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)

Coinfection with mycoplasmas has been shown to enhance cytopathic changes in T lymphocytes in culture brought about by human immunodeficiency virus type-1 (HIV-1), accelerate disease progression, and suppress reverse transcriptase (RT) activity simultaneously. We attempted to identify the components in culture supernatants of mycoplasmas which suppress RT activity. The marked inhibitory effect on RT by culture supernatants was dependent upon Mg2+. The culture supernatants exhibited the activities of DNase and RNase, which degraded the products and substrates in RT assay, respectively. Gel filtration studies revealed that two major protein peaks, peak 1 (MW 67-100 kDa) and peak 2 (MW 10-25 kDa), exhibited DNase and/or RNase activities, and that both peaks contained a significant degree of inhibitory activity on RT. These results indicate that suppression of RT activity by the culture supernatants of mycoplasmas is due to DNase and RNase activities in the culture supernatants. The results of the present investigation suggest that RT assay of certain biological materials that are contaminated with mycoplasmas must be conducted carefully.
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PMID:Suppression of HIV-1 reverse transcriptase activity by culture supernatants of mycoplasmas. 878 58

Acute HIV-1 infection of H9 and C8166 cultures has been shown to be suppressed by certain flavonoids, and evidence for inhibition of HIV-1 protease, integrase, and reverse transcriptase by flavonoids also exists. The present aim was to determine whether flavonoids inhibit HIV-1 activation in models of latent infection. By screening flavonoids from six different classes, three structurally related compounds (chrysin, acacetin, and apigenin) were identified that inhibited HIV expression in TNF-alpha-treated OM-10.1 cultures. The three compounds had favorable potencies against HIV activation in relation to their growth inhibitory effects (therapeutic index 5-10). Chrysin also inhibited HIV expression in response to PMA in OM-10.1 cells, in ACH-2 cells stimulated with either TNF-alpha or PMA, and in 8E5 cultures. Furthermore, return to viral latency in OM-10.1 cells previously exposed to TNF-alpha occurred over a shorter time interval when chrysin was added. The inhibition of HIV activation was not dependent on preincubation with flavonoids relative to TNF, and was characterized by a lack of HIV RNA accumulation by Northern analysis. Gel-shift experiments revealed that NF-kappa B activation after TNF-alpha treatment was not inhibited by these agents, suggesting that some other critical factor(s) needed for viral transcription was being affected. These findings indicate that flavonoids inhibit HIV-1 activation via a novel mechanism, and that these agents are potential candidates for therapeutic strategies aimed at maintaining a cellular state of HIV-1 latency.
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PMID:Inhibition of HIV activation in latently infected cells by flavonoid compounds. 882 17

Five classic DNA minor groove-binding drugs and a series of bis-linked lexitropsins based on netropsin and distamycin have been screened for their effectiveness in inhibiting transcription by HIV-1 reverse transcriptase (RT) on a poly(rA).oligo(dT) template-primer (TP). The two most effective drugs, 3,5 m-pyridyl-linked bisdistamycin (MPyr) and trans-vinyl-linked bisdistamycin (TVin), show (1) enhanced inhibition in reactions initiated with pre-incubated enzyme template-primer (ETP) and (2) reduced affinity for a "free" TP analog, when compared with the parent drug distamycin. All three drugs lack the ability to inhibit processive incorporation of nucleotide, suggesting drug intervention instead at initiation or termination of processive cycles. The two bis-linked drugs exhibit different kinetic behavior with reverse transcriptase's two substrates: template-primer and nucleotide. When primer is the variable substrate, TVin is partially noncompetitive and MPyr is dead-end competitive (Ki = 6.5 microM). With nucleotide as substrate, TVin is noncompetitive at low drug concentrations and MPyr is uncompetitive. Gel band mobility shift assays with MPyr indicate that the drug inhibits via entrapment of TP on the enzyme rather than displacement of TP from the enzyme surface. The conformation of nucleic acid is most likely altered upon MPyr binding, enhancing the induced fit of enzyme to hybrid duplex. The relevance of this novel mode of inhibition is considered in relation to enzyme association/dissociation with TP that occurs prior to (-)-DNA strand transfer, and to the structural implications of an enzyme-bound hybrid RNA/DNA nucleic acid.
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PMID:Linked lexitropsins and the in vitro inhibition of HIV-1 reverse transcriptase RNA-directed DNA polymerization: a novel induced-fit of 3,5 m-pyridyl bisdistamycin to enzyme-associated template-primer. 895 92

The insulin family of peptides and their receptors influence cellular growth in very early preimplantation embryos. In this study their expression and role in renal organogenesis was investigated. By immunofluorescence microscopy and in situ hybridization, insulin receptor (IR) expression was seen in the ureteric bud branches and early nephron precursors in mouse metanephroi harvested at day 13 of gestation. The expression gradually decreased in successive stages of gestation, and it was confined mainly to renal tubules in 1-week-old mice. Similar developmental regulation of the IR and insulin was observed by reverse transcriptase-polymerase chain reaction (RT-PCR) analyses. Addition of insulin into the culture medium at low concentrations, ranging from 40 to 400 ng/ml, induced trophic changes and increased [3H]thymidine incorporation in the embryonic renal explants, and inclusion of IR beta-subunit-specific antisense oligodeoxynucleotide caused marked dysmorphogenesis and growth retardation of the metanephroi. Specificity of the antisense effect was reflected by immunoprecipitation experiments in which translational blockade of the beta subunit of the IR was observed. RT-PCR analyses revealed that the alpha subunit of the IR was unaffected by the antisense treatment of metanephric explants. Concomitantly, de novo synthesis of morphogenetic regulatory extracellular matrix proteins, especially the proteoglycans, was decreased. Gel-shift analyses indicated a failure in the activation of c-fos promoter region binding protein(s) by insulin in the antisense oligodeoxynucleotide-treated explants. These studies suggest that insulin and its putative receptor are developmentally regulated in the murine embryonic metanephros, and they play a role in renal organogenesis, possibly by affecting other modulators of morphogenesis-i.e., extracellular matrix proteins and protooncogenes.
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PMID:Developmental regulation and the role of insulin and insulin receptor in metanephrogenesis. 919 38

The TGA genes encode a family of basic domain-leucine zipper (bZIP) transcription factors that are conserved in higher plants. We have continued to unravel the complexity of this gene family by using a polymerase chain reaction (PCR)-based approach. Taking advantage of the conserved amino acid sequence in the bZIP domain found in all members of this gene family, two degenerate oligonucleotides were synthesized based on the sequence of this region in order to amplify by PCR the analogous genomic fragments from the various TGA loci in Arabidopsis. This approach has led us to the finding of a new member of the TGA gene family, and subsequently the isolation of a gene designated as TGA6. Further characterization of the TGA6 locus confirmed our prediction that the gene structure of this family is remarkably conserved. Genomic Southern blot analysis revealed that TGA6 is a single-copy gene in Arabidopsis. Based on the genomic sequence information, gene-specific primers were synthesized for isolating the cDNA that corresponds to the coding region. Subsequently, the cDNA for TGA6 was cloned and sequenced. Gel mobility shift assays with in vitro translated TGA6 protein showed that TGA6 is more like TGA5 in terms of its in vitro DNA-binding properties. The expression of TGA6 in different tissues was estimated by using reverse transcriptase (RT)-PCR and further analyzed in transgenic Arabidopsis lines expressing a TGA6 promoter-GUS fusion. TGA6 promoter activity is found primarily in roots of young seedlings. As seedlings develop, TGA6 is expressed in aging cotyledons, mesophyll cells of hydathodes on leaf margins, vascular tissue and trichomes of senescing rosette leaves, but is very low in primary roots of mature plants. High levels of expression persist in young lateral roots and in regions of the primary root where lateral roots are emerging. In flowers, the activity is localized predominantly to mature pollen grains. The expression pattern of TGA6 reported here is strikingly similar to that of an Arabidopsis acidic chitinase gene. Possible biological significance of TGA6 in cellular defense against pathogens and abiotic stress is discussed.
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PMID:DNA-binding properties, genomic organization and expression pattern of TGA6, a new member of the TGA family of bZIP transcription factors in Arabidopsis thaliana. 922 52

Since elevated concentrations of plasma high density lipoprotein (HDL) and its major apolipoprotein (apo), apoA-I, confer protection against atherosclerosis, considerable research efforts have focussed on the identification of factors regulating apoA-I gene expression in an attempt to increase its production. Nuclear receptors are interesting candidates because they are transcription factors whose activity is ligand-dependent. In the present study we identified the orphan receptor RORalpha1 as an activator of apoA-I gene transcription. In apoA-I-expressing intestinal Caco-2 cells, overexpression of the RORalpha1, but not the RORalpha2 or RORalpha3 isoforms, increased rat apoA-I gene transcription. Deletion and site-directed mutagenesis experiments identified a functional ROR-responsive element (RORE) in the rat and mouse apoA-I gene promoters, which overlaps with the TATA box. Gel shift experiments indicated that this RORE binds the RORalpha1 isoform, but not the RORalpha2 or RORalpha3 isoforms. Furthermore, compared with wild type mice, apoA-I mRNA levels were significantly lower in small intestines of staggerer mice homozygous for a deletion in the RORalpha gene. In addition, reverse transcriptase-polymerase chain reaction analysis revealed the expression of RORalpha in small intestinal epithelium and in Caco-2 cells. These data indicate a novel, physiological role for RORalpha1 in the regulation of genes involved in lipid and lipoprotein metabolism and possibly in the development of metabolic diseases, such as atherosclerosis.
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PMID:Transcriptional regulation of apolipoprotein A-I gene expression by the nuclear receptor RORalpha. 927 89

Rat-2 fibroblasts demonstrate specific binding of 125I-labelled rat adrenomedullin (KD=0.43 nM; Bmax=50 fmol/mg of protein) in the absence of 125I-labelled calcitonin-gene-related peptide (CGRP) binding. Therefore Rat-2 cells were used to examine the pharmacology and signal transduction pathways of adrenomedullin receptors. We examined the effects of adrenomedullin, the CGRP receptor antagonist CGRP-(8-37) and the amylin antagonists AC187 and AC253 on receptor binding and cAMP production. AC253, AC187 and CGRP-(8-37) inhibited 125I-adrenomedullin binding, with respective IC50 values of 25+/-8, 129+/-39 and 214+/-56 nM. Adrenomedullin dose-dependently increased intracellular cAMP (approximate EC50=1.0 nM). CGRP-(8-37), AC253 and AC187 antagonized adrenomedullin-stimulated cAMP production at micromolar concentrations. Using kinase-substrate assays, Mono Q FPLC and 'phospho-specific' Western blotting, we found that adrenomedullin alone abolished basal mitogen-activated protein kinase (MAPK) activity and dose-dependently inhibited platelet-derived-growth-factor-stimulated MAPK activity. Radioimmunoassay for adrenomedullin of media from Rat-2 cells showed a linear release of adrenomedullin-like immunoreactivity of 3.1 fmol/h per 2x10(6) cells. Gel-filtration chromatography showed that this adrenomedullin-like immunoreactivity co-eluted with synthetic rat adrenomedullin. Northern blotting with a rat adrenomedullin cDNA probe was used to confirm the presence of adrenomedullin mRNA. However, neither Northern blotting nor reverse transcriptase-PCR showed the presence of the cloned adrenomedullin receptor (L1). We conclude that the Rat-2 cell line expresses a specific adrenomedullin receptor (coupled to cAMP production and regulation of MAPK) and secretes adrenomedullin, which may participate in a regulatory control loop.
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PMID:Rat-2 fibroblasts express specific adrenomedullin receptors, but not calcitonin-gene-related-peptide receptors, which mediate increased intracellular cAMP and inhibit mitogen-activated protein kinase activity. 993 Dec 92

Recent studies have suggested that simvastatin may exert endothelial-protective and anti-ischemic effects via nitric oxide (NO) mechanisms. The aim of this study was to evaluate, in isolated working rat hearts, the effect of acute simvastatin administration on endothelial and inducible NO-synthase (eNOS and iNOS) mRNA and on myocytic apoptosis after ischemia-reperfusion. We used isolated working rat hearts submitted to 15 min global, no-flow, normothermic ischemia and 180 min reperfusion. To detect myocytic apoptosis we used DNA agarose gel electrophoresis and Tunel technique; eNOS and iNOS expression were evaluated by multiplex reverse transcriptase-polymerase chain reaction; glyceraldehyde-3-phosphate dehydrogenase (G3PDH) was used as standard. The eNOS and iNOS mRNAs were expressed as G3PDH/eNOS and G3PDH/iNOS densitometric ratio (BioRad Gel Doc 1000). Hearts were divided into four groups: A) hearts excised and used as histological controls; B) untreated hearts submitted to ischemia and reperfusion; C) actinomicin D-treated (1.5 mg/kg) hearts, perfused with 25 microM simvastatin, subjected to ischemia and reperfusion; D) hearts treated with simvastatin 25 microM and submitted to ischemia and reperfusion. In Group B we evidenced a significant myocytic apoptotic damage, reduced in groups C and D. In Group B an increase in G3PDH/eNOS ratio vs Group A was detected; in Group D a reduction in G3PDH/eNOS ratio vs Group B occurred; no significant changes were observed between groups C and D. As for G3PDH/iNOS ratio, it was significantly increased in Group D with respect to groups A and B. Our data suggest that simvastatin in acute may modulate NO-synthase mRNA expression (induction of eNOS mRNA by means of post-transcriptional mechanisms and inhibition of iNOS postischemic overexpression) and reduce myocytic apoptosis.
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PMID:[Simvastatin and ischemia-reperfusion damage: its effects on apoptotic myocyte death and on the endothelial expression of nitric-oxide synthetase in an experimental model of the isolated rat heart]. 1018 33

Transforming growth factor (TGF)-beta1 induces extracellular matrix deposition and proliferation of mesenchymal cells. We recently reported that interleukin (IL)-6 is an essential mediator of growth factor-induced proliferation of lung fibroblasts. Here, we demonstrate by reverse transcriptase polymerase chain reaction and enzyme-linked immunoassay that TGF-beta1 is a potent inducer of IL-6 mRNA and protein in primary human lung fibroblasts. Transient transfections of fibroblasts with a luciferase reporter gene construct containing nucleotides -651 to +1 of the human IL-6 promoter revealed that TGF-beta1 also potently activated IL-6 promoter activity. Progressive 5'-deletions and site-directed mutagenesis of the parental construct located the TGF-beta1-responsive cis-regulatory element to a known activating protein-1 (AP-1) sequence (nucleotides -284 to -276). Gel shift analyses revealed that AP-1 DNA binding activity in nuclear extracts was increased 30 min after stimulation with TGF-beta1. In contrast, neither CCAAT enhancer-binding protein-beta, NF-kappaB, nor Sp1 were activated by TGF-beta1. Supershift analyses demonstrated that the AP-1 complex induced by TGF-beta1 was composed of Jun isoforms and absent of Fos isoforms. Moreover, this complex was found to be a JunD homodimer. Our data thus demonstrate that TGF-beta1 is a potent inducer of IL-6 in primary human lung fibroblasts. The TGF-beta1-activated JunD homodimer may be essential for a majority of the biological effects induced by TGF-beta1 in this cell type, such as proliferation and extracellular matrix synthesis.
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PMID:Transforming growth factor-beta1 induces interleukin-6 expression via activating protein-1 consisting of JunD homodimers in primary human lung fibroblasts. 1021 84

Telomerase is a ribonucleoprotein reverse transcriptase that synthesizes and maintains telomeric DNA. Studies of telomeres and telomerase are facilitated by the large number of linear DNA molecules found in ciliated protozoa, such as Tetrahymena thermophila. To examine the expression of telomerase, we investigated the transcription of the RNA polymerase III-directed gene encoding the RNA subunit (TER1) of this enzyme. A chimeric gene containing the Glaucoma chattoni TER1 transcribed region flanked by 5' and 3' Tetrahymena regions was used to identify promoter elements following transformation of Tetrahymena cells. Disruption of a conserved proximal sequence element (PSE) located at -55 in the Tetrahymena TER1 5' flanking region eliminated expression of the chimeric gene. In addition, mutation of an A/T-rich element at -25 decreased expression markedly. A gel mobility shift assay and protein-DNA cross-linking identified a PSE-binding polypeptide of 50-60 kDa in Tetrahymena extracts. Gel filtration analysis revealed a native molecular mass of approximately 160 kDa for this binding activity. Our results point to a similar architecture between ciliate telomerase RNA and metazoan U6 small nuclear RNA promoters.
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PMID:Identification of an essential proximal sequence element in the promoter of the telomerase RNA gene of Tetrahymena thermophila. 1051 20


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