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  • 1
    Publication Date: 2012-12-29
    Description: Infectious bursal disease (IBD) is an acute, highly contagious, and immunosuppressive avian disease caused by IBD virus (IBDV). Although IBDV-induced immunosuppression has been well established, the underlying exact molecular mechanism for such induction is not very clear. We report here the identification of IBDV VP4 as an interferon suppressor by interaction with the glucocorticoid-induced leucine zipper (GILZ) in host cells. We found that VP4 suppressed the expression of type I interferon in HEK293T cells after tumor necrosis factor alpha (TNF-α) treatment or Sendai virus (SeV) infection and in DF-1 cells after poly(I·C) stimulation. In addition, the VP4-induced suppression of type I interferon could be completely abolished by knockdown of GILZ by small interfering RNA (siRNA). Furthermore, knockdown of GILZ significantly inhibited IBDV growth in host cells, and this inhibition could be markedly mitigated by anti-alpha/beta interferon antibodies in the cell cultures ( P 〈 0.001). Thus, VP4-induced suppression of type I interferon is mediated by interaction with GILZ, a protein that appears to inhibit cell responses to viral infection.
    Print ISSN: 0022-538X
    Electronic ISSN: 1098-5514
    Topics: Medicine
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  • 2
    Publication Date: 2013-06-21
    Description: Well-characterized promoters are essential tools for metabolic engineering and synthetic biology. In Streptomyces coelicolor , the native kasO p is a temporally expressed promoter strictly controlled by two regulators, ScbR and ScbR2. In this work, first, kasO p was engineered to remove a common binding site of ScbR and ScbR2 upstream of its core region, thus generating a stronger promoter, kasO p 3 . Second, another ScbR binding site internal to the kasO p 3 core promoter region was abolished by random mutation and screening of the mutant library to obtain the strongest promoter, kasO p* (where the asterisk is used to distinguish the engineered promoter from the native promoter). The activities of kasO p* were compared with those of two known strong promoters, ermE p* and SF14p, in three Streptomyces species. kasO p* showed the highest activity at the transcription and protein levels in all three hosts. Furthermore, relative to ermE p* and SF14p, kasO p* was shown to confer the highest actinorhodin production level when used to drive the expression of actII -ORF4 in S. coelicolor . Therefore, kasO p* is a simple and well-defined strong promoter useful for gene overexpression in streptomycetes.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
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  • 3
    Publication Date: 2013-11-20
    Description: The development of a safe and efficient dengue vaccine represents a global challenge in public health. Chimeric dengue viruses (DENV) based on an attenuated flavivirus have been well developed as vaccine candidates by using reverse genetics. In this study, based on the full-length infectious cDNA clone of the well-known Japanese encephalitis virus live vaccine strain SA14-14-2 as a backbone, a novel chimeric dengue virus (named ChinDENV) was rationally designed and constructed by replacement with the premembrane and envelope genes of dengue 2 virus. The recovered chimeric virus showed growth and plaque properties similar to those of the parental DENV in mammalian and mosquito cells. ChinDENV was highly attenuated in mice, and no viremia was induced in rhesus monkeys upon subcutaneous inoculation. ChinDENV retained its genetic stability and attenuation phenotype after serial 15 passages in cultured cells. A single immunization with various doses of ChinDENV elicited strong neutralizing antibodies in a dose-dependent manner. When vaccinated monkeys were challenged with wild-type DENV, all animals except one that received the lower dose were protected against the development of viremia. Furthermore, immunization with ChinDENV conferred efficient cross protection against lethal JEV challenge in mice in association with robust cellular immunity induced by the replicating nonstructural proteins. Taken together, the results of this preclinical study well demonstrate the great potential of ChinDENV for further development as a dengue vaccine candidate, and this kind of chimeric flavivirus based on JE vaccine virus represents a powerful tool to deliver foreign antigens.
    Print ISSN: 0022-538X
    Electronic ISSN: 1098-5514
    Topics: Medicine
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  • 4
    Publication Date: 2013-11-05
    Description: 3,5,6-Trichloro-2-pyridinol (TCP) is a widespread pollutant. Some bacteria and fungi have been reported to degrade TCP, but the gene clusters responsible for TCP biodegradation have not been characterized. In this study, a fragment of the reduced flavin adenine dinucleotide (FADH 2 )-dependent monooxygenase gene tcpA was amplified from the genomic DNA of Ralstonia sp. strain T6 with degenerate primers. The tcpA disruption mutant strain T6- tcpA could not degrade TCP but could degrade the green intermediate metabolite 3,6- d i h ydroxy p yridine-2,5- d ione (DHPD), which was generated during TCP biodegradation by strain T6. The flanking sequences of tcpA were obtained by self-formed adaptor PCR. tcpRXA genes constitute a gene cluster. TcpR and TcpX are closely related to the LysR family transcriptional regulator and flavin reductase, respectively. T6- tcpA -com, the complementation strain for the mutant strain T6- tcpA , recovered the ability to degrade TCP, and the strain Escherichia coli DH10B- tcpRXA , which expressed the tcpRXA gene cluster, had the ability to transform TCP to DHPD, indicating that tcpA is a key gene in the initial step of TCP degradation and that TcpA dechlorinates TCP to DHPD. A library of DHPD degradation-deficient mutants of strain T6 was obtained by random transposon mutagenesis. The fragments flanking the Mariner transposon were amplified and sequenced, and the dhpRIJK gene cluster was cloned. DhpJ could transform DHPD to yield an intermediate product, 5- a mino-2,4,5- t ri o xo p entanoic a cid (ATOPA), which was further degraded by DhpI. DhpR and DhpK are closely related to the AraC family transcriptional regulator and the MFS family transporter, respectively.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
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  • 5
    Publication Date: 2013-11-24
    Description: KLF5 is an essential basic transcriptional factor that regulates a number of physiopathological processes. In this study, we tested whether and how KLF5 modulates the epithelial-mesenchymal transition (EMT). Using transforming growth factor β (TGF-β)- and epidermal growth factor (EGF)-treated epithelial cells as an established model of EMT, we found that KLF5 was downregulated during EMT and that knockdown of KLF5 induced EMT even in the absence of TGF-β and EGF treatment, as indicated by phenotypic and molecular EMT properties. Array-based screening suggested and biochemical analyses confirmed that the microRNA 200 (miR-200) microRNAs, a group of well-established EMT repressors, were transcriptionally activated by KLF5 via its direct binding to the GC boxes in miR-200 gene promoters. Functionally, overexpression of miR-200 prevented the EMT induced by KLF5 knockdown or by TGF-β and EGF treatment, and ectopic expression of KLF5 attenuated TGF-β- and EGF-induced EMT by rescuing the expression of miR-200. In mouse prostates, knockout of Klf5 downregulated the miR-200 family and induced molecular changes indicative of EMT. These findings indicate that KLF5 maintains epithelial characteristics and prevents EMT by transcriptionally activating the miR-200 family in epithelial cells.
    Print ISSN: 0270-7306
    Electronic ISSN: 1098-5549
    Topics: Biology , Medicine
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  • 6
    Publication Date: 2013-08-14
    Description: Hepatitis C virus (HCV) infection is a major cause of severe liver disease. Interferon (IFN)/ribavirin treatment remains the standard therapeutic regimen for HCV infection in most countries. IFN-stimulated genes are believed to contribute to antiviral effects. However, emerging evidence suggests that microRNAs (miRNAs), a class of noncoding small RNAs, are involved in the control of viral infection. Here, we systematically profiled the hepatocyte expression of a set of 750 miRNAs in response to alpha interferon (IFN-α) and interleukin-28B (IL-28B) treatments. The anti-HCV activity of differentially expressed miRNAs was evaluated using cell culture-derived HCV in vitro . The results demonstrate that let-7b had a significant anti-HCV effect by inhibiting HCV replication and viral protein translation in human hepatoma cells. In particular, we show that the inhibition of let-7b attenuated the anti-HCV effects of IFN-α and IL-28B. Furthermore, we show that the host factor insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) is a target of let-7b. IGF2BP1 was required for HCV replication, and its expression was downregulated by IFN-α and IL-28B. Deletion of the wild-type seed region of let-7b abolished its antiviral activity. Finally, we demonstrate that other let-7 family miRNAs were able to inhibit HCV and to suppress IGF2BP1 expression. In conclusion, we provide an example of a host miRNA regulated by type I and type III IFNs that inhibits HCV replication and infectivity by targeting host targets. These results highlight the important role of miRNAs in the host antiviral immune response and provide a novel candidate for anti-HCV therapy.
    Print ISSN: 0022-538X
    Electronic ISSN: 1098-5514
    Topics: Medicine
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  • 7
    Publication Date: 2013-10-10
    Description: Brain disturbances, like injuries or aberrant protein deposits, evoke nucleotide release or leakage from cells, leading to microglial chemotaxis and ingestion. Recent studies have identified P2Y 12 purinergic receptors as triggers for microglial chemotaxis and P2Y 6 receptors as mediators for phagocytosis. However, pinocytosis, known as the internalization of fluid-phase materials, has received much less attention. We found that ATP efficiently triggered pinocytosis in microglia. Pharmacological analysis and knockdown experiments demonstrated the involvement of P2Y 4 receptors and the phosphatidylinositol 3-kinase/Akt cascade in the nucleotide-induced pinocytosis. Further evidence indicated that soluble amyloid beta peptide 1-42 induced self-uptake in microglia through pinocytosis, a process involving activation of P2Y 4 receptors by autocrine ATP signaling. Our results demonstrate a previously unknown function of ATP as a "drink me" signal for microglia and P2Y 4 receptors as a potential therapeutic target for the treatment of Alzheimer's disease.
    Print ISSN: 0270-7306
    Electronic ISSN: 1098-5549
    Topics: Biology , Medicine
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  • 8
    Publication Date: 2014-01-08
    Description: Adipogenesis is a multistep process by which 3T3-L1 preadipocytes differentiate into mature adipocytes through mitotic clonal expansion (MCE) and terminal differentiation. The CCAAT/enhancer-binding protein β (C/EBPβ) is an important transcription factor that takes part in both of these processes. C/EBPβ not only transactivates C/EBPα and the peroxisome proliferator-activated receptor (PPAR), which cause 3T3-L1 preadipocytes to enter terminal adipocyte differentiation, but also is required to activate cell cycle genes necessary for MCE. The identification of potential cofactors of C/EBPβ will help to explain how C/EBPβ undertakes these specialized roles during the different stages of adipogenesis. In this study, we found that activating transcription factor 5 (ATF5) can bind to the promoter of C/EBPα via its direct interaction with C/EBPβ (which is mediated via the p300-dependent acetylation of ATF5), leading to enhanced C/EBPβ transactivation of C/EBPα. We also show that p300 is important for the interaction of ATF5 with C/EBPβ as well as for the binding activity of this complex on the C/EBPα promoter. Consistent with these findings, overexpression of ATF5 and an acetylated ATF5 mimic both promoted 3T3-L1 adipocyte differentiation, whereas short interfering RNA-mediated ATF5 downregulation inhibited this process. Furthermore, we show that the elevated expression of ATF5 is correlated with an obese phenotype in both mice and humans. In summary, we have identified ATF5 as a new cofactor of C/EBPβ and examined how C/EBPβ and ATF5 (acetylated by a p300-dependent mechanism) regulate the transcription of C/EBPα.
    Print ISSN: 0270-7306
    Electronic ISSN: 1098-5549
    Topics: Biology , Medicine
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  • 9
    Publication Date: 2014-01-08
    Description: The tumor suppressor p21 acts as a cell cycle inhibitor and has also been shown to regulate gene expression by functioning as a transcription corepressor. Here, we identified p21-regulated microRNAs (miRNAs) by sequencing small RNAs from isogenic p21 +/+ and p21 –/– cells. Three abundant miRNA clusters, miR-200b-200a-429, miR-200c-141, and miR-183-96-182, were downregulated in p21-deficient cells. Consistent with the known function of the miR-200 family and p21 in inhibition of the epithelial-mesenchymal transition (EMT), we observed EMT upon loss of p21 in multiple model systems. To explore a role of the miR-183-96-182 cluster in EMT, we identified its genome-wide targets and found that miR-183 and miR-96 repressed common targets, including SLUG , ZEB1 , ITGB1 , and KLF4 . Reintroduction of miR-200, miR-183, or miR-96 in p21 –/– cells inhibited EMT, cell migration, and invasion. Conversely, antagonizing miR-200 and miR-183-96-182 cluster miRNAs in p21 +/+ cells increased invasion and elevated the levels of VIM , ZEB1 , and SLUG mRNAs. Furthermore, we found that p21 forms a complex with ZEB1 at the miR-183-96-182 cluster promoter to inhibit transcriptional repression of this cluster by ZEB1, suggesting a reciprocal feedback loop.
    Print ISSN: 0270-7306
    Electronic ISSN: 1098-5549
    Topics: Biology , Medicine
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  • 10
    Publication Date: 2014-03-12
    Description: Chinese strong-flavored liquor (CSFL) accounts for more than 70% of all Chinese liquor production. Microbes in pit mud play key roles in the fermentation cellar for the CSFL production. However, microbial diversity, community structure, and cellar-age-related changes in pit mud are poorly understood. Here, we investigated the prokaryotic community structure and diversity in pit-mud samples with different cellar ages (1, 10, 25, and 50 years) using the pyrosequencing technique. Results indicated that prokaryotic diversity increased with cellar age until the age reached 25 years and that prokaryotic community structure changed significantly between three cellar ages (1, 10, and 25 years). Significant correlations between prokaryotic communities and environmental variables (pH, NH 4 + , lactic acid, butyric acid, and caproic acid) were observed. Overall, our study results suggested that the long-term brewing operation shapes unique prokaryotic community structure and diversity as well as pit-mud chemistry. We have proposed a three-phase model to characterize the changes of pit-mud prokaryotic communities. (i) Phase I is an initial domestication period. Pit mud is characterized by abundant Lactobacillus and high lactic acid and low pH levels. (ii) Phase II is a transition period. While Lactobacillus abundance decreases dramatically, that of Bacteroidetes and methanogens increases. (iii) Phase III is a relative mature period. The prokaryotic community shows the highest diversity and capability to produce more caproic acid as a precursor for synthesis of ethyl caproate, the main flavor component in CSFL. This research provides scientific evidence to support the practical experience that old fermentation cellars produce high-quality liquor.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
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