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Nonhomologous end joining

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https://www.readbyqxmd.com/read/28167572/an-oncogenic-alk-fusion-and-an-rras-mutation-in-kras-mutation-negative-pancreatic-ductal-adenocarcinoma
#1
Yoko Shimada, Takashi Kohno, Hideki Ueno, Yoshinori Ino, Hideyuki Hayashi, Takashi Nakaoku, Yasunari Sakamoto, Shunsuke Kondo, Chigusa Morizane, Kazuaki Shimada, Takuji Okusaka, Nobuyoshi Hiraoka
PURPOSE: Oncogenic mutations in the KRAS gene are a well-known driver event, occurring in >95% of pancreatic cancers. The objective of this study was to identify driver oncogene aberrations in pancreatic cancers without the KRAS mutation. METHODS: Whole-exome and transcriptome sequencing was performed on four cases of KRAS mutation-negative pancreatic ductal adenocarcinoma, which were identified in a cohort of 100 cases. RESULTS: One case harbored an oncogenic DCTN1-ALK fusion...
February 6, 2017: Oncologist
https://www.readbyqxmd.com/read/28159901/53bp1-contributes-to-igh-locus-chromatin-topology-during-class-switch-recombination
#2
Scott Feldman, Robert Wuerffel, Ikbel Achour, Lili Wang, Phillip B Carpenter, Amy L Kenter
In B lymphocytes, Ig class switch recombination (CSR) is induced by activation-induced cytidine deaminase, which initiates a cascade of events leading to DNA double-strand break formation in switch (S) regions. Resolution of DNA double-strand breaks proceeds through formation of S-S synaptic complexes. S-S synapsis is mediated by a chromatin loop that spans the C region domain of the Igh locus. S-S junctions are joined via a nonhomologous end joining DNA repair process. CSR occurs via an intrachromosomal looping out and deletion mechanism that is 53BP1 dependent...
February 3, 2017: Journal of Immunology: Official Journal of the American Association of Immunologists
https://www.readbyqxmd.com/read/28154079/dna-pkcs-structure-suggests-an-allosteric-mechanism-modulating-dna-double-strand-break-repair
#3
Bancinyane L Sibanda, Dimitri Y Chirgadze, David B Ascher, Tom L Blundell
DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a central component of nonhomologous end joining (NHEJ), repairing DNA double-strand breaks that would otherwise lead to apoptosis or cancer. We have solved its structure in complex with the C-terminal peptide of Ku80 at 4.3 angstrom resolution using x-ray crystallography. We show that the 4128-amino acid structure comprises three large structural units: the N-terminal unit, the Circular Cradle, and the Head. Conformational differences between the two molecules in the asymmetric unit are correlated with changes in accessibility of the kinase active site, which are consistent with an allosteric mechanism to bring about kinase activation...
February 3, 2017: Science
https://www.readbyqxmd.com/read/28137874/igd-class-switching-is-initiated-by-microbiota-and-limited-to-mucosa-associated-lymphoid-tissue-in-mice
#4
Jin Huk Choi, Kuan-Wen Wang, Duanwu Zhang, Xiaowei Zhan, Tao Wang, Chun-Hui Bu, Cassie L Behrendt, Ming Zeng, Ying Wang, Takuma Misawa, Xiaohong Li, Miao Tang, Xiaoming Zhan, Lindsay Scott, Sara Hildebrand, Anne R Murray, Eva Marie Y Moresco, Lora V Hooper, Bruce Beutler
Class-switch recombination (CSR) alters the Ig isotype to diversify antibody effector functions. IgD CSR is a rare event, and its regulation is poorly understood. We report that deficiency of 53BP1, a DNA damage-response protein, caused age-dependent overproduction of secreted IgD resulting from increased IgD CSR exclusively within B cells of mucosa-associated lymphoid tissues. IgD overproduction was dependent on activation-induced cytidine deaminase, hematopoietic MyD88 expression, and an intact microbiome, against which circulating IgD, but not IgM, was reactive...
January 30, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28125611/lung-basal-stem-cells-rapidly-repair-dna-damage-using-the-error-prone-nonhomologous-end-joining-pathway
#5
Clare E Weeden, Yunshun Chen, Stephen B Ma, Yifang Hu, Georg Ramm, Kate D Sutherland, Gordon K Smyth, Marie-Liesse Asselin-Labat
Lung squamous cell carcinoma (SqCC), the second most common subtype of lung cancer, is strongly associated with tobacco smoking and exhibits genomic instability. The cellular origins and molecular processes that contribute to SqCC formation are largely unexplored. Here we show that human basal stem cells (BSCs) isolated from heavy smokers proliferate extensively, whereas their alveolar progenitor cell counterparts have limited colony-forming capacity. We demonstrate that this difference arises in part because of the ability of BSCs to repair their DNA more efficiently than alveolar cells following ionizing radiation or chemical-induced DNA damage...
January 2017: PLoS Biology
https://www.readbyqxmd.com/read/28119335/dna-double-strand-break-repair-in-penaeus-monodon-is-predominantly-dependent-on-homologous-recombination
#6
Shikha Srivastava, Sumedha Dahal, Sharanya J Naidu, Deepika Anand, Vidya Gopalakrishnan, Rajendran Kooloth Valappil, Sathees C Raghavan
DNA double-strand breaks (DSBs) are mostly repaired by nonhomologous end joining (NHEJ) and homologous recombination (HR) in higher eukaryotes. In contrast, HR-mediated DSB repair is the major double-strand break repair pathway in lower order organisms such as bacteria and yeast. Penaeus monodon, commonly known as black tiger shrimp, is one of the economically important crustaceans facing large-scale mortality due to exposure to infectious diseases. The animals can also get exposed to chemical mutagens under the culture conditions as well as in wild...
January 24, 2017: DNA Research: An International Journal for Rapid Publication of Reports on Genes and Genomes
https://www.readbyqxmd.com/read/28114273/the-suv4-20-inhibitor-a-196-verifies-a-role-for-epigenetics-in-genomic-integrity
#7
Kenneth D Bromberg, Taylor R H Mitchell, Anup K Upadhyay, Clarissa G Jakob, Manisha A Jhala, Kenneth M Comess, Loren M Lasko, Conglei Li, Creighton T Tuzon, Yujia Dai, Fengling Li, Mohammad S Eram, Alexander Nuber, Niru B Soni, Vlasios Manaves, Mikkel A Algire, Ramzi F Sweis, Maricel Torrent, Gunnar Schotta, Chaohong Sun, Michael R Michaelides, Alex R Shoemaker, Cheryl H Arrowsmith, Peter J Brown, Vijayaratnam Santhakumar, Alberto Martin, Judd C Rice, Gary G Chiang, Masoud Vedadi, Dalia Barsyte-Lovejoy, William N Pappano
Protein lysine methyltransferases (PKMTs) regulate diverse physiological processes including transcription and the maintenance of genomic integrity. Genetic studies suggest that the PKMTs SUV420H1 and SUV420H2 facilitate proficient nonhomologous end-joining (NHEJ)-directed DNA repair by catalyzing the di- and trimethylation (me2 and me3, respectively) of lysine 20 on histone 4 (H4K20). Here we report the identification of A-196, a potent and selective inhibitor of SUV420H1 and SUV420H2. Biochemical and co-crystallization analyses demonstrate that A-196 is a substrate-competitive inhibitor of both SUV4-20 enzymes...
March 2017: Nature Chemical Biology
https://www.readbyqxmd.com/read/28062703/tas-116-a-novel-hsp90-inhibitor-selectively-enhances-radiosensitivity-of-human-cancer-cells-to-x-rays-and-carbon-ion-radiation
#8
Younghyun Lee, Shigeaki Sunada, Hirokazu Hirakawa, Akira Fujimori, Jac A Nickoloff, Ryuichi Okayasu
Hsp90 inhibitors have been investigated as cancer therapeutics in monotherapy and to augment radiotherapy; however, serious adverse effects of early-generation Hsp90 inhibitors limited their development. TAS-116 is a novel Hsp90 inhibitor with lower adverse effects than other Hsp90 inhibitors, and here, we investigated the radiosensitizing effects of TAS-116 in low linear energy transfer (LET) X-ray and high LET carbon ion-irradiated human cancer cells and mouse tumor xenografts. TAS-116 decreased cell survival of both X-ray and carbon ion-irradiated human cancer cell lines (HeLa and H1299 cells), and similar to other Hsp90 inhibitors, it did not affect radiosensitivity of noncancerous human fibroblasts...
January 2017: Molecular Cancer Therapeutics
https://www.readbyqxmd.com/read/28057860/contribution-of-canonical-nonhomologous-end-joining-to-chromosomal-rearrangements-is-enhanced-by-atm-kinase-deficiency
#9
Ragini Bhargava, Caree R Carson, Gabriella Lee, Jeremy M Stark
A likely mechanism of chromosomal rearrangement formation involves joining the ends from two different chromosomal double-strand breaks (DSBs). These events could potentially be mediated by either of two end-joining (EJ) repair pathways [canonical nonhomologous end joining (C-NHEJ) or alternative end joining (ALT-EJ)], which cause distinct rearrangement junction patterns. The relative role of these EJ pathways during rearrangement formation has remained controversial. Along these lines, we have tested whether the DNA damage response mediated by the Ataxia Telangiectasia Mutated (ATM) kinase may affect the relative influence of C-NHEJ vs...
January 24, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28030852/drug-induced-premature-senescence-model-in-human-dental-follicle-stem-cells
#10
Yuanfen Zhai, Rongbin Wei, Junjun Liu, Huihui Wang, Wenping Cai, Mengmeng Zhao, Yongguang Hu, Shuwei Wang, Tianshu Yang, Xiaodong Liu, Jianhua Yang, Shangfeng Liu
Aging is identified by a progressive decline of physiological integrity leading to age-related degenerative diseases, but its causes is unclear. Human dental pulp stem cells (hDPSCs) has a remarkable rejuvenated capacity that relies on its resident stem cells. However, because of the lack of proper senescence models, exploration of the underlying molecular mechanisms has been hindered. Here, we established a cellular model utilizing a hydroxyurea (HU) treatment protocol and effectively induced Human dental pulp stem cells to undergo cellular senescence...
January 31, 2017: Oncotarget
https://www.readbyqxmd.com/read/27994036/microhomology-mediated-end-joining-is-activated-in-irradiated-human-cells-due-to-phosphorylation-dependent-formation-of-the-xrcc1-repair-complex
#11
Arijit Dutta, Bradley Eckelmann, Sanjay Adhikari, Kazi Mokim Ahmed, Shiladitya Sengupta, Arvind Pandey, Pavana M Hegde, Miaw-Sheue Tsai, John A Tainer, Michael Weinfeld, Muralidhar L Hegde, Sankar Mitra
Microhomology-mediated end joining (MMEJ), an error-prone pathway for DNA double-strand break (DSB) repair, is implicated in genomic rearrangement and oncogenic transformation; however, its contribution to repair of radiation-induced DSBs has not been characterized. We used recircularization of a linearized plasmid with 3'-P-blocked termini, mimicking those at X-ray-induced strand breaks, to recapitulate DSB repair via MMEJ or nonhomologous end-joining (NHEJ). Sequence analysis of the circularized plasmids allowed measurement of relative activity of MMEJ versus NHEJ...
December 19, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27989139/unpredicted-downregulation-of-rad51-suggests-genome-instability-induced-by-tetrachlorobenzoquinone
#12
Xiufang Song, Qiong Shi, Zixuan Liu, Yawen Wang, Yuxin Wang, Erqun Song, Yang Song
We previously demonstrated that halogenated quinone induces DNA double strand breaks (DSBs) in a ROS-dependent manner, which coordinates with downstream repair cascade including nonhomologous end joining, base excision repair, and nucleotide excision repair. However, these error-prone processes may cause the potential risk of genome instability, and current has no information on how faithful repair route, such as homologous recombination (HR), was affected. RAD51 is a key protein in the HR pathway of DSBs repair...
December 19, 2016: Chemical Research in Toxicology
https://www.readbyqxmd.com/read/27975310/a-t7-endonuclease-i-assay-to-detect-talen-mediated-targeted-mutation-of-hbv-cccdna
#13
Kristie Bloom, Abdullah Ely, Patrick Arbuthnot
Gene editing using designer nucleases is now widely used in many fields of molecular biology. The technology is being developed for the treatment of viral infections such as persistant hepatitis B virus (HBV). The replication intermediate of HBV comprising covalently closed circular DNA (cccDNA) is stable and resistant to available licensed antiviral agents. Advancing gene editing as a means of introducing targeted mutations into cccDNA thus potentially offers the means to cure infection by the virus. Essentially, targeted mutations are initiated by intracellular DNA cleavage, then error-prone nonhomologous end joining results in insertions and deletions (indels) at intended sites...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/27956611/biasing-genome-editing-events-toward-precise-length-deletions-with-an-rna-guided-tevcas9-dual-nuclease
#14
Jason M Wolfs, Thomas A Hamilton, Jeremy T Lant, Marcon Laforet, Jenny Zhang, Louisa M Salemi, Gregory B Gloor, Caroline Schild-Poulter, David R Edgell
The CRISPR/Cas9 nuclease is commonly used to make gene knockouts. The blunt DNA ends generated by cleavage can be efficiently ligated by the classical nonhomologous end-joining repair pathway (c-NHEJ), regenerating the target site. This repair creates a cycle of cleavage, ligation, and target site regeneration that persists until sufficient modification of the DNA break by alternative NHEJ prevents further Cas9 cutting, generating a heterogeneous population of insertions and deletions typical of gene knockouts...
December 27, 2016: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/27956467/linc-complexes-promote-homologous-recombination-in-part-through-inhibition-of-nonhomologous-end-joining
#15
Katherine S Lawrence, Erin C Tapley, Victor E Cruz, Qianyan Li, Kayla Aung, Kevin C Hart, Thomas U Schwartz, Daniel A Starr, JoAnne Engebrecht
The Caenorhabditis elegans SUN domain protein, UNC-84, functions in nuclear migration and anchorage in the soma. We discovered a novel role for UNC-84 in DNA damage repair and meiotic recombination. Loss of UNC-84 leads to defects in the loading and disassembly of the recombinase RAD-51. Similar to mutations in Fanconi anemia (FA) genes, unc-84 mutants and human cells depleted of Sun-1 are sensitive to DNA cross-linking agents, and sensitivity is rescued by the inactivation of nonhomologous end joining (NHEJ)...
December 19, 2016: Journal of Cell Biology
https://www.readbyqxmd.com/read/27941126/evolution-of-resistance-against-crispr-cas9-gene-drive
#16
Robert L Unckless, Andrew G Clark, Philipp W Messer
CRISPR/Cas9 gene drive (CGD) promises to be a highly adaptable approach for spreading genetically engineered alleles throughout a species, even if those alleles impair reproductive success. CGD has been shown to be effective in laboratory crosses of insects, yet it remains unclear to what extent potential resistance mechanisms will affect the dynamics of this process in large natural populations. Here we develop a comprehensive population genetic framework for modeling CGD dynamics, which incorporates potential resistance mechanisms as well as random genetic drift...
February 2017: Genetics
https://www.readbyqxmd.com/read/27924007/bridging-of-double-stranded-breaks-by-the-nonhomologous-end-joining-ligation-complex-is-modulated-by-dna-end-chemistry
#17
Dylan A Reid, Michael P Conlin, Yandong Yin, Howard H Chang, Go Watanabe, Michael R Lieber, Dale A Ramsden, Eli Rothenberg
The nonhomologous end-joining (NHEJ) pathway is the primary repair pathway for DNA double strand breaks (DSBs) in humans. Repair is mediated by a core complex of NHEJ factors that includes a ligase (DNA Ligase IV; L4) that relies on juxtaposition of 3' hydroxyl and 5' phosphate termini of the strand breaks for catalysis. However, chromosome breaks arising from biological sources often have different end chemistries, and how these different end chemistries impact the way in which the core complex directs the necessary transitions from end pairing to ligation is not known...
December 6, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27924002/sfpq%C3%A2-nono-and-xlf-function-separately-and-together-to-promote-dna-double-strand-break-repair-via-canonical-nonhomologous-end-joining
#18
Lahcen Jaafar, Zhentian Li, Shuyi Li, William S Dynan
A complex of two related mammalian proteins, SFPQ and NONO, promotes DNA double-strand break repair via the canonical nonhomologous end joining (c-NHEJ) pathway. However, its mechanism of action is not fully understood. Here we describe an improved SFPQ•NONO-dependent in vitro end joining assay. We use this system to demonstrate that the SFPQ•NONO complex substitutes in vitro for the core c-NHEJ factor, XLF. Results are consistent with a model where SFPQ•NONO promotes sequence-independent pairing of DNA substrates, albeit in a way that differs in detail from XLF...
December 6, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27922005/wrn-regulates-pathway-choice-between-classical-and-alternative-non-homologous-end-joining
#19
Raghavendra A Shamanna, Huiming Lu, Jessica K de Freitas, Jane Tian, Deborah L Croteau, Vilhelm A Bohr
Werner syndrome (WS) is an accelerated ageing disorder with genomic instability caused by WRN protein deficiency. Many features seen in WS can be explained by the diverse functions of WRN in DNA metabolism. However, the origin of the large genomic deletions and telomere fusions are not yet understood. Here, we report that WRN regulates the pathway choice between classical (c)- and alternative (alt)-nonhomologous end joining (NHEJ) during DNA double-strand break (DSB) repair. It promotes c-NHEJ via helicase and exonuclease activities and inhibits alt-NHEJ using non-enzymatic functions...
December 6, 2016: Nature Communications
https://www.readbyqxmd.com/read/27911718/attacking-hiv-1-rna-versus-dna-by-sequence-specific-approaches-rnai-versus-crispr-cas
#20
REVIEW
Elena Herrera-Carrillo, Ben Berkhout
Human immunodeficiency virus type 1 (HIV-1) infection can be effectively controlled by potent antiviral drugs, but this never results in a cure. The patient should therefore take these drugs for the rest of his/her life, which can cause drug-resistance and adverse effects. Therefore, more durable therapeutic strategies should be considered, such as a stable gene therapy to protect the target T cells against HIV-1 infection. The development of potent therapeutic regimens based on the RNA interference (RNAi) and clustered regularly interspaced short palindromic repeats (CRISPR-Cas) mechanisms will be described, which can be delivered by lentiviral vectors...
October 15, 2016: Biochemical Society Transactions
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