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DNA Repair

Jinyu Wang, Haitao Zhang, Mohammed Al Shibar, Belinda Willard, Alo Ray, Kurt W Runge
Telomeres, the ends of eukaryotic chromosomes, consist of repetitive DNA sequences and their bound proteins that protect the end from the DNA damage response. Short telomeres with fewer repeats are preferentially elongated by telomerase. Tel1, the yeast homolog of human ATM kinase, is preferentially recruited to short telomeres and Tel1 kinase activity is required for telomere elongation. Rif1, a telomere-binding protein, negatively regulates telomere length by forming a complex with two other telomere binding proteins, Rap1 and Rif2, to block telomerase recruitment...
March 7, 2018: DNA Repair
Pingping Jia, Weihang Chai
Genome instability gives rise to cancer. MLH1, commonly known for its important role in mismatch repair (MMR), DNA damage signaling and double-strand break (DSB) repair, safeguards genome stability. Recently we have reported a novel role of MLH1 in preventing aberrant formation of interstitial telomeric sequences (ITSs) at intra-chromosomal regions. Deficiency in MLH1, in particular its N-terminus, leads to an increase of ITSs. Here, we identify that the ATPase activity in the MLH1 N-terminal domain is important for suppressing the formation of ITSs...
March 7, 2018: DNA Repair
Nidhi Sharma, Srinivas Chakravarthy, Matthew J Longley, William C Copeland, Aishwarya Prakash
The 16.5 kb mitochondrial genome is subjected to damage from reactive oxygen species (ROS) generated in the cell during normal cellular metabolism and external sources such as ionizing radiation and ultraviolet light. ROS cause harmful damage to DNA bases that could result in mutagenesis and various diseases, if not properly repaired. The base excision repair (BER) pathway is the primary pathway involved in maintaining the integrity of mtDNA. Several enzymes that partake in BER within the nucleus have also been identified in the mitochondria...
March 6, 2018: DNA Repair
Teresa Morales-Ruiz, Álvaro C Romero-Valenzuela, Vanessa M Vázquez-Grande, Teresa Roldán-Arjona, Rafael R Ariza, Dolores Córdoba-Cañero
Base excision repair (BER) is a major defense pathway against spontaneous DNA damage. This multistep process is initiated by DNA glycosylases that recognise and excise the damaged base, and proceeds by the concerted action of additional proteins that perform incision of the abasic site, gap filling and ligation. BER has been extensively studied in bacteria, yeasts and animals. Although knowledge of this pathway in land plants is increasing, there are no reports detecting BER in algae. We describe here an experimental in vitro system allowing the specific analysis of BER in the model alga Chlamydomonas reinhardtii...
March 5, 2018: DNA Repair
Carlos H Trasviña-Arenas, Noe Baruch-Torres, Francisco J Cordoba-Andrade, Víctor M Ayala-García, Paola L García-Medel, Corina Díaz-Quezada, Antolín Peralta-Castro, José Juan Ordaz-Ortiz, Luis G Brieba
Plant mitochondrial and chloroplast genomes encode essential proteins for oxidative phosphorylation and photosynthesis. For proper cellular function, plant organelles must ensure genome integrity. Although plant organelles repair damaged DNA using the multi-enzyme Base Excision Repair (BER) pathway, the details of this pathway in plant organelles are largely unknown. The initial enzymatic steps in BER produce a 5'-deoxyribose phosphate (5'-dRP) moiety that must be removed to allow DNA ligation and in plant organelles, the enzymes responsible for the removal of a 5'-dRP group are unknown...
February 27, 2018: DNA Repair
Marketa Tomkova, Michael McClellan, Skirmantas Kriaucionis, Benjamin Schuster-Böckler
No abstract text is available yet for this article.
February 27, 2018: DNA Repair
John James Tello Cajiao, Mario Pietro Carante, Mario Antonio Bernal Rodriguez, Francesca Ballarini
It is widely accepted that, in chromosome-aberration induction, the (mis-)rejoining probability of two chromosome fragments depends on their initial distance, r. However, several aspects of these "proximity effects" need to be clarified, also considering that they can vary with radiation quality, cell type and dose. A previous work performed by the BIANCA (BIophysical ANalysis of Cell death and chromosome Aberrations) biophysical model has suggested that, in human lymphocytes and fibroblasts exposed to low-LET radiation, an exponential function of the form exp(-r/r0 ), which is consistent with free-end (confined) diffusion, describes proximity effects better than a Gaussian function...
February 22, 2018: DNA Repair
Timsi Rao, Simonne Longerich, Weixing Zhao, Hideki Aihara, Patrick Sung, Yong Xiong
Fanconi-associated nuclease 1 (FAN1) removes interstrand DNA crosslinks (ICLs) through its DNA flap endonuclease and exonuclease activities. Crystal structures of human and bacterial FAN1 bound to a DNA flap have been solved. The Pseudomonas aeruginosa bacterial FAN1 and human FAN1 (hFAN1) missing a flexible loop are monomeric, while intact hFAN1 is homo-dimeric in structure. Importantly, the monomeric and dimeric forms of FAN1 exhibit very different DNA binding modes. Here, we interrogate the functional differences between monomeric and dimeric forms of FAN1 and provide an explanation for the discrepancy in oligomeric state between the two hFAN1 structures...
February 21, 2018: DNA Repair
Kang-Yi Su, Liang-In Lin, Steven D Goodman, Rong-Syuan Yen, Cho-Yuan Wu, Wei-Chen Chang, Ya-Chien Yang, Wern-Cherng Cheng, Woei-Horng Fang
Deamination of adenine can occur spontaneously under physiological conditions to generate the highly mutagenic lesion, deoxyinosine (hypoxanthine deoxyribonucleotide, dI). In DNA, dI preferably pairs with cytosine rather than thymine and results in A:T to G:C transition mutations after DNA replication. The deamination of adenine is enhanced by ROS from exposure of DNA to ionizing radiation, UV light, nitrous acid, or heat. In Escherichia coli, dI repair is initiated by endonuclease V (endo V; nfi gene product) nicking but a complete repair mechanism has yet to be elucidated...
February 17, 2018: DNA Repair
Julie K Horton, Donna F Stefanick, Melike Çağlayan, Ming-Lang Zhao, Agnes K Janoshazi, Rajendra Prasad, Natalie R Gassman, Samuel H Wilson
Aprataxin (APTX) is a DNA-adenylate hydrolase that removes 5'-AMP blocking groups from abortive ligation repair intermediates. XRCC1, a multi-domain protein without catalytic activity, interacts with a number of known repair proteins including APTX, modulating and coordinating the various steps of DNA repair. CK2-phosphorylation of XRCC1 is thought to be crucial for its interaction with the FHA domain of APTX. In light of conflicting reports, the importance of XRCC1 phosphorylation and APTX function is not clear...
February 15, 2018: DNA Repair
Paul Jowsey, Nicholas A Morrice, C James Hastie, Hilary MacLauchlan, Rachel Toth, John Rouse
No abstract text is available yet for this article.
February 12, 2018: DNA Repair
Mei-Shiue Kuo, Julien Adam, Nicolas Dorvault, Angélique Robin, Luc Friboulet, Jean-Charles Soria, Ken A Olaussen
ERCC1/XPF endonuclease plays an important role in multiple DNA repair pathways and stands as a potential prognostic and predictive biomarker for cisplatin-based chemotherapy. Four distinct ERCC1 isoforms arising from alternative splicing have been described (201, 202, 203 and 204) but only the 202 isoform is functional in DNA excision repair, when interacting with its obligate partner XPF. Currently, there is no tool to assess specifically the expression of ERCC1-202 due to high sequence homology between the four isoforms...
February 11, 2018: DNA Repair
Olga A Kladova, Milena Bazlekowa-Karaban, Sonia Baconnais, Olivier Piétrement, Alexander A Ishchenko, Bakhyt T Matkarimov, Danila A Iakovlev, Andrey Vasenko, Olga S Fedorova, Eric Le Cam, Barbara Tudek, Nikita A Kuznetsov, Murat Saparbaev
The base excision repair (BER) pathway consists of sequential action of DNA glycosylase and apurinic/apyrimidinic (AP) endonuclease necessary to remove a damaged base and generate a single-strand break in duplex DNA. Human multifunctional AP endonuclease 1 (APE1, a.k.a. APEX1, HAP-1, or Ref-1) plays essential roles in BER by acting downstream of DNA glycosylases to incise a DNA duplex at AP sites and remove 3'-blocking sugar moieties at DNA strand breaks. Human 8-oxoguanine-DNA glycosylase (OGG1), methyl-CpG-binding domain 4 (MBD4, a...
February 11, 2018: DNA Repair
Laura J Eccles, Andrew C Bell, Simon N Powell
When Fanconi Anemia (FA) proteins were depleted in human U2OS cells with integrated DNA repair reporters, we observed decreases in homologous recombination (HR), decreases in mutagenic non-homologous end joining (m-NHEJ) and increases in canonical NHEJ, which was independently confirmed by measuring V(D)J recombination. Furthermore, depletion of FA proteins resulted in reduced HR protein foci and increased NHEJ protein recruitment to replication-associated DSBs, consistent with our observation that the use of canonical NHEJ increases after depletion of FA proteins in cycling cells...
February 10, 2018: DNA Repair
Milorad Kojic, Mira Milisavljevic, William K Holloman
Cells maintain a small arsenal of resolving functions to process and eliminate complex DNA intermediates that result as a consequence of homologous recombination and distressed replication. Ordinarily the homologous recombination system serves as a high-fidelity mechanism to restore the integrity of a damaged genome, but in the absence of the appropriate resolving function it can turn DNA intermediates resulting from replication stress into pathological forms that are toxic to cells. Here we have investigated how the nucleases Mus81 and Gen1 and the helicase Blm contribute to survival after DNA damage or replication stress in Ustilago maydis cells with crippled yet homologous recombination-proficient forms of Brh2, the BRCA2 ortholog and primary Rad51 mediator...
February 2, 2018: DNA Repair
Phillip R Musich, Zhengke Li, Steven M Shell, Yue Zou
No abstract text is available yet for this article.
February 2, 2018: DNA Repair
Liangwen Chen, Huangqi Tang, Yan Du, Zhangyu Dai, Ting Wang, Lijun Wu, Libin Zhou, Po Bian
Heavy-ion radiation has attracted extensive attention as an effective cancer therapy because of the varying energy deposition along its track and its high cell-killing effect. Reproductive cell death (RCD), also known as clonogenic death, is an important mode of death of the cancer cells after radiotherapy. Although RCD induced by heavy-ion irradiation with various linear energy transfers has been demonstrated using clonogenic assay in vitro, little is known about the distribution of RCD across the range of heavy-ion irradiation at the level of whole organisms...
February 1, 2018: DNA Repair
Fabrizia Carofiglio, Esther Sleddens-Linkels, Evelyne Wassenaar, Akiko Inagaki, Wiggert A van Cappellen, J Anton Grootegoed, Attila Toth, Willy M Baarends
Repair of SPO11-dependent DNA double-strand breaks (DSBs) via homologous recombination (HR) is essential for stable homologous chromosome pairing and synapsis during meiotic prophase. Here, we induced radiation-induced DSBs to study meiotic recombination and homologous chromosome pairing in mouse meiocytes in the absence of SPO11 activity (Spo11YF/YF model), and in the absence of both SPO11 and HORMAD1 (Spo11/Hormad1 dko). Within 30 min after 5 Gy irradiation of Spo11YF/YF mice, 140-160 DSB repair foci were detected, which specifically localized to the synaptonemal complex axes...
January 31, 2018: DNA Repair
Miriam Dormeyer, Sabine Lentes, Patrick Ballin, Markus Wilkens, Stefan Klumpp, Dietrich Kohlheyer, Lorena Stannek, Alexander Grünberger, Fabian M Commichau
Mutations are crucial for the emergence and evolution of proteins with novel functions, and thus for the diversity of life. Tandem repeats (TRs) are mutational hot spots that are present in the genomes of all organisms. Understanding the molecular mechanism underlying TR mutagenesis at the level of single cells requires the development of mutation reporter systems. Here, we present a mutation reporter system that is suitable to visualize mutagenesis of TRs occurring in single cells of the Gram-positive model bacterium Bacillus subtilis using microfluidic single-cell cultivation...
January 23, 2018: DNA Repair
Lisa N Chesner, Colin Campbell
DNA-protein crosslinks (DPCs) are complex DNA lesions that induce mutagenesis and cell death. DPCs are created by common antitumor drugs, reactive oxygen species, and endogenous aldehydes. Since these agents create other types of DNA damage in addition to DPCs, identification of the mechanisms of DPC repair is challenging. In this study, we created plasmid substrates containing site-specific DPC lesions, as well as plasmids harboring lesions that are selectively repaired by the base excision or nucleotide excision repair (NER) pathways...
January 9, 2018: DNA Repair
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