WorldWideScience

Sample records for chromatids

  1. Sister chromatid cohesion and recombination in meiosis

    NARCIS (Netherlands)

    Heemst, van D.; Heyting, C.

    2000-01-01

    Sister chromatids are associated from their formation until their disjunction. Cohesion between sister chromatids is provided by protein complexes, of which some components are conserved across the kingdoms and between the mitotic and meiotic cell cycles. Sister chromatid cohesion is intimately link

  2. Mechanisms of sister chromatid recombination

    International Nuclear Information System (INIS)

    Studies using T948 as a model system have been carried out aimed at elucidating the mechanism of sister chromatid recombination (SCR). Characterization of U.V. light- and x-ray-induced SCR, the relationiship between SCR induction and DNA repair using rad mutations, and the relationship between SCR induction and the time of cell division using cdc mutations are presented. It has been supposed that SCR is induced at the phase of S-G2 following DNA replication, that postreplication break of DNA strands is strongly involved in the induction of SCR, and that induction type of SCR, i.e., conversion type or recombination type, is dependent upon the type of molecular damage of DNA. (Namekawa, K.)

  3. Chromatid interchanges at intrachromosomal telomeric DNA sequences

    International Nuclear Information System (INIS)

    Chinese hamster Don cells were exposed to X-rays, mitomycin C and teniposide (VM-26) to induce chromatid exchanges (quadriradials and triradials). After fluorescence in situ hybridization (FISH) of telomere sequences it was found that interstitial telomere-like DNA sequence arrays presented around five times more breakage-rearrangements than the genome overall. This high recombinogenic capacity was independent of the clastogen, suggesting that this susceptibility is not related to the initial mechanisms of DNA damage. (author)

  4. A matter of choice: the establishment of sister chromatid cohesion

    OpenAIRE

    Uhlmann, Frank

    2009-01-01

    Sister chromatid cohesion is the basis for the recognition of chromosomal DNA replication products for their bipolar segregation in mitosis. Fundamental to sister chromatid cohesion is the ring-shaped cohesin complex, which is loaded onto chromosomes long before the initiation of DNA replication and is thought to hold replicated sister chromatids together by topological embrace. What happens to cohesin when the replication fork approaches, and how cohesin recognizes newly synthesized sister c...

  5. Mechanics of Sister Chromatids studied with a Polymer Model

    Directory of Open Access Journals (Sweden)

    Yang eZhang

    2013-10-01

    Full Text Available Sister chromatid cohesion denotes the phenomenon that sister chromatids are initially attached to each other in mitosis to guarantee the error-free distribution into the daughter cells. Cohesion is mediated by binding proteins and only resolved after mitotic chromosome condensation is completed. However, the amount of attachement points required to maintain sister chromatid cohesion while still allowing proper chromosome condensation is not known yet. Additionally the impact of cohesion on the mechanical properties of chromosomes also poses an interesting problem. In this work we study the conformational and mechanical properties of sister chromatids by means of computer simulations. We model both protein-mediated cohesion between sister chromatids and chromosome condensation with a dynamic binding mechanisms. We show in a phase diagram that only specific link concentrations lead to connected and fully condensed chromatids that do not intermingle with each other nor separate due to entropic forces. Furthermore we show that dynamic bonding between chromatids decrease the Young's modulus compared to non-bonded chromatids.

  6. Meiotic sister chromatid cohesion and recombination in two filamentous fungi

    NARCIS (Netherlands)

    Heemst, van D.

    2000-01-01

    Homologous recombination and sister chromatid cohesion play important roles in the maintenance of genome integrity and the fidelity of chromosome segregation in mitosis and meiosis. Within the living cell, the integrity of the DNA is threatened by various factors that cause DNA-lesions, of which DNA

  7. Is chromatin remodeling required to build sister-chromatid cohesion?

    NARCIS (Netherlands)

    Riedel, Christian G; Gregan, Juraj; Gruber, Stephan; Nasmyth, Kim

    2004-01-01

    Chromosome segregation during mitosis and meiosis depends on the linkage of sister DNA molecules after replication. These links, known as sister-chromatid cohesion, are provided by a multi-subunit complex called cohesin. Recent papers suggest that chromatin-remodeling complexes also have a role in t

  8. Identification of protein complexes required for efficient sister chromatid cohesion

    NARCIS (Netherlands)

    Mayer, Melanie L; Pot, Isabelle; Chang, Michael; Xu, Hong; Aneliunas, Victoria; Kwok, Teresa; Newitt, Rick; Aebersold, Ruedi; Boone, Charles; Brown, Grant W; Hieter, Philip

    2004-01-01

    Ctf8p is a component of Ctf18-RFC, an alternative replication factor C-like complex required for efficient sister chromatid cohesion in Saccharomyces cerevisiae. We performed synthetic genetic array (SGA) analysis with a ctf8 deletion strain as a primary screen to identify other nonessential genes r

  9. Meiotic sister chromatid cohesion and recombination in two filamentous fungi

    OpenAIRE

    Heemst, van, D.

    2000-01-01

    Homologous recombination and sister chromatid cohesion play important roles in the maintenance of genome integrity and the fidelity of chromosome segregation in mitosis and meiosis. Within the living cell, the integrity of the DNA is threatened by various factors that cause DNA-lesions, of which DNA double-strand breaks (DSBs) are considered particularly deleterious. The causative agents can be of endogenous origin, such as metabolically produced free radicals, and of exogenous origin, such a...

  10. Investigating the Interplay between Sister Chromatid Cohesion and Homolog Pairing in Drosophila Nuclei.

    Science.gov (United States)

    Senaratne, T Niroshini; Joyce, Eric F; Nguyen, Son C; Wu, C-Ting

    2016-08-01

    Following DNA replication, sister chromatids must stay connected for the remainder of the cell cycle in order to ensure accurate segregation in the subsequent cell division. This important function involves an evolutionarily conserved protein complex known as cohesin; any loss of cohesin causes premature sister chromatid separation in mitosis. Here, we examined the role of cohesin in sister chromatid cohesion prior to mitosis, using fluorescence in situ hybridization (FISH) to assay the alignment of sister chromatids in interphase Drosophila cells. Surprisingly, we found that sister chromatid cohesion can be maintained in G2 with little to no cohesin. This capacity to maintain cohesion is widespread in Drosophila, unlike in other systems where a reduced dependence on cohesin for sister chromatid segregation has been observed only at specific chromosomal regions, such as the rDNA locus in budding yeast. Additionally, we show that condensin II antagonizes the alignment of sister chromatids in interphase, supporting a model wherein cohesin and condensin II oppose each other's functions in the alignment of sister chromatids. Finally, because the maternal and paternal homologs are paired in the somatic cells of Drosophila, and because condensin II has been shown to antagonize this pairing, we consider the possibility that condensin II-regulated mechanisms for aligning homologous chromosomes may also contribute to sister chromatid cohesion. PMID:27541002

  11. Cohesin SMC1 beta is required for meiotic chromosome dynamics, sister chromatid cohesion and DNA recombination

    NARCIS (Netherlands)

    Revenkova, E.; Eijpe, M.; Heyting, C.; Hodges, C.A.; Hunt, P.A.; Liebe, B.; Scherthan, H.; Jessberger, R.

    2004-01-01

    Sister chromatid cohesion ensures the faithful segregation of chromosomes in mitosis and in both meiotic divisions1, 2, 3, 4. Meiosis-specific components of the cohesin complex, including the recently described SMC1 isoform SMC15, were suggested to be required for meiotic sister chromatid cohesion a

  12. DNA-mediated transfer of a human DNA repair gene that controls sister chromatid exchange.

    OpenAIRE

    Thompson, L H; Brookman, K W; Minkler, J L; Fuscoe, J C; Henning, K A; Carrano, A V

    1985-01-01

    The Chinese hamster cell line mutant EM9, which has a reduced ability to repair DNA strand breaks, is noted for its highly elevated frequency of sister chromatid exchange, a property shared with cells from individuals with Bloom's syndrome. The defect in EM9 cells was corrected by fusion hybridization with normal human fibroblasts and by transfection with DNA from hybrid cells. The transformants showed normalization of sister chromatid exchange frequency but incomplete correction of the repai...

  13. Solution Radioactivated by Hadron Radiation Can Increase Sister Chromatid Exchanges.

    Science.gov (United States)

    Maeda, Junko; Yurkon, Charles R; Fujii, Yoshihiro; Fujisawa, Hiroshi; Kato, Sayaka; Brents, Colleen A; Uesaka, Mitsuru; Fujimori, Akira; Kitamura, Hisashi; Kato, Takamitsu A

    2015-01-01

    When energetic particles irradiate matter, it becomes activated by nuclear reactions. Radioactivation induced cellular effects are not clearly understood, but it could be a part of bystander effects. This investigation is aimed at understanding the biological effects from radioactivation in solution induced by hadron radiation. Water or phosphate buffered saline was activated by being exposed to hadron radiation including protons, carbon- and iron-ions. 1 mL of radioactivated solution was transferred to flasks with Chinese hamster ovary (CHO) cells cultured in 5 mL of complete media. The induction of sister chromatid exchanges (SCE) was used to observe any increase in DNA damage responses. The energy spectrum and the half-lives of the radioactivation were analyzed by NaI scintillation detector in order to identify generated radionuclides. In the radioactivated solution, 511 keV gamma-rays were observed, and their half-lives were approximately 2 min, 10 min, and 20 min. They respectively correspond to the beta+ decay of 15O, 13N, and 11C. The SCE frequencies in CHO cells increased depending on the amount of radioactivation in the solution. These were suppressed with a 2-hour delayed solution transfer or pretreatment with dimethyl sulfoxide (DMSO). Our results suggest that the SCE induction by radioactivated solution was mediated by free radicals produced by the annihilated gamma-rays. Since the SCE induction and DMSO modulation are also reported in radiation-induced bystander effects, our results imply that radioactivation of the solution may have some contribution to the bystander effects from hadron radiation. Further investigations are required to assess if radioactivation effects would attribute an additional level of cancer risk of the hadron radiation therapy itself. PMID:26657140

  14. Cell biology of cancer: BRCA1 and sister chromatid pairing reactions?

    Science.gov (United States)

    Skibbens, Robert V

    2008-02-15

    A significant portion of familial breast/ovarian cancer patients harbors a mutation in Breast Cancer Associated gene 1 (BRCA1). Cells deficient for BRCA1 exhibit chromosome aberrations such as whole chromosome duplications, translocations, inter-sister gaps and gene mis-regulation. Here, new evidence is reviewed that defects in sister chromatid cohesion may contribute directly to cancer cell phenotypes-especially those of BRCA1 mutant cells. Linking cohesion to BRCA1-dependent tumorigenesis are reports that BRCA1-associated components (DNA helicase, RFC, PCNA and genome surveillance factors) are required for efficient sister chromatid cohesion. Other cohesion factors (WAPL, EFO2/ESCO2 and hSecurin) are tightly correlated with various cell-type specific carcinogenesis, in support of a generalized model for cohesion in cancer. Recent findings further reveal that a reciprocal relationship exists in that DNA damage induces new Ctf7/Eco1-dependent sister chromatid pairing reactions that, in turn, are required for efficient DNA repair. Future research into sister chromatid pairing mechanisms are likely to provide critical new insights into the underlying causes of cancer.

  15. INDUCTION, ACCUMULATION, AND PERSISTENCE OF SISTER CHROMATID EXCHANGES IN WOMEN WITH BREAST CANCER RECEIVING CYCLOPHOSPHAMIDE, ANDRIAMYCIN, AND 5-FLUOROACIL CHEMOTHERAPY

    Science.gov (United States)

    The induction, stimulation, and persistence of sister chromatid exchanges (SCE's) and high SCE frequency cells (HFC's) was measured in peripheral lymphocytes of women with breast cancer before chemotherapy and on multiple occasions during and after therapy. Chemotherapy consisted...

  16. Shugoshin1 May Play Important Roles in Separation of Homologous Chromosomes and Sister Chromatids during Mouse Oocyte Meiosis

    OpenAIRE

    Shen Yin; Jun-Shu Ai; Li-Hong Shi; Liang Wei; Ju Yuan; Ying-Chun Ouyang; Yi Hou; Da-Yuan Chen; Heide Schatten; Qing-Yuan Sun

    2008-01-01

    BACKGROUND: Homologous chromosomes separate in meiosis I and sister chromatids separate in meiosis II, generating haploid gametes. To address the question why sister chromatids do not separate in meiosis I, we explored the roles of Shogoshin1 (Sgo1) in chromosome separation during oocyte meiosis. METHODOLOGY/PRINCIPAL FINDINGS: Sgo1 function was evaluated by exogenous overexpression to enhance its roles and RNAi to suppress its roles during two meioses of mouse oocytes. Immunocytochemistry an...

  17. A study of sister chromatid exchange in patients with dental amalgam restorations

    OpenAIRE

    E Lakshmi Priya; K Ranganathan; Uma Devi K Rao; Elizabeth Joshua; Deepu George Mathew; Kavitha Wilson

    2014-01-01

    Study Background: Dental amalgam is still widely used as a restorative material in developing countries due to its low cost and ease of manipulation. The health risks associated with the components of this restorative material has always been a matter of concern. Our study was designed to address this question regarding dental amalgam. Objective: To study sister chromatid exchange (SCE) as an indicator of systemic genotoxicity, due to the exposure from the components of amalgam restoratio...

  18. Sister Chromatid Exchange Frequency in Lymphocytes Cultured from Cotton Gin Workers

    OpenAIRE

    ATMACA, Münevver; BAĞCI, Hüseyin; AÇIKBAŞ, İbrahim; GÜMÜŞ, Dilihan; DÜZCAN, Füsun

    2004-01-01

    Genetic biomonitoring of human populations exposed to potential mutagens/carcinogens can be performed using different genetic markers. Sister chromatid exchange (SCE) is one of the most extensively used markers of the early biological effects of DNA damaging agents. In order to assess the genotoxicity associated with exposure to cotton dust, we determined SCE frequency in peripheral blood lymphocytes cultured from 20 cotton gin workers and 20 controls. Student’s-t test indicated an ...

  19. "Sister Chromatid Exchanges and Micronuclei in Lymphocyte of Nurses Handling Antineoplastic Drugs"

    OpenAIRE

    Ansari-Lari, M; M.Saadat; Shahryari, M.; DD Farhud

    2001-01-01

    Individuals handling antineoplastic drugs or their wastes may absorb these potent genotoxic agents. The effects of handling antineoplastic drugs were examined in a group of 24 nurses working in the hematology and oncology departments of two different university hospitals in Shiraz (Iran) and in a group of 18 unexposed nurses as control group. The cytogenetic repercussions of exposure were assessed by examining sister chromatid exchanges (SCEs) and micronuclei (Mn) in circulating lymphocytes. ...

  20. Frequency of sister chromatid exchange and chromosomal aberrations in asbestos cement workers.

    OpenAIRE

    Fatma, N; Jain, A. K.; Rahman, Q

    1991-01-01

    Exposure to asbestos minerals has been associated with a wide variety of adverse health effects including lung cancer, pleural mesothelioma, and cancer of other organs. It was shown previously that asbestos samples collected from a local asbestos factory enhanced sister chromatid exchanges (SCEs) and chromosomal aberrations in vitro using human lymphocytes. In the present study, 22 workers from the same factory and 12 controls were further investigated. Controls were matched for age, sex, and...

  1. Sister chromatid exchange analysis in lymphocytes of workers exposed to hexavalent chromium.

    OpenAIRE

    Nagaya, T.; Ishikawa, N.; Hata, H.

    1989-01-01

    To investigate the usefulness of sister chromatid exchange (SCE) analysis in lymphocytes as an indicator for mutagenic effects after in vivo exposure to hexavalent chromium (Cr), SCE frequency was analysed in lymphocytes of 44 Cr platers occupationally exposed to hexavalent Cr and 47 controls. Although urinary Cr analysis confirmed that the Cr platers were exposed to Cr, no effects of the exposure on SCE frequency were found. Smokers, both Cr platers and controls, had a significantly higher S...

  2. An increase in telomere sister chromatid exchange in murine embryonic stem cells possessing critically shortened telomeres

    OpenAIRE

    Wang, Yisong; Erdmann, Natalie; Giannone, Richard J.; Wu, Jun; Gomez, Marla; Liu, Yie

    2005-01-01

    Telomerase deficiency leads to a progressive loss of telomeric DNA that eventually triggers cell apoptosis in human primary cells during prolonged growth in culture. Rare survivors can maintain telomere length through either activation of telomerase or recombination-based telomere lengthening, and thus proliferate indefinitely. We have explored the possibility that telomeres may be maintained through telomere sister chromatid exchange (T-SCE) in murine telomere reverse transcriptase-deficient...

  3. "Sister Chromatid Exchanges and Micronuclei in Lymphocyte of Nurses Handling Antineoplastic Drugs"

    Directory of Open Access Journals (Sweden)

    M Ansari-Lari

    2001-07-01

    Full Text Available Individuals handling antineoplastic drugs or their wastes may absorb these potent genotoxic agents. The effects of handling antineoplastic drugs were examined in a group of 24 nurses working in the hematology and oncology departments of two different university hospitals in Shiraz (Iran and in a group of 18 unexposed nurses as control group. The cytogenetic repercussions of exposure were assessed by examining sister chromatid exchanges (SCEs and micronuclei (Mn in circulating lymphocytes. A significant increased frequencies of SCE and Mn is observed in circulating lymphocytes. A significant increased frequencies of SCE and Mn is observed in nurses in daily contact with antineoplastic drugs as compared to control group.

  4. Defective sister chromatid cohesion is synthetically lethal with impaired APC/C function

    OpenAIRE

    De Lange, Job; Faramarz, Atiq; Oostra, Anneke B.; Menezes, Renee X.; van der Meulen, Ida H.; Rooimans, Martin A.; Rockx, Davy A.; Brakenhoff, Ruud H.; van Beusechem, Victor W; King, Randall W; Winter, Johan P. de; Wolthuis, Rob M. F.

    2015-01-01

    Warsaw breakage syndrome (WABS) is caused by defective DDX11, a DNA helicase that is essential for chromatid cohesion. Here, a paired genome-wide siRNA screen in patient-derived cell lines reveals that WABS cells do not tolerate partial depletion of individual APC/C subunits or the spindle checkpoint inhibitor p31comet. A combination of reduced cohesion and impaired APC/C function also leads to fatal mitotic arrest in diploid RPE1 cells. Moreover, WABS cell lines, and several cancer cell line...

  5. Chromosome aberrations and sister chromatid exchanges in Swedish paint industry workers

    Energy Technology Data Exchange (ETDEWEB)

    Haglund, U.; Lundberg, I.; Zech, L.

    1980-12-01

    Workers in the Swedish paint industry exposed to a mixture of organic solvents, mainly containing xylene or toluene, were investigated for genotoxic effects. No difference in the frequency of sister chromatid exchanges (SCE), 0.192 and 0.193 per chromosome, respectively, was noted in the peripheral lymphocytes of the exposed group of 17 workers and their matched reference group. No correlation was found between xylene or toluene exposure and SCE frequency nor between total solvent exposure and SCE frequency. The frequency of chromosome aberrations was also investigated for the five most exposed workers and their matched referents, and no difference was found. There was no correlation between SCE and chromosome breaks.

  6. UBL5 is essential for pre-mRNA splicing and sister chromatid cohesion in human cells

    DEFF Research Database (Denmark)

    Oka, Yasuyoshi; Varmark, Hanne; Vitting-Seerup, Kristoffer;

    2014-01-01

    UBL5 is an atypical ubiquitin-like protein, whose function in metazoans remains largely unexplored. We show that UBL5 is required for sister chromatid cohesion maintenance in human cells. UBL5 primarily associates with spliceosomal proteins, and UBL5 depletion decreases pre-mRNA splicing efficiency......, leading to globally enhanced intron retention. Defective sister chromatid cohesion is a general consequence of dysfunctional pre-mRNA splicing, resulting from the selective downregulation of the cohesion protection factor Sororin. As the UBL5 yeast orthologue, Hub1, also promotes spliceosome functions...

  7. Chromatids segregate without centrosomes during Caenorhabditis elegans mitosis in a Ran- and CLASP-dependent manner.

    Science.gov (United States)

    Nahaboo, Wallis; Zouak, Melissa; Askjaer, Peter; Delattre, Marie

    2015-06-01

    During mitosis, chromosomes are connected to a microtubule-based spindle. Current models propose that displacement of the spindle poles and/or the activity of kinetochore microtubules generate mechanical forces that segregate sister chromatids. Using laser destruction of the centrosomes during Caenorhabditis elegans mitosis, we show that neither of these mechanisms is necessary to achieve proper chromatid segregation. Our results strongly suggest that an outward force generated by the spindle midzone, independently of centrosomes, is sufficient to segregate chromosomes in mitotic cells. Using mutant and RNAi analysis, we show that the microtubule-bundling protein SPD-1/MAP-65 and BMK-1/kinesin-5 act as a brake opposing the force generated by the spindle midzone. Conversely, we identify a novel role for two microtubule-growth and nucleation agents, Ran and CLASP, in the establishment of the centrosome-independent force during anaphase. Their involvement raises the interesting possibility that microtubule polymerization of midzone microtubules is continuously required to sustain chromosome segregation during mitosis.

  8. KINETICS OF IN VIVO SISTER CHROMATID EXCHANGE INDUCTION IN MOUSE BONE MARROW CELLS BY ALKYLATING AGENTS: CYCLOPHOSPHAMIDE

    Science.gov (United States)

    Administration of cyclophosphamide (5, 10, 20 and 25 mg/kg body weight) to male CD-1 mice 2 hours after subcutaneous implantation of a 5-bromo-2'-deoxyuridine (BrdU) pellet (55 mg) resulted in a dose-dependent increase in sister chromatid exchanges (SCE) in bone marrow cells. Tre...

  9. PICH promotes sister chromatid disjunction and co-operates with topoisomerase II in mitosis.

    Science.gov (United States)

    Nielsen, Christian F; Huttner, Diana; Bizard, Anna H; Hirano, Seiki; Li, Tian-Neng; Palmai-Pallag, Timea; Bjerregaard, Victoria A; Liu, Ying; Nigg, Erich A; Wang, Lily Hui-Ching; Hickson, Ian D

    2015-01-01

    PICH is a SNF2 family DNA translocase that binds to ultra-fine DNA bridges (UFBs) in mitosis. Numerous roles for PICH have been proposed from protein depletion experiments, but a consensus has failed to emerge. Here, we report that deletion of PICH in avian cells causes chromosome structural abnormalities, and hypersensitivity to an inhibitor of Topoisomerase II (Topo II), ICRF-193. ICRF-193-treated PICH(-/-) cells undergo sister chromatid non-disjunction in anaphase, and frequently abort cytokinesis. PICH co-localizes with Topo IIα on UFBs and at the ribosomal DNA locus, and the timely resolution of both structures depends on the ATPase activity of PICH. Purified PICH protein strongly stimulates the catalytic activity of Topo II in vitro. Consistent with this, a human PICH(-/-) cell line exhibits chromosome instability and chromosome condensation and decatenation defects similar to those of ICRF-193-treated cells. We propose that PICH and Topo II cooperate to prevent chromosome missegregation events in mitosis.

  10. Sister chromatid exchange in human populations: the effect of smoking, drug treatment, and occupational exposure

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, B.; Bredberg, A.; McKenzie, W.; Sten, M.

    1982-01-01

    Increased rate of sister chromatid exchange (SCE) in peripheral lymphocytes has been observed in smokers as compared to nonsmokers and in patients receiving certain cytostatic drugs. The increased SCE frequency in smokers was shown to depend on the number of cigarettes smoked per day, as well as on the duration of smoking. DNA cross-links caused by photochemotherapy against psoriasis, 8-methoxypsoralen plus UVA irradiation (PUVA), as well as by the anti-cancer chemotherapeutic agent CCNU, were shown to be more effective at inducing SCE's than other types of DNA damage caused by these treatments. These observations suggest that SCE analysis may be used as an indicator of genotoxic exposure in vivo, provided that the various types of DNA damage caused by genotoxic agents and the dose, as well as the time of exposure in relation to the time of sampling, are considered.

  11. An increase in telomere sister chromatid exchange in murine embryonic stem cells possessing critically shortened telomeres

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yisong [ORNL; Giannone, Richard J [ORNL; Wu, Jun [ORNL; Gomez, Marla V [ORNL; Liu, Yie [ORNL

    2005-01-01

    Telomerase deficiency leads to a progressive loss of telomeric DNA that eventually triggers cell apoptosis in human primary cells during prolonged growth in culture. Rare survivors can maintain telomere length through either activation of telomerase or recombination-based telomere lengthening, and thus proliferate indefinitely. We have explored the possibility that telomeres may be maintained through telomere sister chromatid exchange (T-SCE) in murine telomere reverse transcriptase-deficient (mTert -/-) splenocytes and ES cells. Because telomerase deficiency leads to gradual loss of telomeric DNA in mTert -/- splenocytes and ES cells and eventually to chromosomes with telomere signal-free ends (SFEs), we examined these cell types for evidence of sister chromatid exchange at telomeres, and observed an increase in T-SCEs only in a subset of mTert -/- splenocytes or ES cells that possessed multiple SFEs. Furthermore, T-SCEs were more often detected in ES cells than in splenocytes that harbored a similar frequency of SFEs. In mTert heterozygous (mTert +/-) ES cells or splenocytes, which are known to exhibit a decrease in average telomere length but no SFEs, no increase in T-SCE was observed. In addition to T-SCE, other genomic rearrangements (i.e., SCE) were also significantly increased in mTert -/- ES cells possessing critically short telomeres, but not in splenocytes. Our results suggest that animals and cell culture differ in their ability to carry out genomic rearrangements as a means of maintaining telomere integrity when telomeres become critically shortened.

  12. Variation of the symmetrical/asymmetrical ratio in chromatid interchanges during the various phases of the cell cycle of human lymphocytes 'in vitro'

    International Nuclear Information System (INIS)

    Experiments have been performed to verify whether in a human euploid cell system, such as lymphocyte cultures in vitro, there is a differential pattern of induction of chromatid exchanges in the various phases of the cycle. (Auth.)

  13. Premature Sister Chromatid Separation Is Poorly Detected by the Spindle Assembly Checkpoint as a Result of System-Level Feedback

    Directory of Open Access Journals (Sweden)

    Mihailo Mirkovic

    2015-10-01

    Full Text Available Sister chromatid cohesion, mediated by the cohesin complex, is essential for faithful mitosis. Nevertheless, evidence suggests that the surveillance mechanism that governs mitotic fidelity, the spindle assembly checkpoint (SAC, is not robust enough to halt cell division when cohesion loss occurs prematurely. The mechanism behind this poor response is not properly understood. Using developing Drosophila brains, we show that full sister chromatid separation elicits a weak checkpoint response resulting in abnormal mitotic exit after a short delay. Quantitative live-cell imaging approaches combined with mathematical modeling indicate that weak SAC activation upon cohesion loss is caused by weak signal generation. This is further attenuated by several feedback loops in the mitotic signaling network. We propose that multiple feedback loops involving cyclin-dependent kinase 1 (Cdk1 gradually impair error-correction efficiency and accelerate mitotic exit upon premature loss of cohesion. Our findings explain how cohesion defects may escape SAC surveillance.

  14. Cell killing and chromatid damage in primary human bronchial epithelial cells irradiated with accelerated 56Fe ions

    Science.gov (United States)

    Suzuki, M.; Piao, C.; Hall, E. J.; Hei, T. K.

    2001-01-01

    We examined cell killing and chromatid damage in primary human bronchial epithelial cells irradiated with high-energy 56Fe ions. Cells were irradiated with graded doses of 56Fe ions (1 GeV/nucleon) accelerated with the Alternating Gradient Synchrotron at Brookhaven National Laboratory. The survival curves for cells plated 1 h after irradiation (immediate plating) showed little or no shoulder. However, the survival curves for cells plated 24 h after irradiation (delayed plating) had a small initial shoulder. The RBE for 56Fe ions compared to 137Cs gamma rays was 1.99 for immediate plating and 2.73 for delayed plating at the D10. The repair ratio (delayed plating/immediate plating) was 1.67 for 137Cs gamma rays and 1.22 for 56Fe ions. The dose-response curves for initially measured and residual chromatid fragments detected by the Calyculin A-mediated premature chromosome condensation technique showed a linear response. The results indicated that the induction frequency for initially measured fragments was the same for 137Cs gamma rays and 56Fe ions. On the other hand, approximately 85% of the fragments induced by 137Cs gamma rays had rejoined after 24 h of postirradiation incubation; the corresponding amount for 56Fe ions was 37%. Furthermore, the frequency of chromatid exchanges induced by gamma rays measured 24 h after irradiation was higher than that induced by 56Fe ions. No difference in the amount of chromatid damage induced by the two types of radiations was detected when assayed 1 h after irradiation. The results suggest that high-energy 56Fe ions induce a higher frequency of complex, unrepairable damage at both the cellular and chromosomal levels than 137Cs gamma rays in the target cells for radiation-induced lung cancers.

  15. Variations in dysfunction of sister chromatid cohesion in esco2 mutant zebrafish reflect the phenotypic diversity of Roberts syndrome

    Directory of Open Access Journals (Sweden)

    Stefanie M. Percival

    2015-08-01

    Full Text Available Mutations in ESCO2, one of two establishment of cohesion factors necessary for proper sister chromatid cohesion (SCC, cause a spectrum of developmental defects in the autosomal-recessive disorder Roberts syndrome (RBS, warranting in vivo analysis of the consequence of cohesion dysfunction. Through a genetic screen in zebrafish targeting embryonic-lethal mutants that have increased genomic instability, we have identified an esco2 mutant zebrafish. Utilizing the natural transparency of zebrafish embryos, we have developed a novel technique to observe chromosome dynamics within a single cell during mitosis in a live vertebrate embryo. Within esco2 mutant embryos, we observed premature chromatid separation, a unique chromosome scattering, prolonged mitotic delay, and genomic instability in the form of anaphase bridges and micronuclei formation. Cytogenetic studies indicated complete chromatid separation and high levels of aneuploidy within mutant embryos. Amongst aneuploid spreads, we predominantly observed decreases in chromosome number, suggesting that either cells with micronuclei or micronuclei themselves are eliminated. We also demonstrated that the genomic instability leads to p53-dependent neural tube apoptosis. Surprisingly, although many cells required Esco2 to establish cohesion, 10-20% of cells had only weakened cohesion in the absence of Esco2, suggesting that compensatory cohesion mechanisms exist in these cells that undergo a normal mitotic division. These studies provide a unique in vivo vertebrate view of the mitotic defects and consequences of cohesion establishment loss, and they provide a compensation-based model to explain the RBS phenotypes.

  16. Securin and not CDK1/cyclin B1 regulates sister chromatid disjunction during meiosis II in mouse eggs.

    Science.gov (United States)

    Nabti, Ibtissem; Reis, Alexandra; Levasseur, Mark; Stemmann, Olaf; Jones, Keith T

    2008-09-15

    Mammalian eggs remain arrested at metaphase of the second meiotic division (metII) for an indeterminate time before fertilization. During this period, which can last several hours, the continued attachment of sister chromatids is thought to be achieved by inhibition of the protease separase. Separase is known to be inhibited by binding either securin or Maturation (M-Phase)-Promoting Factor, a heterodimer of CDK1/cyclin B1. However, the relative contribution of securin and CDK/cyclin B1 to sister chromatid attachment during metII arrest has not been assessed. Although there are conditions in which either CDK1/cyclinB1 activity or securin can prevent sister chromatid disjunction, principally by overexpression of non-degradable cyclin B1 or securin, we find here that separase activity is primarily regulated by securin and not CDK1/cyclin B1. Thus the CDK1 inhibitor roscovitine and an antibody we designed to block the interaction of CDK1/cyclin B1 with separase, both failed to induce sister disjunction. In contrast, securin morpholino knockdown specifically induced loss of sister attachment, that could be restored by securin cRNA rescue. During metII arrest separase appears primarily regulated by securin binding, not CDK1/cyclin B1. PMID:18639540

  17. Variations in dysfunction of sister chromatid cohesion in esco2 mutant zebrafish reflect the phenotypic diversity of Roberts syndrome.

    Science.gov (United States)

    Percival, Stefanie M; Thomas, Holly R; Amsterdam, Adam; Carroll, Andrew J; Lees, Jacqueline A; Yost, H Joseph; Parant, John M

    2015-08-01

    Mutations in ESCO2, one of two establishment of cohesion factors necessary for proper sister chromatid cohesion (SCC), cause a spectrum of developmental defects in the autosomal-recessive disorder Roberts syndrome (RBS), warranting in vivo analysis of the consequence of cohesion dysfunction. Through a genetic screen in zebrafish targeting embryonic-lethal mutants that have increased genomic instability, we have identified an esco2 mutant zebrafish. Utilizing the natural transparency of zebrafish embryos, we have developed a novel technique to observe chromosome dynamics within a single cell during mitosis in a live vertebrate embryo. Within esco2 mutant embryos, we observed premature chromatid separation, a unique chromosome scattering, prolonged mitotic delay, and genomic instability in the form of anaphase bridges and micronuclei formation. Cytogenetic studies indicated complete chromatid separation and high levels of aneuploidy within mutant embryos. Amongst aneuploid spreads, we predominantly observed decreases in chromosome number, suggesting that either cells with micronuclei or micronuclei themselves are eliminated. We also demonstrated that the genomic instability leads to p53-dependent neural tube apoptosis. Surprisingly, although many cells required Esco2 to establish cohesion, 10-20% of cells had only weakened cohesion in the absence of Esco2, suggesting that compensatory cohesion mechanisms exist in these cells that undergo a normal mitotic division. These studies provide a unique in vivo vertebrate view of the mitotic defects and consequences of cohesion establishment loss, and they provide a compensation-based model to explain the RBS phenotypes.

  18. RSC facilitates Rad59-dependent homologous recombination between sister chromatids by promoting cohesin loading at DNA double-strand breaks.

    Science.gov (United States)

    Oum, Ji-Hyun; Seong, Changhyun; Kwon, Youngho; Ji, Jae-Hoon; Sid, Amy; Ramakrishnan, Sreejith; Ira, Grzegorz; Malkova, Anna; Sung, Patrick; Lee, Sang Eun; Shim, Eun Yong

    2011-10-01

    Homologous recombination repairs DNA double-strand breaks by searching for, invading, and copying information from a homologous template, typically the homologous chromosome or sister chromatid. Tight wrapping of DNA around histone octamers, however, impedes access of repair proteins to DNA damage. To facilitate DNA repair, modifications of histones and energy-dependent remodeling of chromatin are required, but the precise mechanisms by which chromatin modification and remodeling enzymes contribute to homologous DNA repair are unknown. Here we have systematically assessed the role of budding yeast RSC (remodel structure of chromatin), an abundant, ATP-dependent chromatin-remodeling complex, in the cellular response to spontaneous and induced DNA damage. RSC physically interacts with the recombination protein Rad59 and functions in homologous recombination. Multiple recombination assays revealed that RSC is uniquely required for recombination between sister chromatids by virtue of its ability to recruit cohesin at DNA breaks and thereby promoting sister chromatid cohesion. This study provides molecular insights into how chromatin remodeling contributes to DNA repair and maintenance of chromatin fidelity in the face of DNA damage.

  19. Induction of sister chromatid exchanges in xeroderma pigmentosum cells after exposure to ultraviolet light

    International Nuclear Information System (INIS)

    The role of DNA repair mechanisms in the induction of sister chromatid exchanges (SCE) after exposure to ultraviolet radiation was investigated in xeroderma pigmentosum cells. Cells from different excision-deficient XP strains, representing the 5 complementation groups in XP, A, B, C, D and E, and from excision-proficient XP variant strains were irradiated with low doses of UVR (0-3.5 J/m2). The number of SCE was counted after two cycles in the presence of BUdR. In cells of the complementation groups A, B, C and D the number of SCE was significantly higher than in UV-exposed control cells. The frequencies of SCE in group E cells and in XP variant cells were not different from those in control cells. Treatment with caffeine (0-200 μg/ml) did not result in a different response of variant cells compared with normal cells. A simple correlation between SCE frequency and residual excision-repair activity was not observed. The response of the excision-repair deficient cells suggests that unrepaired damage, produced by UVR is involved in the production of SCE

  20. Mutagen sensitivity as measured by induced chromatid breakage as a marker of cancer risk.

    Science.gov (United States)

    Wu, Xifeng; Zheng, Yun-Ling; Hsu, T C

    2014-01-01

    Risk assessment is now recognized as a multidisciplinary process, extending beyond the scope of traditional epidemiologic methodology to include biological evaluation of interindividual differences in carcinogenic susceptibility. Modulation of environmental exposures by host genetic factors may explain much of the observed interindividual variation in susceptibility to carcinogenesis. These genetic factors include, but are not limited to, carcinogen metabolism and DNA repair capacity. This chapter describes a standardized method for the functional assessment of mutagen sensitivity. This in vitro assay measures the frequency of mutagen-induced breaks in the chromosomes of peripheral blood lymphocytes. Mutagen sensitivity assessed by this method has been shown to be a significant risk factor for tobacco-related maladies, especially those of the upper aerodigestive tract. Mutagen sensitivity may therefore be a useful member of a panel of susceptibility markers for defining high-risk subgroups for chemoprevention trials. This chapter describes methods for and discusses results from studies of mutagen sensitivity as measured by quantifying chromatid breaks induced by clastogenic agents, such as the γ-radiation mimetic DNA cross-linking agent bleomycin and chemicals that form so-called bulky DNA adducts, such as 4-nitroquinoline and the tobacco smoke constituent benzo[a]pyrene, in short-term cultured peripheral blood lymphocytes.

  1. Role of the Saccharomyces cerevisiae Rad51 paralogs in sister chromatid recombination.

    Science.gov (United States)

    Mozlin, Amy M; Fung, Cindy W; Symington, Lorraine S

    2008-01-01

    Rad51 requires a number of other proteins, including the Rad51 paralogs, for efficient recombination in vivo. Current evidence suggests that the yeast Rad51 paralogs, Rad55 and Rad57, are important in formation or stabilization of the Rad51 nucleoprotein filament. To gain further insights into the function of the Rad51 paralogs, reporters were designed to measure spontaneous or double-strand break (DSB)-induced sister or nonsister recombination. Spontaneous sister chromatid recombination (SCR) was reduced 6000-fold in the rad57 mutant, significantly more than in the rad51 mutant. Although the DSB-induced recombination defect of rad57 was suppressed by overexpression of Rad51, elevated temperature, or expression of both mating-type alleles, the rad57 defect in spontaneous SCR was not strongly suppressed by these same factors. In addition, the UV sensitivity of the rad57 mutant was not strongly suppressed by MAT heterozygosity, even though Rad51 foci were restored under these conditions. This lack of suppression suggests that Rad55 and Rad57 have different roles in the recombinational repair of stalled replication forks compared with DSB repair. Furthermore, these data suggest that most spontaneous SCR initiates from single-stranded gaps formed at stalled replication forks rather than DSBs.

  2. Defective sister chromatid cohesion is synthetically lethal with impaired APC/C function.

    Science.gov (United States)

    de Lange, Job; Faramarz, Atiq; Oostra, Anneke B; de Menezes, Renee X; van der Meulen, Ida H; Rooimans, Martin A; Rockx, Davy A; Brakenhoff, Ruud H; van Beusechem, Victor W; King, Randall W; de Winter, Johan P; Wolthuis, Rob M F

    2015-01-01

    Warsaw breakage syndrome (WABS) is caused by defective DDX11, a DNA helicase that is essential for chromatid cohesion. Here, a paired genome-wide siRNA screen in patient-derived cell lines reveals that WABS cells do not tolerate partial depletion of individual APC/C subunits or the spindle checkpoint inhibitor p31(comet). A combination of reduced cohesion and impaired APC/C function also leads to fatal mitotic arrest in diploid RPE1 cells. Moreover, WABS cell lines, and several cancer cell lines with cohesion defects, display a highly increased response to a new cell-permeable APC/C inhibitor, apcin, but not to the spindle poison paclitaxel. Synthetic lethality of APC/C inhibition and cohesion defects strictly depends on a functional mitotic spindle checkpoint as well as on intact microtubule pulling forces. This indicates that the underlying mechanism involves cohesion fatigue in response to mitotic delay, leading to spindle checkpoint re-activation and lethal mitotic arrest. Our results point to APC/C inhibitors as promising therapeutic agents targeting cohesion-defective cancers. PMID:26423134

  3. Sister chromatid exchange in human lymphocytes induced by propoxur following plant activation by Vicia faba.

    Science.gov (United States)

    Gómez-Arroyo, S; Calderón-Segura, M E; Villalobos-Pietrini, R

    1995-01-01

    Because the carbamate insecticide propoxur induced sister chromatid exchanges (SCE) in Vicia faba but was ineffective in producing SCE in lymphocytes in culture, it was hardly suspected that plant metabolism was involved. Experiments were conducted in which metabolic activation was afforded by Vicia faba roots, and SCE in human lymphocytes in vitro was used to assess cytogenetic damage. Several concentrations of propoxur (250, 500, 1,000, 1,500, and 2,000 ppm) were applied for 4 hr to the roots of Vicia faba. Extracts prepared from these treatments were added to the lymphocyte cultures and a significant increase of SCE frequencies with a concentration-response relationship could be detected. The lymphocyte proliferation kinetics and the proliferation rate index (PRI) were not affected (except in the highest concentration, of 2,000 ppm). This general behavior was in agreement with the presence of an enzymatic system (S10 fraction) in Vicia roots capable of metabolizing or activating the propoxur. With 2,000 ppm, cell necrosis was produced in Vicia; therefore, this extract did not induce SCE in lymphocytes. However, lymphocyte proliferation kinetics were delayed and PRI was significantly decreased. Ethanol, a promutagen activated by this plant, was applied directly to the lymphocyte cultures as a positive control, and the response was negative. On the other hand, the extracts of roots treated with ethanol increased the SCE to more than twice that of the negative control, but the lymphocyte proliferation kinetics and PRI were not affected.

  4. Correlation of drug-induced sister chromatid exchanges in vitro with in vivo tumor response

    International Nuclear Information System (INIS)

    A spontaneous hepatocarcinoma (HCa) grown in C/sub 3/Hf/Kam mice was used to investigate the ability of the in vitro sister chromatid exchange (SCE) assay to predict in vivo tumor sensitivity to 3 chemotherapeutic agents: melphalan, cis-Platinum, and BCNU. For HCa cells grown in monolayer culture, melphalan was the most efficient at inducing SCEs, followed by cis-Platinum, with BCNU inducing the least. According to in vitro cell survival curves, HCa was most sensitive to melphalan, less sensitive to cis-Platinum, and essentially resistant to BCNU. The relative antineoplastic effects of melphalan, cis-Platinum, and BCNU in vivo were compared by the response of artificial and spontaneous pulmonary metastases and solid tumors to these agents. BCNU had no effect on the number of artificial metastases, while there was a dose-dependent decrease in the number of lung nodules in mice treated with melphalan or cis-Platinum, with melphalan being the more effective. Spontaneous pulmonary metastases generated from HCa leg tumors were reduced in those mice treated with melphalan, unaffected by cis-Platinum, and increased by BCNU. In HCa leg tumors (5 to 6 mm in diameter), melphalan induced the longest growth delay, with cis-Platinum inducing less, and BCNU the least. Thus, the relative effects produced by these 3 drugs in vivo were the same as predicted by SCE assay in vitro

  5. A high rate of telomeric sister chromatid exchange occurs in chronic lymphocytic leukaemia B-cells.

    Science.gov (United States)

    Medves, Sandrine; Auchter, Morgan; Chambeau, Laetitia; Gazzo, Sophie; Poncet, Delphine; Grangier, Blandine; Verney, Aurélie; Moussay, Etienne; Ammerlaan, Wim; Brisou, Gabriel; Morjani, Hamid; Géli, Vincent; Palissot, Valérie; Berchem, Guy; Salles, Gilles; Wenner, Thomas

    2016-07-01

    Cancer cells protect their telomere ends from erosion through reactivation of telomerase or by using the Alternative Lengthening of Telomere (ALT) mechanism that depends on homologous recombination. Chronic lymphocytic leukaemia (CLL) B cells are characterized by almost no telomerase activity, shelterin deregulation and telomere fusions. To characterize telomeric maintenance mechanisms in B-CLL patients, we measured their telomere length, telomerase expression and the main hallmarks of the ALT activity i.e. C-circle concentration, an extra-chromosomal telomere repeat (ECTR), and the level of telomeric sister chromatid exchange (T-SCE) rate. Patients showed relative homogenous telomere length although almost no TERT transcript and nearly no C-circle were evidenced. Nevertheless, compared with normal B cells, B-CLL cells showed an increase in T-SCE rate that was correlated with a strong down-regulation of the topoisomerase III alpha (TOP3A) expression, involved in the dissolution of Holliday Junctions (HJ), together with an increased expression of SLX1A, SLX4, MUS81 and GEN1, involved in the resolution of HJ. Altogether, our results suggest that the telomere maintenance mechanism of B-CLL cells do not preferentially use telomerase or ALT. Rather, the rupture of the dissolvasome/resolvasome balance may increase telomere shuffling that could homogenize telomere length, slowing telomere erosion in this disease. PMID:26970083

  6. Induction of sister chromatid exchanges by coal dust and tobacco snuff extracts in human peripheral lymphocytes

    Energy Technology Data Exchange (ETDEWEB)

    Tucker, J.D.; Ong, T.

    1985-01-01

    The organic solvent extracts of sub-bituminous coal dust and tobacco snuff, both together and separately, were tested for the induction of sister chromatid exchanges (SCEs) in human peripheral lymphocytes. The results indicate that these extracts induced SCEs, and that when tested together synergistically induced SCEs in two of three donors. Studies with the organic solvent extracts of all five ranks of coal indicate that the extracts of bituminous, lignite, and peat, but not anthracite, induced SCEs. Similar experiments conducted with water extracts, induced SCEs, and that anthracite was equivocal. To determine whether individuals differed in their SCE responses to coal dust extracts, lymphocytes from five donors were tested with organic solvent extracts of bituminous and sub-bituminous coal. An analysis of variance indicates that the SCE response was significantly influenced by the donor and each of the two coal extracts. The findings presented here suggest that coal dust, with or without tobacco snuff, may play a role in the elevated incidence of gastric cancer in coal miners. Because water extracts of some ranks of coal induced SCEs, there exists the possibility of adverse environmental effects due to coal leachates.

  7. DNA crosslinking, sister-chromatid exchange and specific-locus mutations.

    Science.gov (United States)

    Carrano, A V; Thompson, L H; Stetka, D G; Minkler, J L; Mazrimas, J A; Fong, S

    1979-11-01

    Chinese hamster ovary cells were treated with the DNA-crosslinking chemicals, mitomycin C (MMC) and porfiromycin (POR), and their monofunctional derivative decarbamoyl mitomycin C (DCMMC). After exposure, the cells were studied for the induction of sister-chromatid exchanges (SCEs) and mutations at the hypoxanthine phosphoribosyltransferase and adenine phosphoribosyltransferase loci. The frequency of SCEs varied significantly in successive sampling intervals, requiring the weighting of each interval by the percentage of second-division mitosis in that interval to obtain the mean SCE frequency for each dose. All 3 compounds were potent inducers of SCEs but weakly mutagenic. All 3 chemicals by concentration were approximately equally effective in inducing SCEs or mutations. When the induced SCEs and mutations were compared at equal levels of survival, DCMMC was slightly more effective than MMC or POR in inducing SCEs and somewhat less mutagenic. These results indicate that the DNA interstrand crosslink is not the major lesion responsible for the induction of SCE or mutation by these compounds. PMID:522865

  8. DNA crosslinking, sister-chromatid exchange and specific-locus mutations

    Energy Technology Data Exchange (ETDEWEB)

    Carrano, A.V.; Thompson, L.H.; Stetka, D.G.; Minkler, J.L.; Mazrimas, J.A.; Fong, S.

    1979-01-01

    Chinese hamster ovary cells were treated with the DNA-crosslinking chemicals, mitomycin C (MMC) and porfiromycin (POR), and their monofunctional derivative decarbamoyl mitomycin C (DCMMC). After exposure, the cells were studied for the induction of sister-chromatid exchanges (SCEs) and mutations at the hypoxanthine phosphoribosyltransferase and adenine phosphoribosyltransferase loci. The frequency of SCEs varied significantly in successive sampling intervals, requiring the weighting of each interval by the percentage of second-division mitosis in that interval to obtain the mean SCE frequency for each dose. All 3 compounds were potent inducers of SCEs but weakly mutagenic. All 3 chemicals by concentration were approximately equally effective in inducing SCEs or mutations. When the induced SCEs and mutations were compared at equal levels of survival, DCMMC was slightly more effective than MMC or POR in inducing SCEs and somewhat less mutagenic. These results indicate that the DNA interstrand crosslink is not the major lesion responsible for the induction of SCE or mutation by these compounds.

  9. Health assessment of gasoline and fuel oxygenate vapors: micronucleus and sister chromatid exchange evaluations.

    Science.gov (United States)

    Schreiner, Ceinwen A; Hoffman, Gary M; Gudi, Ramadevi; Clark, Charles R

    2014-11-01

    Micronucleus and sister chromatid exchange (SCE) tests were performed for vapor condensate of baseline gasoline (BGVC), or gasoline with oxygenates, methyl tert-butyl ether (G/MTBE), ethyl tert butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), t-butyl alcohol (TBA), or ethanol (G/EtOH). Sprague Dawley rats (the same 5/sex/group for both endpoints) were exposed to 0, 2000, 10,000, or 20,000mg/m(3) of each condensate, 6h/day, 5days/week over 4weeks. Positive controls (5/sex/test) were given cyclophosphamide IP, 24h prior to sacrifice at 5mg/kg (SCE test) and 40mg/kg (micronucleus test). Blood was collected from the abdominal aorta for the SCE test and femurs removed for the micronucleus test. Blood cell cultures were treated with 5μg/ml bromodeoxyuridine (BrdU) for SCE evaluation. No significant increases in micronucleated immature erythrocytes were observed for any test material. Statistically significant increases in SCE were observed in rats given BGVC alone or in female rats given G/MTBE. G/TAME induced increased SCE in both sexes at the highest dose only. Although DNA perturbation was observed for several samples, DNA damage was not expressed as increased micronuclei in bone marrow cells. Inclusion of oxygenates in gasoline did not increase the effects of gasoline alone or produce a cytogenetic hazard. PMID:24852491

  10. In vitro genotoxicity of fipronil sister chromatid exchange, cytokinesis block micronucleus test, and comet assay.

    Science.gov (United States)

    Çelik, Ayla; Ekinci, Seda Yaprak; Güler, Gizem; Yildirim, Seda

    2014-03-01

    Fipronil (FP) is a phenylpyrazole pesticide developed by the transnational company Rhône-Poulenc Agro in 1987. Data on the genotoxicity and toxicity of FP are rather inadequate. In this study, we aimed to evaluate the potential genotoxic activity of FP using the single-cell microgel electrophoresis or comet assay, sister chromatid exchanges (SCEs), and micronuclei (MN) in human peripheral blood lymphocytes. In addition, the cytokinesis block proliferation index (CBPI) and proliferation index (PRI) were measured for cytotoxicity. In this study, three different doses of FP were used (0.7, 0.3, 0.1 μg/mL). Mitomycin C (2 μg/mL) and hydrogen peroxide were used as positive controls for SCE MN test systems, and comet assay, respectively. FP induced a statistically significant increase in the MN and SCE frequency and DNA damage in a dose-dependent manner in human peripheral blood lymphocytes (pcomet assay, we showed that all the doses of the FP induced DNA damage in human peripheral blood lymphocytes in vitro (p<0.05).

  11. The Relationship between Dioxin Congeners in the Breast Milk of Vietnamese Women and Sister Chromatid Exchange

    Directory of Open Access Journals (Sweden)

    Hiroyuki Suzuki

    2014-04-01

    Full Text Available The aim of this study was to clarify the relationship between dioxin concentrations in breast milk and the sister chromatid exchange (SCE frequency in women from herbicide-sprayed and non sprayed areas. Blood samples were taken from 21 women with high TCDD (tetrachlorodibenzo-p-dioxin levels from sprayed areas, 23 women with moderate TCDD levels from sprayed areas, and 19 women from non sprayed areas to determine their SCE frequency. The SCE frequencies for the high and moderate TCDD groups from the sprayed area and for the non sprayed area group were 2.40, 2.19, and 1.48 per cell, respectively. Multiple regression analysis showed that the standardized β values for 1,2,3,6,7,8-hexaCDD (β = 0.60, 1,2,3,4,6,7,8-heptaCDD (β = 0.64, and octaCDD (β = 0.65 were higher than those for TCDD (β = 0.34 and 1,2,3,7,8-pentaCDD (β = 0.42. The adjusted R2 value for polyCDDs (R2 = 0.38 was higher than that for polyCDD toxic equivalents (TEQ (toxic equivalents; R2 = 0.23. This study therefore shows that levels of hexa-, hepta-, and octaCDD, which were previously regarded as being less toxic than TCDD, are closely related to SCE frequency and that the level of dioxin (pg/g lipid is potentially more useful as an indicator than TEQ value for explaining SCE frequency.

  12. Chiasmata promote monopolar attachment of sister chromatids and their co-segregation toward the proper pole during meiosis I.

    Directory of Open Access Journals (Sweden)

    Yukinobu Hirose

    2011-03-01

    Full Text Available The chiasma is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis. Chiasmata are essential for the attachment of the homologous chromosomes to opposite spindle poles (bipolar attachment and their subsequent segregation to the opposite poles during meiosis I. However, the overall function of chiasmata during meiosis is not fully understood. Here, we show that chiasmata also play a crucial role in the attachment of sister chromatids to the same spindle pole and in their co-segregation during meiosis I in fission yeast. Analysis of cells lacking chiasmata and the cohesin protector Sgo1 showed that loss of chiasmata causes frequent bipolar attachment of sister chromatids during anaphase. Furthermore, high time-resolution analysis of centromere dynamics in various types of chiasmate and achiasmate cells, including those lacking the DNA replication checkpoint factor Mrc1 or the meiotic centromere protein Moa1, showed the following three outcomes: (i during the pre-anaphase stage, the bipolar attachment of sister chromatids occurs irrespective of chiasma formation; (ii the chiasma contributes to the elimination of the pre-anaphase bipolar attachment; and (iii when the bipolar attachment remains during anaphase, the chiasmata generate a bias toward the proper pole during poleward chromosome pulling that results in appropriate chromosome segregation. Based on these results, we propose that chiasmata play a pivotal role in the selection of proper attachments and provide a backup mechanism that promotes correct chromosome segregation when improper attachments remain during anaphase I.

  13. Inhibition of protein synthesis does not antagonize induction of UV-induced sister-chromatid exchange in xeroderma pigmentosum cells

    International Nuclear Information System (INIS)

    Cycloheximide strongly antagonizes the induction of sisterchromatid exchanges by ethyl methanesulfonate or mitomycin C in human skin fibroblast and xeroderma pigmentosum cells (group A). Analogous behavior has been observed in several other species including Chinese hamster and plant cells. This report documents an exception to that pattern: cycloheximide fails to antagonize UV-induced sister chromatid exchange in xeroderma pigmentosum cells, whereas it does in normal human skin fibroblast cells. A genetic defect in these cells is postulated to alter the UV-mediated DNA recombination process. (author)

  14. Chromosome aberrations and sister chromatid exchanges in cultured human lymphocytes treated with sodium metabisulfite, a food preservative.

    Science.gov (United States)

    Rencüzogullari, E; Ila, H B; Kayraldiz, A; Topaktaş, M

    2001-02-20

    The aim of this study was to investigate the ability of sodium metabisulfite (SMB) which is used as an antimicrobial substance in food, to induce chromosome aberrations (CA) and sister chromatid exchanges (SCE) in human lymphocytes. SMB-induced CAs and SCEs at all concentrations (75, 150 and 300 microg/ml) and treatment periods (24 and 48h) dose-dependently. However, SMB decreased the replication index (RI) and the mitotic index (MI) at the concentrations of 150 and 300 microg/ml for 24 and 48h treatment periods. This decrease was dose-dependent as well.

  15. Erythrocytes modulate cell cycle progression but not the baseline frequency of sister chromatid exchanges in pig lymphocytes

    OpenAIRE

    Miguel A. Reigosa; Sonia Soloneski; Garcia, Carlos F.; Larramendy, Marcelo L.

    1997-01-01

    The effect of co-culturing varying concentrations of pig and human red blood cells (RBCs) on the baseline frequency of sister chromatid exchanges (SCEs) and cell-cycle progression in pig plasma (PLCs) and whole blood leukocyte cultures (WBCs) was studied. No variation in SCE frequency was observed between pig control WBC and PLC. Addition of pig and human RBCs to pig PLCs did not modify the baseline frequency of SCEs. On the other hand, cell proliferation was slower in PLCs than in WBCs. The ...

  16. SNW1 enables sister chromatid cohesion by mediating the splicing of sororin and APC2 pre-mRNAs

    OpenAIRE

    van der Lelij, Petra; Stocsits, Roman R; Ladurner, Rene; Petzold, Georg; Kreidl, Emanuel; Koch, Birgit; Schmitz, Julia; Neumann, Beate; Ellenberg, Jan; Peters, Jan-Michael

    2014-01-01

    Although splicing is essential for the expression of most eukaryotic genes, inactivation of splicing factors causes specific defects in mitosis. The molecular cause of this defect is unknown. Here, we show that the spliceosome subunits SNW1 and PRPF8 are essential for sister chromatid cohesion in human cells. A transcriptome-wide analysis revealed that SNW1 or PRPF8 depletion affects the splicing of specific introns in a subset of pre-mRNAs, including pre-mRNAs encoding the cohesion protein s...

  17. In vivo study on the replicative model validity of sister chromatid exchanges production

    International Nuclear Information System (INIS)

    The sister chromatid exchanges (SCE) frequency determination has been used as index of damage to DNA, however the biological meaning of this event is still ignored. Different models in order to explain the mechanism of their formation have been proposed and they could be contained in two categories: a) those that consider that the SCE is produced by means of discreet lesions to the DNA and that they occur in the place of the lesion, and b) those that propose that the SCE is caused by a group of lesions and that therefore the place in which they occur could not be associated with a lesion in particular. The model of Painter (1980) belongs to this last group. It suggests that the region of the DNA where the clusters are united, is the only place in which the exchange of double chain could happen during the synthesis of the DNA and makes the prediction that since the x rays retard the beginning of the duplication, the pretreatment with ionizing radiation would reduce the frequency of SCE induced by agents capable to block the lengthening of the chain of DNA, that are the most efficient SCE inducers. The objective of the present work was to establish the validity of this replicative model for the SCE formation, based in its prediction. The effect of the unilateral preexposition of mouse to gamma radiation was determined on the SCE induction by Mitomycin C (MMC), in cells of the femoral bone marrow In vivo. This strategy allows to determine the effect of the pretreatment in the same organism, minimizing the variability of the response between individuals. There was not a significant variability between the frequencies of SCE, basal and induced by gamma radiation or MMC in the same organism. The animals that received the gamma radiation pretreatment, showed a reduction of approximately the 30 % in the frequency of SCE, assuming an additive effect of the radiation with the MMC. These results coincide with the prediction of the model of Painter, however it is not

  18. The MCM-binding protein ETG1 aids sister chromatid cohesion required for postreplicative homologous recombination repair.

    Directory of Open Access Journals (Sweden)

    Naoki Takahashi

    2010-01-01

    Full Text Available The DNA replication process represents a source of DNA stress that causes potentially spontaneous genome damage. This effect might be strengthened by mutations in crucial replication factors, requiring the activation of DNA damage checkpoints to enable DNA repair before anaphase onset. Here, we demonstrate that depletion of the evolutionarily conserved minichromosome maintenance helicase-binding protein ETG1 of Arabidopsis thaliana resulted in a stringent late G2 cell cycle arrest. This arrest correlated with a partial loss of sister chromatid cohesion. The lack-of-cohesion phenotype was intensified in plants without functional CTF18, a replication fork factor needed for cohesion establishment. The synergistic effect of the etg1 and ctf18 mutants on sister chromatid cohesion strengthened the impact on plant growth of the replication stress caused by ETG1 deficiency because of inefficient DNA repair. We conclude that the ETG1 replication factor is required for efficient cohesion and that cohesion establishment is essential for proper development of plants suffering from endogenous DNA stress. Cohesion defects observed upon knockdown of its human counterpart suggest an equally important developmental role for the orthologous mammalian ETG1 protein.

  19. Rtt107 phosphorylation promotes localisation to DNA double-stranded breaks (DSBs and recombinational repair between sister chromatids.

    Directory of Open Access Journals (Sweden)

    Pranav Ullal

    Full Text Available Efficient repair of DNA double-stranded breaks (DSB requires a coordinated response at the site of lesion. Nucleolytic resection commits repair towards homologous recombination, which preferentially occurs between sister chromatids. DSB resection promotes recruitment of the Mec1 checkpoint kinase to the break. Rtt107 is a target of Mec1 and serves as a scaffold during repair. Rtt107 plays an important role during rescue of damaged replication forks, however whether Rtt107 contributes to the repair of DSBs is unknown. Here we show that Rtt107 is recruited to DSBs induced by the HO endonuclease. Rtt107 phosphorylation by Mec1 and its interaction with the Smc5-Smc6 complex are both required for Rtt107 loading to breaks, while Rtt107 regulators Slx4 and Rtt101 are not. We demonstrate that Rtt107 has an effect on the efficiency of sister chromatid recombination (SCR and propose that its recruitment to DSBs, together with the Smc5-Smc6 complex is important for repair through the SCR pathway.

  20. Frequent and efficient use of the sister chromatid for DNA double-strand break repair during budding yeast meiosis.

    Directory of Open Access Journals (Sweden)

    Tamara Goldfarb

    Full Text Available Recombination between homologous chromosomes of different parental origin (homologs is necessary for their accurate segregation during meiosis. It has been suggested that meiotic inter-homolog recombination is promoted by a barrier to inter-sister-chromatid recombination, imposed by meiosis-specific components of the chromosome axis. Consistent with this, measures of Holliday junction-containing recombination intermediates (joint molecules [JMs] show a strong bias towards inter-homolog and against inter-sister JMs. However, recombination between sister chromatids also has an important role in meiosis. The genomes of diploid organisms in natural populations are highly polymorphic for insertions and deletions, and meiotic double-strand breaks (DSBs that form within such polymorphic regions must be repaired by inter-sister recombination. Efforts to study inter-sister recombination during meiosis, in particular to determine recombination frequencies and mechanisms, have been constrained by the inability to monitor the products of inter-sister recombination. We present here molecular-level studies of inter-sister recombination during budding yeast meiosis. We examined events initiated by DSBs in regions that lack corresponding sequences on the homolog, and show that these DSBs are efficiently repaired by inter-sister recombination. This occurs with the same timing as inter-homolog recombination, but with reduced (2- to 3-fold yields of JMs. Loss of the meiotic-chromosome-axis-associated kinase Mek1 accelerates inter-sister DSB repair and markedly increases inter-sister JM frequencies. Furthermore, inter-sister JMs formed in mek1Δ mutants are preferentially lost, while inter-homolog JMs are maintained. These findings indicate that inter-sister recombination occurs frequently during budding yeast meiosis, with the possibility that up to one-third of all recombination events occur between sister chromatids. We suggest that a Mek1-dependent reduction in

  1. In Vitro genotoxic and antigenotoxic studies of Thai Noni fruit juice by chromosomal aberration and sister chromatid exchange assays in human lymphocytes

    OpenAIRE

    Treetip Ratanavalachai; Sumon Thitiorul; Pranee Nandhasri

    2008-01-01

    The genotoxic and antigenotoxic effects of Noni fruit juice produced in Thailand have been studied in human lymphocytes for chromosome aberration assay and sister chromatid exchange (SCE) assay in vitro. Treatment of Noni fruit juice(3.1-50 mg/ml) alone for 3 h did not significantly induce chromosomal aberration or SCE (p

  2. Rec8p, a meiotic recombination and sister chromatid cohesion phosphoprotein of the Rad21p family conserved from fision yeast to humans.

    NARCIS (Netherlands)

    S. Parisi; M.J. McKay (Michael); M. Molnar; M.A. Thompson (Anne); P.J. van der Spek (Peter); E. van Drunen-Schoenmaker; R. Kanaar (Roland); E. Lehmann; J.H.J. Hoeijmakers (Jan); J. Kohli

    1999-01-01

    textabstractOur work and that of others defined mitosis-specific (Rad21 subfamily) and meiosis-specific (Rec8 subfamily) proteins involved in sister chromatid cohesion in several eukaryotes, including humans. Mutation of the fission yeast Schizosaccharomyces pombe rec8 gene was previously shown to c

  3. Induction of sister-chromatid exchanges in ICR 2A frog cells exposed to 254 nm UV wavelengths

    International Nuclear Information System (INIS)

    Exposure of ICR 2A frog cells to 254 nm UV induced the formation of sister-chromatid exchanges (SCEs) in a fluence-dependent manner. Cells were also exposed to the UV produced by a fluorescent sunlamp that was filtered through 8C Mylar in order to simulate the mid-UV (290-320 nm) portion of sunlight reaching the earth's surface. In this instance, SCEs were induced in a linear fashion at low fluences but reached a plateau at a low level of induced SCEs. In addition, pretreatment of cells with the solar UV followed by exposure to 254 nm UV resulted in a significantly lower level of SCEs than in cells exposed to 254 nm UV alone. (author)

  4. Early mouse embryos exhibit strain variation in radiation-induced sister-chromatid exchange: relationship with DNA repair.

    Science.gov (United States)

    Bennett, J; Pedersen, R A

    1984-04-01

    Although mature mammalian sperm are incapable of DNA repair, repair of damaged sperm DNA can occur after fertilization, as the sperm head decondenses and forms the male pronucleus. To quantify the cytogenetic effects of damage to sperm DNA we adapted the sister-chromatid exchange (SCE) test for use in early mouse embryos. After ultraviolet (UV) irradiation of sperm, eggs were fertilized in vitro and cultured for 2 cell cycles in medium containing fluorodeoxyuridine and bromodeoxyuridine; chromosomes were then prepared for SCE analysis. We found that UV-induced SCEs could be detected at the second cleavage division, and that eggs of different strains showed different frequencies of SCEs when fertilized by damaged sperm of a single strain. These results may indicate strain-specific differences in DNA repair of UV-induced DNA lesions by the early mouse embryo.

  5. Early mouse embryos exhibit strain variation in radiation-induced sister-chromatid exchange: relationship with DNA repair

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, J. (California Univ., San Francisco (USA). Lab. of Radiobiology); Pedersen, R.A. (California Univ., San Francisco (USA). Dept. of Anatomy)

    1984-04-01

    Although mature mammalian sperm are incapable of DNA repair, repair of damaged sperm DNA can occur after fertilization, as the sperm head decondenses and forms the male pronucleus. To quantify the cytogenetic effects of damage to sperm DNA we adapted the sister-chromatid exchange (SCE) test for use in early mouse embryos. After ultraviolet (UV) irradiation of sperm, eggs were fertilized in vitro and cultured for 2 cell cycles in medium containing fluorodeoxyuridine and bromodeoxyuridine; chromosomes were then prepared for SCE analysis. We found that UV-induced SCEs could be detected at the second cleavage division, and that eggs of different strains showed different frequencies of SCEs when fertilized by damaged sperm of a single strain. These results may indicate strain-specific differences in DNA repair of UV-induced DNA lesions by the early mouse embryo.

  6. Recombinant chromosome 9 possibly derived from breakage and reunion of sister chromatids within a paracentric inversion loop.

    Science.gov (United States)

    Phelan, M C; Stevenson, R E; Anderson, E V

    1993-05-15

    Chromosomally unbalanced offspring resulting from the recombination of parental paracentric inversions are uncommon. We report on a 20-month-old boy with a partial duplication of 9p due to the recombination of a paternal paracentric inversion. The patient's recombinant chromosome was designated rec(9)(p13-->p24::p12-->p24::p12-->qter). The patient's father and paternal aunt have a paracentric inversion of chromosome 9:inv(9)(p13p24). Although several mechanisms have been proposed to explain the chromosome imbalance generated from paracentric inversions, none of the previously described mechanisms can account for the structure of the recombinant chromosome observed in the propositus. We propose an unusual mechanism of formation involving breakage and unequal reunion of sister chromatids within the inversion loop to explain the structure of the patient's recombinant chromosome. PMID:8488876

  7. Test of radiation damage enhancement due to incorporation of BrUdR into DNA using chromatid aberrations

    International Nuclear Information System (INIS)

    Monte Carlo track structure calculations, leading to an estimation of the magnitude of enhancement of radiation damage due to the incorporation of the halogenated pyrimidine, bromodeoxyuridine (BrUdR) a thymine analog, into DNA have been made. The increase in the yield of double strand breaks for various degrees of substitution in one (monofilarly) or both strands (bifilarly) have been calculated. To test these calculations, quantitative selected radiation-induced aberrations have been obtained in Chinese hamster (V79) fibroblast chromosomes having various patterns of BrUdR substitution following irradiation with 250 kV X rays. Free ''breaks'' and achromatic lesions ''gaps'' show no appreciable sensitizations, but breaks involved in chromatid interchanges show significant enhancement though of lower magnitude than theoretical predictions

  8. SGO1 maintains bovine meiotic and mitotic centromeric cohesions of sister chromatids and directly affects embryo development.

    Directory of Open Access Journals (Sweden)

    Feng-Xia Yin

    Full Text Available Shugoshin (SGO is a critical factor that enforces cohesion from segregation of paired sister chromatids during mitosis and meiosis. It has been studied mainly in invertebrates. Knowledge of SGO(s in a mammalian system has only been reported in the mouse and Hela cells. In this study, the functions of SGO1 in bovine oocytes during meiotic maturation, early embryonic development and somatic cell mitosis were investigated. The results showed that SGO1 was expressed from germinal vesicle (GV to the metaphase II stage. SGO1 accumulated on condensed and scattered chromosomes from pre-metaphase I to metaphase II. The over-expression of SGO1 did not interfere with the process of homologous chromosome separation, although once separated they were unable to move to the opposing spindle poles. This often resulted in the formation of oocytes with 60 replicated chromosomes. Depletion of SGO1 in GV oocytes affected chromosomal separation resulting in abnormal chromosome alignment at a significantly higher proportion than in control oocytes. Knockdown of SGO1 expression significantly decreased the embryonic developmental rate and quality. To further confirm the function(s of SGO1 during mitosis, bovine embryonic fibroblast cells were transfected with SGO1 siRNAs. SGO1 depletion induced the premature dissociation of chromosomal cohesion at the centromere and along the chromosome arm giving rise to abnormal appearing mitotic patterns. The results of this study infer that SGO1 is involved in the centromeric cohesion of sister chromatids and chromosomal movement towards the spindle poles. Depletion of SGO1 causes arrestment of cell division in meiosis and mitosis.

  9. RSC Facilitates Rad59-Dependent Homologous Recombination between Sister Chromatids by Promoting Cohesin Loading at DNA Double-Strand Breaks ▿

    OpenAIRE

    Oum, Ji-Hyun; Seong, Changhyun; Kwon, YoungHo; Ji, Jae-Hoon; Sid, Amy; Ramakrishnan, Sreejith; Ira, Grzegorz; Malkova, Anna; Sung, Patrick; Lee, Sang Eun; Shim, Eun Yong

    2011-01-01

    Homologous recombination repairs DNA double-strand breaks by searching for, invading, and copying information from a homologous template, typically the homologous chromosome or sister chromatid. Tight wrapping of DNA around histone octamers, however, impedes access of repair proteins to DNA damage. To facilitate DNA repair, modifications of histones and energy-dependent remodeling of chromatin are required, but the precise mechanisms by which chromatin modification and remodeling enzymes cont...

  10. Left-right symmetry breaking in mice by left-right dynein may occur via a biased chromatid segregation mechanism, without directly involving the Nodal gene

    Directory of Open Access Journals (Sweden)

    Stephan eSauer

    2012-11-01

    Full Text Available Ever since cloning the classic iv mutation identified the ‘left-right dynein’ (lrd gene in mice, most research on body laterality determination has focused on its function in motile cilia at the node embryonic organizer. This model is attractive, as it links chirality of cilia architecture to asymmetry development. However, lrd is also expressed in blastocysts and embryonic stem cells, where it was shown to bias the segregation of recombined sister chromatids away from each other in mitosis. These data suggested that lrd is part of a cellular mechanism that recognizes and selectively segregates sister chromatids based on their replication history: old ‘Watson’ vs. old ‘Crick’ strands. We previously proposed that the mouse left-right axis is established via an asymmetric cell division prior to/or during gastrulation. In this model, left-right dynein selectively segregates epigenetically differentiated sister chromatids harboring a hypothetical ‘left-right axis development 1’ (‘lra1’ gene during the left-right axis establishing cell division. Here, asymmetry development would be ultimately governed by the chirality of the cytoskeleton and the DNA molecule. Our model predicts that randomization of chromatid segregation in lrd mutants should produce embryos with 25% situs solitus, 25% situs inversus, and 50% embryonic death due to heterotaxia and isomerism. Here we confirmed this prediction by using two distinct lrd mutant alleles. Other than lrd, thus far Nodal gene is the most upstream function implicated in visceral organs laterality determination. We next tested whether the Nodal gene constitutes the lra1 gene hypothesized in the model by testing mutant’s effect on 50% embryonic lethality observed in lrd mutants. Since Nodal mutation did not suppress lethality, we conclude that Nodal is not equivalent to the lra1 gene. In summary, we describe the origin of 50% lethality in lrd mutant mice not yet explained by any other

  11. DNA single strand breakage, DNA adducts, and sister chromatid exchange in lymphocytes and phenanthrene and pyrene metabolites in urine of coke oven workers.

    OpenAIRE

    W. Popp; Vahrenholz, C.; Schell, C; Grimmer, G.; Dettbarn, G; Kraus, R.; Brauksiepe, A; Schmeling, B; Gutzeit, T; von Bülow, J; Norpoth, K

    1997-01-01

    OBJECTIVES: To investigate the specificity of biological monitoring variables (excretion of phenanthrene and pyrene metabolites in urine) and the usefulness of some biomarkers of effect (alkaline filter elution, 32P postlabelling assay, measurement of sister chromatid exchange) in workers exposed to polycyclic aromatic hydrocarbons (PAHs). METHODS: 29 coke oven workers and a standardised control group were investigated for frequencies of DNA single strand breakage, DNA protein cross links (al...

  12. Inhibition of UV-induced sister chromatid exchanges in ICR 2A frog cells by pretreatment with γ-rays

    International Nuclear Information System (INIS)

    Exposure of ICR 2A frog cells to UV induced the formation of sister chromatid exchanges (SCEs). However, pretreatment of UV-irradiated cells with γ-rays resulted in a reduction in the level of SCEs, confirming the prediction made by the replication model for SCE induction. This effect was observed over a range of UV fluences (1-5 J/m/sup 2/) and γ-ray doses (50-500 rad). The depression in the yield of SCEs was greatest when the cells were UV-irradiated either immediately or 3 h after γ-irradiation. Following a 6 h incubation, the reduction was much less pronounced while at 48 h the level of SCEs was nearly identical to that of cells exposed to UV alone. This corresponds roughly to the kinetics of depression and recovery in DNA synthesis after γ-irradiation of ICR 2A cells. Hence, these results support the hypothesis that the depression of UV-induced SCEs was the result of a delay in replicon initiation caused by //i/-irradiation

  13. Effect of chlorophyllin on induction of exchanges in sister chromatids by gamma irradiation in mice spermatogonia in vivo

    International Nuclear Information System (INIS)

    Mouse were exposed to different doses of gamma radiation and the effect on Sister Chromatid Exchange (SCE) frequency in spermatogonias was evaluated. The effect was analyzed before and after Bromodeoxyuridine (BrdU) incorporation to determine the interference of such agent with the cellular response induced by radiation. The capacity of chlorophyllin (sodium and Copper salt derivative from chlorophyll) to reduce SCE induction by radiation in normal and BrdU radio sensitized spermatogonia was also determined. The results indicate that there was a significant increase in SCE frequency by gamma radiation exposure in these cells, such effect was higher irradiating after BrdU incorporation than before. This fact confirms previous observations that BrdU sensitizes some cells to SCE induction. With regard to the chlorophyllin effect, it was determined that this salt acts as a radioprotector reducing gamma-rays induced SCE before or after BrdU incorporation Total protection was obtained with 200 μg of chlorophyllin per g of body weight in both protocols. Under the experimental conditions this study there was no evidence of genotoxicity induced by chlorophyllin itself. The results suggest that this agent may act as a radioprotector by scavenging free radicals produced by gamma-radiation which cause DNA lesions that are involved in SCE formation. (Author)

  14. SNW1 enables sister chromatid cohesion by mediating the splicing of sororin and APC2 pre-mRNAs

    Science.gov (United States)

    van der Lelij, Petra; Stocsits, Roman R; Ladurner, Rene; Petzold, Georg; Kreidl, Emanuel; Koch, Birgit; Schmitz, Julia; Neumann, Beate; Ellenberg, Jan; Peters, Jan-Michael

    2014-01-01

    Although splicing is essential for the expression of most eukaryotic genes, inactivation of splicing factors causes specific defects in mitosis. The molecular cause of this defect is unknown. Here, we show that the spliceosome subunits SNW1 and PRPF8 are essential for sister chromatid cohesion in human cells. A transcriptome-wide analysis revealed that SNW1 or PRPF8 depletion affects the splicing of specific introns in a subset of pre-mRNAs, including pre-mRNAs encoding the cohesion protein sororin and the APC/C subunit APC2. SNW1 depletion causes cohesion defects predominantly by reducing sororin levels, which causes destabilisation of cohesin on DNA. SNW1 depletion also reduces APC/C activity and contributes to cohesion defects indirectly by delaying mitosis and causing “cohesion fatigue”. Simultaneous expression of sororin and APC2 from intron-less cDNAs restores cohesion in SNW1-depleted cells. These results indicate that the spliceosome is required for mitosis because it enables expression of genes essential for cohesion. Our transcriptome-wide identification of retained introns in SNW1- and PRPF8-depleted cells may help to understand the aetiology of diseases associated with splicing defects, such as retinosa pigmentosum and cancer. PMID:25257309

  15. Regulation of the Drosophila Enhancer of split and invected-engrailed gene complexes by sister chromatid cohesion proteins.

    Directory of Open Access Journals (Sweden)

    Cheri A Schaaf

    Full Text Available The cohesin protein complex was first recognized for holding sister chromatids together and ensuring proper chromosome segregation. Cohesin also regulates gene expression, but the mechanisms are unknown. Cohesin associates preferentially with active genes, and is generally absent from regions in which histone H3 is methylated by the Enhancer of zeste [E(z] Polycomb group silencing protein. Here we show that transcription is hypersensitive to cohesin levels in two exceptional cases where cohesin and the E(z-mediated histone methylation simultaneously coat the entire Enhancer of split and invected-engrailed gene complexes in cells derived from Drosophila central nervous system. These gene complexes are modestly transcribed, and produce seven of the twelve transcripts that increase the most with cohesin knockdown genome-wide. Cohesin mutations alter eye development in the same manner as increased Enhancer of split activity, suggesting that similar regulation occurs in vivo. We propose that cohesin helps restrain transcription of these gene complexes, and that deregulation of similarly cohesin-hypersensitive genes may underlie developmental deficits in Cornelia de Lange syndrome.

  16. The use of the differential staining of sister chromatids in the study of the cytogenetic radiation effects in human lymphocytes

    International Nuclear Information System (INIS)

    Differential staining of sister chromatides is performed, cells of the 1-st and the following mitoses are identified, chromosome aberrations are accounted, and statistic processing of data is performed. Venous blood of healthy donors is used as material for analysis. It is irradiated in flasks by 60Co gamma-quanta in the doses of 1, 1.5, 2, 3, 4, 5, 6, and 8 Gy. Lymphocytes of the peripheral blood are cultivated at 37 deg C in the medium containing antibiotics, phytohemaggluninin and 5-bromiurnedeoxyidine (BDU). The observed distributions of dicentrics in cells are compared with theoretic Poisson distribution. The dependence of frequency of dicentrics on radiation dose is studied by the method of regressive analysis. The importance of applying this technique in radiation cytogenetic investigations to increase the accuracy of chromosome aberration account in stimulated phytohemagglutinin cultures of lymphocytes of human peripheral blood and to study regularities of their elimination after cells pass the 1-st and the second mitoses, is shown

  17. Hypersensitivity to mutation and sister-chromatid-exchange induction in CHO cell mutants defective in incising DNA containing UV lesions

    International Nuclear Information System (INIS)

    Five UV-sensitive mutant strains of CHO cells representing different genetic complementation groups were analyzed for their ability to perform the incision step of nucleotide excision repair after UV exposure. The assay utilized inhibitors of DNA synthesis to accumulate the short-lived strand breaks resulting from repair incisions. After 6 J/m2, each of the mutants showed 2, the rate in AA8 was similar to that at 6 J/m2, but the rates in the mutants were significantly higher (approx. 20% of the rate of AA8). Thus by this incision assay the mutants were phenotypically indistinguishable. Each of the mutants were hypersensitive to mutation induction at both the hprt and aprt loci by a factor of 10, and in the one strain tested ouabain resistance was induced sevenfold more efficiently than in AA8 cells. Sister chromatid exchange was also induced with sevenfold increased efficiency in the two mutant strains examined. Thus, here CHO mutants resemble xeroderma pigmentosum cells in terms of their incision defects and their hypersensitivity to DNA damage by UV

  18. Sister chromatid exchanges and micronuclei in lymphocytes of operating room personnel occupationally exposed to enfluorane and nitrous oxide.

    Science.gov (United States)

    Pasquini, R; Scassellati-Sforzolini, G; Fatigoni, C; Marcarelli, M; Monarca, S; Donato, F; Cencetti, S; Cerami, F M

    2001-01-01

    The objective of this article is to assess whether occupational exposure to anesthetics increases genotoxic risk. We investigated two cytogenetic biomarkers, sister chromatid exchanges (SCE) and micronuclei (MN), in the peripheral blood lymphocytes of 46 anesthesiologists (24 men), working in operating rooms and mostly exposed to enfluorane and nitrous oxide, and 66 controls (35 men), not exposed to chemicals and living in the same area. Contrary to what was expected, a lower frequency of SCE was found in male anesthesiologists than in controls. Smoking status was found to be positively associated with SCE frequency in each group, while no relation to age was evident. On the contrary, MN frequency was significantly higher in female, but not male, anesthesiologists than in controls. Age and smoking status did not modify the association. No relationship between MN frequency and duration of employment was found in anesthesiologists. Smoking status and mean number of cigarettes smoked per day in smokers were not associated with MN frequency in either anesthesiologists or in controls. MN analysis seems to be a sensitive index of possible genotoxic effects of occupational exposure to anesthesiologists, and women appear to be more susceptible to these effects than men. PMID:11394710

  19. The chromosome damage induced by x-ray radiation doses. Comparison between dicentric chromosomes, micronuclei and Sister Chromatid Exchanges analyses

    International Nuclear Information System (INIS)

    Exposure to ionizing radiations is a well-known source of chromosome damage. Here we present a comparison among three different methodologies employed to recognize cytogenetic damage, after an acute exposure of human lymphocytes to 3 Gy of X-rays (100kVp). Scoring of dicentric chromosomes, present in first mitosis ''in vitro'', was the method of preference as dicentrics increased 937.5 times with respect to background. Micronucleus scoring in binucleated-cytokinesis blocked cells showed an increase of 32.5 times, while it was only of 1.46 times when Sister Chromatid Exchanges (SCEs) were analyzed. The estimated probability of an acentric fragment becoming a micronucleus was around 0.25. Intercellular distribution of dicentrics agree with Poisson, while micronucleus were overdispersed. When analyzed at second cycle after damage induction, the dicentrics yield as well as the level of cells with unstable cromosome aberrations, decreased around a half. Finally, SCEs level was similar in cells with or without unstable structural chromosome aberrations. (Author)

  20. Relationship of the demethylation of the DNA with the induction of the sister chromatid exchanges (SCE) In vivo

    International Nuclear Information System (INIS)

    The methylation of the DNA is an epigenetic modification that has an important paper in the regulation of the functionality of the genome of the organisms. It can be altered by demethylation processes, either natural or experimentally induced. The 5-azacytidine (Aza) is a compound that causes the demethylation of the DNA (dm-DNA), inducing with it, expression genic and increase in the frequency of the Sister Chromatid Exchange (SCE). The SCE is a genotoxicity indicator, caused by diverse mutagens and carcinogen. Since the biological meaning and the formation mechanism of this phenomenon has not been totally illustrious, the exploration of the relation between the dm-DNA and the induction of SCE, it could offer new knowledge to explain those queries. The purpose of this work was to study in cells of the mouse bone marrow In vivo, the effect of the Aza on the induction of SCE, based on two aspects: 1) dose answer and 2) the effectiveness of multiple exhibition. To six groups of three to five animals, they are administered Aza to dose of 5, 10, 15 or 20 mg/Kg of weight; in sharp or multiple form, previously to the bromodeoxyuridine supply and 24 h was sacrificed after this; 2 h after an injection with colchicine. Preparations of those metaphases were made, those which were dyed by means of a technique of fluorescence more Giemsa. It was observed that to sharp low dose, the Aza produced an increment in the frequency of SCE that although small it was proportional and statistically significant. To sharp and multiple high doses, the Aza doesn't cause additional increments of SCE, but if toxicity at cellular level and of individuals. It is concluded that a relationship exists between the dm-DNA and the induction of SCE. It is suggested that the total demethylation of the DNA causes 2 SCE/Cell in cells of the mouse bone marrow, or that the cytotoxicity prevents to evidence a bigger induction. (Author)

  1. Sister chromatid exchanges in the bone marrow cells of in vivo rats induced by gamma radiation and chemical mutagens

    International Nuclear Information System (INIS)

    Sister chromatid exchanges (SCE) in the bone marrow of in vivo rats induced by gamma radiation doses and by the chemical mutagens, mitomycin C (MMC), cyclophosphamide (CP), and sulphonate-methylmethane (SMM), were studied. The purpose was to evaluate the sensitivity and reproducibility of a simplified SCE in vivo detecting system developed in our laboratory and to compare the results obtained with those reported elsewhere. Simplification consisted in administering the amounts of 5-bromo-2'-deoxyuridine (BrdU) necessary to observe the SCE, after first adsorbing the BrdU in activated carbon and then injecting it interperitoneally, into the rats. The results were a longer time in vivo ADN incorporation without convulsions in the rats, and a reduction in the time course as compared to other methods. We observed a basal rate of 3.6+-0.37 SCE/cell and that: 0.44 Gy of gamma radiation induced 7.7+-0.73 SCE/cell; 1.6 μg/g of MMC induced 8.1+-1.20 SCE/cell; 5 μg/g of CP induced 8.25+-1.5 SCE/cell, 40 μg/g of SMM induced 22.0+-5 SCE/cell and 380 μg/g of sulphonate-ethylmethane induced 8.6+-1.2 SCE/cell. This showed that all the agents were capable of inducing SCE in the bone marrow cells of rats in vivo under our conditions. We noted a greater induced efficiency for gamma radiation than the obtained by other investigators and a relatively similar efficiency in the case of chemical mutagens as reported in other studies. (author)

  2. Chaetophractus villosus as a sentinel organism: Baseline values of mitotic index, chromosome aberrations and sister chromatid exchanges.

    Science.gov (United States)

    Rossi, Luis Francisco; Luaces, Juan Pablo; Browne, Melanie; Chirino, Mónica Gabriela; Merani, María Susana; Mudry, Marta Dolores

    2016-01-15

    Sentinel species are useful tools for studying the deleterious effects of xenobiotics on wildlife. The large hairy armadillo (Chaetophractus villosus) is the most abundant and widely distributed mammal in Argentina. It is a long-lived, omnivorous, burrowing species, with fairly restricted home ranges. To evaluate the level of spontaneous genetic damage in this mammal, we determined the baseline values of several genotoxicity biomarkers. The study included 20 C. villosus adults of both sexes from eight pristine localities within its geographic distribution range. Genotoxicity analysis was performed on 72-h lymphocyte cultures, using mitomycin C as positive control. We obtained the baseline values of mitotic index (MI=10.52±0.30 metaphases/total cells, n=20), chromosome aberrations (CA=0.13±0.22, n=20), sister chromatid exchanges (SCE)=6.55±0.26, n=6) and replication index (RI=1.66, n=6). MI and CA did not show significant differences (P>0.05) among localities or between sexes. No significant differences in MI, CA, SCE, and RI (P>0.05) were found between values from the pristine localities and historical data. There were significant differences in CA, SCE, and RI (Parmadillo as a sentinel organism for environmental biomonitoring of genotoxic chemicals due to its abundance, easy manipulation, well-known biology, the fact that it is usually exposed to different mixtures and concentrations of environmental contaminants, and the baseline values of genetic damage characterized by MI, CA, SCE and RI as biomarkers. PMID:26778508

  3. A novel frameshift mutation in BLM gene associated with high sister chromatid exchanges (SCE) in heterozygous family members.

    Science.gov (United States)

    Ben Salah, Ghada; Hadj Salem, Ikhlas; Masmoudi, Abderrahmen; Kallabi, Fakhri; Turki, Hamida; Fakhfakh, Faiza; Ayadi, Hamadi; Kamoun, Hassen

    2014-11-01

    The Bloom syndrome (BS) is an autosomic recessive disorder comprising a wide range of abnormalities, including stunted growth, immunodeficiency, sun sensitivity and increased frequency of various types of cancer. Bloom syndrome cells display a high level of genetic instability, including a 10-fold increase in the sister chromatid exchanges (SCE) level. Bloom syndrome arises through mutations in both alleles of the BLM gene, which was identified as a member of the RecQ helicase family. In this study, we screened a Tunisian family with three BS patients. Cytogenetic analysis showed several chromosomal aberrations, and an approximately 14-fold elevated SCE frequency in BS cells. A significant increase in SCE frequency was observed in some family members but not reaching the BS patients values, leading to suggest that this could be due to the heterozygous profile. Microsatellite genotyping using four fluorescent dye-labeled microsatellite markers revealed evidence of linkage to BLM locus and the healthy members, sharing higher SCE frequency, showed heterozygous haplotypes as expected. Additionally, the direct BLM gene sequencing identified a novel homozygous frameshift mutation c.3617-3619delAA (p.K1207fsX9) in BS patients and a heterozygous BLM mutation in the family members with higher SCE frequency. Our findings suggest that this latter mutation likely leads to a reduced BLM activity explaining the homologous recombination repair defect and, therefore, the increase in SCE. Based on the present data, the screening of this mutation could contribute to the rapid diagnosis of BS. The genetic confirmation of the mutation in BLM gene provides crucial information for genetic counseling and prenatal diagnosis.

  4. Evaluation of radioprotection properties of propolis by chromosomal alterations, cell proliferation kinetics, mitotic index and sister chromatid exchange

    International Nuclear Information System (INIS)

    A consequence of ionizing radiation is the induction of chromosomal alterations. This causality relation involves that chromosomal alterations can be considered a good indicator of the radiological damage. Some chemical agents can modulate the tissue response to radiation. These compounds are useful because they show certain selectivity, protecting the healthy tissues (radioprotectors) or increasing the sensibility of tissues to radiations (radiosensibilizators). Propolis substance has showed radioprotection properties which are performed in the following study. Propolis is a product of extraordinary interest for both medicine and pharmaceutical industry, since it is assumed to show diverse beneficial health effects. Among many other attributes of EEP (propolis ethanolic extract), it exhibits antioxidant and radical free scavenger properties. In a previous study, human peripheral blood lymphocytes were exposed to 2 Gy of γ rays in presence and absence of EEP, and the analysis showed a reduction in the frequency of dicentrics and rings, with a maximum protection of 50%. The proposed concentration for radioprotection would be between 120-500 μg.ml-1. The cytotoxic effect has been evaluated analyzing the EEP effect in the cellular division cycle. Propolis ethanolic extract (EEP) has been obtained and samples of peripheral blood have been cultured in the presence of increasing concentrations of EEP. In order to quantify it, two indexes have been used, the mitotic index and cell proliferation index. For both indexes the cytotoxic effect takes place from 750 μg.ml-1 concentrations onwards. Similar results were obtained for the analysis of chromosomal aberrations. Finally, propolis effect in lymphocytes by sister chromatid exchange test has been presented for higher concentrations of EEP. (author)

  5. Variation in sister chromatid exchange frequencies between human and pig whole blood, plasma leukocyte, and mononuclear leukocyte cultures

    International Nuclear Information System (INIS)

    Sister chromatid exchange (SCE) induction by ultraviolet (UV) light was studied in both human and pig whole blood cultures (WBC) and plasma leukocyte cultures (PLC). No variation in SCE frequency was observed between pig WBC and PLC in control as well as in treated cells. Conversely, SCE frequencies of human PLC were consistently higher than those of WBC in control and UV-exposed cells. Thus, red blood cells (RBCs) do not influence the sensitivity of lymphocytes to UV LIGHT exposure, and there must be some different culture condition(s) in the inducation of SCEs between human WBC and PLC but not in swine lymphocyte cultures. Since the BrdUrd/lymphocyte ratio of WBC was halved in PLC, the effect of BrdUrd concentration in inducing the SCE baseline frequency of PLC may be ruled out. Neither the cell separation technique nor polymorphonuclear leukocytes had a significant role in the elevated SCE frequency of human PLC or MLC. Experiments where human RBCs were titrated into human PLC showed that the induction of an elevated SCE frequency of PLC was suppressed in a dose-dependent manner by the presence of RBCs in the culture medium. Since the incorporation of pig or human RBCs into human PLC as well as into MLC reduced the SCE frequency to that of WBC, a common component and/or function existing in these cells is suggested. Analysis of different RBC components showed that RBCs, specifically RBC ghosts, release a diffusible but not dialyzable corrective factor into culture medium that is able to reduce the SCE frequencies of PLC

  6. Low doses of alpha particles do not induce sister chromatid exchanges in bystander Chinese hamster cells defective in homologous recombination

    Energy Technology Data Exchange (ETDEWEB)

    Nagasawa, H; Wilson, P F; Chen, D J; Thompson, L H; Bedford, J S; Little, J B

    2007-10-26

    We reported previously that the homologous recombinational repair (HRR)-deficient Chinese hamster mutant cell line irs3 (deficient in the Rad51 paralog Rad51C) showed only a 50% spontaneous frequency of sister chromatid exchange (SCE) as compared to parental wild-type V79 cells. Furthermore, when irradiated with very low doses of alpha particles, SCEs were not induced in irs3 cells, as compared to a prominent bystander effect observed in V79 cells (Nagasawa et al., Radiat. Res. 164, 141-147, 2005). In the present study, we examined additional Chinese hamster cell lines deficient in the Rad51 paralogs Rad51C, Rad51D, Xrcc2, and Xrcc3 as well as another essential HRR protein, Brca2. Spontaneous SCE frequencies in non-irradiated wild-type cell lines CHO, AA8 and V79 were 0.33 SCE/chromosome, whereas two Rad51C-deficient cell lines showed only 0.16 SCE/chromosome. Spontaneous SCE frequencies in cell lines defective in Rad51D, Xrcc2, Xrcc3, and Brca2 ranged from 0.23-0.33 SCE/chromosome, 0-30% lower than wild-type cells. SCEs were induced significantly 20-50% above spontaneous levels in wild-type cells exposed to a mean dose of 1.3 mGy of alpha particles (<1% of nuclei traversed by an alpha particle). However, induction of SCEs above spontaneous levels was minimal or absent after {alpha}-particle irradiation in all of the HRR-deficient cell lines. These data suggest that Brca2 and the Rad51 paralogs contribute to DNA damage repair processes induced in bystander cells (presumably oxidative damage repair in S-phase cells) following irradiation with very low doses of alpha particles.

  7. In Vitro genotoxic and antigenotoxic studies of Thai Noni fruit juice by chromosomal aberration and sister chromatid exchange assays in human lymphocytes

    Directory of Open Access Journals (Sweden)

    Treetip Ratanavalachai

    2008-09-01

    Full Text Available The genotoxic and antigenotoxic effects of Noni fruit juice produced in Thailand have been studied in human lymphocytes for chromosome aberration assay and sister chromatid exchange (SCE assay in vitro. Treatment of Noni fruit juice(3.1-50 mg/ml alone for 3 h did not significantly induce chromosomal aberration or SCE (p<0.05. Noni fruit juice at 6.2 mg/ml is the optimum dose for cell survival and cell replication as demonstrated by the highest value of mitotic index and proliferation index (P.I.. Interestingly, pretreatment of Noni fruit juice at the same concentration of 6.2 mg/ml for 2 hfollowed by mitomycin C treatment at 3 μg/ml for 2 h significantly reduced SCE level induced by mitomycin C (p<0.05. However, these treatments did not show significant decrease in chromatid-type aberrations. Our data indicate that Thai Noni fruit juice is not genotoxic against human lymphocytes in vitro. In addition, pretreatment of Noni fruit juice at 6.2 mg/ml demonstrated no anticlastogenic effect while had some antigenotoxic effects as demonstrated by significant decrease in the SCE level induced by mitomycin C (p<0.05. Therefore, the optimum dose of Noni fruit juice used as a traditional medicine is required and needs to be studied further for the benefit of human health.

  8. Increased sister chromatid cohesion and DNA damage response factor localization at an enzyme-induced DNA double-strand break in vertebrate cells.

    LENUS (Irish Health Repository)

    Dodson, Helen

    2009-10-01

    The response to DNA damage in vertebrate cells involves successive recruitment of DNA signalling and repair factors. We used light microscopy to monitor the genetic dependencies of such localization to a single, induced DNA double strand break (DSB) in vertebrate cells. We used an inducible version of the rare-cutting I-SceI endonuclease to cut a chromosomally integrated I-SceI site beside a Tet operator array that was visualized by binding a Tet repressor-GFP fusion. Formation of gamma-H2AX foci at a single DSB was independent of ATM or Ku70. ATM-deficient cells showed normal kinetics of 53Bp1 recruitment to DSBs, but Rad51 localization was retarded. 53Bp1 and Rad51 foci formation at a single DSB was greatly reduced in H2AX-null DT40 cells. We also observed decreased inter-sister chromatid distances after DSB induction, suggesting that cohesin loading at DSBs causes elevated sister chromatid cohesion. Loss of ATM reduced DSB-induced cohesion, consistent with cohesin being an ATM target in the DSB response. These data show that the same genetic pathways control how cells respond to single DSBs and to multiple lesions induced by whole-cell DNA damage.

  9. Sister-chromatid exchanges and cell-cycle kinetics in the lymphocytes of workers occupationally exposed to a chemical mixture in the tyre industry.

    Science.gov (United States)

    Sasiadek, M

    1993-08-01

    Cytogenetic studies of clinically healthy workers employed in the rubber industry showed an increase in chromosome aberrations (CAs), sister-chromatid exchanges (SCEs) and a decrease in proliferation indices (PIs). The aim of the present study was to establish, using the SCE and PI tests, genotoxic effects of hazardous chemicals in the rubber industry. An increase in mean SCEs in the lymphocytes of vulcanizers as compared to controls was observed. Since the PI in the exposed group was insignificantly decreased as compared to the controls, it could be concluded that the SCE test is the most sensitive cytogenetic test for the detection of a genotoxic effect of chemicals in the rubber industry. There was no evidence in the present study that the genotoxic effect of chemicals in the rubber industry was enhanced by cigarette smoking. PMID:7688857

  10. Effect of chlorophyllin on frequency radiation-induced of sister chromatid exchanges (SCE) and other cytogenetic events in mice bone marrow cells In Vivo

    International Nuclear Information System (INIS)

    The effect of chlorophyllin on gamma radiation induced Sister chromatid exchanges (SCE) and on the mitotic index (IM) and average generation time was determined. Groups of mice were treated in one of the following regimens: (1) untreated, (2) treated with chlorophyllin only, (3) irradiated and (4) treated with chlorophyllin and irradiated intraperitoneal administration of chlorophyllin preceding gamma radiation exposure protected again SCE induction and diminution of IM. However, radioprotection was not reflected in the average generation time for the chlorophyllin per se acceleration the average generation time. The results suggest that, under the experimental conditions of the study the SCE and IM are caused by free radicals produced by radiation and wat the action mechanics of chlorophyllin is scavenger free radicals. (Author)

  11. Sister chromatid exchanges, hyperdiploidy and chromosomal rearrangements studied in cells from melanoma-prone individuals belonging to families with the dysplastic nevus syndrome.

    Science.gov (United States)

    Jaspers, N G; Roza-de Jongh, E J; Donselaar, I G; Van Velzen-Tillemans, J T; van Hemel, J O; Rümke, P; van der Kamp, A W

    1987-01-01

    Cytogenetic investigations were performed on 25 individuals belonging to six melanoma-prone families with multiple melanocytic lesions (the dysplastic nevus syndrome, DNS). Patients having DNS with or without a history of melanoma were compared with clinically normal relatives and unrelated normal controls. The results indicate normal frequencies of hyperdiploidy and spontaneous sister chromatid exchanges in the fibroblasts of all individuals studied. Karyotypic analyses were carried out on the members of one family. The patients with DNS had a normal constitutional karyotype. In lymphocytes or fibroblasts from five patients, however, increased frequencies of cells with random chromosomal rearrangements were observed. These abnormalities, mainly translocations and inversions, were not found in two of the patients' spouses and in six clinically normal relatives. In the fibroblast cultures considerable clonal selection of cytogenetically abnormal cells occurred. PMID:3791172

  12. A comparative investigation of DNA strand breaks, sister chromatid exchanges and K-ras gene mutations induced by cadmium salts in cultured human cells

    International Nuclear Information System (INIS)

    Cadmium (Cd) is a toxic heavy metal of continuing occupational and environmental concern with a wide variety of adverse effects. Several studies have shown that cadmium produces DNA strand breaks, DNA-protein cross-links, oxidative DNA damage, chromosomal aberrations, dysregulation of gene expression resulting in enhanced proliferation, depressed apoptosis and/or altered DNA repair. This study was undertaken to investigate the ability of cadmium chloride (CdCl2) and cadmium sulphate (CdSO4) to induce point mutations in codon 12 of the K-ras protooncogene assessed by polymerase chain reaction-single strand conformation polymorphisms (PCR-SSCP) and RFLP-enriched PCR methods. Also their genotoxic effects were analyzed by the comet assay and sister chromatid exchanges test. The human lung fibroblast cell line MRC-5 was used for the experiments. Sister chromatid exchanges assay (SCEs) frequencies were significantly increased in cells exposed to cadmium salts in relation to controls (p < 0.001). Despite the slow increment observed in the three comet parameters considered when cells were treated with cadmium chloride, significant differences between groups were only found in the variable comet moment (CM) (p < 0.005). On the other hand, when cells were exposed to cadmium sulphate, the Kruskal-Wallis test showed highly significant differences between groups for migration, tail moment and comet moment parameters (p < 0.001). Nevertheless, a null or weak point mutation induction in K-ras protooncogene was detected using polymerase chain reaction-low ionic strength-single strand conformation polymorphisms (PCR-LIS-SSCP) and RFLP-enriched PCR methods when cells were treated with cadmium salts. Thus, inorganic cadmium produces genotoxicity in human lung fibroblast MRC-5 cells, in the absence of significant point mutation of the K-ras gene

  13. Characterization of the enhancing effect of caffeine on sister-chromatid exchanges induced by ultraviolet radiation in excision-proficient xeroderma pigmentosum lymphoblastoid cells

    International Nuclear Information System (INIS)

    Cells of some excision-proficient xeroderma pigmentosum (XP) cell lines are highly sensitive to post-UV caffeine treatment in terms of sister-chromatid exchange (SCE) induction as well as cell lethality. In the present study, the authors conducted a detailed investigation of the enhancing effect of caffeine on SCE frequency induced by UV in excision-proficient XP cells, and obtained the following results. (1). Continuous post-UV treatment with 1mM caffeine markedly enhances UV-induced SCEs and such enhanced SCEs occur with similar frequency during either the 1st or the 2nd cell cycle in the presence of caffeine and 5-bromodeoxyuridine (BrdUrd). (2) The high sensitivity of the cells to post-UV caffeine treatment persists for at least 2 days after UV when irradiated cells are held in either the proliferating of the nonproliferating state prior to the addition of BrdUrd. (3) Caffeine exerts its effect on cells in S phase. The most likely explanation for our findings is as follows. In excision-proficient XP cells, the cause of SCE formation such as UV-induced lesions or resulting perturbations of DNA replication persists untill the 2nd round or more of post-UV DNA replication. If caffeine is given as post-UV treatment, such abnormalities may be amplified, resulting in a synergistic increase in SCE frequency. (author). 21 refs.; 4 figs.; 4 tabs

  14. The lethal response to Cdk1 inhibition depends on sister chromatid alignment errors generated by KIF4 and isoform 1 of PRC1.

    Science.gov (United States)

    Voets, Erik; Marsman, Judith; Demmers, Jeroen; Beijersbergen, Roderick; Wolthuis, Rob

    2015-01-01

    Cyclin-dependent kinase 1 (Cdk1) is absolutely essential for cell division. Complete ablation of Cdk1 precludes the entry of G2 phase cells into mitosis, and is early embryonic lethal in mice. Dampening Cdk1 activation, by reducing gene expression or upon treatment with cell-permeable Cdk1 inhibitors, is also detrimental for proliferating cells, but has been associated with defects in mitotic progression, and the formation of aneuploid daughter cells. Here, we used a large-scale RNAi screen to identify the human genes that critically determine the cellular toxicity of Cdk1 inhibition. We show that Cdk1 inhibition leads to fatal sister chromatid alignment errors and mitotic arrest in the spindle checkpoint. These problems start early in mitosis and are alleviated by depletion of isoform 1 of PRC1 (PRC1-1), by gene ablation of its binding partner KIF4, or by abrogation of KIF4 motor activity. Our results show that, normally, Cdk1 activity must rise above the level required for mitotic entry. This prevents KIF4-dependent PRC1-1 translocation to astral microtubule tips and safeguards proper chromosome congression. We conclude that cell death in response to Cdk1 inhibitors directly relates to chromosome alignment defects generated by insufficient repression of PRC1-1 and KIF4 during prometaphase. PMID:26423135

  15. Repairability during G 1 phase of inducting lesions of sister chromatid exchange produced by mitomycin C in salivary gland cells of mice In Vivo

    International Nuclear Information System (INIS)

    The repairability of the injuries that lead to the formation of sister chromatid exchange (SCE) produced by mitomycin C (MMC) with a dose of 2.1 mg/g in vivo, during the G 1 phase in the first cycle of cellular division (before the incorporation of BrdU [5-bromo-2 deoxyurine] to the DNA), as well as during the G 1 phase of the second cycle of cellular division (after the incorporation of BrdU) were analyzed. A 35.1% decrease in the frequency of SCE produced by Mitomycin C was observed, in the early G 1 phase of the first division, with respect to the frequency of SCE induced in the later G 1 phase. When Mitomycin C is given to cells whose DNA is substituted with BrdU in only one of the chain's filaments such decrease is not observed. The results suggest that the injuries caused by MMC, which give place to the SCE, in cells of the salivary glands of the mouse in vivo, are partially repaired only when induced in DNA which has not been substituted with BrdU. (Author)

  16. Relationship of enhanced survival during confluent holding recovery in ultraviolet-irradiated human and mouse cells to chromosome aberrations, sister chromatid exchanges, and DNA repair

    International Nuclear Information System (INIS)

    The relationship among cellular recovery from ultraviolet light (UVL) damage, cytogenetic changes, and DNA repair was studied in density-inhibited cultures of mouse 10T1/2 cells and human diploid fibroblasts. Both cell types showed similar UVL sensitivites to cell killing and a similar enhancement in survival when subculture to a low density was delayed for 24-48 hr after irradiation (potential lethal damage repair). However, excision repair as measured by the loss of endonuclease-sensitive sites was biphasic and much slower in the mouse cells: 30% were removed in the first 24 hr compared with 60% removed in the first 5 hr in the human cells. More than five times as many excision-induced DNA strand breaks as measured by alkaline elution were detected in the human as compared with the mouse cells. DNA-protein crosslinks were removed with a T 1/2 of 30 hr after 10 J/m2 UVL. UVL induced few chromosomal aberrations in the human cells as compared with mouse cells. The frequency of induced sister chromatid exchanges and the pattern of their decline during recovery were similar in both cell types; the kinetics of this decline was similar to that observed for the removal of DNA-protein crosslinks, and slowly removed endonuclease-sensitive sites. Chromosome aberrations, however, correlated with rapidly removed endo sites and DNA strand breaks and appeared to reflect the number of residual pyrimidine dimers in DNA at the time of its replication

  17. Analysis of chromosomal aberrations, sister-chromatid exchanges and micronuclei in peripheral lymphocytes of pharmacists before and after working with cytostatic drugs.

    Science.gov (United States)

    Roth, S; Norppa, H; Järventaus, H; Kyyrönen, P; Ahonen, M; Lehtomäki, J; Sainio, H; Sorsa, M

    1994-12-01

    The frequencies of chromosome aberrations, SCEs and micronuclei (cytokinesis-block method) in blood lymphocytes were compared among six nonsmoking female pharmacists before and after 1 year of working with cytostatic drugs. All possible precautions were taken to avoid exposure to cytostatics, including proper protective clothing and a monitored, negative-pressured working environment with vertical laminar flow cabinet. As referents, an age-matched group of six nonsmoking female hospital workers not dealing with cytostatics was simultaneously sampled twice with the same time interval. The pharmacists showed a marginally higher mean frequency of SCEs/cell (6.3; P = 0.049) after the working period than 1 year earlier (5.8). On the other hand, the referents, with no obvious exposure, had a higher mean number of cells with chromatid-type aberrations, gaps excluded, in the second sampling (2.0%; P = 0.048) than in the first one (0.5%). In addition, a slight (P = 0.055) trend towards a higher frequency of micronucleated binucleate cells was observed in the second sampling for both the exposed and control subjects. As such findings suggest technical variation in the cytogenetic parameters, the small difference observed in SCEs for the pharmacists between the two samplings was probably not related to the cytostatics exposure. No statistically significant differences were observed for any of the cytogenetic parameters in comparisons between the pharmacists and the referents. The findings suggest that caution should be exercised in comparing results obtained from two different samplings in prospective cytogenetic studies. PMID:7527908

  18. Genotoxic effects of a particular mixture of acetamiprid and alpha-cypermethrin on chromosome aberration, sister chromatid exchange, and micronucleus formation in human peripheral blood lymphocytes.

    Science.gov (United States)

    Kocaman, Ayşe Yavuz; Topaktaş, Mehmet

    2010-04-01

    The genotoxic effects of a particular mixture of acetamiprid (Acm, neonicotinoid insecticide) and alpha-cypermethrin (alpha-cyp, pyrethroid insecticide) on human peripheral lymphocytes were examined in vitro by chromosomal aberrations (CAs), sister chromatid exchange (SCE), and micronucleus (MN) tests. The human peripheral lymphocytes were treated with 12.5 + 2.5, 15 + 5, 17.5 + 7.5, and 20 + 10 microg/mL of Acm+alpha-cyp, respectively, for 24 and 48 h. The mixture of Acm+alpha-cyp induced the CAs and SCEs at all concentrations and treatment times when compared with both the control and solvent control and these increases were concentration-dependent in both treatment times. MN formation was significantly induced at 12.5 + 2.5, 15 + 5, 17.5 + 7.5, microg/mL of Acm+alpha-cyp when compared with both controls although these increases were not concentration-dependent. Binuclear cells could not be detected sufficiently in the highest concentration of the mixture (20 + 10 microg/mL) for both the 24- and 48-h treatment times. Mitotic index (MI), proliferation index (PI) and nuclear division index (NDI) significantly decreased because of the cytotoxic and cytostatic effects of the mixture, at all concentrations for two treatment periods. Significant decreases in MI and PI were concentration dependent at both treatment times. The decrease in NDI was also concentration-dependent at 48-h treatment period. In general, Acm+alpha-cyp inhibited nuclear division more than positive control, mitomycin C (MMC) and showed a higher cytostatic effect than MMC. Furthermore, in this article, the results of combined effects of Acm+alpha-cyp were compared with the results of single effects of Acm or alpha-cyp (Kocaman and Topaktas,2007,2009, respectively). In conclusion, the particular mixture of Acm+alpha-cyp synergistically induced the genotoxicity/cytotoxicity in human peripheral blood lymphocytes.

  19. Evaluation of the persistence in the induction of Sister Chromatid Exchanges (SCE) by alkylating agents; Evaluacion de la persistencia en la induccion de Intercambio en las Cromatidas Hermanas (ICH) por agentes alquilantes

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez R, R.; Huerta V, C.; MOrales R, P.R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2006-07-01

    The persistence in the induction of sister chromatid exchanges (SCE) by the alkylating agents methyl and ethyl-methanesulfonates (MMS and EMS) was evaluated. For it, to groups of mice its were administered a dose of these agents and later its were analyzed the induced SCE's in two periods: early and late. Both agents caused high increments of SCE in the early period and small in the late one; however, the caused lately by EMS was significantly bigger. This late induction of SCE by EMS possibly is associated with an epigenetic change or with the presence of etiladucts in the phosphodiester bonds of the DNA. (Author)

  20. Meiosis-specific cohesin component, Stag3 is essential for maintaining centromere chromatid cohesion, and required for DNA repair and synapsis between homologous chromosomes.

    Directory of Open Access Journals (Sweden)

    Jessica Hopkins

    2014-07-01

    Full Text Available Cohesins are important for chromosome structure and chromosome segregation during mitosis and meiosis. Cohesins are composed of two structural maintenance of chromosomes (SMC1-SMC3 proteins that form a V-shaped heterodimer structure, which is bridged by a α-kleisin protein and a stromal antigen (STAG protein. Previous studies in mouse have shown that there is one SMC1 protein (SMC1β, two α-kleisins (RAD21L and REC8 and one STAG protein (STAG3 that are meiosis-specific. During meiosis, homologous chromosomes must recombine with one another in the context of a tripartite structure known as the synaptonemal complex (SC. From interaction studies, it has been shown that there are at least four meiosis-specific forms of cohesin, which together with the mitotic cohesin complex, are lateral components of the SC. STAG3 is the only meiosis-specific subunit that is represented within all four meiosis-specific cohesin complexes. In Stag3 mutant germ cells, the protein level of other meiosis-specific cohesin subunits (SMC1β, RAD21L and REC8 is reduced, and their localization to chromosome axes is disrupted. In contrast, the mitotic cohesin complex remains intact and localizes robustly to the meiotic chromosome axes. The instability of meiosis-specific cohesins observed in Stag3 mutants results in aberrant DNA repair processes, and disruption of synapsis between homologous chromosomes. Furthermore, mutation of Stag3 results in perturbation of pericentromeric heterochromatin clustering, and disruption of centromere cohesion between sister chromatids during meiotic prophase. These defects result in early prophase I arrest and apoptosis in both male and female germ cells. The meiotic defects observed in Stag3 mutants are more severe when compared to single mutants for Smc1β, Rec8 and Rad21l, however they are not as severe as the Rec8, Rad21l double mutants. Taken together, our study demonstrates that STAG3 is required for the stability of all meiosis

  1. Evidence that cyclophosphamide can to induce exchanges in the sister chromatids (ICH) through secondary injuries; Evidencia de que la ciclofosfamida puede inducir intercambios en las cromatidas hermanas (ICH) a traves de lesiones secundarias

    Energy Technology Data Exchange (ETDEWEB)

    Morales R, P.; Rodriguez R, R. [Instituto Nacional de Investigaciones nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    1997-07-01

    By means of the use of destination protocol of ICH inductive injuries (DLI-ICH), it was studied if interchanges in the sister chromatids (ICH) induced by cyclophosphamide (CP), in the second post-treatment division (ICH-2) are produced by secondary injuries or by fresh injuries. For discard between these possibilities it was administered CP at different periods before of the first post-treatment division, taking as reference the administered time for high dose of bromodeoxyuridine (BrdU ) which was approximately at the beginning of this division. The ICH frequencies that occur in the first, the second and the third synthesis stages (S) were determined. It was observed that when the administered CP was four hours before BrdU , the ICH frequencies of the second and the third S were reduced. The frequency of the first ICH increased lightly in relation to those of the normal protocol (0.5 h before BrdU ) and that the supplying of CP six hours before caused almost a total reduction of ICH of second and third S and an important increment of ICH of first S.This was interpreted as evidence that the ICH-2 are product of secondary injuries. (Author)

  2. Role of oxidative stress and intracellular calcium in nickel carbonate hydroxide-induced sister-chromatid exchange, and alterations in replication index and mitotic index in cultured human peripheral blood lymphocytes

    Energy Technology Data Exchange (ETDEWEB)

    M' Bemba-Meka, Prosper [Universite de Montreal, Human Toxicology Research Group (TOXHUM), Department of Environmental and Occupational Health, Main Station, P.O. Box 6128, Montreal, QC (Canada); University of Louisville, Department of Pharmacology and Toxicology, Center for Genetics and Molecular Medicine, Louisville, KY (United States); Lemieux, Nicole [Universite de Montreal, Department of Pathology and Cellular Biology, Faculty of Medicine, Main Station, P.O. Box 6128, Montreal, QC (Canada); Chakrabarti, Saroj K. [Universite de Montreal, Human Toxicology Research Group (TOXHUM), Department of Environmental and Occupational Health, Main Station, P.O. Box 6128, Montreal, QC (Canada)

    2007-02-15

    Human peripheral lymphocytes from whole blood cultures were exposed to either soluble form of nickel carbonate hydroxide (NiCH) (0-60 {mu}M), or of nickel subsulfide (Ni{sub 3}S{sub 2}) (0-120 {mu}M), or of nickel oxide (NiO) (0-120 {mu}M), or nickel sulfate (NiSO{sub 4}) (0-120 {mu}M) for a short duration of 2 h. The treatments occurred 46 h after the beginning of the cultures. The cultures were harvested after a total incubation of 72 h, and sister-chromatid exchange (SCE), replication index (RI), and mitotic index (MI) were measured for each nickel compound. The soluble form of NiCH at 30 {mu}M but those of Ni{sub 3}S{sub 2} and NiO at 120 {mu}M produced significant increase in the SCE per cell compared to the control value, whereas NiSO{sub 4} failed to produce any such significant increase. Except NiSO{sub 4}, the soluble forms of NiCH, Ni{sub 3}S{sub 2}, and NiO produced significant cell-cycle delay (as measured by the inhibition of RI) as well as significant inhibition of the MI at respective similar concentrations as mentioned above. Pretreatment of human blood lymphocytes with catalase (H{sub 2}O{sub 2} scavenger), or superoxide dismutase (superoxide anion scavenger), or dimethylthiourea (hydroxyl radical scavenger), or deferoxamine (iron chelator), or N-acetylcysteine (general antioxidant) inhibited NiCH-induced SCE, and changes in RI and MI. This suggests the participation of oxidative stress involving H{sub 2}O{sub 2}, the superoxide anion radical, the hydroxyl radical, and iron in the NiCH-induced genotoxic responses. Cotreatment of NiCH with either verapamil (inhibitor of intracellular calcium ion ([Ca{sup 2+}]{sub i}) movement through plasma membranes), or dantrolene (inhibitor of [Ca{sup 2+}]{sub i} release from sarcoplasmic reticulum), or BAPTA (Ca{sup 2+} chelator) also inhibited the NiCH-induced responses. These results suggest that [Ca{sup 2+}]{sub i} is also implicated in the genotoxicity of NiCH. Overall these data indicate that various types

  3. Relationship of the demethylation of the DNA with the induction of the sister chromatid exchanges (SCE) In vivo; Relacion de la desmetilacion del ADN con la induccion de intercambios en las cromatidas hermanas (ICH) In vivo

    Energy Technology Data Exchange (ETDEWEB)

    Toribio E, E

    2005-07-01

    The methylation of the DNA is an epigenetic modification that has an important paper in the regulation of the functionality of the genome of the organisms. It can be altered by demethylation processes, either natural or experimentally induced. The 5-azacytidine (Aza) is a compound that causes the demethylation of the DNA (dm-DNA), inducing with it, expression genic and increase in the frequency of the Sister Chromatid Exchange (SCE). The SCE is a genotoxicity indicator, caused by diverse mutagens and carcinogen. Since the biological meaning and the formation mechanism of this phenomenon has not been totally illustrious, the exploration of the relation between the dm-DNA and the induction of SCE, it could offer new knowledge to explain those queries. The purpose of this work was to study in cells of the mouse bone marrow In vivo, the effect of the Aza on the induction of SCE, based on two aspects: 1) dose answer and 2) the effectiveness of multiple exhibition. To six groups of three to five animals, they are administered Aza to dose of 5, 10, 15 or 20 mg/Kg of weight; in sharp or multiple form, previously to the bromodeoxyuridine supply and 24 h was sacrificed after this; 2 h after an injection with colchicine. Preparations of those metaphases were made, those which were dyed by means of a technique of fluorescence more Giemsa. It was observed that to sharp low dose, the Aza produced an increment in the frequency of SCE that although small it was proportional and statistically significant. To sharp and multiple high doses, the Aza doesn't cause additional increments of SCE, but if toxicity at cellular level and of individuals. It is concluded that a relationship exists between the dm-DNA and the induction of SCE. It is suggested that the total demethylation of the DNA causes 2 SCE/Cell in cells of the mouse bone marrow, or that the cytotoxicity prevents to evidence a bigger induction. (Author)

  4. Chromatid Painting for Chromosomal Inversion Detection Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose the continued development of a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and...

  5. Chromatid Painting for Chromosomal Inversion Detection Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and inversions) have profound genetic...

  6. The nature of high frequency sister chromatid exchange cells (HFCs).

    Science.gov (United States)

    Ponzanelli, I; Landi, S; Bernacchi, F; Barale, R

    1997-09-01

    We employed the three-way differential staining technique (TWD), which allows SCEs to be distinguished on a per generation basis by scoring third metaphases (M3), in order to study the spontaneous levels of SCEs in normal and high frequency cells (HFCs) that occurred in the first (S1), second (S2) and third (S3) S phases. Fifty one of 900 lymphocytes from 37 healthy donors were defined as HFCs by calculating the 95th percentile of the distribution of SCEs in S1 + S2. 'Normal' cells presented almost the same number of SCEs after the first, second and third cell cycles (SCE averages of 2.43, 2.04 and 3.53 respectively). In contrast, HFCs showed a higher SCE count in S1, which decreased rapidly through the cycles and reached baseline level at S3 (SCE averages of 7.18, 4.29 and 3.45 respectively). This would suggest that the lesions responsible for the higher SCE frequency in HFCs were effectively removed after two cell cycles and strongly support the hypothesis that HFCs are lymphocytes which accumulate higher levels of DNA lesions through time. PMID:9379910

  7. Review of the international symposium, sister chromatid exchanges: twenty-five years of experimental research

    Energy Technology Data Exchange (ETDEWEB)

    Tice, R.R.; Lambert, B.; Morimoto, Kanehisa; Hollaender, A.

    1983-01-01

    The purpose of this symposium was to honor initial research at Brookhaven by bringing internationally recognized leaders in the fields of genetics, cytogenetics, carcinogenesis, mutagenesis, radiation biology, toxicology, and environmental health together into an open forum to present and discuss: (1) current knowledge of the induction and formation of SCEs and their relationship to other biological endpoints, including carcinogenesis, mutagenesis, transformation, clastogenesis, DNA damage and repair, and cellular toxicity; (2) the optimal strategies for the utilization of SCEs in genetic toxicology testing schemes involving in vitro and in vivo exposure situations; (3) the most valid statistical methods for analyzing SCE data obtained from cells in culture, from cells in intact organisms, and from cells in humans; (4) the relevance of SCEs as an indicator of human disease states, both inherited and acquired, and of progress in disease treatment; and (5) the use of SCEs as an indicator of human exposure to genotoxic agents and their relevance as a prognosticator of future adverse health outcomes. This report summarizes the presentations. 7 references. (ACR)

  8. Rad54 and DNA Ligase IV cooperate to maintain mammalian chromatid stability

    OpenAIRE

    Mills, Kevin D.; Ferguson, David O.; Essers, Jeroen; Eckersdorff, Mark; Kanaar, Roland; Alt, Frederick W.

    2004-01-01

    Nonhomologous end joining (NHEJ) and homologous recombination (HR) represent the two major pathways of DNA double-strand break (DSB) repair in eukaryotic cells. NHEJ repairs DSBs by ligation of cognate broken ends irrespective of homologous flanking sequences, whereas HR repairs DSBs using an undamaged homologous template. Although both NHEJ and HR have been clearly implicated in the maintenance of genome stability, how these apparently independent and mechanistically distinct pathways are co...

  9. PICH promotes sister chromatid disjunction and co-operates with topoisomerase II in mitosis

    DEFF Research Database (Denmark)

    Nielsen, Christian Thomas Friberg; Huttner, Diana; Bizard, Anna H;

    2015-01-01

    PICH is a SNF2 family DNA translocase that binds to ultra-fine DNA bridges (UFBs) in mitosis. Numerous roles for PICH have been proposed from protein depletion experiments, but a consensus has failed to emerge. Here, we report that deletion of PICH in avian cells causes chromosome structural......-193-treated cells. We propose that PICH and Topo II cooperate to prevent chromosome missegregation events in mitosis....

  10. Effect of cysteamine on sister chromatid exchange (SCE) induction by gamma rays

    International Nuclear Information System (INIS)

    The effect of different doses of cysteamine (3, 15 and 150 μg/g bw) on gamma ray-induced SCE was evaluated and compared with the responses obtained with regard to frequency of chromosomal aberrations, frequency of proliferating cells and the rate of cellular proliferating kinetics in mouse bone marrow cells in vivo. Groups of mice were either irradiated, treated with cysteamine and irradiated, only treated with cysteamine or left without treatment for determination of these parameters. The intraperitoneal administration of cysteamine preceding 1 Gy of gamma ray exposure, produces a dose dependent radioprotection on SCE-induction obtaining the greatest effect with 150 μg/g bw. However, this effect was not observed in the mitotic index nor in the average generation time. Chromosomic aberrations in animals irradiated after treatment with cysteamine were also detected. It was not observed any citotoxic or genotoxic effect produced by cysteamine per se. The results suggest that, under the experimental conditions of this study, the SCE are caused by free radicals produced by gamma radiation; not so, the additional damage indexes measured. (author)

  11. DNA-PK-dependent RPA2 hyperphosphorylation facilitates DNA repair and suppresses sister chromatid exchange.

    Directory of Open Access Journals (Sweden)

    Hungjiun Liaw

    Full Text Available Hyperphosphorylation of RPA2 at serine 4 and serine 8 (S4, S8 has been used as a marker for activation of the DNA damage response. What types of DNA lesions cause RPA2 hyperphosphorylation, which kinase(s are responsible for them, and what is the biological outcome of these phosphorylations, however, have not been fully investigated. In this study we demonstrate that RPA2 hyperphosphorylation occurs primarily in response to genotoxic stresses that cause high levels of DNA double-strand breaks (DSBs and that the DNA-dependent protein kinase complex (DNA-PK is responsible for the modifications in vivo. Alteration of S4, S8 of RPA2 to alanines, which prevent phosphorylations at these sites, caused increased mitotic entry with concomitant increases in RAD51 foci and homologous recombination. Taken together, our results demonstrate that RPA2 hyperphosphorylation by DNA-PK in response to DSBs blocks unscheduled homologous recombination and delays mitotic entry. This pathway thus permits cells to repair DNA damage properly and increase cell viability.

  12. Fanconi anaemia proteins are associated with sister chromatid bridging in mitosis

    DEFF Research Database (Denmark)

    Ying, Songmin; Hickson, Ian D

    2011-01-01

    The maintenance of genome stability is critical for the suppression of cancer and premature ageing. The maintenance of the human genome requires hundreds of proteins involved in DNA repair, DNA replication, chromosome segregation and cell cycle checkpoint responses. A number of genetic disorders...... that specifically occur during chromosome segregation in mitosis. The BS protein, BLM, was shown recently to define a novel class of anaphase DNA bridge structures that, in some cases, also contain FA proteins. We will discuss the possible source of these bridges and the role that FA proteins and BLM might play...

  13. Effect of tritiated compounds on sister-chromatid exchanges (SCE) in human lymphocytes in vitro

    International Nuclear Information System (INIS)

    Human lymphocytes treated in vitro with various activities of 3H-TdR and 3H-UdR were cultured to understand the effects of tritium on the cell cycle and the frequency of SCE. The results of these experiments indicated that both tritiated compounds make the frequency of SCE increase and the cell cycle delay. The frequency of SCE increased markedly with activity of 3H. With respect to delaying cell cycle, 3H-UdR was more effective than 3H-TdR. The average frequencies of SCE for 3H-UdR were higher than those for 3H-TdR. With the exception of 3.7 x 103 Bq/mL group and differences between other 3H-UdR groups and corresponding 3H-TdR group were significant (t test, p < 0.01). These results suggest that tritiated compounds may have the effect on the cell proliferating rate. The cell proliferating rate index (PRI) seems to be related with the frequency of SCE: the higher the frequency of SCE, the lower the PRI is

  14. Review of the international symposium, sister chromatid exchanges: twenty-five years of experimental research

    International Nuclear Information System (INIS)

    The purpose of this symposium was to honor initial research at Brookhaven by bringing internationally recognized leaders in the fields of genetics, cytogenetics, carcinogenesis, mutagenesis, radiation biology, toxicology, and environmental health together into an open forum to present and discuss: (1) current knowledge of the induction and formation of SCEs and their relationship to other biological endpoints, including carcinogenesis, mutagenesis, transformation, clastogenesis, DNA damage and repair, and cellular toxicity; (2) the optimal strategies for the utilization of SCEs in genetic toxicology testing schemes involving in vitro and in vivo exposure situations; (3) the most valid statistical methods for analyzing SCE data obtained from cells in culture, from cells in intact organisms, and from cells in humans; (4) the relevance of SCEs as an indicator of human disease states, both inherited and acquired, and of progress in disease treatment; and (5) the use of SCEs as an indicator of human exposure to genotoxic agents and their relevance as a prognosticator of future adverse health outcomes. This report summarizes the presentations. 7 references

  15. Sgo1 is required for co-segregation of sister chromatids during achiasmate meiosis I

    OpenAIRE

    Dudas, Andrej; Ahmad, Shazia; Gregan, Juraj

    2011-01-01

    The reduction of chromosome number during meiosis is achieved by two successive rounds of chromosome segregation, called meiosis I and meiosis II. While meiosis II is similar to mitosis in that sister kinetochores are bi-oriented and segregate to opposite poles, recombined homologous chromosomes segregate during the first meiotic division. Formation of chiasmata, mono-orientation of sister kinetochores and protection of centromeric cohesion are three major features of meiosis I chromosomes wh...

  16. 40 CFR 79.65 - In vivo sister chromatid exchange assay.

    Science.gov (United States)

    2010-07-01

    ... peripheral blood lymphocytes, often from rodent species. (b) Definitions. For the purposes of this section, the following definitions apply: C-metaphase means a state of arrested cell growth typically seen... the end of the exposure period and blood lymphocyte cell cultures are prepared from study...

  17. Homologous recombination, sister chromatid cohesion, and chromosome condensation in mammalian meiosis

    NARCIS (Netherlands)

    Eijpe, M.

    2002-01-01

    In the life cycle of sexually reproducing eukaryotes, haploid and diploid generations of cells alternate. Two types of cell division occur in such a life cycle: mitosis and meiosis. They are compared in chapter 1 . Haploid and diploid cells can multiply by mitoses.

  18. The origin recognition complex links replication, sister chromatid cohesion and transcriptional silencing in Saccharomyces cerevisiae

    NARCIS (Netherlands)

    Suter, Bernhard; Tong, Amy; Chang, Michael; Yu, Lisa; Brown, Grant W; Boone, Charles; Rine, Jasper

    2004-01-01

    Mutations in genes encoding the origin recognition complex (ORC) of Saccharomyces cerevisiae affect initiation of DNA replication and transcriptional repression at the silent mating-type loci. To explore the function of ORC in more detail, a screen for genetic interactions was undertaken using large

  19. Correlation between Cell Killing and Initial Chromatid Breaks Measured by PCC in Human Hepatoma Cells Irradiated With γ-rays

    Institute of Scientific and Technical Information of China (English)

    YangJianshe; LiWenjian; GaoQingxiang; ZhaoJing; XiaJingguang; JinXiaodong

    2003-01-01

    Cancer is one of the most seriously lethal disease. Radiobiologists aimed to develop an assay or a combinative assay to predict the radiation response of human cancer. Precise prediction of response to radiation could provide the basis for selecting and designing clinical treatment project.

  20. Cancer-prone syndrome of mosaic variegated aneuploidy and total premature chromatid separation: Report of five infants

    NARCIS (Netherlands)

    M.M. van Haelst (Mieke); J. Hoogeboom (Jeanette); R-J.H. Galjaard (Robert-Jan); W.J. Kleijer (Wim); N.S. den Hollander (Nicolette); R.R. de Krijger (Ronald); R.C.M. Hennekam (Raoul); M.F. Niermeijer (Martinus)

    2001-01-01

    textabstractFive infants (two girls and three boys) from four families all had severe pre- and post-natal growth retardation, profound developmental delay, microcephaly, hypoplasia of the brain with Dandy-Walker complex or other posterior fossa malformations, and developed uncontrollable clonic seiz

  1. Co-segregation of yeast plasmid sisters under monopolin-directed mitosis suggests association of plasmid sisters with sister chromatids

    OpenAIRE

    Liu, Yen-Ting; Ma, Chien-Hui; Jayaram, Makkuni

    2013-01-01

    The 2-micron plasmid, a high copy extrachromosomal element in Saccharomyces cerevisiae, propagates itself with nearly the same stability as the chromosomes of its host. Plasmid stability is conferred by a partitioning system consisting of the plasmid-coded proteins Rep1 and Rep2 and a cis-acting locus STB. Circumstantial evidence suggests that the partitioning system couples plasmid segregation to chromosome segregation during mitosis. However, the coupling mechanism has not been elucidated. ...

  2. Onderzoek naar de inductie van chromosoomafwijkingen en "sister- chromatid exchanges" door acrylamide met Chinese hamster cellen in vitro

    NARCIS (Netherlands)

    Knaap; A.G.A.C.; Bergkamp; W.G.M.; Groot; M.G.

    1986-01-01

    Acrylamide bleek een clastogene werking te hebben in een test op chromosoomafwijkingen met Chinese hamster cellen in vitro vanaf 0,1 mg/ml (1,4 mmol/l), zowel in aan- als afwezigheid van een systeem voor metaboliosche activering (S9). Tevens induceerde acrylamide in deze cellen een significante

  3. Parallel increases in sister chromatid exchanges at base level and with UV treatment in human opiate users

    Energy Technology Data Exchange (ETDEWEB)

    Shafer, D.A.; Falek, A.; Madden, J.J.; Tadayon, F.; Pline, M. (Georgia Mental Health Inst., Atlanta (USA). Human Genetics Research Lab.; Emory Univ., Atlanta, GA (USA). Dept. of Psychiatry); Bokos, P.J. (Interventions, Chicago, IL (USA)); Kuehnle, J.C.; Mendelson, J. (McLean Hospital, Belmont, MA (USA). Alcohol and Drug Abuse Research Center)

    1983-04-01

    The SCE base level frequency and SCE levels induced by far-UV (254 nm) treatment of cells in early G/sub 1/ and early S phases of the cell cycle were significantly higher in leukocytes from heroin addicts as compared to controls. The increased SCE levels in addicts was greatest at base level and smallest after UV irradiation of cells in S phase. These results corrobate and extend our previous findings of increased chromosome damage and reduced DNA-repair synthesis in heroin users. Since opiates do not directly damage DNA, the elevated cytogenetic effects associated with opiate use probably arise from secondary promotional effects related to opiate-mediated alterations in leukocyte metabolism.

  4. 12. Chromosomal aberrations and sister chromatid exchanges in the symptomatic individuals exposed to arsenic through drinking water in West Bengal, India

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@In the seven districts of West Bengal, India arsenic in ground water has been found to be above the permissible limit. The concentrations of arsenic is ranging from 200-800 (g/l according to latest reports. More than 200,000 people have already shown different types of arsenical skin lesions in these seven districts of West Bengal. It has been regarded as the biggest arsenic calamity in the world. However, there is

  5. The lethal response to Cdk1 inhibition depends on sister chromatid alignment errors generated by KIF4 and isoform 1 of PRC1

    NARCIS (Netherlands)

    E. Voets (Erik); J. Marsman (Judith); J.A.A. Demmers (Jeroen); R.L. Beijersbergen (Roderick); R. Wolthuis (Rob)

    2015-01-01

    textabstractCyclin-dependent kinase 1 (Cdk1) is absolutely essential for cell division. Complete ablation of Cdk1 precludes the entry of G2 phase cells into mitosis, and is early embryonic lethal in mice. Dampening Cdk1 activation, by reducing gene expression or upon treatment with cell-permeable Cd

  6. Rmi1, a member of the Sgs1–Top3 complex in budding yeast, contributes to sister chromatid cohesion

    OpenAIRE

    Lai, Mong Sing; Seki, Masayuki; Ui, Ayako; Enomoto, Takemi

    2007-01-01

    The Saccharomyces cerevisiae RecQ-mediated genome instability (Rmi1) protein was recently identified as the third member of the slow growth suppressor 1–DNA topoisomerase III (Sgs1–Top3) complex, which is required for maintaining genomic stability. Here, we show that cells lacking RMI1 have a mitotic delay, which is partly dependent on the spindle checkpoint, and are sensitive to the microtubule depolymerizing agent benomyl. We show that rmi1 and top3 single mutants are defective in sister ch...

  7. Yeast Interacting Proteins Database: YCL029C, YER016W [Yeast Interacting Proteins Database

    Lifescience Database Archive (English)

    Full Text Available rotubules and kinetochore, involved in sister chromatid separation; essential in polyploid cells but not in ...le-associated protein, component of the interface between microtubules and kinetochore, involved in sister chromatid separation

  8. Monitoring the exposure of rats to 2-acetylaminofluorene by the estimation of mutagenic activity in excreta, sister-chromatid exchanges in peripheral blood cells and DNA adducts in peripheral blood, liver and spleen

    NARCIS (Netherlands)

    Willems, M.I.; Raat, W.K.de; Baan, R.A.; Wilmer, J.W.G.M.; Lansbergen, M.J.; Lohman, P.H.M.

    1987-01-01

    The sensitivity of various methods suitable for biomonitoring the exposure to genotoxicants was compared in an animal model. The results were related to the presence of genotoxic effects in the target organ. Groups of male Wistar rats were given one oral dose of 0, 0.1, 1, 10 or 200 mg 2-acetylamino

  9. Suv4-20h2 mediates chromatin compaction and is important for cohesin recruitment to heterochromatin

    OpenAIRE

    Hahn, Matthias; Dambacher, Silvia; Dulev, Stanimir; Kuznetsova, Anastasia Yurievna; Eck, Simon; Wörz, Stefan; Sadic, Dennis; Schulte, Maike; Mallm, Jan-Philipp; Maiser, Andreas; Debs, Pierre; von Melchner, Harald; Leonhardt, Heinrich; Schermelleh, Lothar; Rohr, Karl

    2013-01-01

    Cohesin is essential to chromatid cohesion during mitosis. Mitotic association between sister chromatids depends on cohesin recruitment to pericentric heterochromatin, but the mechanism in mammalian cells is unknown. Here, Schotta and colleagues show that heterochromatin-associated histone methyltransferase Suv4-20h2 interacts with cohesin. Suv4-20h2-deficient cells have strongly reduced cohesin levels at pericentric heterochromatin, resulting in reduced sister chromatid cohesion. This study ...

  10. Characterization of muntjac DNA

    International Nuclear Information System (INIS)

    Sister chromatid exchange (SCE) in muntjac chromosomes is generally proportional to the chromosomal DNA content, but the SCE frequency is reduced in the heterochromatic neck region of the X chromosome. The physical properties of muntjac DNA and the kinetics of repair of UV damage in muntjac heterochromatin and euchromatin were examined and compared with the distribution of sister chromatid exchange

  11. Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1B and SMC3

    NARCIS (Netherlands)

    Eijpe, M.; Offenberg, H.H.; Jessberger, R.; Revenkova, E.; Heyting, C.

    2003-01-01

    In meiotic prophase, the sister chromatids of each chromosome develop a common axial element (AE) that is integrated into the synaptonemal complex (SC). We analyzed the incorporation of sister chromatid cohesion proteins (cohesins) and other AE components into AEs. Meiotic cohesin REC8 appeared shor

  12. Characterization of muntjac DNA

    Energy Technology Data Exchange (ETDEWEB)

    Davis, R.C.

    1981-05-27

    Sister chromatid exchange (SCE) in muntjac chromosomes is generally proportional to the chromosomal DNA content, but the SCE frequency is reduced in the heterochromatic neck region of the X chromosome. The physical properties of muntjac DNA and the kinetics of repair of UV damage in muntjac heterochromatin and euchromatin were examined and compared with the distribution of sister chromatid exchange.

  13. Effects of up-regulation of separase/esp1 on tumor chromatid separation and construction of a conditional expression vector%Separase上调对肿瘤细胞染色体分离作用的研究及条件表达载体的构建

    Institute of Scientific and Technical Information of China (English)

    由莉越; 刘昕

    2005-01-01

    目的研究esp1在肺腺癌细胞株spc细胞中对染色体分离的作用,为肿瘤的基因治疗探索新的方法.方法将已有的含esp1基因的EGFP-N1质粒转染spc细胞,检测其转染效率及对染色体分裂相的影响.同时构建能依赖四环素调控的含有esp1基因的pTRE-d2EGFP质粒载体.结果表达载体EGFP-N1-esp1转染成功,染色体异常分裂相减少.表达载体pTRE-d2EGFP-esp1构建成功.结论 esp1的上调表达对于肿瘤的异常染色体分裂相有一定的抑制作用,对于肿瘤治疗有潜在的应用价值.

  14. {beta} -carotene effect the induction of the sister chromatid exchanges (ICH) by gamma radiation in mouse radiosensibilized osseous marrow cells In vivo; Efecto del {beta}- caroteno la induccion de intercambios en las cromatidas hermanas (ICH) por radiacion gamma en celulas radiosensibilizadas de la medula osea de raton In vivo

    Energy Technology Data Exchange (ETDEWEB)

    Morales R, P.; Cruz V, V.L. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico). Dept. de Biologia

    1997-07-01

    The effect of {beta}- carotene over the ICH radioinduction in radiosensibilized with BrdU osseous marrow cells of mouse was determined In vivo. The treatment with 50 {mu}g {beta} carotene per se induces a significant increment in the ICH frequency and the pre or post-treatment with the same dose causes an additive effect in the ICH frequency produced by 0.62 Gy of gamma radiation. This implies that {beta}- carotene does not have radioprotective activity, under conditions which was developed this experiment. (Author)

  15. Experiment list: SRX140359 [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available tioning. Involved in sister chromatid cohesion. Associat...ylation. Can dimerize, mediating long-range chromatin looping. When bound to chromatin, provides an anchor point for nucleosomes posi

  16. Chiasmatic and achiasmatic inverted meiosis of plants with holocentric chromosomes.

    Science.gov (United States)

    Cabral, Gabriela; Marques, André; Schubert, Veit; Pedrosa-Harand, Andrea; Schlögelhofer, Peter

    2014-01-01

    Meiosis is a specialized cell division in sexually reproducing organisms before gamete formation. Following DNA replication, the canonical sequence in species with monocentric chromosomes is characterized by reductional segregation of homologous chromosomes during the first and equational segregation of sister chromatids during the second meiotic division. Species with holocentric chromosomes employ specific adaptations to ensure regular disjunction during meiosis. Here we present the analysis of two closely related plant species with holocentric chromosomes that display an inversion of the canonical meiotic sequence, with the equational division preceding the reductional. In-depth analysis of the meiotic divisions of Rhynchospora pubera and R. tenuis reveals that during meiosis I sister chromatids are bi-oriented, display amphitelic attachment to the spindle and are subsequently separated. During prophase II, chromatids are connected by thin chromatin threads that appear instrumental for the regular disjunction of homologous non-sister chromatids in meiosis II. PMID:25295686

  17. Sisters dancing in meiosis

    OpenAIRE

    Baarends, Willy; Mercier, Raphael

    2010-01-01

    The EMBO Conference on Meiosis held last September highlighted the dynamic aspects of this process, including the variability of hotspots for break formation, switches between partners during repair and the dynamics of sister chromatid cohesion.

  18. INDUCTION OF DNA STRAND BREAKS BY TRIHALOMETHANES IN PRIMARY HUMAN LUNG EPITHELIAL CELLS

    Science.gov (United States)

    Abstract Trihalomethanes (TEMs) are disinfection by-products and suspected human carcinogens present in chlorinated drinking water. Previous studies have shown that many THMs induce sister chromatid exchanges and DNA strand breaks in human peripheral blood lymphocyte...

  19. Age-related aneuploidy through cohesion exhaustion

    OpenAIRE

    Jessberger, Rolf

    2012-01-01

    Pregnancy in older women is problematic, as oocytes are particularly prone to chromosome missegregation, and aneuploidy increases with age. Sister chromatid cohesion is weakened or lost with age, having a major impact in age-dependent aneuploidy, as discussed here.

  20. Meiotic recombination in normal and cloned bulls and their offspring

    Science.gov (United States)

    Homologous chromosome pairing and recombination are essential components of meiosis and sexual reproduction. The reshuffling of genetic material through breakage and reunion of chromatids ensure proper segregation of homologous chromosomes in reduction division and genetic diversity in the progeny....

  1. Disease: H00914 [KEGG MEDICUS

    Lifescience Database Archive (English)

    Full Text Available H00914 Warsaw breakage syndrome Warsaw breakage syndrome is a cohesinopathy characterized by cellular defect... features of Fanconi anemia (chromosomal breakage) and Roberts syndrome (sister chromatid cohesion defects

  2. Kinetochore orientation during meiosis is controlled by Aurora B and the monopolin complex.

    OpenAIRE

    Monje-Casas, Fernando; Prabhu, Vineet R.; Lee, Brian H.; Boselli, Monica; Amon, Angelika

    2007-01-01

    Kinetochores of sister chromatids attach to microtubules emanating from the same pole (co-orientation) during meiosis I and to microtubules emanating from opposite poles (bi-orientation) during meiosis II. We find that the Aurora B kinase Ipl1 regulates kinetochore - microtubule attachment during both meiotic divisions and that a complex known as the monopolin complex ensures that the protein kinase co-orients sister chromatids during meiosis I. Furthermore, the defining of conditions suffici...

  3. Sister kinetochores are mechanically fused during meiosis I in yeast

    OpenAIRE

    Sarangapani, Krishna K.; Duro, Eris; Deng, Yi; de Lima Alves, Flavia; Ye, Qiaozhen; Opoku, Kwaku N.; Ceto, Steven; Rappsilber, Juri; Corbett, Kevin D.; Biggins, Sue; Marston, Adèle L.; Asbury, Charles L.

    2014-01-01

    Production of healthy gametes requires a reductional meiosis I division in which replicated sister chromatids co-migrate, rather than separating as in mitosis or meiosis II. Fusion of sister kinetochores during meiosis I may underlie sister chromatid co-migration in diverse organisms, but direct evidence for such fusion has been lacking. Here we studied native kinetochore particles isolated from yeast using laser trapping and quantitative fluorescence microscopy. Meiosis I kinetochores formed...

  4. The Saccharomyces cerevisiae centromere protein Slk19p is required for two successive divisions during meiosis.

    OpenAIRE

    Zeng, X.; Saunders, W S

    2000-01-01

    Meiotic cell division includes two separate and distinct types of chromosome segregation. In the first segregational event the sister chromatids remain attached at the centromere; in the second the chromatids are separated. The factors that control the order of chromosome segregation during meiosis have not yet been identified but are thought to be confined to the centromere region. We showed that the centromere protein Slk19p is required for the proper execution of meiosis in Saccharomyces c...

  5. Human peripheral blood lymphocytes for the analysis of chromosome aberrations in mutagen tests

    International Nuclear Information System (INIS)

    Studies on exposed individuals, and on cultured cells, have shown that the human peripheral blood lymphocyte is an extremely sensitive indicator of both in vivo and in vitro induced chromosome structural change. These changes in chromosome structure offer readily scored morphological evidence of damage to the genetic material. Although problems exist in the extrapolation from in vitro results to the in vivo situation, the lymphocyte offers several advantages as a test system. The types of chromosome damage which can be cytologically distinguished at metaphase can be divided into two main groups: chromosome type and chromatid type. The circulating lymphocyte is in the G/sub 0/ or G/sub 1/ phase of mitosis and exposure to ionising radiations and certain other mutagenic agents during this stage produces chromosome-type damage where the unit of breakage and reunion is the whole chromosome (i.e. both chromatids at the same locus). However, cells exposed to these agents while in the S or G/sub 2/ stages of the cell cycle, after the chromosome has divided into two sister chromatids, yield chromatid-type aberrations and only the single chromatid is involved in breakage or exchange. Other agents (e.g. some of the alkylating agents) will usually produce only chromatid-type aberrations in cells in cycle although the cells are exposed to the mutagen whilst in G/sub 1/

  6. DNA asymmetry in stem cells - immortal or mortal?

    Science.gov (United States)

    Yadlapalli, Swathi; Yamashita, Yukiko M

    2013-09-15

    The immortal strand hypothesis proposes that stem cells retain a template copy of genomic DNA (i.e. an 'immortal strand') to avoid replication-induced mutations. An alternative hypothesis suggests that certain cells segregate sister chromatids non-randomly to transmit distinct epigenetic information. However, this area of research has been highly controversial, with conflicting data even from the same cell types. Moreover, historically, the same term of 'non-random sister chromatid segregation' or 'biased sister chromatid segregation' has been used to indicate distinct biological processes, generating a confusion in the biological significance and potential mechanism of each phenomenon. Here, we discuss the models of non-random sister chromatid segregation, and we explore the strengths and limitations of the various techniques and experimental model systems used to study this question. We also describe our recent study on Drosophila male germline stem cells, where sister chromatids of X and Y chromosomes are segregated non-randomly during cell division. We aim to integrate the existing evidence to speculate on the underlying mechanisms and biological relevance of this long-standing observation on non-random sister chromatid segregation.

  7. Evaluation of radiosensitivity of human tumor cells after irradiation of γ-rays based on G2-chromosome aberrations

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The aim of the present investigation is to determine initial G2-chromosome aberrations and to validate whether the G2-chromosome aberrations can predict the cellular clonogenic survival in human tumor cell lines. Cell lines of human ovary carcinoma cells (HO8910) and human hepatoma cells (HepG2) were irradiated with a range of doses and assessed both for initial G2-chromosome aberrations and for cell survival after γ-irradiation. The initial G2-chromosome aberrations were measured by counting the number of G2-chromatid breaks after irradiation, detected by the premature chromosome condensation technique, and the G2-assay method. Cell survival was documented by a colony formation assay. A linear-quadratic survival curve was observed in both cell lines. The dose-response results show that the numbers of G2-chromatid breaks increase with the increase in dose in the two cell lines. At higher doses (higher than 4 Gy) of irradiation, the number of G2-chromatid breaks for the G2-assay method cannot be determined because too few cells reach mitosis, and hence their detection is difficult. A good correlation is found between the clonogenic survival and the radiation-induced initial G2-chromatid breaks per cell (r=0.9616). The present results suggest that the premature chromosome condensation technique may be useful for determining chromatid breaks in G2 cells, and the number of initial G2-chromatid breaks holds promise for predicting the radiosensitivity of tumor cells.

  8. Studies on the mitotic chromosome scaffold of Allium sativum

    Institute of Scientific and Technical Information of China (English)

    ZHAOJIAN; SHAOBOJIN; 等

    1995-01-01

    An argentophilic structure is present in the metaphase chromosomes of garlic(Allium sativum),Cytochemical studies indicate that the main component of the structure is non-histone proteins(NHPs).The results of light and electron microscopic observations reveal that the chromosme NHP scaffold is a network which is composed of fibres and granules and distributed throughout the chromosomes.In the NHP network,there are many condensed regions that are connected by redlatively looser regions.The distribution of the condensed regions varies in individual chromosomes.In some of the chromosomes the condensed regions are lognitudinally situsted in the central part of a chromatid while in others these regions appear as coillike transverse bands.At early metaphase.scaffolds of the sister chromatids of a chromosome are linked to each other in the centromeric region,meanwhile,they are connected by scafold materials along the whole length of the chromosome.At late metaphase,however,the connective scaffold materials between the two sister chromatids disappear gradually and the chromatids begin to separate from one another at their ends.but the chromatids are linked together in the centromeric region until anaphase.This connection seems to be related to the special structure of the NHP scaffold formed in the centromeric region.The morphological features and dynamic changes of the chromosome scaffold are discussed.

  9. Isolation and evaluation of cytogenetic effect of Brahmi saponins on cultured human lymphocytes exposed in vitro.

    Science.gov (United States)

    Kalachaveedu, Mangathayaru; Papacchan, Sunu; Sanyal, Sudip; Koshy, Teena; Telapolu, Srivani

    2015-01-01

    Major saponins of Brahmi (Bacopa monniera, Fam: Scrophulariaceae) - bacosides A and B - were isolated from the total methanol extract and characterised based on melting point, TLC, IR, (1)H NMR and (13)C NMR. They were evaluated for their in vitro cytogenetic effects on human peripheral blood lymphocytes by chromosomal aberration (CA) assay and sister chromatid exchange (SCE) assay. The frequency of chromatid type aberrations and reciprocal interchanges between sister chromatids in the treated cells was scored in comparison to the untreated control. At 30 μg/mL dose, bacoside A showed a statistically significant increase in the frequency of both CA and SCE and bacoside B showed an increase only in SCE. Our report of the genotoxicity of the saponins is significant in view of the reports of anticancer activity of Brahmi extracts.

  10. Effects of radiations on Spirogyra azygospora singh, 1

    International Nuclear Information System (INIS)

    The material Spirogyra azygospora (n = 12: chromosomes polycentric) belonging to the Order Conjugales, was used as an experimental material to study the morphological and cytological effects of gamma-rays. The doses administered range from 2 kR to 130 kR. Even the dose of 130 kR gamma radiation did not prove to be completely lethal to this alga. Among the various cytological effects chromosome and chromatid breaks, chromatid and isochromatid exchanges and ring chromosomes are noteworthy. Chromatid and isochromatid exchanges are reported for the first time in polycentric chromosomes. The results were discussed with those of others who studied the effects of ionizing radiations on the karyology of algae. (author)

  11. In Vivo Cytogenetic Studies on Aspartame

    Directory of Open Access Journals (Sweden)

    Entissar S. AlSuhaibani

    2010-01-01

    Full Text Available Aspartame (a-Laspartyl-L-phenylalanine 1-methylester is a dipeptide low-calorie artificial sweetener that is widely used as a nonnutritive sweetener in foods and drinks. The safety of aspartame and its metabolic breakdown products (phenylalanine, aspartic acid and methanol was investigated in vivo using chromosomal aberration (CA test and sister chromatid exchange (SCE test in the bone marrow cells of mice. Swiss Albino male mice were exposed to aspartame (3.5, 35, 350 mg/kg body weight. Bone marrow cells isolated from femora were analyzed for chromosome aberrations and sister chromatid exchanges. Treatment with aspartame induced dose dependently chromosome aberrations at all concentrations while it did not induce sister chromatid exchanges. On the other hand, aspartame did not decrease the mitotic index (MI. However, statistical analysis of the results show that aspartame is not significantly genotoxic at low concentration.

  12. Mouse bone marrow cytogenetic damage produced by residues of tequila.

    Science.gov (United States)

    Madrigal-Bujaidar, E; Rojas, A; Ramos, A; Rosas, E; Díaz Barriga-Arceo, S

    1990-06-01

    Five concentrations (50-860 mg/kg) of residues obtained after distillation and lyophilization of commercial tequila were injected into mice for evaluation of chromosome aberrations, sister-chromatid exchanges, and proliferation kinetics in mouse bone marrow cells. Appropriate positive and negative controls were included. Our results showed significant dose-related increases of chromosomal aberrations starting at 50 mg/kg and for sister-chromatid exchanges at 430 mg/kg. Cellular proliferation kinetics showed no alterations. With these data we demonstrated that the residues of tequila are genotoxic in vivo.

  13. Genotoxic monitoring of workers at a hazardous waste disposal site in Mexico.

    Science.gov (United States)

    Gonsebatt, M E; Salazar, A M; Montero, R; Díaz Barriga, F; Yáñez, L; Gómez, H; Ostrosky-Wegman, P

    1995-01-01

    Chromosomal aberration and sister chromatid exchange (SCE) frequencies were determined in lymphocytes cultured from 12 high-risk individuals working at a landfill for hazardous waste disposal. Cell proliferation kinetics (CPK) was also determined. Compared with 7 control individuals, no effects were observed with respect to SCE nor on CPK. However, the workers exhibited significantly higher frequencies of chromatid and chromosomal deletions, the magnitude of which was related with exposure time. This study suggests that when high-risk exposure is suspected, determining biomarkers of genotoxic damage (e.g., chromosomal aberrations), is useful for risk assessments. PMID:7621789

  14. In vivo cytogenetic effects of the cooked-food-related mutagens Trp-P-2 and IQ in mouse bone marrow

    Energy Technology Data Exchange (ETDEWEB)

    Minkler, J.L.; Carrano, A.V.

    1984-01-01

    Sister-chromatid exchange and chromosomal aberrations were measured in vivo in mouse bone marrow following intraperitoneal injection of the cooked food mutagens, 3-amino-1-methyl-5H-pyrido(4,3-b)indole (Trp-P-2), and 2-amino-3-methylimidazo(4,5-f)quinoline (IQ). Trp-P-2 produced a significant positive dose response for both endpoints while IQ produced only a weak but significant sister-chromatid exchange response. The relative potency of these two chemicals is similar to that seen in mammalian cells in vitro but opposite to their potency in Salmonella.

  15. Cytogenetic findings in persons living near the Love Canal.

    Science.gov (United States)

    Heath, C W; Nadel, M R; Zack, M M; Chen, A T; Bender, M A; Preston, R J

    1984-03-16

    Cytogenetic analyses were performed on peripheral blood from 46 present or past residents of the area surrounding Love Canal, a former dump site for chemical wastes in Niagara Falls, NY. Participants included 17 persons in whom cytogenetic analyses had been performed in 1980 and 29 persons who had been living in 1978 in seven homes that directly adjoined the canal and in which environmental tests showed elevated levels of chemicals spreading from the canal. Frequencies of chromosomal aberrations and of sister chromatid exchange (SCE) did not differ significantly from control levels. For all participants, cigarette smoking was associated with an increase in sister chromatid exchange frequency.

  16. Using pool noodles to teach mitosis and meiosis.

    Science.gov (United States)

    Locke, John; McDermid, Heather E

    2005-05-01

    Although mitosis and meiosis are fundamental to understanding genetics, students often find them difficult to learn. We suggest using common "pool noodles" as teaching aids to represent chromatids in classroom demonstrations. Students use these noodles to demonstrate the processes of synapsis, segregation, and recombination. Student feedback has been overwhelmingly positive.

  17. Carrier detection in xeroderma pigmentosum

    International Nuclear Information System (INIS)

    We were able to detect clinically normal carriers of xeroderma pigmentosum (XP) genes with coded samples of either peripheral blood lymphocytes or skin fibroblasts, using a cytogenetic assay shown previously to detect individuals with cancer-prone genetic disorders. Metaphase cells of phytohemagglutinin-stimulated T-lymphocytes from eight individuals who are obligate heterozygotes for XP were compared with those from nine normal controls at 1.3, 2.3, and 3.3 h after x-irradiation (58 R) during the G2 phase of the cell cycle. Lymphocytes from the XP heterozygotes had twofold higher frequencies of chromatid breaks or chromatid gaps than normal (P less than 10(-5)) when fixed at 2.3 or 3.3 h after irradiation. Lymphocytes from six XP homozygotes had frequencies of breaks and gaps threefold higher than normal. Skin fibroblasts from an additional obligate XP heterozygote, when fixed approximately 2 h after x-irradiation (68 R), had a twofold higher frequency of chromatid breaks and a fourfold higher frequency of gaps than fibroblasts from a normal control. This frequency of aberrations in cells from the XP heterozygote was approximately half that observed in the XP homozygote. The elevated frequencies of chromatid breaks and gaps after G2 phase x-irradiation may provide the basis of a test for identifying carriers of the XP gene(s) within known XP families

  18. Modified mouse peripheral blood lymphocyte culture system for cytogenetic analysis

    International Nuclear Information System (INIS)

    A detailed methodology is presented for culturing mouse peripheral blood lymphocytes isolated on density gradients and stimulated to divide using either phytohemagglutinin, concanavalin A, or lipopolysaccharide. The techniques described yield more than sufficient numbers of mitotic cells for analyzing sister chromatid exchange, chromosome, aberrations, and micronuclei following in vitro or in vivo exposure to chemicals or radiation

  19. 4. National Congress on Genetics. Memoirs

    International Nuclear Information System (INIS)

    According to INIS coverage were analyzed four free works on Life and Environmental Sciences presented during the Congress which are treating over the effects of external irradiation on animals. Between the main aspects are the sister chromatid exchange, spermatogonia, somatic cells, genotoxicity, DNA, chlorophyll, gamma radiation, bone marrow cells and radiation injuries

  20. Chromonoodles: Jump into the Gene Pool

    Science.gov (United States)

    Farrar, Jennifer; Barnhart, Kelsi

    2011-01-01

    Chromosomes, alleles, chromatids, genotype, phenotype, mitosis, meiosis, fertilization--this vocabulary can be overwhelming, confusing, and difficult for students to tie together. However, since these terms are commonplace in the high school biology classroom, and are the basis for understanding both DNA and heredity, students must understand…

  1. Looping in on Ndc80 - how does a protein loop at the kinetochore control chromosome segregation?

    DEFF Research Database (Denmark)

    Nilsson, Jakob

    2012-01-01

    Segregation of chromosomes during mitosis requires the interaction of dynamic microtubules with the kinetochore, a large protein structure established on the centromere region of sister chromatids. The core microtubule-binding activity of the kinetochore resides in the KMN network, an outer...

  2. Mitotic dynamics

    Institute of Scientific and Technical Information of China (English)

    唐孝威

    1996-01-01

    A new model for mitotic dynamics of eukaryotic cells is proposed. In the kinetochore mo-tor-midzone motor model two kinds of motors, the kinetochore motors and the midzone motors, play important roles in chromosome movement. Using this model the chromosome congression during prometaphase, the chromosome oscillation during metaphase and the chromatid segregation during anaphase are described in a unified way.

  3. Propranolol induced chromosomal aberrations in Chinese hamster ovary cell line

    Directory of Open Access Journals (Sweden)

    Mozhgan Sedigh-Ardekani

    2013-03-01

    Full Text Available Propranolol (PL, a non-selective beta-blocker, is a cardiovascular drug widely used to treat hypertension. The present study was concerned with assessing the cytogenetic effects of this drug on Chinese hamster ovary (CHO cell line. MTT assay was then carried out to determine the cytotoxicity index (IC50 of the drug. The IC50 value of PL was 0.43±0.02 mM. To investigate the clastogenic effects of the drug, chromatid and chromosome breaks and polyploidy in metaphases were analyzed. CHO cells were exposed to different concentrations of the drug (0.1, 0.2, 0.3, 0.4 mM for 24 hours. Considering that PL has liver metabolism, experiments were carried out in the presence and absence of the metabolic activation system (S9 mix. Mitomycin-C and sodium arsenite were used as positive controls. It was observed that in cells treated with different PL concentrations as 0.1, 0.2 and 0.3 mM, the frequency of chromatid and chromosome breaks as well as polyploidy increased when compared with untreated CHO cells. The addition of S9 mix significantly decreased the chromatid breaks, chromosome breaks and polyploidy compared to the treatment of PL alone. It is concluded that, PL causes chromatid and chromosome aberrations in CHO cell line and the metabolic activation system (S9 mix, playing an important role in drug cytotoxicity reduction.

  4. Cytogenetic effects in the bone marrow of rats with long-term domestic revenue 131I

    International Nuclear Information System (INIS)

    Cytogenetic effects in the rats bone marrow after long-term ingestion of 131I were studied. Significant increase of chromosomal aberrations by dicentric aberrations with and without fragments, acentric fragments, atypical chromosomes and polyploidies was found. Chromatid-type aberrations in exposed animals were present at the same level as in the control

  5. Sequence Classification: 890748 [

    Lifescience Database Archive (English)

    Full Text Available TMB Non-TMH TMB TMB TMB Non-TMB >gi|6321802|ref|NP_011878.1| Meiosis-specific protein, involved in maintaini...ng sister chromatid cohesion during meiosis I as well as promoting proper attachmen

  6. Radiogenotoxicological effect of signal nuclide 134Cs on somatic and germ cells

    Institute of Scientific and Technical Information of China (English)

    ZhuShou-Peng; XiaFen; 等

    1997-01-01

    Chromosome at aberation rates in bone marrow cells and micronucleus formation in bone marrow polychromatic erythrocytes both rise with increase in radioactivities of 134Cs,and can be fitted to power functions of radioactivities of 134Cs.In spermatogonia 134Cs mainly induced chromatid breakage,and abnormalities in sperm can also be experessed as power functions of radioactivities of 134 Cs.

  7. Using Pool Noodles to Teach Mitosis and Meiosis

    OpenAIRE

    Locke, John; McDermid, Heather E.

    2005-01-01

    Although mitosis and meiosis are fundamental to understanding genetics, students often find them difficult to learn. We suggest using common “pool noodles” as teaching aids to represent chromatids in classroom demonstrations. Students use these noodles to demonstrate the processes of synapsis, segregation, and recombination. Student feedback has been overwhelmingly positive.

  8. Genotoxicity of the pesticide propoxur and its nitroso derivative, NO-propoxur, on human lymphocytes in vitro.

    Science.gov (United States)

    Gonzalez Cid, M; Loria, D; Matos, E

    1990-09-01

    The aim of this work was to investigate whether the pesticide propoxur and its nitroso derivative nitroso-propoxur increased the frequencies of sister-chromatid exchanges and micronuclei in human lymphocytes in vitro. The results show that both chemicals were genotoxic in the tested system.

  9. Mitotic spindle assembly: May the force be with you

    NARCIS (Netherlands)

    Heesbeen, R.G.H.P. van

    2015-01-01

    The research described in this thesis is focused on multiple pathways required for assembly of a bipolar mitotic spindle. Proper assembly of a bipolar mitotic spindle is essential for the generation of stable kinetochore-microtubule attachments and correct segregation of the sister chromatids. Defec

  10. Yeast Interacting Proteins Database: YLR295C, YDR510W [Yeast Interacting Proteins Database

    Lifescience Database Archive (English)

    Full Text Available 7) Rows with this bait as prey (0) YDR510W SMT3 Ubiquitin-like protein of the SUMO family, conjugated to lys...uitin-like protein of the SUMO family, conjugated to lysine residues of target proteins; regulates chromatid

  11. Cohesin: A Multi-purpose Chromatin Glue

    Institute of Scientific and Technical Information of China (English)

    Laura A. D(i)az-Mart(i)nez; Hongtao Yu

    2009-01-01

    Long thought to be the glue responsible for holding sister chromatids together, cohesin has been found to be stickier than previously thought. Recent discoveries point to cohesin having a role in transcription regulation by mediating long-distance intra-chromosomal interactions.

  12. Phenotypic variability in 49 cases of ESCO2 mutations, including novel missense and codon deletion in the acetyltransferase domain, correlates with ESCO2 expression and establishes the clinical criteria for Roberts syndrome

    DEFF Research Database (Denmark)

    Vega, H; Trainer, A H; Gordillo, M;

    2010-01-01

    Roberts syndrome (RBS) and SC phocomelia are caused by mutations in ESCO2, which codes for an acetyltransferase involved in the regulation of sister chromatid cohesion. Of 26 mutations described to date, only one missense mutation has been reported and all others are predicted to be truncating mu...

  13. Studies on chromosome aberrations induced in human lymphocytes by very low-dose exposure to tritium

    International Nuclear Information System (INIS)

    Assessment of potential hazard from environmental tritium to man becomes very important with increasing the development of nuclear-power industry. However, little data are available as to the determination on the genetic effect of tritium especially at the low levels. The object of the present study is to obtain quantitative data for chromosome aberrations in human lymphocytes, as an indicator for genetic risk estimation, induced by tritium at very low dose levels. Leukocyte cultures of human peripheral blood were chronically exposed for 48h to tritiated water and 3H-thymidine using a wide range of tritium doses, and aberrations in lymphocyte chromosomes at the first metaphases were examined. In the experimental conditions, the types of aberrations induced by radiation emitted from both tritiated water and 3H-thymidine were mostly chromatid types, such as chromatid gaps and deletions. The dose-response relations for chromatid breaks per cell exhibited unusual dose-dependency in both cases. It was demonstrated that at higher dose range the yields of chromatid breaks increased linearly with dose, while those at lower dose range were significantly higher than would be expected by a downward extraporation from the linear relation. Partial-hit or partial-target kinetics events appeared at very low dose exposure. (author)

  14. The cohesin subunit RAD21L functions in meiotic synapsis and exhibits sexual dimorphism in fertility

    NARCIS (Netherlands)

    A. Herrán; C. Gutierréz-Caballero; M. Sáanchez-Martin; T. Hernández; A. Viera; J.L. Barbero; E. de Álava; D.G. de Rooij; J. Ángel Suja; E. Llano; A.M. Pendas

    2011-01-01

    The cohesin complex is a ring-shaped proteinaceous structure that entraps the two sister chromatids after replication until the onset of anaphase when the ring is opened by proteolytic cleavage of its alpha-kleisin subunit (RAD21 at mitosis and REC8 at meiosis) by separase. RAD21L is a recently iden

  15. A new thermosensitive smc-3 allele reveals involvement of cohesin in homologous recombination in C. elegans.

    Directory of Open Access Journals (Sweden)

    Antoine Baudrimont

    Full Text Available The cohesin complex is required for the cohesion of sister chromatids and for correct segregation during mitosis and meiosis. Crossover recombination, together with cohesion, is essential for the disjunction of homologous chromosomes during the first meiotic division. Cohesin has been implicated in facilitating recombinational repair of DNA lesions via the sister chromatid. Here, we made use of a new temperature-sensitive mutation in the Caenorhabditis elegans SMC-3 protein to study the role of cohesin in the repair of DNA double-strand breaks (DSBs and hence in meiotic crossing over. We report that attenuation of cohesin was associated with extensive SPO-11-dependent chromosome fragmentation, which is representative of unrepaired DSBs. We also found that attenuated cohesin likely increased the number of DSBs and eliminated the need of MRE-11 and RAD-50 for DSB formation in C. elegans, which suggests a role for the MRN complex in making cohesin-loaded chromatin susceptible to meiotic DSBs. Notably, in spite of largely intact sister chromatid cohesion, backup DSB repair via the sister chromatid was mostly impaired. We also found that weakened cohesins affected mitotic repair of DSBs by homologous recombination, whereas NHEJ repair was not affected. Our data suggest that recombinational DNA repair makes higher demands on cohesins than does chromosome segregation.

  16. Andrographia paniculata a Miracle Herbs for cancer treatment: In vivo and in vitro studies against Aflatoxin B1 Toxicity

    Directory of Open Access Journals (Sweden)

    Md. Sultan Ahmad

    2014-04-01

    Conclusion: In conclusion A. paniculata extracts significantly reduced the number of aberrant cells and frequencies of aberration per cell at each concentration and duration of exposure in vivo; similarly it reduced chromosomal aberrations and sister chromatid exchanges and replication index was enhanced in vitro that was statistically significant at <0.05 level.

  17. DNA template strand sequencing of single-cells maps genomic rearrangements at high resolution

    NARCIS (Netherlands)

    Falconer, Ester; Hills, Mark; Naumann, Ulrike; Poon, Steven S. S.; Chavez, Elizabeth A.; Sanders, Ashley D.; Zhao, Yongjun; Hirst, Martin; Lansdorp, Peter M.

    2012-01-01

    DNA rearrangements such as sister chromatid exchanges (SCEs) are sensitive indicators of genomic stress and instability, but they are typically masked by single-cell sequencing techniques. We developed Strand-seq to independently sequence parental DNA template strands from single cells, making it po

  18. Meiotic transverse filament proteins: essential for crossing over

    NARCIS (Netherlands)

    Heyting, C.

    2005-01-01

    Meiosis is a specialized set of two nuclear divisions, meiosis I and II, by which a diploid cell produces four haploid daughters. After premeiotic DNA replication, homologous chromosomes pair and recombine, and then disjoin at meiosis I. Subsequently, at meiosis II, the sister chromatids of each chr

  19. Double-strand break repair and G4 DNA stability in Caenorhabditis elegans

    NARCIS (Netherlands)

    Pontier, D.B.

    2010-01-01

    DNA double-strand breaks (DSBs) can be repaired by three canonical repair pathways. Homologous recombination (HR) uses the sister chromatid or homologous chromosome as a template to repair the DSB in an error-free manner. In non-homologous end-joining (NHEJ), the broken ends are ligated with little

  20. DNA damage in the kidney tissue cells of the fish Rhamdia quelen after trophic contamination with aluminum sulfate

    Directory of Open Access Journals (Sweden)

    Tatiane Klingelfus

    2015-01-01

    Full Text Available Abstract Even though aluminum is the third most common element present in the earth's crust, information regarding its toxicity remains scarce. It is known that in certain cases, aluminum is neurotoxic, but its effect in other tissues is unknown. The aim of this work was to analyze the genotoxic potential of aluminum sulfate in kidney tissue of the fish Rhamdia quelen after trophic contamination for 60 days. Sixty four fish were subdivided into the following groups: negative control, 5 mg, 50 mg and 500 mg of aluminum sulfate per kg of fish. Samples of the posterior kidney were taken and prepared to obtain mitotic metaphase, as well as the comet assay. The three types of chromosomal abnormalities (CA found were categorized as chromatid breaks, decondensation of telomeric region, and early separation of sister chromatids. The tests for CA showed that the 5 mg/kg and 50 mg/kg doses of aluminum sulfate had genotoxic potential. Under these treatments, early separation of the sister chromatids was observed more frequently and decondensation of the telomeric region tended to increase in frequency. We suggest that structural changes in the proteins involved in DNA compaction may have led to the decondensation of the telomeric region, making the DNA susceptible to breaks. Moreover, early separation of the sister chromatids may have occurred due to changes in the mobility of chromosomes or proteins that keep the sister chromatids together. The comet assay confirmed the genotoxicity of aluminum sulfate in the kidney tissue of Rhamdia quelen at the three doses of exposure.

  1. Increased risk of cancer in radon-exposed miners with elevated frequency of chromosomal aberrations.

    Science.gov (United States)

    Smerhovsky, Zdenek; Landa, Karel; Rössner, Pavel; Juzova, Dagmar; Brabec, Marek; Zudova, Zdena; Hola, Nora; Zarska, Hana; Nevsimalova, Emilie

    2002-02-15

    In spite of the extensive use of cytogenetic analysis of human peripheral blood lymphocytes in the biomonitoring of exposure to various mutagens and carcinogens, the long-term effects of an increased frequency of chromosomal aberrations in individuals are still uncertain. Few epidemiologic studies have addressed this issue, and a moderate risk of cancer in individuals with an elevated frequency of chromosomal aberrations has been observed. In the present study, we analyzed data on 1323 cytogenetic assays and 225 subjects examined because of occupational exposures to radon (range of exposure from 1.7 to 662.3 working level month (WLM)). Seventy-five subjects were non-smokers. We found 36 cases of cancer in this cohort. Chromatid breaks were the most frequently observed type of aberrations (mean frequency 1.2 per 100 cells), which statistically significantly correlated with radon exposure (Spearman's correlation coefficient R=0.22, P<0.001). Also, the frequency of aberrant cells (median of 2.5%) correlated with radon exposure (Spearman's correlation coefficient R=0.16, P<0.02). Smoking and silicosis were not associated with results of cytogenetic analyses. The Cox regression models, which accounted for the age at time of first cytogenetic assay, radon exposure, and smoking showed strong and statistically significant associations between cancer incidence and frequency of chromatid breaks and frequency of aberrant cells, respectively. A 1% increase in the frequency of aberrant cells was paralleled by a 62% increase in risk of cancer (P<0.000). An increase in frequency of chromatid breaks by 1 per 100 cells was followed by a 99% increase in risk of cancer (P<0.000). We obtained similar results when we analyzed the incidence of lung cancer and the incidence other than lung cancer separately. Contrary to frequency of chromatid breaks and frequency of aberrant cells, the frequency of chromatid exchanges, and chromosome-type aberrations were not predictive of cancer.

  2. DNA damage in the kidney tissue cells of the fish Rhamdia quelen after trophic contamination with aluminum sulfate

    Science.gov (United States)

    Klingelfus, Tatiane; da Costa, Paula Moiana; Scherer, Marcos; Cestari, Marta Margarete

    2015-01-01

    Abstract Even though aluminum is the third most common element present in the earth's crust, information regarding its toxicity remains scarce. It is known that in certain cases, aluminum is neurotoxic, but its effect in other tissues is unknown. The aim of this work was to analyze the genotoxic potential of aluminum sulfate in kidney tissue of the fish Rhamdia quelen after trophic contamination for 60 days. Sixty four fish were subdivided into the following groups: negative control, 5 mg, 50 mg and 500 mg of aluminum sulfate per kg of fish. Samples of the posterior kidney were taken and prepared to obtain mitotic metaphase, as well as the comet assay. The three types of chromosomal abnormalities (CA) found were categorized as chromatid breaks, decondensation of telomeric region, and early separation of sister chromatids. The tests for CA showed that the 5 mg/kg and 50 mg/kg doses of aluminum sulfate had genotoxic potential. Under these treatments, early separation of the sister chromatids was observed more frequently and decondensation of the telomeric region tended to increase in frequency. We suggest that structural changes in the proteins involved in DNA compaction may have led to the decondensation of the telomeric region, making the DNA susceptible to breaks. Moreover, early separation of the sister chromatids may have occurred due to changes in the mobility of chromosomes or proteins that keep the sister chromatids together. The comet assay confirmed the genotoxicity of aluminum sulfate in the kidney tissue of Rhamdia quelen at the three doses of exposure. PMID:26692157

  3. Cohesin without cohesion: a novel role for Pds5 in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Kevin Tong

    Full Text Available High fidelity chromosome segregation during mitosis requires that cells identify the products of DNA replication during S-phase and then maintain that identity until anaphase onset. Sister chromatid identity is achieved through cohesin complexes (Smc1, Smc3, and Mcd1 and Irr1/Scc3, but the structure through which cohesins perform this task remains enigmatic. In the absence of unambiguous data, a popular model is that a subset of cohesin subunits form a huge ring-like structure that embraces both sister chromatids. This 'one-ring two-sister chromatid embrace' model makes clear predictions--including that premature cohesion loss in mitotic cells must occur through a substantial reduction in cohesin-DNA associations. We used chromatin immunoprecipitation to directly test for cohesin dissociation from well-established cohesin binding sites in mitotic cells inactivated for Pds5--a key cohesin regulatory protein. The results reveal little if any chromatin dissociation from cohesins, despite a regimen that produces both massive loss of sister chromatid tethering and cell inviability. We further excluded models that cohesion loss in mitotic cells inactivated for Pds5 arises through either cohesin subunit degradation, premature Hos1-dependent Smc3 de-acetylation or Rad61/WAPL-dependent regulation of cohesin dynamics. In combination, our findings support a model that cohesin complexes associate with each sister and that sister chromatid cohesion likely results from cohesin-cohesin interactions. We further assessed the role that Pds5 plays in cohesion establishment during S-phase. The results show that Pds5 inactivation can result in establishment defects despite normal cohesion loading and Smc3 acetylation, revealing a novel establishment role for Pds5 that is independent of these processes. The combination of findings provides important new insights that significantly impact current models of both cohesion establishment reactions and maintenance.

  4. Observations on the radiosensitivity of guppy (Lebistes reticulatus Peters)

    International Nuclear Information System (INIS)

    The ichthyologically well-known teleostean fish, Lebistes reticulatus Peters commonly known as guppy, found abundant in pools, streams and estuaries was studied to establish its sensitivity to radiation and to explore its possible use as a biological indicator organism of radiation effects in the aquatic system. The guppy, Lebistes reticulatus was found to be radiosensitive. Chromosome aberrations were induced by gamma-irradiation of fish in vivo. Through cytogenetic technique the aberrant chromosomes were evaluated. The aberrant chromosomes observed were of various types such as chromatid gaps and breaks, chromosome gaps and breaks, chromatid and chromosome fragments, polycentrics (dicentrics and tricentrics), fusions and translocations. Of the types seen, it is concluded that dicentrics are the most reliable indicator of radiation effects. In the course of this study, the Lethal Radiation Dose in guppy within thirty days was determined. It was found to lie in the dose of 3 krad (LDsub(50/30)). (author)

  5. The radiosensitivity of nile tilapia (Oreochromis niloticus) fingerlings

    International Nuclear Information System (INIS)

    The nile tilapia (Oreochromis niloticus), a very popular fish commercially in the Philippines, was studied to determine its radiosensitivity and to see its potential as a biological indicator in aquatic ecosystems. Nile tilapia was seen to be radiosensitive. The fish were exposed to gamma-irradiation and chromosomal aberrations were induced. The various types of aberrations seen were chromatid gaps, chromosome gaps, chromatid fragments, dicentric rings, fusions, despiralizations and translocations. Among the aberrations observed, dicentric rings, fusions and chromosome gaps were strongly correlated with dosage, with only the dicentric rings increasing steadily with increasing dosage. In the course of the study, the lethal dosage50 for nile tilapia with 18 days was determined and it was observed at 2.0 krad. The modal chromosome number was also established at 2n=44 with a karyotype exhibiting 22 pairs of acrocentric chromosomes with 2 pairs of marker chromosomes present. (Author)

  6. Kinetochores coordinate pericentromeric cohesion and early DNA replication by Cdc7-Dbf4 kinase recruitment.

    Science.gov (United States)

    Natsume, Toyoaki; Müller, Carolin A; Katou, Yuki; Retkute, Renata; Gierliński, Marek; Araki, Hiroyuki; Blow, J Julian; Shirahige, Katsuhiko; Nieduszynski, Conrad A; Tanaka, Tomoyuki U

    2013-06-01

    Centromeres play several important roles in ensuring proper chromosome segregation. Not only do they promote kinetochore assembly for microtubule attachment, but they also support robust sister chromatid cohesion at pericentromeres and facilitate replication of centromeric DNA early in S phase. However, it is still elusive how centromeres orchestrate all these functions at the same site. Here, we show that the budding yeast Dbf4-dependent kinase (DDK) accumulates at kinetochores in telophase, facilitated by the Ctf19 kinetochore complex. This promptly recruits Sld3-Sld7 replication initiator proteins to pericentromeric replication origins so that they initiate replication early in S phase. Furthermore, DDK at kinetochores independently recruits the Scc2-Scc4 cohesin loader to centromeres in G1 phase. This enhances cohesin loading and facilitates robust pericentromeric cohesion in S phase. Thus, we have found the central mechanism by which kinetochores orchestrate early S phase DNA replication and robust sister chromatid cohesion at microtubule attachment sites.

  7. One-hit wonders of genomic instability

    Directory of Open Access Journals (Sweden)

    Strunnikov Alexander V

    2010-05-01

    Full Text Available Abstract Recent data show that cells from many cancers exhibit massive chromosome instability. The traditional view is that the gradual accumulation of mutations in genes involved in transcriptional regulation and cell cycle controls results in tumor development. This, however, does not exclude the possibility that some mutations could be more potent than others in destabilizing the genome by targeting both chromosomal integrity and corresponding checkpoint mechanisms simultaneously. Three such examples of "single-hit" lesions potentially leading to heritable genome destabilization are discussed. They include: failure to release sister chromatid cohesion due to the incomplete proteolytic cleavage of cohesin; massive merotelic kinetochore misattachments upon condensin depletion; and chromosome under-replication. In all three cases, cells fail to detect potential chromosomal bridges before anaphase entry, indicating that there is a basic cell cycle requirement to maintain a degree of sister chromatid bridging that is not recognizable as chromosomal damage.

  8. The distribution of α-kleisin during meiosis in the holocentromeric plant Luzula elegans.

    Science.gov (United States)

    Ma, Wei; Schubert, Veit; Martis, Mihaela Maria; Hause, Gerd; Liu, Zhaojun; Shen, Yi; Conrad, Udo; Shi, Wenqing; Scholz, Uwe; Taudien, Stefan; Cheng, Zhukuan; Houben, Andreas

    2016-09-01

    Holocentric chromosomes occur in a number of independent eukaryotic lineages, and they form holokinetic kinetochores along the entire poleward chromatid surfaces. Due to this alternative chromosome structure, Luzula elegans sister chromatids segregate already in anaphase I followed by the segregation of the homologues in anaphase II. However, not yet known is the localization and dynamics of cohesin and the structure of the synaptonemal complex (SC) during meiosis. We show here that the α-kleisin subunit of cohesin localizes at the centromeres of both mitotic and meiotic metaphase chromosomes and that it, thus, may contribute to assemble the centromere in L. elegans. This localization and the formation of a tripartite SC structure indicate that the prophase I behaviour of L. elegans is similar as in monocentric species. PMID:27294972

  9. Cytological evidence for assortment mitosis leading to loss of heterozygosity in rice.

    Science.gov (United States)

    Wang, Richard R-C; Li, Xiaomei; Chatterton, N Jerry

    2006-05-01

    In the root meristem cells of the rice line AMR, which causes loss of heterozygosity in its hybrids, both normal and assortment mitoses were observed. During normal mitosis, chromosomes did not form homologous pairs at metaphase; all chromosomes lined up at the equatorial plate and 2 chromatids of each chromosome disjoined at the centromere and moved toward opposite poles. During assortment mitosis, varying numbers of paired homologues were observed at mitotic metaphase. Two groups of 12 chromosomes separated and moved towards the opposite poles of daughter cells with few chromosomes having their chromatids separated at anaphase. These observations support the proposed mechanism that is responsible for early genotype fixation in rice hybrids involving AMR.

  10. The cytogenetic consequences of diving

    Energy Technology Data Exchange (ETDEWEB)

    Fox, D.P.; Robertson, F.W. [University of Aberdeen (United Kingdom). Dept. of Genetics

    1998-04-01

    A cytogenetic investigation has been completed to ascertain whether the practice of commercial diving causes chromosome damage. The study comprises: (i) a detailed scrutiny of the karyotype in samples of 100 cells per individual in both shallow and deep water divers, topside workers, and men not working on the rigs and without previous diving experience. (ii) A record of sister chromatid exchange, which is the most sensitive indicator of potential chromosome damage, was obtained for a sample of the three major categories and also before, during and after a series of simulated dives under controlled conditions. (iii) The measurement of sister chromatid exchange was also carried out under in vitro conditions in lymphocyte exposed to different levels of high pressure in the presence of alternative gas mixtures corresponding to those used in commercial practice. (author)

  11. Adaptive response induced by occupational exposures to ionizing radiation

    International Nuclear Information System (INIS)

    We have found a significant decreased sensitivity to the cytogenetic effects of ionizing radiation (IR) and bleomycin (BLM) in lymphocytes from individuals occupationally exposed to IR when compared with a control population. These results suggest that occupational exposures to IR can induce adaptive response that can be detected by a subsequent treatment by IR or by BLM. However, no correlation between the results obtained with both treatments was observed. A great heterogeneity in the frequencies of chromatid aberrations induced by BLM was observed. The study of the influence of different harvesting times showed that there was no correlation with the frequencies of chromatid breaks. Our results indicate that the use of BLM to detect adaptive response has several difficulties at the individual level. (author)

  12. Structure of the Pds5-Scc1 Complex and Implications for Cohesin Function

    Directory of Open Access Journals (Sweden)

    Kyle W. Muir

    2016-03-01

    Full Text Available Sister chromatid cohesion is a fundamental prerequisite to faithful genome segregation. Cohesion is precisely regulated by accessory factors that modulate the stability with which the cohesin complex embraces chromosomes. One of these factors, Pds5, engages cohesin through Scc1 and is both a facilitator of cohesion, and, conversely also mediates the release of cohesin from chromatin. We present here the crystal structure of a complex between budding yeast Pds5 and Scc1, thus elucidating the molecular basis of Pds5 function. Pds5 forms an elongated HEAT repeat that binds to Scc1 via a conserved surface patch. We demonstrate that the integrity of the Pds5-Scc1 interface is indispensable for the recruitment of Pds5 to cohesin, and that its abrogation results in loss of sister chromatid cohesion and cell viability.

  13. The Functional Role of TopBP1 in DNA Maintenance at Mitosis

    DEFF Research Database (Denmark)

    Pedersen, Rune Troelsgaard

    of unreplicated DNA and DNA-repair intermediates. These loci can manifest themselves as breaks and gaps on metaphase chromosomes, which often coincide with specific chromosome loci termed common fragile sites (CFSs). Additionally, underreplicated loci function as physical links between sister chromatids, which...... that are devoid of histones and do not stain with DAPI. Some of these UFBs are induced by replication stress and interlink CFSs on segregating sister chromatids in anaphase. Another major advance was the discovery of active processing of underreplicated loci by structure-selective endonucleases MUS81 and GEN1....... This active processing was found to be an underlying mechanism of CFS expression. A final advance was the description of how DNA damage, arising as a consequence of replication stress in S-phase, was shielded in 53BP1 nuclear bodies (NBs), preventing untimely DNA repair during the subsequent G1-phase. We...

  14. Unique DNA repair properties of a xeroderma pigmentosum revertant.

    OpenAIRE

    Cleaver, J.E.; Cortés, F; Lutze, L H; Morgan, W F; Player, A N; D. L. Mitchell

    1987-01-01

    A group A xeroderma pigmentosum revertant with normal sensitivity was created by chemical mutagenesis. It repaired (6-4) photoproducts normally but not pyrimidine dimers and had near normal levels of repair replication, sister chromatid exchange, and mutagenesis from UV light. The rate of UV-induced mutation in a shuttle vector, however, was as high as the rate in the parental xeroderma pigmentosum cell line.

  15. Processing, localization, and requirement of human separase for normal anaphase progression

    OpenAIRE

    Chestukhin, Anton; Pfeffer, Christian; Milligan, Scott; DeCaprio, James A.; Pellman, David

    2003-01-01

    In all eukaryotes, anaphase is triggered by the activation of a protease called separase. Once activated, separase cleaves a subunit of cohesin, a complex that links replicated chromatids before anaphase. Separase and cohesin are conserved from yeasts to humans. Although the machinery for dissolving sister cohesion is conserved, the regulation of this process appears to be more complex in higher eukaryotes than in yeast. Here we report the cloning of full-length human separase cDNA and the ch...

  16. Biomarkers of environmental contaminants in field population of green mussel (Perna viridis) from Karnataka-Kerala coast (South West coast of India).

    OpenAIRE

    Krishnakumar, P.K.; Sasikumar, Geetha; Bhat, G. S.; Asokan, D.P.K.

    2006-01-01

    Biomarker: sister chromatid exchange (SCE); chromosomal aberration; micronucleus (MN); hemic neoplasia (HN), mutagenic activity; comet cells. Exposure/effect represented: exposure to trace metals (Fe, Cu, Ni, Cd, Cr, Zn, Pb, Mn) / DNA damage. Analytical technique: Toxic and essential elements in tissues were determined using AAS; metaphase chromosomes were viewed using light microscope (Olympus BX50) with image analysis facility; hemolymph was stained using the Schiff Feulgen-picromethyl blu...

  17. Identification of inhibitory mechanisms preventing CENP-A assembly in the S phase of the cell cycle

    OpenAIRE

    Abreu, Rúben Lopes Pereira

    2016-01-01

    Tese de mestrado, Biologia Evolutiva e do Desenvolvimento, Universidade de Lisboa, Faculdade de Ciências, 2015 The centromere is the chromosomal locus that directs kinetochore formation in order to secure faithful segregation of sister chromatids during mitosis. Nucleosomes that contain CENP-A (centromere protein A), an H3-histone variant, are thought to be the epigenetic mark indicating active centromeres, and its assembly into chromatin requires the Mis18 complex and its dedicated chaper...

  18. Cytogenetic Abnormalities of Hematopoietic Tissue in Retired Workers of the Ohkunojima Poison Gas Factory

    OpenAIRE

    Shakil, Fouzia A.; Kuramoto, Atsushi; Yamakido, Michio; Nishimoto, Yukio; Kamada, Nanao

    1993-01-01

    A high incidence of cancer of the respiratory tract has been reported among former workers in a poison gas manufacturing plant which operated on Ohkunojima from 1927 to 1945. This report provides evidence of a high incidence of chromosome abnormality and sister chromatid exchange (SCE) rate among the former workers, as well as cytogenetic changes in two patients among the former workers with chronic myelocytic leukemia (CML). A chromosome study of seven former workers with chronic bronchitis ...

  19. Recent Advances in In Vivo Genotoxicity Testing: Prediction of Carcinogenic Potential Using Comet and Micronucleus Assay in Animal Models

    OpenAIRE

    Kang, Seung Hun; Kwon, Jee Young; Lee, Jong Kwon; Seo, Young Rok

    2013-01-01

    Genotoxic events have been known as crucial step in the initiation of cancer. To assess the risk of cancer, genotoxicity assays, including comet, micronucleus (MN), chromosomal aberration, bacterial reverse, and sister chromatid exchange assay, can be performed. Compared with in vitro genotoxicity assay, in vivo genotoxicity assay has been used to verify in vitro assay result and definitely provide biological significance for certain organs or cell types. The comet assay can detect DNA strand...

  20. Biased DNA Segregation during Stem Cell Division

    OpenAIRE

    Anversa, Piero; Leri, Annarosa; Kajstura, Jan

    2012-01-01

    Adult skeletal muscle stem cells are a heterogeneous cell population characterized by a small subset of undifferentiated cells that express at high level the paired/homeodomain gene Pax7. This category of satellite cells divides predominantly by asymmetric chromatid segregation generating a daughter cell that carries the mother DNA and retains stem cell property, and a daughter cell that inherits the newly-synthesized DNA and acquires the myocyte lineage.1

  1. Influence of DNA repair gene polymorphisms of hOGG1, XRCC1, XRCC3, ERCC2 and the folate metabolism gene MTHFR on chromosomal aberration frequencies.

    Science.gov (United States)

    Skjelbred, Camilla Furu; Svendsen, Marit; Haugan, Vera; Eek, Anette Kildal; Clausen, Kjell Oskar; Svendsen, Martin Veel; Hansteen, Inger-Lise

    2006-12-01

    We have studied the effect of genetic polymorphisms in the DNA repair genes hOGG1, XRCC1, XRCC3, ERCC2 and the MTHFR gene in the folate metabolism on the frequencies of cells with chromosomal aberrations (CA), chromosome-type aberrations (CSA), chromatid-type aberrations (CTA), chromatid breaks (CTB) and chromatid gaps (CTG) scored in peripheral blood lymphocytes from 651 Norwegian subjects of Caucasian descendant. DNA was extracted from fixed cell suspensions. The log-linear Poisson regression model was used for the combined data which included age, smoking, occupational exposure and genotype for 449 subjects. Our results suggest that individuals carrying the hOGG1 326Cys or the XRCC1 399Gln allele have an increased risk of chromosomal damage, while individuals carrying the XRCC1 194Trp or the ERCC2 751Gln allele have a reduced risk regardless of smoking habits and age. Individuals carrying the XRCC1 280His allele had an increased risk of CSA which was only apparent in non-smokers. This was independent of age. A protective effect of the XRCC3 241Met allele was only found in the older age group in non-smokers for CA, CSA and CTA, and in smokers for CSA. In the youngest age group, the opposite effect was found, with an increased risk for CA, CTA and CTG in smokers. Carrying the MTHFR 222Val allele gave an increased risk for chromosome and chromatid-type aberrations for both non-smokers and smokers, especially for individuals in the older age group, and with variable results in the youngest age group. The variables included in the different regression models accounted, however, for only 4-10% of the variation. The frequency ratio for CTG was significantly higher than for CTA and CTB for only 7 of the 43 comparisons performed. Some of the gap frequencies diverge from the trend in the CA, CSA, CTA and CTB results.

  2. Ubiquitin-dependent DNA damage bypass is separable from genome replication

    OpenAIRE

    Daigaku, Yasukazu; Davies, Adelina A.; Ulrich, Helle D.

    2010-01-01

    Postreplication repair (PRR) is a pathway that allows cells to bypass or overcome lesions during DNA replication1. In eukaryotes, damage bypass is activated by ubiquitylation of the replication clamp PCNA through components of the RAD6 pathway2. Whereas monoubiquitylation of PCNA allows mutagenic translesion synthesis by damage-tolerant DNA polymerases3-5, polyubiquitylation is required for an error-free pathway that likely involves a template switch to the undamaged sister chromatid6. Both t...

  3. Holliday junction resolution: Regulation in space and time

    OpenAIRE

    Matos, Joao; West, Stephen C.

    2014-01-01

    Holliday junctions (HJs) can be formed between sister chromatids or homologous chromosomes during the recombinational repair of DNA lesions. A variety of pathways act upon HJs to remove them from DNA, in events that are critical for appropriate chromosome segregation. Despite the identification and characterization of multiple enzymes involved in HJ processing, the cellular mechanisms that regulate and implement pathway usage have only just started to be delineated. A conserved network of cor...

  4. New insights into the formation and resolution of ultra-fine anaphase bridges

    DEFF Research Database (Denmark)

    Chan, Kok Lung; Hickson, Ian D

    2011-01-01

    Recent data indicate an unexpected requirement for proteins that were hitherto considered to be dedicated to DNA repair to facilitate the faithful disjunction of sister chromatids in anaphase. These include the Bloom's syndrome gene product, BLM and its partners, as well as a number of proteins....... In this review, we will discuss the possible sources of UFBs, and how the BLM, PICH and FA proteins might serve to process these structures in order to maintain genome stability....

  5. Genotoxic Evaluation of the Antibacterial Drug, Ciprofloxacin, in Cultured Lymphocytes of Patients with Urinary Tract Infection

    OpenAIRE

    İkbal, Mevlit; DOĞAN, Hasan; Odabaş, Hatice; PİRİM, İbrahim

    2004-01-01

    Ciprofloxacin is a quinolone carboxylic acid derivative and is commonly used in medicine. The genotoxicity of ciprofloxacin was evaluated in cultured human peripheral blood lymphocytes in patients with urinary tract infection. Sister chromatid exchange (SCE), mitotic index (MI) and replicative index (RI) were measured before and after ciprofloxacin therapy. Our results showed that SCE frequency significantly increased after ciprofloxacin therapy (P < 0.001), but MI and RI decreased (P &...

  6. TPP1 Is Required for TERT Recruitment, Telomere Elongation during Nuclear Reprogramming, and Normal Skin Development in Mice

    OpenAIRE

    Tejera, Agueda M.; Stagno d'Alcontres, Martina; Thanasoula, Maria; Marion, Rosa M.; Martinez, Paula; Liao, Chunyan; Juana M Flores; Tarsounas, Madalena; Blasco, Maria A.

    2010-01-01

    The TPP1/ACD protein (hereafter TPP1) is a component of the shelterin complex at mammalian telomeres. Here we find that Tpp1-deficient mouse embryonic fibroblasts (MEFs) show increased chromosomal instability including sister chromatid fusions and chromosomes with multitelomeric signals related to telomere fragility. Tpp1 deletion decreases both TERT (the telomerase catalytic subunit) binding to telomeres in MEFs and telomerase function at chromosome ends in vivo. Abrogation of Tpp1 abolished...

  7. Putting CENP-A in its place

    OpenAIRE

    Stellfox, Madison E.; Bailey, Aaron O.; Foltz, Daniel R.

    2012-01-01

    The centromere is the chromosomal region that directs kinetochore assembly during mitosis in order to facilitate the faithful segregation of sister chromatids. The location of the human centromere is epigenetically specified. The presence of nucleosomes that contain the histone H3 variant, CENP-A, are thought to be the epigenetic mark that indicates active centromeres. Maintenance of centromeric identity requires the deposition of new CENP-A nucleosomes with each cell cycle. During S-phase, e...

  8. Comparison of clonogenic assay with premature chromosome condensation assay in prediction of human cell radiosensitivity

    Institute of Scientific and Technical Information of China (English)

    Zhuan-Zi Wang; Wen-Jian Li; Hong Zhang; Jian-She Yang; Rong Qiu; Xiao Wang

    2006-01-01

    AIM: To determine whether the number of non-rejoining G2-chromatid breaks can predict the radiosensitivity of human cell lines.METHODS: Cell lines of human ovary carcinoma cells (HO8910), human hepatoma cells (HepG2) and liver cells (L02) were irradiated with a range of doses and assessed both of cell survival and non-rejoining G2-chromatid breaks at 24 h after irradiation. Cell survival was documented by a colony assay. Non-rejoining G2-chromatid breaks were measured by counting the number of non-rejoining G2 chromatid breaks at 24 h after irradiation, detected by the prematurely chromosome condensed (PCC) technique.RESULTS: A linear-quadratic survival curve was observed in three cell lines, and HepG2 was the most sensitive to y-radiation. A dose-dependent linear increase was observed in radiation-induced non-rejoining G2-PCC breaks measured at 24 h after irradiation in all cell lines, and HepG2 was the most susceptible to induction of non-rejoining G2-PCC breaks. A close correlation was found between the clonogenic radiosensitivity and the radiation-induced non-rejoining G2-PCC breaks (r= 0.923). Furthermore, survival-aberration correlations for two or more than two doses lever were also significant.CONCLUSION: The number of non-rejoining G2 PCC breaks holds considerable promise for predicting the radiosensitivity of normal and tumor cells when two or more than two doses lever is tested.

  9. Etude du système de résolution des dimères de chromosome chez Vibrio cholerae - Implication dans le contrôle de la lysogénie du phage CTXφ codant pour la toxine cholérique

    OpenAIRE

    Val, Marie-Eve

    2008-01-01

    The majority of the bacteria have a single circular chromosome. At the time of replication, chromosome dimers can be formed by homologous recombination between sister chromatides. Dimerisation of replicating chromosomes prevents the faithful segregation of genetic information between the two daughter cells. To correct this, the tyrosine recombinases, XerC and XerD, resolve dimers by adding an additional crossover at a specific site on the chromosome called dif. In Escherichia coli, the resolu...

  10. Cohesin Is limiting for the suppression of DNA damage-induced recombination between homologous chromosomes.

    Directory of Open Access Journals (Sweden)

    Shay Covo

    2010-07-01

    Full Text Available Double-strand break (DSB repair through homologous recombination (HR is an evolutionarily conserved process that is generally error-free. The risk to genome stability posed by nonallelic recombination or loss-of-heterozygosity could be reduced by confining HR to sister chromatids, thereby preventing recombination between homologous chromosomes. Here we show that the sister chromatid cohesion complex (cohesin is a limiting factor in the control of DSB repair and genome stability and that it suppresses DNA damage-induced interactions between homologues. We developed a gene dosage system in tetraploid yeast to address limitations on various essential components in DSB repair and HR. Unlike RAD50 and RAD51, which play a direct role in HR, a 4-fold reduction in the number of essential MCD1 sister chromatid cohesion subunit genes affected survival of gamma-irradiated G(2/M cells. The decreased survival reflected a reduction in DSB repair. Importantly, HR between homologous chromosomes was strongly increased by ionizing radiation in G(2/M cells with a single copy of MCD1 or SMC3 even at radiation doses where survival was high and DSB repair was efficient. The increased recombination also extended to nonlethal doses of UV, which did not induce DSBs. The DNA damage-induced recombinants in G(2/M cells included crossovers. Thus, the cohesin complex has a dual role in protecting chromosome integrity: it promotes DSB repair and recombination between sister chromatids, and it suppresses damage-induced recombination between homologues. The effects of limited amounts of Mcd1and Smc3 indicate that small changes in cohesin levels may increase the risk of genome instability, which may lead to genetic diseases and cancer.

  11. Antiviral Activity of Metal-Containing Polymers—Organotin and Cisplatin-Like Polymers

    OpenAIRE

    Girish Barot; Roner, Michael R.; Charles E. Carraher Jr.; Kimberly Shahi

    2011-01-01

    Polymers containing platinum and to a lesser extent tin, have repeatedly demonstrated antitumor activity in vitro and in vivo against a variety of cell and tumor types. The mechanisms responsible for the antitumor activity include inducing a delay in cell proliferation and sister chromatid exchanges blocking tumor growth. As most DNA and some RNA viruses require, and even induce, infected cells to initiate DNA replication and subsequent cell division, compounds with antitumor activity will ve...

  12. ANALYSES OF CHROMOSOME ABERRATIONS IN LYMPHOCYTES AND BONE MARROW CELLS INDUCED BY RADIATION OR BENZENE

    Institute of Scientific and Technical Information of China (English)

    张鸿源; 王兰金; 等

    1995-01-01

    The chromosomoe and chromatid type aberration can be induced by benzene and the dicentric and ring ones were not observed in vitro experiment but observed in vivo one.In vitro experiment a good linear reression can be given between benzene concentrations and total aberration cells while power regression for radiation dose.The chromosome aberrations induced by benzene combined with radiation in rabbit blood lymphocytes are higher than in bone marryow cells.

  13. Rapid induction of Alternative Lengthening of Telomeres by depletion of the histone chaperone ASF1

    OpenAIRE

    O'Sullivan, Roderick J; Arnoult, Nausica; Daniel H Lackner; Oganesian, Liana; Haggblom, Candy; Corpet, Armelle; Almouzni, Genevieve; Karlseder, Jan

    2014-01-01

    The mechanism of activation of the Alternative Lengthening of Telomeres (ALT) pathway of mammalian chromosome end maintenance has remained an unresolved issue. We have discovered that co-depletion of the histone chaperones ASF1a and ASF1b in human cells induced all hallmarks of ALT in both primary and cancer cells. These included the formation of ALT associated PML bodies (APBs), extra-chromosomal telomeric DNA species an elevated frequency of telomeric sister chromatid exchanges (t-SCE) even...

  14. The Reduction of Chromosome Number in Meiosis Is Determined by Properties Built into the Chromosomes

    OpenAIRE

    Paliulis, Leocadia V.; Nicklas, R. Bruce

    2000-01-01

    In meiosis I, two chromatids move to each spindle pole. Then, in meiosis II, the two are distributed, one to each future gamete. This requires that meiosis I chromosomes attach to the spindle differently than meiosis II chromosomes and that they regulate chromosome cohesion differently. We investigated whether the information that dictates the division type of the chromosome comes from the whole cell, the spindle, or the chromosome itself. Also, we determined when chromosomes can switch from ...

  15. Multiple subunits of the Caenorhabditis elegans anaphase-promoting complex are required for chromosome segregation during meiosis I.

    OpenAIRE

    Davis, Edward S.; Wille, Lucia; Chestnut, Barry A.; Sadler, Penny L.; Shakes, Diane C; Golden, Andy

    2002-01-01

    Two genes, originally identified in genetic screens for Caenorhabditis elegans mutants that arrest in metaphase of meiosis I, prove to encode subunits of the anaphase-promoting complex or cyclosome (APC/C). RNA interference studies reveal that these and other APC/C subunits are essential for the segregation of chromosomal homologs during meiosis I. Further, chromosome segregation during meiosis I requires APC/C functions in addition to the release of sister chromatid cohesion.

  16. Polo kinase Cdc5 is a central regulator of meiosis I

    OpenAIRE

    Attner, Michelle A.; Miller, Matthew P.; Ee, Ly-Sha; Elkin, Sheryl K; Amon, Angelika

    2013-01-01

    During meiosis, two consecutive rounds of chromosome segregation yield four haploid gametes from one diploid cell. The Polo kinase Cdc5 is required for meiotic progression, but how Cdc5 coordinates multiple cell-cycle events during meiosis I is not understood. Here we show that CDC5-dependent phosphorylation of Rec8, a subunit of the cohesin complex that links sister chromatids, is required for efficient cohesin removal from chromosome arms, which is a prerequisite for meiosis I chromosome se...

  17. Cdc7-Dbf4 Is a Gene-Specific Regulator of Meiotic Transcription in Yeast

    OpenAIRE

    Lo, Hsiao-Chi; Kunz, Ryan C.; Chen, Xiangyu; Marullo, Allison; Steven P Gygi; Hollingsworth, Nancy M.

    2012-01-01

    Meiosis divides the chromosome number of the cell in half by having two rounds of chromosome segregation follow a single round of chromosome duplication. The first meiotic division is unique in that homologous pairs of sister chromatids segregate to opposite poles. Recent work in budding and fission yeast has shown that the cell cycle kinase, Cdc7-Dbf4, is required for many meiosis-specific chromosomal functions necessary for proper disjunction at meiosis I. This work reveals another role for...

  18. Holocentric plant meiosis: first sisters, then homologues

    OpenAIRE

    Heckmann, Stefan; Schubert, Veit; Houben, Andreas

    2014-01-01

    Meiosis is a crucial process of sexual reproduction by forming haploid gametes from diploid precursor cells. It involves 2 subsequent divisions (meiosis I and meiosis II) after one initial round of DNA replication. Homologous monocentric chromosomes are separated during the first and sister chromatids during the second meiotic division. The faithful segregation of monocentric chromosomes is realized by mono-orientation of fused sister kinetochores at metaphase I and by bi-orientation of siste...

  19. High-throughput knockout screen in Schizosaccharomyces pombe identifies a novel gene required for efficient homolog disjunction during meiosis I

    OpenAIRE

    Rumpf, Cornelia; Cipak, Lubos; Novatchkova, Maria; LI, ZHANG; Polakova, Silvia; Dudas, Andrej; Kovacikova, Ines; Miadokova, Eva; Ammerer, Gustav; Gregan, Juraj

    2010-01-01

    Meiosis is the process which produces haploid gametes from diploid precursor cells. This reduction of chromosome number is achieved by two successive divisions. Whereas homologs segregate during meiosis I, sister chromatids segregate during meiosis II. To identify novel proteins required for proper segregation of chromosomes during meiosis, we applied a high-throughput knockout technique to delete 87 S. pombe genes whose expression is upregulated during meiosis and analyzed the mutant phenoty...

  20. Separase Is Required for Homolog and Sister Disjunction during Drosophila melanogaster Male Meiosis, but Not for Biorientation of Sister Centromeres.

    OpenAIRE

    Blattner, Ariane C.; Soumya Chaurasia; McKee, Bruce D.; Lehner, Christian F.

    2016-01-01

    Spatially controlled release of sister chromatid cohesion during progression through the meiotic divisions is of paramount importance for error-free chromosome segregation during meiosis. Cohesion is mediated by the cohesin protein complex and cleavage of one of its subunits by the endoprotease separase removes cohesin first from chromosome arms during exit from meiosis I and later from the pericentromeric region during exit from meiosis II. At the onset of the meiotic divisions, cohesin has ...

  1. Strong nucleosomes of A. thaliana concentrate in centromere regions.

    Science.gov (United States)

    Salih, Bilal; Trifonov, Edward N

    2015-01-01

    Earlier identified strongest nucleosome DNA sequences of A. thaliana, those with visible 10-11 base sequence periodicity, are mapped along chromosomes. Resulting positional distributions reveal distinct maxima, one per chromosome, located in the centromere regions. Sequence-directed nucleosome mapping demonstrates that the strong nucleosomes (SNs) make tight arrays, several 'parallel' nucleosomes each, suggesting a columnar chromatin structure. The SNs represent a new class of centromeric nucleosomes, presumably, participating in synapsis of chromatids and securing the centromere architecture.

  2. Cell-cycle regulation of cohesin stability along fission yeast chromosomes

    OpenAIRE

    Bernard, Pascal; Schmidt, Christine Katrin; Vaur, Sabine; Dheur, Sonia; Drogat, Julie; Genier, Sylvie; Ekwall, Karl; Uhlmann, Frank; Javerzat, Jean-Paul

    2007-01-01

    Sister chromatid cohesion is mediated by cohesin, but the process of cohesion establishment during S-phase is still enigmatic. In mammalian cells, cohesin binding to chromatin is dynamic in G1, but becomes stabilized during S-phase. Whether the regulation of cohesin stability is integral to the process of cohesion establishment is unknown. Here, we provide evidence that fission yeast cohesin also displays dynamic behavior. Cohesin association with G1 chromosomes requires continued activity of...

  3. Cohesin acetyltransferase Esco2 is a cell viability factor and is required for cohesion in pericentric heterochromatin

    OpenAIRE

    Whelan, Gabriela; Kreidl, Emanuel; Wutz, Gordana; Egner, Alexander; Peters, Jan-Michael; Eichele, Gregor

    2012-01-01

    Sister chromatid cohesion, mediated by cohesin and regulated by Sororin, is essential for chromosome segregation. In mammalian cells, cohesion establishment and Sororin recruitment to chromatin‐bound cohesin depends on the acetyltransferases Esco1 and Esco2. Mutations in Esco2 cause Roberts syndrome, a developmental disease in which mitotic chromosomes have a ‘railroad’ track morphology. Here, we show that Esco2 deficiency leads to termination of mouse development at pre‐ and post‐implantatio...

  4. Cell Adhesion Geometry Regulates Non-Random DNA Segregation and Asymmetric Cell Fates in Mouse Skeletal Muscle Stem Cells

    OpenAIRE

    Siham Yennek; Mithila Burute; Manuel Théry; Shahragim Tajbakhsh

    2014-01-01

    Cells of several metazoan species have been shown to non-randomly segregate their DNA such that older template DNA strands segregate to one daughter cell. The mechanisms that regulate this asymmetry remain undefined. Determinants of cell fate are polarized during mitosis and partitioned asymmetrically as the spindle pole orients during cell division. Chromatids align along the pole axis; therefore, it is unclear whether extrinsic cues that determine spindle pole position also promote non-rand...

  5. Cell Adhesion Geometry Regulates Non-Random DNA Segregation and Asymmetric Cell Fates in Mouse Skeletal Muscle Stem Cells

    OpenAIRE

    Yennek, Siham; Burute, Mithila; Théry, Manuel; Tajbakhsh, Shahragim

    2014-01-01

    International audience Cells of several metazoan species have been shown to non-randomly segregate their DNA such that older template DNA strands segregate to one daughter cell. The mechanisms that regulate this asymmetry remain undefined. Determinants of cell fate are polarized during mitosis and partitioned asymmetrically as the spindle pole orients during cell division. Chromatids align along the pole axis; therefore, it is unclear whether extrinsic cues that determine spindle pole posi...

  6. Cell adhesion geometry regulates non-random DNA segregation and asymmetric cell fates in mouse skeletal muscle stem cells.

    OpenAIRE

    Yennek, Siham; Burute, Mithila; Théry, Manuel; Tajbakhsh, Shahragim

    2014-01-01

    International audience Cells of several metazoan species have been shown to non-randomly segregate their DNA such that older template DNA strands segregate to one daughter cell. The mechanisms that regulate this asymmetry remain undefined. Determinants of cell fate are polarized during mitosis and partitioned asymmetrically as the spindle pole orients during cell division. Chromatids align along the pole axis; therefore, it is unclear whether extrinsic cues that determine spindle pole posi...

  7. Cell adhesion geometry regulates non-random DNA segregation and asymmetric cell fates in mouse skeletal muscle stem cells

    OpenAIRE

    Yennek, Siham; Burute, Mithila; Thery, Manuel

    2014-01-01

    Cells of several metazoan species have been shown to non-randomly segregate their DNA such that older template DNA strands segregate to one daughter cell. The mechanisms that regulate this asymmetry remain undefined. Determinants of cell fate are polarized during mitosis and partitioned asymmetrically as the spindle pole orients during cell division. Chromatids align along the pole axis; therefore, it is unclear whether extrinsic cues that determine spindle pole position also promote non-rand...

  8. Statistical Aspects of Using Biologic Markers

    OpenAIRE

    Margolin, Barry H.

    1988-01-01

    This expository paper surveys a variety of statistical issues pertinent to the design and analysis of studies involving biologic markers of human genotoxic exposure. Examples with cytogenetic and mutagenic end points are presented. One principal theme is the valuable interplay of ideas among statistical analyses for in vitro, in vivo and human assays for genetic toxicity; e.g., statistical analysis of sister chromatid exchanges in vitro is suggestive of an analytical approach to the study of ...

  9. Genotoxicity of the herbicide butachlor in cultured human lymphocytes.

    Science.gov (United States)

    Sinha, S; Panneerselvam, N; Shanmugam, G

    1995-08-01

    Butachlor, a pre-emergence herbicide was investigated for its ability to induce sister chromatid exchanges (SCE) and chromosome aberrations (CA) in cultured human peripheral blood lymphocytes. Mitogen-stimulated lymphocytes were treated with three different concentrations (5, 10 and 20 micrograms/ml) of butachlor for 24, 48 and 72 h. Our results indicate a dose-dependent increase in the frequency of chromosomal aberrations at 24, 48 and 72 h of treatment with butachlor. No SCE was promoted by butachlor.

  10. A driving and coupling “Pac-Man” mechanism for chromosome poleward translocation in anaphase A

    OpenAIRE

    Liu, Jian; Onuchic, José N.

    2006-01-01

    During mitosis, chromatid harnesses its kinetochore translocation at the depolymerizing microtubule ends for its poleward movement in anaphase A. The force generation mechanism for such movement remains unknown. Analysis of the current experimental results shows that the bending energy release from the bound tubulin subunits alone cannot provide sufficient driving force. Additional contribution from effective electrostatic attractions between the kinetochore and the microtubule is needed for ...

  11. An investigation of the genetic toxicology of irradiated foodstuffs using short-term test systems

    International Nuclear Information System (INIS)

    As part of a programme of short-term tests used to detect possible genetic toxicity in irradiated foodstuffs, cultured Chinese hamster ovary cells were exposed to extracts and digests of irradiated and unirradiated dates, fish and chicken and subjected to tests for cytotoxicity, sister chromatid exchange induction and mutation to thioguanine resistance. The results showed no evidence of genetic toxicity induced in food by irradiation. The general applicability of cell culture tests to the detection of mutagens in food is discussed. (author)

  12. DNA bending facilitates the error-free DNA damage tolerance pathway and upholds genome integrity

    OpenAIRE

    Gonzalez-Huici, V.; Szakal, B.; Urulangodi, M.; Psakhye, I.; Castellucci, F.; Menolfi, D.; Rajakumara, E.; Fumasoni, M.; Bermejo, R; Jentsch, S; Branzei, D.

    2014-01-01

    DNA replication is sensitive to damage in the template. To bypass lesions and complete replication, cells activate recombination mediated (error-free) and translesion synthesis-mediated (errorprone) DNA damage tolerance pathways. Crucial for error-free DNA damage tolerance is template switching, which depends on the formation and resolution of damage-bypass intermediates consisting of sister chromatid junctions. Here we show that a chromatin architectural pathway involving the high mobility g...

  13. Sequence Classification: 804806 [

    Lifescience Database Archive (English)

    Full Text Available lex promotes anaphase by mediating destruction of Pds1 which binds to Esp1 and inhibits its activity; Esp1p||ref|||| http://www.ncbi.nlm.nih.gov/protein/?term=Chro.70313 ... ...Non-TMB Non-TMH Non-TMB Non-TMB Non-TMB TMB >Chro.70313 Esp1 promotes sister chromatid separation by mediati...ng dissociation from the chromatin of the cohesin Scc1. The anaphase-promoting comp

  14. Terminalia catappa, an anticlastogenic agent against MMS induced genotoxicity in the human lymphocyte culture and in bone marrow cells of Albino mice

    Directory of Open Access Journals (Sweden)

    Mohammad Sultan Ahmad

    2014-07-01

    Conclusion: Extracts of T. catappa significantly reduced chromosomal aberrations up to 11.65% to 40.30% at different dosages against MMS induced toxicity, similarly sister chromatid exchange was reduced and replication index enhanced in vitro. Similarly in the in vivo experiments, the effective reduction in clastogeny ranges from 19.70% to 40.90%. Their reducing potential was time and dose dependant.

  15. Distance segregation of sex chromosomes in crane-fly spermatocytes studied using laser microbeam irradiations.

    Science.gov (United States)

    Forer, Arthur; Ferraro-Gideon, Jessica; Berns, Michael

    2013-10-01

    Univalent sex chromosomes in crane-fly spermatocytes have kinetochore spindle fibres to each spindle pole (amphitelic orientation) from metaphase throughout anaphase. The univalents segregate in anaphase only after the autosomes approach the poles. As each univalent moves in anaphase, one spindle fibre shortens and the other spindle fibre elongates. To test whether the directionality of force production is fixed at anaphase, that is, whether one spindle fibre can only elongate and the other only shorten, we cut univalents in half with a laser microbeam, to create two chromatids. In both sex-chromosome metaphase and sex-chromosome anaphase, the two chromatids that were formed moved to opposite poles (to the poles to which their fibre was attached) at speeds about the same as autosomes, much faster than the usual speeds of univalent movements. Since the chromatids moved to the pole to which they were attached, independent of the direction to which the univalent as a whole was moving, the spindle fibre that normally elongates in anaphase still is able to shorten and produce force towards the pole when allowed (or caused) to do so. PMID:23315093

  16. Frequency and distribution studies of asymmetrical versus symmetrical chromosome aberrations

    International Nuclear Information System (INIS)

    Two aspects of the relationship between Asymmetrical (A) and Symmetrical (S) radiation-induced chromosomal aberrations are considered in this paper. (1) Are A and S truly alternative modes of lesion interaction. Relative frequencies for chromatid-type and chromosome-type are examined, and new lymphocyte data using banding is used to look at this, and also for parallelism in chromosome participation of the two forms for various aberration categories. All the tests applied suggest that A and S are alternative interaction modes. (2) The long-term survival characteristics of A and S are discussed, and the differences in expected frequencies of derived S per surviving cell from chromosome-type and chromatid-types are stressed. Since many in vivo tissues have varying mixtures of potential chromatid and chromosome aberration-bearing target cells, ultimate cell survival and derived S frequencies may differ between tissues for the same absorbed dose. An Appendix gives Relative Corrected Lengths (RCL) for chromosomes of the human karyotype which should be used when testing the various exchange aberration categories for random chromosome participation. (orig.)

  17. The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability

    Directory of Open Access Journals (Sweden)

    Noonan James P

    2001-07-01

    Full Text Available Abstract Background Bloom syndrome is a rare cancer-prone disorder in which the cells of affected persons have a high frequency of somatic mutation and genomic instability. Bloom syndrome cells have a distinctive high frequency of sister chromatid exchange and quadriradial formation. BLM, the protein altered in BS, is a member of the RecQ DNA helicase family, whose members share an average of 40% identity in the helicase domain and have divergent N-terminal and C-terminal flanking regions of variable lengths. The BLM DNA helicase has been shown to localize to the ND10 (nuclear domain 10 or PML (promyelocytic leukemia nuclear bodies, where it associates with TOPIIIα, and to the nucleolus. Results This report demonstrates that the N-terminal domain of BLM is responsible for localization of the protein to the nuclear bodies, while the C-terminal domain directs the protein to the nucleolus. Deletions of the N-terminal domain of BLM have little effect on sister chromatid exchange frequency and chromosome stability as compared to helicase and C-terminal mutations which can increase SCE frequency and chromosome abnormalities. Conclusion The helicase activity and the C-terminal domain of BLM are critical for maintaining genomic stability as measured by the sister chromatid exchange assay. The localization of BLM into the nucleolus by the C-terminal domain appears to be more important to genomic stability than localization in the nuclear bodies.

  18. The Monopolin Complex Crosslinks Kinetochore Components to Regulate Chromosome-Microtubule Attachments

    Energy Technology Data Exchange (ETDEWEB)

    Corbett, Kevin D.; Yip, Calvin K.; Ee, Ly-Sha; Walz, Thomas; Amon, Angelika; Harrison, Stephen C. (Harvard-Med); (MIT)

    2010-09-27

    The monopolin complex regulates different types of kinetochore-microtubule attachments in fungi, ensuring sister chromatid co-orientation in Saccharomyces cerevisiae meiosis I and inhibiting merotelic attachment in Schizosaccharomyces pombe mitosis. In addition, the monopolin complex maintains the integrity and silencing of ribosomal DNA (rDNA) repeats in the nucleolus. We show here that the S. cerevisiae Csm1/Lrs4 monopolin subcomplex has a distinctive V-shaped structure, with two pairs of protein-protein interaction domains positioned {approx}10 nm apart. Csm1 presents a conserved hydrophobic surface patch that binds two kinetochore proteins: Dsn1, a subunit of the outer-kinetochore MIND/Mis12 complex, and Mif2/CENP-C. Csm1 point-mutations that disrupt kinetochore-subunit binding also disrupt sister chromatid co-orientation in S. cerevisiae meiosis I. We further show that the same Csm1 point-mutations affect rDNA silencing, probably by disrupting binding to the rDNA-associated protein Tof2. We propose that Csm1/Lrs4 functions as a molecular clamp, crosslinking kinetochore components to enforce sister chromatid co-orientation in S. cerevisiae meiosis I and to suppress merotelic attachment in S. pombe mitosis, and crosslinking rDNA repeats to aid rDNA silencing.

  19. An electrostatic model for biological cell division

    CERN Document Server

    Faraggi, Eshel

    2010-01-01

    Probably the most fundamental processes for biological systems is their ability to create themselves through the use of cell division and cell differentiation. In this work a simple physical model is proposed for biological cell division. The model consists of a positive ionic gradient across the cell membrane, and concentration of charge at the nodes of the spindle and on the chromosomes. A simple calculation, based on Coulomb's Law, shows that under such circumstances a chromosome will tend to break up to its constituent chromatids and that the chromatids will be separated by a distance that is an order of thirty percent of the distance between the spindle nodes. Further repulsion between the nodes will tend to stretch the cell and eventually break the cell membrane between the separated chromatids, leading to cell division. The importance of this work is in continuing the understanding of the electromagnetic basis of cell division and providing it with an analytical model. A central implication of this and...

  20. On the robustness of SAC silencing in closed mitosis

    Science.gov (United States)

    Ruth, Donovan; Liu, Jian

    Mitosis equally partitions sister chromatids to two daughter cells. This is achieved by properly attaching these chromatids via their kinetochores to microtubules that emanate from the spindle poles. Once the last kinetochore is properly attached, the spindle microtubules pull the sister chromatids apart. Due to the dynamic nature of microtubules, however, kinetochore-microtubule attachment often goes wrong. When this erroneous attachment occurs, it locally activates an ensemble of proteins, called the spindle assembly checkpoint proteins (SAC), which halts the mitotic progression until all the kinetochores are properly attached by spindle microtubules. The timing of SAC silencing thus determines the fidelity of chromosome segregation. We previously established a spatiotemporal model that addresses the robustness of SAC silencing in open mitosis for the first time. Here, we focus on closed mitosis by examining yeast mitosis as a model system. Though much experimental work has been done to study the SAC in cells undergoing closed mitosis, the processes responsible are not well understood. We leverage and extend our previous model to study SAC silencing mechanism in closed mitosis. We show that a robust signal of the SAC protein accumulation at the spindle pole body can be achieved. This signal is a nonlinear increasing function of number of kinetochore-microtubule attachments, and can thus serve as a robust trigger to time the SAC silencing. Together, our mechanism provides a unified framework across species that ensures robust SAC silencing and fidelity of chromosome segregation in mitosis. Intramural research program in NHLBI at NIH.

  1. Chromosome aberrations in workers of beach sand mineral industries

    International Nuclear Information System (INIS)

    Beach Sand Mining (BSM) is a profitable industry earning a sizable income for the country by way of foreign exchange. The Indian coast is rich in rare earths such as ilmenite, rutile, leucoxene, zircon, garnet and sillimanite, and is invariably associated with radioactive monazite. Due to the nature of the separation processes involved and the manual handling, workers in these factories are continuously being exposed to suspended particles containing naturally occurring radioactive materials. An attempt was made to estimate DNA damage using a chromosome aberration assay to monitor radiation effects in workers of BSM industries in India. The study group comprised 27 BSM workers and 20 controls. Percentage yields of dicentrics, acentric fragments and chromatid breaks observed in the control group were 0.058 ± 0.017, 0.073 ± 0.03 and 0.22 ± 0.112, respectively. Percentage yields of dicentrics + centric rings, acentric fragments and chromatid breaks observed in the BSM group were 0.029 ± 0.01 (P value 0.19), 0.24 ± 0.06 (P value 0.006) and 0.455 ± 0.06 (P value 0.0004), respectively. Elevated levels of fragments and chromatid aberrations are suggestive of low-dose radiation effects and also chemically-induced DNA damage. (authors)

  2. Dynamic and Stable Cohesins Regulate Synaptonemal Complex Assembly and Chromosome Segregation.

    Science.gov (United States)

    Gyuricza, Mercedes R; Manheimer, Kathryn B; Apte, Vandana; Krishnan, Badri; Joyce, Eric F; McKee, Bruce D; McKim, Kim S

    2016-07-11

    Assembly of the synaptonemal complex (SC) in Drosophila depends on two independent pathways defined by the chromosome axis proteins C(2)M and ORD. Because C(2)M encodes a Kleisin-like protein and ORD is required for sister-chromatid cohesion, we tested the hypothesis that these two SC assembly pathways depend on two cohesin complexes. Through single- and double-mutant analysis to study the mitotic cohesion proteins Stromalin (SA) and Nipped-B (SCC2) in meiosis, we provide evidence that there are at least two meiosis-specific cohesin complexes. One complex depends on C(2)M, SA, and Nipped-B. Despite the presence of mitotic cohesins SA and Nipped-B, this pathway has only a minor role in meiotic sister-centromere cohesion and is primarily required for homolog interactions. C(2)M is continuously incorporated into pachytene chromosomes even though SC assembly is complete. In contrast, the second complex, which depends on meiosis-specific proteins SOLO, SUNN, and ORD is required for sister-chromatid cohesion, localizes to the centromeres and is not incorporated during prophase. Our results show that the two cohesin complexes have unique functions and are regulated differently. Multiple cohesin complexes may provide the diversity of activities required by the meiotic cell. For example, a dynamic complex may allow the chromosomes to regulate meiotic recombination, and a stable complex may be required for sister-chromatid cohesion. PMID:27291057

  3. The Slx4-Dpb11 scaffold complex: coordinating the response to replication fork stalling in S-phase and the subsequent mitosis.

    Science.gov (United States)

    Princz, Lissa N; Gritenaite, Dalia; Pfander, Boris

    2015-01-01

    Replication fork stalling at DNA lesions is a common problem during the process of DNA replication. One way to allow the bypass of these lesions is via specific recombination-based mechanisms that involve switching of the replication template to the sister chromatid. Inherent to these mechanisms is the formation of DNA joint molecules (JMs) between sister chromatids. Such JMs need to be disentangled before chromatid separation in mitosis and the activity of JM resolution enzymes, which is under stringent cell cycle control, is therefore up-regulated in mitosis. An additional layer of control is facilitated by scaffold proteins. In budding yeast, specifically during mitosis, Slx4 and Dpb11 form a cell cycle kinase-dependent complex with the Mus81-Mms4 structure-selective endonuclease, which allows efficient JM resolution by Mus81. Furthermore, Slx4 and Dpb11 interact even prior to joining Mus81 and respond to replication fork stalling in S-phase. This S-phase complex is involved in the regulation of the DNA damage checkpoint as well as in early steps of template switch recombination. Similar interactions and regulatory principles are found in human cells suggesting that Slx4 and Dpb11 may have an evolutionary conserved role organizing the cellular response to replication fork stalling.

  4. Resolving RAD51C function in late stages of homologous recombination

    Directory of Open Access Journals (Sweden)

    Kuznetsov Sergey G

    2007-06-01

    Full Text Available Abstract DNA double strand breaks are efficiently repaired by homologous recombination. One of the last steps of this process is resolution of Holliday junctions that are formed at the sites of genetic exchange between homologous DNA. Although various resolvases with Holliday junctions processing activity have been identified in bacteriophages, bacteria and archaebacteria, eukaryotic resolvases have been elusive. Recent biochemical evidence has revealed that RAD51C and XRCC3, members of the RAD51-like protein family, are involved in Holliday junction resolution in mammalian cells. However, purified recombinant RAD51C and XRCC3 proteins have not shown any Holliday junction resolution activity. In addition, these proteins did not reveal the presence of a nuclease domain, which raises doubts about their ability to function as a resolvase. Furthermore, oocytes from infertile Rad51C mutant mice exhibit precocious separation of sister chromatids at metaphase II, a phenotype that reflects a defect in sister chromatid cohesion, not a lack of Holliday junction resolution. Here we discuss a model to explain how a Holliday junction resolution defect can lead to sister chromatid separation in mouse oocytes. We also describe other recent in vitro and in vivo evidence supporting a late role for RAD51C in homologous recombination in mammalian cells, which is likely to be resolution of the Holliday junction.

  5. High-Resolution Mapping of Homologous Recombination Events in rad3 Hyper-Recombination Mutants in Yeast.

    Directory of Open Access Journals (Sweden)

    Sabrina L Andersen

    2016-03-01

    Full Text Available The Saccharomyces cerevisae RAD3 gene is the homolog of human XPD, an essential gene encoding a DNA helicase of the TFIIH complex involved in both nucleotide excision repair (NER and transcription. Some mutant alleles of RAD3 (rad3-101 and rad3-102 have partial defects in DNA repair and a strong hyper-recombination (hyper-Rec phenotype. Previous studies showed that the hyper-Rec phenotype associated with rad3-101 and rad3-102 can be explained as a consequence of persistent single-stranded DNA gaps that are converted to recombinogenic double-strand breaks (DSBs by replication. The systems previously used to characterize the hyper-Rec phenotype of rad3 strains do not detect the reciprocal products of mitotic recombination. We have further characterized these events using a system in which the reciprocal products of mitotic recombination are recovered. Both rad3-101 and rad3-102 elevate the frequency of reciprocal crossovers about 100-fold. Mapping of these events shows that three-quarters of these crossovers reflect DSBs formed at the same positions in both sister chromatids (double sister-chromatid breaks, DSCBs. The remainder reflects DSBs formed in single chromatids (single chromatid breaks, SCBs. The ratio of DSCBs to SCBs is similar to that observed for spontaneous recombination events in wild-type cells. We mapped 216 unselected genomic alterations throughout the genome including crossovers, gene conversions, deletions, and duplications. We found a significant association between the location of these recombination events and regions with elevated gamma-H2AX. In addition, there was a hotspot for deletions and duplications at the IMA2 and HXT11 genes near the left end of chromosome XV. A comparison of these data with our previous analysis of spontaneous mitotic recombination events suggests that a sub-set of spontaneous events in wild-type cells may be initiated by incomplete NER reactions, and that DSCBs, which cannot be repaired by sister-chromatid

  6. Shugoshin prevents dissociation of cohesin from centromeres during mitosis in vertebrate cells.

    Directory of Open Access Journals (Sweden)

    Barry E McGuinness

    2005-03-01

    Full Text Available Cohesion between sister chromatids is essential for their bi-orientation on mitotic spindles. It is mediated by a multisubunit complex called cohesin. In yeast, proteolytic cleavage of cohesin's alpha kleisin subunit at the onset of anaphase removes cohesin from both centromeres and chromosome arms and thus triggers sister chromatid separation. In animal cells, most cohesin is removed from chromosome arms during prophase via a separase-independent pathway involving phosphorylation of its Scc3-SA1/2 subunits. Cohesin at centromeres is refractory to this process and persists until metaphase, whereupon its alpha kleisin subunit is cleaved by separase, which is thought to trigger anaphase. What protects centromeric cohesin from the prophase pathway? Potential candidates are proteins, known as shugoshins, that are homologous to Drosophila MEI-S332 and yeast Sgo1 proteins, which prevent removal of meiotic cohesin complexes from centromeres at the first meiotic division. A vertebrate shugoshin-like protein associates with centromeres during prophase and disappears at the onset of anaphase. Its depletion by RNA interference causes HeLa cells to arrest in mitosis. Most chromosomes bi-orient on a metaphase plate, but precocious loss of centromeric cohesin from chromosomes is accompanied by loss of all sister chromatid cohesion, the departure of individual chromatids from the metaphase plate, and a permanent cell cycle arrest, presumably due to activation of the spindle checkpoint. Remarkably, expression of a version of Scc3-SA2 whose mitotic phosphorylation sites have been mutated to alanine alleviates the precocious loss of sister chromatid cohesion and the mitotic arrest of cells lacking shugoshin. These data suggest that shugoshin prevents phosphorylation of cohesin's Scc3-SA2 subunit at centromeres during mitosis. This ensures that cohesin persists at centromeres until activation of separase causes cleavage of its alpha kleisin subunit. Centromeric

  7. Sequential loading of cohesin subunits during the first meiotic prophase of grasshoppers.

    Directory of Open Access Journals (Sweden)

    Ana M Valdeolmillos

    2007-02-01

    Full Text Available The cohesin complexes play a key role in chromosome segregation during both mitosis and meiosis. They establish sister chromatid cohesion between duplicating DNA molecules during S-phase, but they also have an important role during postreplicative double-strand break repair in mitosis, as well as during recombination between homologous chromosomes in meiosis. An additional function in meiosis is related to the sister kinetochore cohesion, so they can be pulled by microtubules to the same pole at anaphase I. Data about the dynamics of cohesin subunits during meiosis are scarce; therefore, it is of great interest to characterize how the formation of the cohesin complexes is achieved in order to understand the roles of the different subunits within them. We have investigated the spatio-temporal distribution of three different cohesin subunits in prophase I grasshopper spermatocytes. We found that structural maintenance of chromosome protein 3 (SMC3 appears as early as preleptotene, and its localization resembles the location of the unsynapsed axial elements, whereas radiation-sensitive mutant 21 (RAD21 (sister chromatid cohesion protein 1, SCC1 and stromal antigen protein 1 (SA1 (sister chromatid cohesion protein 3, SCC3 are not visualized until zygotene, since they are located in the synapsed regions of the bivalents. During pachytene, the distribution of the three cohesin subunits is very similar and all appear along the trajectories of the lateral elements of the autosomal synaptonemal complexes. However, whereas SMC3 also appears over the single and unsynapsed X chromosome, RAD21 and SA1 do not. We conclude that the loading of SMC3 and the non-SMC subunits, RAD21 and SA1, occurs in different steps throughout prophase I grasshopper meiosis. These results strongly suggest the participation of SMC3 in the initial cohesin axis formation as early as preleptotene, thus contributing to sister chromatid cohesion, with a later association of both RAD21

  8. A critical view to explanations for the maximal value of 50 % of genetic recombination Críticas a las explicaciones del máximo de 50 % de recombinación genética

    Directory of Open Access Journals (Sweden)

    CARLOS Y VALENZUELA

    2001-03-01

    Full Text Available The maximal value of 50 % of genetic recombination (RF = recombination fraction between two linked gene loci has been explained by two models: (i the restriction of crossovers to only two of the four chromatids of a tetrad (tetrad model; (ii the limit of the occurrence of an odd number of crossovers between two loci, when the expected number of crossovers tends to infinite (odd-even model. This article shows that (i is wrong. If tetrads were responsible for the maximal 50 % RF, sister chromatid exchanges (SCE should display a maximal 100 % RF. In mammalian CHO cells we found that SCE yield a maximal 50 % recombination. Also, we demonstrated that the maximal 50 % RF for tetrads occurs because the sum of odd order coefficients in the binomial distribution is equal to the sum of even order coefficients. At the end of meiosis the two chromatids of a chromosome that receives K crossovers are separated. Then K breaks should distribute into two chromatids. Thus, the expected number of breaks per chromatid distributes, when K is large, in 50 % of chromatids having an even number of breaks (RF = 0 and 50 % having an odd number (RF = 1, irrespective of tetrads, hexads, octads or more complex meiotic chromosome configurationsEl máximo de 50 % de recombinación genética (RF entre dos loci ligados ha sido explicado por dos modelos. (i la restricción de los entrecruzamientos a dos de las cuatro cromátidas de una tétrada (modelo de tétrada; (ii el límite de la ocurrencia de un número impar de entrecruzamientos entre los dos loci, cuando el número esperado de entrecruzamientos tiende a infinito (modelo par-impar. Este artículo muestra que (i es erróneo, ya que, si la tétrada fuera responsable del máximo de 50 % de RF, el intercambio de cromátidas hermanas (SCE debería alcazar el 100 % de recombinación y esto no se da en células CHO, en las que encontramos un máximo de 50 %. Además, demostramos que el máximo de 50 % RF para las t

  9. The coiled coils of cohesin are conserved in animals, but not in yeast.

    Directory of Open Access Journals (Sweden)

    Glenn E White

    Full Text Available BACKGROUND: The SMC proteins are involved in DNA repair, chromosome condensation, and sister chromatid cohesion throughout Eukaryota. Long, anti-parallel coiled coils are a prominent feature of SMC proteins, and are thought to serve as spacer rods to provide an elongated structure and to separate domains. We reported recently that the coiled coils of mammalian condensin (SMC2/4 showed moderate sequence divergence (approximately 10-15% consistent with their functioning as spacer rods. The coiled coils of mammalian cohesins (SMC1/3, however, were very highly constrained, with amino acid sequence divergence typically <0.5%. These coiled coils are among the most highly conserved mammalian proteins, suggesting that they make extensive contacts over their entire surface. METHODOLOGY/PRINCIPAL FINDINGS: Here, we broaden our initial analysis of condensin and cohesin to include additional vertebrate and invertebrate organisms and multiple species of yeast. We found that the coiled coils of SMC1/3 are highly constrained in Drosophila and other insects, and more generally across all animal species. However, in yeast they are no more constrained than the coils of SMC2/4 and Ndc80/Nuf2p, suggesting that they are serving primarily as spacer rods. CONCLUSIONS/SIGNIFICANCE: SMC1/3 functions for sister chromatid cohesion in all species. Since its coiled coils apparently serve only as spacer rods in yeast, it is likely that this is sufficient for sister chromatid cohesion in all species. This suggests an additional function in animals that constrains the sequence of the coiled coils. Several recent studies have demonstrated that cohesin has a role in gene expression in post-mitotic neurons of Drosophila, and other animal cells. Some variants of human Cornelia de Lange Syndrome involve mutations in human SMC1/3. We suggest that the role of cohesin in gene expression may involve intimate contact of the coiled coils of SMC1/3, and impose the constraint on sequence

  10. Immunogold electron microscopy and confocal analyses reveal distinctive patterns of histone H3 phosphorylation during mitosis in MCF-7 cells.

    Science.gov (United States)

    Yan, Yitang; Cummings, Connie A; Sutton, Deloris; Yu, Linda; Castro, Lysandra; Moore, Alicia B; Gao, Xiaohua; Dixon, Darlene

    2016-04-01

    Histone phosphorylation has a profound impact on epigenetic regulation of gene expression, chromosome condensation and segregation, and maintenance of genome integrity. Histone H3 Serine 10 is evolutionally conserved and heavily phosphorylated during mitosis. To examine Histone H3 Serine 10 phosphorylation (H3S10ph) dynamics in mitosis, we applied immunogold labeling and confocal microscopy to visualize H3S10ph expression in MCF-7 cells. Confocal observations showed that MCF-7 cells had abundant H3S10ph expression in prophase and metaphase. In anaphase, the H3S10ph expression was significantly decreased and displayed only sparsely localized staining that mainly associated with the chromatid tips. We showed that immunogold bead density distribution followed the H3S10ph expression patterns observed in confocal analysis. At a higher magnification in metaphase, the immunogold beads were readily visible and the bead distribution along the condensed chromosomes was distinctive, indicating the specificity and reliability of the immunogold staining procedure. In anaphase, the beads were found to distribute focally in specific regions of chromatids, reinforcing the confocal observations of differential H3 phosphorylation. To our knowledge, this is the first report to show the specific H3S10ph expression with an immunogold technique and transmission electron microscopy. Additionally, with confocal microscopy, we analyzed H3S10ph expression in an immortalized cell line derived from benign uterine smooth muscle tumor cells. H3S10ph epitope was expressed more abundantly during anaphase in the benign tumor cells, and there was no dramatic differential expression within the condensed chromatid clusters as observed in MCF-7 cells. The differences in H3S10ph expression pattern and dynamics may contribute to the differential proliferative potential between benign tumor cells and MCF-7 cells.

  11. Genome-wide analysis of heteroduplex DNA in mismatch repair-deficient yeast cells reveals novel properties of meiotic recombination pathways.

    Directory of Open Access Journals (Sweden)

    Emmanuelle Martini

    2011-09-01

    Full Text Available Meiotic DNA double-strand breaks (DSBs initiate crossover (CO recombination, which is necessary for accurate chromosome segregation, but DSBs may also repair as non-crossovers (NCOs. Multiple recombination pathways with specific intermediates are expected to lead to COs and NCOs. We revisited the mechanisms of meiotic DSB repair and the regulation of CO formation, by conducting a genome-wide analysis of strand-transfer intermediates associated with recombination events. We performed this analysis in a SK1 × S288C Saccharomyces cerevisiae hybrid lacking the mismatch repair (MMR protein Msh2, to allow efficient detection of heteroduplex DNAs (hDNAs. First, we observed that the anti-recombinogenic activity of MMR is responsible for a 20% drop in CO number, suggesting that in MMR-proficient cells some DSBs are repaired using the sister chromatid as a template when polymorphisms are present. Second, we observed that a large fraction of NCOs were associated with trans-hDNA tracts constrained to a single chromatid. This unexpected finding is compatible with dissolution of double Holliday junctions (dHJs during repair, and it suggests the existence of a novel control point for CO formation at the level of the dHJ intermediate, in addition to the previously described control point before the dHJ formation step. Finally, we observed that COs are associated with complex hDNA patterns, confirming that the canonical double-strand break repair model is not sufficient to explain the formation of most COs. We propose that multiple factors contribute to the complexity of recombination intermediates. These factors include repair of nicks and double-stranded gaps, template switches between non-sister and sister chromatids, and HJ branch migration. Finally, the good correlation between the strand transfer properties observed in the absence of and in the presence of Msh2 suggests that the intermediates detected in the absence of Msh2 reflect normal intermediates.

  12. Lack of Bystander Effects From High LET Radiation For Early Cytogenetic Endpoints.

    Energy Technology Data Exchange (ETDEWEB)

    Groesser, Torsten; Cooper, Brian; Rydberg, Bjorn

    2008-05-07

    The aim of this work was to study radiation-induced bystander effects for early cytogenetic end points in various cell lines using the medium transfer technique after exposure to high- and low-LET radiation. Cells were exposed to 20 MeV/ nucleon nitrogen ions, 968 MeV/nucleon iron ions, or 575 MeV/nucleon iron ions followed by transfer of the conditioned medium from the irradiated cells to unirradiated test cells. The effects studied included DNA double-strand break induction, {gamma}-H2AX focus formation, induction of chromatid breaks in prematurely condensed chromosomes, and micronucleus formation using DNA repair-proficient and -deficient hamster and human cell lines (xrs6, V79, SW48, MO59K and MO59J). Cell survival was also measured in SW48 bystander cells using X rays. Although it was occasionally possible to detect an increase in chromatid break levels using nitrogen ions and to see a higher number of {gamma}-H2AX foci using nitrogen and iron ions in xrs6 bystander cells in single experiments, the results were not reproducible. After we pooled all the data, we could not verify a significant bystander effect for any of these end points. Also, we did not detect a significant bystander effect for DSB induction or micronucleus formation in these cell lines or for clonogenic survival in SW48 cells. The data suggest that DNA damage and cytogenetic changes are not induced in bystander cells. In contrast, data in the literature show pronounced bystander effects in a variety of cell lines, including clonogenic survival in SW48 cells and induction of chromatid breaks and micronuclei in hamster cells. To reconcile these conflicting data, it is possible that the epigenetic status of the specific cell line or the precise culture conditions and medium supplements, such as serum, may be critical for inducing bystander effects.

  13. 4-nitroquinoline-1-oxide-induced mutagen sensitivity and risk of cutaneous melanoma: a case-control analysis.

    Science.gov (United States)

    Wang, Li-E; Li, Chunying; Xiong, Ping; Gershenwald, Jeffrey E; Prieto, Victor G; Duvic, Madeleine; Lee, Jeffrey E; Grimm, Elizabeth A; Hsu, Tao C; Wei, Qingyi

    2016-04-01

    Mutagen sensitivity assay, which measures the enhanced cellular response to DNA damage induced in vitro by mutagens/carcinogens, has been used in the study of cancer susceptibility. 4-Nitroquinoline-1-oxide (4-NQO), an ultraviolet (UV) radiation-mimetic chemical, can produce chromosomal breaks in mammalian cells and induce cancer. Given the potential role of 4-NQO as the experimental mutagen substituting for UV as the etiological carcinogen of cutaneous melanoma (CM), we tested the hypothesis that cellular sensitivity to 4-NQO is associated with the risk of developing CM in a case-control study of 133 patients with primary CM and 176 cancer-free controls. Short-term blood cultures were treated with 4-NQO at a final concentration of 10 μmol/l for 24 h and scored chromatid breaks in 50 well-spread metaphases. Multivariate logistic regression was used to calculate odds ratios and 95% confidence intervals. We found that the log-transformed frequency of chromatid breaks was significantly higher in 133 patients than in 176 controls (P=0.004) and was associated with an increased risk for CM (adjusted odds ratio=1.78, 95% confidence interval: 1.12-2.84) after adjustment for age and sex. Moreover, as the chromatid break values increased, the risk for CM increased in a dose-dependent manner (P(trend)=0.003). Further analysis explored a multiplicative interaction between the sensitivity to 4-NQO and a family history of skin cancer (P(interaction)=0.004) on the risk of CM. Therefore, our findings suggest that sensitivity to 4-NQO may be a risk factor for the risk of CM, which is more sensitive than UV-induced chromotid breaks.

  14. Unique double de novo structural rearrangements for chromosome 11 with 46,XX,del(11)(q13q23)/46,XX,inv dup(11)(q13q23) in an infant with minor congenital abnormalities and delayed development

    Energy Technology Data Exchange (ETDEWEB)

    Tharapel, A.T.; Zhao, J.; Smith, M.E. [Univ. of Tennessee, Memphis, TN (United States)] [and others

    1994-09-01

    Reported here is a patient with two most unusual structural rearrangements, both involving chromosome 11. The first cell line showed an interstitial deletion of a chromosome 11 with a 46,XX,del(11)(q13q23) chromosome complement. In the second cell line, one of the chromosome 11s had a duplication for the exact region, (11)(q13q23), that was deleted in the first cell line. This duplication also appeared to be inverted with karyotype 46,XX,inv dup(11)(q13q23). Interestingly, chromosome analysis did not reveal a normal cell line and the two abnormal cell lines were present in a 1:1 ratio. Parental chromosome analyses showed normal karyotypes. The patient was referred for genetic evaluation because of developmental delay. Minor congenital anomalies presented on physical examination included: weight and height at or below the 5th percentile, microcephaly, downward slanting palpebral fissures, severe clinodactyly of one toe, bilateral short fifth fingers and a broad based gait. Results of the MRI and urine metabolic screen were normal. Two hypotheses are advanced to explain the origin of the abnormality. It is most likely that the abnormality arose as a postzygotic event at the very early zygotic division. During the first DNA synthesis after fertilization and before the zygotic division, DNA synthesis errors could result in two chromatids, one with a deletion and the other with a duplication. It is also possible that after the DNA synthesis prior to the first cell division, the chromatids of the same chromosome 11 for unknown reasons were involved in uneven double somatic crossing over events resulting in deleted and duplicated chromatids, respectively. The 1:1 cell ratio found in the patient and the apparent non-existence of a normal cell line further suggest that the origin of the abnormality was post-zygotic.

  15. The SUMO protease SENP1 is required for cohesion maintenance and mitotic arrest following spindle poison treatment

    International Nuclear Information System (INIS)

    Highlights: ► SENP1 knockout chicken DT40 cells are hypersensitive to spindle poisons. ► Spindle poison treatment of SENP1−/− cells leads to increased mitotic slippage. ► Mitotic slippage in SENP1−/− cells associates with apoptosis and endoreplication. ► SENP1 counteracts sister chromatid separation during mitotic arrest. ► Plk1-mediated cohesion down-regulation is involved in colcemid cytotoxicity. -- Abstract: SUMO conjugation is a reversible posttranslational modification that regulates protein function. SENP1 is one of the six SUMO-specific proteases present in vertebrate cells and its altered expression is observed in several carcinomas. To characterize SENP1 role in genome integrity, we generated Senp1 knockout chicken DT40 cells. SENP1−/− cells show normal proliferation, but are sensitive to spindle poisons. This hypersensitivity correlates with increased sister chromatid separation, mitotic slippage, and apoptosis. To test whether the cohesion defect had a causal relationship with the observed mitotic events, we restored the cohesive status of sister chromatids by introducing the TOP2α+/− mutation, which leads to increased catenation, or by inhibiting Plk1 and Aurora B kinases that promote cohesin release from chromosomes during prolonged mitotic arrest. Although TOP2α is SUMOylated during mitosis, the TOP2α+/− mutation had no obvious effect. By contrast, inhibition of Plk1 or Aurora B rescued the hypersensitivity of SENP1−/− cells to colcemid. In conclusion, we identify SENP1 as a novel factor required for mitotic arrest and cohesion maintenance during prolonged mitotic arrest induced by spindle poisons.

  16. Higher frequencies of chromosomal aberrations in lymphocytes of children with acute lymphoblastic leukemia after in vitro gamma irradiation

    Directory of Open Access Journals (Sweden)

    A Ramyar

    2012-12-01

    Full Text Available Background: Acute lymphoblastic leukemia (ALL is the most common malignancy in childhood, characterized by excess lymphoblasts, and immature white blood cells that are continuously multiplying and overproducing in the bone marrow. The aim of this investigation was to measure the sensitivity of lymphocytes against gamma irradiation in patients with acute lymphoblastic leukemia, and also find out the effect of such irradiations in causing chromosomal abnormalities.Methods: In this investigation performed between April 2010 and July 2011, at the Department of Genetics, Cancer Institute of Iran, we studied the effects of gamma irradiation on the lymphocytes of 20 children with acute lymphoblastic leukemia. The lymphocytes of 30 healthy donors were used to establish as a normal response to gamma irradiation and seven age-matched ataxia telangiectasia patients were recruited as positive control. The chromosomal radiosensitivity was assessed with the G2- and the G0-assay. We compared the mean number of chromosomal abnormalities such as chromosome and chromatid breakages, chromosome and chromatid gaps, and chromatid exchanges in one-hundred metaphases of patients and control groups.Results: The frequency of chromosomal aberrations was statistically higher among patients with acute lymphoblastic leukemia than the normal controls (P<0.01. In total, 65% of the patients were sensitive to gamma irradiation, but the remaining 35% were similar to the normal controls. Patients with ataxia telangiectasia showed the highest sensitivity to gamma irradiation (P=0.001.Conclusion: Our results showed that a high percentage of patients with acute lymphoblastic leukemia were sensitive to irradiation, meaning that maximum care should be taken during their treatment to avoid unnecessary X-rays or radiotherapies.

  17. The SUMO protease SENP1 is required for cohesion maintenance and mitotic arrest following spindle poison treatment

    Energy Technology Data Exchange (ETDEWEB)

    Era, Saho [Fondazione IFOM, Istituto FIRC di Oncologia Molecolare, IFOM-IEO campus, Via Adamello 16, 20139 Milan (Italy); Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501 (Japan); Abe, Takuya; Arakawa, Hiroshi [Fondazione IFOM, Istituto FIRC di Oncologia Molecolare, IFOM-IEO campus, Via Adamello 16, 20139 Milan (Italy); Kobayashi, Shunsuke [Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501 (Japan); Szakal, Barnabas [Fondazione IFOM, Istituto FIRC di Oncologia Molecolare, IFOM-IEO campus, Via Adamello 16, 20139 Milan (Italy); Yoshikawa, Yusuke; Motegi, Akira; Takeda, Shunichi [Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501 (Japan); Branzei, Dana, E-mail: dana.branzei@ifom.eu [Fondazione IFOM, Istituto FIRC di Oncologia Molecolare, IFOM-IEO campus, Via Adamello 16, 20139 Milan (Italy)

    2012-09-28

    Highlights: Black-Right-Pointing-Pointer SENP1 knockout chicken DT40 cells are hypersensitive to spindle poisons. Black-Right-Pointing-Pointer Spindle poison treatment of SENP1{sup -/-} cells leads to increased mitotic slippage. Black-Right-Pointing-Pointer Mitotic slippage in SENP1{sup -/-} cells associates with apoptosis and endoreplication. Black-Right-Pointing-Pointer SENP1 counteracts sister chromatid separation during mitotic arrest. Black-Right-Pointing-Pointer Plk1-mediated cohesion down-regulation is involved in colcemid cytotoxicity. -- Abstract: SUMO conjugation is a reversible posttranslational modification that regulates protein function. SENP1 is one of the six SUMO-specific proteases present in vertebrate cells and its altered expression is observed in several carcinomas. To characterize SENP1 role in genome integrity, we generated Senp1 knockout chicken DT40 cells. SENP1{sup -/-} cells show normal proliferation, but are sensitive to spindle poisons. This hypersensitivity correlates with increased sister chromatid separation, mitotic slippage, and apoptosis. To test whether the cohesion defect had a causal relationship with the observed mitotic events, we restored the cohesive status of sister chromatids by introducing the TOP2{alpha}{sup +/-} mutation, which leads to increased catenation, or by inhibiting Plk1 and Aurora B kinases that promote cohesin release from chromosomes during prolonged mitotic arrest. Although TOP2{alpha} is SUMOylated during mitosis, the TOP2{alpha}{sup +/-} mutation had no obvious effect. By contrast, inhibition of Plk1 or Aurora B rescued the hypersensitivity of SENP1{sup -/-} cells to colcemid. In conclusion, we identify SENP1 as a novel factor required for mitotic arrest and cohesion maintenance during prolonged mitotic arrest induced by spindle poisons.

  18. Down syndrome due to a recombination of a chromosome 21 paracentric inversion in 1 of 2 cases with a review of paracentric recombinants

    Energy Technology Data Exchange (ETDEWEB)

    Jewett, T.; Rao, P.N.; Berry, M. [Wake Forest Univ., Winston-Salem, NC (United States)] [and others

    1994-09-01

    We recently identified 2 paracentric inversions (PAI) of chromosome 21. Case 1 was identified prenatally and paternally inherited: 46,XY,inv(21)(q21.2q22.13). The outcome is pending. Case 2 was a newborn male infant with clinical features of Down syndrome and an apparent inversion-duplication within chromosome 21. Parental chromosome analysis showed a maternal PAI: 46,XX,inv(21)(q21.2q22.3). The resulting child`s karyotype was: 46,XY,rec(21)(pter{yields}q21.2::q22.3{yields}q21.2::q22.3{yields}pter). Duplication of chromosome region q22.3{yields}qter was confirmed by FISH using a Down syndrome region specific probe (Cambio). Cytologically, the cornerstone of meiotic recombination from a paracentric inversion is the {open_quotes}reverse loop{close_quotes} model. In this model, a crossover event in the inversion loop results in the formation of gametes carrying either a dicentric chromatid, an acentric fragment, a normal chromatid or a chromatid with an inversion. However, a literature review of 326 PAI identified only 2 dicentrics and 15 other recombinants: 1 duplication/deletion; 6 deletions; 8 duplications. A U-type exchange model during meiosis within the inversion loop may best account for duplication/deletion recombinants. In contrast, the recombination in our case 2 would have occurred outside the loop. It is possible that no single explanation for PAI recombination may account for all outcomes. Alternative models of PAI recominational events will be presented. The literature suggests a low risk for prenatal loss due to abnormal PAI recombinants. In our review, viable offspring with recombinant chromosomes occurred in 3.8% of the PAI. Considering the potential for an increased incidence of recombination, prenatal diagnosis for all PAI carriers is warranted.

  19. Effects of phytoestrogen genistein on cytogenetic biomarkers in postmenopausal women: 1 year randomized, placebo-controlled study.

    Science.gov (United States)

    Atteritano, Marco; Pernice, Francesco; Mazzaferro, Susanna; Mantuano, Stefania; Frisina, Alessia; D'Anna, Rosario; Cannata, Maria Letizia; Bitto, Alessandra; Squadrito, Francesco; Frisina, Nicola; Buemi, Michele

    2008-07-28

    To evaluate in a twelve-month, randomized placebo-controlled study whether pure administration of phytoestrogen genistein (54 mg/day) might reduce cytogenetic biomarkers in peripheral lymphocytes of postmenopausal women. A total of 57 postmenopausal women met the criteria and were randomly assigned to receive phytoestrogen genistein (n = 30) or placebo (n = 27). There was no significant difference in age, length of time since menopause or body mass index between the two groups. After one year, plasma genistein level was 0.14 +/- 0.01 micromol/L in the control group and 0.72 +/- 0.08 micromol/L in the genistein group (P < 0.0001). At baseline, sister chromatid exchange rate was 4.97 +/- 2.17 in the control group and 4.96 +/- 1.83 in the genistein group (P = 0.89). After one year, sister chromatid exchange rate was 4.96 +/- 2.16 in the control group and 3.98 +/- 1.14 in the genistein group (P < 0.05). High frequency cells count was 3% in the genistein group and 5% in the control group (P < 0.05) at the end of the study. Chromosomal aberration frequency was 5.55% in the control group at time 0 and 5.75% in the genistein group; after one year, the figures were 5.86% in the control group and 4.5% in the genistein group (P < 0.05). After one year, there was a negative relationship between sister chromatid exchange rate and plasma levels (r = - 0.43; P < 0.05) in the genistein group. Phytoestrogen genistein has been shown in postmenopausal women to be effective in the reduction of cytogenetic biomarkers. The protective effect on genomic damage appears to be a particularly promising tool in reducing the risk of cancer.

  20. The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability

    OpenAIRE

    Noonan James P; Yankiwski Victor; Neff Norma F

    2001-01-01

    Abstract Background Bloom syndrome is a rare cancer-prone disorder in which the cells of affected persons have a high frequency of somatic mutation and genomic instability. Bloom syndrome cells have a distinctive high frequency of sister chromatid exchange and quadriradial formation. BLM, the protein altered in BS, is a member of the RecQ DNA helicase family, whose members share an average of 40% identity in the helicase domain and have divergent N-terminal and C-terminal flanking regions of ...

  1. How unfinished business from S-phase affects mitosis and beyond

    DEFF Research Database (Denmark)

    Mankouri, H.W.; Huttner, D.; Hickson, I.D.

    2013-01-01

    The eukaryotic cell cycle is conventionally viewed as comprising several discrete steps, each of which must be completed before the next one is initiated. However, emerging evidence suggests that incompletely replicated, or unresolved, chromosomes from S-phase can persist into mitosis, where...... they present a potential threat to the faithful segregation of sister chromatids. In this review, we provide an overview of the different classes of loci where this 'unfinished S-phase business' can lead to a variety of cytogenetically distinct DNA structures throughout the various steps of mitosis...

  2. Characterization of the NTPR and BD1 interacting domains of the human PICH-BEND3 complex

    DEFF Research Database (Denmark)

    Pitchai, Ganesha P; Hickson, Ian D; Streicher, Werner;

    2016-01-01

    Chromosome integrity depends on DNA structure-specific processing complexes that resolve DNA entanglement between sister chromatids. If left unresolved, these entanglements can generate either chromatin bridging or ultrafine DNA bridging in the anaphase of mitosis. These bridge structures...... are defined by the presence of the PICH protein, which interacts with the BEND3 protein in mitosis. To obtain structural insights into PICH-BEND3 complex formation at the atomic level, their respective NTPR and BD1 domains were cloned, overexpressed and crystallized using 1.56 M ammonium sulfate...

  3. Three wise centromere functions: see no error, hear no break, speak no delay.

    Science.gov (United States)

    Tanaka, Tomoyuki U; Clayton, Lesley; Natsume, Toyoaki

    2013-12-01

    The main function of the centromere is to promote kinetochore assembly for spindle microtubule attachment. Two additional functions of the centromere, however, are becoming increasingly clear: facilitation of robust sister-chromatid cohesion at pericentromeres and advancement of replication of centromeric regions. The combination of these three centromere functions ensures correct chromosome segregation during mitosis. Here, we review the mechanisms of the kinetochore-microtubule interaction, focusing on sister-kinetochore bi-orientation (or chromosome bi-orientation). We also discuss the biological importance of robust pericentromeric cohesion and early centromere replication, as well as the mechanisms orchestrating these two functions at the microtubule attachment site.

  4. Functions of spindle check-point and its relationship to chromosome instability

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    It is generally believed that the equal distribution of genetic materials to two daughter cells during mitosis is the key to cell health and development. During the dynamic process, spindle checkpoint plays a very important role in chromosome movements and final sister chromatid separation. The equal and precise segregation of chromosomes contributes to the genomic stability while aberrant separations result in chromosome instability that causes pathogenesis of certain diseases such as Down's syndrome and cancers. Kinetochore and its regulatory proteins consist of the spindle checkpoint and determine the spatial and temporal orders of chromosome segregation.

  5. Cytogenetic damage and occupational exposure. I. Exposure to stone dust.

    Science.gov (United States)

    Sobti, R C; Bhardwaj, D K

    1991-10-01

    Cytogenetic investigations were carried out on 50 workers exposed to stone dust in a stone crusher industry and on 25 control subjects never exposed to such dust. The frequency of chromosomal aberrations and sister chromatid exchanges in exposed individuals was significantly higher than that in controls (P less than 0.01). The cytogenetic indices demonstrated a clear dependence on the working environment. The effect of smoking and/or alcoholic habits coupled with exposure to stone dust has also been investigated. The results indicate that the mutagenic risk in the working environment is probably associated with silica dust in the area. PMID:1655400

  6. Cytogenetic damage and occupational exposure. 1. Exposure to stone dust

    Energy Technology Data Exchange (ETDEWEB)

    Sobti, R.C.; Bhardwaj, D.K. (Panjab Univ., Chandigarh (India))

    1991-10-01

    Cytogenetic investigations were carried out on 50 workers exposed to stone dust in a stone crusher industry and on 25 control subjects never exposed to such dust. The frequency of chromosomal aberrations and sister chromatid exchanges in exposed individuals was significantly higher than that in controls. The cytogenetic indices demonstrated a clear dependence on the working environment. The effect of smoking and/or alcoholic habits coupled with exposure to stone dust has also been investigated. The results indicate that the mutagenic risk in the working environment is probably associated with silica dust in the area.

  7. Evaluation of genotoxic effects of the herbicide dicamba using in vivo and in vitro test systems

    International Nuclear Information System (INIS)

    The genotoxic effects of the herbicide dicamba have been studied by measuring (1) the unwinding rate of liver DNA from intraperitoneally treated rats (fluorimetric assay); (2) DNA repair as unscheduled DNA synthesis (UDS) induced in cultured human peripheral blood lymphocytes (HPBL); and (3) sister chromatid exchanges (SCE) in HPBL. Results show that dicamba is capable of inducing DNA damage since it significantly increases the unwinding rate of rat liver DNA in vivo and also induces UDS in HPBL in vitro in the presence of exogenous metabolic activation (S-9 mix). Furthermore, dicamba causes a very slight increase in SCE frequency in HPBL in vitro

  8. Effect of pretreatment with venom of Apis mellifera bees on the yield of gamma-ray induced chromosome aberrations in human blood lymphocytes

    International Nuclear Information System (INIS)

    Venom of the honey bee Apis mellifera induced a protective effect against the induction of dicentric chromosomes by gamma radiation (2.0 Gy) in human peripheral blood lymphocytes when the cultures were treated with 0.00015 μl venom/1 ml medium 6 h before irradiation. In cultures to which the venom was added immediately before irradiation with 0.25, 1.0 and 2.0 Gy, no significant differences in number of dicentric chromosomes induced was observed when compared to cultures submitted to irradiation only. The venom did not induce clastogenic effects nor did it increase the frequency of sister chromatid exchanges. (author)

  9. Cohesin and the nucleolus constrain the mobility of spontaneous repair foci.

    Science.gov (United States)

    Dion, Vincent; Kalck, Véronique; Seeber, Andrew; Schleker, Thomas; Gasser, Susan M

    2013-11-01

    The regulation of chromatin mobility in response to DNA damage is important for homologous recombination in yeast. Anchorage reduces rates of recombination, whereas increased chromatin mobility correlates with more efficient homology search. Here we tracked the mobility and localization of spontaneous S-phase lesions bound by Rad52, and find that these foci have reduced movement, unlike enzymatically induced double-strand breaks. Moreover, spontaneous repair foci are positioned in the nuclear core, abutting the nucleolus. We show that cohesin and nucleolar integrity constrain the mobility of these foci, consistent with the notion that spontaneous, S-phase damage is preferentially repaired from the sister chromatid.

  10. Research on spontaneously emerged chromosomal aberrations in the periphery blood lymphocytes in cattle ('Busa' breed).

    Science.gov (United States)

    Hasanbasić, Danica; Rukavina, Dunja; Hodzić, Aida; Brka, Muhamed; Vegara, Mensur; Hamamdzić, Muhidin

    2007-11-01

    Knowledge of spontaneous aberrations, namely, of their frequency in non-irradiated cells is of paramount importance not only in cytogenetic research, but also in contemporary animal production. The paper deals with research on spontaneously emerged chromosomal aberrations in the peripheral blood lymphocytes in the cattle of 'Busa' breed. To obtain metaphase chromosomes the conventional method of lymphocyte cultivation was used, albeit slightly modified and adapted to the examined animals and the laboratory conditions. The research findings indicate that a certain percent of spontaneously emerged chromosomal aberrations of chromatid type (gap and break) have been found in the peripheral blood lymphocytes in the cattle of 'Busa' breed.

  11. Antiviral Activity of Metal-Containing Polymers—Organotin and Cisplatin-Like Polymers

    Directory of Open Access Journals (Sweden)

    Girish Barot

    2011-05-01

    Full Text Available Polymers containing platinum and to a lesser extent tin, have repeatedly demonstrated antitumor activity in vitro and in vivo against a variety of cell and tumor types. The mechanisms responsible for the antitumor activity include inducing a delay in cell proliferation and sister chromatid exchanges blocking tumor growth. As most DNA and some RNA viruses require, and even induce, infected cells to initiate DNA replication and subsequent cell division, compounds with antitumor activity will very likely also possess antiviral activity. This article examines the use of metal-containing polymers as a novel class of antivirals.

  12. A direct role of Mad1 in the spindle assembly checkpoint beyond Mad2 kinetochore recruitment

    DEFF Research Database (Denmark)

    Kruse, Thomas; Larsen, Marie Sofie Yoo; Sedgwick, Garry G;

    2014-01-01

    The spindle assembly checkpoint (SAC) ensures accurate chromosome segregation by delaying entry into anaphase until all sister chromatids have become bi-oriented. A key component of the SAC is the Mad2 protein, which can adopt either an inactive open (O-Mad2) or active closed (C-Mad2) conformation...... in the SAC beyond recruitment of C-Mad2 to kinetochores has not yet been addressed. Here, we show that Mad1 is required for mitotic arrest even when C-Mad2 is artificially recruited to kinetochores, indicating that it has indeed an additional function in promoting the checkpoint. The C-terminal globular...

  13. The reactivity of plant, murine and human genome to electron beam irradiation

    International Nuclear Information System (INIS)

    A broad spectrum of chromosomal rearrangements is described in plants (Allium cepa), mouse (Mus musculus domestics) and in humans (Homo sapiens sapiens), following in vivo and in vitro beta irradiation. Irradiations were performed at EAL, using a 2.998 GHz traveling-wave electron accelerator. The primary effect of electron beam irradiation is chromosomal breakage followed up by a variety of chromosomal rearrangements i.e. chromosomal aberrations represented mainly by chromatid gaps, deletions, ring chromosomes, dicentrics, translocations, complex chromosomal interchanges, acentric fragments and double minutes (DM). The clastogenic effects were associated in some instances with cell sterilization (i.e. cell death)

  14. Pds5B is required for cohesion establishment and Aurora B accumulation at centromeres

    OpenAIRE

    Carretero, María; Ruiz-Torres, Miguel; Rodríguez-Corsino, Miriam; Barthelemy, Isabel; Losada, Ana

    2013-01-01

    Cohesin mediates sister chromatid cohesion and contributes to the organization of interphase chromatin through DNA looping. In vertebrate somatic cells, cohesin consists of Smc1, Smc3, Rad21, and either SA1 or SA2. Three additional factors Pds5, Wapl, and Sororin bind to cohesin and modulate its dynamic association with chromatin. There are two Pds5 proteins in vertebrates, Pds5A and Pds5B, but their functional specificity remains unclear. Here, we demonstrate that Pds5 proteins are essential...

  15. [Cohesion inside eu- and heterochromatin in human cells].

    Science.gov (United States)

    Cherepaninets, V D; Zhironkina, O A; Strelkova, O S; Kurchashova, S Iu; Kireev, I I

    2015-01-01

    It is considered that sister chromatids are held together immediately after replication by special protein complex--cohesin that consists of Smc1--Smc3 core dimer and two additional subunits, Scc1 and Scc3. This process is called cohesion. We have characterized binding of cohesin complex to early- and late-replicated chromatin at different stages of the cell cycle in human cells HeLa and HT1080 using superresolution microscopy (based on Structural ilumination microscopy--SIM) and immunoelectron microscopy. It has been shown that cohesins do not play important role in cohesion of heterochromatic domains, but they provide cohesion and organization of subdomains in euchromatic regions. PMID:25872375

  16. Cytogenetic effects of aqueous extracts of the medicinal plant paico (chenopodium multifidum L.).

    Science.gov (United States)

    Gadano, A; Gurni, A; Nigro López, M; López, P; Gratti, A; van Baren, C; Ferraro, G; Carballo, M

    2000-01-01

    The cytogenetic effects of aqueous extracts of Chenopodium multifidum L. (Paico) were determined by addition of the extracts and fractions to human lymphocyte cultures. Toxicity was evaluated by analysis of chromosomal aberrations (CA), sister chromatid exchange (SCE), mitotic (MI) and replication (RI) indexes. The results showed an increase in CA frequency in cultures exposed to infusion decoction, no modification in the CPK values either in the decoction or in the infusion, and a decrease in the MI of lymphocyte cultures exposed to the decoction. These results suggested genotoxic effects of "Paico" aqueous extracts. PMID:21214432

  17. Low concentrations of caffeine induce asymmetric cell division as observed in vitro by means of the CBMN-assay and iFISH.

    Science.gov (United States)

    Hatzi, Vasiliki I; Karakosta, Maria; Barszczewska, Katarzyna; Karachristou, Ioanna; Pantelias, Gabriel; Terzoudi, Georgia I

    2015-11-01

    The dual role of caffeine as a chromosomal damage inducer and G2/M-checkpoint abrogator is well known but it is observed mainly at relatively high concentrations. At low concentrations, caffeine enhances the cytogenetic effects of several carcinogens and its intake during pregnancy has been recently reported to cause adverse birth outcomes. Interestingly, a threshold below which this association is not apparent was not identified. Since chromosomal abnormalities and aneuploidy are the major genetic etiologies of spontaneous abortions and adverse birth outcomes, we re-evaluate here the effects of caffeine at the cytogenetic level and propose a model for the mechanisms involved. Our hypothesis is that low caffeine concentrations affect DNA replication and cause chromosomal aberrations and asymmetric cell divisions not easily detected at metaphase since damaged cells are delayed during their G2/M-phase transition and the low caffeine concentrations cannot abrogate the G2-checkpoint. To test this hypothesis, caffeine-induced chromatid breaks and micronuclei in peripheral blood lymphocytes (PBLs) were evaluated in vitro after low caffeine concentration exposures, followed by a short treatment with 4mM of caffeine to abrogate the G2-checkpoint. The results show a statistically significant increase in chromatid breaks at caffeine concentrations ≥1mM. When caffeine was applied for G2/M-checkpoint abrogation, a statistically significant increase in chromatid breaks, compared to an active checkpoint, was only observed at 4mM of caffeine. The potential of low concentrations to induce asymmetric cell divisions was tested by applying a methodology combining the cytochalasin-B mediated cytokinesis-block micronucleus assay (CBMN) with interphase FISH (iFISH), using selected centromeric probes. Interestingly, low caffeine concentrations induce a dose dependent aneuploidy through asymmetric cell divisions, which are caused by misalignment of chromosomes through a mechanism

  18. DNA repair in PHA stimulated human lymphocytes

    International Nuclear Information System (INIS)

    Damage an repair of radiation induced DNA strand breaks were measured by alkaline lysis and hydroxyapatite chromatography. PHA stimulated human lymphocytes show that the rejoining process is complete within the first 50 min., afterwords secondary DNA damage and chromatid aberration. DNA repair, in synchronized culture, allows to evaluate individual repair capacity and this in turn can contribute to the discovery of individual who, although they do not demonstrate apparent clinical signs, are carriers of DNA repair deficiency. Being evident that a correlation exists between DNA repair capacity and carcinogenesis, the possibility of evaluating the existent relationship between DNA repair and survival in tumor cells comes therefore into discussion

  19. Gene-exposure interaction in occupational and environmental epidemiology: Results from an ongoing study

    OpenAIRE

    Kure, Elin H; Marit Thorsen; Inger-Lise Hansteen

    2009-01-01

     ABSTRACTA tissue bank is established in our department on a total of 659 persons whereof 341 are included in theNordic data base on somatic chromosome damage in humans. Genotyping of susceptibility genes relevantto the exposures of the cohort is an ongoing undertaking in our laboratory. GST's and mEH have beengenotyped for 80 persons so far, CYP's for 20 persons. When the mean number of chromatide breaks and ofcells with aberrations were related to genotypes no statistical difference could b...

  20. Mapping Topoisomerase IV Binding and Activity Sites on the E. coli Genome.

    Science.gov (United States)

    El Sayyed, Hafez; Le Chat, Ludovic; Lebailly, Elise; Vickridge, Elise; Pages, Carine; Cornet, Francois; Cosentino Lagomarsino, Marco; Espéli, Olivier

    2016-05-01

    Catenation links between sister chromatids are formed progressively during DNA replication and are involved in the establishment of sister chromatid cohesion. Topo IV is a bacterial type II topoisomerase involved in the removal of catenation links both behind replication forks and after replication during the final separation of sister chromosomes. We have investigated the global DNA-binding and catalytic activity of Topo IV in E. coli using genomic and molecular biology approaches. ChIP-seq revealed that Topo IV interaction with the E. coli chromosome is controlled by DNA replication. During replication, Topo IV has access to most of the genome but only selects a few hundred specific sites for its activity. Local chromatin and gene expression context influence site selection. Moreover strong DNA-binding and catalytic activities are found at the chromosome dimer resolution site, dif, located opposite the origin of replication. We reveal a physical and functional interaction between Topo IV and the XerCD recombinases acting at the dif site. This interaction is modulated by MatP, a protein involved in the organization of the Ter macrodomain. These results show that Topo IV, XerCD/dif and MatP are part of a network dedicated to the final step of chromosome management during the cell cycle. PMID:27171414

  1. Generation and Analysis of Transposon Ac/Ds-Induced Chromosomal Rearrangements in Rice Plants.

    Science.gov (United States)

    Xuan, Yuan Hu; Peterson, Thomas; Han, Chang-Deok

    2016-01-01

    Closely-located transposable elements (TEs) have been known to induce chromosomal breakage and rearrangements via alternative transposition. To study genome rearrangements in rice, an Ac/Ds system has been employed. This system comprises an immobile Ac element expressed under the control of CaMV 35S promoter, and a modified Ds element. A starter line carried Ac and a single copy of Ds at the OsRLG5 (Oryza sativa receptor-like gene 5). To enhance the transpositional activity, seed-derived calli were cultured and regenerated into plants. Among 270 lines regenerated from the starter, one line was selected that contained a pair of inversely-oriented Ds elements at the OsRLG5 (Oryza sativa receptor-like gene 5). The selected line was again subjected to tissue culture to obtain a regenerant population. Among 300 regenerated plants, 107 (36 %) contained chromosomal rearrangements including deletions, duplications, and inversions of various sizes. From 34 plants, transposition mechanisms leading to such genomic rearrangements were analyzed. The rearrangements were induced by sister chromatid transposition (SCT), homologous recombination (HR), and single chromatid transposition (SLCT). Among them, 22 events (65 %) were found to be transmitted to the next generation. These results demonstrate a great potential of tissue culture regeneration and the Ac/Ds system in understanding alternative transposition mechanisms and in developing chromosome engineering in plants.

  2. Chromosomal instability in the lymphocytes of breast cancer patients

    Directory of Open Access Journals (Sweden)

    Harsimran Kaur

    2009-01-01

    Full Text Available Genomic instability in the tumor tissue has been correlated with tumor progression. In the present study, chromosomal aberrations (CAs in peripheral blood lymphocytes (PBLs of breast tumor patients were studied to assess whether chromosomal instability (CIN in PBLs correlates with aggressiveness of breast tumor (i.e., disease stage and has any prognostic utility. Cultured blood lymphocyte metaphases were scored for aberrations in 31 breast cancer patients and 20 healthy age and sex-matched controls. A variety of CAs, including aneuploidy, polyploidy, terminal deletions, acentric fragments, double minutes, chromatid separations, ring chromosome, marker chromosome, chromatid gaps, and breaks were seen in PBLs of the patients. The CAs in patients were higher than in controls. A comparison of the frequency of metaphases with aberrations by grouping the patients according to the stage of advancement of disease did not reveal any consistent pattern of variation in lymphocytic CIN. Neither was any specific chromosomal abnormality found to be associated with the stage of cancer. This might be indicative of the fact that cancer patients have constitutional CIN, which predisposes them to the disease, and this inherent difference in the level of genomic instability might play a role in disease progression and response to treatment.

  3. The mitosis-regulating and protein-protein interaction activities of astrin are controlled by aurora-A-induced phosphorylation.

    Science.gov (United States)

    Chiu, Shao-Chih; Chen, Jo-Mei Maureen; Wei, Tong-You Wade; Cheng, Tai-Shan; Wang, Ya-Hui Candice; Ku, Chia-Feng; Lian, Chiao-Hsuan; Liu, Chun-Chih Jared; Kuo, Yi-Chun; Yu, Chang-Tze Ricky

    2014-09-01

    Cells display dramatic morphological changes in mitosis, where numerous factors form regulatory networks to orchestrate the complicated process, resulting in extreme fidelity of the segregation of duplicated chromosomes into two daughter cells. Astrin regulates several aspects of mitosis, such as maintaining the cohesion of sister chromatids by inactivating Separase and stabilizing spindle, aligning and segregating chromosomes, and silencing spindle assembly checkpoint by interacting with Src kinase-associated phosphoprotein (SKAP) and cytoplasmic linker-associated protein-1α (CLASP-1α). To understand how Astrin is regulated in mitosis, we report here that Astrin acts as a mitotic phosphoprotein, and Aurora-A phosphorylates Astrin at Ser(115). The phosphorylation-deficient mutant Astrin S115A abnormally activates spindle assembly checkpoint and delays mitosis progression, decreases spindle stability, and induces chromosome misalignment. Mechanistic analyses reveal that Astrin phosphorylation mimicking mutant S115D, instead of S115A, binds and induces ubiquitination and degradation of securin, which sequentially activates Separase, an enzyme required for the separation of sister chromatids. Moreover, S115A fails to bind mitosis regulators, including SKAP and CLASP-1α, which results in the mitotic defects observed in Astrin S115A-transfected cells. In conclusion, Aurora-A phosphorylates Astrin and guides the binding of Astrin to its cellular partners, which ensures proper progression of mitosis.

  4. Nanoceria have no genotoxic effect on human lens epithelial cells

    Science.gov (United States)

    Pierscionek, Barbara K.; Li, Yuebin; Yasseen, Akeel A.; Colhoun, Liza M.; Schachar, Ronald A.; Chen, Wei

    2010-01-01

    There are no treatments for reversing or halting cataract, a disease of the structural proteins in the eye lens, that has associations with other age-related degenerative conditions such as Alzheimer's disease. The incidence of cataract and associated conditions is increasing as the average age of the population rises. Protein folding diseases are difficult to assess in vivo as proteins and their age-related changes are assessed after extraction. Nanotechnology can be used to investigate protein changes in the intact lens as well as for a potential means of drug delivery. Nanoparticles, such as cerium oxide (CeO2) which have antioxidant properties, may even be used as a means of treating cataract directly. Prior to use in treatments, nanoparticle genotoxicity must be tested to assess the extent of any DNA or chromosomal damage. Sister chromatid exchanges were measured and DNA damage investigated using the alkaline COMET assay on cultured human lens epithelial cells, exposed to 5 and 10 µg ml-1 of CeO2 nanoparticles (nanoceria). Nanoceria at these dosages did not cause any DNA damage or significant increases in the number of sister chromatid exchanges. The absence of genotoxic effects on lens cells suggests that nanoceria, in the doses and exposures tested in this study, are not deleterious to the eye lens and have the potential for use in studying structural alterations, in developing non-surgical cataract treatments and in investigating other protein folding diseases.

  5. Genetical and cytological response of three tomato varieties to gamma rays

    International Nuclear Information System (INIS)

    Seeds of the tomato varieties, i.e, No. 10, bison and kecskement were irradiated with 12 krad. The abnormalities in the meiotic stages of pollen mother cells in both M1 and M2 were evaluated. The 3 varieties were greatly varied in the percentage of abnormalities occurred. The variety No. 10 showed the maximum percentage of lagging chromosomes. Meanwhile, the variety was super accounted in stickiness or clumping chromosomes, chromatid bridges and micronuclei. Whereas, the highest percentage of disturbed chromosomes and sterility was concerning to the variety kecskement. Different types of abnormalities such as stickiness, disturbed chromosomes, chromatid bridges, micronuclei and pollen sterility highly occurred in M2 than M1. Meanwhile, the percentage of lagging chromosomes reached the maximum in M1 rather than in M2. It could be mentioned that pollen sterility was increased by radiation treatment in tomato varieties. This sterility reached the maximum in M2. This was attributed to the increase in the chromosomal abnormalities in M2. A number of mutants, i.e., dwarf, non-branching, sterile plants and variations in fruit weight, had been occurred in the M2 as a function of gamma irradiation. 13 figs., 1 tab

  6. Development and application of a constant temperature water-bath ultraviolet radiation instrument%恒温水浴紫外光照射仪研制与应用

    Institute of Scientific and Technical Information of China (English)

    戚康标; 王金发; 王宏斌; 何炎明; 冯冬茹; 刘兵

    2012-01-01

    A highly efficient constant temperature water-bath ultraviolet radiation instrument is developed for distinguishing color aberration and exchange of sister chromatids according to the nature of the material handling and special requirements with the staining of sister chromatids. By a wide range of continuous use and examining, it is proved that the constant temperature water-bath ultraviolet radiation instrument has the advantages of convenient operation, safe use and stable performance. The samples treated with the instrument are processed uniformly and have obvious color aberration and fine resolution.%根据姊妹染色单体色差染色材料处理的性质和特殊要求,研制一种能够高效分辨姊妹染色单体色差和互换的仪器——恒温水浴紫外光照射仪.经过大范围连续使用与测试结果表明,该仪器操作简便,安全稳定,样品玻片处理均匀,姊妹染色单体染色清晰,色差明显,分辨率高.

  7. Cytogenetic study of Ascaris trypsin inhibitor in cultured human lymphocytes with metabolic activation

    Indian Academy of Sciences (India)

    Joanna Blaszkowska; Wanda Bratkowska; Dobroslawa Lopaczynska; Tomasz Ferenc

    2009-04-01

    The trypsin inhibitor (ATI) isolated from gastrointestinal nematode Ascaris suum was tested in vitro for induction of chromosome aberrations and sister chromatid exchanges (SCE). Genotoxicity assessment of purified ATI was carried out on metaphase plates received from peripheral blood lymphocyte macroculture (48 h test of structural chromosome aberrations and 72 h test of SCE) with exogenous metabolic activation. ATI was tested in dose of 25, 50 and 100 μg per ml of culture. Kinetics of cell divisions were determined by the replication index (RI). The mitotic index (MI) was expressed as a number of metaphases per 1000 nuclei analysed. Analysis of chromosome aberrations showed that higher doses of ATI (50 and 100 /ml) significantly increased the frequency of chromosome aberrations (mainly of chromatid gaps and breaks) compared to the negative control. All concentrations of ATI caused a statistically significant reduction in the MI and RI. In comparison with the negative control, a significant increase in the SCE frequency was observed in all applied doses of ATI. Thus, in the presence of S9 activation, the Ascaris trypsin inhibitor showed potential clastogenic activity and inhibition of the dynamics of lymphocyte divisions.

  8. Evaluation of genotoxic activity of tenofovir disoproxil fumarate in human peripheral lymphocytes

    Directory of Open Access Journals (Sweden)

    Kubra Kurt

    2016-06-01

    Full Text Available Purpose: Antiretroviral drugs used in the treatment of HIV (Human Immunodeficiency Virus iinfection, treat by preventing the proliferation of HIV in human body. People with HIV have to use this drugs for lifelong because of inability of the drugs to eradicate the viruses. In this study, we investigated the in vitro genotoxic activity of tenofovir disoproxil fumarate one of the antiretroviral drugs, in human peripheral lymphocytes. Material and Methods: The cells were treated with four different concentrations of tenofovir disoproxil fumarate for 24 and 48 hours. The levels of sister chromatid exchanges, chromosomal aberrations, and micronucleus in the cells were examined for the genotoxic activity of tenofovir disoproxil fumarate. Mitotic index, proliferation index, and nucleer division index of treated cells were also determined for the cytotoxic effect of tenofovir disoproxil fumarate. Results: There was no significant differences in the level of sister chromatid exchanges, chromosomal aberrations, and micronucleus in human lyphocytes treated with all concetrations of tenofovir disoproxil fumarate for all treatment period as compared to control group. Similarly, it was observed that treatment of tenofovir disoproxil fumarate did not affect the mitotic index, proliferation index, and nucleer division index values. Conclusion: As a result, in this study, it is demonstrated that tenofovir disoproxil fumarate did not have genotoxic or cytotoxic effect in the human peripheral lymphocytes. [Cukurova Med J 2016; 41(2.000: 229-235

  9. The temporal and spatial pattern of histone H3 phosphorylation at serine 28 and serine 10 is similar in plants but differs between mono- and polycentric chromosomes.

    Science.gov (United States)

    Gernand, D; Demidov, D; Houben, A

    2003-01-01

    Immunolabeling using site-specific antibodies against phosphorylated histone H3 at serine 10 or serine 28 revealed in plants an almost similar temporal and spatial pattern of both post-translational modification sites at mitosis and meiosis. During the first meiotic division the entire chromosomes are highly H3 phosphorylated. In the second meiotic division, like in mitosis, the chromosomes contain high phosphorylation levels in the pericentromeric region and very little H3 phosphorylation along the arms of monocentric species. In the polycentric plant Luzula luzuloides phosphorylation at both serine positions occurs along the whole chromosomes, whereas in monocentric species, only the pericentromeric regions showed strong signals from mitotic prophase to telophase. No phosphorylated serine 10 or serine 28 was detectable on single chromatids at anaphase II resulting from equational segregation of rye B chromosome univalents during the preceding anaphase I. In addition, we found a high level of serine 28 as well as of serine 10 phosphorylation along the entire mitotic monocentric chromosomes after treatment of mitotic cells using the phosphatase inhibitor cantharidin. These observations suggest that histone H3 phosphorylation at serine 10 and 28 is an evolutionarily conserved event and both sites are likely to be involved in the same process, such as sister chromatid cohesion. PMID:14610360

  10. Studies on mutagenic activity of 60Co γ-ray irradiated rape pollen

    International Nuclear Information System (INIS)

    In the present study on disinfection, the rape pollen was irradiated with 2.5 kGy 60Co γ-ray. Micronuclei, sister chromatid exchanges (SCE) of bone marrow cells and chromosomal aberrations of meiotic cells in mice were used as an indicater of chromosomal damage to study the mutagenicity of irradiated rape pollen. The results are as follows: (1) The frequency of micronuclei in polychromatic erythrocytes is 2.00 per mille; nucleated cells is 0.8 per mille in control group. In the numbers of polychromatic erythrocytes and nucleated cells with micronuclei, there is no obviously difference in irradiated and unirradiated groups. (2) SCE incidence of control group is 2.01 ± 0.12/cell. No significant difference in the frequency of SCE exists between non-irradiated rape pollen and the control groups. But the frequency of SCE in irradiated rape pollen group (3000 mg/kg/day x 7) is 2.36 ± 0.12/cell; high dose group (6000 mg/kg/day x 7) is 2.96 ± 0.14/cell. In comparison with control group, there is a significant difference. (3) The chromatid breaks, fragments, and univalents in primary spermatocytes have been obseved. The frequencies of chromosomal aberration showed no obviously difference among irradiated and non-irradiated rape pollen groups

  11. Chromosomal instability associated with a novel BLM frameshift mutation (c.1980-1982delAA) in two unrelated Tunisian families with Bloom syndrome.

    Science.gov (United States)

    Ben Salah, G; Salem, I Hadj; Masmoudi, A; Ben Rhouma, B; Turki, H; Fakhfakh, F; Ayadi, H; Kamoun, H

    2014-10-01

    The Bloom syndrome (BS) is an autosomal recessive disorder associated with dwarfism, immunodeficiency, reduced fertility and cancer risk. BS cells show genomic instability, particularly an hyper exchange between the sister chromatids due to a defective processing of the DNA replication intermediates. It is caused by mutations in the BLM gene which encodes a member of the RecQ family of DExH box DNA helicases. In this study, we reported cytogenetic, BLM linkage and mutational analyses for two affected Tunisian families. The Cytogenetic parameters were performed by chromosomal aberration (CA) and sister chromatid exchange (SCE) assays and results showed a significant increase in mean frequency of CA and SCE in BS cells. BLM linkage performed by microsatellite genotyping revealed homozygous haplotypes for the BS patients, evidence of linkage to BLM gene. Mutational analysis by direct DNA sequencing revealed a novel frameshift mutation (c.1980-1982delAA) in exon 8 of BLM gene, resulting in a truncated protein (p.Lys662fsX5). The truncated protein could explain genomic instability and its related symptoms in the BS patients. The screening of this mutation is useful for BS diagnosis confirmation in Tunisian families.

  12. Stressing Mitosis to Death

    Directory of Open Access Journals (Sweden)

    Andrew eBurgess

    2014-06-01

    Full Text Available The final stage of cell division (mitosis, involves the compaction of the duplicated genome into chromatid pairs. Each pair is captured by microtubules emanating from opposite spindle poles, aligned at the metaphase plate, and then faithfully segregated to form two identical daughter cells. Chromatids that are not correctly attached to the spindle are detected by the constitutively active spindle assembly checkpoint (SAC. Any stress that prevents correct bipolar spindle attachment, blocks the satisfaction of the SAC, and induces a prolonged mitotic arrest, providing the cell time to obtain attachment and complete segregation correctly. Unfortunately, during mitosis repairing damage is not generally possible due to the compaction of DNA into chromosomes, and subsequent suppression of gene transcription and translation. Therefore, in the presence of significant damage cell death is instigated to ensure that genomic stability is maintained. While most stresses lead to an arrest in mitosis, some promote premature mitotic exit, allowing cells to by-pass mitotic cell death. This mini-review will focus on the effects and outcomes that common stresses have on mitosis, and how this impacts on the efficacy of mitotic chemotherapies.

  13. Stressing mitosis to death.

    Science.gov (United States)

    Burgess, Andrew; Rasouli, Mina; Rogers, Samuel

    2014-01-01

    The final stage of cell division (mitosis), involves the compaction of the duplicated genome into chromatid pairs. Each pair is captured by microtubules emanating from opposite spindle poles, aligned at the metaphase plate, and then faithfully segregated to form two identical daughter cells. Chromatids that are not correctly attached to the spindle are detected by the constitutively active spindle assembly checkpoint (SAC). Any stress that prevents correct bipolar spindle attachment, blocks the satisfaction of the SAC, and induces a prolonged mitotic arrest, providing the cell time to obtain attachment and complete segregation correctly. Unfortunately, during mitosis repairing damage is not generally possible due to the compaction of DNA into chromosomes, and subsequent suppression of gene transcription and translation. Therefore, in the presence of significant damage cell death is instigated to ensure that genomic stability is maintained. While most stresses lead to an arrest in mitosis, some promote premature mitotic exit, allowing cells to bypass mitotic cell death. This mini-review will focus on the effects and outcomes that common stresses have on mitosis, and how this impacts on the efficacy of mitotic chemotherapies. PMID:24926440

  14. Distribution pattern of histone H3 phosphorylation at serine 10 during mitosis and meiosis in Brachiaria species

    Indian Academy of Sciences (India)

    C. M. P. Paula; V. H. Techio; F. Souza Sobrinho; A. S. Freitas

    2013-08-01

    Histones are the major eukaryotic DNA-binding proteins. Posttranslational modifications on N-terminal tails of histones that form nucleosomes are often associated with distinct biological functions. Some theories suggest that one of these modifications, the phosphorylation of histone H3 at serine 10 (H3S10ph) plays a role in both chromosome condensation and sister chromatid cohesion. Although histones and some of their modifications are highly conserved, studies have shown that role and distribution of H3S10ph may differ between species. We evaluated the pattern of H3 phosphorylation using immunodetection during mitosis and meiosis in both diploid and tetraploid genotypes of Brachiaria species. Results revealed differences in chromosome distribution of H3S10ph when mitosis and meiosis were compared. Whole chromosomes were phosphorylated during meiosis I, whereas phosphorylation was restricted to the pericentromeric region in both meiosis II and mitosis. There was no variation in phosphorylation patterns between Brachiaria species and diploid and tetraploid genotypes. Regarding spatiotemporal coordination in the Brachiaria species evaluated, H3S10ph is related to maintenance of sister chromatid cohesion during cell divisions.

  15. Nanoceria have no genotoxic effect on human lens epithelial cells

    International Nuclear Information System (INIS)

    There are no treatments for reversing or halting cataract, a disease of the structural proteins in the eye lens, that has associations with other age-related degenerative conditions such as Alzheimer's disease. The incidence of cataract and associated conditions is increasing as the average age of the population rises. Protein folding diseases are difficult to assess in vivo as proteins and their age-related changes are assessed after extraction. Nanotechnology can be used to investigate protein changes in the intact lens as well as for a potential means of drug delivery. Nanoparticles, such as cerium oxide (CeO2) which have antioxidant properties, may even be used as a means of treating cataract directly. Prior to use in treatments, nanoparticle genotoxicity must be tested to assess the extent of any DNA or chromosomal damage. Sister chromatid exchanges were measured and DNA damage investigated using the alkaline COMET assay on cultured human lens epithelial cells, exposed to 5 and 10 μg ml-1 of CeO2 nanoparticles (nanoceria). Nanoceria at these dosages did not cause any DNA damage or significant increases in the number of sister chromatid exchanges. The absence of genotoxic effects on lens cells suggests that nanoceria, in the doses and exposures tested in this study, are not deleterious to the eye lens and have the potential for use in studying structural alterations, in developing non-surgical cataract treatments and in investigating other protein folding diseases.

  16. The DASH complex and Klp5/Klp6 kinesin coordinate bipolar chromosome attachment in fission yeast.

    Science.gov (United States)

    Sanchez-Perez, Isabel; Renwick, Steven J; Crawley, Karen; Karig, Inga; Buck, Vicky; Meadows, John C; Franco-Sanchez, Alejandro; Fleig, Ursula; Toda, Takashi; Millar, Jonathan B A

    2005-08-17

    We identified a truncated allele of dam1 as a multicopy suppressor of the sensitivity of cdc13-117 (cyclin B) and mal3-1 (EB-1) cells to thiabendazole, a microtubule poison. We find that Dam1 binds to the plus end of spindle microtubules and kinetochores as cells enter mitosis and this is dependent on other components of the fission yeast DASH complex, including Ask1, Duo1, Spc34 and Dad1. By contrast, Dad1 remains bound to kinetochores throughout the cell cycle and its association is dependent on the Mis6 and Mal2, but not Mis12, Nuf2 or Cnp1, kinetochore proteins. In cells lacking Dam1, or other components of the DASH complex, anaphase is delayed due to activation of the spindle assembly checkpoint and lagging sister chromatids are frequently observed and occasionally sister chromatid pairs segregate to the same spindle pole. We find that the mitotic centromere-associated Klp5/Klp6 kinesin complex is essential in cells lacking components of the DASH complex. Cells lacking both Dam1 and Klp5 undergo a first cell cycle arrest in mitosis due to a failure to establish bipolar chromosome attachment. PMID:16079915

  17. Dominant-lethal mutations and heritable translocations in mice

    Energy Technology Data Exchange (ETDEWEB)

    Generoso, W.M.

    1983-01-01

    Chromosome aberrations are a major component of radiation or chemically induced genetic damage in mammalian germ cells. The types of aberration produced are dependent upon the mutagen used and the germ-cell stage treated. For example, in male meiotic and postmeiotic germ cells certain alkylating chemicals induce both dominant-lethal mutations and heritable translocations while others induce primarily dominant-lethal mutations. Production of these two endpoints appears to be determined by the stability of alkylation products with the chromosomes. If the reaction products are intact in the male chromosomes at the time of sperm entry, they may be repaired in fertilized eggs. If repair is not effected and the alkylation products persist to the time of pronuclear chromosome replication, they lead to chromatid-type aberrations and eventually to dominant-lethality. The production of heritable translocations, on the other hand, requires a transformation of unstable alkylation products into suitable intermediate lesions. The process by which these lesions are converted into chromosome exchange within the male genome takes place after sperm enters the egg but prior to the time of pronuclear chromosome replication (i.e., chromosome-type). Thus, dominant-lethal mutations result from both chromatid- and chromosome-type aberrations while heritable translocations result primarily from the latter type. DNA target sites associated with the production of these two endpoints are discussed.

  18. Chromosomal Integrity after UV Irradiation Requires FANCD2-Mediated Repair of Double Strand Breaks

    Science.gov (United States)

    Federico, María Belén; Vallerga, María Belén; Radl, Analía; Paviolo, Natalia Soledad; Bocco, José Luis; Di Giorgio, Marina; Soria, Gastón; Gottifredi, Vanesa

    2016-01-01

    Fanconi Anemia (FA) is a rare autosomal recessive disorder characterized by hypersensitivity to inter-strand crosslinks (ICLs). FANCD2, a central factor of the FA pathway, is essential for the repair of double strand breaks (DSBs) generated during fork collapse at ICLs. While lesions different from ICLs can also trigger fork collapse, the contribution of FANCD2 to the resolution of replication-coupled DSBs generated independently from ICLs is unknown. Intriguingly, FANCD2 is readily activated after UV irradiation, a DNA-damaging agent that generates predominantly intra-strand crosslinks but not ICLs. Hence, UV irradiation is an ideal tool to explore the contribution of FANCD2 to the DNA damage response triggered by DNA lesions other than ICL repair. Here we show that, in contrast to ICL-causing agents, UV radiation compromises cell survival independently from FANCD2. In agreement, FANCD2 depletion does not increase the amount of DSBs generated during the replication of UV-damaged DNA and is dispensable for UV-induced checkpoint activation. Remarkably however, FANCD2 protects UV-dependent, replication-coupled DSBs from aberrant processing by non-homologous end joining, preventing the accumulation of micronuclei and chromatid aberrations including non-homologous chromatid exchanges. Hence, while dispensable for cell survival, FANCD2 selectively safeguards chromosomal stability after UV-triggered replication stress. PMID:26765540

  19. Recombinational repair of radiation-induced double-strand breaks occurs in the absence of extensive resection

    Science.gov (United States)

    Westmoreland, James W.; Resnick, Michael A.

    2016-01-01

    Recombinational repair provides accurate chromosomal restitution after double-strand break (DSB) induction. While all DSB recombination repair models include 5′-3′ resection, there are no studies that directly assess the resection needed for repair between sister chromatids in G-2 arrested cells of random, radiation-induced ‘dirty’ DSBs. Using our Pulse Field Gel Electrophoresis-shift approach, we determined resection at IR-DSBs in WT and mutants lacking exonuclease1 or Sgs1 helicase. Lack of either reduced resection length by half, without decreased DSB repair or survival. In the exo1Δ sgs1Δ double mutant, resection was barely detectable, yet it only took an additional hour to achieve a level of repair comparable to WT and there was only a 2-fold dose-modifying effect on survival. Results with a Dnl4 deletion strain showed that remaining repair was not due to endjoining. Thus, similar to what has been shown for a single, clean HO-induced DSB, a severe reduction in resection tract length has only a modest effect on repair of multiple, dirty DSBs in G2-arrested cells. Significantly, this study provides the first opportunity to directly relate resection length at DSBs to the capability for global recombination repair between sister chromatids. PMID:26503252

  20. Chromosome studies in human subjects chronically exposed to arsenic in drinking water

    Energy Technology Data Exchange (ETDEWEB)

    Vig, B.K.; Figueroa, M.L.; Cornforth, M.N.; Jenkins, S.H.

    1984-01-01

    A two-year study was carried out on human subjects of various ages and backgrounds who had been drinking water containing more than 0.05 mg/liter (0.05 ppm) arsenic for a period of at least five years. The main aim was to correlate the frequency of chromosome aberrations and sister chromatid exchanges in the lymphocytes with the amount of arsenic in the water. In addition, the incidence of skin cancer, fetal wastage, and genetic or developmental abnormalities were explored. Several other variables--eg, coffee, wine, and cigarette consumption; sex; residence (rural vs urban); and exposure to chemicals, smelters, or pesticides--were also taken into consideration. The data on chromosome aberrations (104 exposed and 86 control individuals) and on sister chromatid exchanges (98 exposed and 83 control individuals) did not show that arsenic at concentrations (greater than 0.05 mg/liter) has any effect on these parameters. Similarly, no other health effects of arsenic at these concentrations were found.

  1. Generation and Analysis of Transposon Ac/Ds-Induced Chromosomal Rearrangements in Rice Plants.

    Science.gov (United States)

    Xuan, Yuan Hu; Peterson, Thomas; Han, Chang-Deok

    2016-01-01

    Closely-located transposable elements (TEs) have been known to induce chromosomal breakage and rearrangements via alternative transposition. To study genome rearrangements in rice, an Ac/Ds system has been employed. This system comprises an immobile Ac element expressed under the control of CaMV 35S promoter, and a modified Ds element. A starter line carried Ac and a single copy of Ds at the OsRLG5 (Oryza sativa receptor-like gene 5). To enhance the transpositional activity, seed-derived calli were cultured and regenerated into plants. Among 270 lines regenerated from the starter, one line was selected that contained a pair of inversely-oriented Ds elements at the OsRLG5 (Oryza sativa receptor-like gene 5). The selected line was again subjected to tissue culture to obtain a regenerant population. Among 300 regenerated plants, 107 (36 %) contained chromosomal rearrangements including deletions, duplications, and inversions of various sizes. From 34 plants, transposition mechanisms leading to such genomic rearrangements were analyzed. The rearrangements were induced by sister chromatid transposition (SCT), homologous recombination (HR), and single chromatid transposition (SLCT). Among them, 22 events (65 %) were found to be transmitted to the next generation. These results demonstrate a great potential of tissue culture regeneration and the Ac/Ds system in understanding alternative transposition mechanisms and in developing chromosome engineering in plants. PMID:27557685

  2. Dominant-lethal mutations and heritable translocations in mice

    International Nuclear Information System (INIS)

    Chromosome aberrations are a major component of radiation or chemically induced genetic damage in mammalian germ cells. The types of aberration produced are dependent upon the mutagen used and the germ-cell stage treated. For example, in male meiotic and postmeiotic germ cells certain alkylating chemicals induce both dominant-lethal mutations and heritable translocations while others induce primarily dominant-lethal mutations. Production of these two endpoints appears to be determined by the stability of alkylation products with the chromosomes. If the reaction products are intact in the male chromosomes at the time of sperm entry, they may be repaired in fertilized eggs. If repair is not effected and the alkylation products persist to the time of pronuclear chromosome replication, they lead to chromatid-type aberrations and eventually to dominant-lethality. The production of heritable translocations, on the other hand, requires a transformation of unstable alkylation products into suitable intermediate lesions. The process by which these lesions are converted into chromosome exchange within the male genome takes place after sperm enters the egg but prior to the time of pronuclear chromosome replication (i.e., chromosome-type). Thus, dominant-lethal mutations result from both chromatid- and chromosome-type aberrations while heritable translocations result primarily from the latter type. DNA target sites associated with the production of these two endpoints are discussed

  3. Genotoxic effects of copper sulfate in rabbits

    Directory of Open Access Journals (Sweden)

    Georgieva S.

    2013-01-01

    Full Text Available This study was carried out to determine the genotoxic effects of oral application of CuSO4 in rabbits by the chromosome aberration (CA and sister chromatid exchange (SCE tests. Ten male New Zealand rabbits (5 months old, weighing 3.5-4.0 kg were allocated into two groups. The first group received CuSO4 (5H2O in drinking water for 6 consecutive days. The second group was used as a control. On the 7th day, blood samples were taken from the ear marginal vein and the SCE and CA tests in peripheral lymphocytes were used as genotoxicity and mutagenicity endpoints, respectively. Results showed a significant increase in the frequencies of the aberrant cells (7.4±0.24, P<0.001 and CA (chromatid fragments 3.2±0.37, chromosome fragments 4.2±0.37, P<0.001, and total aberrations (7.4±0.24, P<0.001 after the treatment with CuSO4 when compared with the control group. The level of SCE per cell in the CuSO4-treated rabbits (9.66±0.062 was significantly higher than in rabbits from the control group. These findings show that copper exhibits a genotoxic and mutagenic potential in rabbits.

  4. Spindle checkpoint-independent inhibition of mitotic chromosome segregation by Drosophila Mps1.

    Science.gov (United States)

    Althoff, Friederike; Karess, Roger E; Lehner, Christian F

    2012-06-01

    Monopolar spindle 1 (Mps1) is essential for the spindle assembly checkpoint (SAC), which prevents anaphase onset in the presence of misaligned chromosomes. Moreover, Mps1 kinase contributes in a SAC-independent manner to the correction of erroneous initial attachments of chromosomes to the spindle. Our characterization of the Drosophila homologue reveals yet another SAC-independent role. As in yeast, modest overexpression of Drosophila Mps1 is sufficient to delay progression through mitosis during metaphase, even though chromosome congression and metaphase alignment do not appear to be affected. This delay in metaphase depends on the SAC component Mad2. Although Mps1 overexpression in mad2 mutants no longer causes a metaphase delay, it perturbs anaphase. Sister kinetochores barely move apart toward spindle poles. However, kinetochore movements can be restored experimentally by separase-independent resolution of sister chromatid cohesion. We propose therefore that Mps1 inhibits sister chromatid separation in a SAC-independent manner. Moreover, we report unexpected results concerning the requirement of Mps1 dimerization and kinase activity for its kinetochore localization in Drosophila. These findings further expand Mps1's significance for faithful mitotic chromosome segregation and emphasize the importance of its careful regulation.

  5. [Benefit of human gamete cytogenetics: results and perspectives].

    Science.gov (United States)

    Vialard, F; Pellestor, F

    2008-09-01

    In man, the incidence of reproductive failures is high and chromosomal abnormalities remains the major cause of pregnancy wastage. The advent of molecular cytogenetic techniques and assisted reproduction technology have brought forth new approaches for the chromosomal analysis of human oocytes and spermatozoa. The oocyte analyses have evidenced the high rate of chromosomal abnormalities in women and identified premature separation of sister chromatid as a major mechanism in aneuploidy occurrence. High frequencies of aneuploidy have been found in various groups of women, such as patients over 35 or 38 years old, patients with recurrent implantation failures or recurrent miscarriages. The polar body analysis has confirmed the major contribution of premature separation of sister chromatids in aneuploidies and the effect of maternal ageing on its occurrence. In spermatozoa, the efficient adaptation of in situ chromosomal detection techniques has facilitated the segregation analysis of chromosomal abnormalities. Despite the consensus observed in sperm studies of robertsonnian translocations and inversions, new data are required for accurate estimates of imbalances in various types of structural rearrangements. For infertile patients with normal karyotypes, there is significant increase in aneuploidy frequencies, which can be extremely elevated in some groups of subjects, such as patients with large headed spermatozoa syndrome.

  6. Diverse developmental disorders from The One Ring: distinct molecular pathways underlie the cohesinopathies

    Directory of Open Access Journals (Sweden)

    Julia eHorsfield

    2012-09-01

    Full Text Available The multi-subunit protein complex, cohesin, is responsible for sister chromatid cohesion during cell division. The interaction of cohesin with DNA is controlled by a number of additional regulatory proteins. Mutations in cohesin, or its regulators, cause a spectrum of human developmental syndromes known as the ‘cohesinopathies’. Cohesinopathy disorders include Cornelia de Lange Syndrome and Roberts Syndrome. The discovery of novel roles for chromatid cohesion proteins in regulating gene expression led to the idea that cohesinopathies are caused by dysregulation of multiple genes downstream of mutations in cohesion proteins. Consistent with this idea, Drosophila, mouse and zebrafish cohesinopathy models all show altered expression of developmental genes. However, there appears to be incomplete overlap among dysregulated genes downstream of mutations in different components of the cohesion apparatus. This is surprising because mutations in all cohesion proteins would be predicted to affect cohesin’s roles in cell division and gene expression in similar ways. Here we review the differences and similarities between genetic pathways downstream of components of the cohesion apparatus, and discuss how such differences might arise, and contribute to the spectrum of cohesinopathy disorders. We propose that mutations in different elements of the cohesion apparatus have distinct developmental outcomes that can be explained by sometimes subtly different molecular effects.

  7. Genome-wide high-resolution mapping of UV-induced mitotic recombination events in Saccharomyces cerevisiae.

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    Yi Yin

    2013-10-01

    Full Text Available In the yeast Saccharomyces cerevisiae and most other eukaryotes, mitotic recombination is important for the repair of double-stranded DNA breaks (DSBs. Mitotic recombination between homologous chromosomes can result in loss of heterozygosity (LOH. In this study, LOH events induced by ultraviolet (UV light are mapped throughout the genome to a resolution of about 1 kb using single-nucleotide polymorphism (SNP microarrays. UV doses that have little effect on the viability of diploid cells stimulate crossovers more than 1000-fold in wild-type cells. In addition, UV stimulates recombination in G1-synchronized cells about 10-fold more efficiently than in G2-synchronized cells. Importantly, at high doses of UV, most conversion events reflect the repair of two sister chromatids that are broken at approximately the same position whereas at low doses, most conversion events reflect the repair of a single broken chromatid. Genome-wide mapping of about 380 unselected crossovers, break-induced replication (BIR events, and gene conversions shows that UV-induced recombination events occur throughout the genome without pronounced hotspots, although the ribosomal RNA gene cluster has a significantly lower frequency of crossovers.

  8. The Saccharomyces cerevisiae RAD9, RAD17, RAD24 and MEC3 genes are required for tolerating irreparable, ultraviolet-induced DNA damage

    International Nuclear Information System (INIS)

    In wild-type Saccharomyces cerevisiae, a checkpoint slows the rate of progression of an ongoing S phase in response to exposure to a DNA-alkylating agent. Mutations that eliminate S phase regulation also confer sensitivity to alkylating agents, leading us to suggest that, by regulating the S phase rate, cells are either better able to repair or better able to replicate damaged DNA. In this study, we determine the effects of mutations that impair S phase regulation on the ability of excision repair-defective cells to replicate irreparably UV-damaged DNA. We assay survival after UV irradiation, as well as the genetic consequences of replicating a damaged template, namely mutation and sister chromatid exchange induction. We find that RAD9, RAD17, RAD24, and MEC3 are required for UV-induced (although not spontaneous) mutagenesis, and that RAD9 and RAD17 (but not REV3, RAD24, and MEC3) are required for maximal induction of replication-dependent sister chromatid exchange. Therefore, checkpoint genes not only control cell cycle progression in response to damage, but also play a role in accommodating DNA damage during replication. (author)

  9. Drosophila Ctf4 is essential for efficient DNA replication and normal cell cycle progression

    Directory of Open Access Journals (Sweden)

    Christensen Tim W

    2011-04-01

    Full Text Available Abstract Background Proper coordination of the functions at the DNA replication fork is vital to the normal functioning of a cell. Specifically the precise coordination of helicase and polymerase activity is crucial for efficient passage though S phase. The Ctf4 protein has been shown to be a central member of the replication fork and links the replicative MCM helicase and DNA polymerase α primase. In addition, it has been implicated as a member of a complex that promotes replication fork stability, the Fork Protection Complex (FPC, and as being important for sister chromatid cohesion. As such, understanding the role of Ctf4 within the context of a multicellular organism will be integral to our understanding of its potential role in developmental and disease processes. Results We find that Drosophila Ctf4 is a conserved protein that interacts with members of the GINS complex, Mcm2, and Polymerase α primase. Using in vivo RNAi knockdown of CTF4 in Drosophila we show that Ctf4 is required for viability, S phase progression, sister chromatid cohesion, endoreplication, and coping with replication stress. Conclusions Ctf4 remains a central player in DNA replication. Our findings are consistent with what has been previously reported for CTF4 function in yeast, Xenopus extracts, and human tissue culture. We show that Ctf4 function is conserved and that Drosophila can be effectively used as a model to further probe the precise function of Ctf4 as a member of the replication fork and possible roles in development.

  10. Reconstruction of the kinetochore: a prelude to meiosis

    Directory of Open Access Journals (Sweden)

    Haraguchi Tokuko

    2007-06-01

    Full Text Available Abstract In eukaryotic organisms, chromosomes are spatially organized within the nucleus. Such nuclear architecture provides a physical framework for the genetic activities of chromosomes, and changes its functional organization as the cell moves through the phases of the cell cycle. The fission yeast Schizosaccharomyces pombe provides a striking example of nuclear reorganization during the transition from mitosis to meiosis. In this organism, centromeres remain clustered at the spindle-pole body (SPB; a centrosome-equivalent structure in fungi during mitotic interphase. In contrast, during meiotic prophase, centromeres dissociate from the SPB and telomeres cluster to the SPB. Recent studies revealed that this repositioning of chromosomes is regulated by mating pheromone signaling. Some centromere proteins disappear from the centromere in response to mating pheromone, leading to dissociation of centromeres from the SPB. Interestingly, mating pheromone signaling is also required for monopolar orientation of the kinetochore which is crucial for proper segregation of sister chromatids during meiosis. When meiosis is induced in the absence of mating pheromone signaling, aberrant chromosome behaviors are observed: the centromere proteins remain at the centromere; the centromere remains associated with the SPB; and sister chromatids segregate precociously in the first meiotic division. These aberrant chromosome behaviors are all normalized by activating the mating pheromone signaling pathway. Thus, action of mating pheromone on the centromere is important for coherent behavior of chromosomes in meiosis. Here we discuss repositioning and reconstruction of the centromere during the transition from mitosis to meiosis, and highlight its significance for proper progression of meiosis.

  11. Arabidopsis thaliana WAPL is essential for the prophase removal of cohesin during meiosis.

    Directory of Open Access Journals (Sweden)

    Kuntal De

    2014-07-01

    Full Text Available Sister chromatid cohesion, which is mediated by the cohesin complex, is essential for the proper segregation of chromosomes in mitosis and meiosis. The establishment of stable sister chromatid cohesion occurs during DNA replication and involves acetylation of the complex by the acetyltransferase CTF7. In higher eukaryotes, the majority of cohesin complexes are removed from chromosomes during prophase. Studies in fly and human have shown that this process involves the WAPL mediated opening of the cohesin ring at the junction between the SMC3 ATPase domain and the N-terminal domain of cohesin's α-kleisin subunit. We report here the isolation and detailed characterization of WAPL in Arabidopsis thaliana. We show that Arabidopsis contains two WAPL genes, which share overlapping functions. Plants in which both WAPL genes contain T-DNA insertions show relatively normal growth and development but exhibit a significant reduction in male and female fertility. The removal of cohesin from chromosomes during meiotic prophase is blocked in Atwapl mutants resulting in chromosome bridges, broken chromosomes and uneven chromosome segregation. In contrast, while subtle mitotic alterations are observed in some somatic cells, cohesin complexes appear to be removed normally. Finally, we show that mutations in AtWAPL suppress the lethality associated with inactivation of AtCTF7. Taken together our results demonstrate that WAPL plays a critical role in meiosis and raises the possibility that mechanisms involved in the prophase removal of cohesin may vary between mitosis and meiosis in plants.

  12. Haploid meiosis in Arabidopsis: double-strand breaks are formed and repaired but without synapsis and crossovers.

    Directory of Open Access Journals (Sweden)

    Marta Cifuentes

    Full Text Available Two hallmark features of meiosis are i the formation of crossovers (COs between homologs and ii the production of genetically-unique haploid spores that will fuse to restore the somatic ploidy level upon fertilization. In this study we analysed meiosis in haploid Arabidopsis thaliana plants and a range of haploid mutants to understand how meiosis progresses without a homolog. Extremely low chiasma frequency and very limited synapsis occurred in wild-type haploids. The resulting univalents segregated in two uneven groups at the first division, and sister chromatids segregated to opposite poles at the second division, leading to the production of unbalanced spores. DNA double-strand breaks that initiate meiotic recombination were formed, but in half the number compared to diploid meiosis. They were repaired in a RAD51- and REC8-dependent manner, but independently of DMC1, presumably using the sister chromatid as a template. Additionally, turning meiosis into mitosis (MiMe genotype in haploids resulted in the production of balanced haploid gametes and restoration of fertility. The variability of the effect on meiosis of the absence of homologous chromosomes in different organisms is then discussed.

  13. Action of cis-dichlorobis (cyclopentylamine) platinum (2) (cis-PAD) on L5178Y cells of two strains inversely cross-sensitive to X-rays and UV-light. Part 1. Cytotoxicity

    International Nuclear Information System (INIS)

    The response to cis-PAD, an antitumour platinum complex, was studied in two strains of murine lymphoma L5178Y cross-sensitive to X-rays and UV light. Dose-survival relationship, DNA synthesis, formation of chromatid aberrations, progression through the cell cycle, and growth and viability changes after 1 h cis-PAD treatment at 370C were examined and compared with respective effects of X-rays and UV-light. In both strains studied, cis-PAD causes immediate inhibition of progression through the cell cycle, reduced rate of DNA synthesis, delayed appearance of chromatid aberrations and delayed death. However, there is a marked difference in sensitivity to cis-PAD between L5178Y-S strain (D0 ca.5.8 μg/ml) and L5178Y-R strain (D0 ca. 2.5μg/ml). In both strains a close resemblance was found between dose-survival relationship after cis-PAD and UV-light treatment, respectively. (author)

  14. Nanoceria have no genotoxic effect on human lens epithelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Pierscionek, Barbara K; Yasseen, Akeel A [School of Biomedical Sciences, University of Ulster, Coleraine, BT52 1SA (United Kingdom); Li, Yuebin; Schachar, Ronald A; Chen, Wei [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Colhoun, Liza M, E-mail: b.pierscionek@ulster.ac.uk, E-mail: weichen@uta.edu [Centre for Vision and Vascular Sciences, School of Medicine, Dentistry and Biomedical Sciences, Queen' s University Belfast, Grosvenor Road, Belfast, BT12 6BA (United Kingdom)

    2010-01-22

    There are no treatments for reversing or halting cataract, a disease of the structural proteins in the eye lens, that has associations with other age-related degenerative conditions such as Alzheimer's disease. The incidence of cataract and associated conditions is increasing as the average age of the population rises. Protein folding diseases are difficult to assess in vivo as proteins and their age-related changes are assessed after extraction. Nanotechnology can be used to investigate protein changes in the intact lens as well as for a potential means of drug delivery. Nanoparticles, such as cerium oxide (CeO{sub 2}) which have antioxidant properties, may even be used as a means of treating cataract directly. Prior to use in treatments, nanoparticle genotoxicity must be tested to assess the extent of any DNA or chromosomal damage. Sister chromatid exchanges were measured and DNA damage investigated using the alkaline COMET assay on cultured human lens epithelial cells, exposed to 5 and 10 {mu}g ml{sup -1} of CeO{sub 2} nanoparticles (nanoceria). Nanoceria at these dosages did not cause any DNA damage or significant increases in the number of sister chromatid exchanges. The absence of genotoxic effects on lens cells suggests that nanoceria, in the doses and exposures tested in this study, are not deleterious to the eye lens and have the potential for use in studying structural alterations, in developing non-surgical cataract treatments and in investigating other protein folding diseases.

  15. A cell-cycle-stage-related chromosomal X-ray hypersensitivity in larval neuroblasts of Drosophila mei-9 and mei 41 mutants suggesting defective DNA double-strand break repair

    International Nuclear Information System (INIS)

    The authors have examined the chromosomal X-ray hypersensitivity in relation to the cell cycle in larval neuroblasts of the mutagen-sensitive and excision repair-defective mutant mei-9 and of the mutagen-sensitive and post-replication repair-defective mutant mei-41 of Drosophila melanogaster. When compared to wild-type cells, cells bearing the mei-9L1 allele produced unusually high levels in particular of chromatid deletions and to a lesser extent also of isochromatid deletions, but virtually no exchange aberrations. The chromosomal hypersensitivity is apparent at M1 when cells are irradiated in S or G2 but not when irradiated in G1. On the other hand, following irradiation cells bearing the mei-41D5 allele predominantly produce chromosome deletions. The phases of major sensitivity are the S and G1. Mei-9 and mei-41 mutants have been classified to date as proficient in DNA double-strand break repair. The data presented in this paper revealed an S-independent clastogenic hypersensitivity of mei-9 and mei-41 cells. They are interpreted as indicative evidence for the presence of impaired DNA double-strand break repair. The cell-cycle-related difference in the ratio of chromatid- versus chromosome-type deletions in both mutants suggests repair defects at partially different phases of the cell cycle in mei-9 and mei-41 mutant cells. (author). 47 refs.; 2 figs.; 5 tabs

  16. A Chinese hamster ovary cell line hypersensitive to ionizing radiation and deficient in repair replication

    International Nuclear Information System (INIS)

    An X-ray-sensitive Chinese hamster ovary cell line was isolated by means of a semi-automated procedure in which mutagenized cells formed colonies on top of agar, were X-irradiated, and were photographed at two later times. The author compared the photographs to identify colonies that displayed significant growth arrest. One of the colonies identified in this manner produced a stable line (irs1SF) that is hypersensitive to ionizing radiation. irs1SF performs only half as much X-ray-induced repair replication as the parental line, indicating a defect in excision repair. This defect is believed to be the primary cause of the line's radiosensitivity. Although irs1SF repairs DNA double-strand breaks at a normal rate, it repairs single-strand breaks more slowly than normal. irs1SF has an elevated number of spontaneous chromatid aberrations and produces significantly higher numbers of X-ray-induced chromatid aberrations after exposure during the G1 phase of the cell cycle. The line is hypomutable, with X-ray exposure inducing only one-third as many 6-thioguanine-resistant colonies as the parental line. 45 refs.; 10 figs.; 1 table

  17. Induction of genomic instability in TK6 human lymphoblasts exposed to 137Cs gamma radiation: comparison to the induction by exposure to accelerated 56Fe particles

    Science.gov (United States)

    Evans, Helen H.; Horng, Min-Fen; Ricanati, Marlene; Diaz-Insua, M.; Jordan, Robert; Schwartz, Jeffrey L.

    2003-01-01

    The induction of genomic instability in TK6 human lymphoblasts by exposure to (137)Cs gamma radiation was investigated by measuring the frequency and characteristics of unstable clones isolated approximately 36 generations after exposure. Clones surviving irradiation and control clones were analyzed for 17 characteristics including chromosomal aberrations, growth defects, alterations in response to a second irradiation, and mutant frequencies at the thymidine kinase and Na(+)/K(+) ATPase loci. Putative unstable clones were defined as those that exhibited a significant alteration in one or more characteristics compared to the controls. The frequency and characteristics of the unstable clones were compared in clones exposed to (137)Cs gamma rays or (56)Fe particles. The majority of the unstable clones isolated after exposure to either gamma rays or (56)Fe particles exhibited chromosomal instability. Alterations in growth characteristics, radiation response and mutant frequencies occurred much less often than cytogenetic alterations in these unstable clones. The frequency and complexity of the unstable clones were greater after exposure to (56)Fe particles than to gamma rays. Unstable clones that survived 36 generations after exposure to gamma rays exhibited increases in the incidence of dicentric chromosomes but not of chromatid breaks, whereas unstable clones that survived 36 generations after exposure to (56)Fe particles exhibited increases in both chromatid and chromosome aberrations.

  18. Cytogenetics of garlic (Allium sativum L.) in vitro culture

    International Nuclear Information System (INIS)

    Plants obtained from the culture of meristem tips, flower heads and/or basal plates showed no deviations in phenotype and chromosome number. Regenerants from meristem culture comprised solid tetraploids alongside diploids and mixoploids after colchicine treatment. Karyological instability was observed in the course of callus induction and long-term culture. Polyploid cells originated de novo in the in vitro culture. The final chromosomal constitution was dependent on the genotype of the donor plant, the type of the initial explant and the hormonal composition of the nutrient media. Garlic plants regenerated via callus cultures were phenotypically and karyologically variable, but even some regenerants with the unchanged karyotype showed differences in the phenotype. The nutrient medium induced neither mitotic aberrations in the Allium test nor point mutations in the Tradescantia test. The method of differential staining of sister chromatids in callus cells represents a novel approach to the study of in vitro plant genome instability. Higher sister-chromatid exchange frequencies and different cell-replication patterns in garlic callus were observed as compared to the intact meristem. (author)

  19. Assessment of adaptability of zebu cattle ( Bos indicus) breeds in two different climatic conditions: using cytogenetic techniques on genome integrity

    Science.gov (United States)

    Kumar, Anil; Waiz, Syma Ashraf; Sridhar Goud, T.; Tonk, R. K.; Grewal, Anita; Singh, S. V.; Yadav, B. R.; Upadhyay, R. C.

    2016-06-01

    The aim of this study was to evaluate the genome integrity so as to assess the adaptability of three breeds of indigenous cattle reared under arid and semi-arid regions of Rajasthan (Bikaner) and Haryana (Karnal) India. The cattle were of homogenous group (same age and sex) of indigenous breeds viz. Sahiwal, Tharparkar and Kankrej. A total of 100 animals were selected for this study from both climatic conditions. The sister chromatid exchanges (SCE's), chromosomal gaps and chromatid breaks were observed in metaphase plates of chromosome preparations obtained from in vitro culture of peripheral blood lymphocytes. The mean number of breaks and gaps in Sahiwal and Tharparkar of semi-arid zone were 8.56 ± 3.16, 6.4 ± 3.39 and 8.72 ± 2.04, 3.52 ± 6.29, respectively. Similarly, the mean number of breaks and gaps in Tharparkar and Kankrej cattle of arid zone were 5.26 ± 1.76, 2.74 ± 1.76 and 5.24 ± 1.84, 2.5 ± 1.26, respectively. The frequency of SCEs in chromosomes was found significantly higher ( P 0.05) was observed in the same zone. The analysis of frequency of CAs and SCEs revealed significant effects of environmental conditions on the genome integrity of animals, thereby indicating an association with their adaptability.

  20. Genotoxic effects of cadmium chloride on human amniotic fluid cells cultured in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Fogu, G. [Sassari Univ., Sassari (Italy). Dept. of Physiological, Biochemical and Cellular sciences; Sassari Univ., Sassari (Italy). Centre of Clinical Genetics; Congiu, A. M.; Sini, M. C.; Ladu, R. [Sassari Univ., Sassari (Italy). Dept. of Physiological, Biochemical and Cellular sciences; Campus, P. M.; Sanna, R.; Soro, G. [Sassari Univ., Sassari (Italy). Centre of Clinical Genetics

    2000-12-01

    In this study it has been reported the results of cytogenetic tests, namely a search for chromosome aberrations (CA) and sister chromatid exchanges (SCEs), performed on human amniotic fluid cells cultured and treated with Cadmium chloride. The cells from primary cultures were exposed to CdCl{sub 2} at 1 {mu}M and 10 {mu}M for 24 h. At the higher dose, no metaphases were scored and at the lower dose (1 {mu}M) no effects were evident on cell proliferation, and no chromosome aberrations were found. In the subsequent experiments were used cells from subcultures exposed to 1 {mu}M and 5 {mu}M CdCl{sub 2}. At the 5 {mu}M dose was evident the induction of chromatid breaks, while the frequency of sister chromatid exchanges shows a small increase, not statistically significant at the dose of 1 {mu}M. In this study it was positively demonstrated that amniotic fluid cells grown in vitro are reliable for testing various mutagenic or teratogenic substances. With regard to cadmium treatment results, it is evident a clastogenic effect of cadmium chloride but not a significant induction of SCEs. [Italian] In questo studio abbiamo riportato i risultati dei tests citogenici di valutazione degli scambi fra cromatidi fratelli (SCEs) e di induzione di aberrazioni cromosomiche (CA) condotti su colture cellulari di liquido amniotico umano, trattate con cloruro di cadmio. Le cellule delle colture primarie venivano esposte al CdCl{sub 2} a concentrazioni di 1 {mu}M 10 {mu}M per 24 h. Alla dose piu' alta (10 {mu}M) non sono state osservate metafasi, mentre alla dose piu' bassa (1 {mu}M) non sono stati evidenziati ne' effetti sulla proliferazione cellulare ne' CA. Nei successivi esperimenti il CdC{sub 2} e' stato testato su subcolture cellulari alle dosi di 1 {mu}M e 5 {mu}M. Alla dose di 5 {mu}M sono state evidenziate rotture cromatidiche, mentre la frequenza di SCE alla dose di 1 {mu}M ha mostrato un piccolo incremento, statisticamente non significativo. In questo

  1. Differential radiosensitivity phenotypes of DNA-PKcs mutations affecting NHEJ and HRR systems following irradiation with gamma-rays or very low fluences of alpha particles.

    Directory of Open Access Journals (Sweden)

    Yu-Fen Lin

    Full Text Available We have examined cell-cycle dependence of chromosomal aberration induction and cell killing after high or low dose-rate γ irradiation in cells bearing DNA-PKcs mutations in the S2056 cluster, the T2609 cluster, or the kinase domain. We also compared sister chromatid exchanges (SCE production by very low fluences of α-particles in DNA-PKcs mutant cells, and in homologous recombination repair (HRR mutant cells including Rad51C, Rad51D, and Fancg/xrcc9. Generally, chromosomal aberrations and cell killing by γ-rays were similarly affected by mutations in DNA-PKcs, and these mutant cells were more sensitive in G1 than in S/G2 phase. In G1-irradiated DNA-PKcs mutant cells, both chromosome- and chromatid-type breaks and exchanges were in excess than wild-type cells. For cells irradiated in late S/G2 phase, mutant cells showed very high yields of chromatid breaks compared to wild-type cells. Few exchanges were seen in DNA-PKcs-null, Ku80-null, or DNA-PKcs kinase dead mutants, but exchanges in excess were detected in the S2506 or T2609 cluster mutants. SCE induction by very low doses of α-particles is resulted from bystander effects in cells not traversed by α-particles. SCE seen in wild-type cells was completely abolished in Rad51C- or Rad51D-deficient cells, but near normal in Fancg/xrcc9 cells. In marked contrast, very high levels of SCEs were observed in DNA-PKcs-null, DNA-PKcs kinase-dead and Ku80-null mutants. SCE induction was also abolished in T2609 cluster mutant cells, but was only slightly reduced in the S2056 cluster mutant cells. Since both non-homologous end-joining (NHEJ and HRR systems utilize initial DNA lesions as a substrate, these results suggest the possibility of a competitive interference phenomenon operating between NHEJ and at least the Rad51C/D components of HRR; the level of interaction between damaged DNA and a particular DNA-PK component may determine the level of interaction of such DNA with a relevant HRR component.

  2. The ATPases of cohesin interface with regulators to modulate cohesin-mediated DNA tethering.

    Science.gov (United States)

    Çamdere, Gamze; Guacci, Vincent; Stricklin, Jeremiah; Koshland, Douglas

    2015-11-19

    Cohesin tethers together regions of DNA, thereby mediating higher order chromatin organization that is critical for sister chromatid cohesion, DNA repair and transcriptional regulation. Cohesin contains a heterodimeric ATP-binding Cassette (ABC) ATPase comprised of Smc1 and Smc3 ATPase active sites. These ATPases are required for cohesin to bind DNA. Cohesin's DNA binding activity is also promoted by the Eco1 acetyltransferase and inhibited by Wpl1. Recently we showed that after cohesin stably binds DNA, a second step is required for DNA tethering. This second step is also controlled by Eco1 acetylation. Here, we use genetic and biochemical analyses to show that this second DNA tethering step is regulated by cohesin ATPase. Furthermore, our results also suggest that Eco1 promotes cohesion by modulating the ATPase cycle of DNA-bound cohesin in a state that is permissive for DNA tethering and refractory to Wpl1 inhibition.

  3. Evaluation of the genotoxic potential of the alkaloid boldine in mammalian cell systems in vitro and in vivo.

    Science.gov (United States)

    Tavares, D C; Takahashi, C S

    1994-05-01

    Boldine is an alkaloid present in Peumus boldus (popularly called "boldo-do-chile" in Brazil) which has healing properties and is used for the treatment of gastrointestinal disorders. The possible clastogenic effect of the drug was tested in vitro on human peripheral blood lymphocytes by evaluating the induction of chromosome aberrations and sister-chromatid exchanges (SCEs). Cultures from different individuals were treated with boldine at concentrations of 10, 20 and 40 micrograms/ml of culture medium. The effect of the alkaloid was also tested in an in vivo assay using BALB/c mouse bone marrow cells. Boldine was administered to the animals by gavage at the concentrations of 225, 450 and 900 mg/kg body weight. Under the conditions used, boldine did not induce a statistically significant increase in the frequency of chromosome aberrations or SCEs in either test system. PMID:7513064

  4. In vitro genotoxicity of chlorinated drinking water processed from humus-rich surface water

    Energy Technology Data Exchange (ETDEWEB)

    Liimatainen, A.; Grummt, T.

    1988-11-01

    Chlorination by-products of drinking waters are capable of inducing sister chromatid exchanges (SCE) and chromosome aberrations (CA) in vitro, in addition to their mutagenic activity in the Ames test. Finnish drinking waters, processed from humus-rich surface water using chlorine disinfection, have been found to be highly mutagenic in the Ames' test. The highest activities have been found in the acidic, non-volatile fraction of the water concentrates using tester strain TA100 without metabolic activation by S9mix. The mutagenicities have varied between 500 and 14,000 induced revertants per liter. These figures are one to two magnitudes higher than those reported elsewhere. The authors studied five Finnish drinking water samples for their potency to exert genotoxic effects, SCEs and CAs, in mammalian cells in vitro (human peripheral lymphocytes and Chinese hamster lung fibroblasts).

  5. Heterozygosity for a Bub1 mutation causes female-specific germ cell aneuploidy in mice

    Energy Technology Data Exchange (ETDEWEB)

    Leland, Shawn; Nagarajan, Prabakaran; Polyzos, Aris; Thomas, Sharon; Samaan, George; Donnell, Robert; Marchetti, Francesco; Venkatachalam, Sundaresan

    2009-06-24

    Aneuploidy, the most common chromosomal abnormality at birth and the main ascertained cause of pregnancy loss in humans, originates primarily from chromosome segregation errors during oogenesis. Here we report that heterozygosity for a mutation in the mitotic checkpoint kinase gene, Bub1, induces aneuploidy in female germ cells of mice, and that the effect increases with advancing maternal age. Analysis of Bub1 heterozygous oocytes showed that aneuploidy occurred primarily during the first meiotic division and involved premature sister chromatid separation. Furthermore, aneuploidy was inherited in zygotes and resulted in the loss of embryos after implantation. The incidence of aneuploidy in zygotes was sufficient to explain the reduced litter size in matings with Bub1 heterozygous females. No effects were seen in germ cells from heterozygous males. These findings show that Bub1 dysfunction is linked to inherited aneuploidy in female germ cells and may contribute to the maternal age-related increase in aneuploidy and pregnancy loss.

  6. MUS81 promotes common fragile site expression

    DEFF Research Database (Denmark)

    Ying, Songmin; Minocherhomji, Sheroy; Chan, Kok Lung;

    2013-01-01

    Fragile sites are chromosomal loci with a propensity to form gaps or breaks during early mitosis, and their instability is implicated as being causative in certain neurological disorders and cancers. Recent work has demonstrated that the so-called common fragile sites (CFSs) often impair the fait......Fragile sites are chromosomal loci with a propensity to form gaps or breaks during early mitosis, and their instability is implicated as being causative in certain neurological disorders and cancers. Recent work has demonstrated that the so-called common fragile sites (CFSs) often impair...... the faithful disjunction of sister chromatids in mitosis. However, the mechanisms by which CFSs express their fragility, and the cellular factors required to suppress CFS instability, remain largely undefined. Here, we report that the DNA structure-specific nuclease MUS81-EME1 localizes to CFS loci in early...

  7. Mad revival of cancer

    Institute of Scientific and Technical Information of China (English)

    Hong Liu; Hongtao Yu

    2010-01-01

    @@ Aneuploidy (wrong numbers of chromosomes) is a hallmark of cancer cells and arises from chromosome missegregation in mitosis. To prevent aneuploidy, cells employ surveillance systems to monitor mitosis. The spindle checkpoint (also known as the mitotic checkpoint) is one such surveillance system conserved from yeast to man [1, 2]. During each mitosis, this check-point detects aberrant kinetochore-microtubule attachments, inhibits the anaphase-promoting complex or cy-closome (APC/C), stabilizes cyclin B1 and securin, and delays anaphase onset until all sister chromatids reach proper microtubule attachment. Mad2 is a criti-cal player of the spindle checkpoint and contributes to the inhibition of APC/C directly [3].

  8. The cytogenetic effects of the aqueous extracts of migratory locust (Locusta migratoria L.) in vitro.

    Science.gov (United States)

    Turkez, Hasan; Incekara, Umit; Güner, Adem; Aydın, Elanur; Dirican, Ebubekir; Togar, Başak

    2014-04-01

    One of the useful and most commonly cultivated commercially species, migratory locust (Locusta migratoria; Orthoptera), was investigated in light of genotoxic damage potentials. For this aim, we evaluated the genotoxic potentials of water soluble extracts of L. migratoria on cultured human blood cells. The micronucleus, sister chromatid exchange and structural chromosome aberration assays were applied to assess DNA and chromosomal damage produced by aqueous extracts in vitro. The extracts were added to the cultures at different concentrations ranging from 0 to 1000 mg/L. Our results indicated that these extracts did not exhibit genotoxicity at tested concentrations. We conclude that this in vitro approach for biomonitoring genotoxicity assessment is useful for comparing the potential health risks of edible insects. PMID:22872633

  9. Chromosome damage and clinical manifestation in a fetus and the mother after accidental 60Co exposure in Xinzhou

    International Nuclear Information System (INIS)

    The authors present the clinical effect and chromosome damage sustained by a fetus and the four months pregnant mother in an accidental 60Co exposure in November of 1992 in Xinzhou, Shanxi Province. The mother suffered from a moderate acute radiation sickness with ratardation of fetal development. After delivery, the infant's body length, body weight and head circumference were all lowered by three percentiles compared with the normals. Four months after the exposure, the assay of the mother's peripheral lymphocytes showed a chromosome aberration rate of 36%, while concomitant examination of the baby failed to reveal any chromosome abnormality although the sister chromatid exchange rate was remarkably higher than that of the mother and the normal control

  10. Calcium Signaling and Meiotic Exit at Fertilization in Xenopus Egg

    Directory of Open Access Journals (Sweden)

    Alexander A. Tokmakov

    2014-10-01

    Full Text Available Calcium is a universal messenger that mediates egg activation at fertilization in all sexually reproducing species studied. However, signaling pathways leading to calcium generation and the mechanisms of calcium-induced exit from meiotic arrest vary substantially among species. Here, we review the pathways of calcium signaling and the mechanisms of meiotic exit at fertilization in the eggs of the established developmental model, African clawed frog, Xenopus laevis. We also discuss calcium involvement in the early fertilization-induced events in Xenopus egg, such as membrane depolarization, the increase in intracellular pH, cortical granule exocytosis, cortical contraction, contraction wave, cortical rotation, reformation of the nuclear envelope, sperm chromatin decondensation and sister chromatid segregation.

  11. Interaction between some common genotoxic agents.

    Science.gov (United States)

    Beckman, L; Nordenson, I

    1986-01-01

    The clastogenic effects of arsenic, lead and sulphur dioxide and the protective effect of selenium were studied in short-term lymphocyte cultures. The three agents selected are the major toxic substances in emissions from copper smelters. Cells from non-smoking, healthy individuals were exposed to individual agents and combinations of the four agents (sodium arsenite, lead acetate, sodium sulphite and sodium selenite) and the cells were analysed for chromosome aberrations and sister chromatide exchanges. Selenium showed an antagonistic (protective) effect against the other agents. No synergistic effects were found, and the interactions between arsenic, lead and sulphur dioxide were mainly antagonistic. These rather unexpected findings indicate that mixed exposure from copper smelters, and other mixed exposures where arsenic, lead and sulphur dioxide are involved, may cause less genetic damage than expected and that an adequate dietary supplement of selenium may reduce the genotoxic effects of these agents. PMID:3793119

  12. Somatic cell chromosome changes in a population exposed to low levels of ionizing radiation

    International Nuclear Information System (INIS)

    The analysis of chromosomes from the cells of 897 plutonium workers is reported. Within three years, the number of controls alone analyzed for this study approximated the largest plutonium cytogenetic studies today including workers plus controls (81 compared to 84 in a 1979 French study and 94 in a 1982 British report). The number of subjects analyzed in the first three years were: new employees - 245; new employees assigned to plutonium work areas - 7; workers with less than 3% of maximum permissible systemic burden (MPSB) - 35; workers with less than 50% MPSB - 274; workers with greater than 50% of MPSB - 65; follow-up familial congenital cytogenetics at worker request (through Medical) - 6; polymorphic/variant chromosome constitutions - 242; re-sampling of workers with elevated aberration yields - 26; cell sample study - 28; sister-chromatid-exchange (SCE) study - 23; beryllium workers at Rocky Flats - 10; Hanford worker analyses - 5). 20 refs., 3 figs., 5 tabs

  13. The phenotype of FancB-mutant mouse embryonic stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Moon; Ko, Jun Ho; Choi, Yong Jun; Hu Lingchuan [Department of Molecular Medicine and Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 15355 Lambda Drive, San Antonio, TX 78245 (United States); Hasty, Paul, E-mail: hastye@uthscsa.edu [Department of Molecular Medicine and Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 15355 Lambda Drive, San Antonio, TX 78245 (United States)

    2011-07-01

    Fanconi anemia (FA) is a rare autosomal recessive disease characterized by bone marrow failure, developmental defects and cancer. There are multiple FA genes that enable the repair of interstrand crosslinks (ICLs) in coordination with a variety of other DNA repair pathways in a way that is poorly understood. Here we present the phenotype of mouse embryonic stem (ES) cells mutated for FancB. We found FancB-mutant cells exhibited reduced cellular proliferation, hypersensitivity to the crosslinking agent mitomycin C (MMC), increased spontaneous and MMC-induced chromosomal abnormalities, reduced spontaneous sister chromatid exchanges (SCEs), reduced gene targeting, reduced MMC-induced Rad51 foci and absent MMC-induced FancD2 foci. Since FancB is on the X chromosome and since ES cells are typically XY, FancB is an excellent target for an epistatic analysis to elucidate FA's role in ICL repair.

  14. Identification of RecQL1 as a Holliday junction processing enzyme in human cell lines

    Science.gov (United States)

    LeRoy, Gary; Carroll, Robert; Kyin, Saw; Seki, Masayuki; Cole, Michael D.

    2005-01-01

    Homologous recombination provides an effective way to repair DNA double-strand breaks (DSBs) and is required for genetic recombination. During the process of homologous recombination, a heteroduplex DNA structure, or a ‘Holliday junction’ (HJ), is formed. The movement, or branch migration, of this junction is necessary for recombination to proceed correctly. In prokaryotes, the RecQ protein or the RuvA/RuvB protein complex can promote ATP-dependent branch migration of Holliday junctions. Much less is known about the processing of Holliday junctions in eukaryotes. Here, we identify RecQL1 as a predominant ATP-dependent, HJ branch migrator present in human nuclear extracts. A reduction in the level of RecQL1 induced by RNA interference in HeLa cells leads to an increase in sister chromatid exchange. We propose that RecQL1 is involved in the processing of Holliday junctions in human cells. PMID:16260474

  15. Cohesin is needed for bipolar mitosis in human cells.

    Science.gov (United States)

    Díaz-Martínez, Laura A; Beauchene, Nicole A; Furniss, Katherine; Esponda, Pedro; Giménez-Abián, Juan F; Clarke, Duncan J

    2010-05-01

    Multi-polar mitosis is strongly linked with aggressive cancers and it is a histological diagnostic of tumor-grade. However, factors that cause chromosomes to segregate to more than two spindle poles are not well understood. Here we show that cohesins Rad21, Smc1 and Smc3 are required for bipolar mitosis in human cells. After Rad21 depletion, chromosomes align at the metaphase plate and bipolar spindles assemble in most cases, but in anaphase the separated chromatids segregate to multiple poles. Time-lapse microscopy revealed that the spindle poles often become split in Rad21-depleted metaphase cells. Interestingly, exogenous expression of non-cleavable Rad21 results in multi-polar anaphase. Since cohesins are present at the spindle poles in mitosis, these data are consistent with a non-chromosomal function of cohesin. PMID:20436271

  16. WRNIP1 functions upstream of DNA polymerase η in the UV-induced DNA damage response.

    Science.gov (United States)

    Yoshimura, Akari; Kobayashi, Yume; Tada, Shusuke; Seki, Masayuki; Enomoto, Takemi

    2014-09-12

    WRNIP1 (WRN-interacting protein 1) was first identified as a factor that interacts with WRN, the protein that is defective in Werner syndrome (WS). WRNIP1 associates with DNA polymerase η (Polη), but the biological significance of this interaction remains unknown. In this study, we analyzed the functional interaction between WRNIP1 and Polη by generating knockouts of both genes in DT40 chicken cells. Disruption of WRNIP1 in Polη-disrupted (POLH(-/-)) cells suppressed the phenotypes associated with the loss of Polη: sensitivity to ultraviolet light (UV), delayed repair of cyclobutane pyrimidine dimers (CPD), elevated frequency of mutation, elevated levels of UV-induced sister chromatid exchange (SCE), and reduced rate of fork progression after UV irradiation. These results suggest that WRNIP1 functions upstream of Polη in the response to UV irradiation.

  17. Experimental verification for in vitro technique confirmation of bystander effect induced by gamma radiation in CHO-K1 cell line; Verificacao experimental para confirmacao da tecnica in vitro do efeito bystander induzido por radiacao gama na linhagem celular CHO-K1

    Energy Technology Data Exchange (ETDEWEB)

    Viana, P.H.L.; Goes, A.M.; Gomes, D.A., E-mail: pedroleroybio@hotmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento Bioquimica e Imunologia. Lab. de Imunologia Celular e Molecular; Grynberg, S.E., E-mail: seg@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2013-08-15

    The bystander effect refers to biological responses detected in cells not directly irradiated but influenced, somehow, by signals transmitted from neighboring irradiated cells. These biological responses include sister chromatid exchange, mutations, micronucleus formation, chromosomal aberrations, carcinogenesis, apoptosis and necrosis. Although its existence is unquestionable, the mechanisms involved on triggering the bystander effect are not yet completely elucidated. Previous studies have shown that the bystander effect depends on a large variety of parameters including the radiation dose, the dose rate, the type of radiation and type of cells or tissue. This study aims to confirm the technique previously used in the literature in human cell lines for the bystander effect verification. The results suggest that the working conditions adopted by the group show technical efficiency and enables the reproduction of the bystander effect. (author)

  18. Isochromosome X mosaicism in a child with Kabuki syndrome phenotype: A rare cytogenetic association

    Science.gov (United States)

    Kumar, Jeevan M.; Gowrishankar, Kalpana; Vasanthi, T.; Kumar, R. Ashok; Jayasudha, T.

    2011-01-01

    Isochromosome is a structurally unbalanced chromosome consisting of two short arms or two long arms, which are derived by abnormal centromere division or sister-chromatid exchange. Most autosomal isochromosomes are unusual, while those involving sex chromosomes are common. Kabuki syndrome (KS, OMIM 147920) is a multiple malformation/mental retardation syndrome of unknown etiology. A conventional cytogenetic study on lymphocytes from a 4-year-old girl with physical features suggestive of KS was found to have mosaicism for isochromosome for the long arm of the X. Although most manifestations present in this patient have been described before, this report is a rare association of clinical and cytogenetic findings in this syndrome. A genome-wide analysis and a larger number of patient groups studied could improve our understanding of the genetic basis of KS. PMID:22346002

  19. [239Pu and chromosomal aberrations in human peripheral blood lymphocytes].

    Science.gov (United States)

    Okladnikova, N D; Osovets, S V; Kudriavtseva, T I

    2009-01-01

    The genome status in somatic cells was assessed using the chromosomal aberration (CA) test in peripheral blood lymphocytes from 194 plutonium workers exposed to occupational radiation mainly from low-transportable compounds of airborne 230Pu. Pu body burden at the time of cytogenetic study varied from values close to the method sensitivity to values multiply exceeding the permissible level. Standard (routine) methods of peripheral blood lymphocytes cultivation were applied. Chromatid- and chromosomal-type structural changes were estimated. Aberrations were estimated per 100 examined metaphase cells. The quantitative relationship between the CA frequency and Pu body burden and the absorbed dose to the lung was found. Mathematical processing of results was carried out based on the phenomenological model. The results were shown as theoretical and experimental curves. The threshold of the CA yield was 0.43 +/- 0.03 kBq (Pu body burden) and 6.12 +/- 1.20 cGy (absorbed dose to the lung).

  20. Human Sperm Chromosome Analysis—Study on Human Sperm Chromosome Mutagenesis Induced by Carbon Disulfide

    Institute of Scientific and Technical Information of China (English)

    LEJUN-YI; FUXIAO-MIN

    1996-01-01

    The aim of this study was to investigate the effect CS2 of on human sperm chromosomal aberration.The human sperm/hamster egg fusion techniquse was used to analyze 203 human sperm chromosome complement form 9 healthy volunteers.The incidence of numerical aberration was 1.0%,and that of structural chromosome aberration was 5.9% and total abnormalities was 6.9%.Structural aberrations consisted of breaks,deletions, centric rings,fragments,and chromatid exchange.The results from high concentration group(10μmol·L-1 CS2)showed that the incidence of chromosomal aberration rate was significantly higher than that of the control group.The results indicate that high concentration of CS2 might directly cause mutatenesis f the germ cell.

  1. Biomonitoring human exposure to environmental carcinogenic chemicals

    DEFF Research Database (Denmark)

    Farmer, P.B.; Sepai, O.; Lawrence, R.;

    1996-01-01

    A coordinated study was carried out on the development, evaluation and application of biomonitoring procedures for populations exposed to environmental genotoxic pollutants. The procedures used involved both direct measurement of DNA or protein damage (adducts) and assessment of second biological...... effects (mutation and cytogenetic damage). Adduct detection at the level of DNA or protein (haemoglobin) was carried out by 32P-postlabelling, immunochemical, HPLC or mass spectrometric methods. Urinary excretion products resulting from DNA damage were also estimated (immunochemical assay, mass...... aberrations and sister chromatid exchanges) and mutation frequency was estimated at a number of loci including the hprt gene and genes involving in cancer development. Blood and urine samples from individuals exposed to urban pollution were collected. Populations exposed through occupational or medical...

  2. 20-Mb duplication of chromosome 9p in a girl with minimal physical findings and normal IQ: narrowing of the 9p duplication critical region to 6 Mb.

    Science.gov (United States)

    Bonaglia, Maria Clara; Giorda, Roberto; Carrozzo, Romeo; Roncoroni, Maria Elena; Grasso, Rita; Borgatti, Renato; Zuffardi, Orsetta

    2002-10-01

    We studied the case of a girl with a partial 9p duplication, dup(9)(p22.1 --> p13.1). Molecular cytogenetics studies defined the chromosome 9 rearrangement as a direct duplication of 20 Mb from D9S1213 to D9S52. Microsatellite analysis demonstrated the presence of a double dosage of the paternal alleles and demonstrated that the duplication occurred between sister chromatids. The patient's phenotype was almost normal, with a few minor anomalies (dolichocephaly, crowded teeth, high arched palate) and normal IQ. The breakpoint's location in this patient and previously reported cases suggest that the critical region for the 9p duplication syndrome lies within a 6-Mb portion of chromosome 9p22 between markers D9S267 and D9S1213.

  3. Suppression of allelic recombination and aneuploidy by cohesin is independent of Chk1 in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Shay Covo

    Full Text Available Sister chromatid cohesion (SCC, which is established during DNA replication, ensures genome stability. Establishment of SCC is inhibited in G2. However, this inhibition is relived and SCC is established as a response to DNA damage, a process known as Damage Induced Cohesion (DIC. In yeast, Chk1, which is a kinase that functions in DNA damage signal transduction, is considered an activator of SCC through DIC. Nonetheless, here we show that, unlike SCC mutations, loss of CHK1 did not increase spontaneous or damage-induced allelic recombination or aneuploidy. We suggest that Chk1 has a redundant role in the control of DIC or that DIC is redundant for maintaining genome stability.

  4. Suppression of Allelic Recombination and Aneuploidy by Cohesin Is Independent of Chk1 in Saccharomyces cerevisiae

    Science.gov (United States)

    Gordenin, Dmitry A.; Resnick, Michael A.

    2014-01-01

    Sister chromatid cohesion (SCC), which is established during DNA replication, ensures genome stability. Establishment of SCC is inhibited in G2. However, this inhibition is relived and SCC is established as a response to DNA damage, a process known as Damage Induced Cohesion (DIC). In yeast, Chk1, which is a kinase that functions in DNA damage signal transduction, is considered an activator of SCC through DIC. Nonetheless, here we show that, unlike SCC mutations, loss of CHK1 did not increase spontaneous or damage-induced allelic recombination or aneuploidy. We suggest that Chk1 has a redundant role in the control of DIC or that DIC is redundant for maintaining genome stability. PMID:25551702

  5. Delayed SCE frequency of rat bone marrow cells after radon inhalation

    International Nuclear Information System (INIS)

    Cytogenetic tests can reflect in vivo cellular modifications during development of induced neoplasic lesions. These last years, a new experimental in vivo cytogenetic test has been widely developed: Sister chromatid exchanges (SCE) especially on bone marrow cells. This study establishes the relationships between SCE in the bone marrow of rat and post exposure time following whole body neutron irradiation and radon inhalation. From the observed data a two stages response is pointed out. The first stage is thought to correspond to direct DNA damage and is characterized by a short term increase of bone marrow SCE followed by a rapid decrease up to the control values. The second one is marked by a delayed increase of SCE followed by a plateau significantly higher than the control values. From neutron radon exposure and from previously observed data this second stage strongly suggests a modification of the whole organism induced by 'mutagen/carcinogen' modified target organs

  6. Defective repair of uracil causes telomere defects in mouse hematopoietic cells.

    Science.gov (United States)

    Vallabhaneni, Haritha; Zhou, Fang; Maul, Robert W; Sarkar, Jaya; Yin, Jinhu; Lei, Ming; Harrington, Lea; Gearhart, Patricia J; Liu, Yie

    2015-02-27

    Uracil in the genome can result from misincorporation of dUTP instead of dTTP during DNA synthesis, and is primarily removed by uracil DNA glycosylase (UNG) during base excision repair. Telomeres contain long arrays of TTAGGG repeats and may be susceptible to uracil misincorporation. Using model telomeric DNA substrates, we showed that the position and number of uracil substitutions of thymine in telomeric DNA decreased recognition by the telomere single-strand binding protein, POT1. In primary mouse hematopoietic cells, uracil was detectable at telomeres, and UNG deficiency further increased uracil loads and led to abnormal telomere lengthening. In UNG-deficient cells, the frequencies of sister chromatid exchange and fragility in telomeres also significantly increased in the absence of telomerase. Thus, accumulation of uracil and/or UNG deficiency interferes with telomere maintenance, thereby underscoring the necessity of UNG-initiated base excision repair for the preservation of telomere integrity. PMID:25572391

  7. Mitotic fidelity requires transgenerational action of a testis-restricted HP1.

    Science.gov (United States)

    Levine, Mia T; Vander Wende, Helen M; Malik, Harmit S

    2015-07-07

    Sperm-packaged DNA must undergo extensive reorganization to ensure its timely participation in embryonic mitosis. Whereas maternal control over this remodeling is well described, paternal contributions are virtually unknown. In this study, we show that Drosophila melanogaster males lacking Heterochromatin Protein 1E (HP1E) sire inviable embryos that undergo catastrophic mitosis. In these embryos, the paternal genome fails to condense and resolve into sister chromatids in synchrony with the maternal genome. This delay leads to a failure of paternal chromosomes, particularly the heterochromatin-rich sex chromosomes, to separate on the first mitotic spindle. Remarkably, HP1E is not inherited on mature sperm chromatin. Instead, HP1E primes paternal chromosomes during spermatogenesis to ensure faithful segregation post-fertilization. This transgenerational effect suggests that maternal control is necessary but not sufficient for transforming sperm DNA into a mitotically competent pronucleus. Instead, paternal action during spermiogenesis exerts post-fertilization control to ensure faithful chromosome segregation in the embryo.

  8. Mosaicism for combined tetrasomy of chromosomes 8 and 18 in a dysmorphic child: A result of failed tetraploidy correction?

    Directory of Open Access Journals (Sweden)

    Lybæk Helle

    2009-05-01

    Full Text Available Abstract Background Mosaic whole-chromosome tetrasomy has not previously been described as a cause of fetal malformations. Case presentation In a markedly dysmorphic child with heart malformations and developmental delay, CGH analysis of newborn blood DNA suggested a 50% dose increase of chromosomes 8 and 18, despite a normal standard karyotype investigation. Subsequent FISH analysis revealed leukocytes with four chromosomes 8 and four chromosomes 18. The child's phenotype had resemblance to both mosaic trisomy 8 and mosaic trisomy 18. The double tetrasomy was caused by mitotic malsegregation of all four chromatids of both chromosome pairs. A possible origin of such an error is incomplete correction of a tetraploid state resulting from failed cytokinesis or mitotic slippage during early embryonic development. Conclusion This unique case suggests that embryonic cells may have a mechanism for tetraploidy correction that involves mitotic pairing of homologous chromosomes.

  9. The role of RecQ helicases in non-homologous end-joining

    DEFF Research Database (Denmark)

    Keijzers, Guido; Maynard, Scott; Shamanna, Raghavendra A;

    2014-01-01

    Abstract DNA double-strand breaks are highly toxic DNA lesions that cause genomic instability, if not efficiently repaired. RecQ helicases are a family of highly conserved proteins that maintain genomic stability through their important roles in several DNA repair pathways, including DNA double......-strand break repair. Double-strand breaks can be repaired by homologous recombination (HR) using sister chromatids as templates to facilitate precise DNA repair, or by an HR-independent mechanism known as non-homologous end-joining (NHEJ) (error-prone). NHEJ is a non-templated DNA repair process, in which DNA...... termini are directly ligated. Canonical NHEJ requires DNA-PKcs and Ku70/80, while alternative NHEJ pathways are DNA-PKcs and Ku70/80 independent. This review discusses the role of RecQ helicases in NHEJ, alternative (or back-up) NHEJ (B-NHEJ) and microhomology-mediated end-joining (MMEJ) in V...

  10. Assessment of in vitro genotoxic and cytotoxic effects of flurbiprofen on human cultured lymphocytes.

    Science.gov (United States)

    Timocin, Taygun; Ila, Hasan Basri; Dordu, Tuba; Husunet, Mehmet Tahir; Tazehkand, Mostafa Norizadeh; Valipour, Ebrahim; Topaktas, Mehmet

    2016-01-01

    Flurbiprofen is non-steroidal anti-inflammatory drug which is commonly used for its analgesic, antipyretic, and anti-inflammatory effects. The purpose of the study was to explore the genotoxic and cytotoxic effects of flurbiprofen in human cultured lymphocytes by sister chromatid exchange, chromosome aberration, and cytokinesis-blocked micronucleus tests. 10, 20, 30, and 40 μg/mL concentrations of flurbiprofen (solvent is DMSO) were used to treatment of human cultured lymphocytes at two different treatment periods (24 and 48 h). Flurbiprofen had no significant genotoxic effect in any of these tests. But exposing to flurbiprofen for 24 and 48 h led to significant decrease on proliferation index, mitotic index, and nuclear division index (NDI). Also, all decreases were concentration-dependent (except NDI at 24 h treatment period). Consequently, the findings of this research showed that flurbiprofen had cytotoxic effects in human blood lymphocytes.

  11. Silver stained core-like structures in chinese hamster metaphase Chromosomes.

    Science.gov (United States)

    Kaiserman, M Z; Burkholder, G D

    1980-01-01

    Chinese hamster metaphase chromosomes, subjected to prolonged hypotonic pretreatment and subsequently stained with ammoniacal silver, contained a darkly-stained core-like structure in each chromatid, surrounded by a halo of dispersed chromatin which was pale yellow to brown in color. The core was variable in its appearance, ranging from a continuous linear configuration to a spiral structure or a discontinuous, particulate structure. Within the centromeric regions, the cores frequently appeared more intensely stained than elsewhere in the chromosome. The nucleolus organizers also stained darkly and appeared to be attached to the core-like structures. It remains to be determined whether the cores represent a real component of metaphase chromosome structure, or whether they are artifacts resulting from abnormal chromatin aggregation arising at the time of chromosome preparation. PMID:6165446

  12. Structure and function of centromeric and pericentromeric heterochromatin in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Lauriane eSimon

    2015-11-01

    Full Text Available The centromere is a specific chromosomal region where the kinetochore assembles to ensure the faithful segregation of sister chromatids during mitosis and meiosis. Centromeres are defined by a local enrichment of the specific histone variant CenH3 mostly at repetitive satellite sequences. A larger pericentromeric region containing repetitive sequences and transposable elements surrounds the centromere that adopts a particular chromatin state characterized by specific histone variants and post-translational modifications and forms a transcriptionally repressive chromosomal environment. In the model organism Arabidopsis thaliana centromeric and pericentromeric domains form conspicuous heterochromatin clusters called chromocenters in interphase. Here we discuss, using Arabidopsis as example, recent insight into mechanisms involved in maintenance and establishment of centromeric and pericentromeric chromatin signatures as well as in chromocenter formation.

  13. In vitro genotoxic evaluation of the medicinal plant Chenopodium ambrosioides L.

    Science.gov (United States)

    Gadano, A; Gurni, A; López, P; Ferraro, G; Carballo, M

    2002-06-01

    Chenopodium ambrosioides (Chenopodiaceae) is an anthelmintic herb used in Latin-America's folk medicine. The aim of this work is to evaluate genetic damage induced by decoction and infusion of this plant which were assayed in different concentrations (1, 10, 100, 1000 microg/ml), by addition of the extract to human lymphocyte cell cultures. The endpoints evaluated were chromosomal aberrations (CA), sister chromatid exchanges (SCE), cell proliferation kinetics (CPK) and mitotic indexes (MI). The repeated measure analysis of variance was used for statistic evaluation of the results. The results showed (a) a statistical increase in the percentage of cells with CA and in the frequency of SCE when cultures were exposed to both preparations of Paico, (b) a decrease in MI of both preparations assayed, although no modification in the CPK values either in the infusion or in the decoction was observed. These results suggest a possible genotoxic effect of both preparations, probably due to different active principles. PMID:12020922

  14. Accuracy of preimplantation genetic diagnosis (PGD) of single gene and chromosomal disorders

    Energy Technology Data Exchange (ETDEWEB)

    Verlinsky, Y.; Strom, C.; Rechitsky, S. [Reproductive Genetics Institute, Chicage, IL (United States)] [and others

    1994-09-01

    We have developed a polar body inferred approach for preconception diagnosis of single gene and chromosomal disorders. Preconception PCR or FISH analysis was performed in a total of 310 first polar bodies for the following genetic conditions: cystic fibrosis, hemophilia A, alpha-1-antitrypsin deficiency, Tay Sachs disease, retinitis pigmentosa and common chromosomal trisomies. An important advantage of this approach is the avoidance of sperm (DNA) contamination, which is the major problem of PGD. We are currently applying FISH analysis of biopsied blastomeres, in combination with PCR or separately, and have demonstrated a significant improvement of the accuracy of PGD of X-linked disorders at this stage. Our data have also demonstrated feasibility of the application of FISH technique for PGD of chromosomal disorders. It was possible to detect chromosomal non-disjunctions and chromatid malsegregations in the first meiotic division, as well as to evaluate chromosomal mutations originating from the second meiotic nondisjunction.

  15. Evaluation of cytogenetic effects of a naturally occurring non-ice-nucleation Pseudomonas fluorescens strain in Chinese hamster ovary (CHO) cells.

    Science.gov (United States)

    Caruso, P; Andreozzi, L; Motta, S; Mosesso, P

    1995-01-01

    One of the main methods for eliminating ice-nucleation-active (INA+) bacteria the micro-organisms responsible for frost injuries to plants at mild freezing temperatures, is the use, as competitors, of other naturally occurring non-nucleating strains (non-INA). In the present article we investigated the cytogenetic effects of a naturally occurring non-INA strain of Pseudomonas fluorescens (MS 1640 R3), evaluating the induction of chromosomal aberrations and sister chromatid exchanges (SCEs) in Chinese hamster ovary (CHO) cells in the absence and presence of rat S9 metabolism. The results obtained did not show any increase in either chromosomal aberrations or SCEs, both in the absence and presence of rat S9 metabolism when used as i) intact bacteria cells, ii) sonicated bacteria (i.e., potential endotoxins), or iii) metabolic bacterial products (i.e., potential exotoxins) released in the growth medium. PMID:8584981

  16. Evidence of increased chromosomal instability in infertile males after exposure to mitomycin C and caffeine

    Institute of Scientific and Technical Information of China (English)

    Fotini Papachristou; Theodore Lialiaris; Stavros Touloupidis; Christos Kalaitzis; Constantinos Simopoulos; Nikolaos Sofikitis

    2006-01-01

    Aim: To evaluate the genetic instability of 11 fertile and 25 infertile men. Methods: The methodology of sister chromatid exchanges (SCEs) was applied to cultures of peripheral blood lymphocytes, and the levels of SCEss were analyzed as a quantitative index of genotoxicity, along with the values of the mitotic index (MI) and the proliferation rate index (PRI) as qualitative indices of cytotoxicity and cytostaticity, respectively. The genotoxic and antineoplastic agent, mitomycin C (MMC), and caffeine (CAF) - both well-known inhibitors of DNA repair mechanism - were used in an attempt to induce chromosomal instability in infertile men, so as to more easily detect the probable underlying damage on DNA. Results: Our experiments illustrated that infertile men, compared with fertile ones, demonstrated a statistically significant DNA instability in peripheral blood lymphocytes after being exposed simultaneously to MMC and CAF. Conclusion: The current study showed vividly that there was genetic instability in infertile men which probably contributes to the development of an impaired reproductive capacity.

  17. Irradiated and not irradiated fetal bovine sera. Comparative studies by cyto- and genotoxicity assays

    International Nuclear Information System (INIS)

    Full text: Fetal bovine sera (FBS) represent one of the main trophic supports in cell culture media. Due to their origin, they can be vehicle of different toxic elements, biotic or not, that could affect negatively cells in vitro. One of the most disseminated methods to eliminate contamination sources is the sterilization by gamma irradiation. This practice, unless carefully dosed, may constitute in an inducing source of cyto- and genotoxicity. The aim of the present work was to study comparatively irradiated and not irradiated FBS batches to determine presence/absence of deleterious elements. The genotoxicity tests performed were: comet assay, sister chromatid exchange and micronuclei frequency; the cytotoxicity assays employed were: plate efficacy, growth promotion, mycoplasma and diarrhea bovine virus presence. Results showed non statistical significant differences between irradiated and not irradiated sera (p>0.05). These findings could suggest that the doses employed for irradiation are effective to achieve sterilization without producing cyto- and genotoxic factors. (author)

  18. Aqueous extracts of Lippia turbinata and Aloysia citriodora (Verbenaceae): assessment of antioxidant capacity and DNA damage.

    Science.gov (United States)

    Portmann, Erika; Nigro, Marcela M López; Reides, Claudia G; Llesuy, Susana; Ricco, Rafael A; Wagner, Marcelo L; Gurni, Alberto A; Carballo, Marta A

    2012-03-01

    The aim of the present work was to make a contribution to the knowledge of aqueous extracts of Lippia turbinata and Aloysia citriodora (Verbenaceae; infusion and decoction) in relation with the establishment of its antioxidant activity and lack of DNA damage, for its potential use in therapeutics. The cytogenotoxic profile was evaluated through genotoxic biomarkers such as mitotic index, cellular proliferation kinetics, sister chromatid exchanges, single-cell gel electrophoresis assay, and micronucleus test in human peripheral blood lymphocyte cultures. No statistical differences were found (P > .05) between control and exposed cultures, even between both aqueous extracts. The total antioxidant capacity was shown to be higher in the decoction than in the infusion and both aqueous extracts protected against protein carbonylation and lipid peroxidation, the decoction being more efficient than the infusion (P < .005). These results suggest the safe use of these medicinal plants as chemoecologic agents in therapeutics. PMID:22427199

  19. Final report. Human artificial episomal chromosome (HAEC) for building large genomic libraries

    Energy Technology Data Exchange (ETDEWEB)

    Jean-Michael H. Vos

    1999-12-09

    Collections of human DNA fragments are maintained for research purposes as clones in bacterial host cells. However for unknown reasons, some regions of the human genome appear to be unclonable or unstable in bacteria. Their team has developed a system using episomes (extrachromosomal, autonomously replication DNA) that maintains large DNA fragments in human cells. This human artificial episomal chromosomal (HAEC) system may prove useful for coverage of these especially difficult regions. In the broader biomedical community, the HAEC system also shows promise for use in functional genomics and gene therapy. Recent improvements to the HAEC system and its application to mapping, sequencing, and functionally studying human and mouse DNA are summarized. Mapping and sequencing the human genome and model organisms are only the first steps in determining the function of various genetic units critical for gene regulation, DNA replication, chromatin packaging, chromosomal stability, and chromatid segregation. Such studies will require the ability to transfer and manipulate entire functional units into mammalian cells.

  20. Children's exposure to environmental pollutants and biomarkers of genetic damage. II. Results of a comprehensive literature search and meta-analysis

    DEFF Research Database (Denmark)

    Neri, Monica; Ugolini, Donatella; Bonassi, Stefano;

    2005-01-01

    aberrations (CA) and micronuclei (MN) but not sister chromatid exchanges (SCE) were found consistently increased in children exposed to environmental pollutants. Meta-analysis of the studies reporting SCE in cord blood showed similar levels of SCE in exposed and in non-exposed newborns. Exposure to airborne......-DNA adducts were found in fetal than in maternal tissue, suggesting a specific susceptibility of the fetus to this class of ubiquitous environmental pollutants. According to these findings, future research and biomonitoring programs on children would greatly benefit from the inclusion of selected biomarkers...... pollutants, soil and drinking water contaminants, mostly increased CA and, to a lesser extent, MN levels in children. The effect of exposure to airborne urban pollutants was consistently reported by field studies measuring DNA, albumin and hemoglobin adducts. Prenatal (in utero) and postnatal exposure...

  1. The presence of synaptic and chromosome disjunction mutants in Cenchrus ciliaris (Poaceae: Paniceae

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    N. C. Visser

    1999-12-01

    Full Text Available Synaptic mutants are present in  Cenchrus ciliaris L This species, due to the presence of linear bivalents and occasion­al trivalents and quadrivalents, is an intermediate desynaptic species. In addition, geographical distribution and environmental factors, such as high temperatures and low humidity, could also have had an influence on the desynapsis observed.The disjunction of chromosomes during anaphase I was mostly abnormal in this desynaptic species. Precocious disjunction of chromosomes into chromatids occurred during anaphase I Due to the high incidence of this chromosome abnormality, a mutant gene,  'pc'  responsible for the disjunction of chromosomes, must be present. The absence of cytokinesis in one specimen indicates a recessive mutant gene,  'va' to be active in this species.

  2. Medical and biological aspects of the Chernobyl nuclear accident influence on the population of the Republic of Moldova

    International Nuclear Information System (INIS)

    During the period 1996-2004, 850 patients - Chernobyl accident consequences cleaning up participants (CACCP) with nervous, cardiovascular and digestive system morbidity and their children were investigated, inclusively the clinical, immunological and cytogenetic analysis. The clinical investigations indicates that the CACCP patients compared to patients of a control group, were more susceptible to infectious and noninfectious diseases, with the prevalence of large polymorphism of nervous, cardiovascular and digestive system, which were accompanied by with circulatory disorder of the vegetative nervous system. The immunological analysis elucidates alterations in the immune system of the CACCP, expressed through the increase of the activity of humeral indices of immunity and decrease of the cell immunity system expressed through the decrease of total T-lymphocytes and B-lymphocytes. The correlation and simple regression analysis demonstrated the linear negative dependence between some immunological indices and dose level r=-0.54. The hyper compensatory intensity of humoral immunity and natural resistance and clear tendency to T-cell immunity insufficiency are revealed with monoclonal antibodies to CD-19, CD-3, CD-4, CD-8, CD-16 and rosette forming reactions. Cytogenetic research of the lymphocyte cultures of peripheral blood of CACCP living in the Republic of Moldova in the 10-12 years after the accident and their children, elucidated the deterioration of the hereditary system, being expressed through high level of genomic, chromosomal, and chromatid type aberration. In the adults populations dominated the chromosomal type of aberrations, and in the children populations prevailed the chromatid type. On the base of cytogenetic markers, it has been determined that the radiation affection of CACCP indicated by the official physical doses not always coincided with the data of the biological indicators

  3. Non-SMC condensin I complex proteins control chromosome segregation and survival of proliferating cells in the zebrafish neural retina

    Directory of Open Access Journals (Sweden)

    Harris William A

    2009-07-01

    Full Text Available Abstract Background The condensation of chromosomes and correct sister chromatid segregation during cell division is an essential feature of all proliferative cells. Structural maintenance of chromosomes (SMC and non-SMC proteins form the condensin I complex and regulate chromosome condensation and segregation during mitosis. However, due to the lack of appropriate mutants, the function of the condensin I complex during vertebrate development has not been described. Results Here, we report the positional cloning and detailed characterization of retinal phenotypes of a zebrafish mutation at the cap-g locus. High resolution live imaging reveals that the progression of mitosis between prometa- to telophase is delayed and that sister chromatid segregation is impaired upon loss of CAP-G. CAP-G associates with chromosomes between prometa- and telophase of the cell cycle. Loss of the interaction partners CAP-H and CAP-D2 causes cytoplasmic mislocalization of CAP-G throughout mitosis. DNA content analysis reveals increased genomic imbalances upon loss of non-SMC condensin I subunits. Within the retina, loss of condensin I function causes increased rates of apoptosis among cells within the proliferative ciliary marginal zone (CMZ whereas postmitotic retinal cells are viable. Inhibition of p53-mediated apoptosis partially rescues cell numbers in cap-g mutant retinae and allows normal layering of retinal cell types without alleviating their aberrant nuclear sizes. Conclusion Our findings indicate that the condensin I complex is particularly important within rapidly amplifying progenitor cell populations to ensure faithful chromosome segregation. In contrast, differentiation of postmitotic retinal cells is not impaired upon polyploidization.

  4. Dysfunctional telomeres in human BRCA2 mutated breast tumors and cell lines

    Energy Technology Data Exchange (ETDEWEB)

    Bodvarsdottir, Sigridur K., E-mail: skb@hi.is [Cancer Research Laboratory, BioMedical Centre, Faculty of Medicine, University of Iceland, Vatnsmyrarvegi 16, 101 Reykjavik (Iceland); Steinarsdottir, Margret [Chromosome Laboratory, Department of Genetics and Molecular Medicine, Landspitali University Hospital, Reykjavik (Iceland); Bjarnason, Hordur; Eyfjord, Jorunn E. [Cancer Research Laboratory, BioMedical Centre, Faculty of Medicine, University of Iceland, Vatnsmyrarvegi 16, 101 Reykjavik (Iceland)

    2012-01-03

    In the present study the possible involvement of telomeres in chromosomal instability of breast tumors and cell lines from BRCA2 mutation carriers was examined. Breast tumors from BRCA2 mutation carriers showed significantly higher frequency of chromosome end-to-end fusions (CEFs) than tumors from non-carriers despite normal telomere DNA content. Frequent CEFs were also found in four different BRCA2 heterozygous breast epithelial cell lines, occasionally with telomere signal at the fusion point, indicating telomere capping defects. Extrachromosomal telomeric repeat (ECTR) DNA was frequently found scattered around metaphase chromosomes and interstitial telomere sequences (ITSs) were also common. Telomere sister chromatid exchanges (T-SCEs), characteristic of cells using alternative lengthening of telomeres (ALT), were frequently detected in all heterozygous BRCA2 cell lines as well as the two ALT positive cell lines tested. Even though T-SCE frequency was similar in BRCA2 heterozygous and ALT positive cell lines they differed in single telomere signal loss and ITSs. Chromatid type alterations were more prominent in the BRCA2 heterozygous cell lines that may have propensity for telomere based chromosome healing. Telomere dysfunction-induced foci (TIFs) formation, identified by co-localization of telomeres and {gamma}-H2AX, supported telomere associated DNA damage response in BRCA2 heterozygous cell lines. TIFs were found in interphase nuclei, at chromosome ends, ITSs and ECTR DNA. In conclusion, our results suggest that BRCA2 has an important role in telomere stabilization by repressing CEFs through telomere capping and the prevention of telomere loss by replication stabilization.

  5. Application of the Alkaline Comet Assay and the Analysis of Structural Chromosome Aberrations in Assessment of Genetic Damage After Accidental Exposure to Ionising Radiation

    International Nuclear Information System (INIS)

    Full text: Living with the effects of low-level ionising radiation is one of the normal hazards of life. However, the effects of lower doses may not show up for years after exposure and are due to various changes in DNA molecules and chromosomes. Radiation-induced mutations seem to be brought about by the deletion of small pieces of chromosomes during the process of chromosome breakage and repair. Since chromosome damage is most likely to happen in dividing cells, ionising radiation usually cause cancer in those parts of the body where cells are actively dividing. Ionising radiation kills rapidly dividing cells, blood lymphocytes among them. People are exposed to high doses of ionising radiation when radiation accidents occur. The cytogenetical consequences of accidental exposure to gamma-radiation (radiation dose 221 mSv) were investigated by using alkaline Comet assay and the analysis of structural chromosomal aberrations (CA). Blood samples were repeatedly collected during one-year period after the accident. By using the Comet assay immediately after accidental exposure a high level of DNA damage was recorded. Although this level was decreasing over a one-year period, it was still elevated compared to normal values of DNA damage for unexposed persons. Immediately after the accident prevalence of CA (dicentrics, acentrics) over chromatid aberrations was recorded. However, one year afterwards only a few chromatid breaks were recorded. Our results confirmed usefulness of the alkaline Comet assay as a simple and sensitive technique for the biomonitoring of DNA damages, especially in the cases of accidental exposure to ionising radiation. (author)

  6. Influence of GSTM1, GSTT1, GSTP1, NAT1, NAT2, EPHX1, MTR and MTHFR polymorphism on chromosomal aberration frequencies in human lymphocytes.

    Science.gov (United States)

    Skjelbred, Camilla Furu; Svendsen, Marit; Haugan, Vera; Eek, Anette Kildal; Clausen, Kjell Oskar; Kure, Elin H; Tuimala, Jarno T; Svendsen, Martin Veel; Norppa, Hannu; Hansteen, Inger-Lise

    2011-03-01

    We have studied the influence of genetic polymorphisms in the xenobiotic-metabolizing genes GSTM1, GSTP1, GSTT1, EPHX1, NAT1 and NAT2 and the folate-metabolizing genes MTR and MTHFR on the frequencies of cells with chromosomal aberrations (CAs) in peripheral lymphocytes of Norwegian men. Log-linear Poisson regression models were applied on 357 subjects of whom data on all the polymorphisms examined were available. Total CAs and chromosome-type aberrations (CSAs) were significantly increased by higher age alone, whereas chromatid-type aberrations (CTAs) were elevated by the GSTT1-null genotype and MTHFR codon 222 variant allele and chromatid gaps (CTGs) by EPHX1 high activity genotype and occupational exposure. Stratification by smoking and age (<40 and ≥40 years) showed that the effect of the GSTT1 null and EPHX1 high activity genotypes only concerned (older) smokers, in agreement with the roles of the respective enzymes in detoxification and metabolic activation. The MTHFR codon 222 variant allele was associated with high CTGs in smokers, the MTR codon 919 variant allele with high CTAs in older smokers and the NAT2 fast acetylator genotype with high CTGs in older subjects. Among younger nonsmokers, however, carriers of the MTHFR codon 222 and MTR codon 919 variant alleles showed a decrease in the level of CTGs and total CAs, respectively. In conclusion, polymorphisms of GSTT1, EPHX1, MTHFR, MTR and NAT2 differentially affect the frequency of CTAs, CSAs and CTGs, showing interaction with smoking and age. It appears that CA subtypes rather than total CAs should be considered in this type of studies.

  7. Treatment of HeLa cells with Giloe (Tinospora cordifolia meirs) increases the radiosensitivity by increasing DNA damage

    International Nuclear Information System (INIS)

    Radiotherapy is an important treatment modality and screening of phytoceuticals may enhance the clinical outcome of radiotherapy, therefore radiosensitizing activity of various guduchi (Tinospora cordifolia) extracts was studied in HeLa cells. Chromosomal aberrations were scored in HeLa cells treated with 10 μg/ml of aqueous, methanol, or methylene chloride guduchi extracts or doxorubicin before exposure to 0, 0.5, 1, 2 or 3 Gy of γ-radiation at 12, 24, 36 or 48 h post-irradiation. Irradiation of HeLa cells caused a dose dependent rise in the chromatid breaks, chromosome breaks, dicentric, centric rings, acentric fragments and total aberrations at all post-irradiation times and the dose response was linear quadratic for all types of aberrations scored. Chromatid breaks increased up to 12 h post-irradiation and declined steadily up to 48 h post-irradiation, whereas chromosome breaks, dicentric, acentric fragments and total aberrations elevated up to 24 h post-irradiation and declined thereafter. However, centric rings continued to rise steadily up to 48 h post-irradiation. Treatment of HeLa cells with aqueous, methanol or methylene chloride guduchi extract or doxorubicin before irradiation significantly enhanced various types of chromosomal aberrations and a maximum rise in the chromosome aberrations was observed in the HeLa cells treated with methylene chloride extract before irradiation when compared to other groups. Various guduchi extracts enhanced the effect of radiation in HeLa cells by increasing the molecular damage to cellular genome and their effect was similar to or even greater than doxorubicin (positive control) pretreatment, depending on the type of guduchi extract used. (author)

  8. Adaptive Response to ionizing Radiation Induced by Low Doses of Gamma Rays in Human Lymphoblastoid Cell Lines

    International Nuclear Information System (INIS)

    When cells are exposed to low doses of a mutagenic or clastogenic agents, they often become less sensitive to the effects of a higher does administered subsequently. Such adaptive responses were first described in Escherichia coli and mammalian cells to low doses of an alkylating agent. Since most of the studies have been carried out with human lymphocytes, it is urgently necessary to study this effect in different cellular systems. Its relation with inherent cellular radiosensitivity and underlying mechanism also remain to be answered. In this study, adaptive response by 1 cGy of gamma rays was investigated in three human lymphoblastoid cell lines which were derived from ataxia telangiectasia homozygote, ataxia telangiectasia heterozygote, and normal individual. Experiments were carried out by delivering 1 cGy followed by 50 cGy of gamma radiation and chromatid breaks were scored as an endpoint. The results indicate that prior exposure to 1 cGy of gamma rays reduces the number of chromatid breaks induced by subsequent higher does (50 cGy). The expression of this adaptive response was similar among three cell lines despite of their different radiosensitivity. When 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, was added after 50 cGy, adaptive responses were abolished in all the tested cell lines. Therefore it is suggested that the adaptive response can be observed in human lymphoblastoid cell lines. Which was first documented through this study. The expression of adaptive response was similar among the cell lines regardless of their radiosensitivity. The elimination of the adaptive response by 3-aminobenzamide is consistent with the proposal that this adaptive response is the result of the induction of a certain chromosomal repair mechanism

  9. Epigenetic Histone Marks of Extended Meta-Polycentric Centromeres of Lathyrus and Pisum Chromosomes.

    Science.gov (United States)

    Neumann, Pavel; Schubert, Veit; Fuková, Iva; Manning, Jasper E; Houben, Andreas; Macas, Jiří

    2016-01-01

    Species of the legume genera Lathyrus and Pisum possess chromosomes that exhibit a unique structure of their centromeric regions, which is clearly apparent during metaphase by the formation of extended primary constrictions which span up to a third of the length of the chromosome. In addition, these species express two different variants of the CenH3 protein which are co-localized in multiple domains along the poleward surface of the primary constrictions. Here, we show that the constrictions represent a distinct type of chromatin differing from the chromosome arms. In metaphase, histone phosphorylation patterns including H3S10ph, H3S28ph, and H3T3ph were observed along the entire constriction, in a way similar to holocentric chromosomes. On the other hand, distribution of phosphorylated H2AT120 was different from that previously reported from either, holocentric and monocentric chromosomes, occurring at chromatin surrounding but not overlapping CenH3 domains. Since some of these phosphorylations play a role in chromatid cohesion, it can be assumed that they facilitate correct chromosome segregation by ensuring that multiple separate CenH3 domains present on the same chromatid are oriented toward the same pole. The constrictions also displayed distinct patterns of histone methylation marks, being enriched in H3K9me2 and depleted in H3K4me3 and H3K27me2 compared to the chromosome arms. Super-resolution fluorescence microscopy revealed that although both CenH3 protein variants are present in all CenH3 domains detected on metaphase chromosomes, they are only partially co-localized while there are chromatin subdomains which are mostly made of only one CenH3 variant. Taken together, these data revealed specific features of extended primary constrictions of Lathyrus and Pisum and support the idea that they may represent an intermediate stage between monocentric and holocentric chromosomes. PMID:26973677

  10. Epigenetic histone marks of extended meta-polycentric centromeres of Lathyrus and Pisum chromosomes

    Directory of Open Access Journals (Sweden)

    Pavel eNeumann

    2016-03-01

    Full Text Available Species of the legume genera Lathyrus and Pisum possess chromosomes that exhibit a unique structure of their centromeric regions, which is clearly apparent during metaphase by the formation of extended primary constrictions which span up to a third of the length of the chromosome. In addition, these species express two different variants of the CenH3 protein which are co-localized in multiple domains along the poleward surface of the primary constrictions. Here we show that the constrictions represent a distinct type of chromatin differing from the chromosome arms. In metaphase, histone phosphorylation patterns including H3S10ph, H3S28ph and H3T3ph were observed along the entire constriction, in a way similar to holocentric chromosomes. On the other hand, distribution of phosphorylated H2AT120 was different from that previously reported from either, holocentric and monocentric chromosomes, occurring at chromatin surrounding but not overlapping CenH3 domains. Since some of these phosphorylations play a role in chromatid cohesion, it can be assumed that they facilitate correct chromosome segregation by ensuring that multiple separate CenH3 domains present on the same chromatid are oriented towards the same pole. The constrictions also displayed distinct patterns of histone methylation marks, being enriched in H3K9me2 and depleted in H3K4me3 and H3K27me2 compared to the chromosome arms. High resolution fluorescence microscopy revealed that although both CenH3 protein variants are present in all CenH3 domains detected on metaphase chromosomes, they are only partially co-localized while there are chromatin subdomains which are mostly made of only one CenH3 variant. Taken together, these data revealed specific features of extended primary constrictions of Lathyrus and Pisum and support the idea that they may represent an intermediate stage between monocentric and holocentric chromosomes.

  11. Pyrimidine Pool Disequilibrium Induced by a Cytidine Deaminase Deficiency Inhibits PARP-1 Activity, Leading to the Under Replication of DNA.

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    Simon Gemble

    2015-07-01

    Full Text Available Genome stability is jeopardized by imbalances of the dNTP pool; such imbalances affect the rate of fork progression. For example, cytidine deaminase (CDA deficiency leads to an excess of dCTP, slowing the replication fork. We describe here a novel mechanism by which pyrimidine pool disequilibrium compromises the completion of replication and chromosome segregation: the intracellular accumulation of dCTP inhibits PARP-1 activity. CDA deficiency results in incomplete DNA replication when cells enter mitosis, leading to the formation of ultrafine anaphase bridges between sister-chromatids at "difficult-to-replicate" sites such as centromeres and fragile sites. Using molecular combing, electron microscopy and a sensitive assay involving cell imaging to quantify steady-state PAR levels, we found that DNA replication was unsuccessful due to the partial inhibition of basal PARP-1 activity, rather than slower fork speed. The stimulation of PARP-1 activity in CDA-deficient cells restores replication and, thus, chromosome segregation. Moreover, increasing intracellular dCTP levels generates under-replication-induced sister-chromatid bridges as efficiently as PARP-1 knockdown. These results have direct implications for Bloom syndrome (BS, a rare genetic disease combining susceptibility to cancer and genomic instability. BS results from mutation of the BLM gene, encoding BLM, a RecQ 3'-5' DNA helicase, a deficiency of which leads to CDA downregulation. BS cells thus have a CDA defect, resulting in a high frequency of ultrafine anaphase bridges due entirely to dCTP-dependent PARP-1 inhibition and independent of BLM status. Our study describes previously unknown pathological consequences of the distortion of dNTP pools and reveals an unexpected role for PARP-1 in preventing DNA under-replication and chromosome segregation defects.

  12. DNA repair deficiency as a susceptibility marker for spontaneous lymphoma in golden retriever dogs: a case-control study.

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    Douglas H Thamm

    Full Text Available There is accumulating evidence that an individual's inability to accurately repair DNA damage in a timely fashion may in part dictate a predisposition to cancer. Dogs spontaneously develop lymphoproliferative diseases such as lymphoma, with the golden retriever (GR breed being at especially high risk. Mechanisms underlying such breed susceptibility are largely unknown; however, studies of heritable cancer predisposition in dogs may be much more straightforward than similar studies in humans, owing to a high degree of inbreeding and more limited genetic heterogeneity. Here, we conducted a pilot study with 21 GR with lymphoma, 20 age-matched healthy GR and 20 age-matched healthy mixed-breed dogs (MBD to evaluate DNA repair capability following exposure to either ionizing radiation (IR or the chemical mutagen bleomycin. Inter-individual variation in DNA repair capacity was evaluated in stimulated canine lymphoctyes exposed in vitro utilizing the G2 chromosomal radiosensitivity assay to quantify clastogen-induced chromatid-type aberrations (gaps and breaks. Golden retrievers with lymphoma demonstrated elevated sensitivity to induction of chromosome damage following either challenge compared to either healthy GR or MBD at multiple doses and time points. Using the 75(th percentile of chromatid breaks per 1,000 chromosomes in the MBD population at 4 hours post 1.0 Gy IR exposure as a benchmark to compare cases and controls, GR with lymphoma were more likely than healthy GR to be classified as "sensitive" (odds ratio = 21.2, 95% confidence interval 2.3-195.8. Furthermore, our preliminary findings imply individual (rather than breed susceptibility, and suggest that deficiencies in heritable factors related to DNA repair capabilities may be involved in the development of canine lymphoma. These studies set the stage for larger confirmatory studies, as well as candidate-based approaches to probe specific genetic susceptibility factors.

  13. PARP Inhibitors in Clinical Use Induce Genomic Instability in Normal Human Cells

    Science.gov (United States)

    Ito, Shuhei; Murphy, Conleth G.; Doubrovina, Ekaterina; Jasin, Maria; Moynahan, Mary Ellen

    2016-01-01

    Poly(ADP-ribose) polymerases (PARPs) are the first proteins involved in cellular DNA repair pathways to be targeted by specific inhibitors for clinical benefit. Tumors harboring genetic defects in homologous recombination (HR), a DNA double-strand break (DSB) repair pathway, are hypersensitive to PARP inhibitors (PARPi). Early phase clinical trials with PARPi have been promising in patients with advanced BRCA1 or BRCA2-associated breast, ovary and prostate cancer and have led to limited approval for treatment of BRCA-deficient ovary cancer. Unlike HR-defective cells, HR-proficient cells manifest very low cytotoxicity when exposed to PARPi, although they mount a DNA damage response. However, the genotoxic effects on normal human cells when agents including PARPi disturb proficient cellular repair processes have not been substantially investigated. We quantified cytogenetic alterations of human cells, including primary lymphoid cells and non-tumorigenic and tumorigenic epithelial cell lines, exposed to PARPi at clinically relevant doses by both sister chromatid exchange (SCE) assays and chromosome spreading. As expected, both olaparib and veliparib effectively inhibited poly-ADP-ribosylation (PAR), and caused marked hypersensitivity in HR-deficient cells. Significant dose-dependent increases in SCEs were observed in normal and non-tumorigenic cells with minimal residual PAR activity. Clinically relevant doses of the FDA-approved olaparib led to a marked increase of SCEs (5-10-fold) and chromatid aberrations (2-6-fold). Furthermore, olaparib potentiated SCE induction by cisplatin in normal human cells. Our data have important implications for therapies with regard to sustained genotoxicity to normal cells. Genomic instability arising from PARPi warrants consideration, especially if these agents will be used in people with early stage cancers, in prevention strategies or for non-oncologic indications. PMID:27428646

  14. Assessment of adaptability of zebu cattle (Bos indicus) breeds in two different climatic conditions: using cytogenetic techniques on genome integrity.

    Science.gov (United States)

    Kumar, Anil; Waiz, Syma Ashraf; Sridhar Goud, T; Tonk, R K; Grewal, Anita; Singh, S V; Yadav, B R; Upadhyay, R C

    2016-06-01

    The aim of this study was to evaluate the genome integrity so as to assess the adaptability of three breeds of indigenous cattle reared under arid and semi-arid regions of Rajasthan (Bikaner) and Haryana (Karnal) India. The cattle were of homogenous group (same age and sex) of indigenous breeds viz. Sahiwal, Tharparkar and Kankrej. A total of 100 animals were selected for this study from both climatic conditions. The sister chromatid exchanges (SCE's), chromosomal gaps and chromatid breaks were observed in metaphase plates of chromosome preparations obtained from in vitro culture of peripheral blood lymphocytes. The mean number of breaks and gaps in Sahiwal and Tharparkar of semi-arid zone were 8.56 ± 3.16, 6.4 ± 3.39 and 8.72 ± 2.04, 3.52 ± 6.29, respectively. Similarly, the mean number of breaks and gaps in Tharparkar and Kankrej cattle of arid zone were 5.26 ± 1.76, 2.74 ± 1.76 and 5.24 ± 1.84, 2.5 ± 1.26, respectively. The frequency of SCEs in chromosomes was found significantly higher (P P P > 0.05) was observed in the same zone. The analysis of frequency of CAs and SCEs revealed significant effects of environmental conditions on the genome integrity of animals, thereby indicating an association with their adaptability. PMID:26476524

  15. PARP Inhibitors in Clinical Use Induce Genomic Instability in Normal Human Cells.

    Directory of Open Access Journals (Sweden)

    Shuhei Ito

    Full Text Available Poly(ADP-ribose polymerases (PARPs are the first proteins involved in cellular DNA repair pathways to be targeted by specific inhibitors for clinical benefit. Tumors harboring genetic defects in homologous recombination (HR, a DNA double-strand break (DSB repair pathway, are hypersensitive to PARP inhibitors (PARPi. Early phase clinical trials with PARPi have been promising in patients with advanced BRCA1 or BRCA2-associated breast, ovary and prostate cancer and have led to limited approval for treatment of BRCA-deficient ovary cancer. Unlike HR-defective cells, HR-proficient cells manifest very low cytotoxicity when exposed to PARPi, although they mount a DNA damage response. However, the genotoxic effects on normal human cells when agents including PARPi disturb proficient cellular repair processes have not been substantially investigated. We quantified cytogenetic alterations of human cells, including primary lymphoid cells and non-tumorigenic and tumorigenic epithelial cell lines, exposed to PARPi at clinically relevant doses by both sister chromatid exchange (SCE assays and chromosome spreading. As expected, both olaparib and veliparib effectively inhibited poly-ADP-ribosylation (PAR, and caused marked hypersensitivity in HR-deficient cells. Significant dose-dependent increases in SCEs were observed in normal and non-tumorigenic cells with minimal residual PAR activity. Clinically relevant doses of the FDA-approved olaparib led to a marked increase of SCEs (5-10-fold and chromatid aberrations (2-6-fold. Furthermore, olaparib potentiated SCE induction by cisplatin in normal human cells. Our data have important implications for therapies with regard to sustained genotoxicity to normal cells. Genomic instability arising from PARPi warrants consideration, especially if these agents will be used in people with early stage cancers, in prevention strategies or for non-oncologic indications.

  16. Different radiosensitization effects of the halogenated compounds on the human chromosome in vitro

    International Nuclear Information System (INIS)

    Unscheduled DNA synthesis and chromosome aberrations were compared following X- or UV-irradiation or methyl methanesulfonate treatment in cultures of HeLa S3 or KB cells or human and rabbit lymphocytes. The sensitization by incorporation of the halouridines BUdR and IUdR was also investigated. Unscheduled DNA synthesis occurred in two established cell lines after irradiation with 0 to 10 kR of X-rays. The rate of unscheduled synthesis was dose dependent and differed for the two cell lines. The unscheduled synthesis was not correlated with the modal chromosome number nor with the number of aberrations produced. UV-irradiated rabbit lymphocytes exhibited unscheduled DNA synthesis which saturated after a dose of 250 ergs/mm2. In contrast the incorporation of BUdR or IUdR eliminated this saturation and caused an increasing effect with increasing dose up to 1000 ergs/mm2. The degree of sensitization varied between the two halo-uridines, BUdR being more effective at high doses while IUdR was a more potent sensitizer at low doses. Chromosome aberrations were not directly related to unscheduled DNA synthesis but were sensitized by halo-uridine incorporation. In this case IUdR was more potent than BUdR at all doses studied. Methyl methanesulfonate was an effective producer of chromosome aberration in human lymphocytes of both the chromosome and chromatid type. Prior incorporation of BUdR or IUdR did not increase the total aberration produced but did increase the number of chromosome type aberration at the expense of the chromatid type

  17. Drosophila Nipped-B Mutants Model Cornelia de Lange Syndrome in Growth and Behavior.

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    Yaning Wu

    2015-11-01

    Full Text Available Individuals with Cornelia de Lange Syndrome (CdLS display diverse developmental deficits, including slow growth, multiple limb and organ abnormalities, and intellectual disabilities. Severely-affected individuals most often have dominant loss-of-function mutations in the Nipped-B-Like (NIPBL gene, and milder cases often have missense or in-frame deletion mutations in genes encoding subunits of the cohesin complex. Cohesin mediates sister chromatid cohesion to facilitate accurate chromosome segregation, and NIPBL is required for cohesin to bind to chromosomes. Individuals with CdLS, however, do not display overt cohesion or segregation defects. Rather, studies in human cells and model organisms indicate that modest decreases in NIPBL and cohesin activity alter the transcription of many genes that regulate growth and development. Sister chromatid cohesion factors, including the Nipped-B ortholog of NIPBL, are also critical for gene expression and development in Drosophila melanogaster. Here we describe how a modest reduction in Nipped-B activity alters growth and neurological function in Drosophila. These studies reveal that Nipped-B heterozygous mutant Drosophila show reduced growth, learning, and memory, and altered circadian rhythms. Importantly, the growth deficits are not caused by changes in systemic growth controls, but reductions in cell number and size attributable in part to reduced expression of myc (diminutive and other growth control genes. The learning, memory and circadian deficits are accompanied by morphological abnormalities in brain structure. These studies confirm that Drosophila Nipped-B mutants provide a useful model for understanding CdLS, and provide new insights into the origins of birth defects.

  18. Analysis of chromosomal aberrations, micronuclei and hematological disorders among workers of wireless communication instruments and cell phone (Mobile) users

    International Nuclear Information System (INIS)

    This study was carried out to investigate the hazardous effect of electromagnetic radiation (EMR) such as chromosomal aberration, disturbed micronucleus formation and hematological disorders that may detected among workers of wireless communication instruments and mobile phone users. Seven individuals ( 3 males and 4 females) of a central workers in the microwave unit of the wireless station and 7 users of Mobil phone (4 males and 3 females ) were volunteered to give blood samples. Chromosomes and micronucleus were prepared for cytogenetic analysis as well as blood film for differential count. The results obtained in the microwave group indicated that, the total summation of all types of aberrations (chromosomes and chromatid aberrations) had a frequency of 6. 14% for the exposed group, whereas, the frequency in the control group amounted to 1.57%. In Mobil phone users, the total summation of all types of aberrations(chromosome and chromatid aberrations) had a frequency of 4.43% for the exposed group and 1.71% for the control group. The incidence of the total number of micronuclei in the exposed microwave group was increased 4.3 folds as compared with those of the control group The incidence of the total number of micronuclei in the exposed mobile phone group was increased 2 fold as compared with those in the control group. On the other hand, normal ranges of total white blood cells counts were determined for mobile phone users but abnormalities in the differential counts of the different types of the white blood cells such as neutropenia, eosinophilia and lymphocytosis were observed in the individuals number 1,2,3,7 in microwave group

  19. Chromosome Aberrations of East Asian Bullfrog (Hoplobatrachus rugulosus around a Gold Mine Area with Arsenic Contamination

    Directory of Open Access Journals (Sweden)

    Atidtaya Suttichaiya

    2016-01-01

    Full Text Available The objectives of this study are to investigate the chromosome aberrations of the East Asian Bullfrog (Hoplobatrachus rugulosus in the gold mine area compared to an unaffected area. Three H. rugulosus were collected, and chromosome aberrations were studied using bone marrow. The level of arsenic was measured in water, sediment and H. rugulosus samples. The average concentrations of arsenic in the water and sediment samples from the gold mine and unaffected areas were 0.03 ± 0.003 mg/l and not detected in water as well as 351.59 ± 5.73 and 1.37 ± 1.07 mg/kg in sediment, respectively. The gold mine values were higher than the permissible limit of the water and soil quality standards, but the arsenic concentrations in the samples from the unaffected area were within prescribed limit. The average concentrations of arsenic in H. rugulosus samples from the gold mine and unaffected areas were 0.39 ± 0.30 and 0.07 ± 0.01 mg/kg, respectively, which were both lower than the standard of arsenic contamination in food. The diploid chromosome number of H. rugulosus in both areas was 2n=26, and the percentage of chromosome breakages of H. rugulosus in the gold mine area were higher than the unaffected area. There were eight types of chromosome aberrations, including a single chromatid gap, isochromatid gap, single chromatid break, isochromatid break, centric fragmentation, deletion, fragmentation and translocation. The most common chromosome aberration in the samples from the affected area was deletion. The difference in the percentage of chromosome breakages in H. rugulosus from both areas was statistically significant (p<0.05.

  20. When the genome plays dice: circumvention of the spindle assembly checkpoint and near-random chromosome segregation in multipolar cancer cell mitoses.

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    David Gisselsson

    Full Text Available BACKGROUND: Normal cell division is coordinated by a bipolar mitotic spindle, ensuring symmetrical segregation of chromosomes. Cancer cells, however, occasionally divide into three or more directions. Such multipolar mitoses have been proposed to generate genetic diversity and thereby contribute to clonal evolution. However, this notion has been little validated experimentally. PRINCIPAL FINDINGS: Chromosome segregation and DNA content in daughter cells from multipolar mitoses were assessed by multiphoton cross sectioning and fluorescence in situ hybridization in cancer cells and non-neoplastic transformed cells. The DNA distribution resulting from multipolar cell division was found to be highly variable, with frequent nullisomies in the daughter cells. Time-lapse imaging of H2B/GFP-labelled multipolar mitoses revealed that the time from the initiation of metaphase to the beginning of anaphase was prolonged and that the metaphase plates often switched polarity several times before metaphase-anaphase transition. The multipolar metaphase-anaphase transition was accompanied by a normal reduction of cellular cyclin B levels, but typically occurred before completion of the normal separase activity cycle. Centromeric AURKB and MAD2 foci were observed frequently to remain on the centromeres of multipolar ana-telophase chromosomes, indicating that multipolar mitoses were able to circumvent the spindle assembly checkpoint with some sister chromatids remaining unseparated after anaphase. Accordingly, scoring the distribution of individual chromosomes in multipolar daughter nuclei revealed a high frequency of nondisjunction events, resulting in a near-binomial allotment of sister chromatids to the daughter cells. CONCLUSION: The capability of multipolar mitoses to circumvent the spindle assembly checkpoint system typically results in a near-random distribution of chromosomes to daughter cells. Spindle multipolarity could thus be a highly efficient

  1. Meiosis genes in Daphnia pulex and the role of parthenogenesis in genome evolution

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    Eads Brian D

    2009-04-01

    Full Text Available Abstract Background Thousands of parthenogenetic animal species have been described and cytogenetic manifestations of this reproductive mode are well known. However, little is understood about the molecular determinants of parthenogenesis. The Daphnia pulex genome must contain the molecular machinery for different reproductive modes: sexual (both male and female meiosis and parthenogenetic (which is either cyclical or obligate. This feature makes D. pulex an ideal model to investigate the genetic basis of parthenogenesis and its consequences for gene and genome evolution. Here we describe the inventory of meiotic genes and their expression patterns during meiotic and parthenogenetic reproduction to help address whether parthenogenesis uses existing meiotic and mitotic machinery, or whether novel processes may be involved. Results We report an inventory of 130 homologs representing over 40 genes encoding proteins with diverse roles in meiotic processes in the genome of D. pulex. Many genes involved in cell cycle regulation and sister chromatid cohesion are characterized by expansions in copy number. In contrast, most genes involved in DNA replication and homologous recombination are present as single copies. Notably, RECQ2 (which suppresses homologous recombination is present in multiple copies while DMC1 is the only gene in our inventory that is absent in the Daphnia genome. Expression patterns for 44 gene copies were similar during meiosis versus parthenogenesis, although several genes displayed marked differences in expression level in germline and somatic tissues. Conclusion We propose that expansions in meiotic gene families in D. pulex may be associated with parthenogenesis. Taking into account our findings, we provide a mechanistic model of parthenogenesis, highlighting steps that must differ from meiosis including sister chromatid cohesion and kinetochore attachment.

  2. Intact Cohesion, Anaphase, and Chromosome Segregation in Human Cells Harboring Tumor-Derived Mutations in STAG2.

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    Jung-Sik Kim

    2016-02-01

    Full Text Available Somatic mutations of the cohesin complex subunit STAG2 are present in diverse tumor types. We and others have shown that STAG2 inactivation can lead to loss of sister chromatid cohesion and alterations in chromosome copy number in experimental systems. However, studies of naturally occurring human tumors have demonstrated little, if any, correlation between STAG2 mutational status and aneuploidy, and have further shown that STAG2-deficient tumors are often euploid. In an effort to provide insight into these discrepancies, here we analyze the effect of tumor-derived STAG2 mutations on the protein composition of cohesin and the expected mitotic phenotypes of STAG2 mutation. We find that many mutant STAG2 proteins retain their ability to interact with cohesin; however, the presence of mutant STAG2 resulted in a reduction in the ability of regulatory subunits WAPL, PDS5A, and PDS5B to interact with the core cohesin ring. Using AAV-mediated gene targeting, we then introduced nine tumor-derived mutations into the endogenous allele of STAG2 in cultured human cells. While all nonsense mutations led to defects in sister chromatid cohesion and a subset induced anaphase defects, missense mutations behaved like wild-type in these assays. Furthermore, only one of nine tumor-derived mutations tested induced overt alterations in chromosome counts. These data indicate that not all tumor-derived STAG2 mutations confer defects in cohesion, chromosome segregation, and ploidy, suggesting that there are likely to be other functional effects of STAG2 inactivation in human cancer cells that are relevant to cancer pathogenesis.

  3. 脉冲电磁场对家猪淋巴细胞的细胞遗传学效应%Cytogenetic Effects of Pulsing Electromagnetic Field on Domestic Pig Lymphocytes in Vitro

    Institute of Scientific and Technical Information of China (English)

    邹方东; 徐柳; 王子淑; 王喜忠

    2001-01-01

    以家猪外周血淋巴细胞为材料,研究了脉冲电磁场(pulsing electromagnetic fields,简称PEMFs)对细胞的遗传学效应。实验发现,100和200 kHz的PEMFs对家猪的淋巴细胞照射培养12、24、48 h后,染色体畸变(包括非整倍体、染色体断裂等)频率明显高于对照组(P<0.05)。其中,56%的染色体或染色单体断裂和42%的间隙发生在家猪常见染色体脆性位点部位。同时,经100 kHz和200 kHz的PEMFs照射48 h后,淋巴细胞姐妹染色单体交换(SCE)频率也明显高于对照组(P<0.05)。实验结果表明,PEMFs能诱导DNA损伤和染色体畸变。%The effects of pulsing electromagnetic fields (PEMFs) on cells are very important subjects in the field of bioelectromagnetics. In this experiment,the cytogenetic effects of PEMF on domestic pig lymphocytes were tested in vitro. Pig lymphocytes in RPMI 1640 medium were exposed to PEMFs of 100 kHz and 200 kHz for 12,24 and 48 hours. Chromosomal aberrations (aneuploidy,breaks,gaps,et al.) were significantly increased in exposed cultures,and of these aberrations,56% chromosomal or chromatid breaks and 42% gaps induced by PEMFs were the points of pig chromosomal fragile sites.The baseline frequency of sister-chromatid exchange (SCE) increased after exposing lymphocytes continuously to PEMFs of 100 kHz and 200 kHz for 48 hours. These results suggested that the exposure to PEMFs might induce a type of DNA lesion and chromosomal aberrations.

  4. Role of Artemis in DSB repair and guarding chromosomal stability following exposure to ionizing radiation at different stages of cell cycle

    Energy Technology Data Exchange (ETDEWEB)

    Darroudi, Firouz [Department of Toxicogenetics, Leiden University Medical Centre, Einthovenweg 20, 2300RC Leiden (Netherlands)]. E-mail: F.Darroudi@LUMC.NL; Wiegant, Wouter [Department of Toxicogenetics, Leiden University Medical Centre, Einthovenweg 20, 2300RC Leiden (Netherlands); Meijers, Matty [Department of Toxicogenetics, Leiden University Medical Centre, Einthovenweg 20, 2300RC Leiden (Netherlands); Friedl, Anna A. [Radiobiological Institute, University of Munich, Munich (Germany); Institute of Radiobiology, GSF National Research Center for Environment and Health, Neuherberg (Germany); Burg, Mirjam van der [Department of Immunology, Erasmus Medical Centre, Rotterdam (Netherlands); Fomina, Janna [Department of Toxicogenetics, Leiden University Medical Centre, Einthovenweg 20, 2300RC Leiden (Netherlands); Dongen, Jacques J.M. van [Department of Immunology, Erasmus Medical Centre, Rotterdam (Netherlands); Gent, Dik C. van [Department of Cell Biology and Genetics, Erasmus Medical Centre, Rotterdam (Netherlands); Zdzienicka, Malgorzata Z. [Department of Toxicogenetics, Leiden University Medical Centre, Einthovenweg 20, 2300RC Leiden (Netherlands); Department of Molecular Cell Genetics, Collegium Medicum, N. Corpernicus University, Bydgoszcz (Poland)

    2007-02-03

    We analyzed the phenotype of cells derived from SCID patients with different mutations in the Artemis gene. Using clonogenic survival assay an increased sensitivity was found to X-rays (2-3-fold) and bleomycin (2-fold), as well as to etoposide, camptothecin and methylmethane sulphonate (up to 1.5-fold). In contrast, we did not find increased sensitivity to cross-linking agents mitomycin C and cis-platinum. The kinetics of DSB repair assessed by pulsed-field gel electrophoresis and {gamma}H2AX foci formation after ionizing irradiation, indicate that 15-20% of DSB are not repaired in Artemis-deficient cells. In order to get a better understanding of the repair defect in Artemis-deficient cells, we studied chromosomal damage at different stages of the cell cycle. In contrast to AT cells, Artemis-deficient cells appear to have a normal G{sub 1}/S-block that resulted in a similar frequency of dicentrics and translocations, however, frequency of acentrics fragments was found to be 2-4-fold higher compared to normal fibroblasts. Irradiation in G{sub 2} resulted in a higher frequency of chromatid-type aberrations (1.5-3-fold) than in normal cells, indicating that a fraction of DSB requires Artemis for proper repair. Our data are consistent with a function of Artemis protein in processing of a subset of complex DSB, without G{sub 1} cell cycle checkpoint defects. This type of DSB can be induced in high proportion and persist through S-phase and in part might be responsible for the formation of chromatid-type exchanges in G{sub 1}-irradiated Artemis-deficient cells. Among different human radiosensitive fibroblasts studied for endogenous (in untreated samples) as well as X-ray-induced DNA damage, the ranking order on the basis of higher incidence of spontaneously occurring chromosomal alterations and induced ones was: ligase 4 {>=} AT > Artemis. This observation implicates that in human fibroblasts following exposure to ionizing radiation a lower risk might be created when

  5. The functional polymorphism of NBS1 p.Glu185Gln is associated with an increased risk of lung cancer in Chinese populations: Case–control and a meta-analysis

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Wenxiang; Qiu, Fuman; Zhang, Lisha [The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Collaborative Innovation Center for Environmental Toxicity, Guangzhou Medical University, Guangzhou 510182 (China); Deng, Jieqiong [Soochow University Laboratory of Cancer Molecular Genetics, Collaborative Innovation Center for Environmental Toxicity, Medical College of Soochow University, Suzhou 215123 (China); Zhang, Haibo [Department of Cardio-thoracic Surgery, The First Affiliated Hospital of Guangdong Pharmaceutical University, Guangzhou 510080 (China); Yang, Lei [The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Collaborative Innovation Center for Environmental Toxicity, Guangzhou Medical University, Guangzhou 510182 (China); Zhou, Yifeng [Soochow University Laboratory of Cancer Molecular Genetics, Collaborative Innovation Center for Environmental Toxicity, Medical College of Soochow University, Suzhou 215123 (China); Lu, Jiachun, E-mail: jcLu@gzhmu.edu.cn [The State Key Lab of Respiratory Disease, The Institute for Chemical Carcinogenesis, Collaborative Innovation Center for Environmental Toxicity, Guangzhou Medical University, Guangzhou 510182 (China)

    2014-12-15

    Highlights: • NBS1 rs1805794G>C polymorphism conferred an adverse role on lung cancer risk in a two centers case–control study. • Rs1805794C variants had more chromatid breaks and higher DNA damage induced by X-ray radiation. • Meta analysis result confirmed the association between the variant rs1805794G>C and lung cancer risk. - Abstract: NBS1 plays pivotal roles in maintaining genomic stability and cancer development. The exon variant rs1805794G>C (p.Glu185Gln) of NBS1 has been frequently studied in several association studies. However, the results were conflicting. Also, the function of this variant has never been well studied. In the current study, we performed a two centers case–control study and function assays to investigate the effect of the variant rs1805794G>C on lung cancer risk in Chinese, and a meta-analysis to summarize the data on the association between rs1805794G>C and cancer risk. We found that compared with the rs1805794GG genotype, the C genotypes (CG/CC) conferred a significantly increased risk of lung cancer in Chinese (OR = 1.40, 95% CI = 1.21–1.62) and interacted with medical ionizing radiation exposure on increasing cancer risk (P{sub interaction} = 0.015). The lymphocyte cells from the C genotype individuals developed more chromatid breaks than those from the GG genotype carriers after the X-ray radiation (P = 0.036). Moreover, the rs1805794C allele encoding p.185Gln attenuated NBS1's ability to repair DNA damage as the cell lines transfected with NBS1 cDNA expression vector carrying rs1805794C allele had significantly higher DNA breaks than those transfected with NBS1 cDNA expression vector carrying rs1805794G allele (P < 0.05). The meta-analysis further confirmed the association between the variant rs1805794G>C and lung cancer risk, that compared with the GG genotype, the carriers of C genotypes had a 1.30-fold risk of cancer (95% CI = 1.14–1.49, P = 8.49 × 10{sup −5}). These findings suggest that the rs1805794G

  6. Genetic determination of chromosomal radiosensitivities in G0- and G2-phase human lymphocytes

    International Nuclear Information System (INIS)

    Background and purpose: The radiosensitivity of human lymphocytes measured using a G0- or G2-assay has been linked with an individual's risk of developing normal tissue complications following radiotherapy. This study was performed to increase basic knowledge of the genetics of the human radiation response, and chromosomal aberration induction in particular. Materials and methods: The study was carried out with blood samples taken from 15 monozygotic twin pairs. G0-assay was performed for cells irradiated with 6 Gy counting only deletions and G2-assay for cells irradiated with 0.5 Gy scoring only chromatid breaks. Results: The mean number of deletions measured at 6 Gy for all 30 samples using the G0-assay amounted to 2.96 ± 0.37 (means ± SD), which corresponds to a coefficient of variation (CV) of 13%. There is a highly significant intra-pair correlation for this number among twins (r 2 = 0.911) demonstrating that this parameter is mostly determined by genetic factors. According to the mean number of deletions, a theoretical classification based on the definition =MV + SD as sensitive was made, identifying two pairs as sensitive or resistant, respectively, while nine were normal and two pairs are intermediate. For chromatid breaks measured at 0.5 Gy with the G2-assay the mean number was 1.35 ± 0.42 (means ± SD) corresponding to a CV of 31%. There was again a strong intra-pair correlation among twins with r 2 = 0.837 showing that this sensitivity is also determined mostly by genetic factors. There was, however, no inter-assay correlation between the G0- and G2-sensitivity (r 2 = 0.006) demonstrating that these two sensitivities depend on different genetic factors. Conclusion: The chromosomal radiosensitivity of lymphocytes as defined by G0- or G2-assay is largely determined by different genetic factors, which may allow the use of genetic profiling as an indicator of the respective individual radiosensitivity

  7. Monitoring of DNA and cytogenetic damage in lymphocytes from persons with skin cancer diseases

    International Nuclear Information System (INIS)

    There is a lot of interest in the studies that would help to understand whether there is a casual association between cancer and various types of molecular or cytogenetic damage detected in human cells. One major oncogenesis process is activation of proto-oncogenes by point mutations or chromosomal translocation. There are substantial evidence that indicates that the loss of heterozygosity of certain chromosomes is involved in human cancerogenesis. Our study aimed to elicit the possible association between cancer and DNA and cytogenetic abnormalities induced in lymphocytes of people bearing various categories of skin cancer cells. Fresh blood was collected by venipuncture from 25 individuals (including nine prior to cancer treatment). All patients were nonsmoking males, however 42.3 % of them were former smokers. Blood samples were divided into two parts and in the first part of samples cytogenetic studies were performed immediately, while from the second part lymphocytes were isolated and stored at -70oC for further studies in vitro. In the later one a single cell gel electrophoresis assay (SCGE) known as a Comet assay was performed to study individual susceptibility to the induction of DNA damage by UV or radiation and to estimate variability in cellular repair capabilities. An average of 220 per sample of good metaphase spreads in the first mitotic division, and 100 per sample in the second division, were accepted for analysis of cytogenetic damage. Chromosome and chromatid type aberrations were scored in the cells in the first mitosis and expressed as total aberration frequency including gaps and excluding gaps. Sister chromatid exchanges, high frequency cells and proliferative rate index were screened and evaluated in the second mitosis. Each of the patient revealed exceeding in at least one of the cytogenetic biomarkers level from the biomarker's level detected in a reference group. In order to estimate susceptibility of people to environmentally induced

  8. Genetic damage in human cells exposed to non-ionizing radiofrequency fields: a meta-analysis of the data from 88 publications (1990-2011).

    Science.gov (United States)

    Vijayalaxmi; Prihoda, Thomas J

    2012-12-12

    Based on the 'limited' evidence suggesting an association between exposure to radiofrequency fields (RF) emitted from mobile phones and two types of brain cancer, glioma and acoustic neuroma, the International Agency for Research on Cancer has classified RF as 'possibly carcinogenic to humans' in group 2B. In view of this classification and the positive correlation between increased genetic damage and carcinogenesis, a meta-analysis was conducted to determine whether a significant increase in genetic damage in human cells exposed to RF provides a potential mechanism for its carcinogenic potential. The extent of genetic damage in human cells, assessed from various end-points, viz., single-/double-strand breaks in the DNA, incidence of chromosomal aberrations, micronuclei and sister chromatid exchanges, reported in a total of 88 peer-reviewed scientific publications during 1990-2011 was considered in the meta-analysis. Among the several variables in the experimental protocols used, the influence of five specific variables related to RF exposure characteristics was investigated: (i) frequency, (ii) specific absorption rate, (iii) exposure as continuous wave, pulsed wave and occupationally exposed/mobile phone users, (iv) duration of exposure, and (v) different cell types. The data indicated the following. (1) The magnitude of difference between RF-exposed and sham-/un-exposed controls was small with some exceptions. (2) In certain RF exposure conditions there was a statistically significant increase in genotoxicity assessed from some end-points: the effect was observed in studies with small sample size and was largely influenced by publication bias. Studies conducted within the generally recommended RF exposure guidelines showed a smaller effect. (3) The multiple regression analyses and heterogeneity goodness of fit data indicated that factors other than the above five variables as well as the quality of publications have contributed to the overall results. (4) More

  9. Analysis of the meiosis in the F1 hybrids of Longiflorum x Asiatic(LA) of lilies (Lilium) using genomic in situ hybridization

    Institute of Scientific and Technical Information of China (English)

    Shujun Zhou; Munikote S. Ramanna; Richard G.F.Visser; Jaap M. van Tuyl

    2008-01-01

    Longiflorum and Asiatic lilies of the genus Lilium of the family Liliaeeae are two important groups of modern lily eultivars. One of the main trends of lily breeding is to realize introgression between these groups. With cut style pollination and embryo rescue, distant hybrids between the two groups have been obtained. However, the F1hybrids are highly sterile or some of them could produce a small number of 2n gametes, and their BC1 progenies are usually triploids. Dutch lily breeders have selected many cultivars from these BC1 progenies based on their variation. It is presumably suggested that such variation could be caused by intergenomic recombination and abnormal meiosis during gamete formation in F1 hybrids of Longiflorum x Asiatic (LA) hybrids in Lilium. Therefore, the meiotic process of ten F1 LA hybrids was cytologically investigated using genomic in situ hybridization and traditional cytological methods in the present research.The results showed that: at metaphase I, the homoeologous chromosome pairing among different F1hybrids ranged from 2.0 to 11.4 bi-valents formed by homoeologous chromosomes per pollen mother cell (PMC), and very few multivalents, and even very few bivalents were formed by two chromosomes within one genome rather than homoeologous chromosomes in some PMCs; at anaphase I, all biva-lents were disjoined and most univalents were divided. Both the disjoined bivalents (half-bivalents) and the divided univalents (sister chromatids) moved to the opposite poles, and then formed two groups of chromosomes; because the two resulting half-bivalents retained their axes in the cell undisturbed, many crossover types, including single crossovers, three strand double crossovers, four strand double crossovers, four strand triple crossovers, and four strand multiple crossovers between the non-sister chromatids in the tetrads of bivalents,were clearly inferred by analyzing the breakpoints on the disjoined bivalents. The present investigation not only

  10. Genotoxic Damage in vivo, Susceptibility to UVC and X-Rays, and Repair Efficiency in vitro Lymphocytes from Referent and Occupational Exposed to Mercury Vapours Group

    International Nuclear Information System (INIS)

    For years mercury has been considered to be dangerous for human health. It was shown in vitro studies that mercury ions produce various types of DNA damage: single strand breaks as well as alkali labile lesions. The aim of this study was to compare levels of the DNA damage and cytogenetic damage induced in vivo, DNA's susceptibility to radiation, as well as repair capabilities of DNA damage induced in vitro by UV-exposure or X-rays, in lymphocytes from unexposed donors and from persons occupationally exposed to mercury vapours. In order to estimate cytogenetic damage, the analysis of sister chromatid exchange frequency (SCE) was used, while to detect DNA damage alkaline version of the single cell gel electrophoresis (SCGE) was applied. To analyse in vitro susceptibility of cells to genotoxic factors such as UV-C or X-rays, lymphocytes were exposed to 6 J/m2 of UV or irradiated with 2 Gy of X-rays. After exposure the cells were incubated for 2 hours with or without the presence of phytohemagglutinin (agent stimulating cell divisions). In the present study, results do not show any statistically significant differences between the examined groups, either in the levels of DNA damage of untreated lymphocytes or in the sister chromatid exchanges. Neither the levels of DNA damage detected in lymphocytes after UV exposure and 2 h incubation, without or in the presence of a cell- division stimulating agent, nor the repair efficiencies of the DNA damage induced by UV exposure, differed significantly between the unexposed group and that occupationally exposed to mercury vapours. Statistically significant higher levels of DNA damage measured in X-ray-irradiated lymphocytes, without incubation and after 2 hours of incubation, with or without the presence of phytohemagglutinin, were observed in the group exposed to mercury vapours. So, donors exposed to mercury vapours have shown a statistically lower repair efficiency of X-ray-induced DNA damage both in non- stimulated

  11. Influence of Mercury Vapors on Lymphocytes in Vivo and on their Susceptibility to UV-C and X-Rays, and Repair Efficiency in Vitro

    International Nuclear Information System (INIS)

    The aim of the study was to compare the levels of DNA and cytogenetic damage in lymphocytes from donors occupationally exposed to mercury vapors and from matched controls as well as their cellular susceptibility to radiation and capabilities to repair DNA damage induced by UV-C or X-ray exposures in vitro. Materials and To estimate cytogenetic damage, the analysis of sister chromatid exchange frequency (SCE) was used, and to detect DNA damage the alkaline version of single cell gel electrophoresis (SCGE) was applied. To analyze cellular susceptibility, lymphocytes were exposed to 6 J/m2 of UV-C or irradiated with 2 Gy of X-rays. After challenging exposures, cells were incubated for 2 h with or without the presence of cellular mitogen (phytohemagglutinin - PHA). The study did not show statistically significant differences either between the groups, levels of DNA damage (measured as the percentage of cells with comets or comet tail moments), or sister chromatid exchanges. Neither were there significant differences in the levels of DNA damage (measured as tail moment and comet length) detected in UV-C exposed lymphocytes after 2 h incubation in the presence or in the absence of PHA stimulating cells and in the susceptibility to X-ray radiation of lymphocytes between the groups of non-exposed persons and those occupationally exposed to mercury vapors. In the group exposed to mercury vapors, however, statistically significantly higher levels of non-repaired DNA damage measured in X-ray irradiated lymphocytes after 2 h of incubation, with or without the presence of mitogen were observed compared to controls. Significant differences were observed in all types of DNA damage measures (comet tail length, % of DNA in the comet and comet tail moments). As a result, lymphocytes of donors exposed to mercury vapors showed a statistically lower repair efficiency of X-ray-induced DNA damage both in non-stimulated (70.0% for the exposed, 85.7% for the non-exposed) and stimulated (84

  12. The effects of biological and life-style factors on baseline frequencies of chromosome aberrations in human lymphocytes

    Directory of Open Access Journals (Sweden)

    Hilada Nefic

    2014-01-01

    Full Text Available Objective: This study investigated the influence of sex and ageing on chromosomal damage and the role of life-style habits on the frequency of chromosomal aberrations (CAs in peripheral blood lymphocytes (PBLs of healthy Bosnian subjects. Materials and Methods: Peripheral blood samples were obtained from 100 healthy, unrelated individuals in Bosnia and Herzegovina during 2010 and 2011. Chromosome preparations were made by dropping and air drying and slides were stained with 10% Giemsa solution (pH 6.8. The cytogenetic analysis was carried out in a cytogenetic laboratory in the Department of Biology of the Faculty of Science in Sarajevo. The category of total structural CAs was sub classified as chromosome-type aberrations (CSAs and chromatid-type aberrations (CTAs while the category of total numerical CAs was sub classified as aneuploid and polyploid mitoses. All statistical analyses were carried out using Microsoft Excel 2010 (Microsoft Corporation and the Windows Kwikstat Winks SDA 7.0.2 statistical software package (Texa Soft Cedar Hill, Texas. Results: Cytogenetic analysis revealed the average number of structural CAs was 2.84 and of numerical CAs was 9.56. There was a significant increase in the frequency of chromosome-type aberrations (1.92 compared with chromatid-type aberrations (CTAs (0.92 and a significant increase in the frequency of aneuploid (8.83 compared with polyploid (0.73 mitoses. Significant positive correlations between age and CTAs in human PBLs were also demonstrated. Additional statistical analysis showed that ageing increase number of numerical CAs in lymphocytes of drinkers. The frequency of structural CAs of females exposed to radiation was significantly greater than in males. Analysis indicates the presence of a positive association between CAs and smoking in younger subjects but a negative correlation between aberrant cells frequencies and alcohol in older drinkers. Conclusion: The results of the study support the

  13. Evaluation of antigenotoxic effects of carotenoids from green algae Chlorococcum humicola using human lymphocytes

    Institute of Scientific and Technical Information of China (English)

    Bhagavathy S; Sumathi P

    2012-01-01

    Objective:To identify the available phytochemicals and carotenoids in the selected green algae and evaluate the potential genotoxic/antigenotoxic effect using lymphocytes. Methods:Organic solvent extracts of Chlorococcum humicola (C. humicola) were used for the phytochemical analysis. The available carotenoids were assessed by HPLC, and LC-MS analysis. The genotoxicity was induced by the benzo(a)pyrene in the lymphocyte culture, the genotoxic and antigenotoxic effects of algal carotenoids with and without genotoxic inducer were evaluated by chromosomal aberration (CA), sister chromatid exchange (SCE) and micronucleus assay (MN). Results: The results of the analysis showed that the algae were rich in carotenoids and fatty acids. In the total carotenoids lutein,β-carotene and α-carotene were found to be present in higher concentration. The frequency of CA and SCE increased by benzo(a)pyrene were significantly decreased by the carotenoids (P<0.05 for CA, P<0.001 for SCE). The MN frequencies of the cells were significantly decreased by the treatment with carotenoids when compared with the positive controls (P<0.05). Conclusions:The findings of the present study demonstrate that, the green algae C. humicola is a rich source of bioactive compounds especially carotenoids which effectively fight against environmental genotoxic agents, the carotenoids itself is not a genotoxic substance and should be further considered for its beneficial effects.

  14. Xanthium strumarium L. Extracts Produce DNA Damage Mediated by Cytotoxicity in In Vitro Assays but Does Not Induce Micronucleus in Mice

    Directory of Open Access Journals (Sweden)

    Janet Piloto Ferrer

    2014-01-01

    Full Text Available Xanthium strumarium L. is a member of the Asteraceae commonly used in Cuba, mainly as diuretic. Some toxic properties of this plant have also been reported and, to date, very little is known about its genotoxic properties. The present work aims was to evaluate the potential cytotoxic and genotoxic risk of whole extract from Xanthium strumarium L. whole extract of aerial parts. No positive response was observed in a battery of four Salmonella typhimurium strains, when exposed to concentrations up to 5 mg/plate, with and without mammalian metabolic activation (liver microsomal S9 fraction from Wistar rats. In CHO cells, high concentrations (25–100 μg/mL revealed significant reduction in cell viability. Results from sister chromatid exchanges, chromosome aberrations, and comet assay showed that X. strumarium extract is genotoxic at the highest concentration used, when clear cytotoxic effects were also observed. On the contrary, no increase in micronuclei frequency in bone marrow cells was observed when the extract was orally administered to mice (100, 500, and 2000 mg/Kg doses. The data presented here constitute the most complete study on the genotoxic potential of X. strumarium L. and show that the extract can induce in vitro DNA damage at cytotoxic concentrations.

  15. Multistep assembly of DNA condensation clusters by SMC.

    Science.gov (United States)

    Kim, HyeongJun; Loparo, Joseph J

    2016-01-01

    SMC (structural maintenance of chromosomes) family members play essential roles in chromosome condensation, sister chromatid cohesion and DNA repair. It remains unclear how SMCs structure chromosomes and how their mechanochemical cycle regulates their interactions with DNA. Here we used single-molecule fluorescence microscopy to visualize how Bacillus subtilis SMC (BsSMC) interacts with flow-stretched DNAs. We report that BsSMC can slide on DNA, switching between static binding and diffusion. At higher concentrations, BsSMCs form clusters that condense DNA in a weakly ATP-dependent manner. ATP increases the apparent cooperativity of DNA condensation, demonstrating that BsSMC can interact cooperatively through their ATPase head domains. Consistent with these results, ATPase mutants compact DNA more slowly than wild-type BsSMC in the presence of ATP. Our results suggest that transiently static BsSMC molecules can nucleate the formation of clusters that act to locally condense the chromosome while forming long-range DNA bridges. PMID:26725510

  16. Ultraviolet-induced chromosomal instability in cultured fibroblasts of heterozygote carriers for xeroderma pigmentosum

    International Nuclear Information System (INIS)

    Fibroblast cultures of seven patients with xeroderma pigmentosum (XP), 19 healthy sibs or parents of XP patients (XP-heterozygotes), and 24 healthy normal controls were studied for chromosome instability induced by ultraviolet rays (UV). We used a UV source that contained predominantly UV-A and UV-B at an intensity of 500 J/m2 and evaluated the induction of micronuclei (MN) and sister chromatid exchange (SCE). the XP homozygotes had a UV sensitivity that was clearly above that of all heterozygotes and normal controls. Heterozygotes had an increased rate of UV-induced MN (4.76 ± 1.96 vs. 1.82 ± 2.05, p less than 0.0001) and increased UV induction of SCE (13.21 ± 3.49 vs. 9.01 ± 1.25, p less than 0.001), as compared to normal controls. These data support epidemiologic findings that suggest that XP heterozygotes are particularly cancer prone. In addition, the determination of the UV sensitivity in vitro as described may be used for genetic counseling of asymptomatic relatives of XP patients

  17. Xeroderma pigmentosum and medulloblastoma: chromosomal damage to lymphocytes during radiotherapy

    International Nuclear Information System (INIS)

    The effects of radiotherapy on a patient with xeroderma pigmentosum (XP) of complementation group C and medulloblastoma are reported. His lymphocytes showed no x-ray-induced chromatid damage, but unstable chromosomal aberrations increased throughout the course of radiotherapy as observed also in two other children (patients 2 and 3) with a similar tumor. Such damage was more dependent on spinal than cranial irradiation, lowest in the XP patient and highest in patient 3. Interindividual differences seemed largely due to the relative volume of body irradiated, but the damage in patient 3 remained relatively high even after accounting for such a factor. A maximum of 36, 68, and 77% of lymphocytes had aberrations in the XP and patients 2 and 3, respectively, but chromosomal damage did not show a Poisson distribution and indicated admixture of irradiated and nonirradiated cells. The relative frequency of the irradiated cells was estimated and seemed proportional to the ratios of the average irradiated field to the total body area. The XP patient showed no preferential loss of highly damaged cells and seemed not to suffer excessive chromosomal damage; he had a normal clinical response to and a favorable outcome of radiotherapy. These findings reduce anxiety on the use of radiotherapy in XP patients or at least in those of group C

  18. The validity of sedimentation data from high molecular weight DNA and the effects of additives on radiation-induced single-strand breakage

    International Nuclear Information System (INIS)

    The optimization of many of the factors governing reproducible sedimentation behaviour of high molecular weight single-strand DNA in a particular alkaline sucrose density gradient system is described. A range of angular momenta is defined for which a constant strand breakage efficiency is required, despite a rotor speed effect which increases the measured molecular weights at decreasing rotor speeds for larger DNA molecules. The possibility is discussed that the bimodal control DNA profiles obtained after sedimentation at 11 500 rev/min (12 400 g) or less represent structural subunits of the chromatid. The random induction of single-strand DNA breaks by ionizing radiation is demonstrated by the computer-derived fits to the experimental profiles. The enhancement of single-strand break (SSB) yields in hypoxic cells by oxygen, para-nitroacetophenone (PNAP), or any of the three nitrofuran derivatives used was well correlated with increased cell killing. Furthermore, reductions in SSB yields for known hydroxyl radical (OH.) scavengers correlates with the reactivities of these compounds toward OH.. This supports the contention that some type of OH.-induced initial lesion, which may ultimately be expressed as an unrepaired or misrepaired double-strand break, constitutes a lethal event. (author)

  19. Differences in genotoxic activity of alpha-Ni3S2 on human lymphocytes from nickel-hypersensitized and nickel-unsensitized donors.

    Science.gov (United States)

    Arrouijal, F Z; Marzin, D; Hildebrand, H F; Pestel, J; Haguenoer, J M

    1992-05-01

    The genotoxic activity of alpha-Ni3S2 was assessed on human lymphocytes from nickel-hypersensitized (SSL) and nickel-unsensitized (USL) subjects. Three genotoxicity tests were performed: the sister chromatid exchange (SCE) test, the metaphase analysis test and the micronucleus test. (i) The SCE test (3-100 micrograms/ml) showed a weak but statistically significant increase in the number of SCE in both lymphocyte types with respect to controls, USL presenting a slightly higher SCE incidence but only at one concentration. (ii) The metaphase analysis test demonstrated a high dose-dependent clastogenic activity of alpha-Ni3S2 in both lymphocyte types. The frequency of chromosomal anomalies was significantly higher in USL than in SSL for all concentrations applied. (iii) The micronucleus test confirmed the dose-dependent clastogenic activity of alpha-Ni3S2 and the differences already observed between USL and SSL, i.e. the number of cells with micronuclei was statistically higher in USL. Finally, the incorporation study with alpha-63Ni3S2 showed a higher uptake of its solubilized fraction by USL. This allows an explanation of the different genotoxic action of nickel on the two cell types. In this study we demonstrated that hypersensitivity has an influence on the incorporation of alpha-Ni3S2 and subsequently on the different induction of chromosomal aberrations in human lymphocytes. PMID:1602972

  20. Characterization of UV radiation sensitive frog cell lines

    International Nuclear Information System (INIS)

    Twenty-one subclones of nine frog cell isolates were tested for sensitivity to a panel of DNA damaging agents. Two clones were identified which had a greater than wild type level of sensitivity to UV radiation but had a wild type level of sensitivity to the other agents. These clones were the haploid RRP602-7 and the diploid RRP802-1. RRP802-1 was found to be unstable with respect to UV sensitivity. The line was cloned in order to isolate stable sensitive and wild type derivatives. RRP802-1-16, a UV sensitive clone and RRP802-1-13, a clone with a wild type level of sensitivity to UV radiation, were isolated. The UV radiation sensitivity of RRP602-7, RRP802-1 and RRP802-1-16 did not correlate with cell size, cell shape, cell cycle distribution or ploidy. The cell cycle distribution after UV irradiation, the rate of DNA synthesis after UV-irradiation, the DNA polymerase α activity and the sister chromatid exchange frequency were all measured in RRP602-7, RRP802-1 and RRP802-1-16 in order to examine the DNA repair capacity. The presence of DNA repair pathways was examined directly in RRP602-7, RRP802-1 and RRP802-1-16. All were found to be proficient in photo-reactivation repair and postreplication repair of UV elicited DNA damage

  1. H4K20me0 marks post-replicative chromatin and recruits the TONSL₋MMS22L DNA repair complex

    Energy Technology Data Exchange (ETDEWEB)

    Saredi, Giulia; Huang, Hongda; Hammond, Colin M.; Alabert, Constance; Bekker-Jensen, Simon; Forne, Ignasi; Reverón-Gómez, Nazaret; Foster, Benjamin M.; Mlejnkova, Lucie; Bartke, Till; Cejka, Petr; Mailand, Niels; Imhof, Axel; Patel, Dinshaw J.; Groth, Anja [UCopenhagen; (MSKCC); (ICL); (LMU); (Zurich)

    2016-06-22

    Here, we report that after DNA replication, chromosomal processes including DNA repair and transcription take place in the context of sister chromatids. While cell cycle regulation can guide these processes globally, mechanisms to distinguish pre- and post-replicative states locally remain unknown. In this paper we reveal that new histones incorporated during DNA replication provide a signature of post-replicative chromatin, read by the human TONSL–MMS22L1, 2, 3, 4 homologous recombination complex. We identify the TONSL ankyrin repeat domain (ARD) as a reader of histone H4 tails unmethylated at K20 (H4K20me0), which are specific to new histones incorporated during DNA replication and mark post-replicative chromatin until the G2/M phase of the cell cycle. Accordingly, TONSL–MMS22L binds new histones H3–H4 both before and after incorporation into nucleosomes, remaining on replicated chromatin until late G2/M. H4K20me0 recognition is required for TONSL–MMS22L binding to chromatin and accumulation at challenged replication forks and DNA lesions. Consequently, TONSL ARD mutants are toxic, compromising genome stability, cell viability and resistance to replication stress. Finally, together, these data reveal a histone-reader-based mechanism for recognizing the post-replicative state, offering a new angle to understand DNA repair with the potential for targeted cancer therapy.

  2. Radio and Chemo protective Properties of Hesperidin against Genotoxicity Induced by Gamma Radiation and/or Paraquat in Rat Bone Marrow Cells

    International Nuclear Information System (INIS)

    The Protective effect of hesperidin (HES), a flavonone glucoside, was investigated in rat bone marrow cells against genotoxicity induced by ?-irradiation (2Gy), and/or paraquat (PQ) herbicide. Rats were orally (gavages) pre-treated with solution of HES at dose (160 mg/ kg body wt) for five consecutive days. The fifth day 45 min after treatment, the rats were exposed to ?-irradiation and/or intera peritoneal injected with 10 mg/kg body wt PQ. Animals were sacrificed after 24 h for the evaluation of structural chromosomal aberrations, micro nucleated polychromatic erythrocytes (MnPCEs) micro nucleated normo chromatic erythrocytes (MnNCEs) and the ratio of polychromatic erythrocytes (PCEs) count to the total number of polychromatic erythrocytes and normo chromatic erythrocytes (NCEs). HES reduces the frequencies of MnPCEs and increases the ratio of the PCEs in the rat bone marrow compared with the non drug-treated exposed groups (P< 0.01). Chromatid type aberrations in PQ group, chromosome type aberrations in irradiated group and total aberrations were reduced in pre-treated HES groups (P< 0.05). This study demonstrates that HES has a powerful protective effect on radiation and/or chemical induced chromosome aberrations and DNA damage and on the decline in cell proliferation in rat bone marrow

  3. Assessment of cytotoxic and cytogenetic effects of a 1,2,5-thiadiazole derivative on CHO-K1 cells. Its application as corrosion inhibitor

    International Nuclear Information System (INIS)

    This work focuses on the possible use of phenanthro[9,10-c]-1,2,5-thiadiazole 1,1-dioxide (TDZ) as a harmless corrosion inhibitor. TDZ range-dose providing minimum adverse effects to the environment and human health, with satisfactory corrosion-inhibiting properties was evaluated. Cytotoxicity and genotoxicity of TDZ at 0.57-12.50 μM concentration range were tested by neutral red, chromosomal aberrations, mitotic index, and colony formation assays. Results showed a significant increase of chromatid-type aberrations for the highest concentration of TDZ assayed (12.50 μM). Additionally, a reduction in the proliferative rate for lower concentrations was detected by the MI assay. We concluded that TDZ should be used at concentrations lower than 1.16 μM. Corrosion assays performed showed good inhibition effect (ca. 50%) at low (0.65 μM) TDZ concentration. Consequently, our results indicated that TDZ induced a time- and dose-dependent genotoxic and cytotoxic response on CHO-K1 cells. Short assays should be complemented with long exposure tests to simulate chronic contact with TDZ since lower threshold levels may be found for shorter exposures and a wrong safety range could be determined.

  4. Transcription-coupled homologous recombination after oxidative damage.

    Science.gov (United States)

    Wei, Leizhen; Levine, Arthur Samuel; Lan, Li

    2016-08-01

    Oxidative DNA damage induces genomic instability and may lead to mutagenesis and carcinogenesis. As severe blockades to RNA polymerase II (RNA POLII) during transcription, oxidative DNA damage and the associated DNA strand breaks have a profoundly deleterious impact on cell survival. To protect the integrity of coding regions, high fidelity DNA repair at a transcriptionally active site in non-dividing somatic cells, (i.e., terminally differentiated and quiescent/G0 cells) is necessary to maintain the sequence integrity of transcribed regions. Recent studies indicate that an RNA-templated, transcription-associated recombination mechanism is important to protect coding regions from DNA damage-induced genomic instability. Here, we describe the discovery that G1/G0 cells exhibit Cockayne syndrome (CS) B (CSB)-dependent assembly of homologous recombination (HR) factors at double strand break (DSB) sites within actively transcribed regions. This discovery is a challenge to the current dogma that HR occurs only in S/G2 cells where undamaged sister chromatids are available as donor templates. PMID:27233112

  5. Protective Effect of Prolactin against Methylmercury-Induced Mutagenicity and Cytotoxicity on Human Lymphocytes

    Directory of Open Access Journals (Sweden)

    Liz Carmem Silva-Pereira

    2014-09-01

    Full Text Available Mercury exhibits cytotoxic and mutagenic properties as a result of its effect on tubulin. This toxicity mechanism is related to the production of free radicals that can cause DNA damage. Methylmercury (MeHg is one of the most toxic of the mercury compounds. It accumulates in the aquatic food chain, eventually reaching the human diet. Several studies have demonstrated that prolactin (PRL may be differently affected by inorganic and organic mercury based on interference with various neurotransmitters involved in the regulation of PRL secretion. This study evaluated the cytoprotective effect of PRL on human lymphocytes exposed to MeHg in vitro, including observation of the kinetics of HL-60 cells (an acute myeloid leukemia lineage treated with MeHg and PRL at different concentrations, with both treatments with the individual compounds and combined treatments. All treatments with MeHg produced a significant increase in the frequency of chromatid gaps, however, no significant difference was observed in the chromosomal breaks with any treatment. A dose-dependent increase in the mitotic index was observed for treatments with PRL, which also acts as a co-mitogenic factor, regulating proliferation by modulating the expression of genes that are essential for cell cycle progression and cytoskeleton organization. These properties contribute to the protective action of PRL against the cytotoxic and mutagenic effects of MeHg.

  6. Cancer predictive value of cytogenetic markers used in occupational health surveillance programs. A report from an ongoing study by the European Study Group on Cytogenetic Biomarkers and Health

    Energy Technology Data Exchange (ETDEWEB)

    Hagmar, Lars; Stroemberg, Ulf; Mikoczy, Zoli; Tinnerberg, Hakan; Skerfving, Staffan [Department of Occupational and Environmental Medicine, Lund University, S-221 85 Lund (Sweden); Bonassi, Stefano; Lando, Cecilia [Department of Environmental Epidemiology, Istituto Nazionale per la Ricerca sul Cancro, Viale Benedetto XV, I-1016132 Genoa (Italy); Hansteen, Inger-Lise [Department of Occupational Medicine, Telemark Central Hospital, N-3710 Skien (Norway); Montagud, Alicia Huici [Centro Nacional de Condiciones de Trabajo, Instituto Nacional de Seguridad e Higiene en el Trabajo, Dulcet 2-10, ES-08034 Barcelona (Spain); Knudsen, Lisbeth [National Institute of Occupational Health, Lersoe Parkalle 105, DK-2100 Copenhagen (Denmark); Norppa, Hannu [Finnish Institute of Occupational Health, Topeliuksekatu 41 aA, FIN-00250 Helsinki (Finland); Reuterwall, Christina [National Institute of Work Life, S-171 84 Solna (Sweden); Broegger, Anton [Norwegian Radium Hospital, Oslo (Norway); Forni, Alessandra [Istituto di Medicina del Lavoro Clinica del Lavoro `L. Devoto`, Milan (Italy); Hoegstedt, Benkt [Department of Occupational Medicine, Central Hospital, Halmstad (Sweden); Lambert, Bo [Department of Environmental Medicine, Centre for Nutrition and Toxicology, Karolinska Institute, Stockholm (Sweden); Mitelman, Felix [Department of Clinical Genetics, Lund University, Lund (Sweden); Nordenson, Ingrid [National Institute of Work Life, Umea (Sweden); Salomaa, Sisko [Finnish Center for Radiation and Nuclear Safety, Helsinki (Finland)

    1998-09-20

    The cytogenetic endpoints in peripheral blood lymphocytes: chromosomal aberrations (CA), sister chromatid exchange (SCE) and micronuclei (MN) are established biomarkers of exposure for mutagens or carcinogens in the work environment. However, it is not clear whether these biomarkers also may serve as biomarkers for genotoxic effects which will result in an enhanced cancer risk. In order to assess this problem, Nordic and Italian cohorts were established, and preliminary results from these two studies indicated a predictive value of CA frequency for cancer risk, whereas no such associations were observed for SCE or MN. A collaborative study between the Nordic and Italian research groups, will enable a more thorough evaluation of the cancer predictivity of the cytogenetic endpoints. We here report on the establishment of a joint data base comprising 5271 subjects, examined 1965-1988 for at least one cytogenetic biomarker. Totally, 3540 subjects had been examined for CA, 2702 for SCE and 1496 for MN. These cohorts have been followed-up with respect to subsequent cancer mortality or cancer incidence, and the expected values have been calculated from rates derived from the general populations in each country. Stratified cohort analyses will be performed with respect to the levels of the cytogenetic biomarkers. The importance of potential effect modifiers such as gender, age at test, and time since test, will be evaluated using Poisson regression models. The remaining two potential effect modifiers, occupational exposures and smoking, will be assessed in a case-referent study within the study base

  7. TRITOX: a multiple parameter evaluation of tritium toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Carsten, A.L.

    1982-01-01

    The increased use of nuclear reactors for power generation will lead to the introduction of tritium into the environment. The need for assessing possible immediate and long-term effects of exposure to this tritium led to the development of a broad program directed towards evaluating the possible somatic and genetic effects of continuous exposure to tritiated water (HTO). Among the parameters measured are the genetic, cytogenetic, reproductive efficiency, growth, nonspecific lifetime shortening, bone marrow cellularity and stem cell content, relative biological effectiveness as compared to /sup 137/Cesium gamma exposure, and related biochemical and microdosimetric evaluations. These parameters have been evaluated on animals maintained on HTO at 10 to 100 times the maximum permissible concentration (0.03 - 3.0 ..mu..Ci/ml) for HTO. Dominant lethal mutations, chromosome aberrations in regenerating liver, increased sister chromatid exchanges in bone marrow and reduction in bone marrow stem cell content have been observed at the higher concentrations. The relative biological effectiveness for HTO ingestion as compared to external /sup 137/Cesium gamma exposures has been found to be between 1 and 2.

  8. Novel cell death by downregulation of eEF1A1 expression in tetraploids.

    Science.gov (United States)

    Kobayashi, Y; Yonehara, S

    2009-01-01

    When duplicated sister chromatids are not properly compacted in mitosis, chromosomes are mis-segregated, inducing genetically unstable tetraploidy known to facilitate aneuploid malignancies. Here, we show that tetraploid cells produced by impaired chromosomal condensation are eliminated by a novel type of cell death different from caspase-dependent apoptosis. The cell death was associated with downregulation of eukaryotic translation elongation factor-1 alpha 1 (eEF1A1/EF-1alpha) expression in conjunction with accumulation of its mRNA in processing bodies (P bodies). Importantly, expression of exogenous eEF1A1 was shown to inhibit the caspase-independent cell death, and a similar cell death was observed after inducing the expression of short hairpin RNA specific for eEF1A1. Furthermore, the number of spontaneously arising binucleated cells was indicated to increase several fold during 1- to 2-week cultivation after initiation of exogenous eEF1A expression. Taken together, the novel cell death machinery should help to eliminate abnormal tetraploid cells and inhibit tumorigenesis. PMID:18820646

  9. Summary update of the Brookhaven tritium toxicity program with emphasis on recent cytogenetic and lifetime-shortening studies

    International Nuclear Information System (INIS)

    A number of years ago a multiparameter program to evaluate the toxicity of tritiated water (HTO) was undertaken in the Medical Department at Brookhaven National Laboratory. The results of most of these studies have been published and will receive brief attention. Emphasis will be placed on the unpublished studies involving the induction of sister chromatid exchanges (SCE's) in bone marrow of mice, new biochemical information, and preliminary results on lifetime-shortening and carcinogenesis. In brief, male Hale-Stoner Brookhaven (HSB) mice maintained on HTO concentrations ranging from 3.0 to 30.0 μCi/ml exhibited essentially the same number of SCE's per cell throughout their lifetime. Control mice showed a decrease in number of SCE's with age. The lack of a dose-response effect and the constant level of SCE's in HTO mice as compared to controls will be discussed. In the carcinogenesis study C57BL/6J male mice received various x-ray or HTO regimens. Mortality data from these and other studies in which CBA/Ca/BNL mice received single x-ray exposures or equivalent integrated dose exposures by single HTO injections will be discussed. 25 refs., 4 figs

  10. Structure, Function, and Evolution of Rice Centromeres

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Jiming

    2010-02-04

    The centromere is the most characteristic landmark of eukaryotic chromosomes. Centromeres function as the site for kinetochore assembly and spindle attachment, allowing for the faithful pairing and segregation of sister chromatids during cell division. Characterization of centromeric DNA is not only essential to understand the structure and organization of plant genomes, but it is also a critical step in the development of plant artificial chromosomes. The centromeres of most model eukaryotic species, consist predominantly of long arrays of satellite DNA. Determining the precise DNA boundary of a centromere has proven to be a difficult task in multicellular eukaryotes. We have successfully cloned and sequenced the centromere of rice chromosome 8 (Cen8), representing the first fully sequenced centromere from any multicellular eukaryotes. The functional core of Cen8 spans ~800 kb of DNA, which was determined by chromatin immunoprecipitation (ChIP) using an antibody against the rice centromere-specific H3 histone. We discovered 16 actively transcribed genes distributed throughout the Cen8 region. In addition to Cen8, we have characterized eight additional rice centromeres using the next generation sequencing technology. We discovered four subfamilies of the CRR retrotransposon that is highly enriched in rice centromeres. CRR elements are constitutively transcribed and different CRR subfamilies are differentially processed by RNAi. These results suggest that different CRR subfamilies may play different roles in the RNAi-mediated pathway for formation and maintenance of centromeric chromatin.

  11. Biochemical toxicity of benzene.

    Science.gov (United States)

    Rana, S V S; Verma, Yeshvandra

    2005-04-01

    Human exposure to benzene in work environment is a global occupational health problem. After inhalation or absorption, benzene targets organs viz. liver, kidney, lung, heart and brain etc. It is metabolized mainly in the liver by cytochrome P450 multifunctional oxygenase system. Benzene causes haematotoxicity through its phenolic metabolites that act in concert to produce DNA strand breaks, chromosomal damage, sister chromatid exchange, inhibition of topoisomerase II and damage to mitotic spindle. The carcinogenic and myelotoxic effects of benzene are associated with free radical formation either as benzene metabolites or lipid peroxidation products. Benzene oxide and phenol have been considered as proheptons. Liver microsomes play an important role in biotransformation of benzene whereas in kidney, it produces degenerative intracellular changes. Cohort studies made in different countries suggest that benzene induces multiple myeloma in petrochemical workers. Though extensive studies have been performed on its toxicity, endocrinal disruption caused by benzene remains poorly known. Transgenic cytochrome P450 IIE1 mice may help in understanding further toxic manifestations of benzene.

  12. Assessment of cytotoxic and cytogenetic effects of a 1,2,5-thiadiazole derivative on CHO-K1 cells. Its application as corrosion inhibitor

    Energy Technology Data Exchange (ETDEWEB)

    Grillo, C.A. [Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas (INIFTA, CCT La Plata-CONICET), Facultad de Ciencias Exactas, Departamento de Quimica, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, 1900 La Plata (Argentina); Mirifico, M.V. [Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas (INIFTA, CCT La Plata-CONICET), Facultad de Ciencias Exactas, Departamento de Quimica, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, 1900 La Plata (Argentina); Facultad de Ingenieria, Areas Departamentales Ingenieria Quimica and Mecanica, Universidad Nacional de La Plata, Calle 47 y 1, 1900 La Plata (Argentina); Morales, M.L. [Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas (INIFTA, CCT La Plata-CONICET), Facultad de Ciencias Exactas, Departamento de Quimica, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, 1900 La Plata (Argentina); Reigosa, M.A. [IMBICE (Instituto Multidisciplinario de Biologia Celular), CICPBA, CONICET, Calle 526 entre 10 y 11, 1900 La Plata (Argentina); Mele, M. Fernandez Lorenzo de, E-mail: mmele@inifta.unlp.edu.ar [Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas (INIFTA, CCT La Plata-CONICET), Facultad de Ciencias Exactas, Departamento de Quimica, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, 1900 La Plata (Argentina); Facultad de Ingenieria, Areas Departamentales Ingenieria Quimica and Mecanica, Universidad Nacional de La Plata, Calle 47 y 1, 1900 La Plata (Argentina)

    2009-10-30

    This work focuses on the possible use of phenanthro[9,10-c]-1,2,5-thiadiazole 1,1-dioxide (TDZ) as a harmless corrosion inhibitor. TDZ range-dose providing minimum adverse effects to the environment and human health, with satisfactory corrosion-inhibiting properties was evaluated. Cytotoxicity and genotoxicity of TDZ at 0.57-12.50 {mu}M concentration range were tested by neutral red, chromosomal aberrations, mitotic index, and colony formation assays. Results showed a significant increase of chromatid-type aberrations for the highest concentration of TDZ assayed (12.50 {mu}M). Additionally, a reduction in the proliferative rate for lower concentrations was detected by the MI assay. We concluded that TDZ should be used at concentrations lower than 1.16 {mu}M. Corrosion assays performed showed good inhibition effect (ca. 50%) at low (0.65 {mu}M) TDZ concentration. Consequently, our results indicated that TDZ induced a time- and dose-dependent genotoxic and cytotoxic response on CHO-K1 cells. Short assays should be complemented with long exposure tests to simulate chronic contact with TDZ since lower threshold levels may be found for shorter exposures and a wrong safety range could be determined.

  13. Discovery of benzo[e]pyridoindolones as kinase inhibitors that disrupt mitosis exit while erasing AMPK-Thr172 phosphorylation on the spindle.

    Science.gov (United States)

    Le, Ly-Thuy-Tram; Couvet, Morgane; Favier, Bertrand; Coll, Jean-Luc; Nguyen, Chi-Hung; Molla, Annie

    2015-09-01

    Aurora kinases play an essential role in mitotic progression and are attractive targets in cancer therapy. The first generation of benzo[e]pyridoindole exhibited powerful aurora kinase inhibition but their low solubility limited further development. Grafting a pyperidine-ethoxy group gives rise to a hydrosoluble inhibitor: compound C5M.C5M could efficiently inhibit the proliferation of cells from different origins. C5M prevented cell cycling, induced a strong mitotic arrest then, cells became polyploid and finally died. C5M did not impair the spindle checkpoint, the separation of the sister chromatids and the transfer of aurora B on the mid-zone. C5M prevented histone H3 phosphorylation at mitotic entry and erased AMPK-Thr172 phosphorylation in late mitosis. With this unique profile of inhibition, C5M could be useful for understanding the role of phospho-Thr172-AMPK in abscission and the relationship between the chromosomal complex and the energy sensing machinery.C5M is a multikinase inhibitor with interesting preclinical characteristics: high hydro-solubility and a good stability in plasma. A single dose prevents the expansion of multicellular spheroids. C5M can safely be injected to mice and reduces significantly the development of xenograft. The next step will be to define the protocol of treatment and the cancer therapeutic field of this new anti-proliferative drug.

  14. Human Zwint-1 Specifies Localization of Zeste White 10 to Kinetochores and Is Essential for Mitotic Checkpoint Signaling

    Institute of Scientific and Technical Information of China (English)

    HongmeiWang; XiaoyuHu; XiaDing; ZhenDou; ZhihongYank; AndrewW.Shaw; MaikunTcng; DonW.Cleveland; MichaelL.Goldberg; LiwenNiu; XucbiaoYao

    2005-01-01

    Chromosome segregation in mitosis is orchestrated by dynamic interaction between spindle microtubules and the kinetochore, a multiprotein complex assembled onto centromeric DNA of the chromosome. Here we show that Zwint-1 is required and is sufficient for kinetochore localization of Zestc White 10 (ZW10) in HeLa cells. Zwint-1 specifies the kinetochore association of ZW10 by interacting with its N-terminal domain. Suppression of synthesis of Zwint-1 by small interfering RNA abolishes the localization of ZW10 to the kinetochore, demonstrating the requirement of Zwint-1 for ZWl0 kinetochore localization. In addition, dcplction of Zwint-1 affects no mitotic arrest but causes aberrant premature chromo. some segregation. These Zwint-l-suppressed cells dis. play chromosome bridge phenotype with sister chromatids inter-connected. Moreover, Zwint-1 is required for stable association of CENP.F and dynamitin but not BUB1 with the kinetochore. Finally, our studies showthat Zwint-1 is a new component of the mitotic check. point, as cells lacking Zwint-1 fail to arrest in mitosis when exposed to microtubule inhibitors, yielding inter. phase cells with multinuclei. As ZWl0 and Zwint.1 are absent from yeast, we reasoned that metazoans evolved an elaborate spindle checkpoint machinery to ensure faithful chromosome segregation in mitosis.

  15. ANKRD53 interacts with DDA3 and regulates chromosome integrity during mitosis.

    Science.gov (United States)

    Kim, Seul; Jang, Chang-Young

    2016-02-12

    Spindle dynamics drives chromosome movement and mitotic progression during mitosis. Microtubule (MT)-associated proteins (MAPs) regulate MT stabilization/destabilization and MT polymerization/depolymerization for congression of sister chromatids at the mitotic equator and subsequent segregation toward the spindle poles. Here, we identified ANKRD53 as a novel DDA3-interacting protein through proteomic analysis. Based on expression profiles, ANKRD53 is phosphorylated by mitotic kinases during mitosis. In ANKRD53-depleted HeLa cells, the progression of mitosis was delayed and the number of unaligned chromosomes increased substantially. In addition, spindle MT polymerization decreased and the spindle assembly checkpoint (SAC) was concomitantly activated by the decreased spindle dynamics in ANKRD53-depleted cells. Although ANKRD53 is recruited to the mitotic spindle by DDA3, it counteracts the activity of DDA3 for spindle MT polymerization. Furthermore, ANKRD53 depletion increased the number of bi-nuclei and polylobed nuclei. Thus, ANKRD53 is recruited to the mitotic spindle by DDA3 and acts as a regulator of spindle dynamics and cytokinesis.

  16. Fission yeast cells undergo nuclear division in the absence of spindle microtubules.

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    Stefania Castagnetti

    Full Text Available Mitosis in eukaryotic cells employs spindle microtubules to drive accurate chromosome segregation at cell division. Cells lacking spindle microtubules arrest in mitosis due to a spindle checkpoint that delays mitotic progression until all chromosomes have achieved stable bipolar attachment to spindle microtubules. In fission yeast, mitosis occurs within an intact nuclear membrane with the mitotic spindle elongating between the spindle pole bodies. We show here that in fission yeast interference with mitotic spindle formation delays mitosis only briefly and cells proceed to an unusual nuclear division process we term nuclear fission, during which cells perform some chromosome segregation and efficiently enter S-phase of the next cell cycle. Nuclear fission is blocked if spindle pole body maturation or sister chromatid separation cannot take place or if actin polymerization is inhibited. We suggest that this process exhibits vestiges of a primitive nuclear division process independent of spindle microtubules, possibly reflecting an evolutionary intermediate state between bacterial and Archeal chromosome segregation where the nucleoid divides without a spindle and a microtubule spindle-based eukaryotic mitosis.

  17. Regulation of NDR1 activity by PLK1 ensures proper spindle orientation in mitosis.

    Science.gov (United States)

    Yan, Maomao; Chu, Lingluo; Qin, Bo; Wang, Zhikai; Liu, Xing; Jin, Changjiang; Zhang, Guanglan; Gomez, Marta; Hergovich, Alexander; Chen, Zhengjun; He, Ping; Gao, Xinjiao; Yao, Xuebiao

    2015-01-01

    Accurate chromosome segregation during mitosis requires the physical separation of sister chromatids which depends on correct position of mitotic spindle relative to membrane cortex. Although recent work has identified the role of PLK1 in spindle orientation, the mechanisms underlying PLK1 signaling in spindle positioning and orientation have not been fully illustrated. Here, we identified a conserved signaling axis in which NDR1 kinase activity is regulated by PLK1 in mitosis. PLK1 phosphorylates NDR1 at three putative threonine residues (T7, T183 and T407) at mitotic entry, which elicits PLK1-dependent suppression of NDR1 activity and ensures correct spindle orientation in mitosis. Importantly, persistent expression of non-phosphorylatable NDR1 mutant perturbs spindle orientation. Mechanistically, PLK1-mediated phosphorylation protects the binding of Mob1 to NDR1 and subsequent NDR1 activation. These findings define a conserved signaling axis that integrates dynamic kinetochore-microtubule interaction and spindle orientation control to genomic stability maintenance.

  18. Evaluation of genotoxic risk and oxidative DNA damage in mammalian cells exposed to mycotoxins, patulin and citrinin

    International Nuclear Information System (INIS)

    Mycotoxins are fungal secondary metabolites with very diversified toxic effects in humans and animals. In the present study, patulin (PAT) and citrinin (CTN), two prevalent mycotoxins, were evaluated for their genotoxic effects and oxidative damage to mammalian cells, including Chinese hamster ovary cells (CHO-K1), human peripheral blood lymphocytes, and human embryonic kidney cells (HEK293). PAT, but not CTN, caused a significant dose-dependent increase in sister chromatid exchange (SCE) frequency in both CHO-K1 and human lymphocytes. PAT also elevated the levels of DNA gap and break in treated CHO-K1. In the single cell gel electrophoresis (SCGE) assay, exposure of HEK293 to concentrations above 15 μM of PAT induced DNA strand breaks; the tail moment values also greatly increased after posttreatment with formamidopyrimidine-DNA glycosylase (Fpg). This suggests that in human cells PAT is a potent clastogen with the ability to cause oxidative damage to DNA. However, no significant change in the tail moment values in CTN-treated cultures was found, suggesting that CTN is not genotoxic to HEK293. Incubation of HEK293 with CTN increased the mRNA level of heat shock protein 70 (HSP70), but not that of human 8-hydroxyguanine DNA glycosylase 1 (hOGG1). PAT treatment did not modulate the expression of either HSP70 or hOGG1 mRNA

  19. Histone-DNA contacts in structure/function relationships of nucleosomes as revealed by crosslinking

    Energy Technology Data Exchange (ETDEWEB)

    Usachenko, S.I. [Univ. of California, Davis, CA (United States); Bradbury, E.M. [Los Alamos National Lab., NM (United States). Life Science Div.]|[Univ. of California, Davis, CA (United States)

    1998-12-31

    The magnitude of the problem of understanding the structure/function relationships of eukaryotic chromosomes can be appreciated from the fact that the human diploid genome contains more than 2 meters of DNA packaged into 46 chromosomes, each at metaphase being several microns in length. Each chromatid of a chromosome contains a single DNA molecule several centimeters in length. In addition to the DNA, chromosomes contain an equal weight of histones and an equal weight of non-histone chromosomal proteins. These histones are the major chromosomal structural proteins. The non-histone chromosomal proteins are involved in the DNA processes of transcription and replication, in chromosome organization and in nuclear architecture. Polytene chromosomes with their bands and interbands and puffs of active genetic loci provide visual evidence for long range order as do the bands and interbands of mammalian metaphase chromosomes. The gentle removal of histones and all but the most tightly bound 2--3% of non-histone proteins from metaphase chromosomes revealed by electron microscopy a residual protein scaffold constraining a halo of DNA loops extending out from the scaffold.

  20. APC/C-Cdh1-dependent anaphase and telophase progression during mitotic slippage

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    Toda Kazuhiro

    2012-02-01

    Full Text Available Abstract Background The spindle assembly checkpoint (SAC inhibits anaphase progression in the presence of insufficient kinetochore-microtubule attachments, but cells can eventually override mitotic arrest by a process known as mitotic slippage or adaptation. This is a problem for cancer chemotherapy using microtubule poisons. Results Here we describe mitotic slippage in yeast bub2Δ mutant cells that are defective in the repression of precocious telophase onset (mitotic exit. Precocious activation of anaphase promoting complex/cyclosome (APC/C-Cdh1 caused mitotic slippage in the presence of nocodazole, while the SAC was still active. APC/C-Cdh1, but not APC/C-Cdc20, triggered anaphase progression (securin degradation, separase-mediated cohesin cleavage, sister-chromatid separation and chromosome missegregation, in addition to telophase onset (mitotic exit, during mitotic slippage. This demonstrates that an inhibitory system not only of APC/C-Cdc20 but also of APC/C-Cdh1 is critical for accurate chromosome segregation in the presence of insufficient kinetochore-microtubule attachments. Conclusions The sequential activation of APC/C-Cdc20 to APC/C-Cdh1 during mitosis is central to accurate mitosis. Precocious activation of APC/C-Cdh1 in metaphase (pre-anaphase causes mitotic slippage in SAC-activated cells. For the prevention of mitotic slippage, concomitant inhibition of APC/C-Cdh1 may be effective for tumor therapy with mitotic spindle poisons in humans.

  1. Positive feedback promotes mitotic exit via the APC/C-Cdh1-separase-Cdc14 axis in budding yeast.

    Science.gov (United States)

    Hatano, Yuhki; Naoki, Koike; Suzuki, Asuka; Ushimaru, Takashi

    2016-10-01

    The mitotic inhibitor securin is degraded via the ubiquitin ligase anaphase-promoting complex/cyclosome (APC/C)-Cdc20 after anaphase onset. This triggers activation of the mitotic protease separase and thereby sister chromatid separation. However, only a proportion of securin molecules are degraded at metaphase-anaphase transition and the remaining molecules are still present in anaphase. The roles of securin and separase in late mitosis remain elusive. Here, we show that securin still inhibits separase to repress mitotic exit in anaphase in budding yeast. APC/C-Cdh1-mediated securin degradation at telophase further liberated separase, which promotes Cdc14 release and mitotic exit. Separase executed these events via its proteolytic action and that in the Cdc14 early release (FEAR) network. Cdc14 release further activated APC/C-Cdh1 in the manner of a positive feedback loop. Thus, the positive feedback promotes mitotic exit via the APC/C-Cdh1-separase-Cdc14 axis. This study shows the importance of the two-step degradation mode of securin and the role of separase in mitotic exit.

  2. Heterochromatin Protein 1 (HP1) Proteins Do Not Drive Pericentromeric Cohesin Enrichment in Human Cells

    Science.gov (United States)

    Serrano, Ángel; Rodríguez-Corsino, Miriam; Losada, Ana

    2009-01-01

    Sister chromatid cohesion mediated by cohesin is essential for accurate chromosome segregation. Classical studies suggest that heterochromatin promotes cohesion, but whether this happens through regulation of cohesin remains to be determined. Heterochromatin protein 1 (HP1) is a major component of heterochromatin. In fission yeast, the HP1 homologue Swi6 interacts with cohesin and is required for proper targeting and/or stabilization of cohesin at the centromeric region. To test whether this pathway is conserved in human cells, we have examined the behavior of cohesin in cells in which the levels of HP1 alpha, beta or gamma (the three HP1 proteins present in mammalian organisms) have been reduced by siRNA. We have also studied the consequences of treating human cells with drugs that change the histone modification profile of heterochromatin and thereby affect HP1 localization. Our results show no evidence for a requirement of HP1 proteins for either loading of bulk cohesin onto chromatin in interphase or retention of cohesin at pericentric heterochromatin in mitosis. However, depletion of HP1gamma leads to defects in mitotic progression. PMID:19352502

  3. Unique geometry of sister kinetochores in human oocytes during meiosis I may explain maternal age-associated increases in chromosomal abnormalities

    Directory of Open Access Journals (Sweden)

    Jessica Patel

    2016-02-01

    Full Text Available The first meiotic division in human oocytes is highly error-prone and contributes to the uniquely high incidence of aneuploidy observed in human pregnancies. A successful meiosis I (MI division entails separation of homologous chromosome pairs and co-segregation of sister chromatids. For this to happen, sister kinetochores must form attachments to spindle kinetochore-fibres emanating from the same pole. In mouse and budding yeast, sister kinetochores remain closely associated with each other during MI, enabling them to act as a single unified structure. However, whether this arrangement also applies in human meiosis I oocytes was unclear. In this study, we perform high-resolution imaging of over 1900 kinetochores in human oocytes, to examine the geometry and architecture of the human meiotic kinetochore. We reveal that sister kinetochores in MI are not physically fused, and instead individual kinetochores within a pair are capable of forming independent attachments to spindle k-fibres. Notably, with increasing female age, the separation between kinetochores increases, suggesting a degradation of centromeric cohesion and/or changes in kinetochore architecture. Our data suggest that the differential arrangement of sister kinetochores and dual k-fibre attachments may explain the high proportion of unstable attachments that form in MI and thus indicate why human oocytes are prone to aneuploidy, particularly with increasing maternal age.

  4. Assessment of respiratory effect of air pollution: study design on general population samples.

    Science.gov (United States)

    Baldacci, S; Carrozzi, L; Viegi, G; Giuntini, C

    1997-01-01

    The aim of this paper is to describe an epidemiological model to investigate the relationship between respiratory diseases and environmental air pollution. In the Po Delta prospective study, subjects were investigated before and after a large thermoelectric power plant began operating, in 1980 to 1982 and in 1988 to 1991, respectively. The Pisa prospective study was performed in 1986 to 1988 and in 1991 to 1993, before and after the construction of a new expressway that encircles the city from the North to the Southeast. In each survey, subjects completed the interviewer-administered standardized CNR questionnaire on respiratory symptoms/diseases and risk factors, and performed lung function tests. In the second survey of each study, skin prick tests, total serum IgE determination, methacholine challenge test and biomarkers (such as sister chromatide exchanges, micronuclei, chromosomal abnormalities, DNA and hemoglobin adducts) were also performed. Concentrations of total suspended particulate and SO2 in both surveys were higher in urban than in rural areas, as well as symptom/disease prevalences and bronchial reactivity. Subgroups of subjects from the two samples were enrolled to perform a specific study on the acute respiratory effects of indoor pollution; the daily presence of symptoms and measurements of peak expiratory flow (PEF), daily activity pattern, and assessment of the indoor air quality (particulates particulates, especially asthmatics. In conclusion, these studies represent a basis for further analyses to better define the relationship between respiratory health and indoor/outdoor pollutant levels.

  5. Clastogenic Effect of Azadirachtin of Neemix-4.5 On SWR/J Mouse Bone Marrow Cells

    Directory of Open Access Journals (Sweden)

    F. M. Abou-Tarboush1; H. M. El-Ashmaoui2

    2005-03-01

    Full Text Available The clastogenic effect of azadirachtin of neemix-4.5 was investigated in SWR/J mouse bone marrow cells. Males and females, 5 each per treatment time, aged 10­12 weeks and weighing 31.7­33.8 g, were orally administrated 9.0 mg/kg (1/10 LD50 of azadirachtin solution. A control group (5 males and 5 females received only sterile distilled water. The animals were sacrificed 6, 12, 24, 48 or 72 h post- treatment. The chromosome preparations were obtained from bone marrow cells. Chromatid and chromosomal aberrations were investigated in 50 metaphases per animal. No significant differences in the frequency of chromosomal aberrations or in the percentage of mitotic index were observed between the treated male and female mice at any time intervals used. Hence, data from the two sexes were pooled when analyzed statistically. In the prersent study, the dose level 9.0 mg/kg body weight of azadirachtin of neemix-4.5 did not induce any significant (p>0.05 changes in the percentages of mitotic indices or in chromosomal aberrations in the bone marrow cells of treated animals at all time intervals tested compared with the control group. As the pharmacokinetics of azadirachtin is unknown, the essentially negative results in the present study may be due to a lack of genotoxic potential .

  6. Glycidamide genotoxicity modulated by Caspases genes polymorphisms.

    Science.gov (United States)

    de Lima, João Pereira; Silva, Susana N; Rueff, José; Pingarilho, Marta

    2016-08-01

    Acrylamide (AA) is amongst acknowledged carcinogenic dietary factors. Its DNA-reactive metabolite is glycidamide (GA). The present study intended to correlate the role of key polymorphic genes of apoptosis (CASP7, CASP8, CASP9, CASP10, LTA and TNFRSF1B) with biomarkers of effect of DNA damage, namely the sister chromatid exchange assay (SCE) and the comet assay in whole blood cells exposed to GA. The aim was to assess as a proof of concept the role that pro-apoptotic effector proteins might have in the yields of genotoxic effects when those effector proteins are coded by polymorphic genes. Whole blood from a small group of volunteers was exposed to GA to assess DNA damage and the volunteers were genotyped for polymorphic genes related to apoptosis pathways. A relation between the induction of SCE and several variants of the polymorphism CASP8 rs1035142 G>T was observed. Also, a relation between the % tail DNA and the CASP10 I522L polymorphism was found. Furthermore, associations between % tail DNA and several SNP-SNP interactions of CASP8 and CASP10 were found. A possible correlation between DNA damage and the genetic susceptibility, bestowed by polymorphic genes in the apoptosis inducing pathways was verified. PMID:27062911

  7. Genotoxic effect of gamma radiation in vivo rats as evaluated by comet assay and micronucleus assay

    International Nuclear Information System (INIS)

    DNA is one of the most critical site of damage induced by UV, gamma radiation and other the environmental chemical pollutants. Genotoxic evaluation of environmental agents is generally carried out using cytogenetic markers like chromosomal aberrations, sister chromatid exchanges and micronuclei formation. During the recent years Single Cell Gel Electrophoresis/Comet Assay, has emerged as one of the most powerful assays to detect DNA damage at molecular level in any eukaryotic cell. Present studies were undertaken to investigate the effect of gamma radiation at DNA and chromosomal level using comet assay and micronucleus test. Female Wistar rats were exposed to gamma radiation using 60Co Teletherapy machine; 0.125, 0.25, 0.5 and 1.0 Gy at a dose rate of 0.33 Gy/min. Blood and bone marrow samples were processed for comet assay using the standard protocol. Bone marrow cells from femur bone were also processed for micronucleus assay. Results of these studies indicated a dose dependent increase in DNA damage as indicated by increase in tail length (TL), tail moment (TM) and % DNA in tail (% DNA- T). Similarly, a dose dependent increase in the frequency of micronucleated polychromatic erythrocytes (mn-PCEs) was also observed. A good correlation between, DNA damage and the induction of micronucleated erythrocytes was observed. (author)

  8. Genotoxicity of food preservative sodium sorbate in human lymphocytes in vitro.

    Science.gov (United States)

    Mamur, Sevcan; Yüzbaşıoğlu, Deniz; Unal, Fatma; Aksoy, Hüseyin

    2012-10-01

    The genotoxic effects of antimicrobial food additive sodium sorbate (SS) was assessed by using chromosome aberrations (CAs), sister-chromatid exchanges (SCEs), and micronucleus (MN) in cultured human lymphocytes and comet assay in isolated human lymphocytes. Lymphocytes were treated with four concentrations (100, 200, 400 and 800 μg/ml) of SS as well as a negative (sterile distilled water) and a positive control (Mitomycin-C: MMC for cultured lymphocytes and H(2)O(2) for isolated lymphocytes). The result of this study indicated that SS increased the frequency of CAs at both 24 and 48 h period compared to control. When gaps were included, this increase was significant at 200, 400 and 800 μg/ml concentrations at 24 h and, at all concentrations at 48 h treatment time. When gaps were excluded, this increase was significant at only 800 μg/ml concentration at both 24 and 48 h treatments. In addition, SS increased SCEs/cell and MN frequency at 400 and 800 μg/ml concentrations at both 24 and 48 h compared to negative control. Furthermore, this additive caused DNA damage at all concentrations in isolated human lymphocytes after 1 h in vitro exposure. The present results show that SS is genotoxic to the human peripheral blood lymphocytes in vitro at the highest concentrations.

  9. Aberration distribution and chromosomally marked clones in x-irradiated skin

    International Nuclear Information System (INIS)

    Samples of clinically normal human skin were removed from therapeutically X-irradiated areas at intervals of time ranging from one hour to 60 years after completion of radiation treatment. Primary cultures of untransformed fibroblasts from these samples were analysed for surviving chromosomal structural changes using ASG banding techniques. Aberrations of four basic types, reciprocal translocations, terminal deletions, pericentric inversions and paracentric inversions (the last very rare) were found in all samples. Evidence indicates that many of these are secondary aberrations derived from primary chromatid types. Presumptive break points for all aberrations were mapped, and various tests applied to investigate their within-chromosome distributions (the data are unsuitable for valid between-chromosome analysis). For translocations, the within-arm distributions are non-random, principally as the result of a very significant deficiency of break points in terminal segments. Tests for the intrachromosomal changes (pericentric inversions and deletions) are simpler, and in neither case were there significant departure from randomness Two lines of evidence are present in the data for division and migration of chromosomally abnormal cells in vivo: (a) the presence of identical aberrations in cells from different parts of the biopsy; (b) the presence of cells with sequential changes, indicating cell division between the dose fractions of the therapeutic regime. (author)

  10. Unique geometry of sister kinetochores in human oocytes during meiosis I may explain maternal age-associated increases in chromosomal abnormalities.

    Science.gov (United States)

    Patel, Jessica; Tan, Seang Lin; Hartshorne, Geraldine M; McAinsh, Andrew D

    2015-12-30

    The first meiotic division in human oocytes is highly error-prone and contributes to the uniquely high incidence of aneuploidy observed in human pregnancies. A successful meiosis I (MI) division entails separation of homologous chromosome pairs and co-segregation of sister chromatids. For this to happen, sister kinetochores must form attachments to spindle kinetochore-fibres emanating from the same pole. In mouse and budding yeast, sister kinetochores remain closely associated with each other during MI, enabling them to act as a single unified structure. However, whether this arrangement also applies in human meiosis I oocytes was unclear. In this study, we perform high-resolution imaging of over 1900 kinetochores in human oocytes, to examine the geometry and architecture of the human meiotic kinetochore. We reveal that sister kinetochores in MI are not physically fused, and instead individual kinetochores within a pair are capable of forming independent attachments to spindle k-fibres. Notably, with increasing female age, the separation between kinetochores increases, suggesting a degradation of centromeric cohesion and/or changes in kinetochore architecture. Our data suggest that the differential arrangement of sister kinetochores and dual k-fibre attachments may explain the high proportion of unstable attachments that form in MI and thus indicate why human oocytes are prone to aneuploidy, particularly with increasing maternal age.

  11. Radiation exposure: Cytogenetic tests. Chernobyl reactor accident

    International Nuclear Information System (INIS)

    Forty test subjects who, either during or after the reactor accident of Chernobyl (26th April 1986), stayed at a building site at Shlobin 150 km away, were examined for spontaneously occurring as well as mitomycin C-induced Sister Chromatid Exchanges (SCE). The building site staff, who underwent a whole-body radionuclide count upon their return to Austria (June through September 1986), were used for the cytogenetic tests. The demonstration of the SCE was made from whole-blood cultures by the fluorescence/Giemse technique. At last 20 Metaphases of the 2nd mitotic cycle were evaluated per person. The radiation doses of the test subjects were calculated by adding the external exposure determined on the building site, the estimated thyroid dose through I-131, and the measured incorporation of Cs-134 and Cs-137. The subjects were divided into two groups for statistical analysis: One was a more exposed group (proven stay at Shlobin between 26th April and 31st May 1986, mostly working in the open air) and the other a less exposed group for comparison (staying at Shlobin from 1st Juni 1986 and working mainly indoors). (orig.)

  12. Structural Studies Reveal the Functional Modularity of the Scc2-Scc4 Cohesin Loader

    Directory of Open Access Journals (Sweden)

    William C.H. Chao

    2015-08-01

    Full Text Available The remarkable accuracy of eukaryotic cell division is partly maintained by the cohesin complex acting as a molecular glue to prevent premature sister chromatid separation. The loading of cohesin onto chromosomes is catalyzed by the Scc2-Scc4 loader complex. Here, we report the crystal structure of Scc4 bound to the N terminus of Scc2 and show that Scc4 is a tetratricopeptide repeat (TPR superhelix. The Scc2 N terminus adopts an extended conformation and is entrapped by the core of the Scc4 superhelix. Electron microscopy (EM analysis reveals that the Scc2-Scc4 loader complex comprises three domains: a head, body, and hook. Deletion studies unambiguously assign the Scc2N-Scc4 as the globular head domain, whereas in vitro cohesin loading assays show that the central body and the hook domains are sufficient to catalyze cohesin loading onto circular DNA, but not chromatinized DNA in vivo, suggesting a possible role for Scc4 as a chromatin adaptor.

  13. Holliday junction resolution: regulation in space and time.

    Science.gov (United States)

    Matos, Joao; West, Stephen C

    2014-07-01

    Holliday junctions (HJs) can be formed between sister chromatids or homologous chromosomes during the recombinational repair of DNA lesions. A variety of pathways act upon HJs to remove them from DNA, in events that are critical for appropriate chromosome segregation. Despite the identification and characterization of multiple enzymes involved in HJ processing, the cellular mechanisms that regulate and implement pathway usage have only just started to be delineated. A conserved network of core cell-cycle kinases and phosphatases modulate HJ metabolism by exerting spatial and temporal control over the activities of two structure-selective nucleases: yeast Mus81-Mms4 (human MUS81-EME1) and Yen1 (human GEN1). These regulatory cycles operate to establish the sequential activation of HJ processing enzymes, implementing a hierarchy in pathway usage that ensure the elimination of chromosomal interactions which would otherwise interfere with chromosome segregation. Mus81-Mms4/EME1 and Yen1/GEN1 emerge to define a special class of enzymes, evolved to satisfy the cellular need of safeguarding the completion of DNA repair when on the verge of chromosome segregation. PMID:24767945

  14. Stacked thin layers of metaphase chromatin explain the geometry of chromosome rearrangements and banding.

    Science.gov (United States)

    Daban, Joan-Ramon

    2015-10-08

    The three-dimensional organization of tightly condensed chromatin within metaphase chromosomes has been one of the most challenging problems in structural biology since the discovery of the nucleosome. This study shows that chromosome images obtained from typical banded karyotypes and from different multicolour cytogenetic analyses can be used to gain information about the internal structure of chromosomes. Chromatin bands and the connection surfaces in sister chromatid exchanges and in cancer translocations are planar and orthogonal to the chromosome axis. Chromosome stretching produces band splitting and even the thinnest bands are orthogonal and well defined, indicating that short stretches of DNA can occupy completely the chromosome cross-section. These observations impose strong physical constraints on models that attempt to explain chromatin folding in chromosomes. The thin-plate model, which consists of many stacked layers of planar chromatin perpendicular to the chromosome axis, is compatible with the observed orientation of bands, with the existence of thin bands, and with band splitting; it is also compatible with the orthogonal orientation and planar geometry of the connection surfaces in chromosome rearrangements. The results obtained provide a consistent interpretation of the chromosome structural properties that are used in clinical cytogenetics for the diagnosis of hereditary diseases and cancers.

  15. Holocentromeres in Rhynchospora are associated with genome-wide centromere-specific repeat arrays interspersed among euchromatin.

    Science.gov (United States)

    Marques, André; Ribeiro, Tiago; Neumann, Pavel; Macas, Jiří; Novák, Petr; Schubert, Veit; Pellino, Marco; Fuchs, Jörg; Ma, Wei; Kuhlmann, Markus; Brandt, Ronny; Vanzela, André L L; Beseda, Tomáš; Šimková, Hana; Pedrosa-Harand, Andrea; Houben, Andreas

    2015-11-01

    Holocentric chromosomes lack a primary constriction, in contrast to monocentrics. They form kinetochores distributed along almost the entire poleward surface of the chromatids, to which spindle fibers attach. No centromere-specific DNA sequence has been found for any holocentric organism studied so far. It was proposed that centromeric repeats, typical for many monocentric species, could not occur in holocentrics, most likely because of differences in the centromere organization. Here we show that the holokinetic centromeres of the Cyperaceae Rhynchospora pubera are highly enriched by a centromeric histone H3 variant-interacting centromere-specific satellite family designated "Tyba" and by centromeric retrotransposons (i.e., CRRh) occurring as genome-wide interspersed arrays. Centromeric arrays vary in length from 3 to 16 kb and are intermingled with gene-coding sequences and transposable elements. We show that holocentromeres of metaphase chromosomes are composed of multiple centromeric units rather than possessing a diffuse organization, thus favoring the polycentric model. A cell-cycle-dependent shuffling of multiple centromeric units results in the formation of functional (poly)centromeres during mitosis. The genome-wide distribution of centromeric repeat arrays interspersing the euchromatin provides a previously unidentified type of centromeric chromatin organization among eukaryotes. Thus, different types of holocentromeres exist in different species, namely with and without centromeric repetitive sequences. PMID:26489653

  16. The radiosensitivities of the lymphocyte chromosomes of the four mammalian species abundant in the environs of the Philippine Nuclear Power Plant-I

    International Nuclear Information System (INIS)

    The peripheral blood lymphocyte chromosomes of the Filipino, the carabao, the goat, and the ricefield rat, four mammalian species found abundant in the environs of the Philippine Nuclear Power Plant (PNPP-I) in Morong, Bataan, were studied to establish their radiosensitivities and to explore their possible use as biological indicator of radiation effects. The four mammalian species were found to be radiosensitive. Chromosome aberration was induced by gamma-irradiation of whole venous blood. By cytogenetic technique the aberrant chromosomes were evaluated. The aberrant chromosomes may be categorized into chromatid and chromosome types. Of the types seen, it was concluded that dicentrics are the most reliable indicator of radiation effects. In the course of this study a suitable medium was formualted and was found competitive with a commercially prepared medium. The radiosensitivity of the four species based on the frequency of dicentrics differs from each other. A calibration curve was constructed to relate exposure to the observed incidence of dicentrics. This curve is very important in the calculation of the dose corresponding to the observed dicentric yield in case of accidental release of radioactivity in the PNPP-I site. (author)

  17. TRITOX: a multiple parameter evaluation of tritium toxicity

    International Nuclear Information System (INIS)

    The increased use of nuclear reactors for power generation will lead to the introduction of tritium into the environment. The need for assessing possible immediate and long-term effects of exposure to this tritium led to the development of a broad program directed towards evaluating the possible somatic and genetic effects of continuous exposure to tritiated water (HTO). Among the parameters measured are the genetic, cytogenetic, reproductive efficiency, growth, nonspecific lifetime shortening, bone marrow cellularity and stem cell content, relative biological effectiveness as compared to 137Cesium gamma exposure, and related biochemical and microdosimetric evaluations. These parameters have been evaluated on animals maintained on HTO at 10 to 100 times the maximum permissible concentration (0.03 - 3.0 μCi/ml) for HTO. Dominant lethal mutations, chromosome aberrations in regenerating liver, increased sister chromatid exchanges in bone marrow and reduction in bone marrow stem cell content have been observed at the higher concentrations. The relative biological effectiveness for HTO ingestion as compared to external 137Cesium gamma exposures has been found to be between 1 and 2

  18. A closed conformation of the Caenorhabditis elegans separase–securin complex

    Science.gov (United States)

    Bachmann, Gudrun; Richards, Mark W.; Winter, Anja; Beuron, Fabienne; Morris, Edward

    2016-01-01

    The protease separase plays a key role in sister chromatid disjunction and centriole disengagement. To maintain genomic stability, separase activity is strictly regulated by binding of an inhibitory protein, securin. Despite its central role in cell division, the separase and securin complex is poorly understood at the structural level. This is partly owing to the difficulty of generating a sufficient quantity of homogeneous, stable protein. Here, we report the production of Caenorhabditis elegans separase–securin complex, and its characterization using biochemical methods and by negative staining electron microscopy. Single particle analysis generated a density map at a resolution of 21–24 Å that reveals a close, globular structure of complex connectivity harbouring two lobes. One lobe matches closely a homology model of the N-terminal HEAT repeat domain of separase, whereas the second lobe readily accommodates homology models of the separase C-terminal death and caspase-like domains. The globular structure of the C. elegans separase–securin complex contrasts with the more elongated structure previously described for the Homo sapiens complex, which could represent a different functional state of the complex, suggesting a mechanism for the regulation of separase activity through conformational change. PMID:27249343

  19. Suppression of mutagenesis by Rad51D-mediated homologous recombination

    Energy Technology Data Exchange (ETDEWEB)

    Hinz, J M; Tebbs, R S; Wilson, P F; Nham, P B; Salazar, E P; Nagasawa, H; Urbin, S S; Thompson, L H

    2005-11-15

    Homologous recombinational repair (HRR) restores chromatid breaks arising during DNA replication and prevents chromosomal rearrangements that can occur from the misrepair of such breaks. In vertebrates, five Rad51 paralogs are identified that contribute in a nonessential but critical manner to HRR efficiency. We constructed and characterized a Rad51D knockout cell line in widely studied CHO cells. The rad51d mutant (51D1) displays sensitivity to a wide spectrum of induced DNA damage, indicating the broad relevance of HRR to genotoxicity. Untreated 51D1 cells exhibit {approx}5-fold elevated chromosomal breaks, a 12-fold increased rate of hprt mutation, and 4- to 10-fold increased rates of gene amplification at the dhfr and CAD loci, respectively. These results explicitly show the quantitative importance of HHR in preventing these types genetic alterations, which are associated with carcinogenesis. Thus, HRR copes in an error-free manner with spontaneous DNA damage encountered during DNA replication, and Rad51D is essential for this fidelity.

  20. BHK cell lines with increased rates of gene amplification are hypersensitive to ultraviolet light

    Energy Technology Data Exchange (ETDEWEB)

    Giulotto, E.; Bertoni, L.; Attolini, C.; Rainaldi, G.; Anglana, M. (Dipartimento di Genetica e Microbiologia Adriano Buzzati-Traverso, Pavia (Italy))

    1991-04-15

    Four cell lines (MP1, -4, -5, -7), isolated from baby hamster kidney cells after simultaneous selection with N-(phosphonacetyl)-L-aspartate and methotrexate, have previously been shown to amplify their DNA at an increased rate. We now show that all four lines are hypersensitive to killing by UV light and mitomycin C. At high doses of UV light or mitomycin C, the MP lines survived less than 10% or less than 5% as well as parental cells, respectively. After UV irradiation, inhibition of DNA and RNA synthesis was greater in MP than in parental cells, and recovery was slower or absent. A 2- to 3.5-fold increase in the frequency of UV-induced sister chromatid exchange was also seen in the four cell lines. In MP5, unscheduled DNA replication after treatment with UV light was only approximately 70% as great as in parental cells and the other MP lines. In MP4 and MP7 cells S phase was elongated. Although their individual properties confirm that the four cell lines are independent, their common properties suggest a relationship between tolerance of DNA damage and gene amplification.

  1. The significance of cytogenetics for the study of karyotype evolution and taxonomy of water bugs (Heteroptera, Belostomatidae) native to Argentina

    Science.gov (United States)

    Gabriela, Chirino Mónica; Papeschi, Alba Graciela; Bressa, María José

    2013-01-01

    Abstract Male meiosis behaviour and heterochromatin characterization of three big water bug species were studied. Belostoma dentatum (Mayr, 1863), Belostoma elongatum Montandon, 1908 and Belostoma gestroi Montandon, 1903 possess 2n = 26 + X1X2Y (male). In these species, male meiosis is similar to that previously observed in Belostoma Latreille, 1807. In general, autosomal bivalents show a single chiasma terminally located and divide reductionally at anaphase I. On the other hand, sex chromosomes are achiasmatic, behave as univalents and segregate their chromatids equationally at anaphase I. The analysis of heterochromatin distribution and composition revealed a C-positive block at the terminal region of all autosomes in Belostoma dentatum, a C-positive block at the terminal region and C-positive interstitial dots on all autosomes in Belostoma elongatum, and a little C-positive band at the terminal region of autosomes in Belostoma gestroi. A C-positive band on one bivalent was DAPI negative/CMA3 positive in the three species. The CMA3-bright band, enriched in GC base pairs, was coincident with a NOR detected by FISH. The results obtained support the hypothesis that all species of Belostoma with multiple sex chromosome systems preserve NORs in autosomal bivalents. The karyotype analyses allow the cytogenetic characterization and identification of these species belonging to a difficult taxonomic group. Besides, the cytogenetic characterization will be useful in discussions about evolutionary trends of the genome organization and karyotype evolution in this genus. PMID:24260694

  2. Assembly of bipolar microtubule structures by passive cross-linkers and molecular motors

    Science.gov (United States)

    Johann, D.; Goswami, D.; Kruse, K.

    2016-06-01

    During cell division, sister chromatids are segregated by the mitotic spindle, a bipolar assembly of interdigitating antiparallel polar filaments called microtubules. The spindle contains the midzone, a stable region of overlapping antiparallel microtubules, that is essential for maintaining bipolarity. Although a lot is known about the molecular players involved, the mechanism underlying midzone formation and maintenance is still poorly understood. We study the interaction of polar filaments that are cross-linked by molecular motors moving directionally and by passive cross-linkers diffusing along microtubules. Using a particle-based stochastic model, we find that the interplay of motors and passive cross-linkers can generate a stable finite overlap between a pair of antiparallel polar filaments. We develop a mean-field theory to study this mechanism in detail and investigate the influence of steric interactions between motors and passive cross-linkers on the overlap dynamics. In the presence of interspecies steric interactions, passive cross-linkers mimic the behavior of molecular motors and stable finite overlaps are generated even for non-cross-linking motors. Finally, we develop a mean-field theory for a bundle of aligned polar filaments and show that they can self-organize into a spindlelike pattern. Our work suggests possible ways as to how cells can generate spindle midzones and control their extensions.

  3. Cytogenetic changes induced by the different types of drinking water in one HCC high incidence area of P. R of China

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A lot of epidemiological survey on the kinds of risk factors caused by the high incidence of Hepatocellular carcinoma (HCC) in Fusui county,P. R. Of China has been done,especially on relation ship between the different types of drinking water and the mortality of HCC. But the mechanism is no clear. In our study,we sampled the common type of drinking water (pond water,shallow well water,tap water) in Fusui county and did series of cytogenetic determinations such as Chromosomal aberration (CA),Micronuclei (MN) and Sister chromatid exchange (SCE). The changes of CA,MN and SCE related to types of drinking water were observed. There were linear correlation between the concentration of water sample and these changes. The results suggests that one of the reason for the high incidence of HCC in Fusui county may be the presence of mutagen and/or carcinogen existed in the drinking water. The dissimilarity of the different types of drinking water is due to different concentrations of mutagens and/or carcinogens. In brief, the results confirmed the theory of type of drinking water corresponding to incidence rate of HCC proposed by Delong Su on cytogenetics

  4. The perpetual movements of anaphase.

    Science.gov (United States)

    Maiato, Helder; Lince-Faria, Mariana

    2010-07-01

    One of the most extraordinary events in the lifetime of a cell is the coordinated separation of sister chromatids during cell division. This is truly the essence of the entire mitotic process and the reason for the most profound morphological changes in cytoskeleton and nuclear organization that a cell may ever experience. It all occurs within a very short time window known as "anaphase", as if the cell had spent the rest of its existence getting ready for this moment in an ultimate act of survival. And there is a good reason for this: no space for mistakes. Problems in the distribution of chromosomes during cell division have been correlated with aneuploidy, a common feature observed in cancers and several birth defects, and the main cause of spontaneous abortion in humans. In this paper, we critically review the mechanisms of anaphase chromosome motion that resisted the scrutiny of more than 100 years of research, as part of a tribute to the pioneering work of Miguel Mota.

  5. Single-stranded DNA oligomers stimulate error-prone alternative repair of DNA double-strand breaks through hijacking Ku protein.

    Science.gov (United States)

    Yuan, Ying; Britton, Sébastien; Delteil, Christine; Coates, Julia; Jackson, Stephen P; Barboule, Nadia; Frit, Philippe; Calsou, Patrick

    2015-12-01

    In humans, DNA double-strand breaks (DSBs) are repaired by two mutually-exclusive mechanisms, homologous recombination or end-joining. Among end-joining mechanisms, the main process is classical non-homologous end-joining (C-NHEJ) which relies on Ku binding to DNA ends and DNA Ligase IV (Lig4)-mediated ligation. Mostly under Ku- or Lig4-defective conditions, an alternative end-joining process (A-EJ) can operate and exhibits a trend toward microhomology usage at the break junction. Homologous recombination relies on an initial MRN-dependent nucleolytic degradation of one strand at DNA ends. This process, named DNA resection generates 3' single-stranded tails necessary for homologous pairing with the sister chromatid. While it is believed from the current literature that the balance between joining and recombination processes at DSBs ends is mainly dependent on the initiation of resection, it has also been shown that MRN activity can generate short single-stranded DNA oligonucleotides (ssO) that may also be implicated in repair regulation. Here, we evaluate the effect of ssO on end-joining at DSB sites both in vitro and in cells. We report that under both conditions, ssO inhibit C-NHEJ through binding to Ku and favor repair by the Lig4-independent microhomology-mediated A-EJ process. PMID:26350212

  6. Positive feedback promotes mitotic exit via the APC/C-Cdh1-separase-Cdc14 axis in budding yeast.

    Science.gov (United States)

    Hatano, Yuhki; Naoki, Koike; Suzuki, Asuka; Ushimaru, Takashi

    2016-10-01

    The mitotic inhibitor securin is degraded via the ubiquitin ligase anaphase-promoting complex/cyclosome (APC/C)-Cdc20 after anaphase onset. This triggers activation of the mitotic protease separase and thereby sister chromatid separation. However, only a proportion of securin molecules are degraded at metaphase-anaphase transition and the remaining molecules are still present in anaphase. The roles of securin and separase in late mitosis remain elusive. Here, we show that securin still inhibits separase to repress mitotic exit in anaphase in budding yeast. APC/C-Cdh1-mediated securin degradation at telophase further liberated separase, which promotes Cdc14 release and mitotic exit. Separase executed these events via its proteolytic action and that in the Cdc14 early release (FEAR) network. Cdc14 release further activated APC/C-Cdh1 in the manner of a positive feedback loop. Thus, the positive feedback promotes mitotic exit via the APC/C-Cdh1-separase-Cdc14 axis. This study shows the importance of the two-step degradation mode of securin and the role of separase in mitotic exit. PMID:27418100

  7. Use of a ring chromosome and pulsed-field gels to study recombinational repair

    International Nuclear Information System (INIS)

    In wild type yeast, it is known that x-ray induced DNA double-strand breaks (dsb) are repaired, leading to recovery of high molecular-weight molecules on gradients or pulsed-field gels. There is genetic evidence that some or all of this repair occurs via recombinational mechanisms involving sister-chromatid exchange (SCE) and (in diploids) inter-homologue recombination. However, this evidence is indirect and qualitative. The authors of this paper are attempting to use pulsed-field gels to detect and measure recombinational repair at the physical level in yeast strains with a circular homologue of Chr. III. The authors have previously used such strains to study meiotic recombination. The authors have shown that double-size circular molecules can be detected in log-phase haploid yeast cells carrying a ring chromosome, when such cells are exposed to x-rays and allowed time for subsequent repair. Large circular molecules will not enter our pulsed-field gels, but treatment of the DNA samples with radiation prior to running the gels will linearize a fraction of such molecules with a single dsb. Such linearized molecules will run as a band whose position indicates the size of the original unbroken circles

  8. Granuloma pouch assay for mutagenicity testing.

    Science.gov (United States)

    Maier, P

    1980-11-01

    The Granuloma Pouch Assay (GPA) is an animal model in which mutagenic and carcinogenic effects of a testcompound can be detected in rapidly dividing fibroblasts of a granulation tissue in adult male rats. Growth of this tissue was initiated with a small amount of croton oil at the inside wall of a subcutaneous air pouch on the back of the animals. The test compound can be injected either into the pouch (local) or administered by systemic routes. Alkali labile DNA-lesions, chromosome aberrations, sister chromatid exchanges, point mutations and tumor development in situ were determined. The comparison of mutation frequencies after local and systemic administration of testcompounds, provide an estimation of the pharmacokinetic characteristics and the mutagenic potency of the chemical. The local application route allows the detection of locally active mutagens and of compounds which require activation by P-448 dependent mono-oxygenases. Liver mediated proximate metabolites are detectable when they are transformed into ultimate carcinogens in extrahepatic cells whereas chemicals with a strong organ specific activity are not. PMID:7235991

  9. Occupational exposure to antineoplastic agents induces a high level of chromosome damage. Lack of an effect of GST polymorphisms

    International Nuclear Information System (INIS)

    The aim of our study was to investigate whether occupational exposure to antineoplastic drugs (AND) resulted in genetic damage, possibly indicative of adverse health effects in the long term. We performed a chromosomal aberrations (CA) analysis in peripheral blood lymphocytes (PBL) of a group of 76 trained nurses occupationally exposed to AND. Furthermore, we analysed whether genetic polymorphisms in four metabolic genes of the glutathione S-transferase (GST) family involved in antineoplastic drugs detoxification (GSTM1, GSTT1, GSTP1, GSTA1) had any effect on the yield of chromosomal aberrations in nurses exposed to antineoplastic agents. The exposed group showed a very significant increase of genetic damage (p < 0.0001) potentially indicative of an increased risk of cancer. Unexpectedly, besides the elevated level of chromatid-type aberrations usually related to exposure to chemical agents, we found also severe chromosome damages such as chromosome deletions and dicentric chromosomes, usually related to radiation exposure. No significant association was detected between all GSTs genotypes and chromosome damage. In conclusion, our data show how the occupational exposure to AND is associated to a potential cancer risk, suggesting that current prevention methods do not completely eliminate opportunities for exposure and supporting the need to improve the actual safety practices

  10. In vitro evaluation of the genotoxicity of a family of novel MeO-PEG-poly(D,L-lactic-co-glycolic acid)-PEG-OMe triblock copolymer and PLGA nanoparticles

    International Nuclear Information System (INIS)

    Despite the booming development of nanoparticle materials for pharmaceutical applications, studies on their genotoxicity are few. In our previous efforts to develop an intravenous nanoparticle material, a family of novel monomethoxy(polyethylene glycol)-poly(D,L-lactic-co-glycolic acid)-monomethoxy (PELGE) polymers was synthesized. The cytotoxicity and genotoxicity of nine kinds of selected blank PELGE and PLGA (poly(D,L-lactic and glycolic acid)) nanoparticles were evaluated using methyl thiazolyl tetrazolium (MTT), micronucleus (MN) and sister chromatid exchange (SCE) assays with or without the addition of a metabolic activation system (S9 mix), using Chinese hamster ovary (CHO) cells. The cytotoxicity of nanoparticles exhibited a dose-dependent response, with a concentration of 5 mg ml-1 being the turning point. The frequencies of MN observed in samples treated with various nanoparticles were not statistically different from those seen in the negative controls in the presence or absence of the S9 mix. Also, no cell cycle delay was observed. The numbers of SCE per cell observed in samples treated with five kinds of PELGE nanoparticles were significantly greater than those found in the negative controls with or without the S9 mix. The discrepancies found in the two assays suggest that the five kinds of nanoparticles may produce only a weakly clastogenic response.

  11. Biomarkers of genetic damage in human populations exposed to pesticides

    International Nuclear Information System (INIS)

    The effect of pesticides on human, animal and environmental health has been cause of concern in the scientific community for a long time. Numerous studies have reported that pesticides are not harmless and that their use can lead to harmful biological effects in the medium and long term, in exposed human and animals, and their offspring. The importance of early detection of genetic damage is that it allows us to take the necessary measures to reduce or eliminate the exposure to the deleterious agent when damage is still reversible, and thus to prevent and to diminish the risk of developing tumors or other alterations. In this paper we reviewed the main concepts in the field, the usefulness of genotoxicity studies and we compiled studies performed during the last twenty years on genetic monitoring of people occupationally exposed to pesticides. we think that genotoxicity tests, including that include chromosomal aberrations, micronucleus, sister chromatid exchanges and comet assays, should be considered as essential tools in the implementation of complete medical supervision for people exposed to potential environmental pollutants, particularly for those living in the same place as others who were others have already developed some type of malignancy. This action is particularly important at early stages to prevent the occurrence of tumors, especially from environmental origins.

  12. Identification of Putative Mek1 Substrates during Meiosis in Saccharomyces cerevisiae Using Quantitative Phosphoproteomics.

    Directory of Open Access Journals (Sweden)

    Raymond T Suhandynata

    Full Text Available Meiotic recombination plays a key role in sexual reproduction as it generates crossovers that, in combination with sister chromatid cohesion, physically connect homologous chromosomes, thereby promoting their proper segregation at the first meiotic division. Meiotic recombination is initiated by programmed double strand breaks (DSBs catalyzed by the evolutionarily conserved, topoisomerase-like protein Spo11. Repair of these DSBs is highly regulated to create crossovers between homologs that are distributed throughout the genome. This repair requires the presence of the mitotic recombinase, Rad51, as well as the strand exchange activity of the meiosis-specific recombinase, Dmc1. A key regulator of meiotic DSB repair in Saccharomyces cerevisiae is the meiosis-specific kinase Mek1, which promotes interhomolog strand invasion and is required for the meiotic recombination checkpoint and the crossover/noncrossover decision. Understanding how Mek1 regulates meiotic recombination requires the identification of its substrates. Towards that end, an unbiased phosphoproteomic approach utilizing Stable Isotope Labeling by Amino Acids in Cells (SILAC was utilized to generate a list of potential Mek1 substrates, as well as proteins containing consensus phosphorylation sites for cyclin-dependent kinase, the checkpoint kinases, Mec1/Tel1, and the polo-like kinase, Cdc5. These experiments represent the first global phosphoproteomic dataset for proteins in meiotic budding yeast.

  13. The Change of Microtubule Cytoskeleton in the Stem-Tip Cells of Sugarcane during Mitosis%甘蔗茎尖细胞有丝分裂过程中微管骨架的变化

    Institute of Scientific and Technical Information of China (English)

    李志刚; 赵洪波; 李素丽; 杨丽涛; 李杨瑞

    2008-01-01

    In order to understand the microtubule change of monoeotyls stem-tip during mitosis,the arrangement,transformation of microtubule array and its relation with chromosome movement during mitosis were studied with freezing microtome,indirect immunofluorescence,DAPI staining and fluorescence microscopy.The results showed that nueleolus was intact when the cortical miemtubules formed;cortical mierotubulos were changed into phramoplast microtubule bands at mitosis prophase.When phramoplast microtubule came into being,nuclear membrane was ruptured and chromosome was arranged at the position of cell plate;subsequently,phramoplast microtubules were changed into phragmoplast mierotubules,phramoplast mierotubules were shortening and microtubules on the sides of cell plate were increasing gradually,during this course sister chromatid was separated by microtubules at cell plate and tract to the two poles,forming phragmoplast microtubules.Then the nucleolus of two daughter cells formed and separated in the end with the increase of cells numbers.Therefore,cell division orientation could be judged from the arrangement of cell microtubules in different periods in order to understand its growth status.

  14. Relative biological effectiveness of tritiated water on human chromosomes of lymphocytes and bone marrow cells

    International Nuclear Information System (INIS)

    One of the major toxic effluent from nuclear power industries is tritiated water (HTO), which is released into the environment in large quantities. Low dose radiation effects and dose rate effects of HTO on human lymphocytes and bone marrow cells are not well studied. The present study was performed to investigate dose-response relationship for chromosome aberration frequencies in the human lymphocytes and bone marrow cells, by HTO in-vitro exposure at low dose ranges of 0.1 to 1 Gy. Go lymphocytes and bone marrow cells were incubated for 10 - 150 minutes with HTO at 2 cGy/min. Also 60Co γ and 137Cs γ rays were used as controls. Dicentric chromosomes were scored in 1,000 to 2,000 cells of each experimental series. The RBE values of HTO at low dose range for the induction of dicentric chromosomes and chromatid type aberrations were 2.7 in lymphocytes and approximately 3.8 in bone marrow cells with respect to 60Co γ ray, respectively. Also lymphocytes were chronically exposed to HTO for 24 to 72 hrs at lower dose rates (0.2 and 0.05 cGy/min). The yields of dicentrics and rings decreased with the reduction in the dose rate of HTO, presenting a clear dose rate effects of HTO. These results provide an useful information for the assessment for health risk in humans exposed to low concentration level to HTO. (author)

  15. Identification of Putative Mek1 Substrates during Meiosis in Saccharomyces cerevisiae Using Quantitative Phosphoproteomics

    Science.gov (United States)

    Suhandynata, Raymond T.; Wan, Lihong; Zhou, Huilin; Hollingsworth, Nancy M.

    2016-01-01

    Meiotic recombination plays a key role in sexual reproduction as it generates crossovers that, in combination with sister chromatid cohesion, physically connect homologous chromosomes, thereby promoting their proper segregation at the first meiotic division. Meiotic recombination is initiated by programmed double strand breaks (DSBs) catalyzed by the evolutionarily conserved, topoisomerase-like protein Spo11. Repair of these DSBs is highly regulated to create crossovers between homologs that are distributed throughout the genome. This repair requires the presence of the mitotic recombinase, Rad51, as well as the strand exchange activity of the meiosis-specific recombinase, Dmc1. A key regulator of meiotic DSB repair in Saccharomyces cerevisiae is the meiosis-specific kinase Mek1, which promotes interhomolog strand invasion and is required for the meiotic recombination checkpoint and the crossover/noncrossover decision. Understanding how Mek1 regulates meiotic recombination requires the identification of its substrates. Towards that end, an unbiased phosphoproteomic approach utilizing Stable Isotope Labeling by Amino Acids in Cells (SILAC) was utilized to generate a list of potential Mek1 substrates, as well as proteins containing consensus phosphorylation sites for cyclin-dependent kinase, the checkpoint kinases, Mec1/Tel1, and the polo-like kinase, Cdc5. These experiments represent the first global phosphoproteomic dataset for proteins in meiotic budding yeast. PMID:27214570

  16. WRNIP1 functions upstream of DNA polymerase η in the UV-induced DNA damage response

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, Akari, E-mail: akari_yo@stu.musashino-u.ac.jp [Molecular Cell Biology Laboratory, Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, 1-1-20 Shinmachi, Nishitokyo-shi, Tokyo 202-8585 (Japan); Kobayashi, Yume [Molecular Cell Biology Laboratory, Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, 1-1-20 Shinmachi, Nishitokyo-shi, Tokyo 202-8585 (Japan); Tada, Shusuke [Department of Medical Biochemistry, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba 274-8510 (Japan); Seki, Masayuki [Department of Biochemistry, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai-shi, Miyagi 981-8558 (Japan); Enomoto, Takemi [Molecular Cell Biology Laboratory, Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, 1-1-20 Shinmachi, Nishitokyo-shi, Tokyo 202-8585 (Japan)

    2014-09-12

    Highlights: • The UV sensitivity of POLH{sup −/−} cells was suppressed by disruption of WRNIP1. • In WRNIP1{sup −/−/−}/POLH{sup −/−} cells, mutation frequencies and SCE after irradiation reduced. • WRNIP1 defect recovered rate of fork progression after irradiation in POLH{sup −/−} cells. • WRNIP1 functions upstream of Polη in the translesion DNA synthesis pathway. - Abstract: WRNIP1 (WRN-interacting protein 1) was first identified as a factor that interacts with WRN, the protein that is defective in Werner syndrome (WS). WRNIP1 associates with DNA polymerase η (Polη), but the biological significance of this interaction remains unknown. In this study, we analyzed the functional interaction between WRNIP1 and Polη by generating knockouts of both genes in DT40 chicken cells. Disruption of WRNIP1 in Polη-disrupted (POLH{sup −/−}) cells suppressed the phenotypes associated with the loss of Polη: sensitivity to ultraviolet light (UV), delayed repair of cyclobutane pyrimidine dimers (CPD), elevated frequency of mutation, elevated levels of UV-induced sister chromatid exchange (SCE), and reduced rate of fork progression after UV irradiation. These results suggest that WRNIP1 functions upstream of Polη in the response to UV irradiation.

  17. Determination of n+1 Gamete Transmission Rate of Trisomics and Location of Gene Controlling 2n Gamete Formation in Chinese Cabbage (Brassica rapa)

    Institute of Scientific and Technical Information of China (English)

    Cheng-He Zhang; Xiao-Feng Li; Shu-Xing Shen; He Yuan; Shu-Xin Xuan

    2009-01-01

    A set of trisomics of Chinese cabbage was used for determining the n+1 gamete transmission rate and locating the gene controlling 2n gamete formation on the corresponding chromosome. The results showed that the transmission rates of extra chromosomes in different trisomica varied from 0% to 15.38% by male gametes and from 0% to 17.39% by female gametes. Of the nine F2 populations derived from the hybridizations between each triaomic and Bp058 (2n gamete material), only Tri-4×Bp058 showed that the segregation ratio of plants without 2n gamete formation to plants with 2n gamete formation was 10.38:1, which fitted the expected segregation ratio of the trisomics (AAa) based on the 7.37% of n+1 gamete transmission through female and 5.88% through male. In other populations the segregation ratios varied from 2.48:1 to 3.72:1, which fitted the expected 3:1 segregation ratio of the bisomice (Aa). These results suggested that the gene controlling 2n gamete formation in Chinese cabbage Bp058 was located on chromosome 4. Further trisomic analysis based on the chromosome segregation and the incomplete stochastic chromatid segregation indicated that the gene locus was tightly linked to the centromere.

  18. SMC1B is present in mammalian somatic cells and interacts with mitotic cohesin proteins.

    Science.gov (United States)

    Mannini, Linda; Cucco, Francesco; Quarantotti, Valentina; Amato, Clelia; Tinti, Mara; Tana, Luigi; Frattini, Annalisa; Delia, Domenico; Krantz, Ian D; Jessberger, Rolf; Musio, Antonio

    2015-01-01

    Cohesin is an evolutionarily conserved protein complex that plays a role in many biological processes: it ensures faithful chromosome segregation, regulates gene expression and preserves genome stability. In mammalian cells, the mitotic cohesin complex consists of two structural maintenance of chromosome proteins, SMC1A and SMC3, the kleisin protein RAD21 and a fourth subunit either STAG1 or STAG2. Meiotic paralogs in mammals were reported for SMC1A, RAD21 and STAG1/STAG2 and are called SMC1B, REC8 and STAG3 respectively. It is believed that SMC1B is only a meiotic-specific cohesin member, required for sister chromatid pairing and for preventing telomere shortening. Here we show that SMC1B is also expressed in somatic mammalian cells and is a member of a mitotic cohesin complex. In addition, SMC1B safeguards genome stability following irradiation whereas its ablation has no effect on chromosome segregation. Finally, unexpectedly SMC1B depletion impairs gene transcription, particularly at genes mapping to clusters such as HOX and PCDHB. Genome-wide analyses show that cluster genes changing in expression are enriched for cohesin-SMC1B binding.

  19. Comparison of effects of six tritiated compounds on chromosomal aberrations in human lymphocytes in vitro and dose-response relationships

    International Nuclear Information System (INIS)

    The effects of six tritiated compounds on chromosomal aberrations were compared in cultured human lymphocytes, and dose-response relationships were analysed. According to the efficiency of inducing aberrations, these compounds could be arranged in decreasing order as follows: 3H-TdR > 3H-UdR > 3H-lysine > 3H-thymine > 3H-leucine > HTO, when the dose-response relationship was expressed in radioactivity/ml of the medium. This order is determined mainly by the radioactivities incorporated into the nuclei or the cells. However, when compared in terms of the dose absorbed by the nuclei or the cells, the differences among various compounds would be much more reduced. The data of aberration yields for different tritium activities (or absorbed dsoes) were fitted satisfactorily to the linear-quadratic dose-response equation Y = A + BX + CX2. The yields of chromatid-type and chromosometype aberrations induced by various tritiated compounds were quite different. These differences are related to the metabolism of the compounds

  20. Genotoxic evaluation of ammonium inactivated aflatoxin B1 in mice fed with contaminated corn.

    Science.gov (United States)

    Márquez-Márquez, R; Madrigal-Bujaidar, E; Tejada de Hernández, I

    1993-03-01

    Aflatoxin B1 (AFB1) is a major contaminant in different agricultural products including maize. In an attempt to reduce this problem and the hazards to human health, an AFB1 inactivating system with ammonia has been developed. In this work we evaluated the efficiency of the system in mice using micronucleus (MN) and sister chromatid exchange (SCE) analysis. Four groups of animals were fed during 8 weeks with a special diet mainly composed of maize: (1) uncontaminated; (2) uncontaminated/inactivated; (3) contaminated/inactivated; and (4) contaminated. We evaluated MN at weekly intervals in peripheral blood, and in weeks 4 and 8 SCE frequencies were quantified in bone marrow cells. The results showed that animals fed with AFB1 contaminated/inactivated maize had a 45% lower level of induced cytogenetic damage than those animals fed with AFB1 contaminated, but not inactivated maize. A residual amount of AFB1 after the inactivating treatment and the reconversion back to AFB1 in the organism may account for the remaining increased levels of SCE and MN.

  1. Genotoxicity of aflatoxin B1 and its ammonium derivatives.

    Science.gov (United States)

    Márquez Márquez, R; Tejada de Hernandez, I; Madrigal Bujaidar, E

    1995-01-01

    Aflatoxin (AF) B1 is a main contaminant in diverse agricultural products. In an attempt to reduce this problem and the hazards to human health, an AFB1 inactivating system with ammonia has been developed. In this work we evaluated the efficiency of the system in mice using micronucleus (MN) and sister chromatid exchange (SCE) analysis. Four groups of animals were fed for 8 weeks with a special diet mainly composed of maize: (1) uncontaminated; (2) uncontaminated/inactivated; (3) contaminated/inactivated; and (4) contaminated. We evaluated MN at weekly intervals in peripheral blood, and in weeks 4 and 8 SCE frequencies were quantified in bone marrow cells. The results shows that animals fed with AFB1 contaminated/inactivated maize had a 45% lower level of induced cytogenetic damage than those animals fed with AFB1 contaminated but not inactivated maize. A residual amount of AFB1 after the inactivating treatment and reconversion back to AFB1 in the organism may account for the remaining increased levels of SCE and MN.

  2. High-resolution mapping of YACs and the single-copy gene Hs1(pro-1) on Beta vulgaris chromosomes by multi-colour fluorescence in situ hybridization.

    Science.gov (United States)

    Desel, C; Jung, C; Cai, D; Kleine, M; Schmidt, T

    2001-01-01

    Fluorescence in situ hybridization (FISH) is a powerful approach for physical mapping of DNA sequences along plant chromosomes. Nematode-resistant sugar beets (Beta vulgaris) carrying a Beta procumbens translocation were investigated by FISH with two differentially labelled YACs originating from the translocation. At mitotic metaphases, the translocation was identified with both YACs in the terminal region on a pair of chromosomes. Meiotic chromosomes, representing a far more extended hybridization target, were used to determine the orientation of YACs with respect to chromosomal domains in combination with chromosomal landmark probes for telomeres and centromeres. The in situ detection of plant single-copy sequences is technically difficult, and the wild beet translocation was used to explore the potential resolution of the FISH approach and to introduce the chromosomal mapping of single-copy genes into genome analysis of Beta species. An internal fragment of the nematode resistance gene Hs1(pro-1), 684 bp long, was detected on both chromatids of different Beta chromosomes and represents one of the shortest unique DNA sequences localized on mitotic plant chromosomes so far. Comparative chromosomal mapping of the 684 bp Hs1(pro-1) probe in the translocation line, a monosomic addition line and in B. procumbens revealed the origin of the wild beet translocation leading to nematode-resistant sugar beets.

  3. Functional interplay between SA1 and TRF1 in telomeric DNA binding and DNA-DNA pairing.

    Science.gov (United States)

    Lin, Jiangguo; Countryman, Preston; Chen, Haijiang; Pan, Hai; Fan, Yanlin; Jiang, Yunyun; Kaur, Parminder; Miao, Wang; Gurgel, Gisele; You, Changjiang; Piehler, Jacob; Kad, Neil M; Riehn, Robert; Opresko, Patricia L; Smith, Susan; Tao, Yizhi Jane; Wang, Hong

    2016-07-27

    Proper chromosome alignment and segregation during mitosis depend on cohesion between sister chromatids. Cohesion is thought to occur through the entrapment of DNA within the tripartite ring (Smc1, Smc3 and Rad21) with enforcement from a fourth subunit (SA1/SA2). Surprisingly, cohesin rings do not play a major role in sister telomere cohesion. Instead, this role is replaced by SA1 and telomere binding proteins (TRF1 and TIN2). Neither the DNA binding property of SA1 nor this unique telomere cohesion mechanism is understood. Here, using single-molecule fluorescence imaging, we discover that SA1 displays two-state binding on DNA: searching by one-dimensional (1D) free diffusion versus recognition through subdiffusive sliding at telomeric regions. The AT-hook motif in SA1 plays dual roles in modulating non-specific DNA binding and subdiffusive dynamics over telomeric regions. TRF1 tethers SA1 within telomeric regions that SA1 transiently interacts with. SA1 and TRF1 together form longer DNA-DNA pairing tracts than with TRF1 alone, as revealed by atomic force microscopy imaging. These results suggest that at telomeres cohesion relies on the molecular interplay between TRF1 and SA1 to promote DNA-DNA pairing, while along chromosomal arms the core cohesin assembly might also depend on SA1 1D diffusion on DNA and sequence-specific DNA binding. PMID:27298259

  4. The Clathrin-dependent Spindle Proteome.

    Science.gov (United States)

    Rao, Sushma R; Flores-Rodriguez, Neftali; Page, Scott L; Wong, Chin; Robinson, Phillip J; Chircop, Megan

    2016-08-01

    The mitotic spindle is required for chromosome congression and subsequent equal segregation of sister chromatids. These processes involve a complex network of signaling molecules located at the spindle. The endocytic protein, clathrin, has a "moonlighting" role during mitosis, whereby it stabilizes the mitotic spindle. The signaling pathways that clathrin participates in to achieve mitotic spindle stability are unknown. Here, we assessed the mitotic spindle proteome and phosphoproteome in clathrin-depleted cells using quantitative MS/MS (data are available via ProteomeXchange with identifier PXD001603). We report a spindle proteome that consists of 3046 proteins and a spindle phosphoproteome consisting of 5157 phosphosites in 1641 phosphoproteins. Of these, 2908 (95.4%) proteins and 1636 (99.7%) phosphoproteins are known or predicted spindle-associated proteins. Clathrin-depletion from spindles resulted in dysregulation of 121 proteins and perturbed signaling to 47 phosphosites. The majority of these proteins increased in mitotic spindle abundance and six of these were validated by immunofluorescence microscopy. Functional pathway analysis confirmed the reported role of clathrin in mitotic spindle stabilization for chromosome alignment and highlighted possible new mechanisms of clathrin action. The data also revealed a novel second mitotic role for clathrin in bipolar spindle formation. PMID:27174698

  5. Characterization of the NTPR and BD1 interacting domains of the human PICH-BEND3 complex.

    Science.gov (United States)

    Pitchai, Ganesha P; Hickson, Ian D; Streicher, Werner; Montoya, Guillermo; Mesa, Pablo

    2016-08-01

    Chromosome integrity depends on DNA structure-specific processing complexes that resolve DNA entanglement between sister chromatids. If left unresolved, these entanglements can generate either chromatin bridging or ultrafine DNA bridging in the anaphase of mitosis. These bridge structures are defined by the presence of the PICH protein, which interacts with the BEND3 protein in mitosis. To obtain structural insights into PICH-BEND3 complex formation at the atomic level, their respective NTPR and BD1 domains were cloned, overexpressed and crystallized using 1.56 M ammonium sulfate as a precipitant at pH 7.0. The protein complex readily formed large hexagonal crystals belonging to space group P6122, with unit-cell parameters a = b = 47.28, c = 431.58 Å and with one heterodimer in the asymmetric unit. A complete multiwavelength anomalous dispersion (MAD) data set extending to 2.2 Å resolution was collected from a selenomethionine-labelled crystal at the Swiss Light Source. PMID:27487930

  6. Gene-exposure interaction in occupational and environmental epidemiology: Results from an ongoing study

    Directory of Open Access Journals (Sweden)

    Elin H. Kure

    2009-10-01

    Full Text Available  ABSTRACTA tissue bank is established in our department on a total of 659 persons whereof 341 are included in theNordic data base on somatic chromosome damage in humans. Genotyping of susceptibility genes relevantto the exposures of the cohort is an ongoing undertaking in our laboratory. GST's and mEH have beengenotyped for 80 persons so far, CYP's for 20 persons. When the mean number of chromatide breaks and ofcells with aberrations were related to genotypes no statistical difference could be observed between thegenotypes for either parameter. No difference in cytogenetic damage between exposed and referents orbetween smokers and non-smokers were identified for the two separate occupational studies these 80persons represent. The results of the various cytogenetic endpoints were trichotomized and compared to thegenotype distribution. Although not statistically significant, the observed trend with higher percentage ofpersons with polymorphic GSTp1 in particular, but also for GSTq1 and mEH (exon 4 in the group withhigh frequency of chromosome aberrations will be interesting to follow. For further follow-up studies, anested case-control study within the cohort would give a more rapid and less expensive approach thananalysing each study separately as a traditional case-control study. As high frequency of chromosomaldamage is associated with cancer development, the hypothesis to be tested would be whether genetic polymorphismsfor the most appropriate susceptibility genes could be an explanatory factor for this association.

  7. Phosphorylation of microtubule-binding protein Hec1 by mitotic kinase Aurora B specifies spindle checkpoint kinase Mps1 signaling at the kinetochore.

    Science.gov (United States)

    Zhu, Tongge; Dou, Zhen; Qin, Bo; Jin, Changjiang; Wang, Xinghui; Xu, Leilei; Wang, Zhaoyang; Zhu, Lijuan; Liu, Fusheng; Gao, Xinjiao; Ke, Yuwen; Wang, Zhiyong; Aikhionbare, Felix; Fu, Chuanhai; Ding, Xia; Yao, Xuebiao

    2013-12-13

    The spindle assembly checkpoint (SAC) is a quality control device to ensure accurate chromosome attachment to spindle microtubule for equal segregation of sister chromatid. Aurora B is essential for SAC function by sensing chromosome bi-orientation via spatial regulation of kinetochore substrates. However, it has remained elusive as to how Aurora B couples kinetochore-microtubule attachment to SAC signaling. Here, we show that Hec1 interacts with Mps1 and specifies its kinetochore localization via its calponin homology (CH) domain and N-terminal 80 amino acids. Interestingly, phosphorylation of the Hec1 by Aurora B weakens its interaction with microtubules but promotes Hec1 binding to Mps1. Significantly, the temporal regulation of Hec1 phosphorylation orchestrates kinetochore-microtubule attachment and Mps1 loading to the kinetochore. Persistent expression of phosphomimetic Hec1 mutant induces a hyperactivation of SAC, suggesting that phosphorylation-elicited Hec1 conformational change is used as a switch to orchestrate SAC activation to concurrent destabilization of aberrant kinetochore attachment. Taken together, these results define a novel role for Aurora B-Hec1-Mps1 signaling axis in governing accurate chromosome segregation in mitosis.

  8. Cohesin SMC1beta protects telomeres in meiocytes.

    Science.gov (United States)

    Adelfalk, Caroline; Janschek, Johannes; Revenkova, Ekaterina; Blei, Cornelia; Liebe, Bodo; Göb, Eva; Alsheimer, Manfred; Benavente, Ricardo; de Boer, Esther; Novak, Ivana; Höög, Christer; Scherthan, Harry; Jessberger, Rolf

    2009-10-19

    Meiosis-specific mammalian cohesin SMC1beta is required for complete sister chromatid cohesion and proper axes/loop structure of axial elements (AEs) and synaptonemal complexes (SCs). During prophase I, telomeres attach to the nuclear envelope (NE), but in Smc1beta(-/-) meiocytes, one fifth of their telomeres fail to attach. This study reveals that SMC1beta serves a specific role at telomeres, which is independent of its role in determining AE/SC length and loop extension. SMC1beta is necessary to prevent telomere shortening, and SMC3, present in all known cohesin complexes, properly localizes to telomeres only if SMC1beta is present. Very prominently, telomeres in Smc1beta(-/-) spermatocytes and oocytes loose their structural integrity and suffer a range of abnormalities. These include disconnection from SCs and formation of large telomeric protein-DNA extensions, extended telomere bridges between SCs, ring-like chromosomes, intrachromosomal telomeric repeats, and a reduction of SUN1 foci in the NE. We suggest that a telomere structure protected from DNA rearrangements depends on SMC1beta. PMID:19841137

  9. Rapid transcriptional pulsing dynamics of high expressing retroviral transgenes in embryonic stem cells.

    Directory of Open Access Journals (Sweden)

    Mandy Y M Lo

    Full Text Available Single cell imaging studies suggest that transcription is not continuous and occurs as discrete pulses of gene activity. To study mechanisms by which retroviral transgenes can transcribe to high levels, we used the MS2 system to visualize transcriptional dynamics of high expressing proviral integration sites in embryonic stem (ES cells. We established two ES cell lines each bearing a single copy, self-inactivating retroviral vector with a strong ubiquitous human EF1α gene promoter directing expression of mRFP fused to an MS2-stem-loop array. Transfection of MS2-EGFP generated EGFP focal dots bound to the mRFP-MS2 stem loop mRNA. These transcription foci colocalized with the transgene integration site detected by immunoFISH. Live tracking of single cells for 20 minutes detected EGFP focal dots that displayed frequent and rapid fluctuations in transcription over periods as short as 25 seconds. Similarly rapid fluctuations were detected from focal doublet signals that colocalized with replicated proviral integration sites by immunoFISH, consistent with transcriptional pulses from sister chromatids. We concluded that retroviral transgenes experience rapid transcriptional pulses in clonal ES cell lines that exhibit high level expression. These events are directed by a constitutive housekeeping gene promoter and may provide precedence for rapid transcriptional pulsing at endogenous genes in mammalian stem cells.

  10. In vivo synergistic cytogenetic effects of aminophylline on lymphocyte cultures from patients with lung cancer undergoing chemotherapy

    International Nuclear Information System (INIS)

    Highlights: ► SCEs in vivo, a possible predictor of tumor chemoresponse. ► In vivo exposure to combined treatment, applying the SCE assay. ► Aminophylline enhances DNA instability induced by chemotherapy in vivo. ► In vivo synergistic effect of Aminophylline with the chemotherapeutic agents. - Abstract: Background: The anti-cancer and cytogenetic effects of aminophylline (AM) have been demonstrated in several clinical trials. The aim of the present study was to investigate the in vivo cytogenetic effects of AM in newly diagnosed patients with small cell (SCLC) and non-small cell lung cancer (NSCLC), receiving chemotherapy for the first time. Methods: Sister chromatid exchanges (SCEs) and proliferation rate index (PRI) were evaluated in peripheral blood lymphocyte cultures from six patients with SCLC and six patients with NSCLC after the in vitro addition of AM and after the in vivo administration of AM in patients receiving chemotherapy. Results: The in vitro addition of AM significantly increased SCEs only in SCLC patients (p 0.05). Conclusions: These observations suggest that AM enhances the results of concurrently administered chemotherapy by synergistically increasing its cytogenetic effects in patients with lung cancer

  11. Increased Chromosomal Radiosensitivity in Women Carrying BRCA1/BRCA2 Mutations Assessed With the G2 Assay

    International Nuclear Information System (INIS)

    Purpose: Several in vitro studies suggest that BRCA1 and BRCA2 mutation carriers present increased sensitivity to ionizing radiation. Different assays for the assessment of deoxyribonucleic acid double-strand break repair capacity have been used, but results are rather inconsistent. Given the concerns about the possible risks of breast screening with mammography in mutation carrier women and the potentially damaging effects of radiotherapy, the purpose of this study was to further investigate the radiosensitivity of this population. Methods and Materials: The G2 chromosomal radiosensitivity assay was used to assess chromosomal breaks in lymphocyte cultures after exposure to 1 Gy. A group of familiar breast cancer patients carrying a mutation in the BRCA1 or BRCA2 gene (n = 15) and a group of healthy mutation carriers (n = 5) were investigated and compared with a reference group of healthy women carrying no mutation (n = 21). Results: BRCA1 and BRCA2 mutation carriers had a significantly higher number of mean chromatid breaks per cell (p = 0.006) and a higher maximum number of breaks (p = 0.0001) as compared with their matched controls. Both healthy carriers and carriers with a cancer history were more radiosensitive than controls (p = 0.002 and p = 0.025, respectively). Age was not associated with increased radiosensitivity (p = 0.868). Conclusions: Our results indicate that BRCA1 and BRCA2 mutation carriers show enhanced radiosensitivity, presumably because of the involvement of the BRCA genes in deoxyribonucleic acid repair and cell cycle control mechanisms.

  12. Radiomimetic Effect of Oncogenic and 'Non-Oncogenic' Human and Simian Adenoviruses

    International Nuclear Information System (INIS)

    The capacity of human (AD2, 4, 7, 12, 16, 18, 31) and simian (SA7, SV20) adenoviruses to induce chromosome aberrations and to affect the proliferative capacity and cloning efficiency was examined using permissive (AV-3, HEp-2, CV-1 cell strains) and non-permissive (BHK-21, primary Syrian hamster cultures) cell systems. The comparative study revealed (1). that genetically abnormal cells are only induced when the viral replication cycle is incomplete or when cells are infected with defective or experimentally (UV-irradiation, hydroxylamine treatment) impaired viruses; (2) that the chromosome damaging capacity of one virus is comparable to that of about 2 rads of X-ray; and (3) that the viral genome, which can survive in the host cells, represents a self- replicating mutagenic agent capable of continuous induction of new cell mutants. Frequency of cells with chromosome aberrations, incidence of chromatid breaks per cell, loss of cloning efficiency and the formation of virus-induced T(tumour)-antigen, which is coded for by the parental viral DNA molecule but is apparently not a part of the viral coat, depend on the viral dose. The chromosome damaging factors) seem not to reside in the virus particle but appears to be a viral product(s) from which transcription occurs in the early stages of the viral replicative cycle. It is suggested that viruses might represent an important etiologic factor in the mutagenesis of higher organisms. (author)

  13. Human DNA repair and recombination genes

    International Nuclear Information System (INIS)

    Several genes involved in mammalian DNA repair pathways were identified by complementation analysis and chromosomal mapping based on hybrid cells. Eight complementation groups of rodent mutants defective in the repair of uv radiation damage are now identified. At least seven of these genes are probably essential for repair and at least six of them control the incision step. The many genes required for repair of DNA cross-linking damage show overlap with those involved in the repair of uv damage, but some of these genes appear to be unique for cross-link repair. Two genes residing on human chromosome 19 were cloned from genomic transformants using a cosmid vector, and near full-length cDNA clones of each gene were isolated and sequenced. Gene ERCC2 efficiently corrects the defect in CHO UV5, a nucleotide excision repair mutant. Gene XRCC1 normalizes repair of strand breaks and the excessive sister chromatid exchange in CHO mutant EM9. ERCC2 shows a remarkable /approximately/52% overall homology at both the amino acid and nucleotide levels with the yeast RAD3 gene. Evidence based on mutation induction frequencies suggests that ERCC2, like RAD3, might also be an essential gene for viability. 100 refs., 4 tabs

  14. Telomere length as a quantitative trait: genome-wide survey and genetic mapping of telomere length-control genes in yeast.

    Directory of Open Access Journals (Sweden)

    Tonibelle Gatbonton

    2006-03-01

    Full Text Available Telomere length-variation in deletion strains of Saccharomyces cerevisiae was used to identify genes and pathways that regulate telomere length. We found 72 genes that when deleted confer short telomeres, and 80 genes that confer long telomeres relative to those of wild-type yeast. Among identified genes, 88 have not been previously implicated in telomere length control. Genes that regulate telomere length span a variety of functions that can be broadly separated into telomerase-dependent and telomerase-independent pathways. We also found 39 genes that have an important role in telomere maintenance or cell proliferation in the absence of telomerase, including genes that participate in deoxyribonucleotide biosynthesis, sister chromatid cohesion, and vacuolar protein sorting. Given the large number of loci identified, we investigated telomere lengths in 13 wild yeast strains and found substantial natural variation in telomere length among the isolates. Furthermore, we crossed a wild isolate to a laboratory strain and analyzed telomere length in 122 progeny. Genome-wide linkage analysis among these segregants revealed two loci that account for 30%-35% of telomere length-variation between the strains. These findings support a general model of telomere length-variation in outbred populations that results from polymorphisms at a large number of loci. Furthermore, our results laid the foundation for studying genetic determinants of telomere length-variation and their roles in human disease.

  15. The cyto- and genotoxicity of organotin compounds is dependent on the cellular uptake capability

    International Nuclear Information System (INIS)

    Organotin compounds have been widely used as stabilizers and anti-fouling agents with the result that they are ubiquitously distributed in the environment. Organotins accumulate in the food chain and potential effects on human health are disquieting. It is not known as yet whether cell surface adsorption or accumulation within the cell, or indeed both is a prerequisite for the toxicity of organotin compounds. In this study, the alkylated tin derivatives monomethyltin trichloride (MMT), dimethyltin dichloride (DMT), trimethyltin chloride (TMT) and tetramethyltin (TetraMT) were investigated for cyto- and genotoxic effects in CHO-9 cells in relation to the cellular uptake. To identify genotoxic effects, induction of micronuclei (MN), chromosome aberrations (CA) and sister chromatid exchanges (SCE) were analyzed and the nuclear division index (NDI) was calculated. The cellular uptake was assessed using ICP-MS analysis. The toxicity of the tin compounds was also evaluated after forced uptake by electroporation. Our results show that uptake of the organotin compounds was generally low but dose-dependent. Only weak genotoxic effects were observed after exposure of cells to DMT and TMT. MMT and TetraMT were negative in the test systems. After forced uptake by electroporation MMT, DMT and TMT induced significant DNA damage at non-cytotoxic concentrations. The results presented here indicate a considerable toxicological potential of some organotin species but demonstrate clearly that the toxicity is modulated by the cellular uptake capability

  16. Long-range chromosome organization in E. coli: a site-specific system isolates the Ter macrodomain.

    Directory of Open Access Journals (Sweden)

    Axel Thiel

    Full Text Available The organization of the Escherichia coli chromosome into a ring composed of four macrodomains and two less-structured regions influences the segregation of sister chromatids and the mobility of chromosomal DNA. The structuring of the terminus region (Ter into a macrodomain relies on the interaction of the protein MatP with a 13-bp target called matS repeated 23 times in the 800-kb-long domain. Here, by using a new method that allows the transposition of any chromosomal segment at a defined position on the genetic map, we reveal a site-specific system that restricts to the Ter region a constraining process that reduces DNA mobility and delays loci segregation. Remarkably, the constraining process is regulated during the cell cycle and occurs only when the Ter MD is associated with the division machinery at mid-cell. The change of DNA properties does not rely on the presence of a trans-acting mechanism but rather involves a cis-effect acting at a long distance from the Ter region. Two specific 12-bp sequences located in the flanking Left and Right macrodomains and a newly identified protein designated YfbV conserved with MatP through evolution are required to impede the spreading of the constraining process to the rest of the chromosome. Our results unravel a site-specific system required to restrict to the Ter region the consequences of anchoring the Ter MD to the division machinery.

  17. DNA Damage in Melania Snail (Semisulcospira libertine) Irradiated with Gamma Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Tae Ho; Kim, Jin Kyu [Korea Atomic Energy Research Institute, Advanced Radiation Technology Institute, Jeongeup (Korea, Republic of); An, Kwang Guk [Chungnam National University, Daejeon (Korea, Republic of); Nili, Mohammad [Dawnesh Radiation Research Institute, Barcelona (Spain)

    2010-10-15

    Generally radiological protection has focused on human. But International Commission on Radiological Protection (ICRP) requires the effect data of ionizing radiation on nonhuman biota for the radiological protection of the environment. The choice of a melania snail as a model for environmental biomonitoring of radiation genotoxicity took into account that invertebrates represent one of aquatic species. The comet assay or single cell gel electrophoresis (SCGE) assay, first introduced by Ostling and Johanson, was used to detect DNA single strand breaks and to investigate the application of this technique as a tool for aquatic biomonitoring. Comet assay offers considerable advantages over some other assays used in DNA damage detection, such as chromosomal aberrations, sister chromatid Exchange and the micronucleus test, since there is no need for cells to be in a dividing state. Other advantages are its rapidity, relatively low coast, and wide applicability to virtually any nucleated cell type. In this study, we evaluated DNA damage in cells of Semisulcospira libertina after irradiation with {sup 60}Co gamma radiation by using the comet assay

  18. Putting CENP-A in its place.

    Science.gov (United States)

    Stellfox, Madison E; Bailey, Aaron O; Foltz, Daniel R

    2013-02-01

    The centromere is the chromosomal region that directs kinetochore assembly during mitosis in order to facilitate the faithful segregation of sister chromatids. The location of the human centromere is epigenetically specified. The presence of nucleosomes that contain the histone H3 variant, CENP-A, are thought to be the epigenetic mark that indicates active centromeres. Maintenance of centromeric identity requires the deposition of new CENP-A nucleosomes with each cell cycle. During S-phase, existing CENP-A nucleosomes are divided among the daughter chromosomes, while new CENP-A nucleosomes are deposited during early G1. The specific assembly of CENP-A nucleosomes at centromeres requires the Mis18 complex, which recruits the CENP-A assembly factor, HJURP. We will review the unique features of centromeric chromatin as well as the mechanism of CENP-A nucleosome deposition. We will also highlight a few recent discoveries that begin to elucidate the factors that temporally and spatially control CENP-A deposition. PMID:22729156

  19. DNA damage and repair mechanism. [DNA damage and repair mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Grossman, L.

    1976-01-01

    The ability of cells to survive in an environment specifically damaging to its DNA can be attributed to a variety of inherent repair mechanisms. This is a form of repair in which alterations are directly reversed to their original form. This reversibility is exemplified by the photoreactivation of ultraviolet-induced pyrimidine dimers. This phenomenon is attributable to the action of an enzyme, photolyase (photoreactivating enzyme), which is able to monomerize the uv-induced pyrimidine dimers in the presence of 320 to 370 nm light. Dilution of damage can be effected through a series of sister chromatid exchanges, controlled by recombinational mechanisms as a postreplication event. In this form of repair, replication proceeds to the point of damage, stops and resumes at the point of the next initiation site resulting in a gap in the newly synthesized daughter strand. It is presumed that those strands containing damaged regions exchange with undamaged regions of other DNA, strands, resulting in the eventual dilution of such damage.

  20. Cytogenetic analysis in Rothmund-Thomson syndrome with osteosarcoma

    Energy Technology Data Exchange (ETDEWEB)

    Amar, M.; Sutphen, R.; Kousseff, B.G. [Univ. of South Florida, Tampa, FL (United States)] [and others

    1994-09-01

    Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive condition of poikiloderma, erythema, depigmentation, hyperpigmentation, musculoskeletal abnormalities and abnormalities of hair, teeth and nails. Osteogenic sacoma has been reported in 8 patients. Abnormal chromosome studies have been reported in only two patients. Chromosome analysis of tumor or bone marrow has not been reported. We performed cytogenetic studies on a patient with Rothmund-Thomson syndrome and osteogenic sarcoma. Analysis of peripheral lymphocytes revealed 46, XX karyotype by GTW banding. Both spontaneous and chemically-induced chromosome breakage (0.35 and 0.8 breaks/cell) were increased but not significantly different from the age-matched control levels (0.05 and 0.25 breaks/cell). Analysis of mitogen-stimulated bone marrow by Giemsa banding showed slightly increased aneuploidy (20% of cells with random loss of 1 to 5 chromosomes each) and non-specific chromatid despiralization. All 34 cells analyzed from the tumor had normal diploid karyotype, 46.XX. Five of 40 cells derived from skin of the amputated right leg were hyperdiploid with karyotype 47, XX, +7. Skin from the right forearm showed normal karyotype, 46,XX. These results suggest that RTS is associated with chromosomal rearrangement causing acquired somatic mosaicism, including trisomy 7 anomalies. These abnormalities may aid in the diagnosis of RTS and provide clues to the location of the causative gene(s).

  1. Correlation of in vitro genotoxicity and oncogenicity induced by radiation and asbestos fibres

    International Nuclear Information System (INIS)

    The in vitro cytotoxicity and oncogenic potential of both native and acid leached asbestos fibres were studied using the C3H 10T1/2 cell model. Both native and leached fibres induced a dose-dependent toxicity. At high fibre concentrations, acid leached fibres were significantly less toxic than their untreated counterparts. While asbestos fibres alone do not induce oncogenic transformation at the concentration examined, it was found that both leached and native fibres substantially enhanced the oncogenicity of gamma-irradiation in a more than additive fashion. Although no significant chromosomal aberrations or sister chromatid exchanges (SCE) were found in asbestos treated cultures, a significantly higher number of SCEs was observed in cells treated with both asbestos and radiation compared to cells receiving radiation alone. The results suggest that the enhancement in radiation induced oncogenicity by asbestos fibres may be attributed to the mere physical presence of the fibres rather than any chemical contaminants the fibres may contain. Furthermore, the carcinogenicity of asbestos may be unrelated to genotoxicity. (author)

  2. Mitotic chromosome compaction via active loop extrusion

    Science.gov (United States)

    Goloborodko, Anton; Imakaev, Maxim; Marko, John; Mirny, Leonid; MIT-Northwestern Team

    During cell division, two copies of each chromosome are segregated from each other and compacted more than hundred-fold into the canonical X-shaped structures. According to earlier microscopic observations and the recent Hi-C study, chromosomes are compacted into arrays of consecutive loops of ~100 kilobases. Mechanisms that lead to formation of such loop arrays are largely unknown. Here we propose that, during cell division, chromosomes can be compacted by enzymes that extrude loops on chromatin fibers. First, we use computer simulations and analytical modeling to show that a system of loop-extruding enzymes on a chromatin fiber self-organizes into an array of consecutive dynamic loops. Second, we model the process of loop extrusion in 3D and show that, coupled with the topo II strand-passing activity, it leads to robust compaction and segregation of sister chromatids. This mechanism of chromosomal condensation and segregation does not require additional proteins or specific DNA markup and is robust against variations in the number and properties of such loop extruding enzymes. Work at NU was supported by the NSF through Grants DMR-1206868 and MCB-1022117, and by the NIH through Grants GM105847 and CA193419. Work at MIT was supported by the NIH through Grants GM114190 R01HG003143.

  3. The Meiotic Behavior of an Alien Chromosome in Triticum aestivum-Haynaldia villosa Monosomic Addition Lines

    Institute of Scientific and Technical Information of China (English)

    LI Rui-fen; LIANG Hong-xia; ZHAO Mao-lin

    2002-01-01

    By the combination of cytological analysis and using genomic in situ hybridization technique to identify an alien chromosome in wheat-Haynaldia villosa monosomic addition lines, we studied the meiotic behavior of the alien chromosome. The results indicated that the frequency of bivalent pairing was lower than the value expected in PMCs of two monosomic addition lines, the frequency of wheat chromosomes unpairing increased, and the wheat homologous chromosome pairing was interfered with by the added chromosome 6V at metaphase I. The chromosome 6V lagged in 20.3% -29.3% of PMCs, sister chromatids 6V early divided in 29.0% - 34.1% of PMCs, the single chromosome 6V in 18.2% - 26.1% of PMCs went to a pole randomly,the breakage frequency of chromosome 6V was 1.2% - 2.9%. Meanwhile, it was also found that several wheat chromosomes showed earlier division, lagging and breakage in a few PMCs. It revealed that the added chromosome 6V influenced the behavior of wheat chromosomes at anaphase. It was also found that the translocation was produced between 6V and wheat chromosomes in 1.2% of PMCs. It offered evidence for translocation between wheat and Haynaldia villosa 6V chromosomes.

  4. Radio-adaptive response

    International Nuclear Information System (INIS)

    An adaptive response to radiation stress was found as a suppressed induction of chromosomal damage including micronuclei and sister chromatid exchanges in cultured Chinese hamster V79 cells pre-exposed to very low doses of ionizing radiations. The mechanism underlying this novel chromosomal response, called 'radio-adaptive response (RAR)' has been studied progressively. The following results were obtained in recent experiments. 1. Low doses of β-rays from tritiated water (HTO) as well as tritium-thymidine can cause RAR. 2. Thermal neutrons, a high LET radiation, can not act as tritium β-rays or γ-rays. 3. The RAR expression is suppressed not only by the treatment with an inhibitor of protein synthesis but also by RNA synthesis inhibition. 4. Several proteins are newly synthesized concurrently with the RAR expression after the adapting doses, viewed by two-dimensional electrophoresis of cellular proteins. These results suggests that the RAR might be a cellular stress response to a signal produced preferentially by very low doses of low LET radiation under restricted conditions, accompany the inducible specific gene expression. (author)

  5. Cohesinopathies of a feather flock together.

    Directory of Open Access Journals (Sweden)

    Robert V Skibbens

    Full Text Available Roberts Syndrome (RBS and Cornelia de Lange Syndrome (CdLS are severe developmental maladies that present with nearly an identical suite of multi-spectrum birth defects. Not surprisingly, RBS and CdLS arise from mutations within a single pathway--here involving cohesion. Sister chromatid tethering reactions that comprise cohesion are required for high fidelity chromosome segregation, but cohesin tethers also regulate gene transcription, promote DNA repair, and impact DNA replication. Currently, RBS is thought to arise from elevated levels of apoptosis, mitotic failure, and limited progenitor cell proliferation, while CdLS is thought to arise, instead, from transcription dysregulation. Here, we review new information that implicates RBS gene mutations in altered transcription profiles. We propose that cohesin-dependent transcription dysregulation may extend to other developmental maladies; the diagnoses of which are complicated through multi-functional proteins that manifest a sliding scale of diverse and severe phenotypes. We further review evidence that cohesinopathies are more common than currently posited.

  6. TOXICOLOGY STUDIES OF LEWISITE AND SULFUR MUSTARD AGENTS:GENETIC TOXICITY OF LEWISITE (L) IN CHINESE HAMSTER OVARY CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Jostes,R.F. Jr.; Sasser, LB; Rausch, R.J.

    1989-05-31

    The cytotoxic clastogenic and mutagenic effects of the arsenic containing vesicant, Lewisite (L) [dichloro(2-chlorovinyl) arsine], have been investigated using Chinese hamster ovary cells. One hour exposures to Lewisite were cytotoxic in uM amounts. The cell survival response yields a D37 of 0.6 uM and an extrapolation number of 2.5. The mutagenic response at the hypoxantnine-guanine phosporibosyl transferase (HGPRT) locus was sporadic and not significantly greater than control values when cells were exposed over a range of 0.125 to2.0 uM. Sister chromatid exchange (SCE) induction, a measure of chromosomal rearrangement, was weakly positive over a range of 0.25 to 1.0 uM but the values were not significantly greater than the control response. Chromosomal aberrations were induced at 0.75 and 1.0 UMin one experiment and 0.5 and 0.75 uM in another experiment. The Induced values were significantly greater than the control values. Lewisite appears to be cytotoxic and clastogenic in our investigations but SCE and mutation at the HGPRT locus are not significantly greater than control values. Lewisita toxicity was in some ways similar to radiomimetic chemicals such as bleomycin.

  7. Certain patterns of DNA double strand breaks in membrane-attached superstructure units cause cell killing: a radiation action model

    International Nuclear Information System (INIS)

    The discovery that the chromosomal DNA is arranged in membrane-attached superstructure units (MASSUs) is the key for the understanding of the action of ionizing radiations on mammalian cells. Concerning X-rays the following hypothesis is proved true: The appearance of K ≥ 2 double-strand breaks (DSBs) in any MASSU of a G1 cell, respectively, in both MASSUs of any sister MASSU pair of a S cell results in its inactivation (k = actual number of DSBs per MASSU). DSB patterns in the MASSUs characterized by less DSBs will be repaired by recombination with homologous MASSUs. In G1 cells it occurs by the recombination with the homologous MASSU of the homologous chromosome. In the replicated MASSUs of S cells it probably happens by the succession of the following mechanisms: recombination repair of MASSUs with one DSB using the sister MASSU as a matrix (sister chromatid exchange), establishment of 1 intact genome by the substitution of the heavily damaged MASSUs (k ≥ 2) by the intact or repaired sister MASSU at the common attachment point, and degradation of the heavily damaged or abundant MASSUs. Thus the dependence of the form and the steepness of the dose survival curves on the cell cycle stages is interpreted by a universally valid radiation action mechanism. (author)

  8. Genotoxicity of drinking water from Chao Lake

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Q.; Jiao, Q.C. [Nanjing Univ. (China). Dept. of Biological Science and Technology; Huang, X.M.; Jiang, J.P.; Cui, S.Q.; Yao, G.H.; Jiang, Z.R.; Zhao, H.K.; Wang, N.Y. [Anhui Antiepidemic Station, Hefei (China)

    1999-02-01

    Genotoxic activity appears to originate primarily from reactions of chlorine with humic substances in the source waters. Comparisons of extracts of settled versus chlorinated water have confirmed that chlorinating during water treatment produces mutagenic activity in the mutagenicity tests. Present work on XAD-2 extracts of raw, chlorinated (treated), and settled water from the Chao Lake region of China has involved a battery of mutagenicity assays for various genetic endpoints: the Salmonella test, the sister-chromatid exchange (SCE) induction in Chinese hamster lung (CHL) cells, and the micronucleus (MN) induction in the peripheral blood erythrocytes of silver carp. Extracts of raw and treated water but not the settled water are mutagenic in the Salmonella assay. On the other hand, extracts of three water samples show activity in the SCE and MN assays, especially the raw and treated water. These data show that contamination and chlorinating contribute mutagens to drinking water and suggest that the mammalian assays may be more sensitive for detecting mutagenicity in aquatic environment than the Salmonella test.

  9. Flow sorting of the Y sex chromosome in the dioecious plant Melandrium album

    Energy Technology Data Exchange (ETDEWEB)

    Veuskens, J.; Jacobs, M.; Negrutiu, I. [Free Univ. of Brussels (Belgium)] [and others

    1995-12-01

    The preparation of stable chromosome suspensions and flow cytometric sorting of both the Y sex chromosome of the white campion, Melandrium album, and the deleted Y chromosome of an asexual mutant, 5K63, is described. The principle has been to maintain transformed roots in vitro, synchronize and block mitosis, reduce cells to protoplasts, and lyse these to release chromosomes. Such in vitro material, unlike many cell suspensions, showed a stable karyotype. Factors critical to producing high-quality chromosome suspensions from protoplasts include osmolality of isolation solutions and choice of spindle toxin and of lysis buffer. Agrobacterium rhizogenes transformed young growing root cultures were synchronized at G1/S with 50 {mu}M aphidicolin for 24 h and released to a mitotic block with 30 {mu}M oryzalin for 11 h. Protoplast preparations from such tissue routinely had metaphase indices reaching 15%. Suspensions of intact metaphase chromosomes, with few chromatids, were obtained by lysing swollen mitotic protoplasts in a citric acid/disodium phosphate buffer. Except for the presence of clumps of autosomal chromosomes near the X and Y chromosome zones, monoparametric histograms of fluorescence intensities of suspensions stained with 4{prime},6-diamidino-2-phenylindole showed profiles similar to theoretical flow karyotypes. Two types of Y chromosomes, one full-length and one partially deleted (from the asexual mutant), could be sorted at 90% purity (21-fold enrichment of Y). These results are discussed in the context of sex determination and differentiation in higher plants. 45 refs., 6 figs., 2 tabs.

  10. Genotoxicity of propoxur and its N-nitroso derivative in mammalian cells.

    Science.gov (United States)

    Wang, T C; Chiou, J M; Chang, Y L; Hu, M C

    1998-04-01

    N-Nitroso propoxur (NP) can be synthesized from a widely used N-methylcarbamate insecticide, propoxur, in vitro in the laboratory. Because of the extensive use of aerosol propoxur, the adverse effect on cells of respiratory origin is worth elucidating. In this report, two mammalian cell cultures from respiratory tissues [a hamster lung fibroblast, V79, and a primary rat tracheal epithelial cell (RTE)], were used to investigate the genotoxicity of propoxur and NP. NP was more cytotoxic than propoxur, with LC50s (20 and six times smaller, respectively in V79 and RTE cells. NP significantly induced sister chromatid exchange (> or = 0.01 microg/ml), chromosome aberration (> or = 2.5 microg/ml) and hprt gene mutation (> or = 0.5 microg/ml) in V79 cells, and cell transformation (> or = 0.2 microg/ml) in RTE cells. Results of chromosome aberration and hprt gene mutation indicated that the major pre-mutagenic lesion induced by NP must be the O6-methylguanine adduct, which frequently mispairs with thymine and thus gives rise to a GC-->AT transition. Propoxur was not mutagenic to either type of cells. However, it inhibited gap-junctional intercellular communication in V79 cells, which indicates that propoxur could act through some epigenetic mechanisms, such as tumor promotion or cell proliferation, in the multiple process of chemical carcinogenesis.

  11. Promotion of Homologous Recombination and Genomic Stability byRAD51AP1 via RAD51 Recombinase Enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Wiese, Claudia; Dray, Eloise; Groesser, Torsten; San Filippo,Joseph; Shi, Idina; Collins, David W.; Tsai, Miaw-Sheue; Williams,Gareth; Rydberg, Bjorn; Sung, Patrick; Schild, David

    2007-04-11

    Homologous recombination (HR) repairs chromosome damage and is indispensable for tumor suppression in humans. RAD51 mediates the DNA strand pairing step in HR. RAD51AP1 (RAD51 Associated Protein 1) is a RAD51-interacting protein whose function has remained elusive. Knockdown of RAD51AP1 in human cells by RNA interference engenders sensitivity to different types of genotoxic stress. Moreover, RAD51AP1-depleted cells are impaired for the recombinational repair of a DNA double-strand break and exhibit chromatid breaks both spontaneously and upon DNA damaging treatment. Purified RAD51AP1 binds dsDNA and RAD51, and it greatly stimulates the RAD51-mediated D-loop reaction. Biochemical and cytological results show that RAD51AP1 functions at a step subsequent to the assembly of the RAD51-ssDNA nucleoprotein filament. Our findings provide the first evidence that RAD51AP1 helps maintain genomic integrity via RAD51 recombinase enhancement.

  12. Clinical and cytogenetic analysis of human anemias from Jammu region of Jammu and Kashmir state

    Directory of Open Access Journals (Sweden)

    Upma

    2010-01-01

    Full Text Available Background : Anemias are the blood disorders characterized by reduction in the number of circulating red blood cells, the amount of hemoglobin, or the volume of packed red cells in blood. Chromosomal aberrations have often been reported from the bone marrow as well as cultured lymphocytes of the anemic patients. Aims: The aims of the study were to find out the commonest type of anemia occurring in the population of Jammu, India and to find out the chromosomal changes involved in the disorder. Material and Methods: Present study has been carried out on the bone marrow samples from 53 clinically diagnosed anemic patients. Cytogenetic study was carried out on slides prepared from these samples. Noncytogenetic factors like age, sex, religion, blood groups, family history of anemia, socioeconomic status, etc. have also been included in the study. Results: Megaloblastic anemia was found to be the commonest type of anemia. Centromere stretching, chromatid breaks, gaps, and elongation of chromosomes were recorded in patients with megaloblastic anemia and combined deficiency anemia. However, structural changes and numerical changes were totally absent. Conclusion: The commonest anemia among the people of Jammu region is megaloblastic anemia and its prevalence is increasing every year. Also, megaloblastic anemia is always associated with reversible cytogenetic changes.

  13. Effect of therapeutic hypothermia on chromosomal aberration in perinatal asphyxia

    Directory of Open Access Journals (Sweden)

    Bahubali D Gane

    2016-01-01

    Full Text Available Introduction: Perinatal asphyxia is a major cause for neonatal mortality and morbidity around the world. The reduction of O2results in the generation of reactive oxygen species which interact with nucleic acid and make alteration in the structure and functioning of the genome. We studied the effect of therapeutic hypothermia on chromosomes with karyotyping. Subjects and Methods: Babies in the hypothermia group were cooled for the first 72 h, using gel packs. Rectal temperature of 33–34°C was maintained. Blood sample was collected after completion of therapeutic hypothermia for Chromosomal analysis. It was done with IKAROS Karyotyping system, Metasystems, based on recommendations of International system of human cytogenetic nomenclature. Results: The median chromosomal aberration was lower in hypothermia [2(0-5] than control group [4(1-7] and chromatid breakage was commonest aberration seen. Chromosomal aberration was significantly higher in severe encephalopathy group than moderate encephalopathy group. Conclusion: We conclude that the TH significantly reduces DNA damage in perinatal asphyxia.

  14. Studies of DNA and chromosome damage in skin fibroblasts and blood lymphocytes from psoriasis patients treated with 8-methoxypsoralen and UVA irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Bredberg, A.; Lambert, B.; Lindblad, A.; Swanbeck, G.; Wennersten, G.

    1983-08-01

    Exposure of human lymphocytes and skin fibroblasts in vitro to a single, clinically used dose of PUVA, i.e., 0.1 micrograms/ml of 8-methoxypsoralen (8-MOP) plus 0.9-4 J/cm2 of longwave ultraviolet radiation (UVA), lead to the formation of DNA damage as determined by alkaline elution, and to chromosome aberrations and sister chromatid exchanges (SCE). When lymphocyte-enriched plasma was obtained from psoriasis patients 2 h after oral intake of 8-MOP and then UVA irradiated (1.8-3.6 J/cm2) in vitro, an increased frequency of chromosome aberrations and SCE was observed. Normal levels of chromosome aberrations and SCE were found in lymphocytes of psoriasis patients after 3-30 weeks of PUVA treatment in vivo. A small but statistically significant increase in the SCE frequency was observed in the lymphocytes of psoriasis patients treated for 1-6 years with PUVA (mean 18.0 SCE/cell) as compared with before PUVA (mean 15.8, p less than 0.05). Skin fibroblasts of psoriasis patients analyzed 5 years after the start of PUVA treatment showed a normal number of SCE but a high fraction of filter-retained DNA in the alkaline elution assay, suggesting the presence of cross-linked DNA.

  15. Adaptive response induced by occupational exposures to ionizing radiation

    International Nuclear Information System (INIS)

    We have found a significant decreased sensitivity to the cytogenetic effects of both ionizing radiation (IR) (2 Gy of γ rays) and bleomycin (BLM, 0,03 U/ml), in lymphocytes from individuals occupationally exposed to IR when compared with controls. These results suggest that occupational exposures to IR can induce adaptive response that can be detected by a subsequent treatment either by IR or by BLM. When a comparison is made between the cytogenetic effects of both treatments, no correlation was observed at the individual level. On the other hand, the individual frequencies of chromosome aberrations induced by a challenge dose of IR were negatively correlated with the occupationally received doses during the last three years. This correlation was not observed after the challenge treatment of BLM. Moreover, the individual frequencies of chromosome aberrations induced by IR treatment were homogeneous. This is not the case of the individual frequencies of chromatid aberrations induced by BLM, where a great heterogeneity was observed. (authors)

  16. Fragile DNA motifs trigger mutagenesis at distant chromosomal loci in saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Natalie Saini

    2013-06-01

    Full Text Available DNA sequences capable of adopting non-canonical secondary structures have been associated with gross-chromosomal rearrangements in humans and model organisms. Previously, we have shown that long inverted repeats that form hairpin and cruciform structures and triplex-forming GAA/TTC repeats induce the formation of double-strand breaks which trigger genome instability in yeast. In this study, we demonstrate that breakage at both inverted repeats and GAA/TTC repeats is augmented by defects in DNA replication. Increased fragility is associated with increased mutation levels in the reporter genes located as far as 8 kb from both sides of the repeats. The increase in mutations was dependent on the presence of inverted or GAA/TTC repeats and activity of the translesion polymerase Polζ. Mutagenesis induced by inverted repeats also required Sae2 which opens hairpin-capped breaks and initiates end resection. The amount of breakage at the repeats is an important determinant of mutations as a perfect palindromic sequence with inherently increased fragility was also found to elevate mutation rates even in replication-proficient strains. We hypothesize that the underlying mechanism for mutagenesis induced by fragile motifs involves the formation of long single-stranded regions in the broken chromosome, invasion of the undamaged sister chromatid for repair, and faulty DNA synthesis employing Polζ. These data demonstrate that repeat-mediated breaks pose a dual threat to eukaryotic genome integrity by inducing chromosomal aberrations as well as mutations in flanking genes.

  17. Increased STAG2 dosage defines a novel cohesinopathy with intellectual disability and behavioral problems.

    Science.gov (United States)

    Kumar, Raman; Corbett, Mark A; Van Bon, Bregje W M; Gardner, Alison; Woenig, Joshua A; Jolly, Lachlan A; Douglas, Evelyn; Friend, Kathryn; Tan, Chuan; Van Esch, Hilde; Holvoet, Maureen; Raynaud, Martine; Field, Michael; Leffler, Melanie; Budny, Bartłomiej; Wisniewska, Marzena; Badura-Stronka, Magdalena; Latos-Bieleńska, Anna; Batanian, Jacqueline; Rosenfeld, Jill A; Basel-Vanagaite, Lina; Jensen, Corinna; Bienek, Melanie; Froyen, Guy; Ullmann, Reinhard; Hu, Hao; Love, Michael I; Haas, Stefan A; Stankiewicz, Pawel; Cheung, Sau Wai; Baxendale, Anne; Nicholl, Jillian; Thompson, Elizabeth M; Haan, Eric; Kalscheuer, Vera M; Gecz, Jozef

    2015-12-20

    Next generation genomic technologies have made a significant contribution to the understanding of the genetic architecture of human neurodevelopmental disorders. Copy number variants (CNVs) play an important role in the genetics of intellectual disability (ID). For many CNVs, and copy number gains in particular, the responsible dosage-sensitive gene(s) have been hard to identify. We have collected 18 different interstitial microduplications and 1 microtriplication of Xq25. There were 15 affected individuals from 6 different families and 13 singleton cases, 28 affected males in total. The critical overlapping region involved the STAG2 gene, which codes for a subunit of the cohesin complex that regulates cohesion of sister chromatids and gene transcription. We demonstrate that STAG2 is the dosage-sensitive gene within these CNVs, as gains of STAG2 mRNA and protein dysregulate disease-relevant neuronal gene networks in cells derived from affected individuals. We also show that STAG2 gains result in increased expression of OPHN1, a known X-chromosome ID gene. Overall, we define a novel cohesinopathy due to copy number gain of Xq25 and STAG2 in particular.

  18. [Identification of genotoxic compounds used in leather processing industry].

    Science.gov (United States)

    Clonfero, E; Venier, P; Granella, M; Levis, A G

    1990-01-01

    The release of mutagens from 7 carbon black-based leather dyes and from leather samples at various stages of finishing was determined. After vigorous treatment with toluene, 4 commercial dyes yelded mutagenic extracts on Salmonella typhimurium in the presence of microsomal enzymes. Only in one case were the responsible chemicals identified as polycyclic aromatic hydrocarbons. The low bioavailability of mutagens contained in carbon black and their low mutagenic activity suggest that the risk associated with the use of these dyes is probably negligible. Soxhlet extracts with ethanol from finished leather were mutagenic on strain TA98 of Salmonella typhimurium in the absence of S9 mix. Analysis of extracts of leather samples at various intermediate stages of processing showed that mutagenic activity was detectable after the colouring process. The responsible compound was identified as a nitroazo dye (Colour Index: Acid Brown 83), with a mutagenic potential of about 4 revertant/micrograms. Eighteen commercial tannins containing mainly Cr(III) sulphates were assessed for genotoxicity. Most were contaminated with Cr(VI), a known mutagenic and carcinogenic agent, at levels sufficient to induce an increased frequency of SCE (sister chromatid exchanges) in mammalian cells (CHO, chinese hamster ovary) tested in vitro. PMID:2277596

  19. Cohesin interaction with centromeric minichromosomes shows a multi-complex rod-shaped structure.

    Directory of Open Access Journals (Sweden)

    Alexandra Surcel

    Full Text Available Cohesin is the protein complex responsible for maintaining sister chromatid cohesion. Cohesin interacts with centromeres and specific loci along chromosome arms known as Chromosome Attachment Regions (CARs. The cohesin holocomplex contains four subunits. Two of them, Smc1p (Structural maintenance of chromosome 1 protein and Smc3p, are long coiled-coil proteins, which heterodimerize with each other at one end. They are joined together at the other end by a third subunit, Scc1p, which also binds to the fourth subunit, Scc3p. How cohesin interacts with chromosomes is not known, although several models have been proposed, in part on the basis of in vitro assembly of purified cohesin proteins. To be able to observe in vivo cohesin-chromatin interactions, we have modified a Minichromosome Affinity Purification (MAP method to isolate a CAR-containing centromeric minichromosome attached to in vivo assembled cohesin. Transmission Electron Microscopy (TEM analysis of these minichromosomes suggests that cohesin assumes a rod shape and interacts with replicated minichromosome at one end of that rod. Additionally, our data implies that more than one cohesin molecule interacts with each pair of replicated minichromsomes. These molecules seem to be packed into a single thick rod, suggesting that the Smc1p and Smc3p subunits may interact extensively.

  20. Rad51C-deficient CL-V4B cells exhibit normal levels of mitomycin C-induced SCEs but reduced levels of UVC-induced SCEs

    International Nuclear Information System (INIS)

    The mechanisms of sister chromatid exchanges (SCEs) are not known. One hypothesis is that SCE is a manifestation of Rad51-dependent homologous recombination repair. In order to test this hypothesis, we have compared the frequencies of SCEs induced by mitomycin C (MMC) and 254 nm ultraviolet radiation (UVC) in wt V79B and the Rad51C-deficient CL-V4B cells. SCEs were analysed in the first (M1) and second (M2) post-treatment mitoses. In M1 MMC induced the same frequencies of SCEs in CL-V4B and V79B cells, while the UVC-induced SCE frequencies were lower in CL-V4B than V79B cells. In CL-V4B cells, MMC-induced SCEs were higher in M2 than in M1, suggesting that interstrand cross-links (ICL) are either not removed completely or are transformed into another form of DNA damage that persists until the next cell cycle. We suggest that SCEs may represent a mechanism to bypass MMC-induced ICL without their removal