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Holliday junction

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https://www.readbyqxmd.com/read/28090586/holliday-junction-trap-shows-how-cells-use-recombination-and-a-junction-guardian-role-of-recq-helicase
#1
Jun Xia, Li-Tzu Chen, Qian Mei, Chien-Hui Ma, Jennifer A Halliday, Hsin-Yu Lin, David Magnan, John P Pribis, Devon M Fitzgerald, Holly M Hamilton, Megan Richters, Ralf B Nehring, Xi Shen, Lei Li, David Bates, P J Hastings, Christophe Herman, Makkuni Jayaram, Susan M Rosenberg
DNA repair by homologous recombination (HR) underpins cell survival and fuels genome instability, cancer, and evolution. However, the main kinds and sources of DNA damage repaired by HR in somatic cells and the roles of important HR proteins remain elusive. We present engineered proteins that trap, map, and quantify Holliday junctions (HJs), a central DNA intermediate in HR, based on catalytically deficient mutant RuvC protein of Escherichia coli. We use RuvCDefGFP (RDG) to map genomic footprints of HR at defined DNA breaks in E...
November 2016: Science Advances
https://www.readbyqxmd.com/read/28051169/intercalative-dna-binding-of-the-marine-anticancer-drug-variolin-b
#2
Albert Canals, Raquel Arribas-Bosacoma, Fernando Albericio, Mercedes Álvarez, Joan Aymamí, Miquel Coll
Variolin B is a rare marine alkaloid that showed promising anti-cancer activity soon after its isolation. It acts as a cyclin-dependent kinase inhibitor, although the precise mechanism through which it exerts the cytotoxic effects is still unknown. The crystal structure of a variolin B bound to a DNA forming a pseudo-Holliday junction shows that this compound can also contribute, through intercalative binding, to either the formation or stabilization of multi-stranded DNA forms.
January 4, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28049850/resolution-of-single-and-double-holliday-junction-recombination-intermediates-by-gen1
#3
Rajvee Shah Punatar, Maria Jose Martin, Haley D M Wyatt, Ying Wai Chan, Stephen C West
Genetic recombination provides an important mechanism for the repair of DNA double-strand breaks. Homologous pairing and strand exchange lead to the formation of DNA intermediates, in which sister chromatids or homologous chromosomes are covalently linked by four-way Holliday junctions (HJs). Depending on the type of recombination reaction that takes place, intermediates may have single or double HJs, and their resolution is essential for proper chromosome segregation. In mitotic cells, double HJs are primarily dissolved by the BLM helicase-TopoisomeraseIIIα-RMI1-RMI2 (BTR) complex, whereas single HJs (and double HJs that have escaped the attention of BTR) are resolved by structure-selective endonucleases known as HJ resolvases...
January 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28049740/resolvase-osgen1-mediates-dna-repair-by-homologous-recombination
#4
Chong Wang, James Higgins, Yi He, Pingli Lu, Dabing Zhang, Wanqi Liang
Yen1/GEN1 are canonical Holliday Junction (HJ) resolvases that belong to the RAD2/XPG family. In eukaryotes, such as budding yeast, mice, worms, and humans, Yen1/GEN1 work together with Mus81-Mms4/MUS81-EME1 and Slx1-Slx4/SLX1-SLX4 in DNA repair by homologous recombination to maintain genome stability. In plants, the biological function of Yen1/GEN1 remains largely unclear. In this study, we characterized the loss of function mutants of OsGEN1 and OsSEND1, a pair of paralogs of Yen1/GEN1 in rice. We first investigated the role of OsGEN1 during meiosis and found a reduction in chiasma frequency by ~6% in osgen1 mutants, compared to wild type, suggesting a possible involvement of OsGEN1 in the formation of crossovers...
January 3, 2017: Plant Physiology
https://www.readbyqxmd.com/read/27990631/holliday-junction-resolving-enzymes-structures-and-mechanisms
#5
REVIEW
David M J Lilley
Holliday junction-resolving enzymes are nucleases that are highly specific for the structure of the junction, to which they bind in dimeric form. Two symmetrically disposed cleavages are made. These are not simultaneous, but the second cleavage is accelerated relative to the first, so ensuring that bilateral cleavage occurs during the lifetime of the DNA-protein complex. In eukaryotic cells there are two known junction-resolving activities. GEN1 is similar to enzymes from lower organisms. A crystallographic structure of a fungal GEN1 bound to the product of resolution has been determined...
December 19, 2016: FEBS Letters
https://www.readbyqxmd.com/read/27977684/loss-of-rmi2-increases-genome-instability-and-causes-a-bloom-like-syndrome
#6
Damien F Hudson, David J Amor, Amber Boys, Kathy Butler, Lorna Williams, Tao Zhang, Paul Kalitsis
Bloom syndrome is a recessive human genetic disorder with features of genome instability, growth deficiency and predisposition to cancer. The only known causative gene is the BLM helicase that is a member of a protein complex along with topoisomerase III alpha, RMI1 and 2, which maintains replication fork stability and dissolves double Holliday junctions to prevent genome instability. Here we report the identification of a second gene, RMI2, that is deleted in affected siblings with Bloom-like features. Cells from homozygous individuals exhibit elevated rates of sister chromatid exchange, anaphase DNA bridges and micronuclei...
December 2016: PLoS Genetics
https://www.readbyqxmd.com/read/27977207/photon-by-photon-hidden-markov-model-analysis-for-microsecond-single-molecule-fret-kinetics
#7
Menahem Pirchi, Roman Tsukanov, Rashid Khamis, Toma E Tomov, Yaron Berger, Dinesh C Khara, Hadas Volkov, Gilad Haran, Eyal Nir
The function of biological macromolecules involves large-scale conformational dynamics spanning multiple time scales, from microseconds to seconds. Such conformational motions, which may involve whole domains or subunits of a protein, play a key role in allosteric regulation. There is an urgent need for experimental methods to probe the fastest of these motions. Single-molecule fluorescence experiments can in principle be used for observing such dynamics, but there is a lack of analysis methods that can extract the maximum amount of information from the data, down to the microsecond time scale...
December 29, 2016: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/27923713/when-transcription-goes-on-holliday-double-holliday-junctions-block-rna-polymerase-ii-transcription-in-vitro
#8
Anne Pipathsouk, Boris P Belotserkovskii, Philip C Hanawalt
Non-canonical DNA structures can obstruct transcription. This transcription blockage could have various biological consequences, including genomic instability and gratuitous transcription-coupled repair. Among potential structures causing transcription blockage are Holliday junctions (HJs), which can be generated as intermediates in homologous recombination or during processing of stalled replication forks. Of particular interest is the double Holliday junction (DHJ), which contains two HJs. Topological considerations impose the constraint that the total number of helical turns in the DNA duplexes between the junctions cannot be altered as long as the flanking DNA duplexes are intact...
December 5, 2016: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/27908236/interaction-between-saccharomyces-cerevisiae-mitochondrial-dna-binding-protein-abf2p-and-cce1p-resolvase
#9
E O Samoilova, I A Krasheninnikov, S A Levitskii
Mitochondrial DNA is susceptible to the action of reactive oxygen species generated by the reactions of oxidative phosphorylation. Homologous recombination is one of the mechanisms providing integrity of the mitochondrial genome. Some proteins that take part in this process in budding yeast mitochondria have been identified. These include Abf2p, the major protein of the mt-nucleoid that specifically binds cruciform DNA, and Cce1p - Holliday junction resolvase. Here we show that Abf2p does not significantly affect either binding of Cce1p to branched DNA or rate and specificity of Holliday junction resolution...
October 2016: Biochemistry. Biokhimii︠a︡
https://www.readbyqxmd.com/read/27903910/structural-insights-into-dynamics-of-recu-hj-complex-formation-elucidates-key-role-of-ntr-and-stalk-region-toward-formation-of-reactive-state
#10
Sagar Khavnekar, Sarath Chandra Dantu, Svetlana Sedelnikova, Sylvia Ayora, John Rafferty, Avinash Kale
Holliday junction (HJ) resolving enzyme RecU is involved in DNA repair and recombination. We have determined the crystal structure of inactive mutant (D88N) of RecU from Bacillus subtilis in complex with a 12 base palindromic DNA fragment at a resolution of 3.2 Å. This structure shows the stalk region and the essential N-terminal region (NTR) previously unseen in our DNA unbound structure. The flexible nature of the NTR in solution was confirmed using SAXS. Thermofluor studies performed to assess the stability of RecU in complex with the arms of an HJ indicate that it confers stability...
November 29, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27846560/molecular-force-spectroscopy-with-a-dna-origami-based-nanoscopic-force-clamp
#11
Philipp C Nickels, Bettina Wünsch, Phil Holzmeister, Wooli Bae, Luisa M Kneer, Dina Grohmann, Philip Tinnefeld, Tim Liedl
Forces in biological systems are typically investigated at the single-molecule level with atomic force microscopy or optical and magnetic tweezers, but these techniques suffer from limited data throughput and their requirement for a physical connection to the macroscopic world. We introduce a self-assembled nanoscopic force clamp built from DNA that operates autonomously and allows massive parallelization. Single-stranded DNA sections of an origami structure acted as entropic springs and exerted controlled tension in the low piconewton range on a molecular system, whose conformational transitions were monitored by single-molecule Förster resonance energy transfer...
October 21, 2016: Science
https://www.readbyqxmd.com/read/27806301/meiotic-nuclear-oscillations-are-necessary-to-avoid-excessive-chromosome-associations
#12
Mariola R Chacón, Petrina Delivani, Iva M Tolić
Pairing of homologous chromosomes is a crucial step in meiosis, which in fission yeast depends on nuclear oscillations. However, how nuclear oscillations help pairing is unknown. Here, we show that homologous loci typically pair when the spindle pole body is at the cell pole and the nucleus is elongated, whereas they unpair when the spindle pole body is in the cell center and the nucleus is round. Inhibition of oscillations demonstrated that movement is required for initial pairing and that prolonged association of loci leads to mis-segregation...
November 1, 2016: Cell Reports
https://www.readbyqxmd.com/read/27799325/muts2-promotes-homologous-recombination-in-bacillus-subtilis
#13
Peter E Burby, Lyle A Simmons
: Bacterial MutS proteins are subdivided into two families, MutS1 and MutS2. MutS1 family members recognize DNA replication errors during their participation in the well-characterized mismatch repair (MMR) pathway. In contrast to the well-described function of MutS1, the function of MutS2 in bacteria has remained less clear. In Helicobacter pylori and Thermus thermophilus, MutS2 has been shown to suppress homologous recombination. The role of MutS2 is unknown in the Gram-positive bacterium Bacillus subtilis In this work, we investigated the contribution of MutS2 to maintaining genome integrity in B...
January 15, 2017: Journal of Bacteriology
https://www.readbyqxmd.com/read/27779184/replication-intermediates-that-escape-dna2-activity-are-processed-by-holliday-junction-resolvase-yen1
#14
Gizem Ölmezer, Maryna Levikova, Dominique Klein, Benoît Falquet, Gabriele Alessandro Fontana, Petr Cejka, Ulrich Rass
Cells have evolved mechanisms to protect, restart and repair perturbed replication forks, allowing full genome duplication, even under replication stress. Interrogating the interplay between nuclease-helicase Dna2 and Holliday junction (HJ) resolvase Yen1, we find the Dna2 helicase activity acts parallel to homologous recombination (HR) in promoting DNA replication and chromosome detachment at mitosis after replication fork stalling. Yen1, but not the HJ resolvases Slx1-Slx4 and Mus81-Mms4, safeguards chromosome segregation by removing replication intermediates that escape Dna2...
October 25, 2016: Nature Communications
https://www.readbyqxmd.com/read/27771863/solution-nmr-structure-of-the-hltf-hiran-domain-a-conserved-module-in-swi2-snf2-dna-damage-tolerance-proteins
#15
Dmitry M Korzhnev, Dante Neculai, Sirano Dhe-Paganon, Cheryl H Arrowsmith, Irina Bezsonova
HLTF is a SWI2/SNF2-family ATP-dependent chromatin remodeling enzyme that acts in the error-free branch of DNA damage tolerance (DDT), a cellular mechanism that enables replication of damaged DNA while leaving damage repair for a later time. Human HLTF and a closely related protein SHPRH, as well as their yeast homologue Rad5, are multi-functional enzymes that share E3 ubiquitin-ligase activity required for activation of the error-free DDT. HLTF and Rad5 also function as ATP-dependent dsDNA translocases and possess replication fork reversal activities...
October 22, 2016: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/27736945/characterization-of-the-neisseria-meningitidis-helicase-recg
#16
Getachew Tesfaye Beyene, Seetha V Balasingham, Stephan A Frye, Amine Namouchi, Håvard Homberset, Shewit Kalayou, Tahira Riaz, Tone Tønjum
Neisseria meningitidis (Nm) is a Gram-negative oral commensal that opportunistically can cause septicaemia and/or meningitis. Here, we overexpressed, purified and characterized the Nm DNA repair/recombination helicase RecG (RecGNm) and examined its role during genotoxic stress. RecGNm possessed ATP-dependent DNA binding and unwinding activities in vitro on a variety of DNA model substrates including a Holliday junction (HJ). Database searching of the Nm genomes identified 49 single nucleotide polymorphisms (SNPs) in the recGNm including 37 non-synonymous SNPs (nsSNPs), and 7 of the nsSNPs were located in the codons for conserved active site residues of RecGNm...
2016: PloS One
https://www.readbyqxmd.com/read/27669035/e4-ligase-specific-ubiquitination-hubs-coordinate-dna-double-strand-break-repair-and-apoptosis
#17
Leena Ackermann, Michael Schell, Wojciech Pokrzywa, Éva Kevei, Anton Gartner, Björn Schumacher, Thorsten Hoppe
Multiple protein ubiquitination events at DNA double-strand breaks (DSBs) regulate damage recognition, signaling and repair. It has remained poorly understood how the repair process of DSBs is coordinated with the apoptotic response. Here, we identified the E4 ubiquitin ligase UFD-2 as a mediator of DNA-damage-induced apoptosis in a genetic screen in Caenorhabditis elegans. We found that, after initiation of homologous recombination by RAD-51, UFD-2 forms foci that contain substrate-processivity factors including the ubiquitin-selective segregase CDC-48 (p97), the deubiquitination enzyme ATX-3 (Ataxin-3) and the proteasome...
September 26, 2016: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/27611966/correlation-between-mtdna-complexity-and-mtdna-replication-mode-in-developing-cotyledon-mitochondria-during-mung-bean-seed-germination
#18
Ning Cheng, Yih-Shan Lo, Mohammad Israil Ansari, Kuo-Chieh Ho, Shih-Tong Jeng, Na-Sheng Lin, Hwa Dai
The currently accepted model of recombination-dependent replication (RDR) in plant mitochondrial DNA (mtDNA) does not clearly explain how RDR progresses and how highly complex mtDNA develops. This study aimed to investigate the correlation between RDR and mtDNA complexity during mitochondrial development in mung bean (Vigna radiata) seed, and the initiation and processing of RDR in plant mitochondria. Flow cytometry, pulsed-field gel electrophoresis, electron microscopy, real-time PCR and biochemical studies were used in this study...
January 2017: New Phytologist
https://www.readbyqxmd.com/read/27601585/mutator-phenotype-and-dna-double-strand-break-repair-in-blm-helicase-deficient-human-cells
#19
Tetsuya Suzuki, Manabu Yasui, Masamitsu Honma
Bloom syndrome (BS), an autosomal recessive disorder of the BLM gene, predisposes sufferers to various cancers. To investigate the mutator phenotype and genetic consequences of DNA double-strand breaks (DSBs) in BS cells, we developed BLM helicase-deficient human cells by disrupting the BLM gene. Cells with a loss of heterozygosity (LOH) due to homologous recombination (HR) or nonhomologous end joining (NHEJ) can be restored with or without site-directed DSB induction. BLM cells exhibited a high frequency of spontaneous interallelic HR with crossover, but noncrossover events with long-tract gene conversions also occurred...
December 1, 2016: Molecular and Cellular Biology
https://www.readbyqxmd.com/read/27565373/reduced-kinase-activity-of-polo-kinase-cdc5-affects-chromosome-stability-and-dna-damage-response-in-s-cerevisiae
#20
Chetan C Rawal, Sara Riccardo, Chiara Pesenti, Matteo Ferrari, Federica Marini, Achille Pellicioli
Polo-like kinases (PLKs) control several aspects of eukaryotic cell division and DNA damage response. Remarkably, PLKs are overexpressed in several types of cancer, being therefore a marker of bad prognosis. As such, specific PLK kinase activity inhibitors are already used in clinical trials and the regulation of PLK activation is a relevant topic of cancer research. Phosphorylation of threonine residues in the T-loop of the kinase domain is pivotal for PLKs activation. Here, we show that T238A substitution in the T-loop reduces the kinase activity of Cdc5, the only PLK in Saccharomyces cerevisiae, with minor effect on cell growth in unperturbed conditions...
November 2016: Cell Cycle
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