylated H4K16 and H3K9. Further, we showed in response to DNA damage SIRT3 localizes to the repair foci colocalizing with γH2AX and nonhomologous end joining (NHEJ) marker p53-binding protein 1 (53BP1)...
November 8, 2017: DNA Repair
https://www.readbyqxmd.com/read/29133916/brca2-antagonizes-classical-and-alternative-nonhomologous-end-joining-to-prevent-gross-genomic-instability
#2
Jinhua Han, Chunyan Ruan, Michael S Y Huen, Jiadong Wang, Anyong Xie, Chun Fu, Ting Liu, Jun Huang
BRCA2-deficient cells exhibit gross genomic instability, but the underlying mechanisms are not fully understood. Here we report that inactivation of BRCA2 but not RAD51 destabilizes RPA-coated single-stranded DNA (ssDNA) structures at resected DNA double-strand breaks (DSBs) and greatly enhances the frequency of nuclear fragmentation following cell exposure to DNA damage. Importantly, these BRCA2-associated deficits are fueled by the aberrant activation of classical (c)- and alternative (alt)- nonhomologous end-joining (NHEJ), and rely on the well-defined DNA damage signaling pathway involving the pro-c-NHEJ factor 53BP1 and its downstream effector RIF1...
November 13, 2017: Nature Communications
https://www.readbyqxmd.com/read/29129974/screening-of-pesticides-with-the-potential-of-inducing-dsb-and-successive-recombinational-repair
#3
Karen Suárez-Larios, Ana-María Salazar-Martínez, Regina Montero-Montoya
A study was realized to ascertain whether eight selected pesticides would induce double strand breaks (DSB) in lymphocyte cultures and whether this damage would induce greater levels of proteins Rad51 participating in homologous recombination or of p-Ku80 participating in nonhomologous end joining. Only five pesticides were found to induce DSB of which only glyphosate and paraoxon induced a significant increase of p-Ku80 protein, indicating that nonhomologous end joining recombinational DNA repair system would be activated...
2017: Journal of Toxicology
https://www.readbyqxmd.com/read/29116362/homologous-recombination-mediated-repair-of-dna-double-strand-breaks-operates-in-mammalian-mitochondria
#4
Sumedha Dahal, Shubham Dubey, Sathees C Raghavan
Mitochondrial DNA is frequently exposed to oxidative damage, as compared to nuclear DNA. Previously, we have shown that while microhomology-mediated end joining can account for DNA deletions in mitochondria, classical nonhomologous DNA end joining, the predominant double-strand break (DSB) repair pathway in nucleus, is undetectable. In the present study, we investigated the presence of homologous recombination (HR) in mitochondria to maintain its genomic integrity. Biochemical studies revealed that HR-mediated repair of DSBs is more efficient in the mitochondria of testes as compared to that of brain, kidney and spleen...
November 7, 2017: Cellular and Molecular Life Sciences: CMLS
https://www.readbyqxmd.com/read/29113987/bap1-is-a-novel-target-in-hpv-negative-head-and-neck-cancer
#5
Xiyou Liu, Liangpeng Yang, David P Molkentine, David Valdacanas, Shiying Yu, Manish Kumar, Raymond E Meyn, John Heymach, Heath D Skinner
PURPOSE: This study examined the potential role of the nuclear deubiquitinating enzyme BRCA1-associated protein-1 (BAP1) in radioresistance in head and neck squamous cell cancer (HNSCC). EXPERIMENTAL DESIGN: We overexpressed, knocked down, and rescued BAP1 expression in six HNSCC cell lines, three human papillomavirus (HPV) -negative and HPV-positive, and examined the effects on radiosensitivity in vitro and in HNSCC mouse xenograft models. Radiosensitivity was assessed by clonogenic cell survival and tumor growth delay assays; changes in protein expression were analyzed by immunofluorescence staining and western blotting...
November 7, 2017: Clinical Cancer Research: An Official Journal of the American Association for Cancer Research
https://www.readbyqxmd.com/read/29111596/compliance-between-clinical-and-genetic-diagnosis-of-choroidal-hypoplasia-in-103-norwegian-border-collie-puppies
#6
Siv Grosås, Frode Lingaas, Kristin Wear Prestrud, Ernst-Otto Ropstad
OBJECTIVE: To describe the frequency of the nonhomologous end-joining factor 1 (NHEJ1) mutation and the compliance between clinical and genetic diagnosis of choroidal hypoplasia (CH) in a group of Norwegian Border Collies. ANIMALS STUDIED: Border collie puppies in the age from 5 to 8 weeks. MATERIAL AND METHODS: Puppies included in the study had a complete ophthalmological examination. All findings were recorded, and an ECVO scheme form was issued for each puppy...
November 7, 2017: Veterinary Ophthalmology
https://www.readbyqxmd.com/read/29093183/therapeutic-targeting-of-pgbd5-induced-dna-repair-dependency-in-pediatric-solid-tumors
#7
Anton G Henssen, Casie Reed, Eileen Jiang, Heathcliff Dorado Garcia, Jennifer von Stebut, Ian C MacArthur, Patrick Hundsdoerfer, Jun Hyun Kim, Elisa de Stanchina, Yasumichi Kuwahara, Hajime Hosoi, Neil J Ganem, Filemon Dela Cruz, Andrew L Kung, Johannes H Schulte, John H Petrini, Alex Kentsis
Despite intense efforts, the cure rates of childhood and adult solid tumors are not satisfactory. Resistance to intensive chemotherapy is common, and targets for molecular therapies are largely undefined. We have found that the majority of childhood solid tumors, including rhabdoid tumors, neuroblastoma, medulloblastoma, and Ewing sarcoma, express an active DNA transposase, PGBD5, that can promote site-specific genomic rearrangements in human cells. Using functional genetic approaches, we discovered that mouse and human cells deficient in nonhomologous end joining (NHEJ) DNA repair cannot tolerate the expression of PGBD5...
November 1, 2017: Science Translational Medicine
https://www.readbyqxmd.com/read/29083855/repair-of-a-site-specific-dna-cleavage-old-school-lessons-for-cas9-mediated-gene-editing
#8
Danielle N Gallagher, James E Haber
CRISPR/Cas9-mediated gene editing may involve nonhomologous end-joining to create various insertion/deletions (indels) or may employ homologous recombination to modify precisely the target DNA sequence. Our understanding of these processes has been guided by earlier studies using other site-specific endonucleases, both in model organisms such as budding yeast and in mammalian cells. We briefly review what has been gleaned from such studies using the HO and I-SceI endonucleases and how these findings guide current gene editing strategies...
November 14, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/29073611/genomic-characterization-of-chromosomal-insertions-insights-into-the-mechanisms-underlying-chromothripsis
#9
Takema Kato, Yuya Ouchi, Hidehito Inagaki, Yoshio Makita, Seiji Mizuno, Mitsuharu Kajita, Toshiro Ikeda, Kazuhiro Takeuchi, Hiroki Kurahashi
Chromosomal insertions are rare structural rearrangements, and the molecular mechanisms underlying their origin are unknown. In this study, we used whole genome sequencing to analyze breakpoints and junction sequences in 4 patients with chromosomal insertions. Our analysis revealed that none of the 4 cases involved a simple insertion mediated by a 3-chromosomal breakage and rejoining events. The inserted fragments consisted of multiple pieces derived from a localized genomic region, which were shuffled and rejoined in a disorderly fashion with variable copy number alterations...
October 27, 2017: Cytogenetic and Genome Research
https://www.readbyqxmd.com/read/29058711/the-helicase-domain-of-pol%C3%AE-counteracts-rpa-to-promote-alt-nhej
#10
Pedro A Mateos-Gomez, Tatiana Kent, Sarah K Deng, Shane McDevitt, Ekaterina Kashkina, Trung M Hoang, Richard T Pomerantz, Agnel Sfeir
Mammalian polymerase theta (Polθ) is a multifunctional enzyme that promotes error-prone DNA repair by alternative nonhomologous end joining (alt-NHEJ). Here we present structure-function analyses that reveal that, in addition to the polymerase domain, Polθ-helicase activity plays a central role during double-strand break (DSB) repair. Our results show that the helicase domain promotes chromosomal translocations by alt-NHEJ in mouse embryonic stem cells and also suppresses CRISPR-Cas9- mediated gene targeting by homologous recombination (HR)...
October 23, 2017: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/28930678/dna-ligase-iv-guides-end-processing-choice-during-nonhomologous-end-joining
#11
Michael P Conlin, Dylan A Reid, George W Small, Howard H Chang, Go Watanabe, Michael R Lieber, Dale A Ramsden, Eli Rothenberg
Nonhomologous end joining (NHEJ) must adapt to diverse end structures during repair of chromosome breaks. Here, we investigate the mechanistic basis for this flexibility. DNA ends are aligned in a paired-end complex (PEC) by Ku, XLF, XRCC4, and DNA ligase IV (LIG4); we show by single-molecule analysis how terminal mispairs lead to mobilization of ends within PECs and consequent sampling of more end-alignment configurations. This remodeling is essential for direct ligation of damaged and mispaired ends during cellular NHEJ, since remodeling and ligation of such ends both require a LIG4-specific structural motif, insert1...
September 19, 2017: Cell Reports
https://www.readbyqxmd.com/read/28911097/structural-accommodation-of-ribonucleotide-incorporation-by-the-dna-repair-enzyme-polymerase-mu
#12
Andrea F Moon, John M Pryor, Dale A Ramsden, Thomas A Kunkel, Katarzyna Bebenek, Lars C Pedersen
While most DNA polymerases discriminate against ribonucleotide triphosphate (rNTP) incorporation very effectively, the Family X member DNA polymerase μ (Pol μ) incorporates rNTPs almost as efficiently as deoxyribonucleotides. To gain insight into how this occurs, here we have used X-ray crystallography to describe the structures of pre- and post-catalytic complexes of Pol μ with a ribonucleotide bound at the active site. These structures reveal that Pol μ binds and incorporates a rNTP with normal active site geometry and no distortion of the DNA substrate or nucleotide...
September 6, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28900076/-crispr-cas9-the-king-of-genome-editing-tools
#13
A V Bannikov, A V Lavrov
The discovery of CRISPR/Cas9 brought a hope for having an efficient, reliable, and readily available tool for genome editing. CRISPR/Cas9 is certainly easy to use, while its efficiency and reliability remain the focus of studies. The review describes the general principles of the organization and function of Cas nucleases and a number of important issues to be considered while planning genome editing experiments with CRISPR/Cas9. The issues include evaluation of the efficiency and specificity for Cas9, sgRNA selection, Cas9 variants designed artificially, and use of homologous recombination and nonhomologous end joining in DNA editing...
July 2017: Molekuliarnaia Biologiia
https://www.readbyqxmd.com/read/28893909/processive-searching-ability-varies-among-members-of-the-gap-filling-dna-polymerase-x-family
#14
Michael J Howard, Samuel H Wilson
DNA repair proteins must locate rare damaged sites within the genome. DNA polymerase β (Pol β), a member of the DNA polymerase X family that is involved in base excision repair, uses a processive hopping search mechanism to locate substrates. This effectively enhances its search footprint on DNA, increasing the probability of locating damaged sites. Processive searching has been reported or proposed for many DNA-binding proteins, raising the question of how widespread or specific to certain enzymes the ability to perform this function is...
October 20, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28887493/molecular-characterization-of-cell-free-eccdnas-in-human-plasma
#15
Jing Zhu, Fan Zhang, Meijun Du, Peng Zhang, Songbin Fu, Liang Wang
Extrachromosomal circular DNAs (eccDNAs) have been reported in most eukaryotes. However, little is known about the cell-free eccDNA profiles in circulating system such as blood. To characterize plasma cell-free eccDNAs, we performed sequencing analysis in 26 libraries from three blood donors and negative controls. We identified thousands of unique plasma eccDNAs in the three subjects. We observed proportional eccDNA increase with initial DNA input. The detected eccDNAs were also associated with circular DNA enrichment efficiency...
September 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28882611/generation-and-crispr-cas9-editing-of-transformed-progenitor-b-cells-as-a-pseudo-physiological-system-to-study-dna-repair-gene-function-in-v-d-j-recombination
#16
Hélène Lenden Hasse, Chloé Lescale, Joy J Bianchi, Wei Yu, Marie Bedora-Faure, Ludovic Deriano
Antigen receptor gene assembly is accomplished in developing lymphocytes by the V(D)J recombination reaction, which can be separated into two steps: DNA cleavage by the recombination-activating gene (RAG) nuclease and joining of DNA double strand breaks (DSBs) by components of the nonhomologous end joining (NHEJ) pathway. Deficiencies for NHEJ factors can result in immunodeficiency and a propensity to accumulate genomic instability, thus highlighting the importance of identifying all players in this process and deciphering their functions...
September 4, 2017: Journal of Immunological Methods
https://www.readbyqxmd.com/read/28860152/proteasome-inhibitor-bortezomib-is-a-novel-therapeutic-agent-for-focal-radiation-induced-osteoporosis
#17
Abhishek Chandra, Luqiang Wang, Tiffany Young, Leilei Zhong, Wei-Ju Tseng, Michael A Levine, Keith Cengel, X Sherry Liu, Yejia Zhang, Robert J Pignolo, Ling Qin
Bone atrophy and its related fragility fractures are frequent, late side effects of radiotherapy in cancer survivors and have a detrimental impact on their quality of life. In another study, we showed that parathyroid hormone 1-34 and anti-sclerostin antibody attenuates radiation-induced bone damage by accelerating DNA repair in osteoblasts. DNA damage responses are partially regulated by the ubiquitin proteasome pathway. In the current study, we examined whether proteasome inhibitors have similar bone-protective effects against radiation damage...
August 31, 2017: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
https://www.readbyqxmd.com/read/28846869/xlf-cernunnos-an-important-but-puzzling-participant-in-the-nonhomologous-end-joining-dna-repair-pathway
#18
REVIEW
Vijay Menon, Lawrence F Povirk
DNA double strand breaks (DSBs) are one of the most deleterious DNA lesions that promote cell death, genomic instability and carcinogenesis. The two major cellular mechanisms that repair DSBs are Nonhomologous End-Joining (NHEJ) and Homologous Recombination Repair (HRR). NHEJ is the predominant pathway, in which XLF (also called Cernunnos) is a key player. Patients with XLF mutation exhibit microcephaly, lymphopenia, and growth retardation, and are immunodeficient and radiosensitive. During NHEJ, XLF interacts with XRCC4-Ligase IV, stimulates its ligase activity, and forms DNA-binding filaments of alternating XLF and XRCC4 dimers that may serve to align broken DNA and promote ligation of noncomplementary ends...
October 2017: DNA Repair
https://www.readbyqxmd.com/read/28832943/crispri-repression-of-nonhomologous-end-joining-for-enhanced-genome-engineering-via-homologous-recombination-in-yarrowia-lipolytica
#19
Cory Schwartz, Keith Frogue, Adithya Ramesh, Joshua Misa, Ian Wheeldon
In many organisms of biotechnological importance precise genome editing is limited by inherently low homologous recombination (HR) efficiencies. A number of strategies exist to increase the effectiveness of this native DNA repair pathway; however, most strategies rely on permanently disabling competing repair pathways, thus reducing an organism's capacity to repair naturally occurring double strand breaks. Here, we describe a CRISPR interference (CRISPRi) system for gene repression in the oleochemical-producing yeast Yarrowia lipolytica...
December 2017: Biotechnology and Bioengineering
https://www.readbyqxmd.com/read/28827551/small-molecules-enhance-crispr-cas9-mediated-homology-directed-genome-editing-in-primary-cells
#20
Guoling Li, Xianwei Zhang, Cuili Zhong, Jianxin Mo, Rong Quan, Jie Yang, Dewu Liu, Zicong Li, Huaqiang Yang, Zhenfang Wu
CRISPR/Cas9 is an efficient customizable nuclease to generate double-strand breaks (DSBs) in the genome. This process results in knockout of the targeted gene or knock-in of a specific DNA fragment at the targeted locus in the genome of various species. However, efficiency of knock-in mediated by homology-directed repair (HDR) pathway is substantially lower compared with the efficiency of knockout mediated by the nonhomologous end-joining (NHEJ) pathway. Suppressing NHEJ pathway or enhancing HDR pathway has been proven to enhance the nuclease-mediated knock-in efficiency in cultured cells and model organisms...
August 21, 2017: Scientific Reports
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