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  • 1
    Publikationsdatum: 2015-08-20
    Beschreibung: It has been hypothesised that positive associations between age and levels of oxidative stress-generated damage to DNA may be related to an age-dependent decline in DNA repair activity. The objective of this study was to investigate the association between age and repair activity of oxidatively damaged DNA in peripheral blood mononuclear cells (PBMCs). We isolated PBMCs from subjects aged 18–83 years, as part of a health survey of the Danish population that focussed on lifestyle factors. The level of DNA repair activity was measured as incisions on potassium bromate-damaged DNA by the comet assay. There was an inverse association between age and DNA repair activity with a 0.65% decline in activity per year from age 18 to 83 (95% confidence interval: 0.16–1.14% per year). Univariate regression analysis also indicated inverse associations between DNA repair activity and waist-hip ratio ( P 〈 0.05) and plasma concentrations of glycosylated hemoglobin ( P = 0.07). However, multivariate regression analysis only showed an inverse association between age and DNA repair activity ( P 〈 0.05), indicating that the decline in repair activity was not mediated by metabolic risk factors. In summary, the results show an inverse association between age and DNA repair activity of oxidatively damaged DNA.
    Print ISSN: 0267-8357
    Digitale ISSN: 1464-3804
    Thema: Biologie , Medizin
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2015-08-20
    Beschreibung: Exposure to traffic-related particulate matter (PM) has been associated with increased risk of lung disease, cancer and cardiovascular disease especially in elderly and overweight subjects. The proposed mechanisms involve intracellular production of reactive oxygen species (ROS), inflammation and oxidation-induced DNA damage studied mainly in young normal-weight subjects. We performed a controlled cross-over, randomised, single-blinded, repeated-measure study where 60 healthy subjects (25 males and 35 females) with age 55–83 years and body mass index above 25kg/m 2 were exposed for 5h to either particle-filtered or sham-filtered air from a busy street with number of concentrations and PM 2.5 levels of 1800/cm 3 versus 23 000/cm 3 and 3 µg/m 3 versus 24 µg/m 3 , respectively. Peripheral blood mononuclear cells (PBMCs) were collected and assayed for production of ROS with and without ex vivo exposure to nanosized carbon black as well as expression of genes related to inflammation ( chemokine (C-C motif) ligand 2 , interleukin-8 and tumour necrosis factor ), oxidative stress response ( heme oxygenase (decycling)-1 ) and DNA repair ( oxoguanine DNA glycosylase ). DNA strand breaks and oxidised purines were assayed by the alkaline comet assay. No statistically significant differences were found for any biomarker immediately after exposure to PM from urban street air although strand breaks and oxidised purines combined were significantly associated with the particle number concentration during exposure. In conclusion, 5h of controlled exposure to PM from urban traffic did not change the gene expression related to inflammation, oxidative stress or DNA repair, ROS production or oxidatively damaged DNA in PBMCs from elderly overweight human subjects.
    Print ISSN: 0267-8357
    Digitale ISSN: 1464-3804
    Thema: Biologie , Medizin
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2015-08-20
    Beschreibung: Ionising radiation causes free radical–mediated damage in cellular DNA. This damage is manifested as chromosomal aberrations and micronuclei (MN) in proliferating cells. Sesamol, present in sesame seeds, has the potential to scavenge free radicals; therefore, it can reduce radiation-induced cytogenetic damage in cells. The aim of this study was to investigate the radioprotective potential of sesamol in bone marrow cells of mice and related haematopoietic system against radiation-induced genotoxicity. A comparative study with melatonin was designed for assessing the radioprotective potential of sesamol. C57BL/6 mice were administered intraperitoneally with either sesamol or melatonin (10 and 20mg/kg body weight) 30min prior to 2-Gy whole-body irradiation (WBI) and sacrificed after 24h. Total chromosomal aberrations (TCA), MN and cell cycle analyses were performed using bone marrow cells. The comet assay was performed on bone marrow cells, splenocytes and lymphocytes. Blood was drawn to study haematological parameters. Prophylactic doses of sesamol (10 and 20mg/kg) in irradiated mice reduced TCA and micronucleated polychromatic erythrocyte frequency in bone marrow cells by 57% and 50%, respectively, in comparison with radiation-only groups. Sesamol-reduced radiation-induced apoptosis and facilitated cell proliferation. In the comet assay, sesamol (20mg/kg) treatment reduced radiation-induced comets (% DNA in tail) compared with radiation only ( P 〈 0.05). Sesamol also increased granulocyte populations in peripheral blood similar to melatonin. Overall, the radioprotective efficacy of sesamol was found to be similar to that of melatonin. Sesamol treatment also showed recovery of relative spleen weight at 24h of WBI. The results strongly suggest the radioprotective efficacy of sesamol in the haematopoietic system of mice.
    Print ISSN: 0267-8357
    Digitale ISSN: 1464-3804
    Thema: Biologie , Medizin
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2015-09-19
    Beschreibung: Nucleobase modifications dramatically alter nucleic acid structure and thermodynamics. 2-thiouridine (s 2 U) is a modified nucleobase found in tRNAs and known to stabilize U:A base pairs and destabilize U:G wobble pairs. The recently reported crystal structures of s 2 U-containing RNA duplexes do not entirely explain the mechanisms responsible for the stabilizing effect of s 2 U or whether this effect is entropic or enthalpic in origin. We present here thermodynamic evaluations of duplex formation using ITC and UV thermal denaturation with RNA duplexes containing internal s 2 U:A and s 2 U:U pairs and their native counterparts. These results indicate that s 2 U stabilizes both duplexes. The stabilizing effect is entropic in origin and likely results from the s 2 U-induced preorganization of the single-stranded RNA prior to hybridization. The same preorganizing effect is likely responsible for structurally resolving the s 2 U:U pair-containing duplex into a single conformation with a well-defined H-bond geometry. We also evaluate the effect of s 2 U on single strand conformation using UV- and CD-monitored thermal denaturation and on nucleoside conformation using 1 H NMR spectroscopy, MD and umbrella sampling. These results provide insights into the effects that nucleobase modification has on RNA structure and thermodynamics and inform efforts toward improving both ribozyme-catalyzed and nonenzymatic RNA copying.
    Print ISSN: 0305-1048
    Digitale ISSN: 1362-4962
    Thema: Biologie
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2015-09-19
    Beschreibung: DNA interstrand crosslinks (ICLs) are the primary mechanism for the cytotoxic activity of many clinical anticancer drugs, and numerous strategies for forming ICLs have been developed. One such method is using crosslink-forming oligonucleotides (CFOs). In this study, we designed a 4-amino-6-oxo-2-vinylpyrimidine (AOVP) derivative with an acyclic spacer to react selectively with guanine. The AOVP CFO exhibited selective crosslinking reactivity with guanine and thymine in DNA, and with guanine in RNA. These crosslinking reactions with guanine were accelerated in the presence of CoCl 2 , NiCl 2 , ZnCl 2 and MnCl 2 . In addition, we demonstrated that the AOVP CFO was reactive toward 8-oxoguanine opposite AOVP in the duplex DNA. The structural analysis of each guanine and 8-oxoguanine adduct in the duplex DNA was investigated by high-resolution NMR. The results suggested that AOVP reacts at the N2 amine in guanine and at the N1 or N2 amines in 8-oxoguanine in the duplex DNA. This study demonstrated the first direct determination of the adduct structure in duplex DNA without enzyme digestion.
    Print ISSN: 0305-1048
    Digitale ISSN: 1362-4962
    Thema: Biologie
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2015-09-19
    Beschreibung: The sequencing of the full transcriptome (RNA-seq) has become the preferred choice for the measurement of genome-wide gene expression. Despite its widespread use, challenges remain in RNA-seq data analysis. One often-overlooked aspect is normalization. Despite the fact that a variety of factors or ‘batch effects’ can contribute unwanted variation to the data, commonly used RNA-seq normalization methods only correct for sequencing depth. The study of gene expression is particularly problematic when it is influenced simultaneously by a variety of biological factors in addition to the one of interest. Using examples from experimental neuroscience, we show that batch effects can dominate the signal of interest; and that the choice of normalization method affects the power and reproducibility of the results. While commonly used global normalization methods are not able to adequately normalize the data, more recently developed RNA-seq normalization can. We focus on one particular method, RUVSeq and show that it is able to increase power and biological insight of the results. Finally, we provide a tutorial outlining the implementation of RUVSeq normalization that is applicable to a broad range of studies as well as meta-analysis of publicly available data.
    Schlagwort(e): Computational Methods, Transcriptome Mapping - Monitoring Gene Expression
    Print ISSN: 0305-1048
    Digitale ISSN: 1362-4962
    Thema: Biologie
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2015-09-19
    Beschreibung: Many antiproliferative G-quadruplexes (G4s) arise from the folding of GT-rich strands. Among these, the Thrombin Binding Aptamer (TBA), as a rare example, adopts a monomolecular well-defined G4 structure. Nevertheless, the potential anticancer properties of TBA are severely hampered by its anticoagulant action and, consequently, no related studies have appeared so far in the literature. We wish to report here that suitable chemical modifications in the TBA sequence can preserve its antiproliferative over anticoagulant activity. Particularly, we replaced one residue of the TT or TGT loops with a dibenzyl linker to develop seven new quadruplex-forming TBA based sequences (TBA-bs), which were studied for their structural (CD, CD melting, 1D NMR) and biological (fibrinogen, PT and MTT assays) properties. The three-dimensional structures of the TBA-bs modified at T13 (TBA-bs13) or T12 (TBA-bs12), the former endowed with selective antiproliferative activity, and the latter acting as potently as TBA in both coagulation and MTT assays, were further studied by 2D NMR restrained molecular mechanics. The comparative structural analyses indicated that neither the stability, nor the topology of the G4s, but the different localization of the two benzene rings of the linker was responsible for the loss of the antithrombin activity for TBA-bs13.
    Print ISSN: 0305-1048
    Digitale ISSN: 1362-4962
    Thema: Biologie
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 2015-09-19
    Beschreibung: A structural and functional classification of H/ACA and H/ACA-like motifs is obtained from the analysis of the H/ACA guide RNAs which have been identified previously in the genomes of Euryarchaea (Pyrococcus) and Crenarchaea (Pyrobaculum). A unified structure/function model is proposed based on the common structural determinants shared by H/ACA and H/ACA-like motifs in both Euryarchaea and Crenarchaea. Using a computational approach, structural and energetic rules for the guide:target RNA-RNA interactions are derived from structural and functional data on the H/ACA RNP particles. H/ACA(-like) motifs found in Pyrococcus are evaluated through the classification and their biological relevance is discussed. Extra-ribosomal targets found in both Pyrococcus and Pyrobaculum might support the hypothesis of a gene regulation mediated by H/ACA(-like) guide RNAs in archaea.
    Print ISSN: 0305-1048
    Digitale ISSN: 1362-4962
    Thema: Biologie
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2015-09-19
    Beschreibung: Houghton (HG) base pairing plays a central role in the DNA binding of proteins and small ligands. Probing detailed transition mechanism from Watson–Crick (WC) to HG base pair (bp) formation in duplex DNAs is of fundamental importance in terms of revealing intrinsic functions of double helical DNAs beyond their sequence determined functions. We investigated a free energy landscape of a free B-DNA with an adenosine–thymine (A–T) rich sequence to probe its conformational transition pathways from WC to HG base pairing. The free energy landscape was computed with a state-of-art two-dimensional umbrella molecular dynamics simulation at the all-atom level. The present simulation showed that in an isolated duplex DNA, the spontaneous transition from WC to HG bp takes place via multiple pathways. Notably, base flipping into the major and minor grooves was found to play an important role in forming these multiple transition pathways. This finding suggests that naked B-DNA under normal conditions has an inherent ability to form HG bps via spontaneous base opening events.
    Print ISSN: 0305-1048
    Digitale ISSN: 1362-4962
    Thema: Biologie
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    facet.materialart.
    Unbekannt
    Oxford University Press
    Publikationsdatum: 2015-09-19
    Beschreibung: Sequence alignment is a long standing problem in bioinformatics. The Basic Local Alignment Search Tool (BLAST) is one of the most popular and fundamental alignment tools. The explosive growth of biological sequences calls for speedup of sequence alignment tools such as BLAST. To this end, we develop high speed BLASTN (HS-BLASTN), a parallel and fast nucleotide database search tool that accelerates MegaBLAST—the default module of NCBI-BLASTN. HS-BLASTN builds a new lookup table using the FMD-index of the database and employs an accurate and effective seeding method to find short stretches of identities (called seeds) between the query and the database. HS-BLASTN produces the same alignment results as MegaBLAST and its computational speed is much faster than MegaBLAST. Specifically, our experiments conducted on a 12-core server show that HS-BLASTN can be 22 times faster than MegaBLAST and exhibits better parallel performance than MegaBLAST. HS-BLASTN is written in C++ and the related source code is available at https://github.com/chenying2016/queries under the GPLv3 license.
    Schlagwort(e): Computational Methods
    Print ISSN: 0305-1048
    Digitale ISSN: 1362-4962
    Thema: Biologie
    Publiziert von Oxford University Press
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