排序方式: 共有113条查询结果,搜索用时 281 毫秒
11.
Thomas R Grimsley N Escande ML Subirana L Derelle E Moreau H 《Environmental microbiology》2011,13(6):1412-1420
Viruses are known to play a key role in the regulation of eukaryotic phytoplankton population densities; however, little is known about the mechanisms of how they interact with their hosts and how phytoplankton populations mediate their regulations. Viruses are obligate parasites that depend on host cell machinery for their dissemination in the environment (most of the time through host cell lysis that liberates many new particles). But viruses also depend on a reliable host population to carry on their replication before losing their viability. How do hosts cells survive when they coexist with their viruses? We show that clonal lines of three picoeukaryotic green algae (i.e. Bathycoccus sp., Micromonas sp., Ostreococcus tauri) reproducibly acquire resistance to their specific viruses following a round of infection. Our observations show that two mechanisms of resistance may operate in O. tauri. In the first resistant type, viruses can attach to their host cells but no new particles develop. In the second one, O. tauri acquires tolerance to its virus and releases these viruses consistently. These lines maintained their resistance over a 3‐year period, irrespective of whether or not they were re‐challenged with new viral inoculations. Co‐culturing resistant and susceptible lines revealed resistance to be associated with reduced host fitness in terms of growth rate. 相似文献
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Hu L Deeney JT Nolan CJ Peyot ML Ao A Richard AM Luc E Faergeman NJ Knudsen J Guo W Sorhede-Winzell M Prentki M Corkey BE 《American journal of physiology. Endocrinology and metabolism》2005,289(6):E1085-E1092
Intracellular lipolysis is a major pathway of lipid metabolism that has roles, not only in the provision of free fatty acids as energy substrate, but also in intracellular signal transduction. The latter is likely to be particularly important in the regulation of insulin secretion from islet beta-cells. The mechanisms by which lipolysis is regulated in different tissues is, therefore, of considerable interest. Here, the effects of long-chain acyl-CoA esters (LC-CoA) on lipase activity in islets and adipocytes were compared. Palmitoyl-CoA (Pal-CoA, 1-10 microM) stimulated lipase activity in islets from both normal and hormone-sensitive lipase (HSL)-null mice and in phosphatase-treated islets, indicating that the stimulatory effect was neither on HSL nor phosphorylation dependent. In contrast, we reproduced the previously published observations showing inhibition of HSL activity by LC-CoA in adipocytes. The inhibitory effect of LC-CoA on adipocyte HSL was dependent on phosphorylation and enhanced by acyl-CoA-binding protein (ACBP). In contrast, the stimulatory effect on islet lipase activity was blocked by ACBP, presumably due to binding and sequestration of LC-CoA. These data suggest the following intertissue relationship between islets and adipocytes with respect to fatty acid metabolism, LC-CoA signaling, and lipolysis. Elevated LC-CoA in islets stimulates lipolysis to generate a signal to increase insulin secretion, whereas elevated LC-CoA in adipocytes inhibits lipolysis. Together, these opposite actions of LC-CoA lower circulating fat by inhibiting its release from adipocytes and promoting fat storage via insulin action. 相似文献
13.
SM Belgnaoui S Paz S Samuel ML Goulet Q Sun M Kikkert K Iwai I Dikic J Hiscott R Lin 《Cell host & microbe》2012,12(2):211-222
The RIG-I/Mda5 sensors recognize viral intracellular RNA and trigger host antiviral responses. RIG-I signals through the adaptor protein MAVS, which engages various TRAF family members and results in type I interferon (IFNs) and proinflammatory cytokine production via activation of IRFs and NF-κB, respectively. Both the IRF and NF-κB pathways also require the adaptor protein NEMO. We determined that the RIG-I pathway is differentially regulated by the linear ubiquitin assembly complex (LUBAC), which consists of the E3 ligases HOIL-1L, HOIP, and the accessory protein SHARPIN. LUBAC downregulated virus-mediated IFN induction by targeting NEMO for linear ubiquitination. Linear ubiquitinated NEMO associated with TRAF3 and disrupted the MAVS-TRAF3 complex, which inhibited IFN activation while stimulating NF-κB-dependent signaling. In SHARPIN-deficient MEFs, vesicular stomatitis virus replication was decreased due to increased IFN production. Linear ubiquitination thus switches NEMO from a positive to a negative regulator of RIG-I signaling, resulting in an attenuated IFN response. 相似文献
14.
Marie-Line Maublanc Eric Bideau Romain Willemet Clara Bardonnet Georges Gonzalez Lionel Desneux Nicolas Cèbe Jean-François Gerard 《Comptes rendus biologies》2012,335(12):735-743
We studied the ranging behaviour and spatial relationships between seven roe deer during more than 4 years in a partly wooded 14.2-ha enclosure. The animals (three young males, four adult females) were monitored with GPS telemetry collars. As expected, the surface area and overlap of the males’ bimonthly ranges decreased, and the distance between their arithmetic centres increased, as they became adult and, for two of them, territorial. Unexpectedly, females also tended to space out, the surface area and overlap of their bimonthly ranges being minimal in May to June, i.e. during the birth period. The distance between their arithmetic centres reached its maximum at the same time. Overlap between females’ ranges was consistently lower than those between males and females’ ranges, or between 1-year old males’ ranges. Our results raise the questions of female seasonal territoriality and of independence of the spacing systems of the two sexes in roe deer. 相似文献
15.
Derelle E Ferraz C Escande ML Eychenié S Cooke R Piganeau G Desdevises Y Bellec L Moreau H Grimsley N 《PloS one》2008,3(5):e2250
Large DNA viruses are ubiquitous, infecting diverse organisms ranging from algae to man, and have probably evolved from an ancient common ancestor. In aquatic environments, such algal viruses control blooms and shape the evolution of biodiversity in phytoplankton, but little is known about their biological functions. We show that Ostreococcus tauri, the smallest known marine photosynthetic eukaryote, whose genome is completely characterized, is a host for large DNA viruses, and present an analysis of the life-cycle and 186,234 bp long linear genome of OtV5. OtV5 is a lytic phycodnavirus which unexpectedly does not degrade its host chromosomes before the host cell bursts. Analysis of its complete genome sequence confirmed that it lacks expected site-specific endonucleases, and revealed the presence of 16 genes whose predicted functions are novel to this group of viruses. OtV5 carries at least one predicted gene whose protein closely resembles its host counterpart and several other host-like sequences, suggesting that horizontal gene transfers between host and viral genomes may occur frequently on an evolutionary scale. Fifty seven percent of the 268 predicted proteins present no similarities with any known protein in Genbank, underlining the wealth of undiscovered biological diversity present in oceanic viruses, which are estimated to harbour 200Mt of carbon. 相似文献
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17.
Box C/D RNA guides for the ribose methylation of archaeal tRNAs. The tRNATrp intron guides the formation of two ribose-methylated nucleosides in the mature tRNATrp 下载免费PDF全文
Batrice Clouet dOrval Marie-Line Bortolin Christine Gaspin Jean-Pierre Bachellerie 《Nucleic acids research》2001,29(22):4518-4529
Following a search of the Pyrococcus genomes for homologs of eukaryotic methylation guide small nucleolar RNAs, we have experimentally identified in Pyrococcus abyssi four novel box C/D small RNAs predicted to direct 2′-O-ribose methylations onto the first position of the anticodon in tRNALeu(CAA), tRNALeu(UAA), elongator tRNAMet and tRNATrp, respectively. Remarkably, one of them corresponds to the intron of its presumptive target, pre-tRNATrp. This intron is predicted to direct in cis two distinct ribose methylations within the unspliced tRNA precursor, not only onto the first position of the anticodon in the 5′ exon but also onto position 39 (universal tRNA numbering) in the 3′ exon. The two intramolecular RNA duplexes expected to direct methylation, which both span an exon–intron junction in pre-tRNATrp, are phylogenetically conserved in euryarchaeotes. We have experimentally confirmed the predicted guide function of the box C/D intron in halophile Haloferax volcanii by mutagenesis analysis, using an in vitro splicing/RNA modification assay in which the two cognate ribose methylations of pre-tRNATrp are faithfully reproduced. Euryarchaeal pre-tRNATrp should provide a unique system to further investigate the molecular mechanisms of RNA-guided ribose methylation and gain new insights into the origin and evolution of the complex family of archaeal and eukaryotic box C/D small RNAs. 相似文献
18.
Banana streak virus (BSV) is a plant dsDNA pararetrovirus (family Caulimoviridae, genus badnavirus). Although integration is not an essential step in the BSV replication cycle, the nuclear genome of banana (Musa sp.) contains BSV endogenous pararetrovirus sequences (BSV EPRVs). Some BSV EPRVs are infectious by reconstituting a functional
viral genome. Recent studies revealed a large molecular diversity of episomal BSV viruses (i.e., nonintegrated) while others
focused on BSV EPRV sequences only. In this study, the evolutionary history of badnavirus integration in banana was inferred from phylogenetic relationships between BSV and BSV EPRVs. The relative evolution rates
and selective pressures (dN/dS ratio) were also compared between endogenous and episomal viral sequences. At least 27 recent independent integration events
occurred after the divergence of three banana species, indicating that viral integration is a recent and frequent phenomenon.
Relaxation of selective pressure on badnaviral sequences that experienced neutral evolution after integration in the plant
genome was recorded. Additionally, a significant decrease (35%) in the EPRV evolution rate was observed compared to BSV, reflecting
the difference in the evolution rate between episomal dsDNA viruses and plant genome. The comparison of our results with the
evolution rate of the Musa genome and other reverse-transcribing viruses suggests that EPRVs play an active role in episomal BSV diversity and evolution. 相似文献
19.
Young-Hyun Han Marie-Line Garron Hye-Yeon Kim Wan-Seok Kim Zhenqing Zhang Kyeong-Seok Ryu David Shaya Zhongping Xiao Chaejoon Cheong Yeong Shik Kim Robert J. Linhardt Young Ho Jeon Miroslaw Cygler 《The Journal of biological chemistry》2009,284(49):34019-34027
Heparin lyase I (heparinase I) specifically depolymerizes heparin, cleaving the glycosidic linkage next to iduronic acid. Here, we show the crystal structures of heparinase I from Bacteroides thetaiotaomicron at various stages of the reaction with heparin oligosaccharides before and just after cleavage and product disaccharide. The heparinase I structure is comprised of a β-jellyroll domain harboring a long and deep substrate binding groove and an unusual thumb-resembling extension. This thumb, decorated with many basic residues, is of particular importance in activity especially on short heparin oligosaccharides. Unexpected structural similarity of the active site to that of heparinase II with an (α/α)6 fold is observed. Mutational studies and kinetic analysis of this enzyme provide insights into the catalytic mechanism, the substrate recognition, and processivity. 相似文献
20.
Marie-Line Peyot Joshua P. Gray Julien Lamontagne Peter J. S. Smith George G. Holz S. R. Murthy Madiraju Marc Prentki Emma Heart 《PloS one》2009,4(7)