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

---

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

Specific inhibitors and anti-DNA polymerase alpha IgG have been utilized to probe for similarities between cytoplasmic rat hepatic glucocorticoid receptors and DNA polymerase alpha [DNA nucleotidyltransferase (DNA-directed), EC 2.7.7.7]. Rifamycin AF/013, an inhibitor of RNA and DNA polymerase activities, significantly inhibited the binding of activated [6,7-3H]-triamcinolone acetonide (TA) receptor complexes to DNA-cellulose. beta-Lapachone, an inhibitor of DNA polymerase alpha and reverse transcriptase activities, inhibited the specific binding of [6,7-3H]TA when preincubated with unbound receptors. Aphidicolin, another DNA polymerase alpha inhibitor, failed to inhibit any of the glucocorticoid-receptor functions tested. Two specific anti-DNA polymerase alpha IgGs interfered with glucocorticoid receptor functions as measured by their ability to inhibit the binding of [6,7-3H]TA to unbound receptors (85% maximal inhibition) and, to a lesser extent, to inhibit the binding of activated [6,7-3H]TA receptor complexes to DNA-cellulose (50% maximal inhibition). The anti-DNA polymerase alpha IgG and beta-lapachone failed to affect the binding of tritiated estradiol, progesterone, or 5 alpha-dihydrotestosterone to their receptors in appropriate rat target tissues or the binding of [1,2-3H]hydrocortisone to serum transcortin. The most obvious interpretation of these data is that cytoplasmic glucocorticoid receptors and DNA polymerase alpha share antigenic determinants. An alternative interpretation is that the polyclonal anti-DNA polymerase alpha antibody contains IgG molecules raised against calf thymus cytoplasmic activated glucocorticoid-receptor complexes that copurified with DNA polymerase alpha used as the antigen. Taken collectively, however, the antibody and inhibitor data suggest a relationship between DNA polymerase alpha and the glucocorticoid receptor.
...
PMID:Correlations between the activities of DNA polymerase alpha and the glucocorticoid receptor. 681 51

Dexamethasone (DEX) is a glucocorticoid that is widely used after vitreoretinal surgery and may have mitogenic properties. This study was initiated to determine if human cultured retinal pigment epithelium (RPE) cells express glucocorticoid receptor and proliferate in response to DEX stimulation. Glucocorticoid receptor mRNA was detected in RPE cells by means of reverse transcriptase polymerase chain reaction. To determine the effect of DEX on RPE cell proliferation in vitro, we cultured human RPE cells with various concentrations for DEX for 5 days and determined the effects on cell number and incorporation of tritiated thymidine. DEX treatment with a DEX dose of 1 microgram/ml in the presence or absence of serum resulted in a maximal 2-3 times increase in cell number. Autoradiography after thymidine incorporation revealed a greater than 2-fold increase in incorporating cells at this same dose. These results indicate that DEX causes cultured human RPE cells to proliferate and suggest that it may have a growth factor-like action.
...
PMID:Dexamethasone induced proliferation of cultured retinal pigment epithelial cells. 803 87

Although their precise mechanism of action remains to be elucidated, glucocorticoids represent the most effective therapy in the treatment of asthma. Interactions between the glucocorticoid receptor and the AP-1 complex have been shown to regulate the transcription of some genes, including glucocorticoid receptor itself. The aim of the present study was to compare the expression of mRNA for glucocorticoid receptor in human blood monocytes obtained from seven unstable untreated asthmatic patients who were subsequently treated with high doses of parenteral corticosteroid (methyl prednisolone 120 mg/day) for 10 days. mRNA expression was identified after RNA extraction using RNAzol and analysed after reverse transcriptase, by polymerase chain reaction using a semiquantitative competitive hybridization assay. All asthmatic patients showed an improvement in their FEV1 values after corticosteroid treatment (per cent of predicted value 68.28 +/- 4.93 versus 95.57 +/- 6.41, P < 0.02), and a significant decrease for glucocorticoid receptor mRNA expression (P < 0.02) was observed in their monocytes. This is the first report of an ex vivo down-regulation for the glucocorticoid receptor mRNA expression, following corticosteroid treatment.
...
PMID:Glucocorticoids induced down-regulation of glucocorticoid receptor mRNA expression in asthma. 856 17

Alternative splicing of the human glucocorticoid receptor (hGR) primary transcript produces two receptor isoforms, hGRalpha and hGRbeta, which differ at their carboxyl termini. The hGRalpha isoform conveys endocrine information to target tissues by altering patterns of gene expression in a hormone-dependent fashion. In contrast to hGRalpha, very little is known about the hGRbeta splice variant. Using hGRalpha- and hGRbeta-specific riboprobes on human multiple tissue Northern blots, we show that the hGRbeta message has a widespread tissue distribution. We also prove by reverse transcriptase-polymerase chain reaction that the alternative splicing event underlying the formation of the hGRbeta message occurs in these tissues. Because the hGRbeta protein differs from hGRalpha at the extreme COOH terminus, we investigated several of the biochemical properties of hGRbeta expressed in transfected cells. hGRbeta does not bind the glucocorticoid agonist dexamethasone nor the glucocorticoid antagonist RU38486 in vivo. Moreover, in contrast to hGRalpha, hGRbeta is located primarily in the nucleus of transfected cells independent of hormone administration. Finally, in the absence of hGRalpha, hGRbeta is transcriptionally inactive on a glucocorticoid-responsive enhancer. However, when both isoforms are expressed in the same cell, hGRbeta inhibits the hormone-induced, hGRalpha-mediated stimulation of gene expression. Thus, hGRbeta potentially functions as a dominant negative inhibitor of hGRalpha activity.
...
PMID:The human glucocorticoid receptor beta isoform. Expression, biochemical properties, and putative function. 862 28

Progesterone is a known immunosupressant in humans and may be important in treatment regimens for women with immunological and endocrinological reproductive failure. The molecular mechanism of progesterone-mediated immunosuppression remains controversial. We used the reverse transcriptase polymerase chain reaction (RT-PCR) technique to detect progesterone receptor RNA in human peripheral blood mononuclear cells (PBMCs). No expression could be documented in PBMCs from men or women representing various reproductive states. We also used the glucocorticoid receptor antagonist RU 43044 to address the hypothesis that progesterone exerts immunomodulatory effects via interactions with the glucocorticoid receptor. Both hydrocortisone (10(-6) and 10(-7) M) and progesterone (10(-5), 10(-6) and 10(-7) M) inhibited phytohaemagglutinin-induced lymphocyte proliferation in a dose-dependent fashion. RU 43044 (10(-5) M) significantly reversed the immunosuppressive effect od hydrocortisone but not that of progesterone. These studies indicate that human PBMCs do not express the classical progesterone receptor. Our results further suggest that progesterone does not mediate its immunomodulatory effects via interaction with the glucocorticoid receptor. Interaction with other members of the steroid and thyroid hormone receptor superfamily, local conversion to other steroid substances or non-classical receptor-mediated mechanisms may be involved.
...
PMID:Progesterone-induced immunosuppression is not mediated through the progesterone receptor. 913 Jul 72

Leukaemia inhibitory factor (LIF) is the generally recognized nomenclature for a pleiotropic cytokine that exerts multiple biological effects in different systems. However, its role in the neuroendocrine system is relatively unexplored, with the exception of one report indicating that LIF may act to determine the unique vascular organization of the pituitary gland. In the present study the expression of LIF mRNA has been demonstrated for the first time in the pituitary gland of the rat, in all three pituitary lobes. However, LIF gene expression is restricted to tissues in explant culture where LIF transcripts are readily detectable by Northern Techniques. Similar studies using the reverse transcriptase-polymerase chain reaction (RT-PCR) technique also failed to detect LIF transcripts in fresh tissue from adult animals. These results are consistent with the hypothesis that LIF acts to mediate the response to trauma, a response that may include the induction of neuropeptide expression in the anterior pituitary. In further studies it has also been shown that anterior pituitary LIF mRNA is super-induced in the presence of protein synthesis inhibitors, a response that indicates a role for a labile protein in the attenuation of LIF expression. Both the explantation response, and the response to protein synthesis inhibitory drugs are decreased in the presence of dexamethasone indicating that a glucocorticoid receptor mechanism acts as a general modulatory influence on LIF mRNA levels. These findings are consistent with the presence of multiple regulatory controls on the expression of LIF that serve to restrict its expression to pathological conditions, and indicate that LIF does not participate in normal endocrine physiology.
...
PMID:Leukaemia inhibitory factor expression in cultured rat anterior pituitary is regulated by glucocorticoids. 870 36

Steroids have the ability to alter adipose tissue distribution. Controversy exists as to whether these effects of sex hormones (oestrogen, progesterone and testosterone) on human adipose tissue are indirect or direct, as only very few studies have focused on steroid receptor status in human adipose tissue. In the present study, we reinvestigated steroid receptor status in human mature adipose tissue and human preadipocytes. Oestrogen, glucocorticoid and androgen receptors were found in human mature adipocytes from both women and men. The receptors were detected by ligand binding. Furthermore, the existence of the receptors was confirmed by demonstrating that adipocytes contained mRNA encoding the receptors. cDNA was generated using reverse transcriptase (RT) followed by polymerase chain reaction (PCR) amplification using specific primers (RT-PCR) for the specific steroid receptors. Adipocytes did not contain mRNA encoding the progesterone receptor (PR), and no progesterone binding was detectable in human adipocytes. Human preadipocytes contained glucocorticoid receptor (GR) mRNA and androgen receptor (AR) mRNA, whereas we were unable to detect oestrogen receptor (ER) mRNA and progesterone mRNA in human preadipocytes. In conclusion, oestrogen glucocorticoid and androgen receptors are present in mature adipocytes from subjects of both sexes, whereas adipocytes do not contain progesterone receptors. In preadipocytes, only glucocorticoid receptors and androgen receptors are present, whereas oestrogen receptors and progesterone receptors are not present.
...
PMID:Identification of steroid receptors in human adipose tissue. 901 78

Glucocorticoids are known to exert multiple effects upon neuronal systems and neuronal gene expression but the molecular mechanisms through which these effects are mediated are largely undefined. In this study, a transgenic mouse model that expresses a bovine vasopressin transgene was used to investigate the mechanisms by which this neuropeptide gene is repressed by glucocorticoids. Using both northern analysis and a reverse transcriptase polymerase chain reaction assay, depletion of glucocorticoids with the 11,beta-hydroxylase inhibitor metyrapone was shown to result in a dexamethasone-reversed increase in ectopic adrenal transgene messenger RNA levels. This result shows that sequences within the confines of the 3.5 kb transgene are sufficient to mediate repression by glucocorticoids, and indicates the involvement of a type II glucocorticoid receptor mechanism which is independent of cellular context. Evidence for the involvement of cis-acting repressive elements in the proximal 5' flanking sequence was obtained in further studies in which bovine transgene constructs were shown to be negatively regulated by dexamethasone in 293 cells. The further demonstration that recombinant glucocorticoid receptor binds to a vasopressin promoter fragment in an in vitro electrophoretic mobility shift assay provided additional evidence of a direct mechanism of repression. Both in vitro studies were consistent with the presence of a glucocorticoid regulatory element within the region -300 to 155 of the transcription start site. The use of an in vivo transgenic system combined with in vitro analyses of gene promoter fragments enabled the characterization of the molecular mechanisms which effect physiological changes in vasopressin gene expression, and provided evidence of a direct mechanism of repression mediated by sequences within the vasopressin gene promoter.
...
PMID:Repression of vasopressin gene expression by glucocorticoids in transgenic mice: evidence of a direct mechanism mediated by proximal 5' flanking sequence. 917 83

Alternative splicing of the human glucocorticoid receptor (hGR) primary transcript generates two receptor isoforms, hGRalpha and hGRbeta, with different carboxyl termini diverging at amino acid 727. By reverse transcriptase-polymerase chain reactions it was previously demonstrated that the hGRbeta message had a widespread tissue distribution. To demonstrate the presence of hGRbeta as protein we produced specific rabbit antisera to hGRbeta, as well as a hGRbeta-specific mouse monoclonal IgM antibody, by peptide immunizations. By SDS-polyacrylamide gel electrophoresis and Western immunoblotting we showed that hGRbeta is endogenously expressed at the protein level in HeLa cells and human lymphatic leukemia cells. Using an antibody directed against an epitope shared by both isoforms we showed a relatively lower expression of the hGRbeta form. We also showed that hGRbeta bound to hsp90 by immunoprecipitation of in vitro translated hGRbeta in reticulocyte lysate with hsp90-specific antibodies, a coprecipitation occurring also in the presence of dexamethasone. We could not demonstrate that hGRbeta inhibited the effects of dexamethasone-activated hGRalpha on a glucocorticoid-responsive reporter gene. In conclusion, low hGRbeta expression levels and hGRbeta-hsp90 interaction maintained in the presence of ligand and lack of inhibition of hormone-activated hGRalpha effects challenge the concept of the hGRbeta isoform as a proposed dominant negative inhibitor of hGRalpha activity.
...
PMID:Evidence that the beta-isoform of the human glucocorticoid receptor does not act as a physiologically significant repressor. 933 48

Two human glucocorticoid receptor (GR) isoforms, GRalpha and GRbeta, are derived from the same gene by alternative splicing involving exon 9 of the GR locus. The non-ligand binding isoform GRbeta was proposed to act as a transdominant negative inhibitor of GRalpha, thus modulating glucocorticoid responsiveness of target tissues. To study GRbeta in mice we characterized the genomic region around exon 9 of the murine GR gene. Sequence analysis revealed that the presumed exon 9beta contained an open reading frame of 59 amino acids. In contrast, human exon 9beta encoded only 15 amino acids. Using reverse transcriptase polymerase chain reaction the absence of GRbeta mRNA was demonstrated in all adult mouse tissues examined. To exclude the possibility that the polymerase chain reaction conditions employed were not suitable for the amplification of GRbeta mRNA, we synthesized an artificial template corresponding to the presumed GRbeta mRNA spanning exons 7, 8, and 9beta. Various amounts of this template were added to brain cDNA preparations and as little as 25 molecules were detectable under the polymerase chain reaction conditions chosen. Since GRbeta is not conserved across species its physiological significance in humans appears questionable.
...
PMID:Absence of glucocorticoid receptor-beta in mice. 933 49


1 2 3 4 Next >>

---