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https://www.readbyqxmd.com/read/27930670/ku-binding-on-telomeres-occurs-at-sites-distal-from-the-physical-chromosome-ends
#1
Mélanie V Larcher, Emeline Pasquier, R Stephen MacDonald, Raymund J Wellinger
The Ku complex binds non-specifically to DNA breaks and ensures repair via NHEJ. However, Ku is also known to bind directly to telomeric DNA ends and its presence there is associated with telomere capping, but avoiding NHEJ. How the complex discriminates between a DNA break and a telomeric extremity remains unknown. Our results using a tagged Ku complex, or a chromosome end capturing method, in budding yeast show that yKu association with telomeres can occur at sites distant from the physical end, on sub-telomeric elements, as well as on interstitial telomeric repeats...
December 2016: PLoS Genetics
https://www.readbyqxmd.com/read/27926866/inflammation-induced-oxidative-stress-mediates-gene-fusion-formation-in-prostate-cancer
#2
Ram S Mani, Mohammad A Amin, Xiangyi Li, Shanker Kalyana-Sundaram, Brendan A Veeneman, Lei Wang, Aparna Ghosh, Adam Aslam, Susmita G Ramanand, Bradley J Rabquer, Wataru Kimura, Maxwell Tran, Xuhong Cao, Sameek Roychowdhury, Saravana M Dhanasekaran, Nallasivam Palanisamy, Hesham A Sadek, Payal Kapur, Alisa E Koch, Arul M Chinnaiyan
Approximately 50% of prostate cancers are associated with gene fusions of the androgen-regulated gene TMPRSS2 to the oncogenic erythroblast transformation-specific (ETS) transcription factor ERG. The three-dimensional proximity of TMPRSS2 and ERG genes, in combination with DNA breaks, facilitates the formation of TMPRSS2-ERG gene fusions. However, the origins of DNA breaks that underlie gene fusion formation in prostate cancers are far from clear. We demonstrate a role for inflammation-induced oxidative stress in the formation of DNA breaks leading to recurrent TMPRSS2-ERG gene fusions...
December 6, 2016: Cell Reports
https://www.readbyqxmd.com/read/27924007/bridging-of-double-stranded-breaks-by-the-nonhomologous-end-joining-ligation-complex-is-modulated-by-dna-end-chemistry
#3
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
#4
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
#5
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/27921283/choices-have-consequences-the-nexus-between-dna-repair-pathways-and-genomic-instability-in-cancer
#6
REVIEW
Sonali Bhattacharjee, Saikat Nandi
BACKGROUND: The genome is under constant assault from a multitude of sources that can lead to the formation of DNA double-stand breaks (DSBs). DSBs are cytotoxic lesions, which if left unrepaired could lead to genomic instability, cancer and even cell death. However, erroneous repair of DSBs can lead to chromosomal rearrangements and loss of heterozygosity, which in turn can also cause cancer and cell death. Hence, although the repair of DSBs is crucial for the maintenance of genome integrity the process of repair need to be well regulated and closely monitored...
December 2016: Clinical and Translational Medicine
https://www.readbyqxmd.com/read/27918550/selective-y-centromere-inactivation-triggers-chromosome-shattering-in-micronuclei-and-repair-by-non-homologous-end-joining
#7
Peter Ly, Levi S Teitz, Dong H Kim, Ofer Shoshani, Helen Skaletsky, Daniele Fachinetti, David C Page, Don W Cleveland
Chromosome missegregation into a micronucleus can cause complex and localized genomic rearrangements known as chromothripsis, but the underlying mechanisms remain unresolved. Here we developed an inducible Y centromere-selective inactivation strategy by exploiting a CENP-A/histone H3 chimaera to directly examine the fate of missegregated chromosomes in otherwise diploid human cells. Using this approach, we identified a temporal cascade of events that are initiated following centromere inactivation involving chromosome missegregation, fragmentation, and re-ligation that span three consecutive cell cycles...
December 5, 2016: Nature Cell Biology
https://www.readbyqxmd.com/read/27917791/investigation-of-the-expression-of-rif1-gene-on-head-and-neck-pancreatic-and-brain-cancer-and-cancer-stem-cells
#8
Hacer E GursesCila, Muradiye Acar, Furkan B Barut, Mehmet Gunduz, Reidar Grenman, Esra Gunduz
PURPOSE: Recent studies have shown that cancer stem cells are resistant to chemotherapy. The aim of this study was to compare RIF1 gene expression in head and neck, pancreatic cancer and glioma cell lines and the cancer stem cells isolated from these cell lines. METHODS: UT-SCC-74 from Turku University and UT-SCC-74B primary tumor metastasis and neck cancer cell lines, YKG-1 glioma cancer cell line from RIKEN, pancreatic cancer cell lines and ASPC-1 cells from ATCC were grown in cell culture...
December 1, 2016: Clinical and Investigative Medicine. Médecine Clinique et Experimentale
https://www.readbyqxmd.com/read/27915381/regulation-of-non-homologous-end-joining-via-post-translational-modifications-of-components-of-the-ligation-step
#9
REVIEW
Kristína Durdíková, Miroslav Chovanec
DNA double-strand breaks are the most serious type of DNA damage and non-homologous end joining (NHEJ) is an important pathway for their repair. In Saccharomyces cerevisiae, three complexes mediate the canonical NHEJ pathway, Ku (Ku70/Ku80), MRX (Mre11/Rad50/Xrs2) and DNA ligase IV (Dnl4/Lif1). Mammalian NHEJ is more complex, primarily as a consequence of the fact that more factors are involved in the process, and also because higher chromatin organization and more complex regulatory networks exist in mammals...
December 3, 2016: Current Genetics
https://www.readbyqxmd.com/read/27914769/clinicopathological-and-molecular-characteristics-of-ku-70-80-expression-in-nigerian-breast-cancer-and-its-potential-therapeutic-implications
#10
Ayodeji O J Agboola, Henry O Ebili, Victoria O Iyawe, Adekunbiola A F Banjo, Babatunde A Salami, Emad A Rakha, Chrstopher C Nolan, Ian O Ellis, Andrew R Green
Ku 70/80 is a regulator of the Non-Homologous End Joining (NHEJ) roles in clinicopathological features, and has prognostic significance in breast cancer (BC) in Caucasian populations. However, its significance in the Nigerian BC population, which is characterized by a higher rate of the triple-negative and basal phenotype, p53 mutation rate and BRCA1 deficiency, still needs to be investigated. We hypothesize that Ku70/80 expression shows adverse expression in Nigerian BC and, furthermore, that it is likely to have a therapeutic implication for Black BC management...
October 25, 2016: Pathology, Research and Practice
https://www.readbyqxmd.com/read/27902438/dna-double-strand-break-repair-is-involved-in-desiccation-resistance-of-sinorhizobium-meliloti-but-is-not-essential-for-its-symbiotic-interaction-with-medicago-truncatula
#11
Pierre Dupuy, Benjamin Gourion, Laurent Sauviac, Claude Bruand
The soil bacterium Sinorhizobium meliloti, a nitrogen-fixing symbiont of legume plants, is exposed to numerous stress conditions in nature, some of which cause the formation of harmful DNA double strand breaks (DSB). In particular, the reactive oxygen (ROS) and nitrogen (RNS) species produced during symbiosis, and the desiccation occurring in dry soils, are conditions which induce DSB. Two major systems of DSB repair are known in S. meliloti: homologous recombination (HR) and non-homologous end-joining (NHEJ)...
November 23, 2016: Microbiology
https://www.readbyqxmd.com/read/27895153/ubiquitylation-of-ku80-by-rnf126-promotes-completion-of-nhej-mediated-dna-repair
#12
Noriko Ishida, Tadashi Nakagawa, Shun-Ichiro Iemura, Akira Yasui, Hiroki Shima, Yasutake Katoh, Yuko Nagasawa, Toru Natsume, Kazuhiko Igarashi, Keiko Nakayama
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...
November 28, 2016: Molecular and Cellular Biology
https://www.readbyqxmd.com/read/27883076/a-crispr-cas9-assisted-non-homologous-end-joining-strategy-for-one-step-engineering-of-bacterial-genome
#13
Tianyuan Su, Fapeng Liu, Pengfei Gu, Haiying Jin, Yizhao Chang, Qian Wang, Quanfeng Liang, Qingsheng Qi
Homologous recombination-mediated genome engineering has been broadly applied in prokaryotes with high efficiency and accuracy. However, this method is limited in realizing larger-scale genome editing with numerous genes or large DNA fragments because of the relatively complicated procedure for DNA editing template construction. Here, we describe a CRISPR-Cas9 assisted non-homologous end-joining (CA-NHEJ) strategy for the rapid and efficient inactivation of bacterial gene (s) in a homologous recombination-independent manner and without the use of selective marker...
November 24, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27875301/an-intrinsically-disordered-aplf-links-ku-dna-pkcs-and-xrcc4-dna-ligase-iv-in-an-extended-flexible-non-homologous-end-joining-complex
#14
Michal Hammel, Yaping Yu, Sarvan Kumar Radhakrishnan, Chirayu Chokshi, Miaw-Sheue Tsai, Yoshihiro Matsumoto, Monica Kuzdovich, Soumya G Remesh, Shujuan Fang, Alan E Tomkinson, Susan P Lees-Miller, John A Tainer
DNA double-strand break (DSB) repair by non-homologous end joining (NHEJ) in human cells is initiated by Ku heterodimer binding to a DSB, followed by recruitment of core NHEJ factors including DNA-dependent protein kinase catalytic subunit (DNA-PKcs), XRCC4-like factor (XLF) and XRCC4 (X4)-DNA ligase IV (L4). In addition, Ku interacts with accessory factors such as Aprataxin and Polynucleotide kinase/phosphatase-Like Factor (APLF), yet how these factors interact to tether, process and ligate DSB ends while allowing regulation and chromatin interactions remains enigmatic...
November 14, 2016: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/27869163/wwox-brca1-interaction-role-in-dna-repair-pathway-choice
#15
M S Schrock, B Batar, J Lee, T Druck, B Ferguson, J H Cho, K Akakpo, H Hagrass, N A Heerema, F Xia, J D Parvin, C M Aldaz, K Huebner
In this study, loss of expression of the fragile site-encoded Wwox protein was found to contribute to radiation and cisplatin resistance of cells, responses that could be associated with cancer recurrence and poor outcome. WWOX gene deletions occur in a variety of human cancer types, and reduced Wwox protein expression can be detected early during cancer development. We found that Wwox loss is followed by mild chromosome instability in genomes of mouse embryo fibroblast cells from Wwox-knockout mice. Human and mouse cells deficient for Wwox also exhibit significantly enhanced survival of ionizing radiation and bleomycin treatment, agents that induce double-strand breaks (DSBs)...
November 21, 2016: Oncogene
https://www.readbyqxmd.com/read/27869160/pot1-ob-fold-mutations-unleash-telomere-instability-to-initiate-tumorigenesis
#16
P Gu, Y Wang, K K Bisht, L Wu, L Kukova, E M Smith, Y Xiao, S M Bailey, M Lei, J Nandakumar, S Chang
Chromosomal aberrations are a hallmark of human cancers, with complex cytogenetic rearrangements leading to genetic changes permissive for cancer initiation and progression. Protection of Telomere 1 (POT1) is an essential component of the shelterin complex and functions to maintain chromosome stability by repressing the activation of aberrant DNA damage and repair responses at telomeres. Sporadic and familial mutations in the oligosaccharide-oligonucleotide (OB) folds of POT1 have been identified in many human cancers, but the mechanism underlying how hPOT1 mutations initiate tumorigenesis has remained unclear...
November 21, 2016: Oncogene
https://www.readbyqxmd.com/read/27866150/crispr-cas9-induced-double-strand-break-repair-in-arabidopsis-non-homologous-end-joining-mutants
#17
Hexi Shen, Gary D Strunks, Bart J P M Klemann, Paul J J Hooykaas, Sylvia de Pater
Double-strand breaks (DSBs) are one of the most harmful DNA lesions. Cells utilize two main pathways for DSB repair: homologous recombination (HR) and non-homologous end-joining (NHEJ). NHEJ can be subdivided into the KU-dependent classical NHEJ (c-NHEJ) and the more error-prone KU-independent backup-NHEJ (b-NHEJ) pathways, involving the poly (ADP-ribose) polymerases (PARPs). However, in absence of these factors, cells still seem able to adequately maintain genome integrity, suggesting the presence of other b-NHEJ repair factors or pathways independent from KU and PARPs...
November 18, 2016: G3: Genes—Genomes—Genetics
https://www.readbyqxmd.com/read/27862604/whole-genome-sequencing-of-cytogenetically-balanced-chromosome-translocations-identifies-potentially-pathological-gene-disruptions-and-highlights-the-importance-of-microhomology-in-the-mechanism-of-formation
#18
Daniel Nilsson, Maria Pettersson, Peter Gustavsson, Alisa Förster, Wolfgang Hofmeister, Josephine Wincent, Vasilios Zachariadis, Britt-Marie Anderlid, Ann Nordgren, Outi Mäkitie, Valtteri Wirta, Max Käller, Francesco Vezzi, James R Lupski, Magnus Nordenskjöld, Elisabeth Syk Lundberg, Claudia M B Carvalho, Anna Lindstrand
Most balanced translocations are thought to result mechanistically from nonhomologous end joining or, in rare cases of recurrent events, by nonallelic homologous recombination. Here, we use low-coverage mate pair whole-genome sequencing to fine map rearrangement breakpoint junctions in both phenotypically normal and affected translocation carriers. In total, 46 junctions from 22 carriers of balanced translocations were characterized. Genes were disrupted in 48% of the breakpoints; recessive genes in four normal carriers and known dominant intellectual disability genes in three affected carriers...
November 16, 2016: Human Mutation
https://www.readbyqxmd.com/read/27854212/non-random-distribution-of-dmd-deletion-breakpoints-and-implication-of-double-strand-breaks-repair-and-replication-error-repair-mechanisms
#19
Isabelle Marey, Rabah Ben Yaou, Nathalie Deburgrave, Aurélie Vasson, Juliette Nectoux, France Leturcq, Bruno Eymard, Pascal Laforet, Anthony Behin, Tanya Stojkovic, Michèle Mayer, Vincent Tiffreau, Isabelle Desguerre, François Constant Boyer, Aleksandra Nadaj-Pakleza, Xavier Ferrer, Karim Wahbi, Henri-Marc Becane, Mireille Claustres, Jamel Chelly, Mireille Cossee
BACKGROUND: Dystrophinopathies are mostly caused by copy number variations, especially deletions, in the dystrophin gene (DMD). Despite the large size of the gene, deletions do not occur randomly but mainly in two hot spots, the main one involving exons 45 to 55. The underlying mechanisms are complex and implicate two main mechanisms: Non-homologous end joining (NHEJ) and micro-homology mediated replication-dependent recombination (MMRDR). OBJECTIVE: Our goals were to assess the distribution of intronic breakpoints (BPs) in the genomic sequence of the main hot spot of deletions within DMD gene and to search for specific sequences at or near to BPs that might promote BP occurrence or be associated with DNA break repair...
May 27, 2016: Journal of Neuromuscular Diseases
https://www.readbyqxmd.com/read/27853172/lithium-promotes-dna-stability-and-survival-of-ischemic-retinal-neurocytes-by-upregulating-dna-ligase-iv
#20
Ying Yang, Nandan Wu, Sijia Tian, Fan Li, Huan Hu, Pei Chen, Xiaoxiao Cai, Lijun Xu, Jing Zhang, Zhao Chen, Jian Ge, Keming Yu, Jing Zhuang
Neurons display genomic fragility and show fragmented DNA in pathological degeneration. A failure to repair DNA breaks may result in cell death or apoptosis. Lithium protects retinal neurocytes following nutrient deprivation or partial nerve crush, but the underlying mechanisms are not well defined. Here we demonstrate that pretreatment with lithium protects retinal neurocytes from ischemia-induced damage and enhances light response in rat retina following ischemia-reperfusion injury. Moreover, we found that DNA nonhomologous end-joining (NHEJ) repair is implicated in this process because in ischemic retinal neurocytes, lithium significantly reduces the number of γ-H2AX foci (well-characterized markers of DNA double-strand breaks in situ) and increases the DNA ligase IV expression level...
November 17, 2016: Cell Death & Disease
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