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:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have used a soluble in vitro RNA polymerase II transcription system to define the site of initiation of Moloney murine leukemia viral RNA synthesis. Molecularly cloned integrated and unintegrated Moloney murine leukemia virus DNAs were used as templates. The 5' ends of in vitro transcripts and virion RNA of Moloney murine leukemia virus were compared by nuclease S1 protection experiments. Our results indicate that viral sequences upstream of the in vivo cap site are implicated in the transcription of viral RNA and that the 5' end of an in vitro transcript derived from an integrated Moloney murine leukemia virus clone corresponds to the 5' end of viral genomic RNA.
...
PMID:Identification of a RNA polymerase II initiation site in the long terminal repeat of Moloney murine leukemia viral DNA. 694 80

The ATP analog 5'-adenylyl imidodiphosphate (AMP-PNP) inhibits transcription of specific genes by the RNA polymerase II contained in whole cell extracts, not only with promoters that contain A as the first nucleotide of the transcript, but also with those that initiate transcripts with G or U. The analog AMP-PNP (a competitive inhibitor of ATP) probably acts at the level of initiation of transcription, but it can be used for elongation by RNA polymerase II in isolated nuclei or in the whole cell extract. AMP-PNP and the other imidotriphosphates have little effect on purified HeLa cell RNA polymerase II initiation and elongation of transcription. Since RNA polymerase III in the crude system both initiates and elongates transcripts with AMP-PNP, we conclude that the availability of the beta-gamma bond of ATP is an indispensable requirement for faithful and specific in vitro initiation only by RNA polymerase II in the whole cell extract. Uncapped U- or G-initiated transcripts were obtained in the presence of UMP-PNP or GMP-PNP, the respective imidodiphosphate analogs. The presence of the 5'-terminal imidotriphosphate at the same oligonucleotide as the cap for U-initiated precursors established that transcription initiation and capping occur at the same site. Capping is not required for transcription by RNA polymerase II in the in vitro system. Methylation of the 2' ribose of the initiating nucleotide does not occur on the imidonucleotide containing 5' ends of adenovirus EIV or murine leukemia virus long terminal repeat.
...
PMID:Mechanism of RNA polymerase II--specific initiation of transcription in vitro: ATP requirement and uncapped runoff transcripts. 715 Nov 73

Infection of human or murine cells with murine leukemia viruses rapidly increases the expression of a number of genes that belong to the immunoglobulin superfamily and are involved in T-lymphocyte activation, including the class I major histocompatibility complex antigens. We have reported recently that the long terminal repeat (LTR) of Moloney murine leukemia virus encodes a trans activator which induces transcription and expression of class I major histocompatibility complex genes and certain cytokine genes. The portion of the LTR responsible for trans activation was mapped by deletions to lie within the U3 region. We demonstrate here that a transcript is initiated within the U3 region and that its presence correlates with the trans-activating activity. Analysis of the LTR region reveals a potential internal promoter element for RNA polymerase III transcription within the U3 region. Studies with polymerase inhibitors suggest that this LTR transcript, designated let (LTR-encoded trans activator), is a product of RNA polymerase III. The mechanisms whereby RNA leukemia viruses cause lymphoid neoplasia after a long latent period have been extensively studied but are only partially understood. The region of the LTR identified here as being important in trans activation has recently been shown to be a critical determinant of the leukemogenicity and latency of Moloney murine leukemia virus. These findings suggest a novel mechanism of retrovirus-induced activation of cellular gene expression, potentially contributing to leukemogenesis.
...
PMID:A transcript from the long terminal repeats of a murine retrovirus associated with trans activation of cellular genes. 747 25

Fli-1, an ets related gene, was found to be rearranged in 75% of erythroleukemias induced by Friend murine leukemia virus. We have shown previously that the Fli-1 gene codes for a sequence specific transcriptional activator which contains two autonomous transcriptional activation domains, one at the amino terminal region and the other at the carboxy terminal region. Recently human Fli-1 gene was shown to be involved in Ewing's sarcoma and related subtypes of primitive neuroectodermal tumors which share t(11;22) (q24;q12) chromosome translocation. In these tumors the carboxyl terminal region of Fli-1 was found to be fused with the amino terminal region of a putative RNA binding protein, EWS. Because part of the amino terminal transcriptional activation domain of Fli-1 was replaced with the amino terminal domain of the EWS (NTD-EWS) which shares homology with RNA polymerase II, it was speculated that NTD-EWS may interfere with RNA pol II function. Alternatively, NTD-EWS could also contribute to the transcriptional activation function of EWS/Fli-1 chimeric protein by providing either a modulatory/regulatory domain or a novel transcriptional activation domain. Here we show that EWS/Fli-1 chimeric protein functions as a transcriptional activator. Deletion analysis reveals that the EWS domain functions as a modulatory/regulatory domain for the transcriptional activation properties of the carboxy terminal transcriptional activation domain of EWS/Fli-1. We therefore propose that replacement of the amino terminal transcriptional activation domain of the Fli-1 protein with the regulatory domain of NTD-EWS results in the activation of the carboxy terminal transcriptional activation domain of Fli-1 which may be the molecular mechanism involved in these human tumors.
...
PMID:EWS/Fli-1 chimeric protein is a transcriptional activator. 750 13

Reverse transcriptase (RT) is an indispensable component of infectious retroviruses. We have developed an ultrasensitive RT test in which RNA of bacteriophage MS2 serves as the template for RT-mediated cDNA synthesis. A fragment of the cDNA is selectively amplified by polymerase chain reaction and the amplification product is analyzed by Southern blot hybridization or enzyme immunoassay. The procedure was 10(6) to 10(7) times more sensitive than a conventional RT test and detected as little as 10(-9) unit of murine leukemia virus RT, which corresponded to 2.1 x 10(2) molecules, a number present in 3-11 virions. As a screening assay for filterable particle-associated RT, it was positive with supernatants from cell cultures producing human immunodeficiency virus (HIV) type 1 or human T-cell leukemia virus (HTLV) type 1 or 2, but was negative with nonproducer cultures. It was positive with plasma samples from all tested individuals infected with HIV-1, HIV-2, or HTLV-1 and sera from cats infected with feline leukemia virus or feline immunodeficiency virus. Control samples from blood donors or uninfected cats were negative. Density banding experiments with culture supernatants showed that the RT activity was associated with virus particles. The assay should detect all replication-competent retroviruses or similar agents. It may be used as a screening assay for such agents, for quantitation of the viral load, drug susceptibility testing of RT, and control of virus inactivation in biological products.
...
PMID:Ultrasensitive retrovirus detection by a reverse transcriptase assay based on product enhancement. 750 77

Inophyllums are novel non-nucleoside inhibitors of human immunodeficiency virus (HIV) type 1 reverse transcriptase identified through an enzyme screening program and isolated from the plant Calophyllum inophyllum. The kinetics of reverse transcriptase inhibition by inophyllum B were characterized using recombinant purified enzyme, a heteropolymeric RNA template, and a scintillation proximity assay. Preincubation of inhibitor with the enzyme-template-primer complex for 11 min was required for maximal inhibition of reverse transcriptase to occur, suggesting that inophyllum B had a slow on-rate and that template-primer must bind to reverse transcriptase prior to inhibitor binding. Inhibition of reverse transcriptase by inophyllums was shown to be reversible. When thymidine triphosphate was the variable substrate, inophyllum B inhibited reverse transcriptase noncompetitively with a Ki of 42 nM. Enzyme inhibition with respect to template-primer was uncompetitive with a Ki of 26 nM. Reverse transcriptase enzymes containing point mutations in which tyrosine 181 was changed to either cysteine or isoleucine exhibited marginal resistance to inophyllums but were resistant to (+)-(5S)-4,5,6,7-tetrahydro-9-chloro-5-methyl-6- (3-methyl-2-butenyl)-imidazo[4,5,1-j,k][1,4]benzodiazepin-2-(1H)-t hione (TIBO R82913). A mutant enzyme in which tyrosine 188 was changed to leucine was cross-resistant to both inophyllum B and TIBO R82913, as was HIV type 2 reverse transcriptase. These studies suggest that inophyllum B and TIBO R82913 bind to distinct but overlapping sites. Inhibition of avian myeloblastosis virus reverse transcriptase and Moloney murine leukemia virus reverse transcriptase by inophyllum B was detectible, suggesting that these inhibitors may be more promiscuous than other previously described non-nucleoside inhibitors. Inophyllums were active against HIV type 1 in cell culture with IC50 values of approximately 1.5 microM. These studies imply that the inophyllums have a novel mechanism of interaction with reverse transcriptase and as such could conceivably play a role in combination therapy.
...
PMID:Kinetic and mutational analysis of human immunodeficiency virus type 1 reverse transcriptase inhibition by inophyllums, a novel class of non-nucleoside inhibitors. 750

Residual leukemic cells are detectable at frequencies as low as 1 in 10(6) normal cells in patients with Philadelphia chromosome/BCR-ABL-positive leukemias in complete remission (CR) using reverse-transcriptase polymerase chain reaction (RT-PCR) with specific nested primers. The level of minimal residual disease (MRD) in the bone marrow (BM) and the peripheral blood (PB) may favor one of the two as the source for an autologous graft. In order to quantify MRD with RT-PCR we analyzed patients ficolled cells after limiting logarithmic dilutions in normal ficolled buffy-coat cells. In six patients with BCR-ABL-pos ALL who were in CR by conventional criteria (5 in CR1 and 1 in CR2), we studied a total of nine paired BM and PB samples prior to scheduled ABMT. A positive RT-PCR signals was detectable in all samples up to dilutions ranging from 1:10(1) to 1:10(3) in PB, and at higher titers ranging from 1:10(3) to 1:10(5) in the BM. The BM titers exceeded the corresponding PB titers in all nine sample pairs by at least 1 log. The mean difference was 1.55 log (geometric mean, n = 9) and is statistically significant (p < 0.03). We conclude that residual leukemia in BCR-ABL-positive ALL preferentially locates in the BM compartment, and we assume that PB may yield autologous grafts with significantly less leukemic contamination.
...
PMID:In patients with BCR-ABL-positive ALL in CR peripheral blood contains less residual disease than bone marrow: implications for autologous BMT. 751 36

Fifty-seven Thai herbs and spices were examined for their retroviral reverse transcriptase inhibitory activity. All herbs and spices were extracted with hot-water and methanol. Reverse transcriptase inhibitory activity of the extracts was determined by using Moloney Murine Leukemia Virus reverse transcriptase (M-MuLV-RT) reacted with 3H-dTTP and radioactivity measured with a scintillation counter. Eighty-one per cent (46/57) of hot-water extracts and 54% (31/57) of methanol extracts showed inhibitory activities. At a concentration of 125 micrograms/ml, 13% (6/46) of hot-water extracts, namely Eugenia caryophyllus Bullock et Harrison, Phyllanthus urinaria Linn., Terminalia belerica Roxb., Nelumbo nucifera Gaertn., Psidium guajava Linn. and Lawsonia inermis Linn., had a relative inhibitory ratio (IR) over 50%. They showed ratios of 100%, 91%, 75%, 74%, 61% and 60%, respectively. For methanol extracts, only 10% (3/31) had IR values over 50%. They were T. belerica, E. caryophyllus and N. nucifera which exhibited IR values of 83%, 54% and 54%, respectively.
...
PMID:Retroviral reverse transcriptase inhibitory activity in Thai herbs and spices: screening with Moloney murine leukemia viral enzyme. 752 65

The growth of a panel of 22 different human tumor, leukemia, and lymphoma cell lines was examined in a human tumor cloning assay in agar or methylcellulose and a tritiated thymidine uptake assay. The cultures were performed in the absence or presence of increasing concentrations (0.5-500 ng/ml) of nerve growth factor (NGF). The growth of 17 of the 22 cell lines was not significantly and reproducibly affected by NGF. There was minor (1.2-fold) but reproducible stimulation of clonal growth in one glioblastoma cell line (86-HG-39) by NGF, but in this cell line NGF induced no growth modulation in a tritiated thymidine uptake assay. However, clonal growth of another glioblastoma cell line (87-HG-31) and all three lung cancer cell lines tested (HTB 119, HTB 120, CCL 185) could be stimulated up to 3-fold by NGF with a dose-response relationship for the growth factor. Growth stimulation by NGF could be completely reversed by neutralizing anti-NGF antibody and by the tyrosine kinase inhibitor genistein. Evaluation of secondary plating efficiency revealed the stimulation of colony formation as representing self-renewal and not terminal differentiation. Reverse transcriptase-PCR experiments in the five responding cell lines showed expression of both low-affinity NGF receptor (glycoprotein 75) and c-trk transcripts on the mRNA level. Of the five responding cell lines, only 86-HG-39, the cell line with the lowest responsiveness, revealed low-affinity NGF receptor on the protein level; the other four cell lines with high responsiveness, including the three lung cancer cell lines, expressed no low-affinity NGF receptor as shown by fluorescence-activated cell sorter analysis and immunoprecipitation using the ME 20.4 antibody. Immunoprecipitation using anti-trk antibodies was negative in all five responding cell lines. However, binding studies with iodinated NGF showed only low-affinity binding on the 86-HG-39 cell line and only high-affinity binding on the high-responder cell lines CCL 185 and 87-HG-31. In summary, our data suggest that NGF can be operative in stimulation of clonal growth of malignant tumor cells. High-affinity but not low-affinity binding sites mediate signal transduction for clonal growth and signaling involves tyrosine kinase activity.
...
PMID:Nerve growth factor stimulates clonal growth of human lung cancer cell lines and a human glioblastoma cell line expressing high-affinity nerve growth factor binding sites involving tyrosine kinase signaling. 753 48

We have used the vaccinia virus-T7 RNA polymerase-based expression system for studies on the activity of proteases from various retroviruses on homologous and heterologous Gag polyproteins in eukaryotic cells. Proteases from human immunodeficiency virus (HIV) types 1 and 2, equine infectious anaemia virus, human T cell leukaemia virus type 1 and human spumavirus were produced and were shown to cleave their cognate Gag substrates produced in trans. Analysis of cross reactivity revealed that lentivirus proteases cleaved only lentivirus Gag proteins and oncovirus proteases acted primarily on oncovirus Gag proteins. The HIV-2 protease cleaved the HIV-1 Gag precursor almost as efficiently as HIV-1 protease. Expression of the 5' end of the human spumavirus pol gene revealed that it encodes a functional protease that acts specifically on the human spumavirus Gag polyprotein. This assay will allow further investigation on the activity and specificity of retrovirus proteases in eukaryotic cells.
...
PMID:Analysis of cross reactivity of retrovirus proteases using a vaccinia virus-T7 RNA polymerase-based expression system. 756 54


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---