Gulliver, a long terminal repeat retrotransposon from the genome of the oriental blood fluke Schistosoma japonicum

We characterized the consensus sequence and structure of a long terminal re peat (LTR) retrotransposon from the genome of the human blood fluke, Schist osoma japonicum, and have earned this element, Gulliver. The full length, c onsensus Gulliver LTR retrotransposon was 4788 bp, and it was flanked at it s 5'- and 3'-ends by LTRs of 259 bp. Each LTR included RNA polymerase II pr omoter sequences, a CAAT signal and a TATA box, Gulliver exhibited features characteristic of a functional LTR retrotransposon including two read thro ugh (termination) ORFs encoding retroviral gag and pol proteins of 312 and 1071 amino acid residues, respectively. The gag ORF encoded motifs conserve d in nucleic acid binding proteins, while the pol ORF encoded conserved dom ains of aspartic protease, reverse transcriptase (RT), RNaseH and integrase , in that order, a pol pattern conserved in the gypsy lineage of LTR retrot ransposons. Whereas the sequence and structure of Gulliver was similar to t hat of gypsy, phylogenetic analysis revealed that Gulliver did not group pa rticularly closely with the gypsy family. Rather, its closest relatives wer e a LTR retrotransposon from Caenorhabditis elegans, mag from Bombyx mori a nd, to a lesser extent, easel from the salmon Oncorhynchus keta. Dot blot h ybridizations indicated that Gulliver was present at between 100 and severa l thousand copies in the S. japonicum genome, and Southern hybridization an alysis suggested its probable presence in the genome of Schistosoma mansoni . Transcripts encoding the RT domain of Gulliver were detected by RT-PCR in larval and adult stages of S. japonicum, indicating that (at least) the RT domain of Gulliver is transcribed. This is the first report of the sequenc e and structure of an LTR retrotransposon from any schistosome or indeed fr om any species belonging to the phylum Platyhelminthes. (C) 2001 Elsevier S cience B.V. All rights reserved.