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https://www.readbyqxmd.com/read/28228480/a-stable-but-reversible-integrated-surrogate-reporter-for-assaying-crispr-cas9-stimulated-homology-directed-repair
#1
Yahong Wen, Grace Liao, Thomas Pritchard, Ting-Ting Zhao, Jon P Connelly, Shondra M Pruett-Miller, Valerie Blanc, Nicholas O Davidson, Blair B Madison
The discovery and application of CRISPR/Cas9 technology for genome editing has greatly accelerated targeted mutagenesis in a variety of organisms. CRISPR/Cas9-mediated site-specific cleavage is typically exploited for the generation of insertions or deletions (indels) following aberrant dsDNA repair via the endogenous non-homology end-joining (NHEJ) pathway, or alternatively, for enhancing homology directed repair (HDR) to facilitate the generation of a specific mutation (or knock-in). However, there is a need for efficient cellular assays that can measure Cas9/guide RNA (gRNA) activity...
February 22, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28226772/computational-analysis-of-androgen-receptor-dependent-radiosensitivity-in-prostate-cancer
#2
Mengdi Qian, Alexandru Almasan, Evren Gurkan-Cavusoglu, Mengdi Qian, Alexandru Almasan, Evren Gurkan-Cavusoglu, Mengdi Qian, Evren Gurkan-Cavusoglu, Alexandru Almasan
In this study, we quantitatively analyze the mechanism by which androgen deprivation therapy (ADT) is enhancing radiosensitivity in prostate cancer (PCa) patients. It has been shown in laboratory experiments, as well as in patient data in the literature, that the androgen receptor (AR) reduces the effectiveness of ionizing radiation treatment by enhancing the non-homologous end joining (NHEJ) repair of radiation damage. The suppression of AR by ADT suppresses the activity of NHEJ that leads to radiosensitivity in PCa patients...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28216226/nbs1-phosphorylation-status-dictates-repair-choice-of-dysfunctional-telomeres
#3
Rekha Rai, Chunyi Hu, Cayla Broton, Yong Chen, Ming Lei, Sandy Chang
Telomeres employ TRF2 to protect chromosome ends from activating the DNA damage sensor MRE11-RAD50-NBS1 (MRN), thereby repressing ATM-dependent DNA damage checkpoint responses. How TRF2 prevents MRN activation at dysfunctional telomeres is unclear. Here, we show that the phosphorylation status of NBS1 determines the repair pathway choice of dysfunctional telomeres. The crystal structure of the TRF2-NBS1 complex at 3.0 Å resolution shows that the NBS1 429YQLSP433 motif interacts specifically with the TRF2(TRFH) domain...
February 8, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212417/splitax-a-novel-method-to-assess-the-function-of-engineered-nucleases
#4
Richard A Axton, Sharmin S Haideri, Martha Lopez-Yrigoyen, Helen A Taylor, Lesley M Forrester
Engineered nucleases have been used to generate knockout or reporter cell lines and a range of animal models for human disease. These new technologies also hold great promise for therapeutic genome editing. Current methods to evaluate the activity of these nucleases are time consuming, require extensive optimization and are hampered by readouts with low signals and high background. We have developed a simple and easy to perform method (SplitAx) that largely addresses these issues and provides a readout of nuclease activity...
2017: PloS One
https://www.readbyqxmd.com/read/28211448/cx-5461-is-a-dna-g-quadruplex-stabilizer-with-selective-lethality-in-brca1-2-deficient-tumours
#5
Hong Xu, Marco Di Antonio, Steven McKinney, Veena Mathew, Brandon Ho, Nigel J O'Neil, Nancy Dos Santos, Jennifer Silvester, Vivien Wei, Jessica Garcia, Farhia Kabeer, Daniel Lai, Priscilla Soriano, Judit Banáth, Derek S Chiu, Damian Yap, Daniel D Le, Frank B Ye, Anni Zhang, Kelsie Thu, John Soong, Shu-Chuan Lin, Angela Hsin Chin Tsai, Tomo Osako, Teresa Algara, Darren N Saunders, Jason Wong, Jian Xian, Marcel B Bally, James D Brenton, Grant W Brown, Sohrab P Shah, David Cescon, Tak W Mak, Carlos Caldas, Peter C Stirling, Phil Hieter, Shankar Balasubramanian, Samuel Aparicio
G-quadruplex DNAs form four-stranded helical structures and are proposed to play key roles in different cellular processes. Targeting G-quadruplex DNAs for cancer treatment is a very promising prospect. Here, we show that CX-5461 is a G-quadruplex stabilizer, with specific toxicity against BRCA deficiencies in cancer cells and polyclonal patient-derived xenograft models, including tumours resistant to PARP inhibition. Exposure to CX-5461, and its related drug CX-3543, blocks replication forks and induces ssDNA gaps or breaks...
February 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28207808/autologous-hematopoietic-stem-cell-transplantation-in-lymphoma-patients-is-associated-with-a-decrease-in-the-double-strand-break-repair-capacity-of-peripheral-blood-lymphocytes
#6
Sandrine Lacoste, Smita Bhatia, Yanjun Chen, Ravi Bhatia, Timothy R O'Connor
Patients who undergo autologous hematopoietic stem cell transplantation (aHCT) for treatment of a relapsed or refractory lymphoma are at risk of developing therapy related- myelodysplasia/acute myeloid leukemia (t-MDS/AML). Part of the risk likely resides in inherent interindividual differences in their DNA repair capacity (DRC), which is thought to influence the effect chemotherapeutic treatments have on the patient's stem cells prior to aHCT. Measuring DRC involves identifying small differences in repair proficiency among individuals...
2017: PloS One
https://www.readbyqxmd.com/read/28186989/inhibiting-dna-pkcs-in-a-non-homologous-end-joining-pathway-in-response-to-dna-double-strand-breaks
#7
Jun Dong, Tian Zhang, Yufeng Ren, Zhenyu Wang, Clifton C Ling, Fuqiu He, Gloria C Li, Chengtao Wang, Bixiu Wen
DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a distinct factor in the non-homologous end-joining (NHEJ) pathway involved in DNA double-strand break (DSB) repair. We examined the crosstalk between key proteins in the DSB NHEJ repair pathway and cell cycle regulation and found that mouse embryonic fibroblast (MEF) cells deficient in DNA-PKcs or Ku70 were more vulnerable to ionizing radiation (IR) compared with wild-type cells and that DSB repair was delayed. γH2AX was associated with phospho-Ataxia-telangiectasia mutated kinase (Ser1987) and phospho-checkpoint effector kinase 1 (Ser345) foci for the arrest of cell cycle through the G2/M phase...
February 7, 2017: Oncotarget
https://www.readbyqxmd.com/read/28177771/precision-genome-editing-in-the-crispr-era
#8
Jayme Salsman, Graham Dellaire
With the introduction of precision genome editing using CRISPR/Cas9 technology, we have entered a new era of genetic engineering and gene therapy. With RNA-guided endonucleases, such as Cas9, it is possible to engineer DNA double strand breaks (DSB) at specific genomic loci. DSB repair by the error-prone non-homologous end joining (NHEJ) pathway can disrupt a target gene by generating insertions and deletions. Alternatively, Cas9-mediated DSBs can be repaired by homology directed repair (HDR) using a homologous DNA repair template, thus allowing precise gene editing by incorporating genetic changes into the repair template...
September 29, 2016: Biochemistry and Cell Biology, Biochimie et Biologie Cellulaire
https://www.readbyqxmd.com/read/28176781/rad52-competes-with-ku70-ku86-for-binding-to-s-region-dsb-ends-to-modulate-antibody-class-switch-dna-recombination
#9
Hong Zan, Connie Tat, Zhifang Qiu, Julia R Taylor, Justin A Guerrero, Tian Shen, Paolo Casali
Antibody class-switch DNA recombination (CSR) is initiated by AID-introduced DSBs in the switch (S) regions targeted for recombination, as effected by Ku70/Ku86-mediated NHEJ. Ku-deficient B cells, however, undergo (reduced) CSR through an alternative(A)-NHEJ pathway, which introduces microhomologies in S-S junctions. As microhomology-mediated end-joining requires annealing of single-strand DNA ends, we addressed the contribution of single-strand annealing factors HR Rad52 and translesion DNA polymerase θ to CSR...
February 8, 2017: Nature Communications
https://www.readbyqxmd.com/read/28163277/cloning-localization-and-focus-formation-at-dna-damage-sites-of-canine-ku70
#10
Manabu Koike, Yasutomo Yutoku, Aki Koike
Understanding the molecular mechanisms of DNA double-strand break (DSB) repair machinery, specifically non-homologous DNA-end joining (NHEJ), is crucial for developing next-generation radiotherapies and common chemotherapeutics for human and animal cancers. The localization, protein-protein interactions and post-translational modifications of core NHEJ factors, might play vital roles for regulation of NHEJ activity. The human Ku heterodimer (Ku70/Ku80) is a core NHEJ factor in the NHEJ pathway and is involved in sensing of DSBs...
February 6, 2017: Journal of Veterinary Medical Science
https://www.readbyqxmd.com/read/28154079/dna-pkcs-structure-suggests-an-allosteric-mechanism-modulating-dna-double-strand-break-repair
#11
Bancinyane L Sibanda, Dimitri Y Chirgadze, David B Ascher, Tom L Blundell
DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a central component of nonhomologous end joining (NHEJ), repairing DNA double-strand breaks that would otherwise lead to apoptosis or cancer. We have solved its structure in complex with the C-terminal peptide of Ku80 at 4.3 angstrom resolution using x-ray crystallography. We show that the 4128-amino acid structure comprises three large structural units: the N-terminal unit, the Circular Cradle, and the Head. Conformational differences between the two molecules in the asymmetric unit are correlated with changes in accessibility of the kinase active site, which are consistent with an allosteric mechanism to bring about kinase activation...
February 3, 2017: Science
https://www.readbyqxmd.com/read/28133776/non-homologous-end-joining-common-interaction-sites-and-exchange-of-multiple-factors-in-the-dna-repair-process
#12
Stuart L Rulten, Gabrielle J Grundy
Non-homologous end-joining (NHEJ) is the dominant means of repairing chromosomal DNA double strand breaks (DSBs), and is essential in human cells. Fifteen or more proteins can be involved in the detection, signalling, synapsis, end-processing and ligation events required to repair a DSB, and must be assembled in the confined space around the DNA ends. We review here a number of interaction points between the core NHEJ components (Ku70, Ku80, DNA-PKcs, XRCC4 and Ligase IV) and accessory factors such as kinases, phosphatases, polymerases and structural proteins...
March 2017: BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology
https://www.readbyqxmd.com/read/28132842/dna-double-strand-break-resection-occurs-during-non-homologous-end-joining-in-g1-but-is-distinct-from-resection-during-homologous-recombination
#13
Ronja Biehs, Monika Steinlage, Olivia Barton, Szilvia Juhász, Julia Künzel, Julian Spies, Atsushi Shibata, Penny A Jeggo, Markus Löbrich
Canonical non-homologous end joining (c-NHEJ) repairs DNA double-strand breaks (DSBs) in G1 cells with biphasic kinetics. We show that DSBs repaired with slow kinetics, including those localizing to heterochromatic regions or harboring additional lesions at the DSB site, undergo resection prior to repair by c-NHEJ and not alt-NHEJ. Resection-dependent c-NHEJ represents an inducible process during which Plk3 phosphorylates CtIP, mediating its interaction with Brca1 and promoting the initiation of resection. Mre11 exonuclease, EXD2, and Exo1 execute resection, and Artemis endonuclease functions to complete the process...
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28130555/xpf-knockout-via-crispr-cas9-reveals-that-ercc1-is-retained-in-the-cytoplasm-without-its-heterodimer-partner-xpf
#14
Janin Lehmann, Christina Seebode, Sabine Smolorz, Steffen Schubert, Steffen Emmert
The XPF/ERCC1 heterodimeric complex is essentially involved in nucleotide excision repair (NER), interstrand crosslink (ICL), and double-strand break repair. Defects in XPF lead to severe diseases like xeroderma pigmentosum (XP). Up until now, XP-F patient cells have been utilized for functional analyses. Due to the multiple roles of the XPF/ERCC1 complex, these patient cells retain at least one full-length allele and residual repair capabilities. Despite the essential function of the XPF/ERCC1 complex for the human organism, we successfully generated a viable immortalised human XPF knockout cell line with complete loss of XPF using the CRISPR/Cas9 technique in fetal lung fibroblasts (MRC5Vi cells)...
January 27, 2017: Cellular and Molecular Life Sciences: CMLS
https://www.readbyqxmd.com/read/28125611/lung-basal-stem-cells-rapidly-repair-dna-damage-using-the-error-prone-nonhomologous-end-joining-pathway
#15
Clare E Weeden, Yunshun Chen, Stephen B Ma, Yifang Hu, Georg Ramm, Kate D Sutherland, Gordon K Smyth, Marie-Liesse Asselin-Labat
Lung squamous cell carcinoma (SqCC), the second most common subtype of lung cancer, is strongly associated with tobacco smoking and exhibits genomic instability. The cellular origins and molecular processes that contribute to SqCC formation are largely unexplored. Here we show that human basal stem cells (BSCs) isolated from heavy smokers proliferate extensively, whereas their alveolar progenitor cell counterparts have limited colony-forming capacity. We demonstrate that this difference arises in part because of the ability of BSCs to repair their DNA more efficiently than alveolar cells following ionizing radiation or chemical-induced DNA damage...
January 2017: PLoS Biology
https://www.readbyqxmd.com/read/28119335/dna-double-strand-break-repair-in-penaeus-monodon-is-predominantly-dependent-on-homologous-recombination
#16
Shikha Srivastava, Sumedha Dahal, Sharanya J Naidu, Deepika Anand, Vidya Gopalakrishnan, Rajendran Kooloth Valappil, Sathees C Raghavan
DNA double-strand breaks (DSBs) are mostly repaired by nonhomologous end joining (NHEJ) and homologous recombination (HR) in higher eukaryotes. In contrast, HR-mediated DSB repair is the major double-strand break repair pathway in lower order organisms such as bacteria and yeast. Penaeus monodon, commonly known as black tiger shrimp, is one of the economically important crustaceans facing large-scale mortality due to exposure to infectious diseases. The animals can also get exposed to chemical mutagens under the culture conditions as well as in wild...
January 24, 2017: DNA Research: An International Journal for Rapid Publication of Reports on Genes and Genomes
https://www.readbyqxmd.com/read/28119062/baculovirus-based-genome-editing-in-primary-cells
#17
Maysam Mansouri, Zahra Ehsaei, Verdon Taylor, Philipp Berger
Genome editing in eukaryotes became easier in the last years with the development of nucleases that induce double strand breaks in DNA at user-defined sites. CRISPR/Cas9-based genome editing is currently one of the most powerful strategies. In the easiest case, a nuclease (e.g. Cas9) and a target defining guide RNA (gRNA) are transferred into a target cell. Non-homologous end joining (NHEJ) repair of the DNA break following Cas9 cleavage can lead to inactivation of the target gene. Specific repair or insertion of DNA with Homology Directed Repair (HDR) needs the simultaneous delivery of a repair template...
January 22, 2017: Plasmid
https://www.readbyqxmd.com/read/28118392/creation-of-novel-protein-variants-with-crispr-cas9-mediated-mutagenesis-turning-a-screening-by-product-into-a-discovery-tool
#18
Katherine F Donovan, Mudra Hegde, Meagan Sullender, Emma W Vaimberg, Cory M Johannessen, David E Root, John G Doench
CRISPR/Cas9 screening has proven to be a versatile tool for genomics research. Based on unexpected results from a genome-wide screen, we developed a CRISPR/Cas9-mediated approach to mutagenesis, exploiting the allelic diversity generated by error-prone non-homologous end-joining (NHEJ) to identify novel gain-of-function and drug resistant alleles of the MAPK signaling pathway genes MEK1 and BRAF. We define the parameters of a scalable technique to easily generate cell populations containing thousands of endogenous allelic variants to map gene functions...
2017: PloS One
https://www.readbyqxmd.com/read/28118114/coordination-of-the-ser2056-and-thr2609-clusters-of-dna-pkcs-in-regulating-gamma-rays-and-extremely-low-fluencies-of-alpha-particle-irradiation-to-g0-g1-phase-cells
#19
Hatsumi Nagasawa, Yu-Fen Lin, Takamitsu A Kato, John R Brogan, Hung-Ying Shih, Akihiro Kurimasa, Joel S Bedford, Benjamin P C Chen, John B Little
The catalytic subunit of DNA dependent protein kinase (DNA-PKcs) and its kinase activity are critical for mediation of non-homologous end-joining (NHEJ) of DNA double-strand breaks (DSB) in mammalian cells after gamma-ray irradiation. Additionally, DNA-PKcs phosphorylations at the T2609 cluster and the S2056 cluster also affect DSB repair and cellular sensitivity to gamma radiation. Previously we reported that phosphorylations within these two regions affect not only NHEJ but also homologous recombination repair (HRR) dependent DSB repair...
February 2017: Radiation Research
https://www.readbyqxmd.com/read/28114701/-genome-editing-tools-and-their-application-in-experimental-ophthalmology
#20
M Yanik, W Wende, K Stieger
New genome editing tools in molecular biology are revolutionising precise genome surgery and have greatly influenced experimental ophthalmology too. Aside from the commonly used nuclease-based platforms, such as the zinc-finger nucleases (ZFN) and transcription activator-like effector nucleases (TALEN), CRISPR/Cas systems, clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) genes, perform very efficiently in site-specific DNA cleavage within living cells. DNA double strand breaks (DSB) are repaired through two different conserved repair pathways: NHEJ (non-homologous end joining) and HDR (homology directed repair)...
January 23, 2017: Klinische Monatsblätter Für Augenheilkunde
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