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)

The PAT retroid transposable elements differ from other retroids in that they have a 'split direct repeat' structure, i.e., and internal 300bp sequence is found repeated, about one half at each element extremity. A very abundant transcript of about 900 nt, the start of which maps to the preferentially deleted portion of PAT elements, is detected on total Panagrellus redivius RNA bearing Northern blots. A potentially corresponding ORF encodes a protein of 265 residues having a carboxy terminal Cystein motif, believed to be exclusively characteristic of the GAG protein in retoid elements. A much fainter, 1800nt long transcript, is also detected on Northern blots and maps slightly downstream of the first ORF. The predicted protein sequence of this region bears motifs typical of reverse transcriptase and RNaseH, as found in the Pol genes of retroid elements. Peptide motif similarities are greatest with the DIRS-1 element derived from Dictyostelium discoideum. The possibility of using PAT elements as transposon tagging system for Caenorhabditis elegans is discussed.
 ...
PMID:Unusual features of the retroid element PAT from the nematode Panagrellus redivivus. 131 55

Only three retrotransposons of the DIRS1 group have previously been described: DIRS1 from the slime mold Dictyostelium discoideum, PAT from the nematode Panagrellus redivivus, and Prt1 from the zygomycetous fungus Phycomyces blakesleeanus. Analyses of the reverse transcriptase sequences encoded by these elements suggest that they are related to the long terminal repeat (LTR) retroelements, such as the Ty3/gypsy retrotransposons and the vertebrate retroviruses. The DIRS1-group elements, however, have several unusual structural features which distinguish them from typical LTR elements: (1) they lack the capacity to encode DDE-type integrases or aspartic proteases; (2) they have open reading frames (ORFs) of unknown function; (3) they integrate without creating duplications of their target sites; and (4) although they are bordered by terminal repeats, these sequences differ from typical LTRs in that they are either inverted repeats or "split" direct repeats. Because of the small number of DIRS1-like elements described, and the unusual structures of these elements, little is known about their evolution, distribution, and replication mechanisms. Here, we report the identification of several new DIRS1-like retrotransposons, including elements from nematodes, sea urchins, fish, and amphibia. We also present evidence for the existence of DIRS1-like sequences in the human genome. In addition, we show that the lack of DDE-type integrase genes from elements of the DIRS1 group is explained by the finding that the previously uncharacterized ORFs of these elements encode proteins related to the site-specific recombinase of bacteriophage lambda. The presence of lambda-recombinase-like genes in DIRS1 elements also accounts for the lack of target-site duplications for these elements and may be related to the unusual structures of their terminal repeats.
 ...
PMID:The DIRS1 group of retrotransposons. 1160 3

DIRS-1 is a retroelement from the slime mold Dictyostelium discoideum. Until recently only two related retrotransposons had been described: PAT from the nematode Panagrellus redivivus and Prt1 from the zygomycete fungus Phycomyces blakesleeanus. Analyses of the reverse transcriptase sequences encoded by these three elements suggested that they were closely related to each other and more distantly related to the Ty3/gypsy Long Terminal Repeat (LTR) retroelements. They have several unusual structural features that distinguish them from typical LTR elements. For instance, they each encode a tyrosine recombinase (YR), but not a DDE-type integrase or an aspartic protease. Although the DIRS-1-related elements are bordered by terminal repeats these differ from typical LTRs in a number of ways. In DIRS-1, for example, the terminal repeats are inverted (complementary), non-identical in sequence, and the outer edges of the terminal sequences are repeated (adjacent to each other) in the internal region. PAT has so-called "split" direct repeats in which the unrelated terminal sequences appear as direct repeats adjacent to each other in the internal region. The only repetition displayed by Prt1 is the presence of short inverted terminal repeats, but the sequenced copy of this element is believed to be a truncated version of an element with a structure resembling DIRS-1. The unusual structure of the terminal repeats of the DIRS1-like elements appears to be related to their replication via free circular intermediates. Site-specific recombination is believed to integrate the circle without creating duplications of the target sites. In recognition of these important distinctions it is proposed that the retrotransposons that encode tyrosine recombinases be called the tyrosine recombinase (or YR) retrotransposons. Recently a large number of additional YR retrotransposons have been described, including elements from fungi (zygomycetes and basidiomycetes), plants (green algae) and a wide range of animals including nematodes, insects, sea urchins, fish and amphibia, while remnants of elements related to DIRS-1 occur in the human genome. The complete set of YR retrotransposons can be divided into two major groups, the DIRS elements and the Ngaro elements, the two groups forming distinct clades on phylogenetic trees based on alignments of RT/RH and recombinase sequences, and also having some structural distinctions. A third group of transposable elements, which we call Cryptons, also carry tyrosine recombinases. These elements do not encode a reverse transcriptase and so are believed to be DNA transposons not retrotransposons. They have been detected in several pathogenic fungi, including the basidiomycete Cryptococcus neoformans, and the ascomycetes Coccidioides posadasii and Histoplasma capsulatum. Sequence comparisons suggest that the Crypton YRs are related to those of the YR retrotransposons. We suggest that the YR retrotransposons arose from the combination of a Crypton-like YR DNA transposon and the RT/RH encoding sequence of a retrotransposon.
 ...
PMID:DIRS-1 and the other tyrosine recombinase retrotransposons. 1609 11

The expression level of bar, which encodes phosphinothricin acetyltransferase (PAT), was correlated with the inviability of barley hybrids between 20 Golden Promise-derived transgenic lines (Ds-bar lines) and a specialized genetic marker stock, Oregon Wolfe Barley Dominant (OWBD). Each Ds-bar line was homozygous for a modified maize Ds element that encoded bar and that had been delivered via transposition to a unique location. All Ds-bar lines were viable and morphologically similar. Only four of the 20 hybrid populations were viable. The remaining populations died prior to producing seed. Phenotypic, enzyme-linked immunosorbent assay and quantitative reverse transcriptase-polymerase chain reaction analyses of these lines, and of lines from unrelated transformation events that also expressed bar, showed that viability was negatively correlated with bar expression. Analysis of crosses of a high-bar-expressing line with the OWB mapping population showed that the sensitivity of OWBD to PAT segregated as a single locus on chromosome 6HL. No sensitivity to PAT could be detected in several other lines and cultivars. OWBD has been shown to be genetically divergent from other germplasm groups within cultivated barley; therefore, the observed sensitivity may be peculiar to OWBD and thus would not impact generally on the utility of bar as a selectable marker or source of herbicide resistance in barley. Nevertheless, these results demonstrate the extent of allelic variability present in Hordeum vulgare, and suggest an additional variable for consideration when devising protocols for the transformation of Hordeum cultivars or landraces that are not known to be tolerant to PAT.
 ...
PMID:Viability and bar expression are negatively correlated in Oregon Wolfe Barley Dominant hybrids. 1735 97

Oleuropein, a bitter glucoside found in green olive leaves, and its metabolite hydroxytyrosol display powerful antioxidant activity both in vivo and in vitro. In this study, we hypothesized that the antioxidant activity of oleuropein could attenuate hepatic steatosis. To test this hypothesis, we established steatotic hepatocytes using HepG2 and FL83B cells treated with free fatty acids (FFAs) (oleate:palmitate, 2:1). To confirm hepatic steatosis, the intracellular lipid levels were quantitatively measured by Nile Red staining, and the sizes and distributions of lipid droplets were visualized by transmission electron microscopy. The expression of PAT family proteins as well as of adipose differentiation-related protein and tail interacting protein (TIP47) was evaluated by reverse transcriptase polymerase chain reaction and immunoblotting. To examine the cellular and molecular events associated with oleuropein, annexin V/propidium iodide staining and immunoblotting were performed. Oleuropein decreased the number and size of lipid droplets in FFA-treated cells and reduced intracellular triglyceride accumulation. However, it did not affect the expression of lipid droplets-associated PAT family proteins, including adipose differentiation-related protein and TIP47. In addition, oleuropein reduced FFA-induced extracellular signal-regulated kinase activation but had no effect on c-Jun N-terminal kinase or AKT activation. Given its protective effects against FFA-induced hepatocellular steatosis, oleuropein may be a lipid-lowering agent.
 ...
PMID:Oleuropein reduces free fatty acid-induced lipogenesis via lowered extracellular signal-regulated kinase activation in hepatocytes. 2314 75

Retrotransposons carrying tyrosine recombinases (YR) are widespread in eukaryotes. The first described tyrosine recombinase mobile element, DIRS1, is a retroelement from the slime mold Dictyostelium discoideum. The YR elements are bordered by terminal repeats related to their replication via free circular dsDNA intermediates. Site-specific recombination is believed to integrate the circle without creating duplications of the target sites. Recently a large number of YR retrotransposons have been described, including elements from fungi (mucorales and basidiomycetes), plants (green algae) and a wide range of animals including nematodes, insects, sea urchins, fish, amphibia and reptiles. YR retrotransposons can be divided into three major groups: the DIRS elements, PAT-like and the Ngaro elements. The three groups form distinct clades on phylogenetic trees based on alignments of reverse transcriptase/ribonuclease H (RT/RH) and YR sequences, and also having some structural distinctions. A group of eukaryote DNA transposons, cryptons, also carry tyrosine recombinases. These DNA transposons do not encode a reverse transcriptase. They have been detected in several pathogenic fungi and oomycetes. Sequence comparisons suggest that the crypton YRs are related to those of the YR retrotransposons. We suggest that the YR retrotransposons arose from the combination of a crypton-like YR DNA transposon and the RT/RH encoding sequence of a retrotransposon. This acquisition must have occurred at a very early point in the evolution of eukaryotes.
...
PMID:Tyrosine Recombinase Retrotransposons and Transposons. 2610 93