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DNA Repair

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https://www.readbyqxmd.com/read/28089177/cell-cycle-dependent-positive-and-negative-functions-of-fun30-chromatin-remodeler-in-dna-damage-response
#1
Jasmine Siler, Bowen Xia, Carina Wong, Morgan Kath, Xin Bi
The evolutionally conserved Fun30 chromatin remodeler in Saccharomyces cerevisiae has been shown to contribute to cellular resistance to genotoxic stress inflicted by camptothecin (CPT), methyl methanesulfonate (MMS) and hydroxyurea (HU). Fun30 aids in extensive DNA resection of DNA double stranded break (DSB) ends, which is thought to underlie its role in CPT-resistance. How Fun30 promotes MMS- or HU-resistance has not been resolved. Interestingly, we have recently found Fun30 to also play a negative role in cellular tolerance to MMS and HU in the absence of the Rad5-dependent DNA damage tolerance pathway...
January 5, 2017: DNA Repair
https://www.readbyqxmd.com/read/28077248/alternative-splicing-at-exon-2-results-in-the-loss-of-the-catalytic-activity-of-mouse-dna-polymerase-iota-in-vitro
#2
Konstantin Y Kazachenko, Nataliya A Miropolskaya, Leonid V Gening, Vyacheslav Z Tarantul, Alena V Makarova
Y-family DNA polymerase iota (Pol ι) possesses both DNA polymerase and dRP lyase activities and was suggested to be involved in DNA translesion synthesis and base excision repair in mammals. The 129 strain of mice and its derivatives have a natural nonsense codon mutation in the second exon of the Pol ι gene resulting in truncation of the Pol ι protein. These mice were widely used as a Pol ι-null model for in vivo studies of the Pol ι function. However whether 129-derived strains of mice are fully deficient in the Pol ι functions was a subject of discussion since Pol ι mRNA undergoes alternative splicing at exon 2...
January 4, 2017: DNA Repair
https://www.readbyqxmd.com/read/28073635/pcna-dependent-cellular-activities-tolerate-dramatic-perturbations-in-pcna-client-interactions
#3
Rosemary H C Wilson, Antonio J Biasutto, Lihao Wang, Roman Fischer, Emma L Baple, Andrew H Crosby, Erika J Mancini, Catherine M Green
Proliferating cell nuclear antigen (PCNA) is an essential cofactor for DNA replication and repair, recruiting multiple proteins to their sites of action. We examined the effects of the PCNA(S228I) mutation that causes PCNA-associated DNA repair disorder (PARD). Cells from individuals affected by PARD are sensitive to the PCNA inhibitors T3 and T2AA, showing that the S228I mutation has consequences for undamaged cells. Analysis of the binding between PCNA and PCNA-interacting proteins (PIPs) shows that the S228I change dramatically impairs the majority of these interactions, including that of Cdt1, DNMT1, PolD3(p66) and PolD4(p12)...
December 31, 2016: DNA Repair
https://www.readbyqxmd.com/read/28087249/nick-initiated-homologous-recombination-protecting-the-genome-one-strand-at-a-time
#4
REVIEW
Lianne E M Vriend, Przemek M Krawczyk
Homologous recombination (HR) is an essential, widely conserved mechanism that utilizes a template for accurate repair of DNA breaks. Some early HR models, developed over five decades ago, anticipated single-strand breaks (nicks) as initiating lesions. Subsequent studies favored a more double-strand break (DSB)-centered view of HR initiation and at present this pathway is primarily considered to be associated with DSB repair. However, mounting evidence suggests that nicks can indeed initiate HR directly, without first being converted to DSBs...
December 29, 2016: DNA Repair
https://www.readbyqxmd.com/read/28082021/somatic-hypermutation-of-immunoglobulin-genes-in-rad18-knockout-mice
#5
Takeyuki Shimizu, Satoshi Tateishi, Yuki Tanoue, Takachika Azuma, Haruo Ohmori
Somatic hypermutation (SHM) of immunoglobulin (Ig) genes is triggered by the activity of activation-induced cytidine deaminase (AID). AID induces DNA lesions in variable regions of Ig genes, and error-prone DNA repair mechanisms initiated in response to these lesions introduce the mutations that characterize SHM. Error-prone DNA repair in SHM is proposed to be mediated by low-fidelity DNA polymerases such as those that mediate trans-lesion synthesis (TLS); however, the mechanism by which these enzymes are recruited to AID-induced lesions remains unclear...
December 28, 2016: DNA Repair
https://www.readbyqxmd.com/read/28063664/hesperetin-etoposide-combinations-induce-cytotoxicity-in-u2os-cells-implications-on-therapeutic-developments-for-osteosarcoma
#6
Laura Coutinho, Helena Oliveira, Ana Rita Pacheco, Luis Almeida, Francisco Pimentel, Conceição Santos, José Miguel P Ferreira de Oliveira
Osteosarcoma chemotherapy has improved survival rates, however, chemoresistance and drug toxicity still limit therapy. Drug combinations may overcome these limitations by allowing fewer chemoresistant cells to survive. The aim of this study was to evaluate the cytotoxic potential of hesperetin to osteosarcoma and to analyze the cell cycle effects of combinations of hesperetin with chemotherapeutic agents. For this, the U2OS human osteosarcoma cell line was exposed to hesperetin or hesperetin combined with etoposide or doxorubicin in defined proportions...
December 28, 2016: DNA Repair
https://www.readbyqxmd.com/read/28065385/processing-of-the-abasic-sites-clustered-with-the-benzo-a-pyrene-adducts-by-the-base-excision-repair-enzymes
#7
Lidia V Starostenko, Nadejda I Rechkunova, Natalia A Lebedeva, Alexander A Lomzov, Vladimir V Koval, Olga I Lavrik
The major enzyme in eukaryotic cells that catalyzes the cleavage of apurinic/apyrimidinic (AP or abasic) sites is AP endonuclease 1 (APE1) that cleaves the phosphodiester bond on the 5'-side of AP sites. We found that the efficiency of AP site cleavage by APE1 was affected by the benzo[a]pyrenyl-DNA adduct (BPDE-dG) in the opposite strand. AP sites directly opposite of the modified dG or shifted toward the 5' direction were hydrolyzed by APE1 with an efficiency moderately lower than the AP site in the control DNA duplex, whereas AP sites shifted toward the 3' direction were hydrolyzed significantly less efficiently...
December 27, 2016: DNA Repair
https://www.readbyqxmd.com/read/28077247/mouse-dna-polymerase-%C3%AE-lacking-the-forty-two-amino-acids-encoded-by-exon-2-is-catalytically-inactive-in-vitro
#8
Ekaterina G Frank, John P McDonald, Wei Yang, Roger Woodgate
In 2003, we reported that 129-derived strains of mice carry a naturally occurring nonsense mutation at codon 27 of the Poli gene that would produce a polι peptide of just 26 amino acids, rather then the full-length 717 amino acid wild-type polymerase. In support of the genomic analysis, no polι protein was detected in testes extracts from 129X1/SvJmice, where wild-type polι is normally highly expressed. The early truncation in polι occurs before any structural domains of the polymerase are synthesized and as a consequence, we reasoned that 129-derived strains of mice should be considered as functionally defective in polι activity...
December 21, 2016: DNA Repair
https://www.readbyqxmd.com/read/28017527/dna-damage-repair-monitoring-and-epigenetic-dna-methylation-changes-in-seedlings-of-chernobyl-soybeans
#9
Mariyana Georgieva, Namik M Rashydov, Martin Hajduch
This pilot study was carried out to assess the effect of radio-contaminated Chernobyl environment on plant genome integrity 27 years after the accident. For this purpose, nuclei were isolated from root tips of the soybean seedlings harvested from plants grown in the Chernobyl area for seven generations. Neutral, neutral-alkaline, and methylation-sensitive comet assays were performed to evaluate the induction and repair of primary DNA damage and the epigenetic contribution to stress adaptation mechanisms. An increased level of single and double strand breaks in the radio-contaminated Chernobyl seedlings at the stage of primary root development was detected in comparison to the controls...
December 16, 2016: DNA Repair
https://www.readbyqxmd.com/read/28034630/defect-of-fe-s-cluster-binding-by-dna-polymerase-%C3%AE-in-yeast-suppresses-uv-induced-mutagenesis-but-enhances-dna-polymerase-%C3%AE-dependent-spontaneous-mutagenesis
#10
E I Stepchenkova, E R Tarakhovskaya, H M Siebler, Y I Pavlov
Eukaryotic genomes are duplicated by a complex machinery, utilizing high fidelity replicative B-family DNA polymerases (pols) α, δ and ε. Specialized error-prone pol ζ, the fourth B-family member, is recruited when DNA synthesis by the accurate trio is impeded by replication stress or DNA damage. The damage tolerance mechanism dependent on pol ζ prevents DNA/genome instability and cell death at the expense of increased mutation rates. The pol switches occurring during this specialized replication are not fully understood...
December 9, 2016: DNA Repair
https://www.readbyqxmd.com/read/27964836/non-heme-dioxygenases-in-tumor-hypoxia-they-re-all-bound-with-the-same-fate
#11
REVIEW
Roy Anindya
Tumor tissues are known to harbor hypoxic areas. The hypoxic microenvironment promotes angiogenesis. Hypoxic tumor cells also manifest genome instability. DNA damage repair pathways, such as double-strand break repair, mismatch repair and base excision repair are known to be altered during hypoxia. This review is focused on the non-heme Fe(II) and 2-oxoglutarate-dependent dioxygenases which are involved in repair of DNA alkylation adducts. Activities of these DNA repair enzymes are completely oxygen-dependent and little information is available about inhibition of these enzymes during hypoxia...
December 5, 2016: DNA Repair
https://www.readbyqxmd.com/read/27989484/significant-impact-of-divalent-metal-ions-on-the-fidelity-sugar-selectivity-and-drug-incorporation-efficiency-of-human-primpol
#12
E John Tokarsky, Petra C Wallenmeyer, Kenneth K Phi, Zucai Suo
Human PrimPol is a recently discovered bifunctional enzyme that displays DNA template-directed primase and polymerase activities. PrimPol has been implicated in nuclear and mitochondrial DNA replication fork progression and restart as well as DNA lesion bypass. Published evidence suggests that PrimPol is a Mn(2+)-dependent enzyme as it shows significantly improved primase and polymerase activities when binding Mn(2+), rather than Mg(2+), as a divalent metal ion cofactor. Consistently, our fluorescence anisotropy assays determined that PrimPol binds to a primer/template DNA substrate with affinities of 29 and 979nM in the presence of Mn(2+) and Mg(2+), respectively...
November 25, 2016: DNA Repair
https://www.readbyqxmd.com/read/27908669/cellular-responses-to-replication-stress-implications-in-cancer-biology-and-therapy
#13
REVIEW
Hui-Ju Hsieh, Guang Peng
DNA replication is essential for cell proliferation. Any obstacles during replication cause replication stress, which may lead to genomic instability and cancer formation. In this review, we summarize the physiological DNA replication process and the normal cellular response to replication stress. We also outline specialized therapies in clinical trials based on current knowledge and future perspectives in the field.
November 22, 2016: DNA Repair
https://www.readbyqxmd.com/read/27894903/structural-basis-of-accurate-replication-beyond-a-bulky-major-benzo-a-pyrene-adduct-by-human-dna-polymerase-kappa
#14
Vikash Jha, Hong Ling
Human Y-family DNA polymerase kappa (polκ) is specialized to bypass bulky lesions in DNA in an error-free way, thus protecting cells from carcinogenic bulky DNA adducts. Benzo[a]pyrene (BP) is one of the most ubiquitous polycyclic aromatic hydrocarbons and an environmental carcinogen. BP covalently modifies DNA and generates mutagenic, bulky adducts. The major BP adduct formed in cells is 10S (+)-trans-anti-BP-N(2)-dG adduct (BP-dG), which is associated with cancer. The molecular mechanism of how polκ replicates BP-dG accurately is not clear...
November 19, 2016: DNA Repair
https://www.readbyqxmd.com/read/27838458/the-dna-binding-box-of-human-spartan-contributes-to-the-targeting-of-pol%C3%AE-to-dna-damage-sites
#15
Agnes Toth, Lili Hegedus, Szilvia Juhasz, Lajos Haracska, Peter Burkovics
Inappropriate repair of UV-induced DNA damage results in human diseases such as Xeroderma pigmentosum (XP), which is associated with an extremely high risk of skin cancer. A variant form of XP is caused by the absence of Polη, which is normally able to bypass UV-induced DNA lesions in an error-free manner. However, Polη is highly error prone when replicating undamaged DNA and, thus, the regulation of the proper targeting of Polη is crucial for the prevention of mutagenesis and UV-induced cancer formation...
October 29, 2016: DNA Repair
https://www.readbyqxmd.com/read/27836324/the-major-arabidopsis-thaliana-apurinic-apyrimidinic-endonuclease-arp-is-involved-in-the-plant-nucleotide-incision-repair-pathway
#16
Zhiger Akishev, Sabira Taipakova, Botagoz Joldybayeva, Caroline Zutterling, Izat Smekenov, Alexander A Ishchenko, Dmitry O Zharkov, Amangeldy K Bissenbaev, Murat Saparbaev
Apurinic/apyrimidinic (AP) endonucleases are important DNA repair enzymes involved in two overlapping pathways: DNA glycosylase-initiated base excision (BER) and AP endonuclease-initiated nucleotide incision repair (NIR). In the BER pathway, AP endonucleases cleave DNA at AP sites and 3'-blocking moieties generated by DNA glycosylases, whereas in NIR, the same AP endonucleases incise DNA 5' to a wide variety of oxidized bases. The flowering plant Arabidopsis thaliana contains three genes encoding homologues of major human AP endonuclease 1 (APE1): Arp, Ape1L and Ape2...
October 29, 2016: DNA Repair
https://www.readbyqxmd.com/read/27825743/quantification-and-genome-wide-mapping-of-dna-double-strand-breaks
#17
Marie-Chantal Grégoire, Julien Massonneau, Frédéric Leduc, Mélina Arguin, Marc-André Brazeau, Guylain Boissonneault
DNA double-strand breaks (DSBs) represent a major threat to the genetic integrity of the cell. Knowing both their genome-wide distribution and number is important for a better assessment of genotoxicity at a molecular level. Available methods may have underestimated the extent of DSBs as they are based on markers specific to those undergoing active repair or may not be adapted for the large diversity of naturally occurring DNA ends. We have established conditions for an efficient first step of DNA nick and gap repair (NGR) allowing specific determination of DSBs by end labeling with terminal transferase...
October 29, 2016: DNA Repair
https://www.readbyqxmd.com/read/27818081/enhanced-sensitivity-of-neil1-mice-to-chronic-uvb-exposure
#18
Marcus J Calkins, Vladimir Vartanian, Nichole Owen, Guldal Kirkali, Pawel Jaruga, Miral Dizdaroglu, Amanda K McCullough, R Stephen Lloyd
Oxidative stress and reactive oxygen species (ROS)-induced DNA base damage are thought to be central mediators of UV-induced carcinogenesis and skin aging. However, increased steady-state levels of ROS-induced DNA base damage have not been reported after chronic UV exposure. Accumulation of ROS-induced DNA base damage is governed by rates of lesion formation and repair. Repair is generally performed by Base Excision Repair (BER), which is initiated by DNA glycosylases, such as 8-oxoguanine glycosylase and Nei-Endonuclease VIII-Like 1 (NEIL1)...
October 28, 2016: DNA Repair
https://www.readbyqxmd.com/read/27865706/age-related-length-variability-of-polymorphic-cag-repeats
#19
Monica Sanchez-Contreras, Fernando Cardozo-Pelaez
Somatic instability of CAG repeats has been associated with the clinical progression of CAG repeat diseases. Aging and DNA repair processes influence the somatic stability of CAG repeat in disease and in mouse models. However, most of the studies have focused on genetically engineered transgenic repeats and little is known about the stability of naturally polymorphic CAG repeats. To study whether age and/or DNA repair activity have an effect on the somatic stability of CAG repeats, we analyzed variations of the length of naturally polymorphic CAG repeats in the striatum of young and aged WT and ogg1 KO mice...
January 2017: DNA Repair
https://www.readbyqxmd.com/read/27842255/differences-in-the-recruitment-of-dna-repair-proteins-at-subtelomeric-and-interstitial-i-scei-endonuclease-induced-dna-double-strand-breaks
#20
Bárbara Alcaraz Silva, Trevor J Jones, John P Murnane
Telomeres are nucleoprotein structures that are required to protect chromosome ends. Dysfunctional telomeres are recognized as DNA double-strand breaks (DSBs), and elicit the activation of a DNA damage response (DDR). We have previously reported that DSBs near telomeres are poorly repaired, resulting in a high frequency of large deletions and gross chromosome rearrangements (GCRs). Our previous genetic studies have demonstrated that this sensitivity of telomeric regions to DSBs is a result of excessive processing...
January 2017: DNA Repair
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