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1.
We have evaluated codon usage bias in Drosophila histone genes and have
obtained the nucleotide sequence of a 5,161-bp D. hydei histone gene repeat
unit. This repeat contains genes for all five histone proteins (H1, H2a,
H2b, H3, and H4) and differs from the previously reported one by a second
EcoRI site. These D. hydei repeats have been aligned to each other and to
the 5.0-kb (i.e., long) and 4.8-kb (i.e., short) histone repeat types from
D. melanogaster. In each species, base composition at synonymous sites is
similar to the average genomic composition and approaches that in the small
intergenic spacers of the histone gene repeats. Accumulation of synonymous
changes at synonymous sites after the species diverged is quite high. Both
of these features are consistent with the relatively low codon usage bias
observed in these genes when compared with other Drosophila genes. Thus,
the generalization that abundantly expressed genes in Drosophila have high
codon bias and low rates of silent substitution does not hold for the
histone genes.
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2.
In Gram-positive bacteria proteins are displayed on the cell surface using sortase enzymes. These cysteine transpeptidases join proteins bearing an appropriate sorting signal to strategically positioned amino groups on the cell surface. Working alone, or in concert with other enzymes, sortases either attach proteins to the cross-bridge peptide of the cell wall or they link proteins together to form pili. Because surface proteins play a fundamental role in microbial physiology and are frequently virulence factors, sortase enzymes have been intensely studied since their discovery a little more than a decade ago. Based on their primary sequences and functions sortases can be partitioned into distinct families called class A to F enzymes. Most bacteria elaborate their surfaces using more than one type of sortase that function non-redundantly by recognizing unique sorting signals within their protein substrates. Here we review what is known about the functions of these enzymes and the molecular basis of catalysis. Particular emphasis is placed on 'pilin' specific class C sortases that construct structurally complex pili. Exciting new data have revealed that these enzymes are amazingly promiscuous in the substrates that they can employ and that there is a startling degree of diversity in their mechanism of action. We also review recent data that suggest that sortases are targeted to specific sites on the cell surface where they work with other sortases and accessory factors to properly function. 相似文献
3.
In the absence of suitable rodent animal models for Plasmodium falciparum malaria, the efficacy testing of asexual blood-stage vaccine candidates in Aotus nancymaae represents a tool to select between different formulations before conducting expensive human clinical trials. CpG oligonucleotides (ODN) specifically promote the production of pro-inflammatory and Th1-type cytokines and they enhance the immunogenicity of co-administered antigens. Toll like receptor 9 (TLR-9) binds directly and sequence-specifically to single-stranded un-methylated CpG-DNA mediating the biological effects of CpG ODN. We cloned and functionally characterised the TLR-9 cDNA of A. nancymaae. The cDNA encompassed 3,099 bp predicted to code for 1,032 amino acid residues. Results of homology searches to human TLR-9 suggested that the receptor is 93 and 94% identical at the nucleotide and amino acid sequence levels, respectively. Stimulation of splenocytes of A. nancymaae with CpG ODN resulted in proliferative responses in all animals analysed. FACS analysis of cultures incubated with CpG ODN 2006 indicated that the B cell marker CD20 was up-regulated consistent with B cell activation. The high level of sequence conservation of Aona-TLR-9 reinforces the suitability of A. nancymaae as animal model for malaria subunit vaccine development.The nucleotide sequence has been submitted to the GenBank nucleotide sequence database under the accession number AY788894. 相似文献
4.
Inducible and neuron-specific gene expression in the adult mouse brain with the rtTA2S-M2 system 总被引:5,自引:0,他引:5
Michalon A Koshibu K Baumgärtel K Spirig DH Mansuy IM 《Genesis (New York, N.Y. : 2000)》2005,43(4):205-212
To achieve inducible and reversible gene expression in the adult mouse brain, we exploited an improved version of the tetracycline-controlled transactivator-based system (rtTA2(S)-M2, rtTA2 hereafter) and combined it with the forebrain-specific CaMKIIalpha promoter. Several independent lines of transgenic mice carrying the CaMKIIalpha promoter-rtTA2 gene were generated and examined for anatomical profile, doxycycline (dox)-dependence, time course, and reversibility of gene expression using several lacZ reporter lines. In two independent rtTA2-expressing lines, dox-treatment in the diet induced lacZ reporter expression in neurons of several forebrain structures including cortex, striatum, hippocampus, amygdala, and olfactory bulb. Gene expression was dose-dependent and was fully reversible. Further, a similar pattern of expression was obtained in three independent reporter lines, indicating the consistency of gene expression. Transgene expression could also be activated in the developing brain (P0) by dox-treatment of gestating females. These new rtTA2-expressing mice allowing inducible and reversible gene expression in the adult or developing forebrain represent useful models for future genetic studies of brain functions. 相似文献
5.
Global warming will lead to earlier beginnings and prolongation of growing seasons in temperate regions and will have pronounced effects on phenology and life-history adaptation in many species. These changes were not easy to simulate for actual phenologies because of the rudimentary temporal (season) and spatial (regional) resolution of climate model projections. We investigate the effect of climate change on the regional incidence of a pest insect with nearly worldwide distribution and very high potential for adaptation to season length and temperature--the Codling Moth, Cydia pomonella. Seasonal and regional climate change signals were downscaled to the hourly temporal scale of a pest phenology model and the spatial scale of pest habitats using a stochastic weather generator operating at daily scale in combination with a re-sampling approach for simulation of hourly weather data. Under future conditions of increased temperatures (2045-2074), the present risk of below 20% for a pronounced second generation (peak larval emergence) in Switzerland will increase to 70-100%. The risk of an additional third generation will increase from presently 0-2% to 100%. We identified a significant two-week shift to earlier dates in phenological stages, such as overwintering adult flight. The relative extent (magnitude) of first generation pupae and all later stages will significantly increase. The presence of first generation pupae and later stages will be prolonged. A significant decrease in the length of overlap of first and second generation larval emergence was identified. Such shifts in phenology may induce changes in life-history traits regulating the life cycle. An accordingly life-history adaptation in photoperiodic diapause induction to shorter day-length is expected and would thereby even more increase the risk of an additional generation. With respect to Codling Moth management, the shifts in phenology and voltinism projected here will require adaptations of plant protection strategies to maintain their sustainability. 相似文献
6.
7.
Stefan Kunz Marianne Spirig Claudia Ginsburg Andrea Buchstaller Philipp Berger Rainer Lanz Christoph Rader Lorenz Vogt Beat Kunz Peter Sonderegger 《The Journal of cell biology》1998,143(6):1673-1690
Neural cell adhesion molecules composed of immunoglobulin and fibronectin type III-like domains have been implicated in cell adhesion, neurite outgrowth, and fasciculation. Axonin-1 and Ng cell adhesion molecule (NgCAM), two molecules with predominantly axonal expression exhibit homophilic interactions across the extracellular space (axonin- 1/axonin-1 and NgCAM/NgCAM) and a heterophilic interaction (axonin-1–NgCAM) that occurs exclusively in the plane of the same membrane (cis-interaction). Using domain deletion mutants we localized the NgCAM homophilic binding in the Ig domains 1-4 whereas heterophilic binding to axonin-1 was localized in the Ig domains 2-4 and the third FnIII domain. The NgCAM–NgCAM interaction could be established simultaneously with the axonin-1–NgCAM interaction. In contrast, the axonin-1–NgCAM interaction excluded axonin-1/axonin-1 binding. These results and the examination of the coclustering of axonin-1 and NgCAM at cell contacts, suggest that intercellular contact is mediated by a symmetric axonin-12/NgCAM2 tetramer, in which homophilic NgCAM binding across the extracellular space occurs simultaneously with a cis-heterophilic interaction of axonin-1 and NgCAM. The enhanced neurite fasciculation after overexpression of NgCAM by adenoviral vectors indicates that NgCAM is the limiting component for the formation of the axonin-12/NgCAM2 complexes and, thus, neurite fasciculation in DRG neurons. 相似文献
8.
Tiaden A Spirig T Weber SS Brüggemann H Bosshard R Buchrieser C Hilbi H 《Cellular microbiology》2007,9(12):2903-2920
Legionella pneumophila is an opportunistic human pathogen that replicates within environmental amoebae including Acanthamoeba castellanii and Dictyostelium discoideum. The Icm/Dot type IV secretion system promotes phagocytosis and intracellular replication of L. pneumophila in an endoplasmic reticulum-derived 'Legionella-containing vacuole' (LCV). L. pneumophila adopts a biphasic life cycle consisting of a replicative growth phase and a transmissive (stationary) phase, the latter of which is characterized by the preferential expression of genes required for motility and virulence. A bioinformatic analysis of the L. pneumophila genome revealed a gene cluster homologous to the Vibrio cholerae cqsAS genes, encoding a putative quorum sensing autoinducer synthase (lqsA) and a sensor kinase (lqsS), which flank a novel response regulator (lqsR). We report here that an L. pneumophila lqsR deletion mutant grew in broth with the same rate as wild-type bacteria, but entered the replicative growth phase earlier. Overexpression of lqsR led to an elongated morphology of the bacteria. The lqsR mutant strain was found to be more salt-resistant and impaired for intracellular growth in A. castellanii, D. discoideum and macrophages, formation of the ER-derived LCV and toxicity. Moreover, L. pneumophila lacking LqsR, as well as strains lacking the stationary sigma factor RpoS or the two-component response regulator LetA, were phagocytosed less efficiently by A. castellanii, D. discoideum or macrophages. The expression of lqsR was dependent on RpoS and, to a lesser extent, also on LetA. DNA microarray experiments revealed that lqsR regulates the expression of genes involved in virulence, motility and cell division, consistent with a role for LqsR in the transition from the replicative to the transmissive (virulent) phase. Our findings indicate that LqsR is a novel pleiotropic regulator involved in RpoS- and LetA-controlled interactions of L. pneumophila with phagocytes. 相似文献
9.
10.
Fucose is a major constituent of the protein- and lipid-linked glycans of
the various life-cycle stages of schistosomes. These fucosylated glycans
are highly antigenic and seem to play a role in the pathology of
schistosomiasis. In this article we describe the identification and
characterization of two fucosyltransferases (FucTs) in cercariae of the
avian schistosome Trichobilharzia ocellata, a GDP-Fuc:[Galbeta1--
>4]GlcNAcbeta-R alpha1-->3-FucT and a novel GDP-Fuc:Fucalpha-R
alpha1-- >2-FucT. Triton X-100 extracts of cercariae were assayed for
FucT activity using a variety of acceptor substrates. Type 1 chain
(Galbeta1- ->3GlcNAc) based compounds were poor acceptors, whereas those
based on a type 2 chain (Galbeta1-->4GlcNAc), whether
alpha2'-fucosylated, alpha3'-sialylated, or unsubstituted, and whether
present as oligosaccharide or contained in a glycopeptide or glycoprotein,
all served as acceptor substrates. In this respect the schistosomal alpha3-
FucT resembles human FucT V and VI rather than other known FucTs. N-
ethylmaleimide, an inhibitor of several human FucTs, had no effect on the
activity of the schistosomal alpha3-FucT, whereas GDP-beta-S was strongly
inhibitory. Large scale incubations were carried out with
Galbeta1-->4GlcNAc, GalNAcbeta1-->4GlcNAcbeta-O -(CH2)8COOCH3 and
Fucalpha1-->3GlcNAcbeta1-->2Man as acceptor substrates and the
products of the incubations were isolated using a sequence of
chromatographic techniques. By methylation analysis and 2D-TOCSY and
ROESY1H-NMR spectroscopy the products formed were shown to be Galbeta1--
>4[Fucalpha1-->2Fucalpha1-->3]GlcNAc,
GalNAcbeta1-->4[Fucalpha1-- >2Fucalpha1-->3]GlcNAcbe
ta-O-(CH2)8COOCH3, and Fucalpha1-->2Fucalpha1--
>3GlcNAcbeta1-->2Man, respectively. It is concluded that the alpha2-
FucT and alpha3-FucT are involved in the biosynthesis of the (oligomeric)
Lewisx sequences and the Fucalpha1-->2Fucalpha1-->3GlcNAc structural
element that have been described on schistosomal glycoconjugates.
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