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Bryan A Johnson, Heather L Aloor, Cary A Moody
Human papillomaviruses (HPV) exhibit constitutive activation of ATM and ATR DNA damage response (DDR) pathways, which are required for productive viral replication. Expression of HPV31 E7 alone is sufficient to activate the DDR through an unknown mechanism. Here, we demonstrate that the E7 Rb binding domain is required to increase levels of many DDR proteins, including ATM, Chk2, Chk1, the MRN components MRE11, Rad50, and NBS1, as well as the homologous recombination repair proteins BRCA1 and Rad51. Interestingly, we have found that the increase in these DNA repair proteins does not occur solely at the level of transcription, but that E7 broadly increases the half-life of these DDR factors, a phenotype that is lost in the E7 Rb binding mutant...
October 19, 2016: Virology
R C Yan, J Wang, Z Z Huang, Z Y Wang, X F Wu, J C Huang, L H Chang, D Q Li, G H Zhang
Objective: To investigate the killing effects of radiation and mutant Rad50 transfection on human nasopharyngeal carcinoma cell line CNE1. Methods: The experimental groups included: control group, Ad-Rad50-GFP group, Ad-EGFP group, irradiation group, Ad-Rad50-GFP combined with irradiation group, and Ad-EGFP combined with irradiation group. CNE1 cells were transfected with recombinant adenoviral vector Ad-Rad50-GFP carrying mutant Rad50 gene. The expressions of Mre11, Rad50, Nbs1, and relevant constituents composing MRN complex were detected by Western Blot...
October 7, 2016: Zhonghua Er Bi Yan Hou Tou Jing Wai Ke za Zhi, Chinese Journal of Otorhinolaryngology Head and Neck Surgery
Julyun Oh, Amr Al-Zain, Elda Cannavo, Petr Cejka, Lorraine S Symington
The Mre11-Rad50-Xrs2/Nbs1 (MRX/N) complex orchestrates the cellular response to DSBs through its structural, enzymatic, and signaling roles. Xrs2/Nbs1 is essential for nuclear translocation of Mre11, but its role as a component of the complex is not well defined. Here, we demonstrate that nuclear localization of Mre11 (Mre11-NLS) is able to bypass several functions of Xrs2, including DNA end resection, meiosis, hairpin resolution, and cellular resistance to clastogens. Using purified components, we show that the MR complex has equivalent activity to MRX in cleavage of protein-blocked DNA ends...
October 20, 2016: Molecular Cell
Yong Xu, Xiao Wang, Shi-Ming Chen, Chen Chen, Yan Wang, Bo-Kui Xiao, Ze-Zhang Tao
PURPOSE: To explore the influences of telomerase and alternative lengthening of telomeres mechanism on telomere length and laryngeal squamous cell carcinoma in vitro and in vivo. MATERIALS AND METHODS: Short hairpin RNA expression vectors targeting the messenger TERT, TRF2, RAD51 and NBS1 were constructed. The mRNA and protein expression of targeted genes in human laryngeal squamous carcinoma cell line HEp-2 was evaluated by reverse transcription polymerase chain reaction and Western blotting separately...
September 6, 2016: American Journal of Otolaryngology
José Carlos Páez-Franco, Ignacio González-Sánchez, Nora A Gutiérrez-Nájera, Lilián G Valencia-Turcotte, Alfonso Lira-Rocha, Marco A Cerbón, Rogelio Rodríguez-Sotres
9-[(3-chloro)phenylamine]-2-[3-(diethylamine)propylamine]thiazolo[5,4-b]quinolone (D3ClP) is a bioisostere of N-(4-(acridin-9-ylamino)-3-methoxyphenyl)methanesulfonamide (m-AMSA) a DNA topoisomerase II inhibitor with proven cytotoxic activity and known to induce DNA damage and apoptotic cell death in K562 cells. However, recent evidence is not consistent with DNA topoisomerase II (DNA TOP2) as the primary target of D3ClP, in contrast to m-AMSA. We provide evidence of histone γH2AX phosphorylation at Ser135 in HeLa cells treated with D3ClP, a marker of DNA double strand repair through Mre11-Rad50-Nbs1 (MRN) pathway...
September 29, 2016: Journal of Cellular Biochemistry
Michal Franek, Alena Kovaříková, Eva Bártová, Stanislav Kozubek
DNA damage response (DDR) in ribosomal genes and mechanisms of DNA repair in embryonic stem cells (ESCs) are less explored nuclear events. DDR in ESCs should be unique due to their high proliferation rate, expression of pluripotency factors, and specific chromatin signature. Given short population doubling time and fast progress through G1 phase, ESCs require a sustained production of rRNA, which leads to the formation of large and prominent nucleoli. Although transcription of rRNA in the nucleolus is relatively well understood, little is known about DDR in this nuclear compartment...
September 28, 2016: Journal of Histochemistry and Cytochemistry: Official Journal of the Histochemistry Society
Sameera Nallanthighal, Amit B Shirode, Julius A Judd, Ramune Reliene
Ionizing radiation (IR) is a well-documented human carcinogen. The increased use of IR in medical procedures has doubled the annual radiation dose and may increase cancer risk. Genomic instability is an intermediate lesion in IR-induced cancer. We examined whether pomegranate extract (PE) suppresses genomic instability induced by x-rays. Mice were treated orally with PE and exposed to an x-ray dose of 2 Gy. PE intake suppressed x-ray-induced DNA double-strand breaks (DSBs) in peripheral blood and chromosomal damage in bone marrow...
September 27, 2016: Nutrition and Cancer
Tomas Aparicio, Jean Gautier
DNA termini at double-strand breaks are often chemically heterogeneous and require processing before initiation of repair. In a recent report, we demonstrated that CtIP and the MRE11-RAD50-NBS1 (MRN) nuclease complex cooperate with BRCA1 to specifically repair topoisomerase II-DNA adducted breaks. In contrast, BRCA1 is dispensable for repair of restriction endonuclease-generated double-strand breaks.
July 2016: Molecular & Cellular Oncology
Seung Ho Choi, Hae Yong Yoo
TopBP1 has been identified as a direct activator of ATR and interacts with the Nbs1 subunit of the Mre11-Rad50-Nbs1 (MRN) complex in egg extracts in a checkpoint-regulated manner. In this study, we show that Mdc1 associates with both TopBP1 and Nbs1 in egg extracts and human cells. We cloned a cDNA encoding the full-length version of Xenopus Mdc1. The association between Mdc1 and TopBP1 involves the first pair of BRCT repeats in TopBP1. The N-terminal region (161-230) of Mdc1 is required for this binding. The interaction between Mdc1 and Nbs1 involves the two tandem BRCT repeats of Nbs1...
October 7, 2016: Biochemical and Biophysical Research Communications
Christopher J Staples, Giancarlo Barone, Katie N Myers, Anil Ganesh, Ian Gibbs-Seymour, Abhijit A Patil, Ryan D Beveridge, Caroline Daye, Richard Beniston, Sarah Maslen, Ivan Ahel, J Mark Skehel, Spencer J Collis
Through an RNAi-based screen for previously uncharacterized regulators of genome stability, we have identified the human protein C5orf45 as an important factor in preventing the accumulation of DNA damage in human cells. Here, we functionally characterize C5orf45 as a binding partner of the MRE11-RAD50-NBS1 (MRN) damage-sensing complex. Hence, we rename C5orf45 as MRNIP for MRN-interacting protein (MRNIP). We find that MRNIP is rapidly recruited to sites of DNA damage. Cells depleted of MRNIP display impaired chromatin loading of the MRN complex, resulting in reduced DNA end resection and defective ATM-mediated DNA damage signaling, a reduced ability to repair DNA breaks, and radiation sensitivity...
September 6, 2016: Cell Reports
Tomer Halevy, Shira Akov, Martina Bohndorf, Barbara Mlody, James Adjaye, Nissim Benvenisty, Michal Goldberg
Nijmegen breakage syndrome (NBS) results from the absence of the NBS1 protein, responsible for detection of DNA double-strand breaks (DSBs). NBS is characterized by microcephaly, growth retardation, immunodeficiency, and cancer predisposition. Here, we show successful reprogramming of NBS fibroblasts into induced pluripotent stem cells (NBS-iPSCs). Our data suggest a strong selection for karyotypically normal fibroblasts to go through the reprogramming process. NBS-iPSCs then acquire numerous chromosomal aberrations and show a delayed response to DSB induction...
August 30, 2016: Cell Reports
Dianne I Lou, Eui Tae Kim, Nicholas R Meyerson, Neha J Pancholi, Kareem N Mohni, David Enard, Dmitri A Petrov, Sandra K Weller, Matthew D Weitzman, Sara L Sawyer
Humans occasionally transmit herpes simplex virus 1 (HSV-1) to captive primates, who reciprocally harbor alphaherpesviruses poised for zoonotic transmission to humans. To understand the basis for the species-specific restriction of HSV-1 in primates, we simulated what might happen during the cross-species transmission of HSV-1 and found that the DNA repair protein Nbs1 from only some primate species is able to promote HSV-1 infection. The Nbs1 homologs that promote HSV-1 infection also interact with the HSV-1 ICP0 protein...
August 10, 2016: Cell Host & Microbe
Marcin R Lener, Aniruddh Kashyap, Wojciech Kluźniak, Cezary Cybulski, Agnieszka Soluch, Sandra Pietrzak, Tomasz Huzarski, Jacek Gronwald, Jan Lubiński
Purpose: Familial pancreatic cancer describes families with at least two first-degree relatives with pancreatic cancer that do not fulfil the criteria of other inherited tumor syndromes with increased risks of pancreatic cancer. Although much has been learned regarding the aggregation of pancreatic cancer in some families, the genetic basis for this familial aggregation is poorly understood. This study evaluated the prevalence of 10 Polish founder mutations in 4 genes among individuals from families with diagnosed familial pancreatic cancer syndrome and assessed their possible association with the FPC risk in Poland...
July 28, 2016: Cancer Research and Treatment: Official Journal of Korean Cancer Association
Xiao-Mei Wang, Hang Xiao, Ling-Lin Liu, Dang Cheng, Xue-Jun Li, Liang-Yi Si
Cerebrovascular aging has a high relationship with stroke and neurodegenerative disease. In the present study, we evaluated the influence of fibroblast growth factor 21 (FGF21) on angiotensin (Ang II)-mediated cerebrovascular aging in human brain vascular smooth muscle cells (hBVSMCs). Ang II induced remarkable aging-phenotypes in hBVSMCs, including enhanced SA-β-gal staining and NBS1 protein expression. First, we used immunoblotting assay to confirm protein expression of FGF21 receptor (FGFR1) and the co-receptor β-Klotho in cultured hBVSMCs...
August 15, 2016: Experimental Cell Research
Kristi L Jensen, Paul Russell
Homologous recombination (HR) repair of programmed meiotic double-strand breaks (DSBs) requires endonucleolytic clipping of Rec12(Spo11)-oligonucleotides from 5' DNA ends followed by resection to generate invasive 3' single-stranded DNA tails. The Mre11-Rad50-Nbs1 (MRN) endonuclease and Ctp1 (CtIP and Sae2 ortholog) are required for both activities in fission yeast but whether they are genetically separable is controversial. Here, we investigate the mitotic DSB repair properties of Ctp1 C-terminal domain (ctp1-CD) mutants that were reported to be specifically clipping deficient...
September 30, 2016: Nucleic Acids Research
Huiming Lu, Raghavendra A Shamanna, Guido Keijzers, Roopesh Anand, Lene Juel Rasmussen, Petr Cejka, Deborah L Croteau, Vilhelm A Bohr
The RecQ helicase RECQL4, mutated in Rothmund-Thomson syndrome, regulates genome stability, aging, and cancer. Here, we identify a crucial role for RECQL4 in DNA end resection, which is the initial and an essential step of homologous recombination (HR)-dependent DNA double-strand break repair (DSBR). Depletion of RECQL4 severely reduces HR-mediated repair and 5' end resection in vivo. RECQL4 physically interacts with MRE11-RAD50-NBS1 (MRN), which senses DSBs and initiates DNA end resection with CtIP. The MRE11 exonuclease regulates the retention of RECQL4 at laser-induced DSBs...
June 28, 2016: Cell Reports
Zdenek Kleibl, Vessela N Kristensen
The presence of breast cancer in any first-degree female relative in general nearly doubles the risk for a proband and the risk gradually increases with the number of affected relatives. Current advances in molecular oncology and oncogenetics may enable the identification of high-risk individuals with breast-cancer predisposition. The best-known forms of hereditary breast cancer (HBC) are caused by mutations in the high-penetrance genes BRCA1 and BRCA2. Other genes, including PTEN, TP53, STK11/LKB1, CDH1, PALB2, CHEK2, ATM, MRE11, RAD50, NBS1, BRIP1, FANCA, FANCC, FANCM, RAD51, RAD51B, RAD51C, RAD51D, and XRCC2 have been described as high- or moderate-penetrance breast cancer-susceptibility genes...
August 2016: Breast: Official Journal of the European Society of Mastology
Shunichi Takeda, Nguyen Ngoc Hoa, Hiroyuki Sasanuma
Homologous recombination (HR) initiates double-strand break (DSB) repair by digesting 5'-termini at DSBs, the biochemical reaction called DSB resection, during which DSBs are processed by nucleases to generate 3' single-strand DNA. Rad51 recombinase polymerizes along resected DNA, and the resulting Rad51-DNA complex undergoes homology search. Although DSB resection by the Mre11 nuclease plays a critical role in HR in Saccharomyces cerevisiae, it remains elusive whether DSB resection by Mre11 significantly contributes to HR-dependent DSB repair in mammalian cells...
August 2016: Journal of Radiation Research
Aleksey V Larionov, Maxim Y Sinitsky, Vladimir G Druzhinin, Valentin P Volobaev, Varvara I Minina, Maxim A Asanov, Alina V Meyer, Tatiana A Tolochko, Ekaterina E Kalyuzhnaya
PURPOSE: To study polymorphic variants of repair genes in people affected by long-term exposure to radon. The chromosome aberration frequency in peripheral blood lymphocytes was used as the biological marker of genotoxicity. MATERIALS AND METHODS: Genotyping of 12 single nucleotide polymorphisms in DNA repair genes (APE, XRCC1, OGG1, ADPRT, XpC, XpD, XpG, Lig4 and NBS1) was performed in children with long-term resident exposure to radon. Quantification of the aberrations was performed using light microscopy...
August 2016: International Journal of Radiation Biology
Shu Zhang, Corinne Pondarre, Gaelle Pennarun, Helene Labussiere-Wallet, Gabriella Vera, Benoit France, Marie Chansel, Isabelle Rouvet, Patrick Revy, Bernard Lopez, Jean Soulier, Pascale Bertrand, Isabelle Callebaut, Jean-Pierre de Villartay
Inherited bone marrow failure syndromes are human conditions in which one or several cell lineages of the hemopoietic system are affected. They are present at birth or may develop progressively. They are sometimes accompanied by other developmental anomalies. Three main molecular causes have been recognized to result in bone marrow failure syndromes: (1) defects in the Fanconi anemia (FA)/BRCA DNA repair pathway, (2) defects in telomere maintenance, and (3) abnormal ribosome biogenesis. We analyzed a patient with mild bone marrow failure and microcephaly who did not present with the typical FA phenotype...
May 30, 2016: Journal of Experimental Medicine
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