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81.
An amino-terminal domain of the hepatitis C virus NS3 protease is essential for interaction with NS4A. 总被引:22,自引:16,他引:6
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Hepatitis C virus (HCV) genomic RNA is translated into a large polyprotein that is processed into structural and nonstructural proteins. Processing at the N termini of several nonstructural proteins requires sequences contained in both NS3 and NS4A. NS3 contains a serine protease, whereas the function of NS4A in proteolysis is yet to be determined. By using the vaccinia virus-T7 hybrid expression system to transiently express HCV polypeptides in HeLa cells, we studied the effect of several N-terminal and C-terminal deletions of HCV NS3 on the processing activity at all the downstream cleavage sites. In this way, we have delineated the minimal domain of NS3 required for the serine protease activity associated with this protein. In addition, we demonstrate the formation of a stable complex between NS3 and NS4A: analysis of the deletion mutants reveals a region at the N terminus of NS3 that is necessary for both complex formation and modulation of the proteolytic activity by NS4A but not for the NS4A-independent serine protease activity of NS3. 相似文献
82.
Detlef Michel Hans Hartings Simona Lanzini Manuela Michel Mario Motto Giorgia Romina Riboldi Francesco Salamini Hans-Peter Döring 《Molecular & general genetics : MGG》1995,248(3):287-292
Eight independently isolated unstable alleles of theOpaque2 (O2) locus were analysed genetically and at the DNA level. The whole series of mutations was isolated from a maize strain carrying a wild-typeO2 allele and the transposable elementActivator (Ac) at thewx-m7 allele. Previous work with another unstable allele of the same series has shown that it was indeed caused by the insertion of anAc element. Unexpectedly, the remaining eight mutations were not caused by the designatedAc element, but by other insertions that are structurally similar or identical to one of two different autonomous transposable elements. Six mutations were caused by the insertion of a transposable element of theEnhancer/Suppressor-Mutator (En/Spm) family. Two mutations were the result of the insertion of a transposable element of theBergamo (Bg) family. Genetic tests carried out with plants carrying the unstable mutations demonstrated that all were caused by the insertion of an autonomous transposable element. 相似文献
83.
Khalid Meksem Dario Leister Johan Peleman Marc Zabeau Francesco Salamini Christiane Gebhardt 《Molecular & general genetics : MGG》1995,249(1):74-81
The R1 allele confers on potato a race-specific resistance to Phytophthora infestans. The corresponding genetic locus maps on chromosome V in a region in which several other resistance genes are also located. As part of a strategy for cloning R1, a high-resolution genetic map was constructed for the segment of chromosome V that is bordered by the RFLP loci GP21 and GP179 and includes the R1 locus. Bulked segregant analysis and markers based on amplified fragment length polymorphisms (AFLP markers) were used to select molecular markers closely linked to R1. Twenty-nine of approximately 3200 informative AFLP loci displayed linkage to the R1 locus. Based on the genotypic analysis of 461 gametes, eight loci mapped within the GP21–GP179 interval. Two of those could not be seperated from R1 by recombination. For genotyping large numbers of plants with respect to the flanking markers GP21 and GP179 PCR based assays were also developed which allowed marker-assisted selection of plants with genotypes Rr and rr and of recombinant plants. 相似文献
84.
Giuseppe Barbiero Federica Duranti Gabriella Bonelli Joseph S. Amenta Francesco M. Baccino 《Experimental cell research》1995,217(2)
Treatment with VP-16 (1-50 μM) or excess thymidine (5 mM) caused a block of L cells at different steps in their progression through the replicative cycle. The arrest was followed by an asynchronous process of cell death that conformed to criteria for apoptosis. Careful monitoring of this process in the whole cell population by flow cytometry showed a virtual absence of necrosis, an increase in side light scattering, followed by the occurrence of a population with subdiploid DNA fluorescence as well as reduced forward and side light seattering. The development of apoptosis required sufficient time and adequate ion gradients in the cells. By the combined use of flow cytometry and fluorescence microscopy data were obtained suggesting that (i) intracellular free Ca2+ and pH and/or their drug-induced alterations had to be adequately controlled for the apoptotic process to evolve; (ii) mitochondria were compromised earlier than the plasma membrane or lysosomes; and (iii) K+ extrusion possibly played a role in the final loss of cell volume. Interfering with the control of ion gradients and/or their changes in drug-treated cells resulted in cell death by necrosis. 相似文献
85.
Mariëtte P. C. van de Corput Roeland W. Dirks Wouter W. Wiegant Joop Wiegant Klaus Mühlegger A. K. Raap 《Histochemistry and cell biology》1997,108(4-5):359-364
Oestradiol has been conjugated to allylamine-dUTP with an 11-atom spacer to allow enzymatic incorporation of the label into
DNA sequences. In a comparative DNA and mRNA FISH study we have used DNA probes that were either labelled with digoxigenin,
biotin or oestradiol. Results show that oestradiol-labelled probes can detect DNA and RNA sequences in FISH equally well as
digoxigenin- and biotin-labelled probes. Further, no crossreactivity between the various hapten-specific antibodies and the
three haptens were observed. Binding of the rabbit anti-oestradiol antibody to endogenous oestrogen in various tissues was
not observed under the conditions tested. In view of the increasing demands for multi-colour DNA and mRNA FISH applications,
oestradiol is a welcome addition to the collection of haptens employed in FISH.
Accepted 20 June 1997 相似文献
86.
87.
The role of nitrogen as a factor controllingphytoplankton biomass was studied in nutrientenrichment incubations in the laboratory
using waterfrom pelagic region of two mesotrophic lakes ineastern Finland, Lake Kallavesi (in year 1994) andLake Juurusvesi
(in year 1995). We used differentcombinations of phosphorus and nitrogen additions ina total of eight experiments. Furthermore,
we includedDaphnia grazing treatment to the experimentaldesign in Lake Juurusvesi experiments. The nitrogentreatments did
not increase chlorophyll aconcentration in any of the experiments compared withthe controls. Chlorophyll a content was highestin
those nutrient treatments where phosphorus wasadded with or without nitrogen. Daphnia grazingdecreased chlorophyll a concentration
comparedwith non-grazed treatments. In some cases grazing alsocaused higher ammonium concentrations. Theseexperiments, as
well as the nutrient ratio of the lakewater used, suggest that phosphorus is likely tocontrol the amount of phytoplankton
biomass.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
Spontaneous Cell Fusion in Macrophage Cultures Expressing High Levels of the P2Z/P2X7 Receptor 总被引:6,自引:0,他引:6
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Paola Chiozzi Juana M. Sanz Davide Ferrari Simonetta Falzoni Arrigo Aleotti Gary N. Buell Ginetta Collo Francesco Di Virgilio 《The Journal of cell biology》1997,138(3):697-706
Mouse and human macrophages express a plasma membrane receptor for extracellular ATP named P2Z/P2X7. This molecule, recently cloned, is endowed with the intriguing property of forming an aqueous pore that allows transmembrane fluxes of hydrophylic molecules of molecular weight below 900. The physiological function of this receptor is unknown. In a previous study we reported experiments suggesting that the P2Z/P2X7 receptor is involved in the formation of macrophage-derived multinucleated giant cells (MGCs; Falzoni, S., M. Munerati, D. Ferrari, S. Spisani, S. Moretti, and F. Di Virgilio. 1995. J. Clin. Invest. 95:1207– 1216). We have selected several clones of mouse J774 macrophages that are characterized by either high or low expression of the P2Z/P2X7 receptor and named these clones P2Zhyper or P2Zhypo, respectively. P2Zhyper, but not P2Zhypo, cells grown to confluence in culture spontaneously fuse to form MGCs. As previously shown for human macrophages, fusion is inhibited by the P2Z/P2X7 blocker oxidized ATP. MGCs die shortly after fusion through a dramatic process of cytoplasmic sepimentation followed by fragmentation. These observations support our previous hypothesis that the P2Z/P2X7 receptor is involved in macrophage fusion. 相似文献
89.
Francesco Frati Chris Simon Jack Sullivan David L. Swofford 《Journal of molecular evolution》1997,44(2):145-158
The sequence of the mitochondrial COII gene has been widely used to estimate phylogenetic relationships at different taxomonic
levels across insects. We investigated the molecular evolution of the COII gene and its usefulness for reconstructing phylogenetic
relationships within and among four collembolan families. The collembolan COII gene showed the lowest A + T content of all
insects so far examined, confirming that the well-known A + T bias in insect mitochondrial genes tends to increase from the
basal to apical orders. Fifty-seven percent of all nucleotide positions were variable and most of the third codon positions
appeared free to vary. Values of genetic distance between congeneric species and between families were remarkably high; in
some cases the latter were higher than divergence values between other orders of insects. The remarkably high divergence levels
observed here provide evidence that collembolan taxa are quite old; divergence levels among collembolan families equaled or
exceeded divergences among pterygote insect orders. Once the saturated third-codon positions (which violated stationarity
of base frequencies) were removed, the COII sequences contained phylogenetic information, but the extent of that information
was overestimated by parsimony methods relative to likelihood methods. In the phylogenetic analysis, consistent statistical
support was obtained for the monophyly of all four genera examined, but relationships among genera/families were not well
supported. Within the genus Orchesella, relationships were well resolved and agreed with allozyme data. Within the genus Isotomurus, although three pairs of populations were consistently identified, these appeared to have arisen in a burst of evolution from
an earlier ancestor. Isotomurus italicus always appeared as basal and I. palustris appeared to harbor a cryptic species, corroborating allozyme data.
Received: 12 January 1996 / Accepted: 10 August 1996 相似文献
90.
Pietro Paolo Fanciullt Miguel Gaju Carmen Bach Francesco Frati 《Biological journal of the Linnean Society. Linnean Society of London》1997,62(4):533-551
Different species of the bristletail genus Lepismachilis were collected in 14 localities in Italy and Spain and an allozyme electrophoretic survey was carried out to estimate the degree of genetic variability and differentiation at intra- and interspecific levels. Four morphological species were initially identified (L osellai, L. y-signata, L. affinis, L. targionii), but the electrophoretic analysis demonstrated the presence of two additional species among the individuals of L. targionii (Lepismachilis spl and sp2). The validity of these species and their differentiation from L targionii were demonstrated by the fixation of alternative allelic patterns at several loci (7 in Lepismachilis spl and 8 in Lepismachilis sp2), coupled with fixed, previously undetected, morphological differences. In addition, Lepismachilis sp2 was sympatric with L. targionii in three collecting sites, where the fixation of alternative allelic patterns unequivocally demonstrated reproductive isolation. Genetic variability did not seem to be correlated with local ecological factors, and differences between species should rather be explained by different historical factors. Low levels of gene flow, estimated with two different indirect methods, were observed in L. targionii and L. y-signata, and were due to high levels of structuring among populations. Genetic differentiation among conspecific populations was not correlated to their geographical arrangement and the presence of loci fixed for different alleles among them suggested that stochastic factors (such as genetic drift) may have played a role in determining genetic differentiation of geographically isolated populations. Genetic divergence values indicated that the six species are well differentiated and allozyme profiles were diagnostic for all of them. On the other hand, allozyme data did not provide adequate information to resolve evolutionary relationships among the species, nor did they confirm the validity of the two subgenera (Lepismachilis and Berlesilis) in which the genus Lepismachilis is traditionally divided. 相似文献