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Subbiahanadar Chelladurai K, Selvan Christyraj JD, Azhagesan A, Paulraj VD, Jothimani M, Yesudhason BV, Chellathurai Vasantha N, Ganesan M, Rajagopalan K, Venkatachalam S, Benedict J, John Samuel JK, Selvan Christyraj JRS. Exploring the effect of UV-C radiation on earthworm and understanding its genomic integrity in the context of H2AX expression. Sci Rep 2020; 10:21005. [PMID: 33273505 PMCID: PMC7713072 DOI: 10.1038/s41598-020-77719-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 11/17/2020] [Indexed: 01/28/2023] Open
Abstract
Maintaining genomic stability is inevitable for organism survival and it is challenged by mutagenic agents, which include ultraviolet (UV) radiation. Whenever DNA damage occurs, it is sensed by DNA-repairing proteins and thereby performing the DNA-repair mechanism. Specifically, in response to DNA damage, H2AX is a key protein involved in initiating the DNA-repair processes. In this present study, we investigate the effect of UV-C on earthworm, Perionyx excavatus and analyzed the DNA-damage response. Briefly, we expose the worms to different doses of UV-C and find that worms are highly sensitive to UV-C. As a primary response, earthworms produce coelomic fluid followed by autotomy. However, tissue inflammation followed by death is observed when we expose worm to increased doses of UV-C. In particular, UV-C promotes damages in skin layers and on the contrary, it mediates the chloragogen and epithelial outgrowth in intestinal tissues. Furthermore, UV-C promotes DNA damages followed by upregulation of H2AX on dose-dependent manner. Our finding confirms DNA damage caused by UV-C is directly proportional to the expression of H2AX. In short, we conclude that H2AX is present in the invertebrate earthworm, which plays an evolutionarily conserved role in DNA damage event as like that in higher animals.
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Affiliation(s)
- Karthikeyan Subbiahanadar Chelladurai
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Jackson Durairaj Selvan Christyraj
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Ananthaselvam Azhagesan
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India ,grid.412813.d0000 0001 0687 4946Present Address: Centre for Nanobiotechnology, Vellore Institute of Technology, Vellore, 632014 Tamilnadu India
| | - Vennila Devi Paulraj
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Muralidharan Jothimani
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India ,grid.411312.40000 0001 0363 9238Present Address: Department of Bioinformatics, Science Campus, Alagappa University, Karaikudi, 630004 Tamilnadu India
| | - Beryl Vedha Yesudhason
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Niranjan Chellathurai Vasantha
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Mijithra Ganesan
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Kamarajan Rajagopalan
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Saravanakumar Venkatachalam
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Johnson Benedict
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
| | - Jemima Kamalapriya John Samuel
- grid.252262.30000 0001 0613 6919Department of Biotechnology, Anna University of Technology, Tiruchirappalli, 620024 Tamilnadu India
| | - Johnson Retnaraj Samuel Selvan Christyraj
- grid.412427.60000 0004 1761 0622Regeneration and Stem Cell Biology Lab, Centre for Molecular and Nanomedical Sciences, International Research Centre, Sathyabama Institute of Science and Technology, Chennai, 600119 Tamilnadu India
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Calvente A, Santos JL, Rufas JS. Do Exogenous DNA Double-Strand Breaks Change Incomplete Synapsis and Chiasma Localization in the Grasshopper Stethophyma grossum? PLoS One 2016; 11:e0168499. [PMID: 28005992 PMCID: PMC5179137 DOI: 10.1371/journal.pone.0168499] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 11/30/2016] [Indexed: 01/15/2023] Open
Abstract
Meiotic recombination occurs as a programmed event that initiates by the formation of DNA double-strand breaks (DSBs) that give rise to the formation of crossovers that are observed as chiasmata. Chiasmata are essential for the accurate chromosome segregation and the generation of new combinations of parental alleles. Some treatments that provoke exogenous DSBs also lead to alterations in the recombination pattern of some species in which full homologous synapsis is achieved at pachytene. We have carried out a similar approach in males of the grasshopper Stethophyma grossum, whose homologues show incomplete synapsis and proximal chiasma localization. After irradiating males with γ rays we have studied the distribution of both the histone variant γ-H2AX and the recombinase RAD51. These proteins are cytological markers of DSBs at early prophase I. We have inferred synaptonemal complex (SC) formation via identification of SMC3 and RAD 21 cohesin subunits. Whereas thick and thin SMC3 filaments would correspond to synapsed and unsynapsed regions, the presence of RAD21 is only restricted to synapsed regions. Results show that irradiated spermatocytes maintain restricted synapsis between homologues. However, the frequency and distribution of chiasmata in metaphase I bivalents is slightly changed and quadrivalents were also observed. These results could be related to the singular nuclear polarization displayed by the spermatocytes of this species.
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Affiliation(s)
- Adela Calvente
- Departamento de Biología, Edificio de Biológicas, Universidad Autónoma de Madrid, Madrid, Spain
| | - Juan Luis Santos
- Departamento de Genética, Facultad de Biología, Universidad Complutense de Madrid, Madrid, Spain
| | - Julio S. Rufas
- Departamento de Biología, Edificio de Biológicas, Universidad Autónoma de Madrid, Madrid, Spain
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Chang KE, Wei BR, Madigan JP, Hall MD, Simpson RM, Zhuang Z, Gottesman MM. The protein phosphatase 2A inhibitor LB100 sensitizes ovarian carcinoma cells to cisplatin-mediated cytotoxicity. Mol Cancer Ther 2014; 14:90-100. [PMID: 25376608 DOI: 10.1158/1535-7163.mct-14-0496] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Despite early positive response to platinum-based chemotherapy, the majority of ovarian carcinomas develop resistance and progress to fatal disease. Protein phosphatase 2A (PP2A) is a ubiquitous phosphatase involved in the regulation of DNA-damage response (DDR) and cell-cycle checkpoint pathways. Recent studies have shown that LB100, a small-molecule inhibitor of PP2A, sensitizes cancer cells to radiation-mediated DNA damage. We hypothesized that LB100 could sensitize ovarian cancer cells to cisplatin treatment. We performed in vitro studies in SKOV-3, OVCAR-8, and PEO1, -4, and -6 ovarian cancer lines to assess cytotoxicity potentiation, cell-death mechanism(s), cell-cycle regulation, and DDR signaling. In vivo studies were conducted in an intraperitoneal metastatic mouse model using SKOV-3/f-Luc cells. LB100 sensitized ovarian carcinoma lines to cisplatin-mediated cell death. Sensitization via LB100 was mediated by abrogation of cell-cycle arrest induced by cisplatin. Loss of the cisplatin-induced checkpoint correlated with decreased Wee1 expression, increased cdc2 activation, and increased mitotic entry (p-histone H3). LB100 also induced constitutive hyperphosphorylation of DDR proteins (BRCA1, Chk2, and γH2AX), altered the chronology and persistence of JNK activation, and modulated the expression of 14-3-3 binding sites. In vivo, cisplatin sensitization via LB100 significantly enhanced tumor growth inhibition and prevented disease progression after treatment cessation. Our results suggest that LB100 sensitizes ovarian cancer cells to cisplatin in vitro and in vivo by modulation of the DDR pathway and cell-cycle checkpoint abrogation.
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Affiliation(s)
- Ki-Eun Chang
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - Bih-Rong Wei
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - James P Madigan
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - Matthew D Hall
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - R Mark Simpson
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland
| | - Zhengping Zhuang
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland
| | - Michael M Gottesman
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.
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Sun TM, Wang YC, Wang F, Du JZ, Mao CQ, Sun CY, Tang RZ, Liu Y, Zhu J, Zhu YH, Yang XZ, Wang J. Cancer stem cell therapy using doxorubicin conjugated to gold nanoparticles via hydrazone bonds. Biomaterials 2013; 35:836-45. [PMID: 24144908 DOI: 10.1016/j.biomaterials.2013.10.011] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 10/02/2013] [Indexed: 12/18/2022]
Abstract
Nanoparticle-mediated delivery of chemotherapies has demonstrated enhanced anti-cancer efficacy, mainly through the mechanisms of both passive and active targeting. Herein, we report other than these well-elucidated mechanisms, rationally designed nanoparticles can efficiently deliver drugs to cancer stem cells (CSCs), which in turn contributes significantly to the improved anti-cancer efficacy. We demonstrate that doxorubicin-tethered gold nanoparticles via a poly(ethylene glycol) spacer and an acid-labile hydrazone bond mediate potent doxorubicin delivery to breast CSCs, which reduces their mammosphere formation capacity and their cancer initiation activity, eliciting marked enhancement in tumor growth inhibition in murine models. The drug delivery mediated by the nanoparticles also markedly attenuates tumor growth during off-therapy stage by reducing breast CSCs in tumors, while the therapy with doxorubicin alone conversely evokes an enrichment of breast CSCs. Our findings suggest that with well-designed drug delivery system, the conventional chemotherapeutic agents are promising for cancer stem cell therapy.
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Affiliation(s)
- Tian-Meng Sun
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, PR China
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Nalbandian A, Yan BS, Pichugin A, Bronson RT, Kramnik I. Lung carcinogenesis induced by chronic tuberculosis infection: the experimental model and genetic control. Oncogene 2009; 28:1928-38. [DOI: 10.1038/onc.2009.32] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Vázquez-Martin C, Rouse J, Cohen PTW. Characterization of the role of a trimeric protein phosphatase complex in recovery from cisplatin-induced versus noncrosslinking DNA damage. FEBS J 2008; 275:4211-21. [PMID: 18647348 DOI: 10.1111/j.1742-4658.2008.06568.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Cisplatin (cis-diamminedichloroplatinum) and related chemotherapeutic DNA-crosslinking agents are widely used to treat human cancers. Saccharomyces cerevisiae with separate deletions of the genes encoding the trimeric protein serine/threonine phosphatase (Pph)3p-platinum sensitivity (Psy)4p-Psy2p complex, are more sensitive than the isogenic wild-type (WT) strain to cisplatin. We show here that cisplatin causes an enhanced intra-S-phase cell cycle delay in these three deletion mutants. The C-terminal tail of histone 2AX (H2AX) is hyperphosphorylated in the same mutants, and Pph3p is found to interact with phosphorylated H2AX (gammaH2AX). After cisplatin treatment is terminated, pph3Delta, psy4Delta and psy2Delta mutants are delayed as compared with the WT strain in the dephosphorylation of Rad53p. In contrast, only pph3Delta and psy2Delta cells are more sensitive than WT cells to methylmethanesulfonate, a noncrosslinking DNA-alkylating agent that is known to cause a Rad53p-dependent intra-S-phase cell cycle delay. Dephosphorylation of Rad53p and the recovery of chromosome replication are delayed in the same mutants, but not in psy4Delta cells. By comparison with their mammalian orthologues, the regulatory subunit Psy4p is likely to inhibit Pph3p catalytic activity. The presence of a weak but active Pph3p-Psy2p complex may allow psy4Delta cells to escape from the Rad53p-mediated cell cycle arrest. Overall, our data suggest that the trimeric Pph3p-Psy4p-Psy2p complex may dephosphorylate both gammaH2AX and Rad53p, the differences lying in the more stable interaction of the Pph3 phosphatase with gammaH2AX as opposed to a transient interaction with Rad53p.
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Affiliation(s)
- Cristina Vázquez-Martin
- Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, UK
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Mochizuki K, Novatchkova M, Loidl J. DNA double-strand breaks, but not crossovers, are required for the reorganization of meiotic nuclei in Tetrahymena. J Cell Sci 2008; 121:2148-58. [PMID: 18522989 PMCID: PMC3184542 DOI: 10.1242/jcs.031799] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
During meiosis, the micronuclei of the ciliated protist Tetrahymena thermophila elongate dramatically. Within these elongated nuclei, chromosomes are arranged in a bouquet-like fashion and homologous pairing and recombination takes place. We studied meiotic chromosome behavior in Tetrahymena in the absence of two genes, SPO11 and a homolog of HOP2 (HOP2A), which have conserved roles in the formation of meiotic DNA double-strand breaks (DSBs) and their repair, respectively. Single-knockout mutants for each gene display only a moderate reduction in chromosome pairing, but show a complete failure to form chiasmata and exhibit chromosome missegregation. The lack of SPO11 prevents the elongation of meiotic nuclei, but it is restored by the artificial induction of DSBs. In the hop2ADelta mutant, the transient appearance of gamma-H2A.X and Rad51p signals indicates the formation and efficient repair of DSBs; but this repair does not occur by interhomolog crossing over. In the absence of HOP2A, the nuclei are elongated, meaning that DSBs but not their conversion to crossovers are required for the development of this meiosis-specific morphology. In addition, by in silico homology searches, we compiled a list of likely Tetrahymena meiotic proteins as the basis for further studies of the unusual synaptonemal complex-less meiosis in this phylogenetically remote model organism.
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Affiliation(s)
- Kazufumi Mochizuki
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), A-1030 Vienna, Austria
| | - Maria Novatchkova
- Research Institute of Molecular Pathology (IMP), A-1030 Vienna, Austria
| | - Josef Loidl
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Dr Bohr Gasse 1, A-1030 Vienna, Austria
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Downs JA, Nussenzweig MC, Nussenzweig A. Chromatin dynamics and the preservation of genetic information. Nature 2007; 447:951-8. [PMID: 17581578 DOI: 10.1038/nature05980] [Citation(s) in RCA: 229] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The integrity of the genome is frequently challenged by double-strand breaks in the DNA. Defects in the cellular response to double-strand breaks are a major cause of cancer and other age-related pathologies; therefore, much effort has been directed at understanding the enzymatic mechanisms involved in recognizing, signalling and repairing double-strand breaks. Recent work indicates that chromatin - the fibres into which DNA is packaged with a proteinaceous structural polymer - has an important role in initiating, propagating and terminating this cellular response to DNA damage.
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Affiliation(s)
- Jessica A Downs
- MRC Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK.
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Li W, Dou SX, Xie P, Wang PY. Brownian dynamics simulation of the effect of histone modification on nucleosome structure. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:051915. [PMID: 17677106 DOI: 10.1103/physreve.75.051915] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Revised: 03/21/2007] [Indexed: 05/16/2023]
Abstract
Using Brownian dynamics we simulate the effect of histone modification, such as phosphorylation, acetylation, and methylation, on nucleosome structure by varying the interaction force between DNA and the histone octamer. The simulation shows that the structural stability of nucleosome is very sensitive to the interaction force, and the DNA unwrapping from the modified histone octamer usually occurs turn by turn. Furthermore, the effects of temperature and DNA break as well as the competition between modified and normal histone octamers are investigated, with the simulation results being in agreement with the experimental observation that phosphorylated nucleosomes near DNA breaks are more easily depleted. Though the simulation study may only give a coarse grained view of the DNA unwrapping process for the modified histone octamer, it may provide insight into the mechanism of DNA repair.
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Affiliation(s)
- Wei Li
- Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
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Bewersdorf J, Bennett BT, Knight KL. H2AX chromatin structures and their response to DNA damage revealed by 4Pi microscopy. Proc Natl Acad Sci U S A 2006; 103:18137-42. [PMID: 17110439 PMCID: PMC1636994 DOI: 10.1073/pnas.0608709103] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
DNA double-strand breaks (DSBs) caused by cellular exposure to genotoxic agents or produced by inherent metabolic processes initiate a rapid and highly coordinated series of molecular events resulting in DNA damage signaling and repair. Phosphorylation of histone H2AX to form gamma-H2AX is one of the earliest of these events and is important for coordination of signaling and repair activities. An intriguing aspect of H2AX phosphorylation is that gamma-H2AX spreads a limited distance up to 1-2 Mbp from the site of a DNA break in mammalian cells. However, neither the distribution of H2AX throughout the genome nor the mechanism that defines the boundary of gamma-H2AX spreading have yet been described. Here, we report the identification of previously undescribed H2AX chromatin structures by successfully applying 4Pi microscopy to visualize endogenous nuclear proteins. Our observations suggest that H2AX is not distributed randomly throughout bulk chromatin, rather it exists in distinct clusters that themselves are uniformly distributed within the nuclear volume. These data support a model in which the size and distribution of H2AX clusters define the boundaries of gamma-H2AX spreading and also may provide a platform for the immediate and robust response observed after DNA damage.
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Affiliation(s)
- Jörg Bewersdorf
- *Institute for Molecular Biophysics, The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609
| | - Brian T. Bennett
- Department of Biochemistry and Molecular Pharmacology, Aaron Lazare Medical Research Building, 364 Plantation Street, University of Massachusetts Medical School, Worcester, MA 01655; and
- Leica Microsystems Inc., 410 Eagleview Boulevard, Exton, PA 19341
| | - Kendall L. Knight
- Department of Biochemistry and Molecular Pharmacology, Aaron Lazare Medical Research Building, 364 Plantation Street, University of Massachusetts Medical School, Worcester, MA 01655; and
- To whom correspondence should be addressed. E-mail:
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Game JC, Williamson MS, Spicakova T, Brown JM. The RAD6/BRE1 histone modification pathway in Saccharomyces confers radiation resistance through a RAD51-dependent process that is independent of RAD18. Genetics 2006; 173:1951-68. [PMID: 16783014 PMCID: PMC1569736 DOI: 10.1534/genetics.106.057794] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We examine ionizing radiation (IR) sensitivity and epistasis relationships of several Saccharomyces mutants affecting post-translational modifications of histones H2B and H3. Mutants bre1Delta, lge1Delta, and rtf1Delta, defective in histone H2B lysine 123 ubiquitination, show IR sensitivity equivalent to that of the dot1Delta mutant that we reported on earlier, consistent with published findings that Dot1p requires H2B K123 ubiquitination to fully methylate histone H3 K79. This implicates progressive K79 methylation rather than mono-methylation in IR resistance. The set2Delta mutant, defective in H3 K36 methylation, shows mild IR sensitivity whereas mutants that abolish H3 K4 methylation resemble wild type. The dot1Delta, bre1Delta, and lge1Delta mutants show epistasis for IR sensitivity. The paf1Delta mutant, also reportedly defective in H2B K123 ubiquitination, confers no sensitivity. The rad6Delta, rad51null, rad50Delta, and rad9Delta mutations are epistatic to bre1Delta and dot1Delta, but rad18Delta and rad5Delta show additivity with bre1Delta, dot1Delta, and each other. The bre1Delta rad18Delta double mutant resembles rad6Delta in sensitivity; thus the role of Rad6p in ubiquitinating H2B accounts for its extra sensitivity compared to rad18Delta. We conclude that IR resistance conferred by BRE1 and DOT1 is mediated through homologous recombinational repair, not postreplication repair, and confirm findings of a G1 checkpoint role for the RAD6/BRE1/DOT1 pathway.
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Affiliation(s)
- John C Game
- Life Sciences Division, Lawrence Berkeley National Laboratory, CA 94720, USA.
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Kruhlak MJ, Celeste A, Dellaire G, Fernandez-Capetillo O, Müller WG, McNally JG, Bazett-Jones DP, Nussenzweig A. Changes in chromatin structure and mobility in living cells at sites of DNA double-strand breaks. J Cell Biol 2006; 172:823-34. [PMID: 16520385 PMCID: PMC2063727 DOI: 10.1083/jcb.200510015] [Citation(s) in RCA: 393] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Accepted: 02/09/2006] [Indexed: 01/14/2023] Open
Abstract
The repair of DNA double-strand breaks (DSBs) is facilitated by the phosphorylation of H2AX, which organizes DNA damage signaling and chromatin remodeling complexes in the vicinity of the lesion. The disruption of DNA integrity induces an alteration of chromatin architecture that has been proposed to activate the DNA damage transducing kinase ataxia telangiectasia mutated. However, little is known about the physical properties of damaged chromatin. In this study, we use a photoactivatable version of GFP-tagged histone H2B to examine the mobility and structure of chromatin containing DSBs in living cells. We find that chromatin containing DSBs exhibits limited mobility but undergoes an energy-dependent local expansion immediately after DNA damage. The localized expansion observed in real time corresponds to a 30-40% reduction in the density of chromatin fibers in the vicinity of DSBs, as measured by energy-filtering transmission electron microscopy. The observed opening of chromatin occurs independently of H2AX and ATM. We propose that localized adenosine triphosphate-dependent decondensation of chromatin at DSBs establishes an accessible subnuclear environment that facilitates DNA damage signaling and repair.
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Affiliation(s)
- Michael J Kruhlak
- Experimental Immunology Branch and 2Laboratory for Receptor Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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