158 research outputs found

    Distinct requirements for the Rad32(Mre¹¹) nuclease and Ctp1(CtIP) in the removal of covalently bound topoisomerase I and II from DNA

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    For a cancer cell to resist treatment with drugs that trap topoisomerases covalently on the DNA, the topoisomerase must be removed. In this study, we provide evidence that the Schizosaccharomyces pombe Rad32Mre11 nuclease activity is involved in the removal of both Top2 from 5′ DNA ends as well as Top1 from 3′ ends in vivo. A ctp1CtIP deletion is defective for Top2 removal but overproficient for Top1 removal, suggesting that Ctp1CtIP plays distinct roles in removing topoisomerases from 5′ and 3′ DNA ends. Analysis of separation of function mutants suggests that MRN-dependent topoisomerase removal contributes significantly to resistance against topoisomerase-trapping drugs. This study has important implications for our understanding of the role of the MRN complex and CtIP in resistance of cells to a clinically important group of anticancer drugs

    Talc-dominated seafloor deposits reveal a new class of hydrothermal system

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    The Von Damm Vent Field (VDVF) is located on the flanks of the Mid-Cayman Spreading Centre, 13?km west of the axial rift, within a gabbro and peridotite basement. Unlike any other active vent field, hydrothermal precipitates at the VDVF comprise 85–90% by volume of the magnesium silicate mineral, talc. Hydrothermal fluids vent from a 3-m high, 1-m diameter chimney and other orifices at up to 215?°C with low metal concentrations, intermediate pH (5.8) and high concentrations (667?mmol?kg?1) of chloride relative to seawater. Here we show that the VDVF vent fluid is generated by interaction of seawater with a mafic and ultramafic basement which precipitates talc on mixing with seawater. The heat flux at the VDVF is measured at 487±101?MW, comparable to the most powerful magma-driven hydrothermal systems known, and may represent a significant mode of off-axis oceanic crustal cooling not previously recognized or accounted for in global models

    Species Delineation and Comparative Genomics within the Campylobacter ureolyticus Complex

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    Campylobacter ureolyticus is an emerging pathogen increasingly appreciated as a common cause of gastroenteritis and extra-intestinal infections in humans. Outside the setting of gastroenteritis, little work has been done to describe the genomic content and relatedness of the species, especially regarding clinical isolates. We reviewed the epidemiology of clinical C. ureolyticus cultured by our institution over the past 10 years. Fifty-one unique C. ureolyticus isolates were identified between January 2010 and August 2022, mostly originating from abscesses and blood cultures. To clarify the taxonomic relationships between isolates and to attribute specific genes with different clinical manifestations, we sequenced 19 available isolates from a variety of clinical specimen types and conducted a pangenomic analysis with publicly available C. ureolyticus genomes. Digital DNA:DNA hybridization suggested that these C. ureolyticus comprised a species complex of 10 species clusters (SCs) and several subspecies clusters. Although some orthologous genes or gene functions were enriched in isolates found in different SCs and clinical specimens, no association was significant. Nearly a third of the isolates possessed antimicrobial resistance genes, including the ermA resistance gene, potentially conferring resistance to macrolides, the treatment of choice for severe human campylobacteriosis. This work effectively doubles the number of publicly available C. ureolyticus genomes, provides further clarification of taxonomic relationships within this bacterial complex, and identifies target SCs for future analysis

    A survey of ex vivo/in vitro transduction efficiency of mammalian primary cells and cell lines with Nine natural adeno-associated virus (AAV1-9) and one engineered adeno-associated virus serotype

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    Abstract: Background: The ability to deliver a gene of interest into a specific cell type is an essential aspect of biomedical research. Viruses can be a useful tool for this delivery, particularly in difficult to transfect cell types. Adeno-associated virus (AAV) is a useful gene transfer vector because of its ability to mediate efficient gene transduction in numerous dividing and quiescent cell types, without inducing any known pathogenicity. There are now a number of natural for that designed AAV serotypes that each has a differential ability to infect a variety of cell types. Although transduction studies have been completed, the bulk of the studies have been done in vivo, and there has never been a comprehensive study of transduction ex vivo/in vitro. Methods: Each cell type was infected with each serotype at a multiplicity of infection of 100,000 viral genomes/cell and transduction was analyzed by flow cytometry + . Results: We found that AAV1 and AAV6 have the greatest ability to transduce a wide range of cell types, however, for particular cell types, there are specific serotypes that provide optimal transduction. Conclusions: In this work, we describe the transduction efficiency of ten different AAV serotypes in thirty-four different mammalian cell lines and primary cell types. Although these results may not be universal due to numerous factors such as, culture conditions and/ or cell growth rates and cell heterogeneity, these results provide an important and unique resource for investigators who use AAV as an ex vivo gene delivery vector or who work with cells that are difficult to transfect

    Sex differences in the cardiovascular effects of GnRH analogues

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    The integral role of the hypothalamic–pituitary–gonadal axis in reproductive processes makes it a prime therapeutic target. By inhibiting sex steroid synthesis, gonadotropin-releasing hormone (GnRH) analogues are used in the management of cancers, benign neoplasms, infertility and gender dysphoria. However, the wide application of these therapeutics raises concerns regarding the unintended effects upon the cardiovascular system. In males with prostate cancer, GnRH analogues when used as an androgen deprivation therapy appear to increase the risk of cardiovascular disease, which is the leading cause of death in this population. Therefore, due to the utilisation of GnRH analogues across the lifespan and gender spectrum, this relationship merits discussion. Existing data suggest an association between GnRH analogues and major adverse cardiovascular events in males. Conversely, females receiving GnRH analogues for breast cancer treatment appear to be at an increased risk of developing hypertension. In this narrative review, we describe the uses of GnRH analogues in adults, adolescents and children. We discuss whether sex plays a role in the cardiovascular effects of GnRH analogues and explore the significance of sex hormone receptors in the vasculature. We also consider confounding factors such as malignancy, advanced age and infertility

    Neuronal non-CG methylation is an essential target for MeCP2 function

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    DNA methylation is implicated in neuronal biology via the protein MeCP2, the mutation of which causes Rett syndrome. MeCP2 recruits the NCOR1/2 co-repressor complexes to methylated cytosine in the CG dinucleotide, but also to sites of non-CG methylation, which are abundant in neurons. To test the biological significance of the dual-binding specificity of MeCP2, we replaced its DNA binding domain with an orthologous domain from MBD2, which can only bind mCG motifs. Knockin mice expressing the domain-swap protein displayed severe Rett-syndrome-like phenotypes, indicating that normal brain function requires the interaction of MeCP2 with sites of non-CG methylation, specifically mCAC. The results support the notion that the delayed onset of Rett syndrome is due to the simultaneous post-natal accumulation of mCAC and its reader MeCP2. Intriguingly, genes dysregulated in both Mecp2 null and domain-swap mice are implicated in other neurological disorders, potentially highlighting targets of relevance to the Rett syndrome phenotype

    Recent Arctic climate change and its remote forcing of Northwest Atlantic shelf ecosystems

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    Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 3 (2012): 208-213, doi:10.5670/oceanog.2012.64.During recent decades, historically unprecedented changes have been observed in the Arctic as climate warming has increased precipitation, river discharge, and glacial as well as sea-ice melting. Additionally, shifts in the Arctic's atmospheric pressure field have altered surface winds, ocean circulation, and freshwater storage in the Beaufort Gyre. These processes have resulted in variable patterns of freshwater export from the Arctic Ocean, including the emergence of great salinity anomalies propagating throughout the North Atlantic. Here, we link these variable patterns of freshwater export from the Arctic Ocean to the regime shifts observed in Northwest Atlantic shelf ecosystems. Specifically, we hypothesize that the corresponding salinity anomalies, both negative and positive, alter the timing and extent of water-column stratification, thereby impacting the production and seasonal cycles of phytoplankton, zooplankton, and higher-trophic-level consumers. Should this hypothesis hold up to critical evaluation, it has the potential to fundamentally alter our current understanding of the processes forcing the dynamics of Northwest Atlantic shelf ecosystems.Funding for this research was provided by the National Science Foundation as part of the Regional and Pan-Regional Synthesis Phases of the US Global Ocean Ecosystem (GLOBEC) Program

    HIV Prevalence and Impact on Renutrition in Children Hospitalised for Severe Malnutrition in Niger: An Argument for More Systematic Screening

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    Background: In developing countries, malnutrition is a contributing factor in over 50 % of child deaths. Mortality rates are higher in underweight children, and HIV-infection is known to increase underweight. Our goals were to evaluate the prevalence of HIV among children hospitalised for severe malnutrition (SM) at the Niamey national hospital (Niger), and to compare renutrition and mortality by HIV-status. Methods: Retrospective study based on all children,5 years hospitalised for SM between January 1 st 2008 and July 1 st 2009. HIV-prevalence was the ratio of HIV+ children on the number of children tested. Duration of renutrition and mortality were described using survival curves. Results: During the study period, 477 children were hospitalised for SM. HIV testing was accepted in 470 (98.5%), of which 40 were HIV+ (HIV prevalence (95 % confidence interval) of 8.6 % (6.2–11.5)). Duration of renutrition was longer in HIV+ than HIV2 children (mean: 22 vs. 15 days; p = 0.003). During renutrition, 8 (20%) and 61 (14%) HIV+ and HIV2 children died, respectively (p = 0.81). Conclusion: Around 9 % of children hospitalised for severe malnutrition were HIV infected, while in Niger HIV prevalence i
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