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https://www.readbyqxmd.com/read/28713155/hypoxia-induces-universal-but-differential-drug-resistance-and-impairs-anticancer-mechanisms-of-5-fluorouracil-in-hepatoma-cells
#1
Jing-Qiu Li, Xian Wu, Lu Gan, Xiang-Liang Yang, Ze-Hong Miao
Hepatocellular carcinoma (HCC) is one of the most refractory cancers. The mechanisms by which hypoxia further aggravates therapeutic responses of advanced HCC to anticancer drugs remain to be clarified. Here, we report that hypoxia (1% O2) caused 2.55-489.7-fold resistance to 6 anticancer drugs (sorafenib, 5-fluorouracil [5-FU], gemcitabine, cisplatin, adriamycin and 6-thioguanine) in 3 HCC cell lines (BEL-7402, HepG2 and SMMC-7721). Among the 6 drugs, sorafenib, the sole one approved for HCC therapy, inhibited proliferation with little influence from hypoxia and displayed the smallest variation among the 3 HCC cell lines tested...
July 17, 2017: Acta Pharmacologica Sinica
https://www.readbyqxmd.com/read/28703879/precarious-maintenance-of-simple-dna-repeats-in-eukaryotes
#2
REVIEW
Alexander J Neil, Jane C Kim, Sergei M Mirkin
In this review, we discuss how two evolutionarily conserved pathways at the interface of DNA replication and repair, template switching and break-induced replication, lead to the deleterious large-scale expansion of trinucleotide DNA repeats that cause numerous hereditary diseases. We highlight that these pathways, which originated in prokaryotes, may be subsequently hijacked to maintain long DNA microsatellites in eukaryotes. We suggest that the negative mutagenic outcomes of these pathways, exemplified by repeat expansion diseases, are likely outweighed by their positive role in maintaining functional repetitive regions of the genome such as telomeres and centromeres...
July 13, 2017: BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology
https://www.readbyqxmd.com/read/28696814/ddx19-links-mrna-nuclear-export-with-progression-of-transcription-and-replication-and-suppresses-genomic-instability-upon-dna-damage-in-proliferating-cells
#3
Dana Hodroj, Kamar Serhal, Domenico Maiorano
The DEAD-box Helicase 19 (Ddx19) gene codes for an RNA helicase involved in both messenger RNA (mRNA) export from the nucleus into the cytoplasm and in mRNA translation. In unperturbed cells, Ddx19 localizes in the cytoplasm and at the cytoplasmic face of the nuclear pore. Here we review recent findings related to an additional Ddx19 function in the nucleus in resolving RNA:DNA hybrids (R-loops) generated during collision between transcription and replication, and upon DNA damage. Activation of a DNA damage response pathway dependent upon the ATR kinase, a major regulator of replication fork progression, stimulates translocation of the Ddx19 protein from the cytoplasm into the nucleus...
July 11, 2017: Nucleus
https://www.readbyqxmd.com/read/28676700/the-multifaceted-roles-of-parp1-in-dna-repair-and-chromatin-remodelling
#4
REVIEW
Arnab Ray Chaudhuri, André Nussenzweig
Cells are exposed to various endogenous and exogenous insults that induce DNA damage, which, if unrepaired, impairs genome integrity and leads to the development of various diseases, including cancer. Recent evidence has implicated poly(ADP-ribose) polymerase 1 (PARP1) in various DNA repair pathways and in the maintenance of genomic stability. The inhibition of PARP1 is therefore being exploited clinically for the treatment of various cancers, which include DNA repair-deficient ovarian, breast and prostate cancers...
July 5, 2017: Nature Reviews. Molecular Cell Biology
https://www.readbyqxmd.com/read/28645381/examining-dna-double-strand-break-repair-in-a-cell-cycle-dependent-manner
#5
Janapriya Saha, Shih-Ya Wang, Anthony J Davis
DNA double-strand breaks (DSBs) are deleterious DNA lesions that must be properly repaired to maintain genome stability. Agents, generated both exogenously (environmental radiation, dental X-rays, etc.) and endogenously (reactive oxygen species, DNA replication, V(D)J recombination, etc.), induce numerous DSBs every day. To counter these DSBs, there are two major repair pathways in mammalian cells, nonhomologous end joining (NHEJ) and homologous recombination (HR). NHEJ directly mediates the religation of the broken DNA molecule and is active in all phases of the cell cycle...
2017: Methods in Enzymology
https://www.readbyqxmd.com/read/28631426/hsp90%C3%AE-regulates-atm-and-nbn-functions-in-sensing-and-repair-of-dna-double-strand-breaks
#6
Rosa Pennisi, Antonio Antoccia, Stefano Leone, Paolo Ascenzi, Alessandra di Masi
The molecular chaperone heat shock protein 90 (Hsp90α) regulates cells proteostasis and mitigates the harmful effects of endogenous and exogenous stressors on the proteome. Indeed, the inhibition of Hsp90α ATPase activity affects the cellular response to ionizing radiation (IR). Although the interplay between Hsp90α and several DNA damage response (DDR) proteins has been reported, its role in the DDR is still unclear. Here, we show that ATM and NBN, but not 53BP1, RAD50, and MRE11, are Hsp90α clients as the Hsp90α inhibitor 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) induces ATM and NBN polyubiquitination and proteosomal degradation in normal fibroblasts and lymphoblastoid cells lines...
June 20, 2017: FEBS Journal
https://www.readbyqxmd.com/read/28630044/single-molecule-fret-analysis-discloses-the-dynamics-of-the-dna-topoisomerase-ii-top2-interaction-in-the-presence-of-top2-targeting-agents
#7
Wan-Chen Huang, Chun-Ying Lee, Tao-Shih Hsieh
Topoisomerases play crucial roles in DNA replication, transcription, and recombination. For instance, topoisomerase II (Top2) is critically important for resolving DNA tangles during cell division, and as such, it is a broad anticancer drug target. Top2 regulates DNA topology by transiently breaking one double stranded DNA molecule (cleavage), allowing a second double strand to pass through the opened DNA gate (opening), and then closing the gate by rejoining the broken ends. Drugs that modulate Top2 catalysis may therefore affect enzymatic activity at several different steps...
June 19, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28628639/small-molecule-inhibitors-uncover-synthetic-genetic-interactions-of-human-flap-endonuclease-1-fen1-with-dna-damage-response-genes
#8
Thomas A Ward, Peter J McHugh, Stephen T Durant
Flap endonuclease 1 (FEN1) is a structure selective endonuclease required for proficient DNA replication and the repair of DNA damage. Cellularly active inhibitors of this enzyme have previously been shown to induce a DNA damage response and, ultimately, cell death. High-throughput screens of human cancer cell-lines identify colorectal and gastric cell-lines with microsatellite instability (MSI) as enriched for cellular sensitivity to N-hydroxyurea series inhibitors of FEN1, but not the PARP inhibitor olaparib or other inhibitors of the DNA damage response...
2017: PloS One
https://www.readbyqxmd.com/read/28627616/distinct-cellular-phenotype-linked-to-defective-dna-interstrand-crosslink-repair-and-homologous-recombination
#9
Aleksandra M Gorniewska, Katarzyna Kluzek, Lidia Gackowska, Izabela Kubiszewska, Malgorzata Z Zdzienicka, Aneta Bialkowska
Repair of DNA interstrand crosslinks (ICLs) predominantly involves the Fanconi anemia (FA) pathway and homologous recombination (HR). The HR repair system eliminates DNA double strand breaks (DSBs) that emerge during ICLs removal. The current study presents a novel cell line, CL‑V8B, representing a new complementation group of Chinese hamster cell mutants hypersensitive to DNA crosslinking factors. CL‑V8B exhibits increased sensitivity to various DNA‑damaging agents, including compounds leading to DSBs formation (bleomycin and 6‑thioguanine), and is extremely sensitive to poly (ADP-ribose) polymerase inhibitor (>400‑fold), which is typical for HR‑defective cells...
August 2017: Molecular Medicine Reports
https://www.readbyqxmd.com/read/28626219/base-excision-repair-proteins-couple-activation-induced-cytidine-deaminase-and-endonuclease-g-during-replication-stress-induced-mll-destabilization
#10
B Gole, E Mian, M Rall, L Wiesmüller
The breakpoint cluster region of the MLL gene (MLLbcr) is frequently rearranged in therapy-related and infant acute leukaemia, but the destabilizing mechanism is poorly understood. We recently proposed that DNA replication stress results in MLLbcr cleavage via Endonuclease G (EndoG) and represents the common denominator of genotoxic therapy-induced MLL destabilization. Here we performed a siRNA screen for new factors involved in replication stress-induced MLL rearrangements employing an EGFP-based reporter system...
June 19, 2017: Leukemia: Official Journal of the Leukemia Society of America, Leukemia Research Fund, U.K
https://www.readbyqxmd.com/read/28621832/break-induced-replication-links-microsatellite-expansion-to-complex-genome-rearrangements
#11
REVIEW
Michael Leffak
The instability of microsatellite DNA repeats is responsible for at least 40 neurodegenerative diseases. Recently, Mirkin and co-workers presented a novel mechanism for microsatellite expansions based on break-induced replication (BIR) at sites of microsatellite-induced replication stalling and fork collapse. The BIR model aims to explain single-step, large expansions of CAG/CTG trinucleotide repeats in dividing cells. BIR has been characterized extensively in Saccharomyces cerevisiae as a mechanism to repair broken DNA replication forks (single-ended DSBs) and degraded telomeric DNA...
June 16, 2017: BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology
https://www.readbyqxmd.com/read/28607006/nr4a2-promotes-dna-double-strand-break-repair-upon-exposure-to-uvr
#12
Kelvin Yin, Yash Chhabra, Romain Tropée, Yi Chieh Lim, Mitchell Fane, Eloise Dray, Richard Sturm, Aaron G Smith
Exposure of melanocytes to ultraviolet radiation (UVR) induces the formation of UV-lesions that can produce deleterious effects in genomic DNA. Encounters of replication forks with unrepaired UV-lesions can lead to several complex phenomena, such as the formation of DNA double strand breaks (DSBs). The NR4A family of nuclear receptors are transcription factors that have been associated with mediating DNA repair functions downstream of the MC1R signalling pathway in melanocytes. In particular, emerging evidence shows that upon DNA damage, the NR4A2 receptor can translocate to sites of UV-lesion by mechanisms requiring post-translational modifications within the N-terminal domain and at a serine residue in the DNA biding domain at position 337...
June 12, 2017: Molecular Cancer Research: MCR
https://www.readbyqxmd.com/read/28596989/both-rad5-dependent-and-independent-pathways-are-involved-in-dna-damage-associated-sister-chromatid-exchange-in-budding-yeast
#13
Michael T Fasullo, Mingzeng Sun
Sister chromatids are preferred substrates for recombinational repair after cells are exposed to DNA damage. While some agents directly cause double-strand breaks (DSBs), others form DNA base adducts which stall or impede the DNA replication fork. We asked which types of DNA damage can stimulate SCE in budding yeast mutants defective in template switch mechanisms and whether PCNA polyubiquitination functions are required for DNA damage-associated SCE after exposure to potent recombinagens. We measured spontaneous and DNA damage-associated unequal sister chromatid exchange (uSCE) in yeast strains containing two fragments of his3 after exposure to MMS, 4-NQO, UV, X rays, and HO endonuclease-induced DSBs...
2017: AIMS Genetics
https://www.readbyqxmd.com/read/28587792/breaking-fat-how-mycobacteria-and-other-intracellular-pathogens-manipulate-host-lipid-droplets
#14
REVIEW
Caroline Barisch, Thierry Soldati
Tuberculosis (Tb) is a lung infection caused by Mycobacterium tuberculosis (Mtb). With one third of the world population latently infected, it represents the most prevalent bacterial infectious diseases worldwide. Typically, persistence is linked to so-called "dormant" slow-growing bacteria, which have a low metabolic rate and a reduced response to antibiotic treatments. However, dormant bacteria regain growth and virulence when the immune system is weakened, leading again to the active form of the disease...
June 3, 2017: Biochimie
https://www.readbyqxmd.com/read/28580318/targeting-ongoing-dna-damage-in-multiple-myeloma-effects-of-dna-damage-response-inhibitors-on-plasma-cell-survival
#15
Ana Belén Herrero, Norma Carmen Gutiérrez
Human myeloma cell lines (HMCLs) and a subset of myeloma patients with poor prognosis exhibit high levels of replication stress (RS), leading to DNA damage. In this study, we confirmed the presence of DNA double-strand breaks (DSBs) in several HMCLs by measuring γH2AX and RAD51 foci and analyzed the effect of various inhibitors of the DNA damage response on MM cell survival. Inhibition of ataxia telangiectasia and Rad3-related protein (ATR), the main kinase mediating the response to RS, using the specific inhibitor VE-821 induced more cell death in HMCLs than in control lymphoblastoid cells and U266, an HMCL with a low level of DNA damage...
2017: Frontiers in Oncology
https://www.readbyqxmd.com/read/28575236/monitoring-of-the-spatial-and-temporal-dynamics-of-ber-ssbr-pathway-proteins-including-myh-ung2-mpg-nth1-and-neil1-3-during-dna-replication
#16
Karine Ø Bjørås, Mirta M L Sousa, Animesh Sharma, Davi M Fonseca, Caroline K Søgaard, Magnar Bjørås, Marit Otterlei
Base lesions in DNA can stall the replication machinery or induce mutations if bypassed. Consequently, lesions must be repaired before replication or in a post-replicative process to maintain genomic stability. Base excision repair (BER) is the main pathway for repair of base lesions and is known to be associated with DNA replication, but how BER is organized during replication is unclear. Here we coupled the iPOND (isolation of proteins on nascent DNA) technique with targeted mass-spectrometry analysis, which enabled us to detect all proteins required for BER on nascent DNA and to monitor their spatiotemporal orchestration at replication forks...
May 29, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28575031/is-the-efficacy-of-antidepressants-in-panic-disorder-mediated-by-adverse-events-a-mediational-analysis
#17
Irene Bighelli, Anna Borghesani, Corrado Barbui
It has been hypothesised that the perception of adverse events in placebo-controlled antidepressant clinical trials may induce patients to conclude that they have been randomized to the active arm of the trial, leading to the breaking of blind. This may enhance the expectancies for improvement and the therapeutic response. The main objective of this study is to test the hypothesis that the efficacy of antidepressants in panic disorder is mediated by the perception of adverse events. The present analysis is based on a systematic review of published and unpublished randomised trials comparing antidepressants with placebo for panic disorder...
2017: PloS One
https://www.readbyqxmd.com/read/28549155/evidence-for-double-strand-break-mediated-mitochondrial-dna-replication-in-saccharomyces-cerevisiae
#18
Kanchanjunga Prasai, Lucy C Robinson, Rona S Scott, Kelly Tatchell, Lynn Harrison
The mechanism of mitochondrial DNA (mtDNA) replication in Saccharomyces cerevisiae is controversial. Evidence exists for double-strand break (DSB) mediated recombination-dependent replication at mitochondrial replication origin ori5 in hypersuppressive ρ- cells. However, it is not clear if this replication mode operates in ρ+ cells. To understand this, we targeted bacterial Ku (bKu), a DSB binding protein, to the mitochondria of ρ+ cells with the hypothesis that bKu would bind persistently to mtDNA DSBs, thereby preventing mtDNA replication or repair...
May 26, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28540821/enhancing-radiosensitisation-of-brca2-proficient-and-brca2-deficient-cell-lines-with-hyperthermia-and-parp1-i
#19
Arlene L Oei, Vidhula R Ahire, C M van Leeuwen, Rosemarie Ten Cate, Lukas J A Stalpers, Johannes Crezee, H Petra Kok, Nicolaas A P Franken
Poly(ADP-ribose)polymerase1 (PARP1) is an important enzyme in regulating DNA replication. Inhibition of PARP1 can lead to collapsed DNA forks which subsequently causes genomic instability, making DNA more susceptible in developing fatal DNA double strand breaks. PARP1-induced DNA damage is generally repaired by homologous recombination (HR), in which BRCA2 proteins are essential. Therefore, BRCA2-deficient tumour cells are susceptible to treatment with PARP1-inhibitors (PARP1-i). Recently, BRCA2 was shown to be down-regulated by hyperthermia (HT) temporarily, and this consequently inactivated HR for several hours...
May 19, 2017: International Journal of Hyperthermia
https://www.readbyqxmd.com/read/28524082/cellular-repair-of-dna-dna-cross-links-induced-by-1-2-3-4-diepoxybutane
#20
Lisa N Chesner, Amanda Degner, Dewakar Sangaraju, Shira Yomtoubian, Susith Wickramaratne, Bhaskar Malayappan, Natalia Tretyakova, Colin Campbell
Xenobiotic-induced interstrand DNA-DNA cross-links (ICL) interfere with transcription and replication and can be converted to toxic DNA double strand breaks. In this work, we investigated cellular responses to 1,4-bis-(guan-7-yl)-2,3-butanediol (bis-N7G-BD) cross-links induced by 1,2,3,4-diepoxybutane (DEB). High pressure liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI⁺-MS/MS) assays were used to quantify the formation and repair of bis-N7G-BD cross-links in wild-type Chinese hamster lung fibroblasts (V79) and the corresponding isogenic clones V-H1 and V-H4, deficient in the XPD and FANCA genes, respectively...
May 18, 2017: International Journal of Molecular Sciences
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