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991.
The subcellular localization of specific mRNAs is a widespread mechanism for regulating gene expression. In Xenopus oocytes microtubules are required for localization of Vg1 mRNA to the vegetal cortex during the late RNA localization pathway. The factors that mediate microtubule-based RNA transport during the late pathway have been elusive. Here we show that heterotrimeric kinesin II becomes enriched at the vegetal cortex of stage III/IV Xenopus oocytes concomitant with the localization of endogenous Vg1 mRNA. In addition, expression of a dominant negative mutant peptide fragment or injection of a function-blocking antibody, both of which impair the function of heterotrimeric kinesin II, block localization of Vg1 mRNA. We also show that exogenous Vg1 RNA or Xcat-2, another RNA that can use the late pathway, recruits endogenous kinesin II to the vegetal pole and colocalizes with it at the cortex. These data support a model in which kinesin II mediates the transport of specific RNA complexes destined for the vegetal cortex. 相似文献
992.
Hermjakob H Montecchi-Palazzi L Bader G Wojcik J Salwinski L Ceol A Moore S Orchard S Sarkans U von Mering C Roechert B Poux S Jung E Mersch H Kersey P Lappe M Li Y Zeng R Rana D Nikolski M Husi H Brun C Shanker K Grant SG Sander C Bork P Zhu W Pandey A Brazma A Jacq B Vidal M Sherman D Legrain P Cesareni G Xenarios I Eisenberg D Steipe B Hogue C Apweiler R 《Nature biotechnology》2004,22(2):177-183
993.
Brand JM Frohn C Cziupka K Brockmann C Kirchner H Luhm J 《European cytokine network》2004,15(2):99-104
994.
Milhiet PE Dosset P Giocondi MC Le Grimellec C 《Journal de la Société de Biologie》2004,198(2):169-174
The atomic force microscope (AFM) allows to explore the surface of biological samples bathed in physiological solutions, with vertical and horizontal resolutions ranging from nanometers to angstr?ms. Complex biological structures as well as single molecules can be observed and recent examples of the possibilities offered by the AFM in the imaging of intact cells, isolated membranes, membrane model systems and single molecules are discussed in this review. Applications where the AFM tip is used as a nanotool to manipulate biomolecules and to determine intra and intermolecular forces from single molecules are also presented. 相似文献
995.
Genome size displays an important variability between species without any direct link to complexity. This paradox, so-called "C value paradox", now becomes understood as resulting from a differential abundance of numerous repeated sequences, among which transposable elements. Genomes indeed contain a important proportion of such sequences (95 % of DNA in man, about 45 % of which are transposable elements, up to 99 % of DNA in some plants). While most investigations until now are focalized on genes or coding sequences, which thus represent a small part of the genome, more attention now is dedicated on so-called non-coding sequences. Transposable elements, which are capable of moving around in genomes, inducing mutations, chromosomal rearrangements, gene expression regulations, thus appear as major actors in diversity and evolution. We present here a brief review of the most prominent acquisition in this expanding domain. 相似文献
996.
SUMMARY: QDist is a program for computing the quartet distance between two unrooted trees, i.e. the number of quartet topology differences between the trees, where a quartet topology is the topological subtree induced by four species. The program is based on an algorithm with running time O(n log2 n), which makes it practical to compare large trees. Available under GNU license. AVAILABILITY: http://www.birc.dk/Software/QDist 相似文献
997.
SUMMARY: LumberJack is a phylogenetic tool intended to serve two purposes: to facilitate sampling treespace to find likely tree topologies quickly, and to map phylogenetic signal onto regions of an alignment in a revealing way. LumberJack creates non-random jackknifed alignments by progressively sliding a window of omission along the alignment. A neighbor-joining tree is built from the full alignment and from each jackknifed alignment, and then the likelihood for each topology (given the original full alignment) is calculated. To determine whether any of the topologies generated is significantly more likely than the others, Kishino-Hasegawa, Shimodaira-Hasegawa and ELW tests are implemented. Availability and SUPPLEMENTARY INFORMATION: http://www.plantbio.uga.edu/~russell/software.html 相似文献
998.
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1000.
Phylogenomics of the reproductive parasite Wolbachia pipientis wMel: a streamlined genome overrun by mobile genetic elements
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Wu M Sun LV Vamathevan J Riegler M Deboy R Brownlie JC McGraw EA Martin W Esser C Ahmadinejad N Wiegand C Madupu R Beanan MJ Brinkac LM Daugherty SC Durkin AS Kolonay JF Nelson WC Mohamoud Y Lee P Berry K Young MB Utterback T Weidman J Nierman WC Paulsen IT Nelson KE Tettelin H O'Neill SL Eisen JA 《PLoS biology》2004,2(3):E69
The complete sequence of the 1,267,782 bp genome of Wolbachia pipientis wMel, an obligate intracellular bacteria of Drosophila melanogaster, has been determined. Wolbachia, which are found in a variety of invertebrate species, are of great interest due to their diverse interactions with different hosts, which range from many forms of reproductive parasitism to mutualistic symbioses. Analysis of the wMel genome, in particular phylogenomic comparisons with other intracellular bacteria, has revealed many insights into the biology and evolution of wMel and Wolbachia in general. For example, the wMel genome is unique among sequenced obligate intracellular species in both being highly streamlined and containing very high levels of repetitive DNA and mobile DNA elements. This observation, coupled with multiple evolutionary reconstructions, suggests that natural selection is somewhat inefficient in wMel, most likely owing to the occurrence of repeated population bottlenecks. Genome analysis predicts many metabolic differences with the closely related Rickettsia species, including the presence of intact glycolysis and purine synthesis, which may compensate for an inability to obtain ATP directly from its host, as Rickettsia can. Other discoveries include the apparent inability of wMel to synthesize lipopolysaccharide and the presence of the most genes encoding proteins with ankyrin repeat domains of any prokaryotic genome yet sequenced. Despite the ability of wMel to infect the germline of its host, we find no evidence for either recent lateral gene transfer between wMel and D. melanogaster or older transfers between Wolbachia and any host. Evolutionary analysis further supports the hypothesis that mitochondria share a common ancestor with the α-Proteobacteria, but shows little support for the grouping of mitochondria with species in the order Rickettsiales. With the availability of the complete genomes of both species and excellent genetic tools for the host, the wMel–D. melanogaster symbiosis is now an ideal system for studying the biology and evolution of Wolbachia infections. 相似文献