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J Zhou

Publications and source records attributed to J Zhou.

At least 253 records · Page 14Linked to original sources
PubMed2000

Regulation of the paired type IV collagen genes COL4A5 and COL4A6. Role of the proximal promoter region.

Tissue-specific expression patterns of the paired type IV collagen genes COL4A5 and COL4A6 form the basis for organ involvement in X-linked Alport syndrome, a disorder in which these genes are mutated. We investigated the proximal promoter region of COL4A5 and COL4A6 using glomerular visceral epithelial cells, in which COL4A5 alone is transcribed; keratinocytes, in which the genes are co-transcribed; and additional model cell lines. By RNase protection assays, the intergenic region is 292 base pairs. Transcription start sites for two 5' splice variants of COL4A6 are 1 kilobase apart. Transient transfections with reporter gene constructs revealed that the minimal promoters for COL4A5 and COL4A6 are within 100 base pairs of their respective transcription start sites and are functionally distinct. In further transfection, gel shift and footprinting assays, we defined a bidirectional positive regulatory element, which functions in several cell types, but not in glomerular visceral epithelial cells selectively transcribing COL4A5. The existence of separate promoters for COL4A5 and COL4A6 permits fine control over their expression. Activation through the bidirectional element can bring about co-expression of the genes, exploiting their paired arrangement. Features of the proximal promoter region frame its roles in a hierarchy regulating type IV collagen gene expression.

Base Sequence↗
PubMed2000

Presenilin affects arm/beta-catenin localization and function in Drosophila.

Presenilin is an essential gene for development that when disrupted leads to a neurogenic phenotype that closely resembles Notch loss of function in Drosophila. In humans, many naturally occurring mutations in Presenilin 1 or 2 cause early onset Alzheimer's disease. Both loss of expression and overexpression of Presenilin suggested a role for this protein in the localization of Armadillo/beta-catenin. In blastoderm stage Presenilin mutants, Arm is aberrantly distributed, often in Ubiquitin-immunoreactive cytoplasmic inclusions predominantly located basally in the cell. These inclusions were not observed in loss of function Notch mutants, suggesting that failure to process Notch is not the only consequence of the loss of Presenilin function. Human presenilin 1 expressed in Drosophila produces embryonic phenotypes resembling those associated with mutations in Armadillo and exhibited reduced Armadillo at the plasma membrane that is likely due to retention of Armadillo in a complex with Presenilin. The interaction between Armadillo/beta-catenin and Presenilin 1 requires a third protein which may be delta-catenin. Our results suggest that Presenilin may regulate the delivery of a multiprotein complex that regulates Armadillo trafficking between the adherens junction and the proteasome.

Animals↗
PubMed2000

Study on the fluorescence spectra and electrochemical behavior of ZnL2 and Morin with DNA.

The interactions of Morin (2', 3, 4', 5, 7-pentahydroxyflavone) and its Zn-complex, ZnL2.3H2O [L = Morin (2'-OH group deprotonated)], with calf thymus DNA have been studied using fluorimetric and electrochemical methods. ZnL2.3H2O has different spectral characteristics and electrochemical behavior from that of Morin in the presence of DNA. Increasing fluorescence is seen for ZnL2.3H2O with DNA addition whereas decreased fluorescence is observed for Morin. An isosbestic point appears at 560 nm for the DNA-ZnL2.3H2O system with ethidium bromide (EB) addition while no isosbestic point is detectable for Morin. Quenching fluorescence is observed for DNA-EB system when ZnL2.3H2O is added whereas no quenched fluorescence is seen for DNA-EB system with Morin addition. The above results suggest that Morin and ZnL2.3H2O can both bind to DNA, but the binding mode is different. The complex binds to DNA mainly by intercalation, while Morin binds in a non-intercalating mode. The binding constant and binding site sizes are derived from electrochemical methods. For ZnL2.3H2O, the binding constant is 5.0 x 10(4) l mol(-1) at 20 degrees C, and the binding site size n(s) is 5.

DNA↗
PubMed2000

A human PKD1 transgene generates functional polycystin-1 in mice and is associated with a cystic phenotype.

Three founder transgenic mice were generated with a 108 kb human genomic fragment containing the entire autosomal dominant polycystic kidney disease (ADPKD) gene, PKD1, plus the tuberous sclerosis gene, TSC2. Two lines were established (TPK1 and TPK3) each with approximately 30 copies of the transgene. Both lines produced full-length PKD1 mRNA and polycystin-1 protein that was developmentally regulated, similar to the endogenous pattern, with expression during renal embryogenesis and neonatal life, markedly reduced at the conclusion of renal development. Tuberin expression was limited to the brain. Transgenic animals from both lines (and the TPK2 founder animal) often displayed a renal cystic phenotype, typically consisting of multiple microcysts, mainly of glomerular origin. Hepatic cysts and bile duct proliferation, characteristic of ADPKD, were also seen. All animals with two copies of the transgenic chromosome developed cysts and, in total, 48 of the 100 transgenic animals displayed a cystic phenotype. To test the functionality of the transgene, animals were bred with the Pkd1(del34) knockout mouse. Both transgenic lines rescued the embryonically lethal Pkd1(del34/del34) phenotype, demonstrating that human polycystin-1 can complement for loss of the endogenous protein. The rescued animals were viable into adulthood, although more than half developed hepatic cystic disease in later life, similar to the phenotype of older Pkd1(del34/+) animals. The TPK mice have defined a minimal area that appropriately expresses human PKD1. Furthermore, this model indicates that over-expression of normal PKD1 can elicit a disease phenotype, suggesting that the level of polycystin-1 expression may be relevant in the human disease.

Animals↗
PubMed2000

Interaction of the papillomavirus transcription/replication factor, E2, and the viral capsid protein, L2.

The minor capsid protein L2 of papillomaviruses (PVs) likely plays a role in the selective encapsidation of PV DNA in viral capsids and in the infectivity of PV virions. The L2 protein also can cause the relocalization of the PV early protein, E2TA, to nuclear subdomains known as promyelocytic leukemia oncogenic domains (PODs) in which it is localized. E2TA is a transcriptional transactivator that also plays a critical role in viral DNA replication. In this study, we investigated whether L2, in causing the relocalization of E2TA, alters the activities of E2TA. We provide evidence that L2 inhibits the transcriptional transactivation function of E2, but it does not specifically inhibit the capacity of E2 to support viral DNA replication. We also investigated whether the colocalization of E2 and L2 to PODs and the ability of L2 to inhibit the transcriptional transactivation activity of E2TA might be mediated through a direct interaction between these two proteins. Using an in vitro protein-protein association assay, we found that L2 binds to E2TA. Two regions in E2TA were found to mediate this interaction. One of those domains is present in an alternative E2 gene product, E2TR, which is an antagonist to E2TA. Here we show that the L2 protein also relocalizes the E2 transcriptional repressor, E2TR, to the nuclear subdomains. These data suggest that the ability of L2 to relocalize E2 proteins to PODs is mediated through a direct interaction with L2.

Animals↗
PubMed2000

Basis for half-of-the-site reactivity and the dominance of the K487 oriental subunit over the E487 subunit in heterotetrameric human liver mitochondrial aldehyde dehydrogenase.

Human liver mitochondrial aldehyde dehydrogenase is a tetrameric enzyme composed of 4 identical 500 amino acid containing subunits arranged such that the protein is a dimer of dimers. No kinetic evidence for subunit interactions has been reported. However, the enzyme exhibits half-of-the-site reactivity in that there is a pre-steady-state burst of 2 mol of NADH per mole of enzyme. A variant of the enzyme, found in Asian people, contains a lysine rather than a glutamate at position 487. This enzyme has a high K(M) for NAD(+) and a low specific activity. In heterotetramers composed of both subunit types, it appeared that the lysine-containing subunit was dominant over the glutamate-containing subunits. To allow for the separation of various heterotetrameric forms of the enzyme, surface residues were changed. Each of the five possible tetrameric forms of the modified enzyme was isolated and characterized with respect to steady-state kinetics and pre-steady-state burst magnitudes. The data best fit a model where in each dimer pair there is one functioning and one nonfunctioning subunit. Further, the lysine subunit affects the properties only of its dimer partner. Residue 487 is located at the dimer interface, and the glutamate forms salt bonds with two arginine residues. One is to Arg(264) in the same subunit; the other is to Arg(475) located in the other subunit. Most likely the presence of a lysine affects these salt bonds so the lysine subunit can cause the other subunit to become essentially nonfunctional.

Aldehyde Dehydrogenase↗
PubMed2000

Striatal extracts promote the survival and phenotypic expression of rat fetal dopaminergic neurons in vitro.

To begin to identify novel protein(s) that acts on nigral dopaminergic (DA) neurons, we characterized trophic effects of DA-depleted striatum on survival of fetal DA neurons in the present study. Treatment of ventral mesencephalic cultures with the striatal extracts delayed DA cell death in a dose-dependent manner. This effect was partially dependent on brain-derived neurotrophic factor (BDNF), but not glial cell line-derived neurotrophic factor (GDNF), present in the extracts. Furthermore, we addressed the hypothesis that the striatum-derived substances can elicit DA phenotypic expression of striatal cells in cultures. The striatal extract was found to be able to induce expression of tyrosine hydroxylase in cultured striatal cells in the presence of dopamine. These data suggest that denervation of the striatum resulted in production of neurotrophic factors, including BDNF and as-yet-unidentified trophic substances, which may be responsible for the increased survival and DA phenotype expression in DA neurons.

Animals↗
PubMed2000

Differential expression of mRNAs of GDNF family in the striatum following 6-OHDA-induced lesion.

Changes of mRNA levels of GDNF and its recently discovered congeners persephin, neurturin, artemin in the striatum of lesioned side following 6-hydroxydopamine (6-OHDA) lesion in rodents were investigated with semi-quantitative RT-PCR. Two weeks after the lesions were made, mRNA levels of GDNF family members, except for neurturin, were significantly increased in the striatum on the side ipsilateral to the lesion compared with equivalent tissue of sham control. This increase reached a maximal level 5-7 weeks post-lesion. The marked increase of BDNF mRNA expression was also observed in the ipsilateral striatum with similar time course. These findings suggest that 6-OHDA-induced lesions can change gene expression in denervated target tissue, and that mRNA levels of GDNF family members in striatal cells may be modulated by afferent dopaminergic input in a slow-rising and long-lasting fashion.

Animals↗
PubMed2000

Mechanisms governing the differentiation of a serotonergic phenotype in culture.

In this study, we explored whether a serotonergic (5-HT) phenotype could be novelly induced in the phenotypically plastic neurons of the developing striatum. We found that the 5-HT biosynthetic enzyme tryptophan hydroxylase (TPH) was expressed in nearly 10% of neurons following treatment with an extract derived from adult raphe tissue. This effect was mimicked by co-treatment with a growth factor (aFGF, bFGF or BDNF; but not GDNF, IGF-1, EGF or TGF) and the neurotransmitter 5-HT (but not GABA, dopamine, glutamate) and/or a protein kinase activator (IBMX, forskolin, TPA). Treatment with combined factors (aFGF+5-HT+IBMX+forskolin+TPA) yielded the greatest level of TPH induction (15.6%). Moreover, TPH was enzymatically active (112.8+/-36 pmol/mg per h) and produced detectable levels of 5-HT (2.12+/-0.30 ng) and its metabolite 5-HIAA (4.24+/-0.11 ng) in maximally stimulated cultures. These findings demonstrate that it is possible to promote the differentiation of serotonergic phenotypic traits in developing brain neurons in culture.

Animals↗
PubMed2000

Induction of an HPV 6bL1-specific mucosal IgA response by DNA immunization.

Human papillomavirus (HPV) plays a crucial role in the development of human anogenital dysplasia. To prevent infection, it is important to induce an HPV-specific mucosal immune response. We investigated whether DNA vaccination would induce an intravaginal mucosal antibody response against HPV 6bL1. New Zealand White rabbits were immunized with an HPV 6bL1 DNA vaccine by one of the three routes: muscular, vaginal, or rectal. We found that vaginal immunization of rabbits with HPV 6bL1 DNA induced 6bL1 virus-like particle-specific lgA antibodies in vaginal secretions. They were detectable until at least 14 weeks after the first immunization. The antibodies also showed neutralizing activity in a hemagglutination inhibition assay. No mucosal immune response was detected in vaginal secretions of rabbits immunized intramuscularly or intrarectally. Our data suggest that vaginal immunization with HPV 6bL1 DNA induces long-lasting IgA responses with neutralizing activity in vaginal secretions of rabbits.

Administration, Intravaginal↗
PubMed2000

The dual impact of coxsackie and adenovirus receptor expression on human prostate cancer gene therapy.

In a recent paper, we reported a significant difference in coxsackie and adenovirus receptor (CAR) from several human bladder cancer cell lines that correlated with their sensitivities to adenoviral infection (Y. Li, R-C. Pong, J. M. Bergelson, M. C. Hall, A. I. Sagalowsky, C-P. Tseng, Z. Wang, and J. T. Hsieh, Cancer Res., 59: 325-330, 1999). In human prostate cancer, CAR protein is down-regulated in the highly tumorigenic PC3 cell line, which suggests that, in addition to its function as a viral receptor, CAR may have a pathophysiological role in prostate cancer progression. In this paper, we document that CAR does not merely enhance the viral sensitivity of prostate cancer cells but also acts as a tumor inhibitor for androgen-independent prostate cancer cells. Our data indicate that CAR is a potential therapeutic agent for increasing the efficacy of prostate cancer therapy.

Adenoviridae↗
PubMed2000

Cleavage of lamin-like proteins in in vivo and in vitro apoptosis of tobacco protoplasts induced by heat shock.

Apoptosis in heat shock-treated tobacco protoplasts was evidenced by DNA fragmentation, flow cytometric analysis and activation of caspase 3-like protease. Furthermore, an in vitro apoptosis system was established which reproduced the apoptotic events. Western blotting analysis using an antibody against lamin A and C showed that in both in vivo and in vitro systems lamin-like proteins were cleaved into a 35-kDa fragment, and that lamin-like protein degradation precedes DNA fragmentation. Moreover, we found a 22.8-fold increase in caspase 6-like activity in cytosol of heat-treated protoplasts as compared with the control.

Apoptosis↗
PubMed2000

Gene expression profiling in the human hypothalamus-pituitary-adrenal axis and full-length cDNA cloning.

The primary neuroendocrine interface, hypothalamus and pituitary, together with adrenals, constitute the major axis responsible for the maintenance of homeostasis and the response to the perturbations in the environment. The gene expression profiling in the human hypothalamus-pituitary-adrenal axis was catalogued by generating a large amount of expressed sequence tags (ESTs), followed by bioinformatics analysis (http://www.chgc.sh.cn/ database). Totally, 25,973 sequences of good quality were obtained from 31,130 clones (83.4%) from cDNA libraries of the hypothalamus, pituitary, and adrenal glands. After eliminating 5,347 sequences corresponding to repetitive elements and mtDNA, 20,626 ESTs could be assembled into 9, 175 clusters (3,979, 3,074, and 4,116 clusters in hypothalamus, pituitary, and adrenal glands, respectively) when overlapping ESTs were integrated. Of these clusters, 2,777 (30.3%) corresponded to known genes, 4,165 (44.8%) to dbESTs, and 2,233 (24.3%) to novel ESTs. The gene expression profiles reflected well the functional characteristics of the three levels in the hypothalamus-pituitary-adrenal axis, because most of the 20 genes with highest expression showed statistical difference in terms of tissue distribution, including a group of tissue-specific functional markers. Meanwhile, some findings were made with regard to the physiology of the axis, and 200 full-length cDNAs of novel genes were cloned and sequenced. All of these data may contribute to the understanding of the neuroendocrine regulation of human life.

Alternative Splicing↗
PubMed2000

Pif1p helicase, a catalytic inhibitor of telomerase in yeast.

Mutations in the yeast Saccharomyces cerevisiae PIF1 gene, which encodes a 5'-to-3' DNA helicase, cause telomere lengthening and a large increase in the formation rate of new telomeres. Here, we show that Pif1p acts by inhibiting telomerase rather than telomere-telomere recombination, and this inhibition requires the helicase activity of Pif1p. Overexpression of enzymatically active Pif1p causes telomere shortening. Thus, Pif1p is a catalytic inhibitor of telomerase-mediated telomere lengthening. Because Pif1p is associated with telomeric DNA in vivo, its effects on telomeres are likely direct. Pif1p-like helicases are found in diverse organisms, including humans. We propose that Pif1p-mediated inhibition of telomerase promotes genetic stability by suppressing telomerase-mediated healing of double-strand breaks.

Alleles↗
PubMed2000

Selection of antibiotic-resistant bacterial mutants: allelic diversity among fluoroquinolone-resistant mutations.

To obtain a general framework for understanding selection of antibiotic-resistant mutants, allelic diversity was examined with about 600 fluoroquinolone-resistant mutants of mycobacteria. Selection at low fluoroquinolone concentration produced many low-level resistance mutants. Some of these contained mutations that conferred unselected antibiotic resistance; none contained alterations in the quinolone-resistance-determining region of the GyrA protein, the principal drug target. As selection pressure increased, a variety of GyrA variants became prevalent. High concentrations of antibiotic reduced the variety to a few types, and eventually a concentration was reached at which no mutant was recovered. That concentration defined a threshold for preventing the selection of resistance. The pattern of variants selected, which was also strongly influenced by antibiotic structure, readily explained the variants present in clinical isolates. Thus, resistance arises from selection of mutants whose identity depends on drug concentration and structure, both of which can be manipulated to restrict selection.

Alleles↗
PubMed2000

Activation of protein kinase A modulates trafficking of the human cardiac sodium channel in Xenopus oocytes.

Voltage-gated Na(+) channels are critical determinants of electrophysiological properties in the heart. Stimulation of beta-adrenergic receptors, which activate cAMP-dependent protein kinase (protein kinase A [PKA]), can alter impulse conduction in normal tissue and promote development of cardiac arrhythmias in pathological states. Recent studies demonstrate that PKA activation increases cardiac Na(+) currents, although the mechanism of this effect is unknown. To explore the molecular basis of Na(+) channel modulation by beta-adrenergic receptors, we have examined the effects of PKA activation on the recombinant human cardiac Na(+) channel, hH1. Both in the absence and the presence of hbeta(1) subunit coexpression, activation of PKA caused a slow increase in Na(+) current that did not saturate despite kinase stimulation for 1 hour. In addition, there was a small shift in the voltage dependence of channel activation and inactivation to more negative voltages. Chloroquine and monensin, compounds that disrupt plasma membrane recycling, reduced hH1 current, suggesting rapid turnover of channels at the cell surface. Preincubation with these agents also prevented the PKA-mediated rise in Na(+) current, indicating that this effect likely resulted from an increased number of Na(+) channels in the plasma membrane. Experiments using chimeric constructs of hH1 and the skeletal muscle Na(+) channel, hSKM1, identified the I-II interdomain loop of hH1 as the region responsible for the PKA effect. These results demonstrate that activation of PKA modulates both trafficking and function of the hH1 channel, with changes in Na(+) current that could either speed or slow conduction, depending on the physiological circumstances.

Animals↗
PubMed2000

Prolongation of allograft survival by Nippostrongylus brasiliensis is associated with decreased allospecific cytotoxic T lymphocyte activity and development of T cytotoxic cell type 2 cells.

BACKGROUND: We have demonstrated that infection with Nippostrongylus brasiliensis (Nb), which induces strong type 2 responses, prolongs kidney allograft survival in rats. Here, we confirm that this effect is not species-specific and address immune modulation in allospecific T-cell responses mediated by nematode infection. METHODS: C57BL/6 mice were injected with Nb or phosphate-buffered saline. Four days later, mice were transplanted with BALB/c hearts and graft survival was assessed. In other experiments, Nb-infected mice were immunized with BALB/c spleen cells and allospecific T-cell responses were determined in vitro. RESULTS: In this study, we show that Nb prolongs cardiac allograft survival in mice. Further, spleen T cells from Nb-infected, allo-immunized mice exhibit reduced allospecific cytotoxic T-lymphocyte activity. In contrast, allospecific proliferation of T cells in the mixed lymphocyte reaction was not reduced by Nb, ruling out immunosuppression as the mechanism of Nb-induced allograft survival. Nb infection induced IL-4 and IL-6 and inhibited IFN-gamma production by T cells in response to allo-antigen. Furthermore, anti-IL-4 treatment reduced allospecific T-cell proliferation from Nb-infected but not control mice, indicating that type 2 allospecific T cells develop in the presence of Nb. We also double-stained T cells for CD8 and IL-4 and showed that Nb induces an 8-fold increase in Tc2 cell numbers. CONCLUSIONS: These results are consistent with a hypothesis that Nb mediates prolongation of allograft survival through induction of type 2 immunity, including the development of regulatory Tc2 cells, and subsequent inhibition of allospecific cytotoxic T-lymphocyte activity.

Animals↗