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)

The adeno-associated virus (AAV) rep gene encodes four proteins (Rep78, Rep68, Rep52, and Rep40) required for AAV DNA replication and AAV gene regulation. In addition, the Rep proteins may have pleiotropic regulatory effects in heterologous systems, and in particular Rep78 may mediate a negative regulatory effect. We analyzed the effects of the AAV rep gene on human immunodeficiency virus type 1 (HIV-1) gene expression. The rep gene proteins of AAV type 2 (AAV2) inhibited the trans-activating ability of HIV-1. Constructs containing the AAV2 rep gene (pHIVrep) or a CAT gene (pBennCAT) expressed from the 5' HIV-1 long terminal repeat were inducible for Rep78 and Rep68 or CAT expression, respectively, when cotransfected with a plasmid containing the HIV-1 tat gene (pARtat). When equivalent amounts of pHIVrep and pBennCAT were cotransfected with increasing amounts of pARtat, expression of CAT activity was decreased. The pHIVrep construct was more inhibitory than plasmids expressing rep from the wild-type AAV2 p5 transcription promoter. rep expression from pHIVrep almost completely inhibited the replication of an HIV-1 proviral clone as measured by reverse transcriptase activity and p24 protein levels. Inhibition of HIV-1 production by Rep protein was also seen at the transcriptional level in that all HIV-1 transcripts were decreased when pHIVrep was present. The inhibitory effects of pHIVrep appear to be mediated primarily by Rep78 and perhaps Rep68. These results suggest that a trans-acting protein from a heterologous virus might be used to inhibit HIV-1 growth.
...
PMID:Adeno-associated virus Rep protein inhibits human immunodeficiency virus type 1 production in human cells. 184 99

Human immunodeficiency virus type 1 (HIV-1) NEF protein has been demonstrated to be a negative regulator of HIV-1 replication and HIV-1 LTR transcription under transient expression conditions. The difficulty of several laboratories to reproduce these findings led us to reexamine the role of NEF in HIV-1 provirus expression and HIV-1 LTR transcription. Basal transcription from the HIV-1 LTR in the presence of a NEF expression vector was compared to that in the presence of a mutated NEF vector. NEF expression led to a greater than 10-fold repression of LTR transcription under these conditions. HeLa and Jurkat cell lines carrying the nef gene linked to the CMV promoter or the HIV-1 LTR were isolated by coselection for neomycin resistance. Single cell isolates were further selected for the expression of nef transcripts. With the exception of the anti-sense nef cell lines, all the nef cell lines expressed the 27-kDa NEF protein, detectable by immunoprecipitation. NEF+ HeLa cell lines were at least 5-fold less efficient than NEF- HeLa cell lines in transient proviral expression. Provirus expression was also repressed in the NEF+ Jurkat cell lines. TAT-activated LTR transcription from an HIV-1 LTR-linked CAT expression vector was repressed 10-fold in the NEF+ HeLa and NEF+ Jurkat cell lines. When infected with HIV-1, NEF expressing T lymphoid cell lines showed moderate delays in onset and peak of reverse transcriptase production. However, none of these cell lines completely arrested virus replication. Our data confirm a negative regulatory effect of NEF on both virus production and LTR driven CAT expression in the cell lines tested. It is possible that cell specific factors may influence NEF activity.
...
PMID:Human immunodeficiency virus type 1 (HIV-1) provirus expression and LTR transcription are repressed in NEF-expressing cell lines. 202 88

We have isolated the human prointerleukin 1 (proIL-1) beta gene from leukocyte and fetal liver libraries. The nucleotide sequence and its gene organization reveals that the proIL-1 beta gene is composed of seven exons with a primary transcription product length of 7,008 nucleotides. The exon sequence agrees well with that of the human proIL-1 beta cDNA. Features of interest within the transcriptional unit include positioned TATA, CAT, and poly-adenylation signals for gene regulation, as well as the signatures of gene duplication via retrotransposition in the form of flanking direct repeats and a genomic poly A tail. The genomic organization of the proIL-1 beta gene with respect to the number and position of exon boundaries is strikingly similar to that of the recently reported human proIL-1 alpha gene. Therefore, we hypothesize that the proIL-1 beta may have arisen by a reverse transcriptase mediated duplication of the related alpha gene.
...
PMID:Genomic sequence for human prointerleukin 1 beta: possible evolution from a reverse transcribed prointerleukin 1 alpha gene. 349 Jun 54

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

Reducing agents such as glutathione (GSH), glutathione ester (GSE), and N-acetylcysteine (NAC) have been shown to suppress the induction of HIV expression in chronically infected cells stimulated by cytokines. We present data which show the effects of the organic thiophosphate WR-151327 on the expression of latent HIV in U1 cells. The chronically infected promonocytic cell line U1 constitutively expresses low levels of HIV that can be increased by 13-phorbol 12-myristate acetate (PMA), tumor necrosis factor alpha (TNF-alpha), and granulocyte/monocyte colony-stimulating factor (GM-CSF). WR-151327 suppressed, in dose-dependent fashion, the reverse transcriptase (RT) activity induced by TNF-alpha, GM-CSF, and PMA. The maximal decrease in RT activity was 70, 80, and 50%, respectively. Pretreatment with WR-151327 also suppressed the induction of total HIV protein synthesis, as shown by Western blot analysis. In addition, WR-151327 suppressed HIV-LTR-CAT activity in transfected human rhabdomyosarcoma cells (RD). Suppression of HIV expression by WR-151327 was observed in the absence of a cytotoxic or cytostatic effect. Incubation of WR-151327 with human recombinant TNF-alpha for 6 hr at 37 degrees C did not alter the capacity of TNF-alpha to induce the expression of HIV. Our observations further support the hypothesis that reducing agents are important in the control of HIV replication and that the clinical evaluation of WR-151327 may be indicated.
...
PMID:Organic thiophosphate WR-151327 suppresses expression of HIV in chronically infected cells. 752 Nov 93

Foscarnet (phosphonoformic acid) is a pyrophosphate analog that inhibits the replication of human immunodeficiency virus type 1 (HIV-1) in vitro and in patients with AIDS. HIV-1 resistance to foscarnet has not been reported despite long-term foscarnet therapy of AIDS patients with cytomegalovirus disease. We therefore attempted to select foscarnet-resistant HIV-1 in vitro by serial endpoint passage of virus in 400 microM foscarnet. After 13 cycles of passage in MT-2 cells, virus exhibiting > or = 8.5-fold foscarnet resistance was isolated. The reverse transcriptase (RT) from resistant virions exhibited a similar level of foscarnet resistance in enzyme inhibition assays (approximately 10-fold resistance). Foscarnet-resistant virus showed increased susceptibility to 3'-azido-3'-deoxythymidine (90-fold) and to the HIV-1-specific RT inhibitors TIBO R82150 (30-fold) and nevirapine (20-fold). DNA sequence analysis of RT clones from resistant virus revealed the coexistence of two mutations in all clones: Gln-161 to Leu (CAA to CTA) and His-208 to Tyr (CAT to TAT). Sequence analysis of six clinical HIV-1 isolates showing reduced susceptibility to foscarnet revealed the Tyr-208 mutation in two, the Leu-161 mutation in one, and a Trp-88-to-Ser or -Gly mutation in four isolates. Site-specific mutagenesis and production of mutant recombinant viruses demonstrated that the Leu-161, Ser-88, and Tyr-208 mutations reduced HIV-1 susceptibility to foscarnet 10.5-, 4.3-, and 2.4-fold, respectively, in MT-2 cells. In the crystal structure of HIV-1 RT, the Gln-161 residue lies in the alpha E helix beneath the putative deoxynucleoside triphosphate (dNTP) binding site. The Gln-161-to-Leu mutation may affect the structure of the dNTP binding site and its affinity for foscarnet. The location of the Trp-88 residue in the Beta5a strand of HIV-1 RT suggest that the Ser-88 mutation affects template-primer binding, as do several mutations that affect RT susceptibility to nucleoside analogs.
...
PMID:Novel mutations in reverse transcriptase of human immunodeficiency virus type 1 reduce susceptibility to foscarnet in laboratory and clinical isolates. 754 60

The high sensitivity of reverse transcriptase-polymerase chain reaction for detecting low copy number mRNA transcripts has been standardized to analyze the mRNA profiles of catalase, glutathione peroxidase, CuZn-superoxide dismutase and aldose reductase, with respect to the housekeeping gene cyclophilin, in rat lenses cultured in hyperglycemic (50mM glucose) or oxidative (100 microM H2O2) media for 24, 40 and 60 hr. In response to hyperglycemia mRNA expression of catalase appeared to be inhibited at 24 hr but attained normal levels by 40 hr. On the other hand, mRNA levels of catalase were higher than normal between 40 and 60 hr in the presence of H2O2. Glutathione peroxidase mRNA abundance although enhanced in response to both hyperglycemia as well as H2O2-induced stress, displayed opposite trends with time-an increase from 24-60 hr due to hyperglycemia and a decrease to normal by 60 hr in the presence of H2O2. In contrast, CuZn-superoxide dismutase was inhibited at 50 mM glucose achieving baseline levels by 60 hr, while H2O2 elicited an induction at 24 hr which waned to basal levels by 60 hr. Interestingly, aldose reductase was unaffected by hyperglycemia but showed an appreciable increase with time upon exposure of the lens to H2O2. The role of these enzymes in cataractogenesis with regard to their respective mRNA levels is discussed.
...
PMID:Semi-quantitation of mRNA by polymerase chain reaction. Levels of oxidative defense enzymes and aldose reductase in rat lenses cultured in hyperglycemic or oxidative medium. 873 24

Using the human T-cell leukemia virus type I (HTLV-I) infected SLB-I T-cell line, we showed in this study that 5-d treatment with the maximal subtoxic 3-methylcholanthrene (3-MC) dose (0.25 microgram/ml), as well as with a 3-MC dose that inhibits 50% of the cell growth (5 micrograms/ml), profoundly increased the level of viral RNA. Exposure to these 3-MC doses for 5 d before transient transfection of HTLV-I LTR-CAT construct into these cells markedly stimulated CAT activity, indicating that 3-MC exerted its effect by a trans-acting mechanism. A similar stimulation was observed when this construct was transfected into 3-MC treated uninfected Jurkat cells, indicating that this trans-acting effect was independent of the viral tax protein. However, although the subtoxic 3-MC dose increased also the capacity of SLB-I cells to transmit the virus to normal peripheral blood lymphocytes in coculture, the toxic dose strongly reduced this capacity. No inhibition by this toxic dose was observed in the viral protein synthesis or processing nor in the final release of the virus from the cells. However, the virions released under the influence of this 3-MC dose were found to contain mainly the uncleaved gag precursor polypeptide and a low level of reverse transcriptase. Thus, the reduced virus transmission capacity of the host cells can be ascribed to this structural defect, which presumably lowered the viral infectivity.
...
PMID:Tax-independent stimulation of human T-cell leukemia virus type-I expression and differential effects on its infectivity by subtoxic and toxic doses of 3-methylcholanthrene. 886 84

We previously reported that monocyte adhesion to tumor necrosis factor-alpha (TNF-alpha)-treated endothelial cells increased expression of tissue factor and CD36 on monocytes. Using immunological cross-linking to mimic receptor engagement by natural ligands, we now show that CD15 (Lewis X), a monocyte counter-receptor for endothelial selectins may participate in this response. We used cytokine production as a readout for monocyte activation and found that CD15 cross-linking induced TNF-alpha release from peripheral blood monocytes and cells from the monocytic cell line MM6. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) showed an increase in steady-state TNF-alpha mRNA after 3 to 4 hours of cross-linking. CD15 cross-linking also concomitantly increased interleukin-1 beta (IL-1 beta) mRNA, while no apparent change was observed in the levels of beta-actin mRNA, indicating specificity. To examine transcriptional regulation of cytokine genes by CD15 engagement, a CAT plasmid reporter construct containing IL-1 beta promoter/enhancer sequences was introduced into MM6. Subsequent cross-linking of CD15 increased CAT activity. CD15 engagement by monoclonal antibody also attenuated IL-1 beta transcript degradation, demonstrating that signaling via CD15 also had posttranscriptional effects. Nuclear extracts of anti-CD15 cross-linked cells demonstrated enhanced levels of the transcriptional factor activator protein-1, minimally changed nuclear factor-kappa B, and did not affect SV40 promoter specific protein-1. We conclude that engagement of CD15 on monocytes results in monocyte activation. In addition to its well-recognized adhesive role, CD15 may function as an important signaling molecule capable of initiating proinflammatory events in monocytes that come into contact with activated endothelium.
...
PMID:Engagement of the Lewis X antigen (CD15) results in monocyte activation. 897 6

Androgens have significant beneficial effects on the skeleton. However, studies on the effects of androgens on osteoblasts are limited due to the absence of appropriate model systems that combine completeness of the osteoblastic phenotype, rapid proliferation rate, and stable expression of the androgen receptor (AR). Thus, we stably transfected the conditionally immortalized human fetal osteoblastic cell line (hFOB) with the human wild-type AR (hAR) cDNA. Compared to nontransfected hFOB cells, constitutive hAR mRNA expression in three independent hAR-transfected hFOB clones (hFOB/AR) was 15-fold higher in hFOB/AR-16, 62-fold higher in hFOB/AR-2, and 72-fold higher in hFOB/AR-6 cells, respectively, as assessed by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Detectable constitutive levels of hAR mRNA by Northern blot analysis were present in hFOB/AR-2 and hFOB/AR-6 cells, but not in hFOB/AR-16 or hFOB cells, respectively. Treatment with 5 alpha-dihydrotestosterone (5 alpha-DHT) (10(-8) M) for 24 h did not alter hAR mRNA steady state levels in the hFOB/AR cell lines. Nuclear binding studies demonstrated 152 +/- 73 (mean +/- SEM) functional hARs/nucleus in non-transfected hFOB cells, 3,940 +/- 395 functional hARs/nucleus in hFOB/AR-2 cells, and 3,987 +/- 823 hARs/nucleus in hFOB/AR-6 cells, respectively. Treatment with 5 alpha-DHT increased the expression of a transiently transfected androgen response element-chloramphenicol acetyltransferase (ARE-CAT) reporter construct in hFOB/AR-6 cells in a dose- and time-dependent manner; no such effect was observed in transiently transfected hFOB cells lacking exogenously transfected hARs. Moreover, 5 alpha-DHT-induced ARE-CAT expression was inhibited by the selective androgen receptor antagonist, hydroxyflutamide. In summary, we have developed and characterized androgen-responsive osteoblastic cell lines derived from normal human fetal bone that express physiological levels of functional hARs. These cell lines should provide a suitable model for further studies on the effects of androgens on osteoblast function, including the identification of potential androgen-regulated growth factors and cytokines.
...
PMID:Development and characterization of a conditionally immortalized human osteoblastic cell line stably transfected with the human androgen receptor gene. 928 32


1 2 3 4 5 6 7 8 Next >>

---