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DNA Repair

Richard D Wood, Mandira Manandhar, Megan Lowery, Karen S Boulware, Kevin Lin, Yue Lu
No abstract text is available yet for this article.
January 5, 2018: DNA Repair
Timothy R L Howes, Annahita Sallmyr, Rhys Brooks, George E Greco, Darin E Jones, Yoshihiro Matsumoto, Alan E Tomkinson
No abstract text is available yet for this article.
December 19, 2017: DNA Repair
Kang-Yi Su, Hung-Ming Lai, Steven D Goodman, Wei-Yao Hu, Wern-Cherng Cheng, Liang-In Lin, Ya-Chien Yang, Woei-Horng Fang
Proofreading and DNA repair are important factors in maintaining the high fidelity of genetic information during DNA replication. Herein, we designed a non-labeled and non-radio-isotopic simple method to measure proofreading. An oligonucleotide primer is annealed to a template DNA forming a mismatched site and is proofread by Klenow fragment of Escherichia coli DNA polymerase I (pol I) in the presence of all four dideoxyribonucleotide triphosphates. The proofreading excision products and re-synthesis products of single nucleotide extension are subjected to MALDI-TOF mass spectrometry (MS)...
December 2, 2017: DNA Repair
James W Westmoreland, Michael J Mihalevic, Kara A Bernstein, Michael A Resnick
Yeast Cdc13 protein (related to human CTC1) maintains telomere stability by preventing 5'-3' end resection. While Cdc13 and Yku70/Yku80 proteins appear to prevent excessive resection, their combined contribution to maintenance of telomere ends across the genome and their relative roles at specific ends of different chromosomes have not been addressable because Cdc13 and Yku70/Yku80 double mutants are sickly. Using our PFGE-shift approach where large resected molecules have slower pulse field gel electrophoresis mobilities, along with methods for maintaining viable double mutants, we address end-resection on most chromosomes as well as telomere end differences...
November 29, 2017: DNA Repair
Henok Kassahun, Tanima SenGupta, Alfonso Schiavi, Silvia Maglioni, Hanne K Skjeldam, Katarzyna Arczewska, Nicole L Brockway, Suzanne Estes, Lars Eide, Natascia Ventura, Hilde Nilsen
Oxidation of DNA bases, an inevitable consequence of oxidative stress, requires the base excision repair (BER) pathway for repair. Caenorhabditis elegans is a well-established model to study phenotypic consequences and cellular responses to oxidative stress. To better understand how BER affects phenotypes associated with oxidative stress, we characterised the C. elegans nth-1 mutant, which lack the only DNA glycosylase dedicated to repair of oxidative DNA base damage, the NTH-1 DNA glycosylase. We show that nth-1 mutants have mitochondrial dysfunction characterised by lower mitochondrial DNA copy number, reduced mitochondrial membrane potential, and increased steady-state levels of reactive oxygen species...
November 29, 2017: DNA Repair
Katja Scheffler, Lyudmila Rachek, Panpan You, Alexander D Rowe, Wei Wang, Anna Kuśnierczyk, Lene Kittelsen, Magnar Bjørås, Lars Eide
Mitochondrial DNA (mtDNA) resides in close proximity to metabolic reactions, and is maintained by the 8-oxoguanine DNA glycosylase (Ogg1) and other members of the base excision repair pathway. Here, we tested the hypothesis that changes in liver metabolism as under fasting/feeding conditions would be sensed by liver mtDNA, and that Ogg1 deficient mice might unravel a metabolic phenotype. Wild type (WT) and ogg1-/- mice were either fed ad libitum or subjected to fasting for 24h, and the corresponding effects on liver gene expression, DNA damage, as well as serum values were analyzed...
November 28, 2017: DNA Repair
Min Hsu, Neal F Lue
Eukaryotic chromosome ends, or telomeres, are essential for genome stability and are protected by an intricate nucleoprotein assembly. Cdc13, the major single-strand telomere-binding protein in budding yeasts, mediates critical functions in both telomere protection and telomere elongation by telomerase. In particular, the interaction between S. cerevisiae Cdc13 and telomerase subunit Est1 has long served as a paradigm for telomerase regulation. However, despite extensive investigations, the role of this interaction in regulating telomerase recruitment or activation remains controversial...
November 28, 2017: DNA Repair
Jun-Ichi Akagi, Masayuki Yokoi, Young-Man Cho, Takeshi Toyoda, Haruo Ohmori, Fumio Hanaoka, Kumiko Ogawa
Genotoxic agents cause modifications of genomic DNA, such as alkylation, oxidation, bulky adduct formation, and strand breaks, which potentially induce mutations and changes to the structure or number of genes. Majority of point mutations are generated during error-prone bypass of modified nucleotides (translesion DNA synthesis, TLS); however, when TLS fails, replication forks stalled at lesions eventually result in more lethal effects, formation of double-stranded breaks (DSBs). Here we compared sensitivities to various compounds among mouse embryonic fibroblasts derived from wild-type and knock-out mice lacking one of the three Y-family TLS DNA polymerases (Polη, Polι, and Polκ) or all of them (TKO)...
November 26, 2017: DNA Repair
Marketa Tomkova, Michael McClellan, Skirmantas Kriaucionis, Benjamin Schuster-Böckler
Transitions of cytosine to thymine in CpG dinucleotides are the most frequent type of mutations observed in cancer. This increased mutability is commonly explained by the presence of 5-methylcytosine (5mC) and its spontaneous hydrolytic deamination into thymine. Here, we describe observations that question whether spontaneous deamination alone causes the elevated mutagenicity of 5mC. Tumours with somatic mutations in DNA mismatch-repair genes or in the proofreading domain of DNA polymerase ε (Pol ε) exhibit more 5mC to T transitions than would be expected, given the kinetics of hydrolytic deamination...
November 24, 2017: DNA Repair
Polly Gravells, James Neale, Emma Grant, Amit Nathubhai, Kate M Smith, Dominic I James, Helen E Bryant
Upon DNA binding the poly(ADP-ribose) polymerase family of enzymes (PARPs) add multiple ADP-ribose subunits to themselves and other acceptor proteins. Inhibitors of PARPs have become an exciting and real prospect for monotherapy and as sensitizers to ionising radiation (IR). The action of PARPs are reversed by poly(ADP-ribose) glycohydrolase (PARG). Until recently studies of PARG have been limited by the lack of an inhibitor. Here, a first in class, specific, and cell permeable PARG inhibitor, PDD00017273, is shown to radiosensitize...
November 22, 2017: DNA Repair
Flavia Zita Francies, Rosalind Wainwright, Janet Poole, Kim De Leeneer, Ilse Coene, Greet Wieme, Hélène A Poirel, Bénédicte Brichard, Stephanie Vermeulen, Anne Vral, Jacobus Slabbert, Kathleen Claes, Ans Baeyens
Fanconi Anaemia (FA) is an autosomal recessive disorder characterised by defects in DNA repair, associated with chromosomal instability and cellular hypersensitivity to DNA cross-linking agents such as mitomycin C (MMC). The FA repair pathway involves complex DNA repair mechanisms crucial for genomic stability. Deficiencies in DNA repair genes give rise to chromosomal radiosensitivity. FA patients have shown increased clinical radiosensitivity by exhibiting adverse normal tissue side-effects. The study aimed to investigate chromosomal radiosensitivity of homozygous and heterozygous carriers of FA mutations using three micronucleus (MN) assays...
November 8, 2017: DNA Repair
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
Alexey N Evdokimov, Alexandra Yu Tsidulko, Alexander V Popov, Yury N Vorobiev, Alexander A Lomzov, Lyudmila S Koroleva, Vladimir N Silnikov, Irina O Petruseva, Olga I Lavrik
Mammalian nucleotide excision repair (NER) eliminates the broadest diversity of bulky lesions from DNA with wide specificity. However, the double incision efficiency for structurally different adducts can vary over several orders of magnitude. Therefore, great attention is drawn to the question of the relationship among structural properties of bulky DNA lesions and the rate of damage elimination. This paper studies the properties of several structurally diverse synthetic (model) DNAs containing bulky modifications...
November 2, 2017: DNA Repair
Brett A Kaufman, Bennett Van Houten
The mitochondrial genome is a matrilineally inherited DNA that encodes numerous essential subunits of the respiratory chain in all metazoans. As such mitochondrial DNA (mtDNA) sequence integrity is vital to organismal survival, but it has a limited cadre of DNA repair activities, primarily base excision repair (BER). We have known that the mtDNA is significantly oxidized by both endogenous and exogenous sources, but this does not lead to the expected preferential formation of transversion mutations, which suggest a robust base excision repair (BER) system...
December 2017: DNA Repair
Lihong Zhang, Yang Peng, Ivan P Uray, Jianfeng Shen, Lulu Wang, Xiangdong Peng, Powel H Brown, Wei Tu, Guang Peng
Investigation of natural products is an attractive strategy to identify novel compounds for cancer prevention and treatment. Numerous studies have shown the efficacy and safety of natural products, and they have been widely used as alternative treatments for a wide range of illnesses, including cancers. However, it remains unknown whether natural products affect homologous recombination (HR)-mediated DNA repair and whether these compounds can be used as sensitizers with minimal toxicity to improve patients' responses to radiation therapy, a mainstay of treatment for many human cancers...
December 2017: DNA Repair
Rajendra Prasad, Melike Çağlayan, Da-Peng Dai, Cristina A Nadalutti, Ming-Lang Zhao, Natalie R Gassman, Agnes K Janoshazi, Donna F Stefanick, Julie K Horton, Rachel Krasich, Matthew J Longley, William C Copeland, Jack D Griffith, Samuel H Wilson
Mitochondrial genome integrity is fundamental to mammalian cell viability. Since mitochondrial DNA is constantly under attack from oxygen radicals released during ATP production, DNA repair is vital in removing oxidatively generated lesions in mitochondrial DNA, but the presence of a strong base excision repair system has not been demonstrated. Here, we addressed the presence of such a system in mammalian mitochondria involving the primary base lesion repair enzyme DNA polymerase (pol) β. Pol β was localized to mammalian mitochondria by electron microscopic-immunogold staining, immunofluorescence co-localization and biochemical experiments...
December 2017: DNA Repair
Michelle C Silva, Katie E Bryan, Milagros D Morrical, April M Averill, Julie Dragon, Adrian P Wiegmans, Scott W Morrical
The human RAD51 recombinase possesses DNA pairing and strand exchange activities that are essential for the error-free, homology-directed repair of DNA double-strand breaks. The recombination activities of RAD51 are activated upon its assembly into presynaptic filaments on single-stranded DNA at resected DSB ends. Defects in filament assembly caused by mutations in RAD51 or its regulators such as BRCA2 are associated with human cancer. Here we describe two novel RAD51 missense variants located in the multimerization/BRCA2 binding region of RAD51...
December 2017: DNA Repair
Julie K Horton, Donna F Stefanick, Ming-Lang Zhao, Agnes K Janoshazi, Natalie R Gassman, Hannah J Seddon, Samuel H Wilson
Repair of DNA-protein crosslinks and oxidatively damaged DNA base lesions generates intermediates with nicks or gaps with abnormal and blocked 3'-phosphate and 5'-OH ends that prevent the activity of DNA polymerases and ligases. End cleaning in mammalian cells by Tdp1 and PNKP produces the conventional 3'-OH and 5'-phosphate DNA ends suitable for completion of repair. This repair function of PNKP is facilitated by its binding to the scaffold protein XRCC1, and phosphorylation of XRCC1 by CK2 at several consensus sites enables PNKP binding and recruitment to DNA damage...
December 2017: DNA Repair
Phillip R Musich, Zhengke Li, Steven M Shell, Yue Zou
No abstract text is available yet for this article.
December 2017: DNA Repair
Jing Li, Matthew Summerlin, Karin C Nitiss, John L Nitiss, Leslyn A Hanakahi
Tyrosyl-DNA phosphodiesterase 1 (TDP1) can remove a wide variety of 3' and 5' terminal DNA adducts. Genetic studies in yeast identified TDP1 as a regulator of non-homologous end joining (NHEJ) fidelity in the repair of double-strand breaks (DSBs) lacking terminal adducts. In this communication, we show that TDP1 plays an important role in joining cohesive DSBs in human cells. To investigate the role of TDP1 in NHEJ in live human cells we used CRISPR/cas9 to produce TDP1-knockout (TDP1-KO) HEK-293 cells. As expected, human TDP1-KO cells were highly sensitive to topoisomerase poisons and ionizing radiation...
December 2017: DNA Repair
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