954 resultados para STRAND SCISSION


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Recent years have seen a striking proliferation of the term ‘global’ in public and political discourse. The popularity of the term is a manifestation of the fact that there is a widespread notion that contemporary social reality is ‘global’. The acknowledgment of this notion has important political implications and raises questions about the role played by the idea of the ‘global’ in policy making. These questions, in turn, expose even more fundamental issues about whether the term ‘global’ indicates a difference in kind, even an ontological shift, and, if so, how to approach it. This paper argues that the notion of ‘global’, in other words the ‘global dimension’, is a significant aspect of contemporary politics that needs to be investigated. The paper argues that in the globalization discourse of International Studies ‘global’ is ‘naturalized’, which means that it is taken for granted and assumed to be self-evident. The term ‘global’ is used mainly in a descriptive way and subsumed under the rubric of ‘globalization’. ‘Global’ tends to be equated with transnational and/or world-wide; hence, it addresses quantitative differences in degree but not (alleged) differences in kind. In order to advance our understanding of contemporary politics, ‘global’ needs to be taken seriously. This means, firstly, to understand and to conceptualize ‘global’ as a social category; and, secondly, to uncover ‘global’ as a ‘naturalized’ concept in the Political and International Studies strand of the globalization discourse in order to rescue it for innovative new approaches in the investigation of contemporary politics. In order to do so, the paper suggests adopting a strong linguistic approach starting with the analysis of the word ‘global’. Based on insights from post-structuralism as well as cognitive and general constructivist perspectives it argues that a frame-based corpus linguistic analysis offers the possibility of investigating the collective/social meaning(s) of global in order to operationalize them for the analysis of the ‘global dimension’ of contemporary politics.

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Human MRE11 is a key enzyme in DNA double-strand break repair and genome stability. Human MRE11 bears a glycine-arginine-rich (GAR) motif that is conserved among multicellular eukaryotic species. We investigated how this motif influences MRE11 function. Human MRE11 alone or a complex of MRE11, RAD50, and NBS1 (MRN) was methylated in insect cells, suggesting that this modification is conserved during evolution. We demonstrate that PRMT1 interacts with MRE11 but not with the MRN complex, suggesting that MRE11 arginine methylation occurs prior to the binding of NBS1 and RAD50. Moreover, the first six methylated arginines are essential for the regulation of MRE11 DNA binding and nuclease activity. The inhibition of arginine methylation leads to a reduction in MRE11 and RAD51 focus formation on a unique double-strand break in vivo. Furthermore, the MRE11-methylated GAR domain is sufficient for its targeting to DNA damage foci and colocalization with gamma-H2AX. These studies highlight an important role for the GAR domain in regulating MRE11 function at the biochemical and cellular levels during DNA double-strand break repair.

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Lynch syndrome is one of the most common hereditary colorectal cancer (CRC) syndrome and is caused by germline mutations of MLH1, MSH2 and more rarely MSH6, PMS2, MLH3 genes. Whereas the absence of MSH2 protein is predictive of Lynch syndrome, it is not the case for the absence of MLH1 protein. The purpose of this study was to develop a sensitive and cost effective algorithm to select Lynch syndrome cases among patients with MLH1 immunohistochemical silencing. Eleven sporadic CRC and 16 Lynch syndrome cases with MLH1 protein abnormalities were selected. The BRAF c.1799T> A mutation (p.Val600Glu) was analyzed by direct sequencing after PCR amplification of exon 15. Methylation of MLH1 promoter was determined by Methylation-Sensitive Single-Strand Conformation Analysis. In patients with Lynch syndrome, there was no BRAF mutation and only one case showed MLH1 methylation (6%). In sporadic CRC, all cases were MLH1 methylated (100%) and 8 out of 11 cases carried the above BRAF mutation (73%) whereas only 3 cases were BRAF wild type (27%). We propose the following algorithm: (1) no further molecular analysis should be performed for CRC exhibiting MLH1 methylation and BRAF mutation, and these cases should be considered as sporadic CRC; (2) CRC with unmethylated MLH1 and negative for BRAF mutation should be considered as Lynch syndrome; and (3) only a small fraction of CRC with MLH1 promoter methylation but negative for BRAF mutation should be true Lynch syndrome patients. These potentially Lynch syndrome patients should be offered genetic counselling before searching for MLH1 gene mutations.

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We give a unified solution the conjugacy problem in Thompson’s groups F, V , and T using strand diagrams, and we analyze the complexity of the resulting algorithms.

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We describe an explicit relationship between strand diagrams and piecewise-linear functions for elements of Thompson’s group F. Using this correspondence, we investigate the dynamics of elements of F, and we show that conjugacy of one-bump functions can be described by a Mather-type invariant.

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In this paper a number of anticancer agents of natural origin will be presented. Hydroxycamtothecin (HCPT) was found to produce a strong inhibitory action on a variety of animal tumors. It is also effective for treatment of patients with gastric carcinoma, liver carcinoma, tumor of head and neck or leukemia. Pharmacologic studies showed that it could depress S phase of tumor cells significantly and cause formation of cellular chromatid breaks. By means of alkaline elution and nick translation methods it has been proved that HCPT induced DNA singlo strand breaks remarkably. Homoharringyonine (hhrt) was shown to be effective against acute leukemia. Recent experiments in tumor-bearing mice inidcated that (HHRT) could diminish tumor metastasis. Using molecular hybridization technique it was demonstrated that (HHRT) decreased the content of c-myc RNA in the cytoplasm but not in the nuclei. Lycobetaine (LBT) poddrddrf dytnh inhibitory effects on a number of ascites tumors. In clinical trials it was against ovarian and gastric carcinomas. It is able to intercalate into DNA. Oxalysine (OXL) is a new antibiotic and shown to be effective against tumor metastatis. When used in combination with 5-FU, its anticancer action could be enhanced. Other natural compounds such as indirubin, ß-elemene, irisquinone, oridonine, norcantharidin and PSP have been also found to possess antitumor action.

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An abundant scientific literature about climate change economics points out that the future participation of developing countries in international environmental policies will depend on their amount of pay offs inside and outside specific agreements. These studies are aimed at analyzing coalitions stability typically through a game theoretical approach. Though these contributions represent a corner stone in the research field investigating future plausible international coalitions and the reasons behind the difficulties incurred over time to implement emissions stabilizing actions, they cannot disentangle satisfactorily the role that equality play in inducing poor regions to tackle global warming. If we focus on the Stern Review findings stressing that climate change will generate heavy damages and policy actions will be costly in a finite time horizon, we understand why there is a great incentive to free ride in order to exploit benefits from emissions reduction efforts of others. The reluctance of poor countries in joining international agreements is mainly supported by historical responsibility of rich regions in generating atmospheric carbon concentration, whereas rich countries claim that emissions stabilizing policies will be effective only when developing countries will join them.Scholars recently outline that a perceived fairness in the distribution of emissions would facilitate a wide spread participation in international agreements. In this paper we overview the literature about distributional aspects of emissions by focusing on those contributions investigating past trends of emissions distribution through empirical data and future trajectories through simulations obtained by integrated assessment models. We will explain methodologies used to elaborate data and the link between real data and those coming from simulations. Results from this strand of research will be interpreted in order to discuss future negotiations for post Kyoto agreements that will be the focus of the next. Conference of the Parties in Copenhagen at the end of 2009. A particular attention will be devoted to the role that technological change will play in affecting the distribution of emissions over time and to how spillovers and experience diffusion could influence equality issues and future outcomes of policy negotiations.

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BACKGROUND: The Nuclear Factor I (NFI) family of DNA binding proteins (also called CCAAT box transcription factors or CTF) is involved in both DNA replication and gene expression regulation. Using chromatin immuno-precipitation and high throughput sequencing (ChIP-Seq), we performed a genome-wide mapping of NFI DNA binding sites in primary mouse embryonic fibroblasts. RESULTS: We found that in vivo and in vitro NFI DNA binding specificities are indistinguishable, as in vivo ChIP-Seq NFI binding sites matched predictions based on previously established position weight matrix models of its in vitro binding specificity. Combining ChIP-Seq with mRNA profiling data, we found that NFI preferentially associates with highly expressed genes that it up-regulates, while binding sites were under-represented at expressed but unregulated genes. Genomic binding also correlated with markers of transcribed genes such as histone modifications H3K4me3 and H3K36me3, even outside of annotated transcribed loci, implying NFI in the control of the deposition of these modifications. Positional correlation between + and - strand ChIP-Seq tags revealed that, in contrast to other transcription factors, NFI associates with a nucleosomal length of cleavage-resistant DNA, suggesting an interaction with positioned nucleosomes. In addition, NFI binding prominently occurred at boundaries displaying discontinuities in histone modifications specific of expressed and silent chromatin, such as loci submitted to parental allele-specific imprinted expression. CONCLUSIONS: Our data thus suggest that NFI nucleosomal interaction may contribute to the partitioning of distinct chromatin domains and to epigenetic gene expression regulation.NFI ChIP-Seq and input control DNA data were deposited at Gene Expression Omnibus (GEO) repository under accession number GSE15844. Gene expression microarray data for mouse embryonic fibroblasts are on GEO accession number GSE15871.

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Chromosomal and plasmid DNA molecules in bacterial cells are maintained under torsional tension and are therefore supercoiled. With the exception of extreme thermophiles, supercoiling has a negative sign, which means that the torsional tension diminishes the DNA helicity and facilitates strand separation. In consequence, negative supercoiling aids such processes as DNA replication or transcription that require global- or local-strand separation. In extreme thermophiles, DNA is positively supercoiled which protects it from thermal denaturation. While the role of DNA supercoiling connected to the control of DNA stability, is thoroughly researched and subject of many reviews, a less known role of DNA supercoiling emerges and consists of aiding DNA topoisomerases in DNA decatenation and unknotting. Although DNA catenanes are natural intermediates in the process of DNA replication of circular DNA molecules, it is necessary that they become very efficiently decatenated, as otherwise the segregation of freshly replicated DNA molecules would be blocked. DNA knots arise as by-products of topoisomerase-mediated intramolecular passages that are needed to facilitate general DNA metabolism, including DNA replication, transcription or recombination. The formed knots are, however, very harmful for cells if not removed efficiently. Here, we overview the role of DNA supercoiling in DNA unknotting and decatenation.

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Targeted mutagenesis directed by oligonucleotides (ONs) is a promising method for manipulating the genome in higher eukaryotes. In this study, we have compared gene editing by different ONs on two new target sequences, the eBFP and the rd1 mutant photoreceptor betaPDE cDNAs, which were integrated as single copy transgenes at the same genomic site in 293T cells. Interestingly, antisense ONs were superior to sense ONs for one target only, showing that target sequence can by itself impart strand-bias in gene editing. The most efficient ONs were short 25 nt ONs with flanking locked nucleic acids (LNAs), a chemistry that had only been tested for targeted nucleotide mutagenesis in yeast, and 25 nt ONs with phosphorothioate linkages. We showed that LNA-modified ONs mediate dose-dependent target modification and analyzed the importance of LNA position and content. Importantly, when using ONs with flanking LNAs, targeted gene modification was stably transmitted during cell division, which allowed reliable cloning of modified cells, a feature essential for further applications in functional genomics and gene therapy. Finally, we showed that ONs with flanking LNAs aimed at correcting the rd1 stop mutation could promote survival of photoreceptors in retinas of rd1 mutant mice, suggesting that they are also active in vivo.

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A structural and functional analysis of the 5'-end region of the Xenopus laevis vitellogenin gene A1 revealed two transcription initiation sites located 1.8 kilobases apart. A RNA polymerase II binding assay indicates that both promoters form initiation complexes efficiently. In vitro, using a transcription assay derived from a HeLa whole-cell extract, the upstream promoter is more than 10-fold stronger than the downstream one. In contrast, both promoters have a similar strength in a HeLa nuclear extract. In vivo, that is in estrogen-stimulated hepatocytes, it is the downstream promoter homologous to the one used by the other members of the vitellogenin gene family, which is 50-fold stronger than the upstream promoter. Thus, if functional vitellogenin mRNA results from this latter activity, it would contribute less than 1% to the synthesis of vitellogenin by fully induced Xenopus hepatocytes expressing the four vitellogenin genes. In contrast, both gene A1 promoters are silent in uninduced hepatocytes. Transfection experiments using the Xenopus cell line B3.2 in which estrogen-responsiveness has been introduced reveal that the strong downstream promoter is controlled by an estrogen responsive element (ERE) located 330 bp upstream of it. The upstream promoter can also be controlled by the same ERE. Since the region comprising the upstream promoter is flanked by a 200 base pair long inverted repeat with stretches of homology to other regions of the X. laevis genome, we speculate that it might have been inserted upstream of the vitellogenin gene A1 by a recombination event and consequently brought under control of the ERE lying 1.5 kilobases downstream.

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We demonstrate that RecA protein can mediate annealing of complementary DNA strands in vitro by at least two different mechanisms. The first annealing mechanism predominates under conditions where RecA protein causes coaggregation of single-stranded DNA (ssDNA) molecules and where RecA-free ssDNA stretches are present on both reaction partners. Under these conditions annealing can take place between locally concentrated protein-free complementary sequences. Other DNA aggregating agents like histone H1 or ethanol stimulate annealing by the same mechanism. The second mechanism of RecA-mediated annealing of complementary DNA strands is best manifested when preformed saturated RecA-ssDNA complexes interact with protein-free ssDNA. In this case, annealing can occur between the ssDNA strand resident in the complex and the ssDNA strand that interacts with the preformed RecA-ssDNA complex. Here, the action of RecA protein reflects its specific recombination promoting mechanism. This mechanism enables DNA molecules resident in the presynaptic RecA-DNA complexes to be exposed for hydrogen bond formation with DNA molecules contacting the presynaptic RecA-DNA filament.

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PURPOSE: The aim of this study was to determine whether tumor location proximal or distal to the splenic flexure is associated with distinct molecular patterns and can predict clinical outcome in a homogeneous group of patients with Dukes B (T3-T4, N0, M0) colorectal cancer. It has been hypothesized that proximal and distal colorectal cancer may arise through different pathogenetic mechanisms. Although p53 and Ki-ras gene mutations occur frequently in distal tumors, another form of genomic instability associated with defective DNA mismatch repair has been predominantly identified in the proximal colon. To date, however, the clinical usefulness of these molecular characteristics remains unproven. METHODS: A total of 126 patients with a lymph node-negative sporadic colon or rectum adenocarcinoma were prospectively assessed with the endpoint of death by cancer. No patient received either radiotherapy or chemotherapy. p53 protein was studied by immunohistochemistry using DO-7 monoclonal antibody, and p53 and Ki-ras gene mutations were detected by single strand conformation polymorphism assay. RESULTS: During a mean follow-up of 67 months, the overall five-year survival was 70 percent. Nuclear p53 staining was found in 57 tumors (47 percent), and was more frequent in distal than in proximal tumors (55 vs. 21 percent; chi-squared test, P < 0.001). For the whole group, p53 protein expression correlated with poor survival in univariate and multivariate analysis (log-rank test, P = 0.01; hazard ratio = 2.16; 95 percent confidence interval = 1.12-4.11, P = 0.02). Distal colon tumors and rectal tumors exhibited similar molecular patterns and showed no difference in clinical outcome. In comparison with distal colorectal cancer, proximal tumors were found to be statistically significantly different on the following factors: mucinous content (P = 0.008), degree of histologic differentiation (P = 0.012), p53 protein expression, and gene mutation (P = 0.001 and 0.01 respectively). Finally, patients with proximal tumors had a marginally better survival than those with distal colon or rectal cancers (log-rank test, P = 0.045). CONCLUSION: In this series of Dukes B colorectal cancers, p53 protein expression was an independent factor for survival, which also correlated with tumor location. Eighty-six percent of p53-positive tumors were located in the distal colon and rectum. Distal colon and rectum tumors had similar molecular and clinical characteristics. In contrast, proximal neoplasms seem to represent a distinct entity, with specific histopathologic characteristics, molecular patterns, and clinical outcome. Location of the neoplasm in reference to the splenic flexure should be considered before group stratification in future trials of adjuvant chemotherapy in patients with Dukes B tumors.

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Purpose of the Study: To elucidate the mechanism of homologous recombination and double-strand break repair mediated by the eukaryotic recombination pin, Rad51.

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CONTEXT: New trial data and drug regimens that have become available in the last 2 years warrant an update to guidelines for antiretroviral therapy (ART) in human immunodeficiency virus (HIV)-infected adults in resource-rich settings. OBJECTIVE: To provide current recommendations for the treatment of adult HIV infection with ART and use of laboratory-monitoring tools. Guidelines include when to start therapy and with what drugs, monitoring for response and toxic effects, special considerations in therapy, and managing antiretroviral failure. DATA SOURCES, STUDY SELECTION, AND DATA EXTRACTION: Data that had been published or presented in abstract form at scientific conferences in the past 2 years were systematically searched and reviewed by an International Antiviral Society-USA panel. The panel reviewed available evidence and formed recommendations by full panel consensus. DATA SYNTHESIS: Treatment is recommended for all adults with HIV infection; the strength of the recommendation and the quality of the evidence increase with decreasing CD4 cell count and the presence of certain concurrent conditions. Recommended initial regimens include 2 nucleoside reverse transcriptase inhibitors (tenofovir/emtricitabine or abacavir/lamivudine) plus a nonnucleoside reverse transcriptase inhibitor (efavirenz), a ritonavir-boosted protease inhibitor (atazanavir or darunavir), or an integrase strand transfer inhibitor (raltegravir). Alternatives in each class are recommended for patients with or at risk of certain concurrent conditions. CD4 cell count and HIV-1 RNA level should be monitored, as should engagement in care, ART adherence, HIV drug resistance, and quality-of-care indicators. Reasons for regimen switching include virologic, immunologic, or clinical failure and drug toxicity or intolerance. Confirmed treatment failure should be addressed promptly and multiple factors considered. CONCLUSION: New recommendations for HIV patient care include offering ART to all patients regardless of CD4 cell count, changes in therapeutic options, and modifications in the timing and choice of ART in the setting of opportunistic illnesses such as cryptococcal disease and tuberculosis.