Biomedical subjects

Y Chen

Publications and source records attributed to Y Chen.

At least 1,027 records · Page 57Linked to original sources

PubMed1999

Smad3 inhibits transforming growth factor-beta and activin signaling by competing with Smad4 for FAST-2 binding.

Transcriptional regulation by transforming growth factor-beta and activin is mediated by interaction of Smad2 and Smad3 with specific transcription factors and/or DNA elements. However, Smad3 behaves differently from Smad2 in regulating transcription by a winged-helix transcription factor, FAST-2, on an activin-responsive element (ARE) in the Xenopus Mix.2 promoter. Smad3 alone was able to stimulate the ARE through FAST-2, but inhibited the ARE transactivation mediated by Smad2/Smad4 following receptor activation. We characterized the functional domains that are involved in these two activities of Smad3. Deletion of the MH1 domain as well as mutations of four lysine residues in the MH1 domain abrogated the inhibitory activity of Smad3, but did not compromise the self-stimulatory function. In contrast, deletion of the MH2 domain or a point mutation of glycine 379 within this domain obliterated the self-stimulatory activity of Smad3, but not the inhibitory activity. In an electrophoretic mobility shift assay, we found that Smad3 was able to associate with the FAST-2.ARE complex and that this association was dependent on FAST-2. In addition, Smad3 was not able to directly bind the ARE in a DNase I protection assay, in which FAST-2 binds the ARE around a motif (TGTGTATT) previously characterized to associate with the human FAST-1 protein. Interestingly, Smad4 was also able to directly associate with the FAST-2.ARE complex through binding with FAST-2. In a gel shift assay, the association of FAST-2 with Smad4 was mutually exclusive from the association with Smad3. Taken together, these data indicate that Smad3 exerts the inhibitory activity by competitive association with FAST-2.

Activin Receptors↗

PubMed1999

Cloning the promoter for transforming growth factor-beta type III receptor. Basal and conditional expression in fetal rat osteoblasts.

Transforming growth factor-beta binds to three high affinity cell surface molecules that directly or indirectly regulate its biological effects. The type III receptor (TRIII) is a proteoglycan that lacks significant intracellular signaling or enzymatic motifs but may facilitate transforming growth factor-beta binding to other receptors, stabilize multimeric receptor complexes, or segregate growth factor from activating receptors. Because various agents or events that regulate osteoblast function rapidly modulate TRIII expression, we cloned the 5' region of the rat TRIII gene to assess possible control elements. DNA fragments from this region directed high reporter gene expression in osteoblasts. Sequencing showed no consensus TATA or CCAAT boxes, whereas several nuclear factors binding sequences within the 3' region of the promoter co-mapped with multiple transcription initiation sites, DNase I footprints, gel mobility shift analysis, or loss of activity by deletion or mutation. An upstream enhancer was evident 5' proximal to nucleotide -979, and a silencer region occurred between nucleotides -2014 and -2194. Glucocorticoid sensitivity mapped between nucleotides -687 and -253, whereas bone morphogenetic protein 2 sensitivity co-mapped within the silencer region. Thus, the TRIII promoter contains cooperative basal elements and dispersed growth factor- and hormone-sensitive regulatory regions that can control TRIII expression by osteoblasts.

Animals↗

PubMed1999

Post-transcriptional adenylation of signal recognition particle RNA is carried out by an enzyme different from mRNA Poly(A) polymerase.

A fraction of the signal recognition particle (SRP) RNA from human, rat, Xenopus, and Saccharomyces cerevisiae cells contains a single post-transcriptionally added adenylic acid residue on its 3'-end; in the case of human SRP RNA, over 60% of the SRP RNA molecules contain a nontemplated adenylic acid residue on their 3'-ends (Sinha, K. M., Gu, J., Chen, Y., and Reddy, R. (1998) J. Biol. Chem. 273, 6853-6859). In this study, we investigated the enzyme that is involved in this 3'-end adenylation of SRP RNA. A U1A protein peptide conjugated to albumin completely inhibited the polyadenylation of a SV40 mRNA by HeLa cell nuclear extract in vitro; however, the 3'-end adenylation of human SRP RNA or Alu RNA, which corresponds to 5' and 3'-ends of SRP RNA, was not affected by this U1A peptide conjugate. SRP RNA from mutant strains of S. cerevisiae with a temperature-sensitive mRNA poly(A) polymerase grown at a restrictive temperature of 37 degrees C also contained a post-transcriptionally added adenylic acid residue just like SRP RNA from wild-type cells and mutant cells grown at permissive temperature of 23 degrees C. In addition, binding of SRP 9/14-kDa protein heterodimer was required for adenylation of Alu RNA in vitro. These lines of evidence, along with other data, show that post-transcriptional adenylation of SRP and Alu RNAs is carried out by a novel enzyme that is distinct from the mRNA poly(A) polymerase, CCA-adding enzyme, and nonspecific terminal transferase.

Alu Elements↗

PubMed1999

Hormone therapy failure in human prostate cancer: analysis by complementary DNA and tissue microarrays.

BACKGROUND: The molecular mechanisms underlying the progression of prostate cancer during hormonal therapy have remained poorly understood. In this study, we developed a new strategy for the identification of differentially expressed genes in hormone-refractory human prostate cancer by use of a combination of complementary DNA (cDNA) and tissue microarray technologies. METHODS: Differences in gene expression between hormone-refractory CWR22R prostate cancer xenografts (human prostate cancer transplanted into nude mice) and a xenograft of the parental, hormone-sensitive CWR22 strain were analyzed by use of cDNA microarray technology. To validate the data from cDNA microarrays on clinical prostate cancer specimens, a tissue microarray of specimens from 26 prostates with benign prostatic hyperplasia, 208 primary prostate cancers, and 30 hormone-refractory local recurrences was constructed and used for immunohistochemical detection of protein expression. RESULTS: Among 5184 genes surveyed with cDNA microarray technology, expression of 37 (0.7%) was increased more than twofold in the hormone-refractory CWR22R xenografts compared with the CWR22 xenograft; expression of 135 (2.6%) genes was reduced by more than 50%. The genes encoding insulin-like growth factor-binding protein 2 (IGFBP2) and 27-kd heat-shock protein (HSP27) were among the most consistently overexpressed genes in the CWR22R tumors. Immunohistochemical analysis of tissue microarrays demonstrated high expression of IGFBP2 protein in 100% of the hormone-refractory clinical tumors, in 36% of the primary tumors, and in 0% of the benign prostatic specimens (two-sided P =.0001). Overexpression of HSP27 protein was demonstrated in 31% of the hormone-refractory tumors, in 5% of the primary tumors, and in 0% of the benign prostatic specimens (two-sided P =.0001). CONCLUSIONS: The combination of cDNA and tissue microarray technologies enables rapid identification of genes associated with progression of prostate cancer to the hormone-refractory state and may facilitate analysis of the role of the encoded gene products in the pathogenesis of human prostate cancer.

Animals↗

PubMed1999

6,7,8,9-Tetrahydro-3-methyl-1H-pyrano-[4,3-b]quinolin-1-one.

The condensation reaction of 4-amino-6-methyl-2-pyrone with 1-cyclohexenecarboxaldehyde and a catalytic amount of (S)-(+)-10-camphorsulfonic acid in toluene at 358 K gave a 1:2.5 ratio of the title compound, (1) (C13H13NO2), and 7,8,9,10-tetrahydro-1H-pyrano[4,3-c]isoquinoline-1-one, (2). The formation of (2) presumably proceeds through an intermediate imine. Both (1) and (2) show inhibitory activities against acetylcholinesterase and human aldose reductase. Of the three linear-fused rings of (1), both ring A and ring B are planar and the angle between these planes is 0.46 (13) degrees. While the two C atoms of cyclohexane ring C attached to its common atoms with ring B are in the plane of the latter, as expected, the remaining two C atoms of ring C are out of this plane, by 0.342 (4) and -0.402 (3) A, respectively.

Aldehyde Reductase↗

PubMed1999

[DNA cloning and partial sequence analysis of EBV LMP1 gene isolated from human nasopharyngeal carcinoma cell line SUNE1].

OBJECTIVE: To study the variation of EBV LMP1 encoding gene isolated from human nasopharyngeal carcinoma cell line SUNE1 in Guangdong. METHODS: The EBV LMP1 gene was amplified from the SUNE1 cell genome by PCR and then the recombinant vector was constructed by inserting the PCR fragment into pcDNA3. The encoding EBV LMP1 spanning from exon1 to exon3 in recombinant vector was sequenced by the Sequence Analyzer. RESULTS: The 1,312 bp encoding EBV LMP1 pieces in 2.6 kb PCR fragments were compared with the same EBV segments in B95-8 cell line. The data indicated that the rate of nucleotide sequence homology between the two fragments is 98.5% and the rate of amino acid is 96%. The restricted enzyme site of Xho I in exon1 was deleted in SUNE1 but the 30 bp deletion at the carboxyl terminus in most Chinese NPC LMP1 gene was not present. CONCLUSION: Although the LMP1 gene derived from SUNE1 had greater tumorigenicity than that derived from B95-8 cell, the high homology rate of nucleotide and amino acid sequences between them indicated that it was not the result from the variation of certain nucleotide sites but the change in amino acid domain.

Amino Acid Sequence↗

PubMed1999

[An inquire into the infection of a new virus(TTV)].

OBJECTIVE: The aim of this study is to find out the prevalence of TTV in the cryptogenic hepatitis' and the clinical features of TTV infected patients. METHODS: TTV DNA in the serum was tested by nested PCR and the clinical data was analyzed. RESULTS: Infection rate of the TTV in cryptogenic hepatitis was 38.6%. It was a sporadic disease, and involved mainly the adults, with no sexual difference. The symptoms were notable, often with jaundice, but the level of transaminase were elevated moderately. Histology revealed the portal area inflammation. If accompanied with other disease, the illness would be exacerbated. CONCLUSION: TTV would be accounted for part of the reason in patients with cryptogenic hepatitis.

Adult↗

PubMed1999

[Detection of serum antibody of coxsackievirus A24 variant].

OBJECTIVE: To observe the serum antibody in residents after outbreak of acute hemorrhagic conjunctivitis (AHC) caused by coxrackievirus (CA24 v). METHODS: The serum was diluted in 1:10 and mixed with 100 TCID50 CA24 v in volume. The same the mixture was incubated 1 hour in 37 degrees C and then observed for cytopathic changes of the infected HeLa cells. RESULTS: The post-epidemic antibody positive rate in residents was 49.67% and in 19-25 age group was about 69.49%. It had significant difference statistically (P < 0.01). CONCLUSION: The raising of CA24 v antibody level in residents was relevent with age. May be it was caused by the opporturnities of taking part in social activities in different age groups.

Adolescent↗

PubMed1999

[Effect of aluminium on meiotic maturation of mouse oocyte in vitro].

The effect of aluminium nitrate on the meiotic maturation of mouse oocyte was studied in the culture of mouse oocyte. The results showed that aluminium nitrate could inhibit the extruding of the first polar body and the dose of 30 mg/L and 60 mg/L could affect the viability of mouse oocyte, but little impact on the germinal vesicle breakdown (GVBD) of oocyte. The results indicated that aluminium nitrate might be hazardous to the meiotic maturation of mouse oocyte.

Aluminum Compounds↗

PubMed1999

[Progress in detecting methods on paralytic shellfish poisons].

Paralytic shellfish poisons have led to uncountable economic losses, and done potential harm to human health now. In order to overcome the limits of the traditional bioassay with mouse, many novel detecting methods have been developed, which made it possible to detect the paralytic shellfish poisons with sensitive, high effective and rapid methods. This paper systematically introduces the progress in research on paralytic shellfish poisons detection.

Biological Assay↗

PubMed1999

ERK MAP kinase links cytokine signals to activation of latent HIV-1 infection by stimulating a cooperative interaction of AP-1 and NF-kappaB.

Human immunodeficiency virus type 1 (HIV-1) can establish latent infection following provirus integration into the host genome. NF-kappaB plays a critical role in activation of HIV-1 gene expression by cytokines and other stimuli, but the signal transduction pathways that regulate the switch from latent to productive infection have not been defined. Here, we show that ERK1/ERK2 mitogen-activated protein kinase (MAPK) plays a central role in linking signals at the cell surface to activation of HIV-1 gene expression in latently infected cells. MAPK was activated by cytokines and phorbol 12-myristate 13-acetate in latently infected U1 cells. The induction of HIV-1 expression by these stimuli was inhibited by PD98059 and U0126, which are specific inhibitors of MAPK activation. Studies using constitutively active MEK or Raf kinase mutants demonstrated that MAPK activates the HIV-1 long terminal repeat (LTR) through the NF-kappaB sites. Most HIV-1 inducers activated NF-kappaB via a MAPK-independent pathway, indicating that activation of NF-kappaB is not sufficient to explain the activation of HIV-1 gene expression by MAPK. In contrast, all of the stimuli activated AP-1 via a MAPK-dependent pathway. NF-kappaB and AP-1 components c-Fos and c-Jun were shown to physically associate by yeast two-hybrid assays and electrophoretic mobility shift assays. Coexpression of NF-kappaB and c-Fos or c-Jun synergistically transactivated the HIV-1 LTR through the NF-kappaB sites. These studies suggest that MAPK acts by stimulating AP-1 and a subsequent physical and functional interaction of AP-1 with NF-kappaB, resulting in a complex that synergistically transactivates the HIV-1 LTR. These results define a mechanism for signal-dependent activation of HIV-1 replication in latently infected cells and suggest potential therapeutic strategies for unmasking latent reservoirs of HIV-1.

Cytokines↗

PubMed1999

Ectopic purinergic sensitivity develops at sites of chronic nerve constriction injury in rat.

The possibility that ectopic purinergic sensitivity develops following peripheral nerve injury was investigated in chronic constriction injury (CCI). Spontaneous firing of A-fibers originated from the injury site or from sensory endings of afferents in the contralateral sciatic nerve. ATP injected intravenously excited most of the injured fibers whereas none of the contralateral afferents responded to ATP. The ATP-induced effect was blocked by the P2 receptor antagonist reactive blue 2, but not the P1 receptor antagonist aminophylline. Neither the alpha-adrenoreceptor antagonist phentolamine nor the cyclooxygenase inhibitor indomethacin attenuated the ATP-evoked effect. We conclude that a novel ectopic purinergic sensitivity mediated by P2 receptors develops at sites of the CCI of nerves in the rat, which may contribute to neuropathic pain.

Adenosine Triphosphate↗

PubMed1999

Eosinophil peroxidase nitrates protein tyrosyl residues. Implications for oxidative damage by nitrating intermediates in eosinophilic inflammatory disorders.

Eosinophil peroxidase (EPO) has been implicated in promoting oxidative tissue injury in conditions ranging from asthma and other allergic inflammatory disorders to cancer and parasitic/helminthic infections. Studies thus far on this unique peroxidase have primarily focused on its unusual substrate preference for bromide (Br(-)) and the pseudohalide thiocyanate (SCN(-)) forming potent hypohalous acids as cytotoxic oxidants. However, the ability of EPO to generate reactive nitrogen species has not yet been reported. We now demonstrate that EPO readily uses nitrite (NO(2)(-)), a major end-product of nitric oxide ((.)NO) metabolism, as substrate to generate a reactive intermediate that nitrates protein tyrosyl residues in high yield. EPO-catalyzed nitration of tyrosine occurred more readily than bromination at neutral pH, plasma levels of halides, and pathophysiologically relevant concentrations of NO(2)(-). Furthermore, EPO was significantly more effective than MPO at promoting tyrosine nitration in the presence of plasma levels of halides. Whereas recent studies suggest that MPO can also promote protein nitration through indirect oxidation of NO(2)(-) with HOCl, we found no evidence that EPO can indirectly mediate protein nitration by a similar reaction between HOBr and NO(2)(-). EPO-dependent nitration of tyrosine was modulated over a physiologically relevant range of SCN(-) concentrations and was accompanied by formation of tyrosyl radical addition products (e.g. o,o'-dityrosine, pulcherosine, trityrosine). The potential role of specific antioxidants and nucleophilic scavengers on yields of tyrosine nitration and bromination by EPO are examined. Thus, EPO may contribute to nitrotyrosine formation in inflammatory conditions characterized by recruitment and activation of eosinophils.

Animals↗

PubMed1999

Experimental autoimmune encephalomyelitis in NF-kappa B-deficient mice:roles of NF-kappa B in the activation and differentiation of autoreactive T cells.

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the CNS, which has long been used as an animal model for human multiple sclerosis. Development of autoimmune disease requires coordinated expression of a number of genes that are involved in the activation and effector functions of inflammatory cells. These include genes that encode costimulatory molecules, cytokines, chemokines, and adhesion molecules. Activation of these genes is regulated at the transcriptional level by several families of transcription factors. One of these is the NF-kappa B family, which is present in a variety of cell types and becomes highly activated at sites of inflammation. To test the roles of NF-kappa B in the development of autoimmune diseases, we studied EAE in mice deficient in one of the NF-kappa B isoforms, i.e., NF-kappa B1 (p50). We found that NF-kappa B1-deficient mice were significantly resistant to EAE induced by myelin oligodendrocyte glycoprotein. The resistance was primarily evidenced by a decrease in disease incidence, clinical score, and the degree of CNS inflammation. Furthermore, we established that the resistance to EAE in NF-kappa B1-deficient mice was associated with a deficiency of myelin oligodendrocyte glycoprotein-specific T cells to differentiate into either Th1- or Th2-type effector cells in vivo. These results strongly suggest that NF-kappa B1 plays crucial roles in the activation and differentiation of autoreactive T cells in vivo and that blocking NF-kappa B function can be an effective means to prevent autoimmune encephalomyelitis.

Animals↗

PubMed1999

The addition of adenovirus type 5 region E3 enables calydon virus 787 to eliminate distant prostate tumor xenografts.

CV787, a novel highly prostate-specific replication-competent adenovirus with improved efficacy, was constructed. CV787 contains the prostate-specific rat probasin promoter, driving the adenovirus type 5 (Ad5) E1A gene, and the human prostate-specific enhancer/promoter, driving the E1B gene. To improve efficacy, we constructed CV787 such that it also contains the entire Ad5 E3 region. CV787 replicates in prostate-specific antigen (PSA)+ cells as well as wild-type adenovirus, but in PSA- cells, CV787 replicates 10(4)-10(5) times less efficiently. CV787 destroys PSA+ prostate cancer cells 10,000 times more efficiently than PSA- cells. Incorporation of the Ad5 E3 region significantly improves the target cell killing ability or efficacy of CV787. In nu/nu mice carrying s.c. LNCaP xenografts, a single i.v. tail vein injection of CV787 eliminates 300-mm3 tumors within 4 weeks. CV787 could be a powerful therapeutic for human metastatic prostate cancer.

Adenoviridae↗

PubMed1999

Selective A1-adenosine receptor antagonists identified using yeast Saccharomyces cerevisiae functional assays.

Evaluation of a biased "library" of pyrrolo[2,3-d]pyrimidines using yeast-based functional assays expressing human A1- and A2a-adenosine receptors, led to the A1 selective antagonist 4b. A direct correlation between yeast functional activity and binding data was established. Practical compounds with polar residues at C-4 of the pyrrolopyrimidine system required H-bond donor functionality for high potency.

Binding, Competitive↗

PubMed1999

Anhydroretinol induces oxidative stress and cell death.

The retro-retinoid anhydroretinol (AR), a physiological metabolite of retinol (vitamin A), induces cell death in multiple in vitro systems. AR-induced cell death is blocked by retinol and its metabolite 14-hydroxy-4,14-retro-retinol. AR has been shown also to prevent mammary cancer induced by N-methyl-N-nitrosourea in rats. We report that AR kills cells by generating reactive oxygen species. Direct measurements show that the addition of AR to lymphoblastoid cells increases the intracellular oxidative stress in a time- and dose-dependent manner. Furthermore, the amount of induced oxidative stress directly correlates with the number of dying cells. The addition of retinol, 14-hydroxy-4,14-retro-retinol, or the antioxidant, alpha-tocopherol (vitamin E), decreases AR-induced oxidative stress and proportionally reduces AR-induced cell death. In contrast, pretreatment with caspase inhibitors, known to inhibit apoptosis, has no effect on AR-induced cell death. This is the first demonstration of cellular reactive oxygen species production by a natural retinoid.

Animals↗

PubMed1999

Informatic selection of a neural crest-melanocyte cDNA set for microarray analysis.

With cDNA microarrays, it is now possible to compare the expression of many genes simultaneously. To maximize the likelihood of finding genes whose expression is altered under the experimental conditions, it would be advantageous to be able to select clones for tissue-appropriate cDNA sets. We have taken advantage of the extensive sequence information in the dbEST expressed sequence tag (EST) database to identify a neural crest-derived melanocyte cDNA set for microarray analysis. Analysis of characterized genes with dbEST identified one library that contained ESTs representing 21 neural crest-expressed genes (library 198). The distribution of the ESTs corresponding to these genes was biased toward being derived from library 198. This is in contrast to the EST distribution profile for a set of control genes, characterized to be more ubiquitously expressed in multiple tissues (P < 1 x 10(-9)). From library 198, a subset of 852 clustered ESTs were selected that have a library distribution profile similar to that of the 21 neural crest-expressed genes. Microarray analysis demonstrated the majority of the neural crest-selected 852 ESTs (Mel1 array) were differentially expressed in melanoma cell lines compared with a non-neural crest kidney epithelial cell line (P < 1 x 10(-8)). This was not observed with an array of 1,238 ESTs that was selected without library origin bias (P = 0.204). This study presents an approach for selecting tissue-appropriate cDNAs that can be used to examine the expression profiles of developmental processes and diseases.

Calibration↗