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

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new RTE-like, non-long terminal repeat retrotransposon, termed SjR2, from the human blood fluke, Schistosoma japonicum, is described. SjR2 is approximately 3.9 kb in length and is constituted of a single open reading frame encoding a polyprotein with apurinic/apyrimidinic endonuclease and reverse transcriptase domains. The open reading frame is bounded by 5'- and 3'-terminal untranslated regions and, at its 3'-terminus, SjR2 bears a short (TGAC)(3) repeat. Phylogenetic analyses based on conserved domains of reverse transcriptase or endonuclease revealed that SjR2 belonged to the RTE clade of non-long terminal repeat retrotransposons. Further, SjR2 was homologous, but probably not orthologous, to SR2 from the African blood fluke, Schistosoma mansoni; this RTE-like family of non-long terminal repeat retrotransposons appears to have arisen before the divergence of the extant schistosome species. Hybridisation analyses indicated that approximately 10,000 copies of SjR2 were dispersed throughout the S. japonicum chromosomes, accounting for up to 14% of the nuclear genome. Messenger RNAs encoding the reverse transcriptase and endonuclease domains of SjR2 were detected in several developmental stages of the schistosome, indicating that the retrotransposon was actively replicating within the genome of the parasite. Exploration of the coding and non-coding regions of SjR2 revealed two notable characteristics. First, the recombinant reverse transcriptase domain of SjR2 expressed in insect cells primed reverse transcription of SjR2 mRNA in vitro. By contrast, recombinant SjR2-endonuclease did not appear to cleave schistosome or plasmid DNA. Second, the 5'-untranslated region of SjR2 was >80% identical to the 3'-untranslated region of a schistosome heat shock protein-70 gene (hsp-70) in the antisense orientation, indicating that SjR2-like elements were probably inserted into the non-coding regions of ancestral S. japonicum HSP-70, probably after the species diverged from S. mansoni.
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PMID:Reverse transcriptase activity and untranslated region sharing of a new RTE-like, non-long terminal repeat retrotransposon from the human blood fluke, Schistosoma japonicum. 1211 99

Adenylosuccinate lyase is an enzyme used in parasite nucleotide salvage pathways that cleaves adenylosuccinate into adenosine 5'-monophosphate and fumarate. A cDNA encoding adenylosuccinate lyase from the trematode parasite Schistosoma mansoni has been cloned for analysis. Sequencing of the cDNA revealed an open reading frame of 1454 nucleotides that codes for a protein with a predicted mass of about 54.5 kDa. Comparative analysis of the predicted protein sequence shows that S. mansoni adenylosuccinate lyase has a lot of similarity with human adenylosuccinate lyase. Genomic analysis using S. mansoni adenylosuccinate lyase-containing bacterial artificial chromosome (BAC) clones revealed a gene of approximately 19.4 kb consisting of eight exons and seven introns. Intron 6 was found to contain a novel 2.9 kb long terminal repeat retrotransposon with direct terminal repeats of 500 nucleotides. Fluorescence in situ hybridisation mapping localised S. mansoni adenylosuccinate lyase to the Z and W chromosomes. Analysis of S. mansoni adenylosuccinate lyase mRNA expression levels using real time reverse transcriptase (RT)-PCR showed that S. mansoni adenylosuccinate lyase is expressed at higher levels in the female worms than in the male worms and is expressed at different levels than other purine nucleotide salvage enzymes. Male homogenate showed a specific activity of 10.3 units/mg protein while the female showed a specific activity of 24.2 units/mg protein. These data indicate that S. mansoni adenylosuccinate lyase is an important parasite enzyme and should be examined as a potential chemotherapeutic target.
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PMID:Adenylosuccinate lyase of Schistosoma mansoni: gene structure, mRNA expression, and analysis of the predicted peptide structure of a potential chemotherapeutic target. 1239 14

In this paper, we used the genetic manipulation technique known as RNA-interference to suppress the expression of a target, cathepsin B, gene in the platyhelminth parasite, Schistosoma mansoni. Parasites were cultured for 6 days in the presence of double stranded RNA derived from the cathepsin B cDNA sequence or from two control sequences. Relative to the controls, the cathepsin B double stranded RNA-treated group exhibited lower levels of cathepsin B as determined by immuno-staining and by enzyme activity measurements. Additionally, using the reverse transcriptase-PCR, suppression was seen in the inability to detect cathepsin B cDNA, using RNA obtained from those parasites. This ability to manipulate gene expression represents a powerful new tool for investigating gene function in these debilitating human parasites.
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PMID:Suppression of cathepsin B expression in Schistosoma mansoni by RNA interference. 1270 30

The genome of Schistosoma mansoni contains a proviral form of a retrovirus-like long terminal repeat (LTR) retrotransposon, designated BOUDICCA: Sequence and structural characterization of the new mobile genetic element, which was found in bacterial artificial chromosomes prepared from S. mansoni genomic DNA, revealed the presence of three putative open reading frames (ORFs) bounded by direct LTRs of 328 bp in length. ORF1 encoded a retrovirus-like major homology region and a Cys/His box motif, also present in Gag polyproteins of related retrotransposons and retroviruses. ORF2 encoded enzymatic domains and motifs characteristic of a retrovirus-like polyprotein, including aspartic protease, reverse transcriptase, RNase H, and integrase, in that order, a domain order similar to that of the gypsy/Ty3 retrotransposons. An additional ORF at the 3' end of the retrotransposon may encode an envelope protein. Phylogenetic comparison based on the reverse transcriptase domain of ORF2 confirmed that Boudicca was a gypsy-like retrotransposon and showed that it was most closely related to CsRn1 from the Oriental liver fluke Clonorchis sinensis and to kabuki from Bombyx mori. Bioinformatics approaches together with Southern hybridization analysis of genomic DNA of S. mansoni and the screening of a bacterial artificial chromosome library representing approximately 8-fold coverage of the S. mansoni genome revealed that numerous copies of Boudicca were interspersed throughout the schistosome genome. By reverse transcription-PCR, mRNA transcripts were detected in the sporocyst, cercaria, and adult developmental stages of S. mansoni, indicating that Boudicca is actively transcribed in this trematode.
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PMID:Boudicca, a retrovirus-like long terminal repeat retrotransposon from the genome of the human blood fluke Schistosoma mansoni. 1274 72

Inspection of the nucleotide sequence of bacterial artificial chromosome number 49_J_14 [Le Paslier, M.C., Pierce, R.J., Merlin, F., Hirai, H., Wu, W., Williams, D.L., Johnston, D., LoVerde, P.T., Le Paslier, D., 2000. Construction and characterization of a Schistosoma mansoni bacterial artificial chromosome library. Genomics 65, 87-94] from chromosome 1 of the genome of Schistosoma mansoni (GenBank ) revealed the likely presence of a proviral form of a novel schistosome retrotransposon. The novel element, which we named the fugitive, belonged to the mag-like family of the gypsy-Ty3 clade of long terminal repeat retrotransposons. It was closely related to the mag-like retrotransposon Gulliver from Schistosoma japonicum, but was dissimilar to several other long terminal repeat retrotransposons known from S. mansoni including Boudicca, Saci-1, Saci-2 and Saci-3. The full length fugitive element was 4811 bp constituted of a single read-through open reading frame of 4134 bp flanked at both ends by identical long terminal repeat sequences of 273 bp. The open reading frame encoded retroviral-like gag, with a distinctive double Cys-His motif, and pol polyprotein, with a pol domain order of protease, reverse transcriptase, RNaseH and integrase. Examination of schistosome transcriptome sequences in the public domain revealed that the fugitive was transcribed in at least six developmental stages of S. mansoni, while bioinformatics approaches and Southern hybridisation analysis indicated that as many as 2000 copies of the fugitive were interspersed throughout the schistosome genome.
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PMID:The fugitive LTR retrotransposon from the genome of the human blood fluke, Schistosoma mansoni. 1554 97

Suppression subtractive hybridization (SSH) was used to construct a complementary DNA library enriched for transcripts more abundantly expressed in the resistant BS90 strain of Biomphalaria glabrata at 12 hr postinfection with Schistosoma mansoni as compared with the susceptible M-line strain under the same circumstances. One hundred and twelve clones of the library were sequenced, yielding 88 unique SSH-expressed sequence tags (ESTs). Differential expression screening indicated that 22 of the 88 unique transcripts were strong candidates for differential expression in the BS90 strain relative to the M-line strain. Analysis of a subset of 4 transcripts using quantitative reverse transcriptase-polymerase chain reaction (qPCR) substantially supports the patterns obtained using the differential expression screen. Furthermore, the qPCR results revealed that gene upregulation in resistant snails, downregulation in susceptible snails, and differences in constitutive gene expression can all account for differential expression during the defense responses of resistant and susceptible snails. The majority (71.6%) of the SSH-ESTs recovered consisted of novel sequences not identified by sequence similarity to known genes. This work complements previous efforts to elucidate the genetic components underlying a successful response to S. mansoni by B. glabrata and identifies a series of transcripts deserving additional study in comparing susceptible and resistant snails.
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PMID:Identification of transcripts generated during the response of resistant Biomphalaria glabrata to Schistosoma mansoni infection using suppression subtractive hybridization. 1556 3

This work describes 18 new transcribed retrotransposons of the blood fluke Schistosoma mansoni. Among them, 9 were LTR, 8 non-LTR, and 1 Penelope-like element (PLE) retrotransposon. Sequences were generated by in silico reconstruction using S. mansoni ESTs and transcripts obtained by rapid amplification of cDNA ends, complemented in some cases by sequencing of genomic clones amplified by PCR. A novel element from the ancient R2/R4/CRE transposon group is described for the first time in S. mansoni. In addition, one non-LTR retrotransposon family displays long (40-450 bp) 3'-UTR with at least six different transcribed sequences among the copies, five LTR retrotransposons have abundantly transcribed incomplete copies lacking the sequence segment coding for the reverse transcriptase domain, and four non-LTR retrotransposons code for DNA-binding PHD domains that may give them a differential targeting. These results allow for a comprehensive description of the transcribed retrotransposon diversity of this complex human parasite.
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PMID:Identification of 18 new transcribed retrotransposons in Schistosoma mansoni. 1593 96

In most bilaterian organisms so far studied, Hox genes are organized in genomic clusters and determine development along the anteroposterior axis. It has been suggested that this clustering, together with spatial and temporal colinearity of gene expression, represents the ancestral condition. However, in organisms with derived modes of embryogenesis and lineage-dependent mechanisms for the determination of cell fate, temporal colinearity of expression can be lost and Hox cluster organization disrupted, as is the case for the ecdysozoans Drosophila melanogaster and Caenorhabditis elegans and the urochordates Ciona intestinalis and Oikopleura dioica. We sought to determine whether a lophotrochozoan, the platyhelminth parasite Schistosoma mansoni, possesses a conserved or disrupted Hox cluster. Using a polymerase chain reaction (PCR)-based strategy, we have cloned and characterized three novel S. mansoni genes encoding orthologues of Drosophila labial (SmHox1), deformed (SmHox4), and abdominal A (SmHox8), as well as the full-length coding sequence of the previously described Smox1, which we identify as an orthologue of fushi tarazu. Quantitative reverse transcriptase-PCR showed that the four genes were expressed at all life-cycle stages but that levels of expression were differentially regulated. Phylogenetic analysis and the conservation of "parapeptide" sequences C-terminal to the homeodomains of SmHox8 and Smox1 support the grouping of platyhelminths within the lophotrochozoan clade. However, Bacterial Artificial Chromosome (BAC) library screening followed by genome walking failed to reconstitute a cluster. The BAC clones containing Hox genes were sequenced, and in no case were other Hox genes found on the same clone. Moreover, the SmHox4 and SmHox8 genes contained single very large introns (>40 kbp) further indicating that the schistosome Hox cluster is highly extended. Localization of the Hox genes to chromosomes using fluorescence in situ hybridization showed that SmHox4 and SmHox8 are on the long arm of chromosome 4, whereas SmHox1 and Smox1 are on chromosome 3. In silico screening of the available genome sequences corroborated results of Southern blotting and BAC library screening that indicate that there are no paralogues of SmHox1, SmHox4, or SmHox8. The schistosome Hox cluster is therefore not duplicated, but is both dispersed and disintegrated in the genome.
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PMID:Evidence for a dispersed Hox gene cluster in the platyhelminth parasite Schistosoma mansoni. 1612 Aug 9

Members of the retrotransposable element (RTE) clade of non-long terminal repeat (LTR) retrotransposon are widely distributed among eukaryote taxa, with representatives known from Caenorhabditis elegans, mammals, mosquitoes, schistosomes, and other taxa. An RTE retrotransposon has not, however, been characterized in detail from a parasitic nematode. Here, we characterize two discrete copies of an RTE-like non-LTR retrotransposon from the genome of the dog hookworm, Ancylostoma caninum. The elements were named dingo-1 and dingo-2. The full-length dingo-1 and dingo-2 elements were 3421 and 3171bp in length, respectively. They exhibited 54% nucleotide sequence identity to one another across their entire length and 40%/58% amino-acid sequence identity/similarity across their open reading frames. dingo-1 and dingo-2 exhibited hallmark structures and sequences of non-LTR retrotransposons of the RTE family including a single open reading frame encoding apurinic-apyrimidinic endonuclease (EN) and reverse transcriptase (RT), in that order. Phylogenetic analyses targeting the RT and the EN domains both confirmed that dingo-1 and dingo-2 were members of the RTE clade and that they were closely related to RTE-1 from C. elegans, to BDDF from Bos taurus and to SR2 from Schistosoma mansoni. Dot blot hybridization indicated that as many as 100-1000 copies of dingo-1 reside within the genome of A. caninum, while detection by RT-PCR of transcripts encoding dingo-like elements suggested that dingo-1 and -2 may be retrotranspositionally active within the genome of A. caninum. The dingo elements are the first retrotransposons to be characterized from a hookworm genome.
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PMID:The dingo non-long terminal repeat retrotransposons from the genome of the hookworm, Ancylostoma caninum. 1644 14

Biomphalaria glabrata is an intermediate snail host for Schistosoma mansoni, a medically important schistosome. In order to identify transcripts involved in snail-schistosome interactions, subtractive cDNA libraries were prepared, using suppression subtractive hybridization (SSH) between a parasite-exposed schistosome-resistant and a susceptible strain of B. glabrata, and also between schistosome-exposed and unexposed snails from the resistant snail line. Separate libraries were made from both haemocytes and the haemopoietic organ. Subtraction was performed in both directions enriching for cDNAs differentially expressed between parasite-exposed resistant and susceptible samples and up or down-regulated in the resistant line after challenge. The resulting eight libraries were screened and eight genes, differentially expressed between the haemocytes of resistant and susceptible snail strains, were identified and confirmed with reverse transcriptase PCR, including two transcripts expected to be involved in the stress response mechanism for regulating the damaging oxidative burst pathways involved in cytotoxic killing of the parasite: the iron-storage and immunoregulatory molecule, ferritin, and HtrA2, a serine protease involved in the cellular stress response. Transcripts with elevated levels in the resistant strain, had the same expression patterns in the subtracted libraries and unsubtracted controls; higher levels in exposed resistant snails compared to susceptible ones and down-regulated in exposed compared with unexposed resistant snails. Differential expression of two of the transcripts with no known function from the susceptible strain, was independently confirmed in a repeat exposure experiment.
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PMID:Identification of genes involved in interactions between Biomphalaria glabrata and Schistosoma mansoni by suppression subtractive hybridization. 1708 33


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