Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A full-length complementary DNA (cDNA) clone (pTK-3) encoding an isoform of Mg(2+)-dependent protein phosphatase beta (MPP beta-4) was isolated for the first time from a mouse melanocyte cDNA library. It was strongly suggested that the mRNA corresponding to the pTK-3 insert was a splicing variant of a single pre-mRNA that also encodes MPP beta-1 and -2 (T. Terasawa, T. Kobayashi, T. Murakami, M. Ohnishi, S. Kato, O. Tanaka, H. Kondo, H. Yamamoto, T. Takeuchi, and S. Tamura, 1993, Arch. Biochem. Biophys. 307, 342-349). The amino acid sequence of MPP beta-4 differed from those of MPP beta-1 and -2 only at the carboxyl terminal region. Analysis by reverse transcriptase polymerase chain reaction (RT-PCR) revealed that MPP beta-4 mRNA was expressed only in testis and intestine and not in other mouse tissues tested. Specific expression of the mRNA signals of two other isoforms of MPP beta, MPP beta-3 and -5 (a novel isoform), in testis and intestine was also demonstrated by the RT-PCR. The carboxyl terminal region of MPP beta-5 was found to have a chimera structure composed of part of MPP beta-1 and part of MPP beta-3. The recombinant MPP beta-3 and -4 and the putative MPP beta-5 expressed in Escherichia coli cells exhibited Mg(2+)-dependent and okadaic acid-insensitive protein phosphatase activities. It was demonstrated that the mRNA expression levels of MPP beta-3, -4, and -5 alter according to the maturation of mouse testis. These results suggest that the complex structure of MPP beta isoforms and their tissue- and developmental stage-specific expression reflect the variety of their physiological functions.
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PMID:Molecular cloning and expression of mouse mg(2+)-dependent protein phosphatase beta-4 (type 2C beta-4). 773 67

A cDNA encoding the regulatory subunit of Ca2+/calmodulin-dependent protein phosphatase, calcineurin B (CNB), was isolated from a rat testis cDNA library. It differs from the cDNA obtained from a rat brain cDNA library by an addition of 138 base pairs in the coding region. The codon of the clone from a testis library corresponding to the initiation codon of the clone from a brain library is not ATG but AAG, 5'-noncoding regions of these cDNAs are also different. The addition in the coding region results in the gain of 46 amino acids at the N-terminus. These findings suggest that two distinct isoforms of CNB alpha are derived from the same gene through a process involving alternative utilization of two promoters. We designate the brain type isoform as CNB alpha 1 and the longer isoform as CNB alpha 2. Northern blot analysis and reverse transcriptase-polymerase chain reaction (RT-PCR) followed by Southern blot analysis suggest that CNB alpha 2 is specifically expressed in the testis, and its expression is developmentally regulated.
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PMID:cDNA cloning of an alternatively spliced isoform of the regulatory subunit of Ca2+/calmodulin-dependent protein phosphatase (calcineurin B alpha 2). 811 Aug 31

Suramin has long been used for the treatment of Gambian and Rhodesian trypanosomiasis and oncocerciasis. More recently, the demonstration that suramin inhibits DNA polymerases, reverse transcriptase and the lymphocyte terminal deoxynucleotidyl transferase has led to its clinical trials for the treatment of AIDS and cancer. The precise nature of suramin's anti-neoplastic action is not clear at this time. Suramin rapidly alters the tyrosine-specific phosphorylation of cellular proteins in many cancer cell lines. Here we demonstrate that suramin strongly inhibits the activity of CD45, the principal tyrosine specific protein phosphatase of T lymphocytes. Suramin-induced inactivation of CD45 is noncompetitive, irreversible and complete within 10 min. The ability of suramin to block CD45 mediated phosphatase function provides both new insight into the mechanism of action of this agent and a useful new probe for studies of T cell activation.
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PMID:Suramin, an experimental chemotherapeutic drug, irreversibly blocks T cell CD45-protein tyrosine phosphatase in vitro. 833 52

TRAIL (TNF-related apoptosis inducing ligand), like other members of the TNF family of proteins, is able to induce apoptosis in sensitive target cells. Recently, cell-surface TRAIL has been shown to be expressed by activated human and mouse T lymphocytes, raising the possibility that TRAIL might be involved in T cell-mediated cytotoxicity and/or immune regulation. In the present study we show by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis that activated, but not resting, mouse T cells express abundant TRAIL mRNA. TRAIL transcripts were detectable within 4 h of T cell activation. A panel of pharmacologic inhibitors was used to investigate the signal transduction pathways involved in TRAIL gene induction following T lymphocyte activation. TRAIL gene expression was sensitive to the src-like protein tyrosine kinase (PTK) inhibitor herbimycin A, as well as the more general PTK inhibitor genistein, suggesting the involvement of a src family PTK. The PKC inhibitors staurosporine and calphostin C, and the phosphatidylinositol 3-kinase (PI3-K) inhibitors wortmannin and LY294002, also prevented TRAIL mRNA transcription by activated T cells, indicating a role for PKC and PI3-K. In addition, TRAIL induction was inhibited by cyclosporin A, implicating the Ca(2+)/calmodulin-dependent protein phosphatase calcineurin. TRAIL expression was also blocked by rapamycin, which inhibits p70 S6 kinase involved in CD28 and interleukin (IL)-2 receptor signaling. However, TRAIL mRNA expression was not induced by IL-2, suggesting that TRAIL gene induction is not coupled to the IL-2 receptor. Data obtained by RT-PCR were confirmed at the protein level by immunoblotting with TRAIL-specific antibody. We conclude that TRAIL gene induction is initiated through a T cell receptor-associated signaling pathway similar to that responsible for the expression of cytokine genes such as IL-2.
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PMID:Murine TRAIL (TNF-related apoptosis inducing ligand) expression induced by T cell activation is blocked by rapamycin, cyclosporin A, and inhibitors of phosphatidylinositol 3-kinase, protein kinase C, and protein tyrosine kinases: evidence for TRAIL induction via the T cell receptor signaling pathway. 1050 2

A rapid, semiquantitative reverse transcriptase-polymerase chain reaction assay was developed to investigate signal transduction events involved in the induction of Crassulacean acid metabolism (CAM) in detached common ice plant (Mesembryanthemum crystallinum) leaves. Transcript abundance of Ppc1, a gene encoding the CAM-specific isoform of phosphoenolpyruvate carboxylase, increased rapidly in response to osmotic stress (dehydration and mannitol), ionic stress (NaCl), and exogenous abscisic acid treatment, but failed to accumulate in response to exogenous cytokinin or methyl jasmonate. Stress-induced accumulation of Ppc1, GapC1, and Mdh1 transcripts was inhibited by pretreating leaves with the calcium chelator ethyleneglycol-bis(aminoethyl ether)-N,N'-tetraacetic acid, suggesting that extracellular calcium participates in signaling events leading to CAM induction. Treatment of unstressed detached leaves with ionomycin, a Ca(2+) ionophore, and thapsigargin, a Ca(2+)-ATPase inhibitor, enhanced Ppc1 transcript accumulation, indicating that elevations in cytosolic [Ca(2+)] are likely to participate in signaling CAM induction. Inhibitors of Ca(2+)- or calmodulin-dependent protein kinases (N-[6-aminohexyl]-5-chloro-1-napthalenesulfonamide, Lavendustin C) and protein phosphatase 1 and 2A (okadaic acid) activity suppressed Ppc1 transcript accumulation in response to ionic and osmotic stresses, as well as abscisic acid treatment. These results suggest that both protein phosphorylation and dephosphorylation events participate in signaling during CAM induction. In contrast, pretreatment with cyclosporin A or ascomycin, inhibitors of protein phosphatase 2B activity, stimulated Ppc1 gene expression either directly or indirectly through promoting water loss.
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PMID:Signaling events leading to crassulacean acid metabolism induction in the common ice plant 1051 46

Fas receptor is a member of a superfamily of receptors characterized by cysteine-rich motifs in the extracellular domain of the molecule. Binding of Fas ligand to the receptor leads to receptor activation and the induction of intracellular signals that result in apoptotic cell death. In the present study, the expression of mRNA and proteins of Fas receptor and Fas ligand were examined in human submandibular gland ductal (HSG) cells treated with okadaic acid by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblot analysis. Six hundred and eighty-two bp of the PCR product of Fas receptor mRNA was detected in HSG cells and a protein with an estimated molecular weight of 58,000 was expressed in HSG cells. Treatment of HSG cells with an agonistic anti-Fas monoclonal antibody resulted in death of HSG cells, indicating that the functional Fas receptor protein is expressed in HSG cells. Fas receptor protein expression stimulated by okadaic acid was elevated in a dose- and time-dependent manner, with maximal expression at 20 nM and 48 h treatment. Fas ligand mRNA was also detected constitutively in HSG cells by RT-PCR. Okadaic acid stimulated the expression of Fas ligand protein in HSG cells in a time-dependent manner, while the expression of the ligand was low in untreated HSG cells. The molecular weight of Fas ligand was estimated as 68,000. An antagonistic anti-Fas ligand monoclonal antibody prevented okadaic acid-induced death in HSG cells in a dose-dependent fashion as determined by WST-1 assay. The results indicate that the expression of Fas receptor and ligand is regulated by protein phosphatase(s) sensitive to okadaic acid and is involved in okadaic acid-induced apoptosis in HSG cells. The results also suggest that the Fas receptor-ligand system might regulate apoptosis in HSG cells.
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PMID:Upregulation of the expression of Fas antigen and Fas ligand in a human submandibular gland ductal cell line by okadaic acid. 1086 77

This study investigates the volume-sensitive KCI cotransporter (KCC) in various types of human cervical epithelial cell, testing the hypothesis that cervical malignancy is accompanied by differential expression of volume-sensitive KCC. Normal human cervical epithelial cells have KCCs which are quiescent in normal physiological conditions and are relatively refractory to hypotonic stress. By contrast, cervical cancer cells have KCCs which are also nearly quiescent in normal physiological conditions but high transport rates are observed in response to hypotonic challenge. Using isoform-specific primers, mRNA transcripts of KCC1, KCC3 and KCC4 were identified by reverse transcriptase polymerase chain reaction (RT-PCR) in several types of cervical cell, and confirmed by digestion with specific restriction endonucleases. By semiquantitative RT-PCR with beta-actin as the internal standard, the results indicate that cervical carcinogenesis is accompanied by the up-regulation of mRNA transcripts in KCC1, KCC3 and KCC4. [(Dihydroindenyl)oxy] alkanoic acid (DIOA), a KCC inhibitor, blocked both the regulatory volume decrease (RVD) process and volume-sensitive 86Rb+ efflux from cervical cancer cells in a dose-dependent manner. The volume-sensitive 86Rb+ efflux from cervical cancer cells was also blocked by two protein phosphatase inhibitors, calyculin A and okadaic acid, with IC50 values of 0.8 and 6 nM, respectively. Conversely, protein kinase inhibitors, chelerythrine and staurosporine, increased Cl- dependent 86Rb+ efflux. NEM (1 mM) led to a fivefold stimulation of 86Rb+ efflux which was totally Cl- dependent in cervical cancer cells. Hypotonicity could not stimulate any further 86Rb+ efflux after NEM treatment. These results indicate that the volume-sensitive KCC in cervical cancer cells plays a significant role in volume regulation and that the activities are modulated by a phosphorylation cascade. Taken together with our previous studies, we suggest the volume-regulatory ion channels and the co-transport systems work synergistically for volume regulation in human cervical cancer cells.
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PMID:Volume-sensitive KCI cotransport associated with human cervical carcinogenesis. 1100 18

Applying 10 pmol of okadaic acid (OA), a specific inhibitor of type 1 or type 2A serine/threonine protein phosphatases, to the orchid (Phalaenopsis species) stigma induced a dramatic increase in ethylene production and an accelerated senescence of the whole flower. Aminoethoxyvinylglycine or silver thiosulfate, inhibitors of ethylene biosynthesis or action, respectively, effectively inhibited the OA-induced ethylene production and retarded flower senescence, suggesting that the protein phosphatase inhibitor induced orchid flower senescence through an ethylene-mediated signaling pathway. OA treatment induced a differential expression pattern for the 1-aminocyclopropane-1-carboxylic acid synthase multigene family. Accumulation of Phal-ACS1 transcript in the stigma, labelum, and ovary induced by OA were higher than those induced by pollination as determined by "semiquantitative" reverse transcriptase-polymerase chain reaction. In contrast, the transcript levels of Phal-ACS2 and Phal-ACS3 induced by OA were much lower than those induced by pollination. Staurosporine, a protein kinase inhibitor, on the other hand, inhibited the OA-induced Phal-ACS1 expression in the stigma and delayed flower senescence. Our results suggest that a hyper-phosphorylation status of an unidentified protein(s) is involved in up-regulating the expression of Phal-ACS1 gene resulting in increased ethylene production and accelerated the senescence process of orchid flower.
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PMID:Differential expression of 1-aminocyclopropane-1-carboxylate synthase genes during orchid flower senescence induced by the protein phosphatase inhibitor okadaic acid. 1135 Oct 88

A cDNA clone was selected as a candidate for the catalytic subunit of phospho-pyruvate dehydrogenase phosphatase (PDP) by screening a Zea mays expressed sequence tag database with the bovine PDP deduced amino acid sequence. Both strands of the cDNA were completely sequenced. The maize clone contains an open reading frame of 1098 base pairs that encodes a polypeptide of 40 127 Da, ZMPP2. The deduced amino acid sequence of ZMPP2 contains the five PP2C signature domains, as does PDP. However, the expression pattern of ZMPP2, determined by reverse transcriptase-polymerase chain reaction, was different from those of the maize pyruvate dehydrogenase E1 alpha subunit and pyruvate dehydrogenase kinase. Additionally, the predicted subcellular location of ZMPP2 is cytoplasmic, while the pyruvate dehydrogenase complex, regulated by reversible phosphorylation, is mitochondrial. Thus, ZMPP2 is a PP2C-type protein phosphatase related to but distinct from PDP.
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PMID:ZMPP2, a novel type-2C protein phosphatase from maize. 1147 40

Fas receptor is a member of a superfamily of receptors characterized by cysteine-rich motifs in the extracellular domain of the molecule. Binding of Fas ligand to Fas receptor leads to activation of the latter and the induction of intracellular signals that result in apoptotic cell death. In the present study, we used reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis to examine the expression of mRNAs and proteins of Fas receptor and Fas ligand in human oral squamous carcinoma SCC-25 cells treated with okadaic acid. The PCR product of Fas receptor mRNA was detected in the cells and a protein with an estimated molecular weight of 35,000 was also expressed in them. Expression of Fas receptor mRNA stimulated by okadaic acid was elevated in dose- and time-dependent manners as judged by semiquantitative RT-PCR analysis, with the maximum expression level at 50 nM and 8 h treatment. Fas ligand mRNA expression was also stimulated by okadaic acid in SCC-25 cells in dose- and time-dependent manners. Okadaic acid also stimulated the expression of Fas ligand protein in the cells. Okadaic acid in serum-free medium induced apoptosis in SCC-25 cells in a time-dependent manner up to 24 h as determined by nuclear condensation and fragmentation of chromatin and DNA ladder formation. The present results indicate that the expression of Fas receptor and Fas ligand is negatively regulated by a protein phosphatase(s) sensitive to okadaic acid and is involved in okadaic acid-induced apoptosis in SCC-25 cells. Our results also suggest that Fas receptor and Fas ligand system might regulate apoptosis in SCC-25 cells in an autocrine fashion.
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PMID:Okadaic acid stimulates apoptosis through expression of Fas receptor and Fas ligand in human oral squamous carcinoma cells. 1175 16


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