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https://www.readbyqxmd.com/read/29352017/keeping-it-real-mrx-sae2-clipping-of-natural-substrates
#1
REVIEW
Robert Gnügge, Lorraine S Symington
The yeast Mre11-Rad50-Xrs2 (MRX) complex and Sae2 function together to initiate DNA end resection, an essential early step in homology-dependent repair of DNA double-strand breaks (DSBs). In this issue of Genes & Development, Wang and colleagues (pp. 2331-2336) and Reginato and colleagues (pp. 2325-2330) report that a variety of physiological protein blocks, including Ku, RPA, and nucleosomes, stimulate MRX-Sae2 endonuclease cleavage in vitro. These studies have important implications for how cells deal with a range of barriers to end resection and highlight the crucial role of Sae2 in activating MRX cleavage at the correct cell cycle stage...
December 1, 2017: Genes & Development
https://www.readbyqxmd.com/read/29340025/the-novel-atm-inhibitor-az31-enhances-antitumor-activity-in-patient-derived-xenografts-that-are-resistant-to-irinotecan-monotherapy
#2
Justin Greene, Anna Nguyen, Stacey M Bagby, Gemma N Jones, W M Tai, Kevin S Quackenbush, Anna Schreiber, Wells A Messersmith, Kalpana M Devaraj, Patrick Blatchford, S Gail Eckhardt, Elaine B Cadogan, Gareth D Hughes, Aaron Smith, Todd M Pitts, John J Arcaroli
Irinotecan, a standard of care therapy for CRC, elicits cytotoxic effects by generating double strand breaks resulting in DNA damage. The activation of the ATM pathway plays a fundamental role in regulating the cellular response and repair to DNA damage. The objective of this preclinical study was to determine whether ATM inhibition would enhance sensitivity to irinotecan treatment. Treatment effects of AZ31, irinotecan or AZ31 + irinotecan were investigated in CRC cell lines and CRC patient derived xenografts...
December 19, 2017: Oncotarget
https://www.readbyqxmd.com/read/29322791/targeting-rad50-increases-sensitivity-to-radiotherapy-in-colorectal-cancer-cells
#3
C Chen, Y Wang, J F Mei, S S Li, H X Xu, H P Xiong, X H Wang, X He
Radiotherapy resistance remains the major factor limiting the radiotherapy efficacy in colorectal cancer. The Mre11-RAD50-Nbs1 (MRN) complex is known to play a critical role in the DNA double strand breaks (DSBs) repair pathways and thus facilitates radioresistance. Targeting MRN function can sensitize cancer cells to irradiation in some malignancies. In this study, we stably knocked down RAD50 protein in colorectal cancer (CRC) cell lines, HCT116 and DLD1, and evaluated their response to irradiation as well as the DSB repair dynamics...
2018: Neoplasma
https://www.readbyqxmd.com/read/29321179/physiological-protein-blocks-direct-the-mre11-rad50-xrs2-and-sae2-nuclease-complex-to-initiate-dna-end-resection
#4
Giordano Reginato, Elda Cannavo, Petr Cejka
DNA double-strand break repair by homologous recombination is initiated by DNA end resection, which is commenced by the Mre11-Rad50-Xrs2 complex and Sae2 in yeast. Here we report that the nonhomologous end joining factor Ku limits the exonuclease activity of Mre11 and promotes its endonuclease to cleave 5'-terminated DNA strands at break sites. Following initial endonucleolytic cleavage past the obstacle, Exo1 specifically extends the resection track, leading to the generation of long 3' overhangs that are required for homologous recombination...
January 10, 2018: Genes & Development
https://www.readbyqxmd.com/read/29321177/plasticity-of-the-mre11-rad50-xrs2-sae2-nuclease-ensemble-in-the-processing-of-dna-bound-obstacles
#5
Weibin Wang, James M Daley, Youngho Kwon, Danielle S Krasner, Patrick Sung
The budding yeast Mre11-Rad50-Xrs2 (MRX) complex and Sae2 function together in DNA end resection during homologous recombination. Here we show that the Ku complex shields DNA ends from exonucleolytic digestion but facilitates endonucleolytic scission by MRX with a dependence on ATP and Sae2. The incision site is enlarged into a DNA gap via the exonuclease activity of MRX, which is stimulated by Sae2 without ATP being present. RPA renders a partially resected or palindromic DNA structure susceptible to MRX-Sae2, and internal protein blocks also trigger DNA cleavage...
January 10, 2018: Genes & Development
https://www.readbyqxmd.com/read/29317520/atm-directs-dna-damage-responses-and-proteostasis-via-genetically-separable-pathways
#6
Ji-Hoon Lee, Michael R Mand, Chung-Hsuan Kao, Yi Zhou, Seung W Ryu, Alicia L Richards, Joshua J Coon, Tanya T Paull
The protein kinase ATM is a master regulator of the DNA damage response but also responds directly to oxidative stress. Loss of ATM causes ataxia telangiectasia, a neurodegenerative disorder with pleiotropic symptoms that include cerebellar dysfunction, cancer, diabetes, and premature aging. We genetically separated the activation of ATM by DNA damage from that by oxidative stress using separation-of-function mutations. We found that deficient activation of ATM by the Mre11-Rad50-Nbs1 complex and DNA double-strand breaks resulted in loss of cell viability, checkpoint activation, and DNA end resection in response to DNA damage...
January 9, 2018: Science Signaling
https://www.readbyqxmd.com/read/29285240/molecular-basis-for-the-dna-damage-induction-and-anticancer-activity-of-asymmetrically-substituted-anthrapyridazone-pdz-7
#7
Majus Misiak, Mateusz Heldt, Marlena Szeligowska, Stefania Mazzini, Leonardo Scaglioni, Grzegorz J Grabe, Marcin Serocki, Jan Lica, Marta Switalska, Joanna Wietrzyk, Giovanni L Beretta, Paola Perego, Dominik Zietkowski, Maciej Baginski, Edward Borowski, Andrzej Skladanowski
Anthrapyridazones, imino analogues of anthraquinone, constitute a family of compounds with remarkable anti-cancer activity. To date, over 20 derivatives were studied, of which most displayed nanomolar cytotoxicity towards broad spectrum of cancer cells, including breast, prostate and leukemic ones. BS-154, the most potent derivative, had IC50 values close to 1 nM, however, it was toxic in animal studies. Here, we characterize another anthrapyridazone, PDZ-7, which retains high cytotoxicity while being well tolerated in mice...
December 1, 2017: Oncotarget
https://www.readbyqxmd.com/read/29273315/staphylococcus-aureus-triggers-induction-of-mir-15b-5p-to-diminish-dna-repair-and-de-regulate-inflammatory-response-in-diabetic-foot-ulcers
#8
Horacio A Ramirez, Irena Pastar, Ivan Jozic, Olivera Stojadinovic, Rivka C Stone, Nkemcho Ojeh, Joel Gil, Stephen C Davis, Robert S Kirsner, Marjana Tomic-Canic
Diabetic foot ulcers (DFUs) are a debilitating complication of diabetes in which bacterial presence, including its frequent colonizer Staphylococcus aureus, contribute to inhibition of healing. MicroRNAs (miRs) play a role in healing and host response to bacterial pathogens. However, the mechanisms by which miR response to cutaneous S. aureus contributes to DFU pathophysiology are unknown. Herein we show S. aureus inhibits wound closure and induces miR-15b-5p in acute human and porcine wound models, and in chronic DFUs...
December 19, 2017: Journal of Investigative Dermatology
https://www.readbyqxmd.com/read/29208713/sbcc-sbcd-and-exoi-process-convergent-forks-to-complete-chromosome-replication
#9
Brian M Wendel, Jessica M Cole, Charmain T Courcelle, Justin Courcelle
SbcC-SbcD are the bacterial orthologs of Mre11-Rad50, a nuclease complex essential for genome stability, normal development, and viability in mammals. In vitro, these enzymes degrade long DNA palindromic structures. When inactivated along with ExoI in Escherichia coli, or Sae2 in eukaryotes, palindromic amplifications arise and propagate in cells. However, long DNA palindromes are not normally found in bacterial or human genomes, leaving the cellular substrates and function of these enzymes unknown. Here, we show that during the completion of DNA replication, convergent replication forks form a palindrome-like structural intermediate that requires nucleolytic processing by SbcC-SbcD and ExoI before chromosome replication can be completed...
December 5, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29189711/early-postoperative-low-expression-of-rad50-in-rectal-cancer-patients-associates-with-disease-free-survival
#10
Vincent Ho, Liping Chung, Amandeep Singh, Vivienne Lea, Maxine Revoltar, Stephanie H Lim, Thein-Ga Tut, Weng Ng, Mark Lee, Paul de Souza, Joo-Shik Shin, Cheok Soon Lee
BACKGROUND: Molecular biomarkers have the potential to predict response to the treatment of rectal cancer. In this study, we aimed to evaluate the prognostic and clinicopathological implication of RAD50 (DNA repair protein RAD50 homolog) expression in rectal cancer. METHODS: A total of 266 rectal cancer patients who underwent surgery and received chemo- and radiotherapy between 2000 and 2011 were involved in the study. Postoperative RAD50 expression was determined by immunohistochemistry in surgical samples (n = 266)...
November 30, 2017: Cancers
https://www.readbyqxmd.com/read/29180822/damage-induced-lncrnas-control-the-dna-damage-response-through-interaction-with-ddrnas-at-individual-double-strand-breaks
#11
Flavia Michelini, Sethuramasundaram Pitchiaya, Valerio Vitelli, Sheetal Sharma, Ubaldo Gioia, Fabio Pessina, Matteo Cabrini, Yejun Wang, Ilaria Capozzo, Fabio Iannelli, Valentina Matti, Sofia Francia, G V Shivashankar, Nils G Walter, Fabrizio d'Adda di Fagagna
The DNA damage response (DDR) preserves genomic integrity. Small non-coding RNAs termed DDRNAs are generated at DNA double-strand breaks (DSBs) and are critical for DDR activation. Here we show that active DDRNAs specifically localize to their damaged homologous genomic sites in a transcription-dependent manner. Following DNA damage, RNA polymerase II (RNAPII) binds to the MRE11-RAD50-NBS1 complex, is recruited to DSBs and synthesizes damage-induced long non-coding RNAs (dilncRNAs) from and towards DNA ends...
December 2017: Nature Cell Biology
https://www.readbyqxmd.com/read/29165875/4%C3%AE-hydroxywithanolide-e-selectively-induces-oxidative-dna-damage-for-selective-killing-of-oral-cancer-cells
#12
Jen-Yang Tang, Hurng-Wern Huang, Hui-Ru Wang, Ya-Ching Chan, Jo-Wen Haung, Chih-Wen Shu, Yang-Chang Wu, Hsueh-Wei Chang
Reactive oxygen species (ROS) induction had been previously reported in 4β-hydroxywithanolide (4βHWE)-induced selective killing of oral cancer cells, but the mechanism involving ROS and the DNA damage effect remain unclear. This study explores the role of ROS and oxidative DNA damage of 4βHWE in the selective killing of oral cancer cells. Changes in cell viability, morphology, ROS, DNA double strand break (DSB) signaling (γH2AX foci in immunofluorescence and DSB signaling in western blotting), and oxidative DNA damage (8-oxo-2'deoxyguanosine [8-oxodG]) were detected in 4βHWE-treated oral cancer (Ca9-22) and/or normal (HGF-1) cells...
November 22, 2017: Environmental Toxicology
https://www.readbyqxmd.com/read/29149348/mechanistic-insight-into-the-assembly-of-the-hera-nura-helicase-nuclease-dna-end-resection-complex
#13
Zainab Ahdash, Andy M Lau, Robert Thomas Byrne, Katja Lammens, Alexandra Stüetzer, Henning Urlaub, Paula J Booth, Eamonn Reading, Karl-Peter Hopfner, Argyris Politis
The HerA-NurA helicase-nuclease complex cooperates with Mre11 and Rad50 to coordinate the repair of double-stranded DNA breaks. Little is known, however, about the assembly mechanism and activation of the HerA-NurA. By combining hybrid mass spectrometry with cryo-EM, computational and biochemical data, we investigate the oligomeric formation of HerA and detail the mechanism of nucleotide binding to the HerA-NurA complex from thermophilic archaea. We reveal that ATP-free HerA and HerA-DNA complexes predominantly exist in solution as a heptamer and act as a DNA loading intermediate...
November 16, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/29065514/the-role-of-mdm2-in-promoting-genome-stability-versus-instability
#14
REVIEW
M Reza Saadatzadeh, Adily N Elmi, Pankita H Pandya, Khadijeh Bijangi-Vishehsaraei, Jixin Ding, Christopher W Stamatkin, Aaron A Cohen-Gadol, Karen E Pollok
In cancer, the mouse double minute 2 (MDM2) is an oncoprotein that contributes to the promotion of cell growth, survival, invasion, and therapeutic resistance. The impact of MDM2 on cell survival versus cell death is complex and dependent on levels of MDM2 isoforms, p53 status, and cellular context. Extensive investigations have demonstrated that MDM2 protein-protein interactions with p53 and other p53 family members (p63 and p73) block their ability to function as transcription factors that regulate cell growth and survival...
October 23, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/29030353/rad50-expression-is-associated-with-poor-clinical-outcomes-after-radiotherapy-for-resected-non-small-cell-lung-cancer
#15
Yifan Wang, Jayanthi Gudikote, Uma Giri, Jun Yan, Weiye Deng, Rui Ye, Wen Jiang, Nan Li, Brian Hobbs, Jing Wang, Stephen G Swisher, Junya Fujimoto, Ignacio Ivan Wistuba, Ritsuko Komaki, John Heymach, Steven H Lin
PURPOSE: Although postoperative radiotherapy is often used to maintain local control after surgical resection and chemotherapy for locally advanced non-small cell lung cancer (NSCLC), both locoregional failure and distant metastasis remain problematic.  The mechanisms of therapeutic resistance remain poorly understood.    Experimental Design: We used reverse-phase protein arrays (RPPAs) to profile the baseline expression of 170 total and phosphorylated proteins in 70 NSCLC cell lines to categorize pathways that may contribute to radiation resistance...
October 13, 2017: Clinical Cancer Research: An Official Journal of the American Association for Cancer Research
https://www.readbyqxmd.com/read/29018935/a-curious-new-role-for-mrn-in-schizosaccharomyces-pombe-non-homologous-end-joining
#16
REVIEW
Kurt W Runge, Yanhui Li
Chromosomal breaks can be healed by several repair processes, including one called non-homologous end-joining (NHEJ) where the two broken ends are ligated together with a loss of 0-5 bp of DNA. The protein requirements for NHEJ of cut DNA ends in the budding yeast Saccharomyces cerevisiae include its version of the Mre11-Rad50-Nbs1 (MRN) complex. In contrast, the fission yeast Schizosaccharomyces pombe and mammalian cells do not require MRN for this process. Recent work in S. pombe used transposon excision to generate breaks that were capped by DNA hairpins, which must be opened to produce ligatable ends...
October 10, 2017: Current Genetics
https://www.readbyqxmd.com/read/28970327/genetic-separation-of-sae2-nuclease-activity-from-mre11-nuclease-functions-in-budding-yeast
#17
Sucheta Arora, Rajashree A Deshpande, Martin Budd, Judy Campbell, America Revere, Xiaoming Zhang, Kristina H Schmidt, Tanya T Paull
Sae2 promotes the repair of DNA double-strand breaks in Saccharomyces cerevisiae The role of Sae2 is linked to the Mre11/Rad50/Xrs2 (MRX) complex, which is important for the processing of DNA ends into single-stranded substrates for homologous recombination. Sae2 has intrinsic endonuclease activity, but the role of this activity has not been assessed independently from its functions in promoting Mre11 nuclease activity. Here we identify and characterize separation-of-function mutants that lack intrinsic nuclease activity or the ability to promote Mre11 endonucleolytic activity...
October 2, 2017: Molecular and Cellular Biology
https://www.readbyqxmd.com/read/28967905/akt-overactivation-can-suppress-dna-repair-via-p70s6-kinase-dependent-downregulation-of-mre11
#18
D Piscitello, D Varshney, S Lilla, M G Vizioli, C Reid, V Gorbunova, A Seluanov, D A Gillespie, P D Adams
Deregulated AKT kinase activity due to PTEN deficiency in cancer cells contributes to oncogenesis by incompletely understood mechanisms. Here, we show that PTEN deletion in HCT116 and DLD1 colon carcinoma cells leads to suppression of CHK1 and CHK2 activation in response to irradiation, impaired G2 checkpoint proficiency and radiosensitization. These defects are associated with reduced expression of MRE11, RAD50 and NBS1, components of the apical MRE11/RAD50/NBS1 (MRN) DNA damage response complex. Consistent with reduced MRN complex function, PTEN-deficient cells fail to resect DNA double-strand breaks efficiently after irradiation and show greatly diminished proficiency for DNA repair via the error-free homologous recombination (HR) repair pathway...
October 2, 2017: Oncogene
https://www.readbyqxmd.com/read/28961279/the-frequency-of-cancer-predisposition-gene-mutations-in-hereditary-breast-and-ovarian-cancer-patients-in-taiwan-from-brca1-2-to-multi-gene-panels
#19
Pi-Lin Sung, Kuo-Chang Wen, Yi-Jen Chen, Ta-Chung Chao, Yi-Fang Tsai, Ling-Ming Tseng, Jian-Tai Timothy Qiu, Kuan-Chong Chao, Hua-Hsi Wu, Chi-Mu Chuang, Peng-Hui Wang, Chi-Ying F Huang
An important role of genetic factors in the development of breast cancer (BC) or ovarian cancer (OC) in Taiwanese (ethnic Chinese) patients has been suggested. However, other than germline BRCA1 or BRCA2 mutations, which are related to hereditary breast-ovarian cancer (HBOC), cancer-predisposition genes have not been well studied in this population. The aim of the present study was to more accurately summarize the prevalence of genetic mutations in HBOC patients using various gene panels ranging in size from BRCA1/2 alone to multi-gene panels...
2017: PloS One
https://www.readbyqxmd.com/read/28927087/gimeracil-enhances-the-antitumor-effect-of-cisplatin-in-oral-squamous-cell-carcinoma-cells-in-vitro-and-in-vivo
#20
Koji Harada, Tarannum Ferdous, Toyoko Harada, Takanori Takenawa, Yoshiya Ueyama
Gimeracil or 5-chloro-2,4-dihydroxypyridine (CDHP) enhances the antitumor effects of 5-fluorouracil (5-FU) by inhibiting dihydropyrimidine dehydrogenase (DPD), which is involved in the degradation of 5-FU. CDHP, as part of a combination therapy, was also reported to exert a radiosensitizing effect. Therefore, CDHP may have underlying mechanisms of action other than DPD inhibition. The focus of the present study was to investigate the antitumor effects of CDHP and cisplatin (CDDP) combination treatment in vitro and in vivo against oral squamous cell carcinoma (OSCC) tumors...
September 2017: Oncology Letters
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