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https://www.readbyqxmd.com/read/28811666/the-essential-kinase-atr-ensuring-faithful-duplication-of-a-challenging-genome
#1
REVIEW
Joshua C Saldivar, David Cortez, Karlene A Cimprich
One way to preserve a rare book is to lock it away from all potential sources of damage. Of course, an inaccessible book is also of little use, and the paper and ink will continue to degrade with age in any case. Like a book, the information stored in our DNA needs to be read, but it is also subject to continuous assault and therefore needs to be protected. In this Review, we examine how the replication stress response that is controlled by the kinase ataxia telangiectasia and Rad3-related (ATR) senses and resolves threats to DNA integrity so that the DNA remains available to read in all of our cells...
August 16, 2017: Nature Reviews. Molecular Cell Biology
https://www.readbyqxmd.com/read/28806726/replication-fork-slowing-and-stalling-are-distinct-checkpoint-independent-consequences-of-replicating-damaged-dna
#2
Divya Ramalingam Iyer, Nicholas Rhind
In response to DNA damage during S phase, cells slow DNA replication. This slowing is orchestrated by the intra-S checkpoint and involves inhibition of origin firing and reduction of replication fork speed. Slowing of replication allows for tolerance of DNA damage and suppresses genomic instability. Although the mechanisms of origin inhibition by the intra-S checkpoint are understood, major questions remain about how the checkpoint regulates replication forks: Does the checkpoint regulate the rate of fork progression? Does the checkpoint affect all forks, or only those encountering damage? Does the checkpoint facilitate the replication of polymerase-blocking lesions? To address these questions, we have analyzed the checkpoint in the fission yeast Schizosaccharomyces pombe using a single-molecule DNA combing assay, which allows us to unambiguously separate the contribution of origin and fork regulation towards replication slowing, and allows us to investigate the behavior of individual forks...
August 14, 2017: PLoS Genetics
https://www.readbyqxmd.com/read/28802045/transcription-replication-conflict-orientation-modulates-r-loop-levels-and-activates-distinct-dna-damage-responses
#3
Stephan Hamperl, Michael J Bocek, Joshua C Saldivar, Tomek Swigut, Karlene A Cimprich
Conflicts between transcription and replication are a potent source of DNA damage. Co-transcriptional R-loops could aggravate such conflicts by creating an additional barrier to replication fork progression. Here, we use a defined episomal system to investigate how conflict orientation and R-loop formation influence genome stability in human cells. R-loops, but not normal transcription complexes, induce DNA breaks and orientation-specific DNA damage responses during conflicts with replication forks. Unexpectedly, the replisome acts as an orientation-dependent regulator of R-loop levels, reducing R-loops in the co-directional (CD) orientation but promoting their formation in the head-on (HO) orientation...
August 10, 2017: Cell
https://www.readbyqxmd.com/read/28802036/transcription-replication-conflicts-orientation-matters
#4
Yea-Lih Lin, Philippe Pasero
Interference between DNA replication and transcription represents a major source of genomic instability. In this issue of Cell, Lang et al. and Hamperl et al. show that head-on collisions, but not codirectional collisions, impede fork progression in bacteria and in human cells by promoting the formation of RNA-DNA hybrids known as R-loops.
August 10, 2017: Cell
https://www.readbyqxmd.com/read/28801308/egfr-mutations-compromise-hypoxia-associated-radiation-resistance-through-impaired-replication-fork-associated-dna-damage-repair
#5
Mohammad Saki, Haruhiko Makino, Prashanthi Javvadi, Nozomi Tomimatsu, Lianghao Ding, Jennifer E Clark, Elaine Gavin, Kenichi Takeda, Joel Andrews, Debabrata Saha, Michael D Story, Sandeep Burma, Chaitanya Nirodi
Epidermal growth factor receptor (EGFR) signaling has been implicated in hypoxia-associated resistance to radiation or chemotherapy. Non-small cell lung carcinomas (NSCLC) with activating L858R or ΔE746-E750 EGFR mutations exhibit elevated EGFR activity and downstream signaling. Here, relative to wild type (WT) EGFR, mutant (MT) EGFR expression significantly increases radiosensitivity in hypoxic cells. Gene expression profiling in human bronchial epithelial cells (HBEC) revealed that MT-EGFR expression elevated transcripts related to cell cycle and replication in aerobic and hypoxic conditions and down-regulated RAD50, a critical component of non-homologous end-joining (NHEJ) and homologous recombination (HR) DNA repair pathways...
August 11, 2017: Molecular Cancer Research: MCR
https://www.readbyqxmd.com/read/28779875/paths-from-dna-damage-and-signaling-to-genome-rearrangements-via-homologous-recombination
#6
REVIEW
Jac A Nickoloff
DNA damage is a constant threat to genome integrity. DNA repair and damage signaling networks play a central role maintaining genome stability, suppressing tumorigenesis, and determining tumor response to common cancer chemotherapeutic agents and radiotherapy. DNA double-strand breaks (DSBs) are critical lesions induced by ionizing radiation and when replication forks encounter damage. DSBs can result in mutations and large-scale genome rearrangements reflecting mis-repair by non-homologous end joining or homologous recombination...
July 24, 2017: Mutation Research
https://www.readbyqxmd.com/read/28761001/dna-damage-tolerance-in-hematopoietic-stem-and-progenitor-cells-in-mice
#7
Bas Pilzecker, Olimpia Alessandra Buoninfante, Paul van den Berk, Cesare Lancini, Ji-Ying Song, Elisabetta Citterio, Heinz Jacobs
DNA damage tolerance (DDT) enables bypassing of DNA lesions during replication, thereby preventing fork stalling, replication stress, and secondary DNA damage related to fork stalling. Three modes of DDT have been documented: translesion synthesis (TLS), template switching (TS), and repriming. TLS and TS depend on site-specific PCNA K164 monoubiquitination and polyubiquitination, respectively. To investigate the role of DDT in maintaining hematopoietic stem cells (HSCs) and progenitors, we used Pcna(K164R/K164R) mice as a unique DDT-defective mouse model...
August 15, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28757209/smarcal1-mediated-fork-reversal-triggers-mre11-dependent-degradation-of-nascent-dna-in-the-absence-of-brca2-and-stable-rad51-nucleofilaments
#8
Arun Mouli Kolinjivadi, Vincenzo Sannino, Anna De Antoni, Karina Zadorozhny, Mairi Kilkenny, Hervé Técher, Giorgio Baldi, Rong Shen, Alberto Ciccia, Luca Pellegrini, Lumir Krejci, Vincenzo Costanzo
Brca2 deficiency causes Mre11-dependent degradation of nascent DNA at stalled forks, leading to cell lethality. To understand the molecular mechanisms underlying this process, we isolated Xenopus laevis Brca2. We demonstrated that Brca2 protein prevents single-stranded DNA gap accumulation at replication fork junctions and behind them by promoting Rad51 binding to replicating DNA. Without Brca2, forks with persistent gaps are converted by Smarcal1 into reversed forks, triggering extensive Mre11-dependent nascent DNA degradation...
July 20, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28756516/synthetic-lethality-in-malignant-pleural-mesothelioma-with-parp1-inhibition
#9
Gayathri Srinivasan, Gurjit Singh Sidhu, Elizabeth A Williamson, Aruna S Jaiswal, Nasreen Najmunnisa, Keith Wilcoxen, Dennie Jones, Thomas J George, Robert Hromas
Malignant pleural mesotheliomas (MPM) are most often surgically unresectable, and they respond poorly to current chemotherapy and radiation therapy. Between 23 and 64% of malignant pleural mesothelioma have somatic inactivating mutations in the BAP1 gene. BAP1 is a homologous recombination (HR) DNA repair component found in the BRCA1/BARD1 complex. Similar to BRCA1/2 deficient cancers, mutation in the BAP1 gene leads to a deficient HR pathway and increases the reliance on other DNA repair pathways. We hypothesized that BAP1-mutant MPM would require PARP1 for survival, similar to the BRCA1/2 mutant breast and ovarian cancers...
July 29, 2017: Cancer Chemotherapy and Pharmacology
https://www.readbyqxmd.com/read/28749464/the-cohesin-complex-prevents-myc-induced-replication-stress
#10
Sara Rohban, Aurora Cerutti, Marco J Morelli, Fabrizio d'Adda di Fagagna, Stefano Campaner
The cohesin complex is mutated in cancer and in a number of rare syndromes collectively known as Cohesinopathies. In the latter case, cohesin deficiencies have been linked to transcriptional alterations affecting Myc and its target genes. Here, we set out to understand to what extent the role of cohesins in controlling cell cycle is dependent on Myc expression and activity. Inactivation of the cohesin complex by silencing the RAD21 subunit led to cell cycle arrest due to both transcriptional impairment of Myc target genes and alterations of replication forks, which were fewer and preferentially unidirectional...
July 27, 2017: Cell Death & Disease
https://www.readbyqxmd.com/read/28749073/arranging-eukaryotic-nuclear-dna-polymerases-for-replication-specific-interactions-with-accessory-proteins-arrange-pols-%C3%AE-%C3%AE-and-%C3%AF%C2%B5-in-the-replisome-for-leading-strand-and-lagging-strand-dna-replication
#11
REVIEW
Thomas A Kunkel, Peter M J Burgers
Biochemical and cryo-electron microscopy studies have just been published revealing interactions among proteins of the yeast replisome that are important for highly coordinated synthesis of the two DNA strands of the nuclear genome. These studies reveal key interactions important for arranging DNA polymerases α, δ, and ϵ for leading and lagging strand replication. The CMG (Mcm2-7, Cdc45, GINS) helicase is central to this interaction network. These are but the latest examples of elegant studies performed in the recent past that lead to a much better understanding of how the eukaryotic replication fork achieves efficient DNA replication that is accurate enough to prevent diseases yet allows evolution...
August 2017: BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology
https://www.readbyqxmd.com/read/28746850/investigation-of-n-terminal-phospho-regulation-of%C3%A2-uracil-dna-glycosylase-using-protein-semisynthesis
#12
Brian P Weiser, James T Stivers, Philip A Cole
Uracil DNA Glycosylase (UNG2) is the primary enzyme in humans that prevents the stable incorporation of deoxyuridine monophosphate into DNA in the form of U/A basepairs. During S-phase, UNG2 remains associated with the replication fork through its interactions with two proteins, Proliferating Cell Nuclear Antigen (PCNA) and Replication Protein A (RPA), which are critical for DNA replication and repair. In this work, we used protein semisynthesis and fluorescence anisotropy assays to explore the interactions of UNG2 with PCNA and RPA and to determine the effects of two UNG2 phosphorylation sites (Thr(6) and Tyr(8)) located within its PCNA-interacting motif (PIP-box)...
July 25, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28743747/the-ul8-subunit-of-the-helicase-primase-complex-of-herpes-simplex-virus-promotes-dna-annealing-and-has-a-high-affinity-for-replication-forks
#13
Oya Bermek, Sandra K Weller, Jack D Griffith
During lytic infection, herpes simplex virus (HSV) DNA is replicated by a mechanism involving DNA recombination. For instance, replication of the HSV-1 genome produces X- and Y-branched structures, reminiscent of recombination intermediates. HSV-1's replication machinery includes a trimeric helicase/primase is composed of helicase (UL5) and primase (UL52) subunits and a third subunit, UL8. UL8 has been reported to stimulate the helicase and primase activities of the complex in the presence of ICP8, an HSV-1 protein that functions as an annealase, a protein that binds complementary single-stranded (ss)DNA and facilitates its annealing to duplex DNA...
July 25, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28735897/radx-promotes-genome-stability-and-modulates-chemosensitivity-by-regulating-rad51-at-replication-forks
#14
Huzefa Dungrawala, Kamakoti P Bhat, Rémy Le Meur, Walter J Chazin, Xia Ding, Shyam K Sharan, Sarah R Wessel, Aditya A Sathe, Runxiang Zhao, David Cortez
RAD51 promotes homology-directed repair (HDR), replication fork reversal, and stalled fork protection. Defects in these functions cause genomic instability and tumorigenesis but also generate hypersensitivity to cancer therapeutics. Here we describe the identification of RADX as an RPA-like, single-strand DNA binding protein. RADX is recruited to replication forks, where it prevents fork collapse by regulating RAD51. When RADX is inactivated, excessive RAD51 activity slows replication elongation and causes double-strand breaks...
August 3, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28732309/zebularine-induces-replication-dependent-double-strand-breaks-which-are-preferentially-repaired-by-homologous-recombination
#15
Manuel Luis Orta, Nuria Pastor, Estefanía Burgos-Morón, Inmaculada Domínguez, José Manuel Calderón-Montaño, Carlos Huertas Castaño, Miguel López-Lázaro, Thomas Helleday, Santiago Mateos
Zebularine is a second-generation, highly stable hydrophilic inhibitor of DNA methylation with oral bioavailability that preferentially target cancer cells. It acts primarily as a trap for DNA methyl transferases (DNMTs) protein by forming covalent complexes between DNMT protein and zebularine-substrate DNA. It's well documented that replication-blocking DNA lesions can cause replication fork collapse and thereby to the formation of DNA double-strand breaks (DSB). DSB are dangerous lesions that can lead to potentially oncogenic genomic rearrangements or cell death...
July 12, 2017: DNA Repair
https://www.readbyqxmd.com/read/28729482/brca1-and-brca2-tumor-suppressors-protect-against-endogenous-acetaldehyde-toxicity
#16
Eliana Mc Tacconi, Xianning Lai, Cecilia Folio, Manuela Porru, Gijs Zonderland, Sophie Badie, Johanna Michl, Irene Sechi, Mélanie Rogier, Verónica Matía García, Ankita Sati Batra, Oscar M Rueda, Peter Bouwman, Jos Jonkers, Anderson Ryan, Bernardo Reina-San-Martin, Joannie Hui, Nelson Tang, Alejandra Bruna, Annamaria Biroccio, Madalena Tarsounas
Maintenance of genome integrity requires the functional interplay between Fanconi anemia (FA) and homologous recombination (HR) repair pathways. Endogenous acetaldehyde, a product of cellular metabolism, is a potent source of DNA damage, particularly toxic to cells and mice lacking the FA protein FANCD2. Here, we investigate whether HR-compromised cells are sensitive to acetaldehyde, similarly to FANCD2-deficient cells. We demonstrate that inactivation of HR factors BRCA1, BRCA2, or RAD51 hypersensitizes cells to acetaldehyde treatment, in spite of the FA pathway being functional...
July 20, 2017: EMBO Molecular Medicine
https://www.readbyqxmd.com/read/28718810/dna2-an-important-player-in-dna-damage-response-or-just-another-dna-maintenance-protein
#17
REVIEW
Elzbieta Pawłowska, Joanna Szczepanska, Janusz Blasiak
The human DNA2 (DNA replication helicase/nuclease 2) protein is expressed in both the nucleus and mitochondria, where it displays ATPase-dependent nuclease and helicase activities. DNA2 plays an important role in the removing of long flaps in DNA replication and long-patch base excision repair (LP-BER), interacting with the replication protein A (RPA) and the flap endonuclease 1 (FEN1). DNA2 can promote the restart of arrested replication fork along with Werner syndrome ATP-dependent helicase (WRN) and Bloom syndrome protein (BLM)...
July 18, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/28718400/histone-h3g34r-mutation-causes-replication-stress-homologous-recombination-defects-and-genomic-instability-in-s-pombe
#18
Rajesh K Yadav, Carolyn M Jablonowski, Alfonso G Fernandez, Brandon R Lowe, Ryan A Henry, David Finkelstein, Kevin J Barnum, Alison L Pidoux, Yin-Ming Kuo, Jie Huang, Matthew J O'Connell, Andrew J Andrews, Arzu Onar-Thomas, Robin C Allshire, Janet F Partridge
Recurrent somatic mutations of H3F3A in aggressive pediatric high-grade gliomas generate K27M or G34R/V mutant histone H3.3. H3.3-G34R/V mutants are common in tumors with mutations in p53 and ATRX, an H3.3-specific chromatin remodeler. To gain insight into the role of H3-G34R, we generated fission yeast that express only the mutant histone H3. H3-G34R specifically reduces H3K36 tri-methylation and H3K36 acetylation, and mutants show partial transcriptional overlap with set2 deletions. H3-G34R mutants exhibit genomic instability and increased replication stress, including slowed replication fork restart, although DNA replication checkpoints are functional...
July 18, 2017: ELife
https://www.readbyqxmd.com/read/28717046/from-structure-to-mechanism-understanding-initiation-of-dna-replication
#19
REVIEW
Alberto Riera, Marta Barbon, Yasunori Noguchi, L Maximilian Reuter, Sarah Schneider, Christian Speck
DNA replication results in the doubling of the genome prior to cell division. This process requires the assembly of 50 or more protein factors into a replication fork. Here, we review recent structural and biochemical insights that start to explain how specific proteins recognize DNA replication origins, load the replicative helicase on DNA, unwind DNA, synthesize new DNA strands, and reassemble chromatin. We focus on the minichromosome maintenance (MCM2-7) proteins, which form the core of the eukaryotic replication fork, as this complex undergoes major structural rearrangements in order to engage with DNA, regulate its DNA-unwinding activity, and maintain genome stability...
June 1, 2017: Genes & Development
https://www.readbyqxmd.com/read/28717002/human-ribonuclease-h1-resolves-r-loops-and-thereby-enables-progression-of-the-dna-replication-fork
#20
Shankar Parajuli, Daniel C Tealsey, Bhavna Murali, Jessica Jackson, Alessandro Vindigni, Sheila A Stewart
Faithful DNA replication is essential for genome stability. To ensure accurate replication, numerous complex and redundant replication and repair mechanisms function in tandem with the core replication proteins to ensure DNA replication continues even when replication challenges are present that could impede progression of the replication fork. A unique topological challenge to the replication machinery is posed by RNA:DNA hybrids, commonly referred to as R-loops. While R-loops play important roles in gene expression and recombination at immunoglobulin sites, their persistence is thought to interfere with DNA replication by slowing or impeding replication fork progression...
July 17, 2017: Journal of Biological Chemistry
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