Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An enzymatic mechanism involved in the activation of 3-hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole (N-hydroxy-Trp-P-2), a mutagenic intermediate of a tryptophan pyrolysate, was studied in vitro. In hepatic cytosol supplemented with adenosine triphosphate and L-proline, N-hydroxy-Trp-P-2 was converted to a form which reacts readily with DNA. The enzyme responsible for the activation was partially purified and identified as prolyl transfer RNA synthetase as judged by their cofactor requirements, inhibition by pyrophosphate or adenosine monophosphate, and copurification of their activities. The prolyl transfer RNA-dependent covalent binding of N-hydroxy-Trp-P-2 to DNA of hepatic cytosol was highest in rats, followed by mice, hamsters, rabbits, and guinea pigs in that order. The capacity for the binding of N-hydroxy-Trp-P-2 was largely consistent with their prolyl transfer RNA synthetase activity. With regard to the ultimate form of N-hydroxy-Trp-P-2 for the covalent binding, a possible formation of N,O-prolyl-3-amino-1-methyl-5H-pyrido[4,3-b]indole was proposed.
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PMID:Catalysis of the covalent binding of 3-hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole to DNA by a L-proline- and adenosine triphosphate-dependent enzyme in rat hepatic cytosol. 398 89

Reverse transcriptase-like sequences (RTs) with amino acid motifs characteristic of non-LTR retrotransposons have been isolated from several medically important phlebotomine sandfly species. These sequences were amplified using the polymerase chain reaction (PCR) with primers based on conserved amino acid motifs present in previously described insect RTs. A further set of RTs were amplified using primers based on the conserved regions identified in phlebotomine RTs. The average similarity of the phlebotomine RTs to the Drosophila I, F and R1Dm elements was 28-29% between the closest primers used. Phlebotomine RTs were 31-62% similar to each other, the most dissimilar sequences coming from the same species. Several amino acid residues were invariant in the ten phlebotomine RTs, including motif Q(F/Y)GF, conserved in other non-LTR retrotransposons, but not in retrovirus or LTR retrotransposon RTs. The remarkable conservation of this distinctive domain of non-LTR retrotransposon RTs suggests it has a vital and possibly unique role in the mode of reverse transcription of this class of transposon.
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PMID:Isolation of non-LTR retrotransposon reverse transcriptase-like sequences from phlebotomine sandflies. 752 83

This study was designed to clarify the important association between eosinophilia-myalgia syndrome (EMS) and the L-tryptophan contaminant, "Peak E." To determine the functional activation of eosinophils induced by Peak E, eosinophil cationic protein (ECP) release was examined. Peak E augumented the release of ECP from peripheral blood normodense eosinophils by degranulation. Proliferative analysis using the human eosinophilic leukemia cell line EoL-3 showed prominent cellular replication in the presence of Peak E. Moreover, Peak E upregulated interleukin 5 (IL-5) receptor levels on normodense eosinophils. Of particular interest, Peak E-stimulated human splenic T cells produced bioactive and immunoreactive IL-5. Marked induction of IL-5 mRNA in Peak E-stimulated T cells was also shown by reverse-transcriptase polymerase chain reaction (RT-PCR). In contrast, L-tryptophan without the contaminant showed none of these effects. Thus, these data suggest that Peak E might be involved in the pathogenesis of EMS through bimodal mechanism including IL-5 generation by T cells and potentiation of eosinophil functional activation.
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PMID:1,1'-Ethylidenebis(tryptophan) (Peak E) induces functional activation of human eosinophils and interleukin 5 production from T lymphocytes: association of eosinophilia-myalgia syndrome with a L-tryptophan contaminant. 813 37

A host cell-derived tRNA3Lys molecule is utilized by human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) to prime DNA synthesis from the viral RNA genome. We performed fluorescence titration experiments to characterize the interaction between RT and its natural primer, tRNA3Lys, and to address RT's putative role in the required and specific packaging of tRNA3Lys into the budding virus. Titration of RT with tRNA3Lys resulted in a 30% maximal quenching of RT tryptophan fluorescence, from which a dissociation constant (Kd) of 57.6 +/- 7.5 nM was derived. Titration of RT with Escherichia coli tRNA2Glu, E. coli tRNA2Tyr, E. coli tRNALys, yeast tRNAPhe, or in vitro-synthesized human tRNA3Lys (no base modifications) resulted in similar fluorescence changes and Kd values as obtained for the natural tRNA3Lys. The specific interaction between RT and tRNA3Lys during viral assembly suggested by previous in vivo studies is therefore not present in the fully processed, in vitro form of RT. Other factors during viral assembly must therefore cooperate in the packaging of tRNA3Lys. The nonspecific and ionic strength dependent RT-tRNA interaction detected in the present studies suggests that the overall shape and charges of tRNA constitute recognition features for RT binding. The fluorescence of the wyebutine base contained on the anticodon loop of yeast tRNAPhe was found to increase upon RT binding, supporting speculation that RT interacts with the anticodon loop of tRNA. The individual tRNAs also displaced a fluorescent DNA primer/template (p/t) substrate from RT, indicating overlapping tRNA and p/t binding sites. Cubic fit evaluation of the displacement titrations allowed further assessment of the affinities of the two competing ligands. The presence of both overlapping and separate p/t and tRNA binding regions on RT was tested by examination of the affinity of a possible RT bisubstrate type inhibitor, containing motifs proposed to be essential for both tRNA and p/t binding. Reverse transcriptase was found to bind to the mutant tRNA 10-fold more tightly than to the unaltered tRNA (Kd = 4.5 +/- 1.0 and 44.6 +/- 6.6 nM, respectively). Further analyses revealed that the tighter affinity is probably due to a preferred p/t binding mode and not to one expected if separate tRNA and p/t binding regions are accessed simultaneously by the same molecule.
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PMID:Evaluation of human immunodeficiency virus type 1 reverse transcriptase primer tRNA binding by fluorescence spectroscopy: specificity and comparison to primer/template binding. 860 12

The possible involvement of the human T lymphotropic viruses type I and II (HTLV-I and -II) in lymphoproliferative disorders of mature T cells other than adult T cell leukemia/lymphoma (ATLL) has been controversial. Most studies have focused primarily on the cutaneous T cell lymphomas. However, skin involvement is a frequent feature of T prolymphocytic leukemia (T-PLL) and antibodies against HTLV-I and -II have been reported in individuals with large granular lymphocytic (LGL) leukemia. We examined 36 patients with T-PLL and 28 with LGL leukemia for evidence of HTLV-I and -II. Polymerase chain reaction (PCR) was performed on DNA from fresh peripheral blood mononuclear cells (PBMCs) and PBMCs after short-term culture (STC) using primers against all parts of the HTLV-I genome (LTR, gag, env, pol, tax/rex) and against HTLV-II pol and gag. Reverse transcriptase (RT) activity was measured on supernatants from STCs using a sensitive PCR-based technique. No HTLV-I or -II sequences were found by PCR nor RT activity detected in the 64 cases. Our findings do not provide evidence of HTLV-I or -II infection in T-PLL and LGL leukemia patients from an HTLV-I nonendemic area. Previous positive reports on these disorders may represent technical artefacts, detection of endogenous HTLV-like sequences or reflect patients from endemic areas and a variable etiology of T cell diseases.
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PMID:The human T-cell lymphotropic viruses types I/II are not involved in T prolymphocytic leukemia and large granular lymphocytic leukemia. 926 85

Association between mycosis fungoides (MF), its leukaemic variant Sezary syndrome (SS) and the human T-cell lymphotropic virus type-I (HTLV-I) has been controversial, with the reported incidence of infection varying between 0% and nearly 100%. We studied 127 patients (85 MF, 28 SS, five Sezary cell leukaemia, four lymphomatoid papulosis, and five unspecified cutaneous T-cell lymphomas (CTCL)) originating from Europe (France, Spain, U.K., Portugal) or from U.S.A. (California) for the presence of HTLV-I infection markers. HTLV-I and -II serology were performed on 78 patients using standard immunological methods. Reverse transcriptase (RT) assay was also performed in 26 cases using an RT-PCR-based method of high sensitivity. Molecular analyses were performed on 215 DNA samples (121 from fresh PBMCs, 26 from PBMCs after short-term culture and 68 from skin lesions) by PCR amplification using HTLV-I and -II gag, pol, env, pX and LTR specific primers. Immunological tests were negative except for two sera which were indeterminate. PCR with all HTLV-I and -II primer pairs showed negative results in all 215 samples investigated. No RT activity was detected in short-term PBMC cultures of any of the 26 cases studied. The results of this large study from five different countries clearly indicate that MF and SS are not associated with HTLV-I infection.
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PMID:Mycosis fungoides and Sezary syndrome are not associated with HTLV-I infection: an international study. 1055 37

We used a new approach called panhandle polymerase chain reaction (PCR) to clone an MLL genomic translocation breakpoint in a case of acute lymphoblastic leukemia of infancy in which karyotype analysis was technically unsuccessful and did not show the translocation partner. Panhandle PCR amplified known MLL sequence 5' of the breakpoint and 3' sequence from the unknown partner gene from a DNA template with an intrastrand loop schematically shaped like a pan with a handle. The 7-kb panhandle PCR product contained the translocation breakpoint in MLL intron 8. The partner DNA included unique nonrepetitive sequences, Alu and mammalian apparent LTR-retrotransposon (MaLR) repetitive sequences, and a region of homology to expressed sequence tags. MaLR sequences have not been found before near leukemia-associated translocation breakpoints. The nonrepetitive sequences were not homologous to known partner genes of MLL. Screening of somatic cell hybrid and radiation hybrid lines by PCR and fluorescence in situ hybridization analysis of normal metaphase chromosomes mapped the partner DNA to chromosome band 4q21. Reverse transcriptase-PCR identified an MLL-AF-4 chimeric mRNA, indicating that panhandle PCR identified a fusion of MLL with a previously uncharacterized AF-4 intronic sequence. Panhandle PCR facilitates cloning translocation breakpoints and identifying unknown partner genes.
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PMID:Panhandle polymerase chain reaction amplifies MLL genomic translocation breakpoint involving unknown partner gene. 938 82

The BARE-1 copia-like retrotransposon constitutes nearly 7% of the barley (Hordeum vulgare L.) genome as a family of more than 2 x 10(4) mostly full-length copies dispersed on all chromosomes. BARE-1 elements are transcribed in barley tissues from promoters within the LTR (long terminal repeat). The predicted, translated polyprotein contains conserved domains for GAG, aspartic proteinase, integrase, reverse-transcriptase, and RNase H. Here, we have used inverse PCR with LTR-based primers to establish the consensus sequences for the terminal region of the LTR, the external dinucleotides of the cDNA integration intermediate, and the minus- and plus-strand priming sites. These key functional entities are well-conserved in the BARE-1 family, including wheat Wis2, but differ from those of other plant retrotransposons. The target site duplication was established as 5 bp. Of the 13 integration sites identified here, 8 were other BARE-1 elements and 1 another retrotransposon; 59% of the total 17 identified BARE-1 insertion sites are retrotransposons. This nested insertion pattern may represent a basic feature of plant retrotransposons.
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PMID:BARE-1 insertion site preferences and evolutionary conservation of RNA and cDNA processing sites. 944 Feb 75

RTE-1 is a non-long-terminal-repeat (non-LTR) retrotransposable element first found in the Caenorhabditis elegans genome. It encodes a 1,024-amino-acid open reading frame (ORF) containing both apurinic-apyrimidic endonuclease and reverse-transcriptase domains. A possible first ORF of only 43 amino acids overlaps with the larger ORF and may be the site of translation initiation. Database searches and phylogenetic analysis indicate that representatives of the RTE clade of non-LTR retrotransposons are found in the bovine and sheep genomes of mammals and in the silkmoth and mosquito genomes of insects. In addition, the previously identified SINEs, Art2 and Pst, from ruminate and viper genomes are shown to be truncated RTE-like retrotransposable elements. RTE-derived SINE elements are also found in mollusc and flatworm genomes. Members of the RTE clade are characterized by unusually short 3' untranslated regions that are predominantly composed of AT-rich trimer, tetramer, and/or pentamer repeats. This study establishes RTE as a very widespread clade of non-LTR retrotransposons. RTE represents the third distinct class of non-LTR retrotransposons in the vertebrate lineage (after Line 1 elements in mammals and CR1 elements in birds and reptiles).
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PMID:The RTE class of non-LTR retrotransposons is widely distributed in animals and is the origin of many SINEs. 972 77

RNA-dependent RNA polymerase (RdRp) activity has been detected in mitochondria from an isolate of Ophiostoma novo-ulmi infected with O. novo-ulmi mitovirus 6 (OnuMV6). The reaction products corresponded to the double-stranded and single-stranded forms of OnuMV6 RNA. Western blot analysis using antibodies raised against a conserved RdRp region has detected a protein of ca. 80 kDa in OnuMV6-infected mitochondria, close to the predicted size of the OnuMV6 RdRp. No RdRp activity or protein was detected in mitochondria from an uninfected O. novo-ulmi isolate. This is the first detection of a virus RdRp in fungal mitochondria and the results are consistent with the use of UGA tryptophan codons in its synthesis.
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PMID:Detection of an RNA-dependent RNA polymerase in mitochondria from a mitovirus-infected isolate of the Dutch Elm disease fungus, Ophiostoma novo-ulmi. 1070 32


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