Small gene family encoding an eggshell (chorion) protein of the human parasite Schistosoma mansoni.

Bobek, Libuse A.; Rekosh, David; LoVerde, Philip T.

doi:10.1128/mcb.8.8.3008

Cited by 61 publications

(22 citation statements)

References 21 publications

(29 reference statements)

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“…On the basis of primer extensions and Northern analysis we conclude that a number of schistosome poly(A)+ transcripts carry the identical 36-nt SL sequence at their 5' termini. However, only a subset of S. mansoni poly(A)+ transcripts carry the SL sequence at their 5' termini, since primer extension analyses of transcripts encoding superoxide dismutase (21), egg shell protein (22), calciumbinding protein (23), and an antigen recognized by human sera from infected patients (13) failed to reveal the SL.…”

Section: Resultsmentioning

confidence: 99%

A spliced leader is present on a subset of mRNAs from the human parasite Schistosoma mansoni.

Rajkovic

Davis

Simonsen

et al. 1990

Proc. Natl. Acad. Sci. U.S.A.

128

118

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We present evidence that a subset of mRNAs in the human parasitic trematode Schistosoma mansoni contain an identical 36-nucleotide spliced leader (SL) sequence at their 5' termini. The SL is derived from a 90-nucleotide nonpolyadenylylated RNA (SL RNA), presumably by trans-splicing.Neither the SL nor the SL RNA share significat sequence identity with previously described trans-spliced leaders and SL RNAs in trypanosomatid protozoans or nematodes. However, several features, such as predicted secondary structure, trimethylguanosine cap, and potential Sm binding site, suggest similarities among SL RNAs in widely divergent organisms. Our evidence also indicates that the exon 3 acceptor site of the 3-hydroxy-3-methylglutaryl-CoA reductase gene can be spliced either to the SL by trans-splicing or to an upstream exon, 2, by cis-splicing. The presence of a SL sequence in S. mansoni, a member of the phylum Platyhelminthes, suggests that transsplicing may be a common feature ofother lower invertebrates.Trans-splicing ofpre-mRNA sequences was first described in trypanosomatid protozoans (1-3). In these organisms, small nonpolyadenylylated RNAs [spliced leader (SL) RNAs] of -100 nucleotides (nt) donate a 5'-terminal 39-nt SL sequence to all pre-mRNAs to form the 5' termini of mature mRNAs. In metazoans, the description of trans-splicing has been confined to the phylum Nematoda. Trans-splicing in nematodes resembles the situation in trypanosomes as exemplified by the detection of Y-branched intermediates and the presence of consensus 5' and 3' splice sites flanking the SL and pre-mRNAs, respectively (4-6). There are, however, several notable differences. Unlike trypanosomatid protozoans, only a subset of nematode mRNAs (10-15%) mature via addition of a distinct 22-nt SL sequence (7). In addition, processing of nematode mRNA includes both cis-and trans-splicing (4). Analyses ofthese mRNAs and corresponding genomic clones have suggested that only the first exon serves as an acceptor for the 22-nt SL sequence (8).The discovery of trans-splicing in nematodes raised the question of the prevalence of this reaction in other metazoans. Nucleotide sequence analysis of SL genes in different genera of nematodes has revealed perfectly conserved copies of the 22-nt SL sequence (7, 9, 10). The nematode SL, however, does not hybridize to RNA from other metazoans such as Schistosoma mansoni, Dictyostelium, Drosophila, Xenopus, and humans (7). If these organisms process their mRNAs by trans-splicing, it is likely to involve SL sequences that are not homologous to the nematode SL.Here we present evidence that a subset of polyadenylylated transcripts in the human parasite S. mansoni, a trematode, are processed art their 5' termini by addition of a distinct 36-nt SL sequencet that shares no sequence identity with the 22-nt SL in nematodes or the 39-nt SL in trypanosomatid protozoans. Trematodes, cestodes, turbellarians, and monogeneans are grouped together into the morphologically diverse phylum Platyhelminthes and are distinctly differ...

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Section: Resultsmentioning

confidence: 99%

A spliced leader is present on a subset of mRNAs from the human parasite Schistosoma mansoni.

Rajkovic

Davis

Simonsen

et al. 1990

Proc. Natl. Acad. Sci. U.S.A.

128

118

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“…When RXR forms heterodimers, such as RXR/RAR and USP/ecdysone receptor, the conformation of its binding partner changes allowing a greater affinity not only for the DNA response element but also for the ligand (43)(44)(45)(46)(47)(48)(49)(50)(51). RT-PCR results demonstrated that SmRXR mRNA is constitutively expressed throughout schistosome development, not only in mature females as are the female-specific genes (2,3,7,9,10). Furthermore, Western blot analysis showed that the 74-kDa SmRXR protein is present in both sexes, mature and immature.…”

Section: Discussionmentioning

confidence: 99%

“…Ligand binding is thought to change the conformation of the steroid receptor into an active state (51). The ability of members of the RXR subfamily to bind specific ligands appears to have evolved after the vertebrate and arthopod lineages diverged, as of yet ligands have not been found for arthropod 10 and 100 ϫ amounts, respectively. Lanes 6 -8, binding reactions contained a 250-bp fragment of a irrelevant DNA competitor in 10, 100, and 250 ϫ amounts, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…One gene, p14, encodes an eggshell precursor expressed only in vitelline cells of mature females in response to male stimulus (3,7,8). The region upstream of transcription initiation of p14 contains elements similar to those found in Drosophila and silkmoths that are known to regulate chorion gene expression in a sex-, tissue-, and temporal-specific manner (2,7,9,10).…”

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confidence: 99%

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Identification of a cDNA Encoding a Retinoid X Receptor Homologue from Schistosoma mansoni

Freebern

Osman²,

Niles

et al. 1999

Journal of Biological Chemistry

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Schistosoma mansoni, a multicelluar eukaryotic blood fluke, is a major cause of morbidity worldwide in humans. The study of female parasite growth, development, and gene regulation is important because the eggs produced are responsible for the pathogenesis observed in schistosomiasis. p14, an eggshell precursor gene expressed only in sexually mature females in response to a male stimulus, is a model for female-specific gene regulation. The upstream region of the p14 gene shares sequences present in insect genes known to be regulated in a sex-, temporal-, and tissue-specific manner by members of the steroid receptor superfamily. Herein, we report the identification and characterization of a cDNA that encodes the S. mansoni (Sm) RXR homologue. Sequence analysis predicts and Western blot analysis confirms the synthesis of a 74-kDa protein, the largest member of the RXR family reported to date. We show by electrophoretic mobility shift assay analysis that SmRXR binds to cis-elements of the p14 gene including a direct repeat that follows the "3-4-5" rule of binding elements recognized by members of the steroid receptor superfamily. Furthermore, we demonstrate that SmRXR can act as a transcription activator in the yeast onehybrid system. Through quantitative reverse transcriptase-polymerase chain reaction, we show that the SmRXR gene is constitutively expressed and thus must play multiple roles throughout the schistosome life cycle.

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“…Three clones were identified that shared 100% sequence identity with S. mansoni eggshell proteins. p97D2 encoded the EGG2 ORF (5,16), and both p25G7 and p43F7 encoded the ORF of EGG3 (25). Sex-specific gene products, notably those involved in reproduction, are attractive targets for antihelminth intervention strategies (3) actin I protein (Met-121 to Asp-189) gained a positive C and S score in the SignalP-NN program.…”

Section: Resultsmentioning

confidence: 99%

Isolation of cDNAs Encoding Secreted and Transmembrane Proteins fromSchistosoma mansoniby a Signal Sequence Trap Method

et al. 2003

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Surface and secreted proteins of schistosomes orchestrate the basic physiologic requirements of a parasitic existence. These proteins are often exposed to host tissues during penetration, migration, feeding, and immune evasion, and they are obvious targets for control strategies. Signal sequence trap (SST) represents a novel approach that selects for cDNAs encoding secreted and surface proteins with N-terminal signal peptides, so we constructed a randomly primed adult Schistosoma mansoni cDNA library fused to a signalless reporter gene encoding placental alkaline phosphatase. The library was used to transfect COS-7 cells, which were then assayed for the presence of reporter at the cell surface. Eighteen S. mansoni cDNA fragments were isolated and sequenced. Expression profiles of the novel clones were determined for different developmental stages; some transcripts were restricted to single-sex adult worms, while others were ubiquitously distributed. Most clones contained signal peptides or signal anchors as determined by the SignalP algorithm. Open reading frames (ORFs) were categorized as follows: (i) previously identified S. mansoni cDNAs encoding proteins of known function; (ii) cDNAs encoding proteins of known function in other organisms but novel for Schistosoma; (iii) S. mansoni expressed sequence tags (ESTs) of unknown function; and (iv) completely novel ORFs without homologues (including ESTs) from any phylum. Clones of particular interest included tetraspanins similar to human cell surface antigens, a protein kinase, and ORFs transcribed in the antisense orientation to previously characterized S. mansoni cDNAs. This is the first report describing the use of SST as a tool for identifying secreted proteins from any pathogenic organism.

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Small gene family encoding an eggshell (chorion) protein of the human parasite Schistosoma mansoni.

Cited by 61 publications

References 21 publications

A spliced leader is present on a subset of mRNAs from the human parasite Schistosoma mansoni.

A spliced leader is present on a subset of mRNAs from the human parasite Schistosoma mansoni.

Identification of a cDNA Encoding a Retinoid X Receptor Homologue from Schistosoma mansoni

Isolation of cDNAs Encoding Secreted and Transmembrane Proteins fromSchistosoma mansoniby a Signal Sequence Trap Method

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