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Nonhomologous end joining

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https://www.readbyqxmd.com/read/28930678/dna-ligase-iv-guides-end-processing-choice-during-nonhomologous-end-joining
#1
Michael P Conlin, Dylan A Reid, George W Small, Howard H Chang, Go Watanabe, Michael R Lieber, Dale A Ramsden, Eli Rothenberg
Nonhomologous end joining (NHEJ) must adapt to diverse end structures during repair of chromosome breaks. Here, we investigate the mechanistic basis for this flexibility. DNA ends are aligned in a paired-end complex (PEC) by Ku, XLF, XRCC4, and DNA ligase IV (LIG4); we show by single-molecule analysis how terminal mispairs lead to mobilization of ends within PECs and consequent sampling of more end-alignment configurations. This remodeling is essential for direct ligation of damaged and mispaired ends during cellular NHEJ, since remodeling and ligation of such ends both require a LIG4-specific structural motif, insert1...
September 19, 2017: Cell Reports
https://www.readbyqxmd.com/read/28911097/structural-accommodation-of-ribonucleotide-incorporation-by-the-dna-repair-enzyme-polymerase-mu
#2
Andrea F Moon, John M Pryor, Dale A Ramsden, Thomas A Kunkel, Katarzyna Bebenek, Lars C Pedersen
While most DNA polymerases discriminate against ribonucleotide triphosphate (rNTP) incorporation very effectively, the Family X member DNA polymerase μ (Pol μ) incorporates rNTPs almost as efficiently as deoxyribonucleotides. To gain insight into how this occurs, here we have used X-ray crystallography to describe the structures of pre- and post-catalytic complexes of Pol μ with a ribonucleotide bound at the active site. These structures reveal that Pol μ binds and incorporates a rNTP with normal active site geometry and no distortion of the DNA substrate or nucleotide...
September 6, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28900076/-crispr-cas9-the-king-of-genome-editing-tools
#3
A V Bannikov, A V Lavrov
The discovery of CRISPR/Cas9 brought a hope for having an efficient, reliable, and readily available tool for genome editing. CRISPR/Cas9 is certainly easy to use, while its efficiency and reliability remain the focus of studies. The review describes the general principles of the organization and function of Cas nucleases and a number of important issues to be considered while planning genome editing experiments with CRISPR/Cas9. The issues include evaluation of the efficiency and specificity for Cas9, sgRNA selection, Cas9 variants designed artificially, and use of homologous recombination and nonhomologous end joining in DNA editing...
July 2017: Molekuliarnaia Biologiia
https://www.readbyqxmd.com/read/28893909/processive-searching-ability-varies-among-members-of-the-gap-filling-dna-polymerase-x-family
#4
Michael J Howard, Samuel H Wilson
DNA repair proteins must locate rare damaged sites within the genome. DNA polymerase beta (Pol β), a member of the DNA polymerase X family that is involved in base excision repair, uses a processive hopping search mechanism to locate substrates. This effectively enhances its search footprint on DNA, increasing the probability of locating damaged sites. Processive searching has been reported or proposed for many DNA-binding proteins, raising the question of how widespread or specific to certain enzymes the ability to perform this function is...
September 11, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28887493/molecular-characterization-of-cell-free-eccdnas-in-human-plasma
#5
Jing Zhu, Fan Zhang, Meijun Du, Peng Zhang, Songbin Fu, Liang Wang
Extrachromosomal circular DNAs (eccDNAs) have been reported in most eukaryotes. However, little is known about the cell-free eccDNA profiles in circulating system such as blood. To characterize plasma cell-free eccDNAs, we performed sequencing analysis in 26 libraries from three blood donors and negative controls. We identified thousands of unique plasma eccDNAs in the three subjects. We observed proportional eccDNA increase with initial DNA input. The detected eccDNAs were also associated with circular DNA enrichment efficiency...
September 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28882611/generation-and-crispr-cas9-editing-of-transformed-progenitor-b-cells-as-a-pseudo-physiological-system-to-study-dna-repair-gene-function-in-v-d-j-recombination
#6
Hélène Lenden Hasse, Chloé Lescale, Joy J Bianchi, Wei Yu, Marie Bedora-Faure, Ludovic Deriano
Antigen receptor gene assembly is accomplished in developing lymphocytes by the V(D)J recombination reaction, which can be separated into two steps: DNA cleavage by the recombination-activating gene (RAG) nuclease and joining of DNA double strand breaks (DSBs) by components of the nonhomologous end joining (NHEJ) pathway. Deficiencies for NHEJ factors can result in immunodeficiency and a propensity to accumulate genomic instability, thus highlighting the importance of identifying all players in this process and deciphering their functions...
September 4, 2017: Journal of Immunological Methods
https://www.readbyqxmd.com/read/28860152/proteasome-inhibitor-bortezomib-is-a-novel-therapeutic-agent-for-focal-radiation-induced-osteoporosis
#7
Abhishek Chandra, Luqiang Wang, Tiffany Young, Leilei Zhong, Wei-Ju Tseng, Michael A Levine, Keith Cengel, X Sherry Liu, Yejia Zhang, Robert J Pignolo, Ling Qin
Bone atrophy and its related fragility fractures are frequent, late side effects of radiotherapy in cancer survivors and have a detrimental impact on their quality of life. In another study, we showed that parathyroid hormone 1-34 and anti-sclerostin antibody attenuates radiation-induced bone damage by accelerating DNA repair in osteoblasts. DNA damage responses are partially regulated by the ubiquitin proteasome pathway. In the current study, we examined whether proteasome inhibitors have similar bone-protective effects against radiation damage...
August 31, 2017: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
https://www.readbyqxmd.com/read/28846869/xlf-cernunnos-an-important-but-puzzling-participant-in-the-nonhomologous-end-joining-dna-repair-pathway
#8
REVIEW
Vijay Menon, Lawrence F Povirk
DNA double strand breaks (DSBs) are one of the most deleterious DNA lesions that promote cell death, genomic instability and carcinogenesis. The two major cellular mechanisms that repair DSBs are Nonhomologous End-Joining (NHEJ) and Homologous Recombination Repair (HRR). NHEJ is the predominant pathway, in which XLF (also called Cernunnos) is a key player. Patients with XLF mutation exhibit microcephaly, lymphopenia, and growth retardation, and are immunodeficient and radiosensitive. During NHEJ, XLF interacts with XRCC4-Ligase IV, stimulates its ligase activity, and forms DNA-binding filaments of alternating XLF and XRCC4 dimers that may serve to align broken DNA and promote ligation of noncomplementary ends...
August 18, 2017: DNA Repair
https://www.readbyqxmd.com/read/28832943/crispri-repression-of-nonhomologous-end-joining-for-enhanced-genome-engineering-via-homologous-recombination-in-yarrowia-lipolytica
#9
Cory Schwartz, Keith Frogue, Adithya Ramesh, Joshua Misa, Ian Wheeldon
In many organisms of biotechnological importance precise genome editing is limited by inherently low homologous recombination (HR) efficiencies. A number of strategies exist to increase the effectiveness of this native DNA repair pathway; however, most strategies rely on permanently disabling competing repair pathways, thus reducing an organism's capacity to repair naturally occurring double strand breaks. Here, we describe a CRISPR interference (CRISPRi) system for gene repression in the oleochemical-producing yeast Yarrowia lipolytica...
August 19, 2017: Biotechnology and Bioengineering
https://www.readbyqxmd.com/read/28827551/small-molecules-enhance-crispr-cas9-mediated-homology-directed-genome-editing-in-primary-cells
#10
Guoling Li, Xianwei Zhang, Cuili Zhong, Jianxin Mo, Rong Quan, Jie Yang, Dewu Liu, Zicong Li, Huaqiang Yang, Zhenfang Wu
CRISPR/Cas9 is an efficient customizable nuclease to generate double-strand breaks (DSBs) in the genome. This process results in knockout of the targeted gene or knock-in of a specific DNA fragment at the targeted locus in the genome of various species. However, efficiency of knock-in mediated by homology-directed repair (HDR) pathway is substantially lower compared with the efficiency of knockout mediated by the nonhomologous end-joining (NHEJ) pathway. Suppressing NHEJ pathway or enhancing HDR pathway has been proven to enhance the nuclease-mediated knock-in efficiency in cultured cells and model organisms...
August 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28790200/chromosome-end-repair-and-genome-stability-in-plasmodium-falciparum
#11
Susannah F Calhoun, Jake Reed, Noah Alexander, Christopher E Mason, Kirk W Deitsch, Laura A Kirkman
The human malaria parasite Plasmodium falciparum replicates within circulating red blood cells, where it is subjected to conditions that frequently cause DNA damage. The repair of DNA double-stranded breaks (DSBs) is thought to rely almost exclusively on homologous recombination (HR), due to a lack of efficient nonhomologous end joining. However, given that the parasite is haploid during this stage of its life cycle, the mechanisms involved in maintaining genome stability are poorly understood. Of particular interest are the subtelomeric regions of the chromosomes, which contain the majority of the multicopy variant antigen-encoding genes responsible for virulence and disease severity...
August 8, 2017: MBio
https://www.readbyqxmd.com/read/28739276/a-process-of-resection-dependent-nonhomologous-end-joining-involving-the-goddess-artemis
#12
REVIEW
Markus Löbrich, Penny Jeggo
DNA double-strand breaks (DSBs) are a hazardous form of damage that can potentially cause cell death or genomic rearrangements. In mammalian G1- and G2-phase cells, DSBs are repaired with two-component kinetics. In both phases, a fast process uses canonical nonhomologous end joining (c-NHEJ) to repair the majority of DSBs. In G2, slow repair occurs by homologous recombination. The slow repair process in G1 also involves c-NHEJ proteins but additionally requires the nuclease Artemis and DNA end resection. Here, we consider the nature of slow DSB repair in G1 and evaluate factors determining whether DSBs are repaired with fast or slow kinetics...
September 2017: Trends in Biochemical Sciences
https://www.readbyqxmd.com/read/28729543/evaluation-of-atm-heterozygous-mutations-underlying-individual-differences-in-radiosensitivity-using-genome-editing-in-human-cultured-cells
#13
Ekaterina Royba, Tatsuo Miyamoto, Silvia Natsuko Akutsu, Kosuke Hosoba, Hiroshi Tauchi, Yoshiki Kudo, Satoshi Tashiro, Takashi Yamamoto, Shinya Matsuura
Ionizing radiation (IR) induces DNA double-strand breaks (DSBs), which are an initial step towards chromosomal aberrations and cell death. It has been suggested that there are individual differences in radiosensitivity within human populations, and that the variations in DNA repair genes might determine this heterogeneity. However, it is difficult to quantify the effect of genetic variants on the individual differences in radiosensitivity, since confounding factors such as smoking and the diverse genetic backgrounds within human populations affect radiosensitivity...
July 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28729231/cernunnos-deficiency-associated-with-bcg-adenitis-and-autoimmunity-first-case-from-the-national-iranian-registry-and-review-of-the-literature
#14
Reza Yazdani, Hassan Abolhassani, Javad Tafaroji, Gholamreza Azizi, Raif S Geha, Asghar Aghamohammadi
Non-homologous end-joining (NHEJ) is a pathway that repairs double-strand breaks (DSB) in DNA and plays a vital role in V(D)J recombination of immunoglobulin genes. Cernunnos is a DNA repair factor that is involved in nonhomologous end-joining (NHEJ) process. Impairment in Cernunnos leads to a genetic disease characterized by neural disorders, immunodeficiency and increased radiosensitivity. We herein describe a severe combined immunodeficiency (SCID) patient with T- B+ phenotype who had a mutation in Cernunnos gene and manifested recurrent infections, microcephaly and growth retardation with hypogammaglobulinemia...
July 17, 2017: Clinical Immunology: the Official Journal of the Clinical Immunology Society
https://www.readbyqxmd.com/read/28714989/correction-of-a-splicing-defect-in-a-mouse-model-of-congenital-muscular-dystrophy-type-1a-using-a-homology-directed-repair-independent-mechanism
#15
Dwi U Kemaladewi, Eleonora Maino, Elzbieta Hyatt, Huayun Hou, Maylynn Ding, Kara M Place, Xinyi Zhu, Prabhpreet Bassi, Zahra Baghestani, Amit G Deshwar, Daniele Merico, Hui Y Xiong, Brendan J Frey, Michael D Wilson, Evgueni A Ivakine, Ronald D Cohn
Splice-site defects account for about 10% of pathogenic mutations that cause Mendelian diseases. Prevalence is higher in neuromuscular disorders (NMDs), owing to the unusually large size and multi-exonic nature of genes encoding muscle structural proteins. Therapeutic genome editing to correct disease-causing splice-site mutations has been accomplished only through the homology-directed repair pathway, which is extremely inefficient in postmitotic tissues such as skeletal muscle. Here we describe a strategy using nonhomologous end-joining (NHEJ) to correct a pathogenic splice-site mutation...
August 2017: Nature Medicine
https://www.readbyqxmd.com/read/28712502/gene-editing-with-talen-and-crispr-cas-in-rice
#16
Honghao Bi, Bing Yang
Engineered, site-specific nucleases induce genomic double-strand DNA breaks and break repair processes enable genome editing in a plethora of eukaryotic genomes. TALENs (transcription activator-like effector nucleases) and CRISPR/Cas (clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins) are potent biotechnological tools used for genome editing. In rice, species-tailored editing tools have proven to be efficient and easy to use. Both tools are capable of generating DNA double-strand breaks (DSBs) in vivo and such breaks can be repaired either by error-prone NHEJ (nonhomologous end joining) that leads to nucleotide insertions or deletions or by HDR (homology-directed repair) if an appropriate exogenous DNA template is provided...
2017: Progress in Molecular Biology and Translational Science
https://www.readbyqxmd.com/read/28696258/effects-of-dna-end-configuration-on-xrcc4-dna-ligase-iv-and-its-stimulation-of-artemis-activity
#17
Christina A Gerodimos, Howard H Y Chang, Go Watanabe, Michael R Lieber
In humans, nonhomologous DNA end-joining (NHEJ) is the major pathway by which DNA double-strand breaks are repaired. Recognition of each broken DNA end by the DNA repair protein Ku is the first step in NHEJ, followed by the iterative binding of nucleases, DNA polymerases, and the XRCC4-DNA ligase IV (X4-LIV) complex in an order influenced by the configuration of the two DNA ends at the break site. The endonuclease Artemis improves joining efficiency by functioning in a complex with DNA-dependent protein kinase, catalytic subunit (DNA-PKcs) that carries out endonucleolytic cleavage of 5' and 3' overhangs...
August 25, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28674816/crispr-cas9-mediated-gene-editing-in-mouse-spermatogonial-stem-cells
#18
Yinghua Wang, Yifu Ding, Jinsong Li
Precise genome editing is a powerful tool for analysis of gene function. However, in spermatogonial stem cells (SSCs), this still remains a big challenge mainly due to low efficiency and complexity of currently available gene editing techniques. The CRISPR-Cas9 system from bacteria has been applied to modifying genome in different species at a very high efficiency and specificity. Here we describe CRISPR-Cas9-mediated gene editing via nonhomologous end joining (NHEJ) or homology-directed repair (HDR) in SSCs...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28668129/what-combined-measurements-from-structures-and-imaging-tell-us-about-dna-damage-responses
#19
Chris A Brosey, Zamal Ahmed, Susan P Lees-Miller, John A Tainer
DNA damage outcomes depend upon the efficiency and fidelity of DNA damage responses (DDRs) for different cells and damage. As such, DDRs represent tightly regulated prototypical systems for linking nanoscale biomolecular structure and assembly to the biology of genomic regulation and cell signaling. However, the dynamic and multifunctional nature of DDR assemblies can render elusive the correlation between the structures of DDR factors and specific biological disruptions to the DDR when these structures are altered...
2017: Methods in Enzymology
https://www.readbyqxmd.com/read/28668119/dna-pkcs-allostery-and-dna-double-strand-break-repair-defining-the-structure-and-setting-the-stage
#20
Dimitri Y Chirgadze, David B Ascher, Tom L Blundell, Bancinyane L Sibanda
DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is central to the regulation of the DNA damage response and repair through nonhomologous end joining. The structure has proved challenging due to its large size and multiple HEAT repeats. We have recently reported crystals of selenomethionine-labeled DNA-PKcs complexed with native KU80ct194 (KU80 residues 539-732) diffracting to 4.3Å resolution. The novel use of crystals of selenomethionine-labeled protein expressed in HeLa cells has facilitated the use of single anomalous X-ray scattering of this 4128 amino acid, multiple HEAT-repeat structure...
2017: Methods in Enzymology
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