Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several newly discovered potent and selective non-nucleoside inhibitors of human immunodeficiency virus-1 reverse transcriptase (RT) are undergoing evaluation in clinical trials. We studied the potential for development of viral resistance to one of the prototype compounds, BI-RG-587, a dipyridodiazepinone derivative. Human immunodeficiency virus-1 resistant to BI-RG-587 emerged after only one cycle of in vitro infection in the presence of the drug. Resistant virus was cross-resistant to the non-nucleoside tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-thione derivative R82150 but remained susceptible to 2',3'-dideoxynucleosides and phosphonoformate. Both native (virion-associated) and recombinant RT derived from resistant virus were insensitive to BI-RG-587 and R82150. Nucleotide sequence analysis of multiple drug-resistant and -sensitive recombinant RT clones identified a single predicted amino acid change common to all resistant clones (tyrosine-181----cysteine). These studies suggest that the viral resistance to non-nucleoside RT inhibitors may develop in vivo. This possibility should be carefully monitored in clinical trials of these compounds.
Mol Pharmacol 1992 Mar
PMID:In vitro selection and molecular characterization of human immunodeficiency virus-1 resistant to non-nucleoside inhibitors of reverse transcriptase. 137 83

The use of splice donor site consensus sequences as primers in cDNA synthesis (to make a cDNA library from heterogeneous RNA or unprocessed transcript--an hn-cDNA library) and the screening of such an hn-cDNA library with human repeat DNA probe in order to isolate human genes from somatic cell hybrids have been demonstrated. Here, we optimize and evaluate the efficiency and limitations of the approach. Computer analysis of genomic sequences of 22 randomly selected human genes indicated that hexamers CTTACC, CTCACC, and CCTACC were most efficient at beginning first-strand cDNA synthesis at donor splice sites of hnRNA and suggested that the procedure is efficient for priming cDNA synthesis of at least one exon from most every gene. Primer extension experiments established conditions in which the primers would initiate synthesis of cDNA starting from a perfectly matched position on the RNA template at more than 60-fold higher yield than any other product. By isolation of a clone containing exon III of the human DNA repair gene ERCC1, we indicate that the approach is capable of cloning exons from weakly expressed genes. Sequencing of clones revealed a structure of hn-cDNA clones consistent with the expectations of the cloning strategy and indicated the potential of the clones in detecting polymorphisms. Finally, we demonstrate that the expression of these hn-cDNA sequences in cells can be detected efficiently at the hnRNA level by reverse transcriptase-polymerase chain reaction (RT/PCR).
Somat Cell Mol Genet 1992 Jan
PMID:Efficiency and limitations of the hn-cDNA library approach for the isolation of human transcribed genes from hybrid cells. 137 33

Strains carrying a marked Ty element (TyUra) in the LYS2 locus were transformed with plasmids bearing a differently marked Ty1 element (Ty1Neo) under the control of the GAL promoter. When these strains were grown in glucose, a low level of gene conversion events involving TyUra was detected. Upon growth on galactose an increase in the rate of gene conversion was seen. This homologous recombination is not the consequence of increased levels of transposition. When an intron-containing fragment was inserted into Ty1Neo, some of the convertants had the intron removed, implying an RNA intermediate. Mutations that affect reverse transcriptase or reverse transcription of Ty1Neo greatly reduce the induction of recombination in galactose. Thus, Ty cDNA is involved in homologous gene conversion with chromosomal copies of Ty elements. Our results have implications about the way families of repeated sequences retain homogeneity throughout evolution.
Mol Cell Biol 1992 Apr
PMID:Involvement of cDNA in homologous recombination between Ty elements in Saccharomyces cerevisiae. 137 87

Some natural isolates of Escherichia coli have been shown to produce a unique branched RNA-linked single-stranded DNA called msDNA. These bacteria contain a retro-element called retron consisting of the msr-msd region and the gene for reverse transcriptase (RT). All three E. coli retrons characterized to date have been shown to be integrated into a prophage or to be associated with phage-related genes. In this report, we identified a new msDNA from an E. coli wild strain. Using the msDNA as a probe, the retron for the msDNA was cloned and its DNA sequence was determined. The retron was found to consist of a 1.3kb DNA fragment, making it the smallest retron isolated to date. The msDNA produced from the retron consists of a 107 base single-stranded DNA, which is considered to be branched out from the 18th G residue of a 75-base RNA molecule by a 2',5'-phosphodiester linkage. Thus, the msDNA and the retron were designated msDNA-Ec107 and retron-Ec107, respectively. Most significantly, retron-Ec107 was inserted into the E. coli genome by replacing a 34bp intergenic sequence between the pyrE and ttk genes located at 82 min on the E. coli chromosome. Interestingly, the retron contains palindromic structures at both ends and the E. coli 34bp intergenic sequence also contains a 10bp inverted repeat structure. These palindromic structures might have played a role in the integration of retron-Ec107 into the E. coli genome.
Mol Microbiol 1992 Feb
PMID:Retron-Ec107 is inserted into the Escherichia coli genome by replacing a palindromic 34bp intergenic sequence. 137 75

In the preceding paper, we showed that a new 1.3 kb retron (retron-Ec107) in Escherichia coli is responsible for the biosynthesis of a branched-RNA-linked multicopy single-stranded DNA (msDNA-Ec107). Here, we show that this retron occurs in strains from different branches, A, B1, and D of a well-defined phylogenetic tree of a collection of wild E. coli. Sequence comparisons of the retrons from these three branches were carried out. Sequence homology was well conserved among the strains within the same branch and the retron sequence from branch A was exactly the same with that from branch D, while there were 18 base substitutions between the retrons from branch B1 and A or D, resulting in seven amino acid substitutions in reverse transcriptase. No substitutions were found in the msDNA- and msdRNA-coding regions, and there was no difference in the ability of msDNA production between them. These results suggest that the retron has probably been integrated into at least one of the three branches at an early stage of evolution and subsequently transferred to the other two branches, and also that the msDNA-producing system has been conserved during evolution with some mutations in the retron.
Mol Microbiol 1992 Feb
PMID:Sequence diversity of the 1.3 kb retron (retron-Ec107) among three distinct phylogenetic groups of Escherichia coli. 137 76

Recently, several classes of compounds have been shown to be potent, selective, and specific inhibitors of human immunodeficiency virus type 1 replication in vitro. These include the tetrahydroimidazo[4,5,1-jk][1,4]-benzodiazepin-2(1H)-one and -thione (TIBO) and the 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) derivatives. Both the TIBO and HEPT derivatives specifically inhibit human immunodeficiency virus type 1 reverse transcriptase (RT). From a comparative study of the characteristics of RT inhibition by TIBO and HEPT, and from the competition between TIBO and HEPT for RT inhibition, we infer that both classes of compounds, although structurally unrelated, are targeted at the same site of the enzyme. Detailed functional and kinetic analyses indicate that this target site is functionally and possibly also spatially related to the substrate binding site.
Mol Pharmacol 1992 May
PMID:Common features in the interaction of tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione and 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine derivatives with the human immunodeficiency virus type 1 reverse transcriptase. 137 20

Three families of retrotransposons of rice (Tos1, Tos2, and Tos3) were isolated by using a method based on the sequence conservation of the primer binding site for reverse transcription. This method should be generally applicable for cloning retrotransposon of other plants. One retrotransposon, Tos3-1, was studied in detail. Tos3-1 is 5.2 kb long, has structures common to retrotransposons, such as long terminal repeats (LTR), a primer binding site complementary to the initiator tRNA, a polypurine tract, and generates target sequence duplications flanking the inserted element. Southern blotting analysis showed that sequences homologous to Tos1, 2 and 3 are found in wild rice species as well as in cultivated rice species, but not in maize and tobacco. The copy number and genomic location of the families vary in different strains of one species of wild rice, suggesting that these elements may still be active. Retrotransposons were also screened for by amplification of the reverse transcriptase coding region using the polymerase chain reaction (PCR). At least two types of copia-like elements (Tos4 and Tos5) were found. The total copy number of retrotransposons in the rice genome was estimated to be about 1000. These results suggest that, as in Drosophila, retrotransposons are the major transposon class in rice.
Mol Gen Genet 1992 May
PMID:Retrotransposon families in rice. 137 4

Primer tRNA regions involved in the interactions between human immunodeficiency virus reverse transcriptase (HIV RT) and tRNA(Lys) were studied by digestion of primer with pancreatic ribonuclease in the presence or absence of HIV RT. The acceptor stem of tRNA(Lys) is not noticeably protected against nuclease action in the presence of HIV RT, while this enzyme clearly protects part of the anticodon and dihydrouridine loops of tRNA(Lys). The acceptor stem of primer tRNA was digested by RNase A only in the presence of the retroviral enzyme, suggesting a partial destabilization of this region by the HIV RT. Synthetic oligoribonucleotides, corresponding to the anticodon and the dihydrouridine loops, inhibited strongly reverse transcription, confirming the strong interaction of these tRNA regions with the enzyme.
J Mol Biol 1992 Jul 05
PMID:Preferential interaction of human immunodeficiency virus reverse transcriptase with two regions of primer tRNA(Lys) as evidenced by footprinting studies and inhibition with synthetic oligoribonucleotides. 137 51

A retrotransposon from the fungal tomato pathogen Cladosporium fulvum (syn. Fulvia fulva) has been isolated and characterised. It is 6968 bp in length and bounded by identical long terminal repeats of 427 bp; 5 bp target-site duplications were found. Putative first- and second-strand primer binding sites were identified. Three long open reading frames (ORFs) are predicted from the sequence. The first has homology to retroviral gag genes. The second includes sequences homologous to protease, reverse transcriptase, RNAse H and integrase, in that order. Sequence comparisons of the predicted ORFs indicate that this element is closely related to the gypsy class of LTR retrotransposons. Races of the pathogen exhibit polymorphisms in their complement of at least 25 copies of the sequence. Virus-like particles which co-sediment with reverse transcriptase activity were observed in homogenates of the fungus. This is the first report of an LTR retrotransposon in a filamentous fungus.
Mol Gen Genet 1992 Jun
PMID:CfT-I: an LTR-retrotransposon in Cladosporium fulvum, a fungal pathogen of tomato. 137 73

The genomic structure of the rat LINE (L1Rn) DNA element contains two overlapping open reading frames (ORFs) and apparently has a potential to code for a DNA/RNA-binding protein (in ORF1) and a reverse transcriptase (in ORF2). We have characterized a 1,630-bp L1Rn cDNA clone encompassing the overlapping ORFs and a 600-bp genomic fragment derived from a full-length L1Rn member and containing the beginning of ORF1. These DNAs were used to restore in part the ORF1-ORF2 organization of L1Rn after being cloned into the pSP65 vector under the control of SP6 polymerase promoter. To test whether L1Rn ORF1 and ORF2 are expressed as a fusion protein, a series of capped RNAs with progressive truncations containing one or both ORFs were prepared and translated in the rabbit reticulocyte lysate. Our analysis indicates that the expression of a putative reverse transcriptase-encoded L1Rn ORF2 in vitro is regulated by reinitiation or internal initiation of translation but not by ribosomal frameshifting.
Mol Cell Biol 1992 Sep
PMID:Translation of the rat LINE bicistronic RNAs in vitro involves ribosomal reinitiation instead of frameshifting. 138 Jun 49


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