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Jun Yu

Publications and source records attributed to Jun Yu.

At least 145 records · Page 8Linked to original sources
PubMed2003

The mitochondrial genome of the thermal dimorphic fungus Penicillium marneffei is more closely related to those of molds than yeasts.

We report the complete sequence of the mitochondrial genome of Penicillium marneffei, the first complete mitochondrial DNA sequence of a thermal dimorphic fungus. This 35 kb mitochondrial genome contains the genes encoding ATP synthase subunits 6, 8, and 9 (atp6, atp8, and atp9), cytochrome oxidase subunits I, II, and III (cox1, cox2, and cox3), apocytochrome b (cob), reduced nicotinamide adenine dinucleotide ubiquinone oxireductase subunits (nad1, nad2, nad3, nad4, nad4L, nad5, and nad6), ribosomal protein of the small ribosomal subunit (rps), 28 tRNAs, and small and large ribosomal RNAs. Analysis of gene contents, gene orders, and gene sequences revealed that the mitochondrial genome of P. marneffei is more closely related to those of molds than yeasts.

Base Sequence↗
PubMed2003

Identification and characterization of simple sequence repeats in the genomes of Shigella species.

A variety of simple sequence repeats (SSRs) have been identified in the genome of Shigella flexneri serotype 2a (strain Sf301), an enteric pathogen that causes bacillary dysentery in man. The distribution of SSRs, with unit length ranging from 1 to 9 nucleotides, was biased in different regions of the genome. The tri-, tetra- and hexanucleotide SSRs prevailed in the coding regions while the mono- and dinucleotide SSRs were more common in the noncoding regions. Many intergenic SSRs are less than 30 bp away from the downstream open reading frames (ORFs), suggesting a potential role in transcriptional regulation. To study polymorphism of SSRs, we compared 17 coding-region SSRs from strain Sf301 with the corresponding sequences from 23 other strains of four Shigella species. Five chromosomal loci were found to be polymorphic, of which those from S. flexneri strains were most variable. Particularly interesting is the C5-1 locus in the coding sequence of the hcaD gene encoding a subunit of ferredoxin reductase. Depending on the insertion of variable numbers of the unit sequence (CGCAG), the Shigella hcaD genes can encode truncated products due to premature stop codons or frame shifts, or products with extended core alpha helices that leads to radical alterations in the predicted tertiary structure. Hence, SSRs may serve as genotyping markers for epidemiological investigations, and may offer insights into evolutionary adaptation of the pathogens.

Amino Acid Sequence↗
PubMed2003

Heat shock protein 90 and tyrosine kinase regulate eNOS NO* generation but not NO* bioactivity.

An increase in the association of heat shock protein 90 (HSP90) with endothelial nitric oxide (NO) synthase (eNOS) is well recognized for increasing NO (NO*) production. Despite the progress in this field, the mechanisms by which HSP90 modulates eNOS remain unclear due, in part, to the fact that geldanamycin (GA) redox cycles to generate superoxide anion (O(2)(-*) and the fact that inhibiting HSP90 with GA or radicicol (RAD) destabilizes tyrosine kinases that rely on the chaperone for maturation. In this report, we determine the extent to which these side effects alter vascular and endothelial cell function in physiologically relevant systems and in cultured endothelial cells. Vascular endothelial growth factor (VEGF)-stimulated vascular permeability, as measured by Evans blue leakage in the ears of male Swiss mice in vivo, and acetylcholine-induced vasodilation of isolated, pressurized mandibular arterioles from male C57BL6 mice ex vivo were attenuated by N(omega)-nitro-L-arginine methyl ester (L-NAME), GA, and RAD. Z-1[N-(2-aminoethyl)-N-(2-ammonoethyl)amino]diazen-1-ium-1,2-dioate (DETA-NONOate), a slow releasing NO. donor, increased vasodilation of arterioles pretreated with GA, RAD, and L-NAME equally well except at 10(-5) M, the highest concentration used, where vasodilation was greater in pressurized arterioles treated with L-NAME than in arterioles pretreated with GA or RAD alone. Both GA and RAD reduced NO* release from stimulated endothelial cell cultures and increased O(2)(-*) production in the endothelium of isolated aortas by an L-NAME-inhibitable mechanism. Pretreatment with RAD increased stimulated O(2)(-*) production from eNOS, whereas pretreatment with genistein (GE), a broad-spectrum tyrosine kinase inhibitor, did not; however, pretreatment with GE + RAD resulted in a super-induced state of uncoupled eNOS activity upon stimulation. These data suggest that the tyrosine kinases, either directly or indirectly, and HSP90-dependent signaling pathways act in concert to suppress uncoupled eNOS activity.

Acetylcholine↗
PubMed2003

Membranous cells in nasal-associated lymphoid tissue: a portal of entry for the respiratory mucosal pathogen group A streptococcus.

Human tonsils are suspected to be an antibiotic-impervious human reservoir for group A streptococcus. An intranasal infection model in mice and a bioluminescent-tagged strain were used to investigate this possibility. Viable streptococci were predominantly found both intra- and extracellularly in nasal-associated lymphoid tissue (NALT), a human tonsil homologue. Ulex europaeus-1, a membranous (M) cell-specific lectin, identified cells harboring streptococci at the epithelial surface of NALT and blocked bacterial colonization of this tissue. These results suggest that M cells in NALT transport this Gram-positive pathogen across the epithelial layers in a manner similar to those in Peyer's patches, which permit enteric pathogens to invade deeper tissues from the gastrointestinal tract.

Administration, Intranasal↗
PubMed2003

[Animal models of schizophrenia using different laboratory mouse strains].

Based on the glutamate dysfunction hypothesis for the pathophysiology of schizophrenia, MK801, a noncompetitive antagonist for the NMDA-type of glutamate receptors, was administered to mice by i.p. injection. We observed hyperlocomotion and stereotypy, two behavioral signs indicative of schizophrenic symptoms in human. Aided with automated movement measuring of locomotion and videotaping for off-line scoring of stereotypy, these two schizophrenia-like behaviors were readily evaluated. According to the result of dose-response measurements of serial MK801 dosages in the BALB/c inbred mice, 0.6 mg/kg MK801 was determined as the optimum dosage for these behaviors. Furthermore, the same experiments were performed in another inbred strain C57BL/6 and the outbred stock ICR, and similar results were obtained. These results show that MK801 induces schizophrenia-like symptoms in both inbred and outbred mice. Risperidone, an atypical antipsychotic drug for treating schizophrenia in human, was used in the schizophrenia models using BALB/c and C57BL/6 mice. The results indicated that risperidone dose-dependently inhibited the MK801-induced schizophrenia-like symptoms in BALB/c and C57BL/6 mice. Thus, our results indicate that the MK801-induced behaviors may serve as useful mouse models of schizophrenia.

Animals↗
PubMed2003

Chimeric exchanges within the bradykinin B2 receptor intracellular face with the prostaglandin EP2 receptor as the donor: importance of the second intracellular loop for cAMP synthesis.

The prostaglandin E2 (PGE(2)) EP2 receptor (EP2R) type is G protein coupled (GPCR) and links to Galphas. Through this receptor PGE(2) activates cAMP production. The bradykinin (BK) B2 receptor (BKB2R) is also a GPCR but links to Galphaq and Galphai and does not activate cAMP production in response to bradykinin. In an attempt to convert the BKB2R into a Galphas-linked adenylate cyclase-activating receptor we proceeded to make global and discrete motif replacements of the intracellular (IC) face of the BKB2R with the corresponding regions of the human EP2R. With this approach we produced hybrid receptors which, when stably transfected into wild type (WT) Rat-1 cells, bound BK but produced cAMP. Replacement of the second loop (IC2), third loop (IC3), the entire C terminus, and the distal C terminus resulted in receptors which bound BK. However, only the IC2 and IC3 exchanges resulted in cAMP-producing receptors. Of these two regions, the IC2 exchange was by far the better cAMP-generating receptor, producing cAMP at approximately 6.6-fold above WT BKB2R or approximately one fourth the amount produced by WT EP2R-transfected Rat-1 cells. Both human and rat EP2R and human beta2-adrenergic receptor exchanges of the IC2 produced equal quantities of cAMP. Focusing on the rBKB2R/hEP2R IC2 chimeras, the region consisting of residues 136-147 (BKB2R residue numbering) proved to contain a cAMP-generating motif. Within this region, the proximal six amino acids from the EP2R (HPYFYQ) at position 136-141 proved crucial for cAMP production (10-fold over WT BKB2R). The distal part of this region, the six residues at 142-147, played no role in cAMP production. On the other hand, the ALV motif of the BKB2R IC2, residues 133-135, proved important with respect to phosphatydilinositol (PI) turnover. Replacing the entire IC2 of BKB2R resulted in poor PI turnover, while including the AVL of BKB2R retained approximately half of the WT PI turnover. With respect to receptor uptake, all the IC2 mutants endocytosed as WT BKB2R (60% in 1h). However, the exchange of the distal and the whole C termini resulted in a marked drop in endocytosis (30% in 1h). These results demonstrate that the construction of a cAMP-producing BKB2/EP2 receptor hybrid is possible, with the IC2 region distal to DRYLALV proving important to Galphas linkage and the LALV motif within the IC2 of BKB2R and the region proximal to it proving important for Galphaq and Galphai linkage. Additionally, our results confirm the importance of the distal C terminus in determining receptor uptake.

Amino Acid Sequence↗
PubMed2003

Loss of beta-catenin expression in metastatic gastric cancer.

PURPOSE: Beta-catenin (beta-catenin) participates in intercellular adhesion and is an integral part of the Wnt signaling pathway. The role of beta-catenin in the pathogenesis of gastric cancer and its metastasis is largely unknown. PATIENTS AND METHODS: Immunohistochemistry and Western blot analysis were used to analyze the expression of beta-catenin in 87 human gastric cancers, in metastasis and cancer cell lines. The beta-catenin and the adenomatous polyposis coli (APC) genes were analyzed for gene mutations. Furthermore, methylation of the beta-catenin promoter in cell lines was assessed by treatment with 5'-azadeoxycytidine and sodium bisulfite genomic sequencing. RESULTS: beta-Catenin expression was present at either the cell membrane or the cytoplasm in 34 of 75 primary gastric cancers. Expression of beta-catenin was significantly more frequent in intestinal-type (P =.0049) and well-differentiated gastric cancers (P <.001). There were no quantitative differences between gastric cancers and the nonmalignant gastric tissues, as determined by Western blot analysis. One of 18 metastatic cancer lesions and four of five gastric cancer cell lines expressed beta-catenin protein. N87 cells, derived from the liver metastasis of a gastric cancer, did not express beta-catenin. Treatment with 5'-azadeoxycytidine restored beta-catenin protein levels in this cell line, which exhibited significantly more 5-methylcytosines in the beta-catenin promoter compared with the other cell lines. CONCLUSION: beta-Catenin expression is lost in a subgroup of primary gastric cancers, is frequently absent in metastases, and exhibits nuclear localization in cancers with either beta-catenin or APC gene mutations. Interestingly, the loss of beta-catenin expression in metastatic gastric cancers may result from hypermethylation of the beta-catenin promoter.

Adenomatous Polyposis Coli↗
PubMed2003

[Vasorelaxing role of vasonatrin peptide in human intramammary artery in vitro].

The purpose of this study was to investigate the vasorelaxing effect of vasonatrin peptide (VNP) on human intramammary artery (HIMA).The vasorelaxing effect of VNP on HIMA was measured by means of perfusion in vitro. The effects of HS-142-1, TEA, 8-Br-cGMP and methylene blue (MB) were also observed. It was found that VNP caused a concentration-dependent relaxation in HIMA which was independent of the endothelium. 8-Br-cGMP (0.1-1000 micromol/L) also caused a concentration-dependent relaxation in HIMA. The vasorelaxing effect of VNP disappeared in the presence of HS-142-1 (20 micromol/L), an antagonist of the natriuretic peptide guanylate cyclase (GC) receptor. MB (10 micromol/L), an inhibitor of GC, not only blocked completely the relaxation of HIMA, but also enhanced the vascular contraction induced by norepinephrine. TEA (1 mmol/L), an antagonist of calcium activated potassium channels (K(Ca)), reduced but not completely blocked the vasorelaxing effect of VNP. These findings suggest that VNP can relax HIMA, which is independent of the endothelium. This effect is possibly achieved by the binding of VNP with the natriuretic peptide GC receptors in the smooth muscle cells (SMCs), leading to an increase in intracellular cGMP level. Moreover, the vasorelaxing effect of VNP is associated with K(Ca).

Aged↗
PubMed2003

Cell-permeable peptides improve cellular uptake and therapeutic gene delivery of replication-deficient viruses in cells and in vivo.

Small polybasic peptides derived from the transduction domains of certain proteins, such as the third alpha-helix of the Antennapedia (Antp) homeodomain, can cross the cell membrane through a receptor-independent mechanism. These cell-permeable molecules have been used as 'Trojan horses' to introduce biologically active cargo molecules such as DNA, peptides or proteins into cells. Using these cell-permeable peptides, we have developed an efficient and simple method to increase virally mediated gene delivery and protein expression in vitro and in vivo. Here, we show that cell-permeable peptides increase viral cell entry, improve gene expression at reduced titers of virus and improve efficacy of therapeutically relevant genes in vivo.

Adenoviridae↗
PubMed2003

Inactivation of helicase-like transcription factor by promoter hypermethylation in human gastric cancer.

Helicase-like transcription factor (HLTF), a member of the SWI/SNF (mating type switching/sucrose nonfermenting) chromatin-remodeling complex, is recently found to be inactivated by promoter hypermethylation in human colorectal cancer. However, the role of this putative tumor suppressor gene in other tumors has not been determined. We evaluated the role of HLTF promoter hypermethylation in gastric cancer. Expression of HLTF was examined by reverse-transcription (RT)-polymerase chain reaction (PCR), and promoter hypermethylation in HLTF was determined by methylation-specific PCR. Bisulfite DNA sequencing was performed to determine the detailed methylation profiles of the promoter region. HLTF expression was lost in two of five gastric cell lines and in 13 (28%) of 46 primary gastric cancers. Accordingly, promoter hypermethylation was detected in the two cell lines and in nine of 13 gastric cancer samples. Of the ten normal gastric specimens and ten paired adjacent nonneoplastic tissues, methylation was detected in only one adjacent nonneoplastic tissue. Bisulfite DNA sequencing of the promoter region of HLTF showed that the CpG island was densely methylated in cell lines and cancer samples; this also appeared to correlate with expression level. Treatment of gastric cell lines that lacked HLTF expression with the demethylating agent 5-azacytidine (5-azaDC) restored HLTF expression. These results suggest that HLTF promoter hypermethylation is frequently demonstrated in human gastric cancer, and inactivation of HLTF or the chromatin-remodeling complex may play a crucial role in gastric carcinogenesis.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Enhanced immune response to DNA-based HPV16L1 vaccination by costimulatory molecule B7-2.

We have investigated whether co-injection of DNA encoding the costimulatory molecule B7-2 augments immune response to the major capsid protein L1 of the high-risk human papillomavirus type 16 (HPV16L1). While immunoglobulin G (IgG) specific to HPV16L1 was detected in sera from mice injected intramuscularly with pcDNA-L1 that encodes HPV16L1, a significantly increased level of IgG was found in sera from mice immunised with pcDNA-L1 in conjunction with pLXHDmB7-2 DNA. Levels of IgG in the anti-sera were correlated with the inhibitory activity of the murine erythrocyte hemagglutination caused by the virus-like particles (VLP) and the binding of VLP to HeLa cells. Moreover, splenic cells isolated from mice co-injected with pLXHDmB7-2 had stronger proliferation and more IFN-gamma producing T cells (CD4(+) and CD8(+)) when stimulated with HPV16 VLP compared with cells from mice that had received pcDNA-L1 alone and mice of the control groups. Furthermore, in footpad swelling test, mice co-immunised with pLXHDmB7-2 had greater skin thickness over those immunised with pcDNA-L1 alone or control mice. We conclude that co-injection of DNA encoding B7-2 can enhance both humoral and cellular immune responses elicited by DNA-based vaccination against HPV16 infection in mice.

Adjuvants, Immunologic↗
PubMed2003

Selective inhibition of tumor microvascular permeability by cavtratin blocks tumor progression in mice.

Tumor vasculature is hyperpermeable to macromolecules compared to normal vasculature; however, the relationship between tumor hyperpermeability and tumor progression is poorly understood. Here we show that a cell-permeable peptide derived from caveolin-1, termed cavtratin, reduces microvascular hyperpermeability and delays tumor progression in mice. These antipermeability and antitumor actions of cavtratin occur in the absence of direct cytostatic or antiangiogenic effects. Cavtratin blocks microvascular permeability by inhibiting endothelial nitric oxide synthase (eNOS), as the antipermeability and antitumor actions of cavtratin are markedly diminished in eNOS knockout mice. Our results support the concepts that hyperpermeability of tumor blood vessels contributes to tumor progression and that blockade of eNOS may be exploited as a novel target for antitumor therapy.

Animals↗
PubMed2003

Azolla--a model organism for plant genomic studies.

The aquatic ferns of the genus Azolla are nitrogen-fixing plants that have great potentials in agricultural production and environmental conservation. Azolla in many aspects is qualified to serve as a model organism for genomic studies because of its importance in agriculture, its unique position in plant evolution, its symbiotic relationship with the N2-fixing cyanobacterium, Anabaena azollae, and its moderate-sized genome. The goals of this genome project are not only to understand the biology of the Azolla genome to promote its applications in biological research and agriculture practice but also to gain critical insights about evolution of plant genomes. Together with the strategic and technical improvement as well as cost reduction of DNA sequencing, the deciphering of their genetic code is imminent.

Cyanobacteria↗
PubMed2003

Gene identification and expression analysis of 86,136 Expressed Sequence Tags (EST) from the rice genome.

Expressed Sequence Tag (EST) analysis has pioneered genome-wide gene discovery and expression profiling. In order to establish a gene expression index in the rice cultivar indica, we sequenced and analyzed 86,136 ESTs from nine rice cDNA libraries from the super hybrid cultivar LYP9 and its parental cultivars. We assembled these ESTs into 13,232 contigs and leave 8,976 singletons. Overall, 7,497 sequences were found similar to existing sequences in GenBank and 14,711 are novel. These sequences are classified by molecular function, biological process and pathways according to the Gene Ontology. We compared our sequenced ESTs with the publicly available 95,000 ESTs from japonica, and found little sequence variation, despite the large difference between genome sequences. We then assembled the combined 173,000 rice ESTs for further analysis. Using the pooled ESTs, we compared gene expression in metabolism pathway between rice and Arabidopsis according to KEGG. We further profiled gene expression patterns in different tissues, developmental stages, and in a conditional sterile mutant, after checking the libraries are comparable by means of sequence coverage. We also identified some possible library specific genes and a number of enzymes and transcription factors that contribute to rice development.

Arabidopsis↗
PubMed2003

A genome sequence of novel SARS-CoV isolates: the genotype, GD-Ins29, leads to a hypothesis of viral transmission in South China.

We report a complete genomic sequence of rare isolates (minor genotype) of the SARS-CoV from SARS patients in Guangdong, China, where the first few cases emerged. The most striking discovery from the isolate is an extra 29-nucleotide sequence located at the nucleotide positions between 27,863 and 27,864 (referred to the complete sequence of BJ01) within an overlapped region composed of BGI-PUP5 (BGI-postulated uncharacterized protein 5) and BGI-PUP6 upstream of the N (nucleocapsid) protein. The discovery of this minor genotype, GD-Ins29, suggests a significant genetic event and differentiates it from the previously reported genotype, the dominant form among all sequenced SARS-CoV isolates. A 17-nt segment of this extra sequence is identical to a segment of the same size in two human mRNA sequences that may interfere with viral replication and transcription in the cytosol of the infected cells. It provides a new avenue for the exploration of the virus-host interaction in viral evolution, host pathogenesis, and vaccine development.

Base Sequence↗
PubMed2003

Complete genome sequences of the SARS-CoV: the BJ Group (Isolates BJ01-BJ04).

Beijing has been one of the epicenters attacked most severely by the SARS-CoV (severe acute respiratory syndrome-associated coronavirus) since the first patient was diagnosed in one of the city's hospitals. We now report complete genome sequences of the BJ Group, including four isolates (Isolates BJ01, BJ02, BJ03, and BJ04) of the SARS-CoV. It is remarkable that all members of the BJ Group share a common haplotype, consisting of seven loci that differentiate the group from other isolates published to date. Among 42 substitutions uniquely identified from the BJ group, 32 are non-synonymous changes at the amino acid level. Rooted phylogenetic trees, proposed on the basis of haplotypes and other sequence variations of SARS-CoV isolates from Canada, USA, Singapore, and China, gave rise to different paradigms but positioned the BJ Group, together with the newly discovered GD01 (GD-Ins29) in the same clade, followed by the H-U Group (from Hong Kong to USA) and the H-T Group (from Hong Kong to Toronto), leaving the SP Group (Singapore) more distant. This result appears to suggest a possible transmission path from Guangdong to Beijing/Hong Kong, then to other countries and regions.

Genome, Viral↗
PubMed2003

The C-terminal portion of the nucleocapsid protein demonstrates SARS-CoV antigenicity.

In order to develop clinical diagnostic tools for rapid detection of the SARS-CoV (severe acute respiratory syndrome-associated coronavirus) and to identify candidate proteins for vaccine development, the C-terminal portion of the nucleocapsid (NC) gene was amplified using RT-PCR from the SARS-CoV genome, cloned into a yeast expression vector (pEGH), and expressed as a glutathione S-transferase (GST) and Hisx6 double-tagged fusion protein under the control of an inducible promoter. Western analysis on the purified protein confirmed the expression and purification of the NC fusion proteins from yeast. To determine its antigenicity, the fusion protein was challenged with serum samples from SARS patients and normal controls. The NC fusion protein demonstrated high antigenicity with high specificity, and therefore, it should have great potential in designing clinical diagnostic tools and provide useful information for vaccine development.

Antigens, Viral↗