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Nonhomologous end joining

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https://www.readbyqxmd.com/read/29717453/detection-and-quantification-of-hdr-and-nhej-induced-by-genome-editing-at-endogenous-gene-loci-using-droplet-digital-pcr
#1
Yuichiro Miyaoka, Steven J Mayerl, Amanda H Chan, Bruce R Conklin
Genome editing holds great promise for experimental biology and potential clinical use. To successfully utilize genome editing, it is critical to sensitively detect and quantify its outcomes: homology-directed repair (HDR) and nonhomologous end joining (NHEJ). This has been difficult at endogenous gene loci and instead is frequently done using artificial reporter systems. Here, we describe a droplet digital PCR (ddPCR)-based method to simultaneously measure HDR and NHEJ at endogenous gene loci. This highly sensitive and quantitative method may significantly contribute to a better understanding of DNA repair mechanisms underlying genome editing and to the improvement of genome editing technology by allowing for efficient and systematic testing of many genome editing conditions in parallel...
2018: Methods in Molecular Biology
https://www.readbyqxmd.com/read/29695624/new-crispr-mutagenesis-strategies-reveal-variation-in-repair-mechanisms-among-fungi
#2
Valmik K Vyas, G Guy Bushkin, Douglas A Bernstein, Matthew A Getz, Magdalena Sewastianik, M Inmaculada Barrasa, David P Bartel, Gerald R Fink
We have created new vectors for clustered regularly interspaced short palindromic repeat (CRISPR) mutagenesis in Candida albicans , Saccharomyces cerevisiae , Candida glabrata , and Naumovozyma castellii These new vectors permit a comparison of the requirements for CRISPR mutagenesis in each of these species and reveal different dependencies for repair of the Cas9 double-stranded break. Both C. albicans and S. cerevisiae rely heavily on homology-directed repair, whereas C. glabrata and N. castellii use both homology-directed and nonhomologous end-joining pathways...
April 25, 2018: MSphere
https://www.readbyqxmd.com/read/29686104/interdependent-and-separable-functions-of-caenorhabditis-elegans-mrn-c-complex-members-couple-formation-and-repair-of-meiotic-dsbs
#3
Chloe Girard, Baptiste Roelens, Karl A Zawadzki, Anne M Villeneuve
Faithful inheritance of genetic information through sexual reproduction relies on the formation of crossovers between homologous chromosomes during meiosis, which, in turn, relies on the formation and repair of numerous double-strand breaks (DSBs). As DSBs pose a potential threat to the genome, mechanisms that ensure timely and error-free DSB repair are crucial for successful meiosis. Here, we identify NBS-1, the Caenorhabditis elegans ortholog of the NBS1 (mutated in Nijmegen Breakage Syndrome) subunit of the conserved MRE11-RAD50-NBS1/Xrs2 (MRN) complex, as a key mediator of DSB repair via homologous recombination (HR) during meiosis...
April 23, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29680088/clustered-regularly-interspaced-short-palindromic-repeat-crispr-crispr-associated-endonuclease-cas9-mediated-homology-independent-integration-for-generating-quality-control-materials-for-clinical-molecular-genetic-testing
#4
Guigao Lin, Kuo Zhang, Rongxue Peng, Yanxi Han, Jiehong Xie, Jinming Li
Genome-edited human cell lines are important resources for producing quality control materials for clinical molecular genetic testing. Generating cell lines with defined mutations through homology-directed repair-based methods are inefficient and can lead to unwanted insertions and deletions in the target loci. Nonhomologous end joining in the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated endonuclease Cas9 (Cas9) system was harnessed to generate genome-engineered cell lines harboring target mutations...
May 2018: Journal of Molecular Diagnostics: JMD
https://www.readbyqxmd.com/read/29659581/an-interplay-between-multiple-sirtuins-promotes-completion-of-dna-replication-in-cells-with-short-telomeres
#5
Antoine Simoneau, Étienne Ricard, Hugo Wurtele
The evolutionarily-conserved sirtuin family of histone deacetylases regulates a multitude of DNA-associated processes. A recent genome-wide screen conducted in the yeast Saccharomyces cerevisiae identified Yku70/80, which regulate nonhomologous end-joining (NHEJ) and telomere structure, as being essential for cell proliferation in the presence of the pan-sirtuin inhibitor nicotinamide (NAM). Here, we show that sirtuin-dependent deacetylation of both histone H3 lysine 56 and H4 lysine 16 promotes growth of yku70Δ and yku80Δ cells, and that the NAM sensitivity of these mutants is not caused by defects in double-strand break repair by NHEJ, but rather by their inability to maintain normal telomere length...
April 16, 2018: PLoS Genetics
https://www.readbyqxmd.com/read/29655920/suppressing-ku70-ku80-expression-elevates-homology-directed-repair-efficiency-in-primary-fibroblasts
#6
Guoling Li, Dewu Liu, Xianwei Zhang, Rong Quan, Cuili Zhong, Jianxin Mo, Yaoqiang Huang, Haoqiang Wang, Xiaofang Ruan, Zheng Xu, Enqin Zheng, Ting Gu, Linjun Hong, Zicong Li, Zhenfang Wu, Huaqiang Yang
The main DNA repair pathways, nonhomologous end joining (NHEJ) and homology-directed repair (HDR), are complementary to each other; hence, interruptions of the NHEJ pathway can favor HDR. Improving HDR efficiency in animal primary fibroblasts can facilitate the generation of gene knock-in animals with agricultural and biomedical values by somatic cell nuclear transfer. In this study, we used siRNA to suppress the expression of Ku70 and Ku80, which are the key factors in NHEJ pathway, to investigate the effect of Ku silencing on the HDR efficiency in pig fetal fibroblasts...
April 12, 2018: International Journal of Biochemistry & Cell Biology
https://www.readbyqxmd.com/read/29622803/simultaneous-reprogramming-and-gene-editing-of-human-fibroblasts
#7
Sara E Howden, James A Thomson, Melissa H Little
The utility of human induced pluripotent stem cells (iPSCs) is enhanced by an ability to precisely modify a chosen locus with minimal impact on the remaining genome. However, the derivation of gene-edited iPSCs typically involves multiple steps requiring lengthy culture periods and several clonal events. Here, we describe a one-step protocol for reliable generation of clonally derived gene-edited iPSC lines from human fibroblasts in the absence of drug selection or FACS enrichment. Using enhanced episomal-based reprogramming and CRISPR/Cas9 systems, gene-edited and passage-matched unmodified iPSC lines are obtained following a single electroporation of human fibroblasts...
May 2018: Nature Protocols
https://www.readbyqxmd.com/read/29622782/multiple-sgrnas-with-overlapping-sequences-enhance-crispr-cas9-mediated-knock-in-efficiency
#8
Da Eun Jang, Jae Young Lee, Jae Hoon Lee, Ok Jae Koo, Hee Sook Bae, Min Hee Jung, Ji Hyun Bae, Woo Sung Hwang, Yoo Jin Chang, Yoon Hoo Lee, Han Woong Lee, Su Cheong Yeom
The CRISPR/Cas9 system is widely applied in genome engineering due to its simplicity and versatility. Although this has revolutionized genome-editing technology, knockin animal generation via homology directed repair (HDR) is not as efficient as nonhomologous end-joining DNA-repair-dependent knockout. Although its double-strand break activity may vary, Cas9 derived from Streptococcus pyogenens allows robust design of single-guide RNAs (sgRNAs) within the target sequence; However, prescreening for different sgRNA activities delays the process of transgenic animal generation...
April 6, 2018: Experimental & Molecular Medicine
https://www.readbyqxmd.com/read/29618789/altered-dna-repair-an-early-pathogenic-pathway-in-alzheimer-s-disease-and-obesity
#9
Hao Yu, Fiona Edith Harrison, Fen Xia
Unrepaired DNA double-strand breaks (DSBs) are lethal. The present study compared the extent of DSBs, neuronal apoptosis, and status of two major DSB repair pathways - homologous combinational repair (HR) and nonhomologous end-joining (NHEJ) - in hippocampus of 5-6 month and 16-18 month-old wild-type and APP/PSEN1 mice fed control diet or high fat diet (60% fat from lard). We performed immunohistochemical staining and quantification for nuclear foci formation of γ-H2AX for DSBs, RAD51, and 53BP1, which represent the functional status of HR and NHEJ, respectively...
April 4, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29530982/repair-of-dna-double-strand-breaks-by-mammalian-alternative-end-joining-pathways
#10
Annahita Sallmyr, Alan E Tomkinson
Alternative end-joining (alt-EJ) pathways, which repair DNA double-strand breaks (DSBs), are initiated by end resection that generates 3' single strands. This reaction is shared, at least in part, with homologous recombination but distinguishes alt-EJ from the major nonhomologous end-joining pathway. Although the alt-EJ pathways make only a minor and poorly understood contribution to DSB repair in nonmalignant cells, there is growing interest in these pathways, as they generate genomic rearrangements that are hallmarks of cancer cells...
March 12, 2018: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/29526801/bcl2-overexpressing-prostate-cancer-cells-rely-on-parp1-dependent-end-joining-and-are-sensitive-to-combined-parp-inhibitor-and-radiation-therapy
#11
Christoph Oing, Pierre Tennstedt, Ronald Simon, Jennifer Volquardsen, Kerstin Borgmann, Carsten Bokemeyer, Cordula Petersen, Ekkehard Dikomey, Kai Rothkamm, Wael Y Mansour
Here we report that BCL2 blocks DNA double strand break (DSB) repair via nonhomologous end-joining (NHEJ), through sequestration of KU80 protein outside the nucleus. We find that this effect is associated with a repair switch to the error-prone PARP1-dependent end-joining (PARP1-EJ). We present in-vitro proof-of-concept for therapeutic targeting of this switch using PARP inhibitor to specifically enhance the radiosensitivity of BCL2-overexpressing cells. Given its erroneous behavior, PARP1-EJ might allow for the accumulation of genetic alterations and tumor progression...
June 1, 2018: Cancer Letters
https://www.readbyqxmd.com/read/29523244/recovery-of-alternative-end-joining-repair-products-from-drosophila-embryos
#12
Terrence Hanscom, Varandt Y Khodaverdian, Mitch McVey
In this chapter, we describe a method for the recovery and analysis of alternative end-joining (alt-EJ) DNA double-strand break repair junctions following I-SceI cutting in Drosophila melanogaster embryos. Alt-EJ can be defined as a set of Ku70/80 and DNA ligase 4-independent end-joining processes that are typically mutagenic, producing deletions, insertions, and chromosomal rearrangements more frequently than higher-fidelity repair pathways such as classical nonhomologous end joining or homologous recombination...
2018: Methods in Enzymology
https://www.readbyqxmd.com/read/29522271/inhibition-of-pc4-radiosensitizes-non-small-cell-lung-cancer-by-transcriptionally-suppressing-xlf
#13
Tian Zhang, Xiaojie Liu, Xiuli Chen, Jing Wang, Yuwen Wang, Dong Qian, Qingsong Pang, Ping Wang
Positive cofactor 4 (PC4) participates in DNA damage repair and involved in nonhomologous end joining (NHEJ). Our previous results demonstrated that knockdown of PC4 downregulated the expression of XRCC4-like factor (XLF) in esophageal squamous cell carcinoma. However, the mechanism how PC4 regulates the expression of XLF remains unclear. Here, we found that knockdown of PC4 increased radiosensitivity of non-small cell lung cancer (NSCLC) both in vivo and in vitro. Furthermore, we found that PC4 knockdown downregulated the expression of XLF, whereas recovering XLF expression restored radioresistance in the PC4-knockdown NSCLC cells...
April 2018: Cancer Medicine
https://www.readbyqxmd.com/read/29511621/robust-dna-repair-in-paxx-deficient-mammalian-cells
#14
Alisa Dewan, Mengtan Xing, Marie Benner Lundbæk, Raquel Gago-Fuentes, Carole Beck, Per Arne Aas, Nina-Beate Liabakk, Siri Sæterstad, Khac Thanh Phong Chau, Bodil Merete Kavli, Valentyn Oksenych
To ensure genome stability, mammalian cells employ several DNA repair pathways. Nonhomologous DNA end joining (NHEJ) is the DNA repair process that fixes double-strand breaks throughout the cell cycle. NHEJ is involved in the development of B and T lymphocytes through its function in V(D)J recombination and class switch recombination (CSR). NHEJ consists of several core and accessory factors, including Ku70, Ku80, XRCC4, DNA ligase 4, DNA-PKcs, Artemis, and XLF. Paralog of XRCC4 and XLF (PAXX) is the recently described accessory NHEJ factor that structurally resembles XRCC4 and XLF and interacts with Ku70/Ku80...
March 2018: FEBS Open Bio
https://www.readbyqxmd.com/read/29511619/normal-development-of-mice-lacking-paxx-the-paralogue-of-xrcc4-and-xlf
#15
Raquel Gago-Fuentes, Mengtan Xing, Siri Sæterstad, Antonio Sarno, Alisa Dewan, Carole Beck, Stefano Bradamante, Magnar Bjørås, Valentyn Oksenych
DNA repair consists of several cellular pathways which recognize and repair damaged DNA. The classical nonhomologous DNA end-joining (NHEJ) pathway repairs double-strand breaks in DNA. It is required for maturation of both B and T lymphocytes by supporting V(D)J recombination as well as B-cell differentiation during class switch recombination (CSR). Inactivation of NHEJ factors Ku70, Ku80, XRCC4, DNA ligase 4, DNA-PKcs, and Artemis impairs V(D)J recombination and blocks lymphocyte development. Paralogue of XRCC4 and XLF (PAXX) is an accessory NHEJ factor that has a significant impact on the repair of DNA lesions induced by ionizing radiation in human, murine, and chicken cells...
March 2018: FEBS Open Bio
https://www.readbyqxmd.com/read/29500194/an-efficient-platform-for-generating-somatic-point-mutations-with-germline-transmission-in-the-zebrafish-by-crispr-cas9-mediated-gene-editing
#16
Yibo Zhang, Zhiwei Zhang, Wei Ge
Homology-directed recombination (HDR)-mediated genome editing is a powerful approach for both basic functional study and disease modeling. Although some studies have reported HDR-mediated precise editing in nonrodent models, the efficiency of establishing pure mutant animal lines that carry specific amino acid substitutions remains low. Furthermore, because the efficiency of nonhomologous end joining (NHEJ)-induced insertion and deletion (indel) mutations is normally much higher than that of HDR-induced point mutations, it is often difficult to identify the latter in the background of indel mutations...
April 27, 2018: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/29500182/ku-dna-end-binding-activity-promotes-repair-fidelity-and-influences-end-processing-during-nonhomologous-end-joining-in-saccharomyces-cerevisiae
#17
Charlene H Emerson, Christopher R Lopez, Albert Ribes-Zamora, Erica J Polleys, Christopher L Williams, Lythou Yeo, Jacques E Zaneveld, Rui Chen, Alison A Bertuch
The Ku heterodimer acts centrally in nonhomologous end-joining (NHEJ) of DNA double-strand breaks (DSB). Saccharomyces cerevisiae Ku, like mammalian Ku, binds and recruits NHEJ factors to DSB ends. Consequently, NHEJ is virtually absent in yeast Ku null ( yku70 ∆ or yku80 ∆) strains. Previously, we unexpectedly observed imprecise NHEJ proficiency in a yeast Ku mutant with impaired DNA end-binding (DEB). However, how DEB impairment supported imprecise NHEJ was unknown. Here, we found imprecise NHEJ proficiency to be a feature of a panel of DEB-impaired Ku mutants and that DEB impairment resulted in a deficiency in precise NHEJ...
May 2018: Genetics
https://www.readbyqxmd.com/read/29458761/methods-to-study-dna-end-resection-i-recombinant-protein-purification
#18
Roopesh Anand, Cosimo Pinto, Petr Cejka
Accurate repair of DNA double-strand breaks (DSBs) is carried out by homologous recombination. In order to repair DNA breaks by the recombination pathway, the 5'-terminated DNA strand at DSB sites must be first nucleolytically processed to produce 3'-overhang. The process is termed DNA end resection and involves the interplay of several nuclease complexes. DNA end resection commits DSB repair to the recombination pathway including a process termed single-strand annealing, as resected DNA ends are generally nonligatable by the competing nonhomologous end-joining machinery...
2018: Methods in Enzymology
https://www.readbyqxmd.com/read/29440496/crispr-cas9-cleavages-in-budding-yeast-reveal-templated-insertions-and-strand-specific-insertion-deletion-profiles
#19
Brenda R Lemos, Adam C Kaplan, Ji Eun Bae, Alexander E Ferrazzoli, James Kuo, Ranjith P Anand, David P Waterman, James E Haber
Harnessing CRISPR-Cas9 technology provides an unprecedented ability to modify genomic loci via DNA double-strand break (DSB) induction and repair. We analyzed nonhomologous end-joining (NHEJ) repair induced by Cas9 in budding yeast and found that the orientation of binding of Cas9 and its guide RNA (gRNA) profoundly influences the pattern of insertion/deletions (indels) at the site of cleavage. A common indel created by Cas9 is a 1-bp (+1) insertion that appears to result from Cas9 creating a 1-nt 5' overhang that is filled in by a DNA polymerase and ligated...
February 27, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29432179/parp-1-dependent-recruitment-of-cold-inducible-rna-binding-protein-promotes-double-strand-break-repair-and-genome-stability
#20
Jung-Kuei Chen, Wen-Ling Lin, Zhang Chen, Hung-Wen Liu
Maintenance of genome integrity is critical for both faithful propagation of genetic information and prevention of mutagenesis induced by various DNA damage events. Here we report cold-inducible RNA-binding protein (CIRBP) as a newly identified key regulator in DNA double-strand break (DSB) repair. On DNA damage, CIRBP temporarily accumulates at the damaged regions and is poly(ADP ribosyl)ated by poly(ADP ribose) polymerase-1 (PARP-1). Its dissociation from the sites of damage may depend on its phosphorylation status as mediated by phosphatidylinositol 3-kinase-related kinases...
February 20, 2018: Proceedings of the National Academy of Sciences of the United States of America
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