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Nonhomologous end joining

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https://www.readbyqxmd.com/read/29348327/genome-instability-as-a-consequence-of-defects-in-the-resolution-of-recombination-intermediates
#1
Stephen C West, Ying Wai Chan
The efficient processing of homologous recombination (HR) intermediates, which often contain four-way structures known as Holliday junctions (HJs), is required for proper chromosome segregation at mitosis. Eukaryotic cells possess three distinct pathways of resolution: (i) HJ dissolution mediated by BLM-topoisomerase IIIα-RMI1-RMI2 (BTR) complex, and HJ resolution catalyzed by either (ii) SLX1-SLX4-MUS81-EME1-XPF-ERCC1 (SMX complex) or (iii) GEN1. The BTR pathway acts at all times throughout the cell cycle, whereas the actions of SMX and GEN1 are restrained in S phase and become elevated late in the cell cycle to ensure the resolution of persistent recombination intermediates before mitotic division...
January 18, 2018: Cold Spring Harbor Symposia on Quantitative Biology
https://www.readbyqxmd.com/read/29321179/physiological-protein-blocks-direct-the-mre11-rad50-xrs2-and-sae2-nuclease-complex-to-initiate-dna-end-resection
#2
Giordano Reginato, Elda Cannavo, Petr Cejka
DNA double-strand break repair by homologous recombination is initiated by DNA end resection, which is commenced by the Mre11-Rad50-Xrs2 complex and Sae2 in yeast. Here we report that the nonhomologous end joining factor Ku limits the exonuclease activity of Mre11 and promotes its endonuclease to cleave 5'-terminated DNA strands at break sites. Following initial endonucleolytic cleavage past the obstacle, Exo1 specifically extends the resection track, leading to the generation of long 3' overhangs that are required for homologous recombination...
January 10, 2018: Genes & Development
https://www.readbyqxmd.com/read/29320763/a-de-novo-50-bp-gnas-intragenic-duplication-in-a-patient-with-pseudohypoparathyroidism-type-1a
#3
Erina Suzuki, Ryosuke Bo, Kaori Sue, Hiroyuki Awano, Tsutomu Ogata, Satoshi Narumi, Masayo Kagami, Shinichiro Sano, Maki Fukami
Germline intragenic mutations in the GNAS locus result in pseudohypoparathyroidism type 1a (PHP1a) and related conditions. Nearly half of the previously reported GNAS intragenic mutations were structural variants, including 3 tandem duplications of 12-25 bp. However, the precise mutation spectrum and the genomic basis of GNAS structural variants remain to be clarified. Here, we report a de novo 50-bp tandem duplication in GNAS (c.723_772dup50, p.Glu259Leufs*29) identified in a patient with typical clinical features of PHP1a...
January 11, 2018: Cytogenetic and Genome Research
https://www.readbyqxmd.com/read/29311308/dna-double-strand-break-response-factors-influence-end-joining-features-of-igh-class-switch-and-general-translocation-junctions
#4
Rohit A Panchakshari, Xuefei Zhang, Vipul Kumar, Zhou Du, Pei-Chi Wei, Jennifer Kao, Junchao Dong, Frederick W Alt
Ig heavy chain (IgH) class switch recombination (CSR) in B lymphocytes switches IgH constant regions to change antibody functions. CSR is initiated by DNA double-strand breaks (DSBs) within a donor IgH switch (S) region and a downstream acceptor S region. CSR is completed by fusing donor and acceptor S region DSB ends by classical nonhomologous end-joining (C-NHEJ) and, in its absence, by alternative end-joining that is more biased to use longer junctional microhomologies (MHs). Deficiency for DSB response (DSBR) factors, including ataxia telangiectasia-mutated (ATM) and 53BP1, variably impair CSR end-joining, with 53BP1 deficiency having the greatest impact...
January 8, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29273627/precise-and-efficient-nucleotide-substitution-near-genomic-nick-via-noncanonical-homology-directed-repair
#5
Kazuhiro Nakajima, Yue Zhou, Akiko Tomita, Yoshihiro Hirade, Channabasavaiah B Gurumurthy, Shinichiro Nakada
CRISPR/Cas9, which generates DNA double-strand breaks (DSBs) at target loci, is a powerful tool for editing genomes when codelivered with a donor DNA template. However, DSBs, which are the most deleterious type of DNA damage, often result in unintended nucleotide insertions/deletions (indels) via mutagenic nonhomologous end joining. We developed a strategy for precise gene editing that does not generate DSBs. We show that a combination of single nicks in the target gene and donor plasmid (SNGD) using Cas9D10A nickase promotes efficient nucleotide substitution by gene editing...
December 22, 2017: Genome Research
https://www.readbyqxmd.com/read/29247009/nonhomologous-dna-end-joining-for-repair-of-dna-double-strand-breaks
#6
Nicholas R Pannunzio, Go Watanabe, Michael R Lieber
Nonhomologous DNA end joining (NHEJ) is the predominant DSB repair pathway throughout the cell cycle and accounts for nearly all DSB repair outside of the S and G2 phases.  NHEJ relies on Ku to thread onto DNA termini and thereby improve the affinity of the NHEJ enzymatic components consisting of polymerases (Pol μ and Pol λ), a nuclease (the Artemis·DNA-PKcs complex), and a ligase (XLF·XRCC4·Lig4 complex).  Each of the enzymatic components is distinctive for its versatility in acting on diverse incompatible DNA end configurations coupled with a flexibility in loading order, resulting in many possible junctional outcomes from one DSB...
December 14, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/29238067/alternative-nhej-pathway-proteins-as-components-of-mycn-oncogenic-activity-in-human-neural-crest-stem-cell-differentiation-implications-for-neuroblastoma-initiation
#7
Erika A Newman, Sahiti Chukkapalli, Daniela Bashllari, Tina T Thomas, Raelene A Van Noord, Elizabeth R Lawlor, Mark J Hoenerhoff, Anthony W Opipari, Valerie P Opipari
Neuroblastoma is a cancer of neural crest stem cell (NCSC) lineage. Signaling pathways that regulate NCSC differentiation have been implicated in neuroblastoma tumorigenesis. This is exemplified by MYCN oncogene targets that balance proliferation, differentiation, and cell death similarly in normal NCSC and in high-risk neuroblastoma. Our previous work discovered a survival mechanism by which MYCN-amplified neuroblastoma circumvents cell death by upregulating components of the error-prone non-canonical alternative nonhomologous end-joining (alt-NHEJ) DNA repair pathway...
December 13, 2017: Cell Death & Disease
https://www.readbyqxmd.com/read/29232168/high-throughput-screening-approach-for-identifying-compounds-that-inhibit-nonhomologous-end-joining
#8
Andrea L Bredemeyer, Bruce S Edwards, Mark K Haynes, Abigail J Morales, Yinan Wang, Oleg Ursu, Anna Waller, Larry A Sklar, Barry P Sleckman
DNA double-strand breaks (DSBs) are repaired primarily by homologous recombination (HR) or nonhomologous end joining (NHEJ). Compounds that modulate HR have shown promise as cancer therapeutics. The V(D)J recombination reaction, which assembles antigen receptor genes in lymphocytes, is initiated by the introduction of DNA DSBs at two recombining gene segments by the RAG endonuclease, followed by the NHEJ-mediated repair of these DSBs. Here, using HyperCyt automated flow cytometry, we develop a robust high-throughput screening (HTS) assay for NHEJ that utilizes engineered pre-B-cell lines where the V(D)J recombination reaction can be induced and monitored at a single-cell level...
December 1, 2017: SLAS Discovery
https://www.readbyqxmd.com/read/29227966/pot1-inhibits-the-efficiency-but-promotes-the-fidelity-of-nonhomologous-end-joining-at-non-telomeric-dna-regions
#9
Yang Yu, Rong Tan, Qian Ren, Boya Gao, Zhejin Sheng, Juanlian Zhang, Xiaoqing Zheng, Ying Jiang, Li Lan, Zhiyong Mao
Robust DNA double strand break (DSB) repair and stabilized telomeres help maintain genome integrity, preventing the onset of aging or tumorigenesis. POT1 is one of the six factors in the shelterin complex, which protects telomeres from being recognized as DNA damages. TRF1 and TRF2, two other shelterin proteins, have been shown to participate in DNA DSB repair at non-telomeric regions, but whether POT1, which binds to single strand telomeric DNA at chromosomal ends, is involved in DNA DSB repair has not been assessed...
December 8, 2017: Aging
https://www.readbyqxmd.com/read/29227281/targeting-mcl-1-enhances-dna-replication-stress-sensitivity-to-cancer-therapy
#10
Guo Chen, Andrew T Magis, Ke Xu, Dongkyoo Park, David S Yu, Taofeek K Owonikoko, Gabriel L Sica, Sarah W Satola, Suresh S Ramalingam, Walter J Curran, Paul W Doetsch, Xingming Deng
DNA double-strand breaks (DSBs) are mainly repaired either by homologous recombination (HR) or by nonhomologous end-joining (NHEJ) pathways. Here, we showed that myeloid cell leukemia sequence 1 (Mcl-1) acts as a functional switch in selecting between HR and NHEJ pathways. Mcl-1 was cell cycle-regulated during HR, with its expression peaking in S/G2 phase. While endogenous Mcl-1 depletion reduced HR and enhanced NHEJ, Mcl-1 overexpression resulted in a net increase in HR over NHEJ. Mcl-1 directly interacted with the dimeric Ku protein complex via its Bcl-2 homology 1 and 3 (BH1 and BH3) domains, which are required for Mcl-1 to inhibit Ku-mediated NHEJ...
December 11, 2017: Journal of Clinical Investigation
https://www.readbyqxmd.com/read/29162700/double-strand-dna-breaks-are-mainly-repaired-by-the-homologous-recombination-pathway-in-early-developing-swine-embryos
#11
Rodrigo C Bohrer, Naomi Dicks, Karina Gutierrez, Raj Duggavathi, Vilceu Bordignon
DNA double-strand breaks (DSBs) are less frequent than single-strand breaks but have more harmful consequences on cell survival and physiology. Homologous recombination (HR) and nonhomologous end-joining (NHEJ) are the two main pathways that are responsible for DSB repair in eukaryotic cells, but their importance for the preservation of genome stability in totipotent blastomeres of early developing embryos has not been determined. In this study, we observed that the chemical inhibition of HR or both pathways, but not NHEJ alone, increased the number of DSBs, reduced embryo development to the blastocyst stage, and resulted in embryos with higher proportions of apoptotic cells...
November 21, 2017: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
https://www.readbyqxmd.com/read/29158395/histone-methyltransferase-mmset-promotes-aid-mediated-dna-breaks-at-the-donor-switch-region-during-class-switch-recombination
#12
Hai Vu Nguyen, Junchao Dong, Rohit A Panchakshari, Vipul Kumar, Frederick W Alt, Jean-Christophe Bories
In B cells, Ig class switch recombination (CSR) is initiated by activation-induced cytidine deaminase (AID), the activity of which leads to DNA double-strand breaks (DSBs) within IgH switch (S) regions. Preferential targeting of AID-mediated DSBs to S sequences is critical for allowing diversification of antibody functions, while minimizing potential off-target oncogenic events. Here, we used gene targeted inactivation of histone methyltransferase (HMT) multiple myeloma SET domain (MMSET) in mouse B cells and the CH12F3 cell line to explore its role in CSR...
November 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29155797/immunofluorescence-microscopy-of-%C3%AE-h2ax-and-53bp1-for-analyzing-the-formation-and-repair-of-dna-double-strand-breaks
#13
Henning D Popp, Susanne Brendel, Wolf-Karsten Hofmann, Alice Fabarius
DNA double-strand breaks (DSB) are serious DNA lesions. Analysis of the formation and repair of DSB is relevant in a broad spectrum of research areas including genome integrity, genotoxicity, radiation biology, aging, cancer, and drug development. In response to DSB, the histone H2AX is phosphorylated at Serine 139 in a region of several megabase pairs forming discrete nuclear foci detectable by immunofluorescence microscopy. In addition, 53BP1 (p53 binding protein 1) is another important DSB-responsive protein promoting repair of DSB by nonhomologous end-joining while preventing homologous recombination...
November 3, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/29149412/the-translationally-controlled-tumor-protein-and-the-cellular-response-to-ionizing-radiation-induced-dna-damage
#14
Jie Zhang, Grace Shim, Sonia M de Toledo, Edouard I Azzam
The absorption of ionizing radiation by living cells can directly disrupt atomic structures, producing chemical and biological changes. It can also act indirectly through radiolysis of water, thereby generating reactive chemical species that may damage nucleic acids, proteins, and lipids. Together, the direct and indirect effects of radiation initiate a series of biochemical and molecular signaling events that may repair the damage or culminate in permanent physiological changes or cell death. In efforts to gain insight into the mechanisms underlying these effects, we observed a prominent upregulation of the Translationally Controlled Tumor Protein (TCTP) in low dose/low dose rate (137)Cs γ-irradiated cells that was associated with adaptive responses that reduced chromosomal damage to a level lower than what occurs spontaneously...
2017: Results and Problems in Cell Differentiation
https://www.readbyqxmd.com/read/29136592/human-sirtuin-3-sirt3-deacetylates-histone-h3-lysine-56-to-promote-nonhomologous-end-joining-repair
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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