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https://www.readbyqxmd.com/read/28829673/oxygen-enhancement-ratio-in-radiation-induced-initial-dsbs-by-an-optimized-flow-cytometry-based-gamma-h2ax-analysis-in-a549-human-cancer-cells
#1
Shigeaki Sunada, Hirokazu Hirakawa, Akira Fujimori, Mitsuru Uesaka, Ryuichi Okayasu
High-linear energy transfer (LET) heavy ions cause higher therapeutic effects than low-LET radiation due to lower dependency on oxygen concentration in tumor cell killing. The lethality after irradiation largely depends on DNA double-strand breaks (DSBs), however the detailed LET dependency for DSB induction under oxic and hypoxic conditions has not been reported. Therefore, we evaluated the oxygen enhancement ratio (OER) of heavy ion-induced DSB induction using a highly-optimized flow cytometry-based method of γ-H2AX detection...
August 22, 2017: Radiation Research
https://www.readbyqxmd.com/read/28827551/small-molecules-enhance-crispr-cas9-mediated-homology-directed-genome-editing-in-primary-cells
#2
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
https://www.readbyqxmd.com/read/28827033/inhibition-of-parp1-activity-enhances-chemotherapeutic-efficiency-in-cisplatin-resistant-gastric-cancer-cells
#3
Qiang Wang, Jianping Xiong, Danping Qiu, Xue Zhao, Donglin Yan, Wenxia Xu, Zhangding Wang, Qi Chen, Sapna Panday, Aiping Li, Shouyu Wang, Jianwei Zhou
Cisplatin (DDP) is the first line chemotherapeutic drug for several cancers, including gastric cancer (GC). Unfortunately, the rapid development of drug resistance remains a significant challenge for the clinical application of cisplatin. There is an urgent need to develop new strategies to overcome DDP resistance for cancer treatment. In this study, four types of human GC cells have been divided into naturally sensitive or naturally resistant categories according to their responses to cisplatin. PARP1 activity (poly (ADP-ribose), PAR) was found to be greatly increased in cisplatin-resistant GC cells...
August 4, 2017: International Journal of Biochemistry & Cell Biology
https://www.readbyqxmd.com/read/28826474/a-sharp-pif1-dependent-threshold-separates-dna-double-strand-breaks-from-critically-short-telomeres
#4
Jonathan Strecker, Sonia Stinus, Mariana Pliego Caballero, Rachel K Szilard, Michael Chang, Daniel Durocher
DNA double-strand breaks (DSBs) and short telomeres are structurally similar, yet have diametrically opposed fates. Cells must repair DSBs while blocking the action of telomerase on these ends. Short telomeres must avoid recognition by the DNA damage response while promoting telomerase recruitment. In Saccharomyces cerevisiae, the Pif1 helicase, a telomerase inhibitor, lies at the interface of these end-fate decisions. Using Pif1 as a sensor, we uncover a transition point in which 34 bp of telomeric (TG1-3)n repeat sequence renders a DNA end insensitive to Pif1 action, thereby enabling extension by telomerase...
August 3, 2017: ELife
https://www.readbyqxmd.com/read/28822740/is-dna-damage-indispensable-for-stress-induced-senescence
#5
REVIEW
Anna Bielak-Zmijewska, Grazyna Mosieniak, Ewa Sikora
Cellular senescence is a fundamental trait of many eukaryotic organisms. Senescent cells participate both in the developmental program and in normal ageing and age-related diseases. Senescence of proliferation-prone cells is a state of permanent cell cycle arrest accompanied by metabolic activity manifested by high secretion levels of numerous factors, including pro-inflammatory ones. It seems that cell senescence is a stress response. There are many intrinsic and extrinsic stress inducers which can elicit cell senescence...
August 16, 2017: Mechanisms of Ageing and Development
https://www.readbyqxmd.com/read/28822007/brca1-like-profile-is-not-significantly-associated-with-survival-benefit-of-non-myeloablative-intensified-chemotherapy-in-the-gain-randomized-controlled-trial
#6
A G J van Rossum, P C Schouten, K E Weber, V Nekljudova, C Denkert, C Solbach, C H Köhne, C Thomssen, H Forstbauer, G Hoffmann, A Kohls, S Schmatloch, C Schem, G von Minckwitz, T Karn, V J Möbus, S C Linn, S Loibl, F Marmé
PURPOSE: The BRCA1-like profile identifies tumors with a defect in homologous recombination due to inactivation of BRCA1. This profile has been shown to predict which stage III breast cancer patients benefit from myeloablative, DNA double-strand-break-inducing chemotherapy. We tested the predictive potential of the BRCA1-like profile for adjuvant non-myeloablative, intensified dose-dense chemotherapy in the GAIN trial. METHODS: Lymph node positive breast cancer patients were randomized to 3 × 3 dose-dense cycles of intensified epirubicin, paclitaxel, and cyclophosphamide (ETC) or 4 cycles concurrent epirubicin and cyclophosphamide followed by 10 cycles of weekly paclitaxel combined with 4 cycles capecitabine (EC-TX)...
August 18, 2017: Breast Cancer Research and Treatment
https://www.readbyqxmd.com/read/28821455/rnase-hii-saves-rnha-mutant-escherichia-coli-from-r-loop-associated-chromosomal-fragmentation
#7
Elena A Kouzminova, Farid F Kadyrov, Andrei Kuzminov
The rnhAB mutant E. coli, deficient in two RNase H enzymes that remove both R-loops and incorporated ribonucleotides (rNs) from DNA, grow slowly, suggesting accumulation of rN-containing DNA lesions (R-lesions). We report that the rnhAB mutants have reduced viability, form filaments with abnormal nucleoids, induce SOS and fragment their chromosome, revealing replication and/or segregation stress. R-loops are known to interfere with replication forks, and sensitivity of the double rnhAB mutants to translation inhibition points to R-loops as precursors for R-lesions...
August 15, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28821159/inhibition-of-dna-pk-enhances-chemosensitivity-of-b-cell-precursor-acute-lymphoblastic-leukemia-cells-to-doxorubicin
#8
Fatemeh Alikarami, Majid Safa, Mohammad Faranoush, Parisa Hayat, Ahmad Kazemi
DNA damage repair pathways greatly affect the response to genotoxic drugs in cancer cells, so inhibition of such pathways could be a potentially useful strategy to enhance chemosensitivity. DNA-dependent protein kinase (DNA-PK) plays a crucial role in the repair of DNA double-strand breaks (DSBs) that are probably one of the most detrimental types of DNA damage. It has been shown that DNA-PK is highly expressed in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) cells. Less well appreciated was the effect of DNA-PK inhibition on sensitivity of BCP-ALL cells to DNA-damaging agents...
August 14, 2017: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
https://www.readbyqxmd.com/read/28820390/small-molecule-inhibitors-of-dna-pk-for-tumor-sensitization-to-anticancer-therapy
#9
M Pospisilova, M Seifrtova, M Rezacova
The most sensitive cell structure - a DNA molecule, is the common target of cancer therapy. DNA damage response (controlled by enzymes from the phosphatidylinositol 3-kinase-related kinases family - PIKK) presents many encouraging targets for improving both conventional cytotoxic anticancer therapy and individualized monotherapy. DNA-dependent protein kinase (DNA-PK) is a member of the PIKK superfamily and plays an important role in the detection and repair of DNA double-strand breaks via the non-homologous end-joining pathway...
June 2017: Journal of Physiology and Pharmacology: An Official Journal of the Polish Physiological Society
https://www.readbyqxmd.com/read/28820351/genomic-and-chromatin-features-shaping-meiotic-double-strand-break-formation-and-repair-in-mice
#10
Shintaro Yamada, Seoyoung Kim, Sam E Tischfield, Maria Jasin, Julian Lange, Scott Keeney
The SPO11-generated DNA double-strand breaks (DSBs) that initiate meiotic recombination occur non-randomly across genomes, but mechanisms shaping their distribution and repair remain incompletely understood. Here, we expand on recent studies of nucleotide-resolution DSB maps in mouse spermatocytes. We find that trimethylation of histone H3 lysine 36 around DSB hotspots is highly correlated, both spatially and quantitatively, with trimethylation of H3 lysine 4, consistent with coordinated formation and action of both PRDM9-dependent histone modifications...
August 18, 2017: Cell Cycle
https://www.readbyqxmd.com/read/28819291/a-single-molecule-assessment-of-the-protective-effect-of-dmso-against-dna-double-strand-breaks-induced-by-photo-and-%C3%AE-ray-irradiation-and-freezing
#11
Masami Noda, Yue Ma, Yuko Yoshikawa, Tadayuki Imanaka, Toshiaki Mori, Masakazu Furuta, Tatsuaki Tsuruyama, Kenichi Yoshikawa
Dimethyl sulfoxide (DMSO) is widely used as a cryoprotectant for organs, tissues, and cell suspension in storage. In addition, DMSO is known to be a useful free radical scavenger and a radio-protectant. To date, many in vitro assays using cultured cells have been performed for analysing the protective effect of DMSO against genomic DNA damage; however, currently it has been rather difficult to detect DNA double strand breaks (DSBs) in a quantitative manner. In the present study, we aimed to observe the extent of DNA damage by use of single molecular observation with a fluorescence microscope to evaluate DSBs induced by photo- and γ-ray-irradiation, or freeze/thawing in variable concentrations of DMSO...
August 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28819025/mre11-promotes-tumorigenesis-by-facilitating-resistance-to-oncogene-induced-replication-stress
#12
Elizabeth Spehalski, Kayla M Capper, Cheryl J Smith, Mary J Morgan, Maria Dinkelmann, Jeffrey Buis, JoAnn M Sekiguchi, David O Ferguson
Hypomorphic mutations in the genes encoding the MRE11/RAD50/NBS1 (MRN) DNA repair complex lead to cancer-prone syndromes. MRN binds DNA double strand breaks where it functions in repair and triggers cell cycle checkpoints via activation of the ataxia-telangiectasia mutated (ATM) kinase. To gain understanding of MRN in cancer, we engineered mice with B lymphocytes lacking MRN, or harboring MRN in which MRE11 lacks nuclease activities. Both forms of MRN deficiency led to hallmarks of cancer, including oncogenic translocations involving c-Myc and the immunoglobulin locus...
August 17, 2017: Cancer Research
https://www.readbyqxmd.com/read/28818740/assessment-of-genotoxicity-of-four-volatile-pollutants-from-cigarette-smoke-based-on-the-in-vitro-%C3%AE-h2ax-assay-using-high-content-screening
#13
Sen Zhang, Huan Chen, An Wang, Yong Liu, Hongwei Hou, Qingyuan Hu
To evaluate the genotoxic effects of formaldehyde, acetaldehyde, acrolein and benzene on A549 cells, the in vitro γH2AX assay was used in combination with high content screening (HCS) technology. All aldehydes showed a significant genotoxicity in a dose/time-dependent effect on the induction of γH2AX. Benzene failed to show a significant genotoxicity based on the γH2AX assay. However, hydroquinone (one of metabolites of benzene) showed a significant genotoxicity in vitro. Based on the dose-response of γH2AX and Hill model, the ability to induce DNA double-strand break can be evaluated as acrolein>formaldehyde>acetaldehyde>benzene...
July 18, 2017: Environmental Toxicology and Pharmacology
https://www.readbyqxmd.com/read/28815851/basics-of-genome-editing-technology-and-its-application-in-livestock-species
#14
REVIEW
Bjoern Petersen
In the last decade, the research community has witnessed a blooming of targeted genome editing tools and applications. Novel programmable DNA nucleases such as zinc finger nucleases (ZFNs), transcription activator-like endonucleases (TALENs) and the clustered regularly interspaced short palindromic repeats/Cas9 system (CRISPR/Cas9) possess long recognition sites and are capable of cutting DNA in a very specific manner. These DNA nucleases mediate targeted genetic alterations by enhancing the DNA mutation rate via induction of double-strand breaks at a predetermined genomic site...
August 2017: Reproduction in Domestic Animals, Zuchthygiene
https://www.readbyqxmd.com/read/28811466/time-lapse-crystallography-snapshots-of-a-double-strand-break-repair-polymerase-in-action
#15
Joonas A Jamsen, William A Beard, Lars C Pedersen, David D Shock, Andrea F Moon, Juno M Krahn, Katarzyna Bebenek, Thomas A Kunkel, Samuel H Wilson
DNA polymerase (pol) μ is a DNA-dependent polymerase that incorporates nucleotides during gap-filling synthesis in the non-homologous end-joining pathway of double-strand break repair. Here we report time-lapse X-ray crystallography snapshots of catalytic events during gap-filling DNA synthesis by pol μ. Unique catalytic intermediates and active site conformational changes that underlie catalysis are uncovered, and a transient third (product) metal ion is observed in the product state. The product manganese coordinates phosphate oxygens of the inserted nucleotide and PPi...
August 15, 2017: Nature Communications
https://www.readbyqxmd.com/read/28810059/targeted-genome-editing-in-caenorhabditis-elegans-using-crispr-cas9
#16
REVIEW
Behnom Farboud
Utilization of programmable nucleases to generate DNA lesions at precise endogenous sequences has transformed the ability to edit genomes from microbes to plants and animals. This is especially true in organisms that previously lacked the means to engineer precise genomic changes, like Caenorhabditis elegans. C. elegans is a 1 mm long free-living, nonparasitic, nematode worm, which is easily cultivated in a laboratory. Its detailed genetic map and relatively compact genome (~100 megabases) helped make it the first metazoan to have its entire genome sequenced...
August 15, 2017: Wiley Interdisciplinary Reviews. Developmental Biology
https://www.readbyqxmd.com/read/28804761/unfolding-of-core-nucleosomes-by-parp-1-revealed-by-spfret-microscopy
#17
Daniel C Sultanov, Nadezhda S Gerasimova, Kseniya S Kudryashova, Natalya V Maluchenko, Elena Y Kotova, Marie-France Langelier, John M Pascal, Mikhail P Kirpichnikov, Alexey V Feofanov, Vasily M Studitsky
DNA accessibility to various protein complexes is essential for various processes in the cell and is affected by nucleosome structure and dynamics. Protein factor PARP-1 (poly(ADP-ribose)polymerase 1) increases the accessibility of DNA in chromatin to repair proteins and transcriptional machinery, but the mechanism and extent of this chromatin reorganization are unknown. Here we report on the effects of PARP-1 on single nucleosomes revealed by spFRET (single-particle Förster Resonance Energy Transfer) microscopy...
2017: AIMS Genetics
https://www.readbyqxmd.com/read/28803330/bime2-a-novel-gene-required-for-interhomolog-meiotic-recombination-in-the-protist-model-organism-tetrahymena
#18
Anura Shodhan, Maria Novatchkova, Josef Loidl
Meiotic recombination is initiated by DNA double-strand breaks (DSBs). Most DSBs are converted into nonreciprocal exchanges (gene conversions) or crossovers (COs) between sister chromatids. Only a minority of DSBs are processed toward interhomolog COs, the precursors of the chiasmata that connect homologous chromosomes. Dmc1, the meiosis-specific paralog of the universal recombination protein Rad51, is required for interhomolog COs; in its absence, univalents are primarily formed. Here, we report a ciliate-specific novel meiotic gene, BIME2, which also promotes interhomolog crossing over...
August 12, 2017: Chromosome Research
https://www.readbyqxmd.com/read/28801621/efficient-generation-of-conditional-knockout-mice-via-sequential-introduction-of-lox-sites
#19
Takuro Horii, Sumiyo Morita, Mika Kimura, Naomi Terawaki, Mihiro Shibutani, Izuho Hatada
Conditional knockout using Cre/lox is essential for functional analysis of genes. CRISPR/Cas in combination with two sets of guide RNAs and a single-stranded oligonucleotide enables simultaneous insertion of two lox sequences. However, this method induces double-strand breaks at two sites on the same chromosome, which causes an undesirable chromosomal deletion and reduces the flanked lox (flox) rate. To solve this problem, we investigated a method that sequentially introduces each lox sequence at the 1-cell and 2-cell embryonic stages, respectively...
August 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28799445/molecular-efficacy-of-radio-and-chemotherapy-sequences-from-direct-dna-damages-measurements
#20
Yanfang Dong, Yunfeng Chen, Limei Zhou, Yu Shao, Xianzhi Fu, Yi Zheng
PURPOSE: To investigate the molecular aspects of the synergy of between ionizing radiation and platinum (Pt) chemotherapeutic agents in cancer treatment with chemoradiation therapy (CRT), by measuring damages induced by low-energy electrons (LEE) to DNA bound to cisplatin. LEE are produced abundantly by any types of ionizing radiation and cisplatin represents a typical Pt-chemotherapeutic agents. MATERIALS AND METHODS: Our strategy involves two parallel administrations of cisplatin and irradiation with a 4...
August 11, 2017: International Journal of Radiation Biology
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