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)

NF kappa B is a potent mediator of specific gene expression in human monocytes and has been shown to play a role in transcription of the HIV-1 genome in promonocytic leukemias. There is little information available on the response of NF kappa B to cytokines in normal human monocytes. We have used a 32P-labeled oligonucleotide derived from human immunodeficiency virus (HIV-1) long terminal repeat, which contains a tandem repeat of the NF kappa B binding sequence, as a probe in a gel retardation assay to study this transcription factor. Using this assay, we have detected NF kappa B in extracts of nuclei from normal human monocytes. Treatment of normal monocytes with 12-0-tetradecanoyl phorbol-13-acetate (TPA) for 4-24 h caused the complete disappearance of NF kappa B from nuclear extracts of monocytes. A similar result was obtained with the mature monocytic leukemia cell line THP-1. The constitutive transcription factor SP1 was unaffected by addition of TPA. The disappearance of NF kappa B from the nucleus was concentration dependent between 10 and 50 ng/ml of phorbol ester. In THP-1 cells, TPA also induced a new, faster-migrating NF kappa B species not induced in monocytes. Protein kinase C inhibitor staurosporine, but not cyclic nucleotide-dependent protein kinase inhibitor HA-1004, also dramatically reduced constitutive levels of nuclear NF kappa B. Finally, TPA addition to monocytes infected with HIV-1 inhibited HIV-1 replication, as determined by reverse transcriptase assays, in a concentration-dependent manner. These results are in striking contrast to the increase in nuclear NF kappa B and HIV-1 replication induced by phorbol esters in promonocytic leukemia cells U937 and HL-60, and emphasize the importance of studying cytokine regulation of HIV-1 in normal monocytes.
...
PMID:Phorbol ester reduces constitutive nuclear NF kappa B and inhibits HIV-1 production in mature human monocytic cells. 146 36

In vitro assessment of biological properties of 14 independent isolates of human immunodeficiency virus type 1 (HIV-1) was performed in order to gain insight into the spectrum of behavioral diversity of HIV-1s and to attempt to identify phenotypic traits that may be eventually correlated with in vivo pathogenesis. All of these biologically cloned isolates were found to spread very slowly in most cell cultures, requiring 8-10 weeks for virus to spread from a few infected cells to around 10(5) cells. If viral synergistic activity was also present, as in HTLV-1-infected cells, HIV-1 spread was greatly accelerated. The isolates varied in their cellular tropisms, having as much as 100,000-fold difference in their tropisms for various human CD4-positive cell lines. Several HIV isolates were dual-tropic for both T and promonocytic cells, but some of these isolates did not readily infect U937 promonocytes while readily infecting THP-1 promonocytes. Both the slow spread and extreme tropisms of HIV-1 isolates have practical implications for titering HIVs and for initiating any studies examining the interaction between a given isolate and any given cell. Some isolates did not score readily by reverse transcriptase assays while others did and this did not reflect the amount of infectious virus produced. These findings raise questions about the reliability of HIV quantitation by RT assay. The HIV isolates further varied in their ability to kill and/or fuse cells, whereas some induced cytopathology more efficiently in a given cell line than others, even though the latter appeared to replicate as well. Finally, most isolates killed cells without syncytia formation, demonstrating that cell-to-cell fusion is a minor mechanism of cytopathology. The properties observed for each HIV isolate appeared to be stable phenotypes for that virus and the diversity of biological behavior raises the possibility that independent HIV isolates may differ in their virulence properties in vivo as well.
...
PMID:Spectrum of biological properties of human immunodeficiency virus (HIV-1) isolates. 168 73

Human immunodeficiency virus type 1 (HIV-1) contains an open reading frame called nef at the 3' end of its genome. The nef gene product has been reported to down-regulate viral growth by suppressing viral transcription through interaction with the long terminal repeat region. We have compared two isogenic HIV-1 (HIV-1-WI3) strains, one of which lacks nef expression, and found little difference between them in in vitro growth. We tested effects on viral entry, DNA synthesis, and RNA expression by measuring HIV-specific low molecular weight DNA and RNA after infection. The qualitative and quantitative aspects of DNA and RNA synthesis were comparable between the nef+ and nef- strains. The effects on viral growth were also examined by following changes in reverse transcriptase activity during the course of infection. The presence of the nef gene product failed to slow viral growth in several different cell types tested, including the human T-lymphocyte cell lines H9 and CEM-SS, human primary T cells enriched for CD4+ cells, and human monocytic cell lines U-937 and THP-1. On the contrary, the nef+ strain grew more efficiently in some cell types than the nef- strain. The same results were obtained with nef+ and nef- strains of a different virus, HIV-1-432, whose Nef had been reported to have a negative effect on viral growth. Our data suggest that the Nef protein does not act as a negative factor, at least in the experimental systems employed in our studies.
...
PMID:Lack of a negative influence on viral growth by the nef gene of human immunodeficiency virus type 1. 268 83

Macrophage activation resulting from phagocytosis has the potential to modulate human immunodeficiency virus (HIV) replication. We have determined the effects of phagocytosis of particulate stimuli on transcription and release of HIV. Using THP-1 and Mono Mac 6 human monocytic cell lines transfected with HIV long terminal repeat sequence chloramphenicol acetyltransferase (LTR CAT) constructs we have demonstrated that phagocytosis of Mycobacterium tuberculosis enhanced HIV-1 and -2 LTR CAT expression. However phagocytosis of zymosan or inert latex beads had little or no effect on CAT expression. Enhancement of HIV LTR CAT expression was dependent upon intact NF-kappa B binding sites and was independent of tumour necrosis factor alpha secretion. M. tuberculosis strains of different degrees of virulence induced similar levels of enhanced CAT expression. In contrast, phagocytosis of M. tuberculosis by HIV-1-infected THP-1 cells reduced supernatant reverse transcriptase (RT) activity without suppression of p24 antigen release. Phagocytosis of zymosan granules or latex particles did not alter released RT activity. However, phagocytosis of either M. tuberculosis, zymosan granules or latex particles by HIV-1-infected human peripheral blood monocyte-derived macrophages reduced supernatant RT activity. These data indicate that phagocytosis of M. tuberculosis may enhance HIV transcription in monocytic cells although it may reduce release of intact HIV.
...
PMID:Phagocytosis of Mycobacterium tuberculosis modulates human immunodeficiency virus replication in human monocytic cells. 751 19

Macrophage adherence, an important regulatory signal, has the potential to affect human immunodeficiency virus (HIV) production either directly or by priming monocytes to respond to other activating signals. We have investigated the role of adherence as an activator of HIV-1 transcription and release. The effects of adherence on HIV-1 transcription were examined by using THP-1 cells, a human monocytic cell line, transfected with HIV long terminal repeat (LTR)-chloramphenicol acetyltransferase (CAT) constructs. The effects of adherence on release of HIV-1 were investigated in both HIV-1-infected THP-1 cells and human peripheral blood monocyte-derived macrophages (MDM). Adherence of lipopolysaccharide (LPS)-stimulated THP-1 cells to either tissue culture plastic or endothelial cells was crucial for enhanced HIV-1 transcription as measured by LTR-CAT expression. Such increased LTR-CAT expression did not occur with an HIV LTR construct containing mutated NF-kappa B binding sites. In contrast, release of whole HIV, measured by reverse transcriptase (RT) activity in tissue culture medium, was reduced upon adherence of stimulated HIV-1-infected THP-1 cells without suppression of HIV LTR-CAT transcription or p24 release. This finding suggested that activation of adherent monocytic cells interfered with HIV assembly and release. Although the reduction of RT activity following activation of HIV-1-infected MDM was independent of adhesion, adherence alone of nonstimulated HIV-infected MDM to endothelial cells was sufficient to induce a reduction in RT release. This study demonstrates that LPS stimulation of monocytic cells enhances HIV LTR transcription under adherent conditions. In contrast, activation of adherent monocytic cells infected with HIV reduced viral release.
...
PMID:Release of human immunodeficiency virus by THP-1 cells and human macrophages is regulated by cellular adherence and activation. 768 70

The reduced progesterone metabolite tetrahydroprogesterone (3 alpha-hydroxy-5 alpha-pregnan-20-one; 3 alpha,5 alpha-THP) is a positive modulator of the gamma-aminobutyric acid type A (GABAA) receptor. Experiments performed in vitro with hypothalamic fragments have previously shown that GABA could modulate the release of gonadotropin-releasing hormone (GnRH). Using GT1-1 immortalized GnRH neurons, we investigated the role of GABAA receptor ligands, including 3 alpha,5 alpha-THP, on the release of GnRH. We first characterized the GABAA receptors expressed by these neurons. [3H]Muscimol, but not [3H]flunitrazepam, bound with high affinity to GT1-1 cell membranes (Kd = 10.9 +/- 0.3 nM; Bmax = 979 +/- 12 fmol/mg of protein), and [3H]muscimol binding was enhanced by 3 alpha,5 alpha-THP. mRNAs encoding the alpha 1 and beta 3 subunits of the GABAA receptor were detected by the reverse transcriptase polymerase chain reaction. In agreement with binding data, the benzodiazepine-binding gamma subunit mRNA was absent. GnRH release studies showed a dose-related stimulating action of muscimol. 3 alpha,5 alpha-THP not only modulated muscimol-induced secretion but also stimulated GnRH release when administered alone. Bicuculline and picrotoxin blocked the effects of 3 alpha,5 alpha-THP and muscimol. Finally, we observed that GT1-1 neurons convert progesterone to 3 alpha,5 alpha-THP. We propose that progesterone may increase the release of GnRH by a membrane mechanism, via its reduced metabolite 3 alpha,5 alpha-THP acting at the GABAA receptor.
...
PMID:A progesterone metabolite stimulates the release of gonadotropin-releasing hormone from GT1-1 hypothalamic neurons via the gamma-aminobutyric acid type A receptor. 773 81

Mononuclear phagocytes infected with human immunodeficiency virus 1 (HIV-1) produce soluble factors that kill neurons in culture. To define the molecular events that lead to neuron killing, HIV-1 proteins were tested for the ability to trigger release of neurotoxins from human monocytes and lymphocytes. None of the recombinant-derived HIV-1 proteins examined (reverse transcriptase, protease, gag, nef, or gp120) were directly neurotoxic at concentrations from 100 pM to 10 nM. The envelope glycoprotein gp120 did, however, stimulate both isolated human blood monocytes and the monocytoid line THP-1 (but not lymphocytes or the lymphoid cell line H9) to discharge neurotoxic factors. These toxins consisted of heat-stable, protease-resistant molecules (< 500 Da) that copurified with neurotoxins from HIV-1-infected THP-1 cells and were blocked by antagonists to N-methyl-D-aspartate receptors. Release of neurotoxins through gp120 stimulation involved monocytoid CD4 receptors because toxin production could be inhibited either by a monoclonal antibody to the CD4-binding region of gp120 or by soluble CD4 receptors. Alternatively, production of neuron-killing factors could be induced with a peptide from the CD4-binding region of gp120. These data show that the HIV-1 envelope glycoprotein alone can stimulate neurotoxin release by binding to CD4 receptors of mononuclear phagocytes. Such neurotoxic factors may, in turn, contribute to the central nervous system dysfunction associated with HIV-1 by acting on neurons through N-methyl-D-aspartate receptors.
...
PMID:The envelope glycoprotein of human immunodeficiency virus type 1 stimulates release of neurotoxins from monocytes. 846 87

Certain osteoclastic markers (multinucleation and tartrate-resistant acid phosphatase) were induced in human leukemia HL-60 cells by treatment with 10(-7) M 1,25-dihydroxy-vitamin D3 [1,25(OH)2D3] for 10 days. However, no formation of pits on a bone substrate by vitamin-treated HL-60 cells was detected. Expression of calcitonin receptors (CTR), another osteoclastic marker, was examined by means of the reverse transcriptase polymerase chain reaction. The human CTR-cDNA (T47D isotype) was amplified from untreated HL-60 cells, but not from cells treated with 1,25(OH)2D3. The CTR mRNA disappeared within 24 h after the treatment. Thus, 1,25(OH)2D3-differentiated HL-60 cells failed to show two intrinsic characteristics of osteoclasts, pit formation on a bone substrate and expression of CTR. We then examined the expression of CTR on established human leukemia cell lines. The CTR mRNA was expressed in myeloblastic ML-1 and promyelocytic HL-60 leukemia cells but not in more mature macrophage-like cell lines, U-937 and THP-1 cells. Neither B cell leukemia BALL-1, T cell leukemia Jurkat, promegakaryoblastic leukemia Meg-J, nor cervix uteri carcinoma HeLa S3 cells amplified the CTR products. The cDNA of BIN67-isotype CTR, that has an additional 16-amino acid insert in the putative first intracellular loop of T47D-type CTR [Kuestner et al. (1994) Mol. Pharmacol. 46, 246-255], was amplified by neither strain tested. It was suggested that the T47D-type CTR is a novel differentiation antigen of immature myeloid lineage cells.
...
PMID:Expression of calcitonin receptors on human myeloid leukemia cells. 854 84

In situ hybridization studies have shown that at early but not late stages of gestation, human placental stromal cells, many of which are macrophages (Hofbauer cells), contain HLA-G message. In this study, the HLA-G protein was identified in the macrophage-like stromal cells by immunohistochemistry using the anti-HLA-G mAb, 87G. Expression of the HLA-G gene was then analyzed in macrophage cell lines (U937, HL-60, THP-1) and blood monocytes. HLA-G mRNA identified by using reverse transcriptase PCR was consistent with production of a transcript containing intron 4, which codes for a soluble form of HLA-G. Low levels of HLA-G mRNA were identified in mononuclear phagocytes by Northern blot hybridization, and little if any HLA-G Ag was detectable. By contrast, essentially all of the cells displayed high levels of HLA-B/C H chains detected by the mAb, 4E, and B2m. Treatment of macrophage cell lines and monocytes with IFN-gamma increased steady-state levels of HLA-G mRNA, stimulated higher levels of cell surface and intracellular HLA-G Ag in a dose-dependent manner, and increased the proportions of HLA-G relative to HLA-B/C. INF-alpha and IFN-beta enhanced steady-state levels of HLA-G mRNA and in some lines modestly increased the numbers of weakly positive cells but were poor inducers of cell-surface and intracellular HLA-G and did not increase HLA-G relative to HLA-B/C. Thus, mononuclear phagocytes express low levels of HLA-G mRNA and protein, and IFN-gamma selectively enhances expression of this HLA class Ib gene relative to HLA class Ia, which could influence the repertoire of peptides presented during embryogenesis as well as during inflammatory situations in adults. Soluble HLA-G might influence both fetal and maternal immune responses.
...
PMID:Expression of HLA-G in human mononuclear phagocytes and selective induction by IFN-gamma. 866 91

Receptors for the Fc portion of IgA (Fc alpha R) trigger important immunological elimination processes against IgA-coated targets. Investigation of human Fc alpha R (CD89) transcripts in neutrophils, eosinophils and a monocyte-like cell line, THP-1, with the use of reverse transcriptase PCR, Northern blotting and RNase protection analysis, has provided evidence in these cell types for at least two distinct transcripts generated by alternative splicing. The cDNAs derived from the two major transcripts of both neutrophils and eosinophils have been cloned and sequenced. For both cell types, the larger clone represents the previously described full-length receptor, whereas the second, shorter, splice variant lacks the entire second, membrane-proximal, Ig-like domain. Stable CHO-K1 transfectants have been obtained for both full-length and truncated variant neutrophil receptors. Whereas the full-length receptor is recognized by a panel of five anti-Fc alpha R monoclonal antibodies (mAbs), the shorter variant is bound weakly by only two of the antibodies, suggesting that the epitopes recognized by the majority of the mAbs lie at least in part in the second Ig-like domain of Fc alpha R. Both full-length and splice variant forms of the receptor bind secretory IgA, but the weak binding to serum IgA seen with the full-length receptor is not evident with the shorter variant. Alternative splicing might therefore serve as a means of diversifying Fc alpha R structure and function.
...
PMID:Alternative splicing of the human IgA Fc receptor CD89 in neutrophils and eosinophils. 883 18


1 2 3 4 5 6 7 Next >>

---