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Replication fork

Advaitha Madireddy, Settapong T Kosiyatrakul, Rebecca A Boisvert, Emilia Herrera-Moyano, María L García-Rubio, Jeannine Gerhardt, Elizabeth A Vuono, Nichole Owen, Zi Yan, Susan Olson, Andrés Aguilera, Niall G Howlett, Carl L Schildkraut
Common fragile sites (CFSs) are genomic regions that are unstable under conditions of replicative stress. Although the characteristics of CFSs that render them vulnerable to stress are associated mainly with replication, the cellular pathways that protect CFSs during replication remain unclear. Here, we identify and describe a role for FANCD2 as a trans-acting facilitator of CFS replication, in the absence of exogenous replicative stress. In the absence of FANCD2, replication forks stall within the AT-rich fragility core of CFS, leading to dormant origin activation...
October 20, 2016: Molecular Cell
Teodora Nikolova, Anja Göder, Ann Parplys, Kerstin Borgmann
DNA fiber spreading assay is an invaluable technique to visualize and follow the spatial and temporal progress of individual DNA replication forks. It provides information on the DNA replication progress and its regulation under normal conditions as well as on replication stress induced by environmental genotoxic agents or cancer drugs. The method relies on the detection of incorporated thymidine analogues during DNA synthesis in the S phase of the cell cycle by indirect immunofluorescence. Here, we describe the procedure established in our laboratories for sequential pulse labeling of human cells with 5-chloro-2'-deoxyuridine (CldU) and 5-iodo-2'-deoxyuridine (IdU), cell lysis, and DNA fiber spreading on slides and sequential immunodetection of the incorporated thymidine analogues by primary antibodies recognizing specifically CldU or IdU alone...
2017: Methods in Molecular Biology
Vincenzo Sannino, Arun M Kolinjivadi, Giorgio Baldi, Vincenzo Costanzo
The correct duplication of genetic information is essential to maintain genome stability, which is lost in cancer cells. Replication fork integrity is ensured by a number of DNA metabolism proteins that assist replication of chromatin regions difficult to replicate due to their intrinsic DNA sequence composition, coordinate repair of DNA molecules resulting from aberrant replication events or protect replication forks in the presence of lesions impairing their progression. Some DNA metabolism genes involved in DNA repair are essential in higher eukaryotes even in unchallenged conditions, suggesting the existence of biological processes requiring these specialized functions in organisms with complex genomes...
2016: International Journal of Developmental Biology
Jin S Xiong, Steven E McKeand, Fikret Isik, Jill Wegrzyn, David B Neale, Zhao-Bang Zeng, Luciano da Costa E Silva, Ross W Whetten
BACKGROUND: The use of wood as an industrial raw material has led to development of plantation forestry, in which trees are planted, managed, and harvested as crops. The productivity of such plantations often exceeds that of less-intensively-managed forests, and land managers have the option of choosing specific planting stock to produce specific types of wood for industrial use. Stem forking, or division of the stem into two or more stems of roughly equal size, is a character trait important in determining the quality of the stem for production of solid wood products...
October 18, 2016: BMC Genetics
Patricia Perez-Arnaiz, Daniel L Kaplan
Mcm10 is an essential protein that functions to initiate DNA replication after the formation of the replication fork helicase. In this manuscript, we identified a budding yeast Mcm10 mutant (Mcm10-m2,3,4) that is defective in DNA binding in vitro. Moreover, this Mcm10-m2,3,4 mutant does not stimulate the phosphorylation of Mcm2 by DDK in vitro. When we expressed wild-type levels of mcm10-m2,3,4 in budding yeast cells, we observed a severe growth defect and substantially decreased DNA replication. We also observed a substantially reduced RPA-ChIP signal at origins of replication, reduced levels of DDK-phosphorylated-Mcm2 and diminished GINS association with Mcm2-7 in vivo...
October 14, 2016: Journal of Molecular Biology
Panagiotis Kotsantis, Lara Marques Silva, Sarah Irmscher, Rebecca M Jones, Lisa Folkes, Natalia Gromak, Eva Petermann
Cancer is a disease associated with genomic instability that often results from oncogene activation. This in turn leads to hyperproliferation and replication stress. However, the molecular mechanisms that underlie oncogene-induced replication stress are still poorly understood. Oncogenes such as HRAS(V12) promote proliferation by upregulating general transcription factors to stimulate RNA synthesis. Here we investigate whether this increase in transcription underlies oncogene-induced replication stress. We show that in cells overexpressing HRAS(V12), elevated expression of the general transcription factor TATA-box binding protein (TBP) leads to increased RNA synthesis, which together with R-loop accumulation results in replication fork slowing and DNA damage...
October 11, 2016: Nature Communications
Thomas E Bass, Jessica W Luzwick, Gina Kavanaugh, Clinton Carroll, Huzefa Dungrawala, Gloria G Glick, Michael D Feldkamp, Reid Putney, Walter J Chazin, David Cortez
The ATR checkpoint kinase coordinates cellular responses to DNA replication stress. Budding yeast contain three activators of Mec1 (the ATR orthologue); however, only TOPBP1 is known to activate ATR in vertebrates. We identified ETAA1 as a replication stress response protein in two proteomic screens. ETAA1-deficient cells accumulate double-strand breaks, sister chromatid exchanges, and other hallmarks of genome instability. They are also hypersensitive to replication stress and have increased frequencies of replication fork collapse...
October 10, 2016: Nature Cell Biology
Peter Haahr, Saskia Hoffmann, Maxim A X Tollenaere, Teresa Ho, Luis Ignacio Toledo, Matthias Mann, Simon Bekker-Jensen, Markus Räschle, Niels Mailand
Activation of the ATR kinase following perturbations to DNA replication relies on a complex mechanism involving ATR recruitment to RPA-coated single-stranded DNA via its binding partner ATRIP and stimulation of ATR kinase activity by TopBP1. Here, we discovered an independent ATR activation pathway in vertebrates, mediated by the uncharacterized protein ETAA1 (Ewing's tumour-associated antigen 1). Human ETAA1 accumulates at DNA damage sites via dual RPA-binding motifs and promotes replication fork progression and integrity, ATR signalling and cell survival after genotoxic insults...
October 10, 2016: Nature Cell Biology
Nicholas Sen, Joanne Leonard, Raul Torres, Jonay Garcia-Luis, Gloria Palou-Marin, Luis Aragón
Sister chromatid intertwines (SCIs), or catenanes, are topological links between replicated chromatids that interfere with chromosome segregation. The formation of SCIs is thought to be a consequence of fork swiveling during DNA replication, and their removal is thought to occur because of the intrinsic feature of type II topoisomerases (Top2) to simplify DNA topology. Here, we report that SCIs are also formed independently of DNA replication during G2/M by Top2-dependent concatenation of cohesed chromatids due to their physical proximity...
October 6, 2016: Molecular Cell
Andrei Kuzminov
As the ratio of the copy number of the most replicated to the unreplicated regions in the same chromosome, the definition of chromosomal replication complexity (CRC) appears to leave little room for variation, being either two during S-phase or one otherwise. However, bacteria dividing faster than they replicate their chromosome spike CRC to four and even eight. A recent experimental inquiry about the limits of CRC in Escherichia coli revealed two major reasons to avoid elevating it further: (i) increased chromosomal fragmentation and (ii) complications with subsequent double-strand break repair...
October 2016: PLoS Genetics
Arun Kanakkanthara, Karthik B Jeganathan, Jazeel F Limzerwala, Darren J Baker, Masakazu Hamada, Hyun-Ja Nam, Willemijn H van Deursen, Naomi Hamada, Ryan M Naylor, Nicole A Becker, Brian A Davies, Janine H van Ree, Georges Mer, Virginia S Shapiro, L James Maher, David J Katzmann, Jan M van Deursen
Cyclin A2 activates the cyclin-dependent kinases Cdk1 and Cdk2 and is expressed at elevated levels from S phase until early mitosis. We found that mutant mice that cannot elevate cyclin A2 are chromosomally unstable and tumor-prone. Underlying the chromosomal instability is a failure to up-regulate the meiotic recombination 11 (Mre11) nuclease in S phase, which leads to impaired resolution of stalled replication forks, insufficient repair of double-stranded DNA breaks, and improper segregation of sister chromosomes...
September 30, 2016: Science
James P R Connolly, Andrew J Roe
: We recently discovered that exposure of enterohaemorrhagic Escherichia coli (EHEC) to D-serine resulted in accumulation of this unusual amino acid, induction of the SOS regulon and downregulation of type III secretion that is essential for efficient colonization of the host. Here, we have investigated the physiological relevance of this elevated SOS response, which is of particular interest given the presence of Stx-toxin carrying lysogenic prophages on the EHEC chromosome that are activated during the SOS response...
October 3, 2016: Journal of Bacteriology
Wonbae Lee, John P Gillies, Davis Jose, Brett A Israels, Peter H von Hippel, Andrew H Marcus
Gene 32 protein (gp32) is the single-stranded (ss) DNA binding protein of the bacteriophage T4. It binds transiently and cooperatively to ssDNA sequences exposed during the DNA replication process and regulates the interactions of the other sub-assemblies of the replication complex during the replication cycle. We here use single-molecule FRET techniques to build on previous thermodynamic studies of gp32 binding to initiate studies of the dynamics of the isolated and cooperative binding of gp32 molecules within the replication complex...
September 30, 2016: Nucleic Acids Research
Koichi Sato, Mayo Shimomuki, Yoko Katsuki, Daisuke Takahashi, Wataru Kobayashi, Masamichi Ishiai, Hiroyuki Miyoshi, Minoru Takata, Hitoshi Kurumizaka
The FANCI-FANCD2 (I-D) complex is considered to work with RAD51 to protect the damaged DNA in the stalled replication fork. However, the means by which this DNA protection is accomplished have remained elusive. In the present study, we found that the I-D complex directly binds to RAD51, and stabilizes the RAD51-DNA filament. Unexpectedly, the DNA binding activity of FANCI, but not FANCD2, is explicitly required for the I-D complex-mediated RAD51-DNA filament stabilization. The RAD51 filament stabilized by the I-D complex actually protects the DNA end from nucleolytic degradation by an FA-associated nuclease, FAN1...
September 30, 2016: Nucleic Acids Research
Daniel R Semlow, Jieqiong Zhang, Magda Budzowska, Alexander C Drohat, Johannes C Walter
During eukaryotic DNA interstrand cross-link (ICL) repair, cross-links are resolved ("unhooked") by nucleolytic incisions surrounding the lesion. In vertebrates, ICL repair is triggered when replication forks collide with the lesion, leading to FANCI-FANCD2-dependent unhooking and formation of a double-strand break (DSB) intermediate. Using Xenopus egg extracts, we describe here a replication-coupled ICL repair pathway that does not require incisions or FANCI-FANCD2. Instead, the ICL is unhooked when one of the two N-glycosyl bonds forming the cross-link is cleaved by the DNA glycosylase NEIL3...
October 6, 2016: Cell
Chiaki Noguchi, Grant Grothusen, Vinesh Anandarajan, Marta Martínez-Lage García, Daniel Terlecky, Krysten Corzo, Katsunori Tanaka, Hiroshi Nakagawa, Eishi Noguchi
Acetaldehyde, a primary metabolite of alcohol, forms DNA adducts and disrupts the DNA replication process, causing genomic instability, a hallmark of cancer. Indeed, chronic alcohol consumption accounts for approximately 3.6% of all cancers worldwide. However, how the adducts are prevented and repaired after acetaldehyde exposure is not well understood. In this report, we used the fission yeast Schizosaccharomyces pombe as a model organism to comprehensively understand the genetic controls of DNA damage avoidance in response to acetaldehyde...
September 29, 2016: Cell Cycle
Austin T Raper, Zucai Suo
DNA polymerases catalyze DNA synthesis through a stepwise kinetic mechanism that begins with binding to DNA, followed by selection, binding, and incorporation of a nucleotide into an elongating primer. It is hypothesized that subtle active site adjustments in a polymerase to align reactive moieties limit the rate of correct nucleotide incorporation. DNA damage can impede this process for many DNA polymerases, causing replication fork stalling, genetic mutations, and potentially cell death. However, specialized Y-family DNA polymerases are structurally evolved to efficiently bypass DNA damage in vivo, albeit at the expense of replication fidelity...
October 10, 2016: Biochemistry
Norbert Schormann, Natalia Zhukovskaya, Gregory Bedwell, Manunya Nuth, Richard Gillilan, Peter E Prevelige, Robert P Ricciardi, Surajit Banerjee, Debasish Chattopadhyay
Uracil-DNA glycosylases are ubiquitous enzymes, which play a key role repairing damages in DNA and in maintaining genomic integrity by catalyzing the first step in the base excision repair pathway. Within the superfamily of uracil-DNA glycosylases family I enzymes or UNGs are specific for recognizing and removing uracil from DNA. These enzymes feature conserved structural folds, active site residues and use common motifs for DNA binding, uracil recognition and catalysis. Within this family the enzymes of poxviruses are unique and most remarkable in terms of amino acid sequences, characteristic motifs and more importantly for their novel non-enzymatic function in DNA replication...
September 29, 2016: Protein Science: a Publication of the Protein Society
Arnab Ray Chaudhuri, Elsa Callen, Xia Ding, Ewa Gogola, Alexandra A Duarte, Ji-Eun Lee, Nancy Wong, Vanessa Lafarga, Jennifer A Calvo, Nicholas J Panzarino, Sam John, Amanda Day, Anna Vidal Crespo, Binghui Shen, Linda M Starnes, Julian R de Ruiter, Jeremy A Daniel, Panagiotis A Konstantinopoulos, David Cortez, Sharon B Cantor, Oscar Fernandez-Capetillo, Kai Ge, Jos Jonkers, Sven Rottenberg, Shyam K Sharan, André Nussenzweig
No abstract text is available yet for this article.
September 28, 2016: Nature
Andrew M Cobb, Thomas V Murray, Derek T Warren, Yiwen Liu, Catherine M Shanahan
The accumulation of prelamin A is linked to disruption of cellular homeostasis, tissue degeneration and ageing. Its expression is implicated in compromised genome stability and increased levels of DNA damage, but to date there is no complete explanation for how prelamin A exerts its toxic effects. As the nuclear lamina is important for DNA replication we wanted to investigate the relationship between prelamin A expression and DNA replication fork stability. In this study we report that the expression of prelamin A in U2OS cells induced both mono-ubiquitination of proliferating cell nuclear antigen (PCNA) and subsequent induction of Pol η, two hallmarks of DNA replication fork stalling...
September 27, 2016: Nucleus
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