The African blood fluke Schistosoma mansoni is the etiological agent of intestinal schistosomiasis, the most serious of the helminth parasitic diseases. LTR retrotransposons make up substantial portions of eukaryotic genomes and are important both for their roles in genome evolution and instability and for their potential use in various applications. At the outset of this study, we hypothesized that LTR retrotransposons exist in the genome of S. mansoni, that most but not all copies of these retrotransposons will be inactivated due to the accumulation of mutations, and that mechanisms must exist to prevent uncontrolled proliferation of these elements. In addition, we hypothesized that similar elements should exist in either closely related platyhelminth organisms, or in host species of schistosomes The first LTR retrotransposon to be characterized from the genome of Schistosoma mansoni, designated Boudicca, included direct LTRs 328 bp in length and three open reading frames encoding gag, pol, and an unknown gene. Boudicca was a member of the recently characterized CsRn1 subclade of Gypsy-like retrotransposons and was transcribed in the sporocyst, cercaria and adult developmental stages of S. mansoni. Boudicca's copy number was found to exceed 1,000, with the fully characterized copy resembling the sequences of mRNA transcripts produced by RT-PCR. Models of the secondary structure of the Boudicca transcript suggested a transcription or translation based method of regulation of Boudicca proliferation The second LTR retrotransposon characterized during these studies, Sinbad, belongs to one of five discreet subfamilies of Pao/BEL like elements, which were found to be present only in animal genomes. Sinbad was 6,287 bp long, was flanked by identical LTRs of 386 bp, and displayed genomic features characteristic of Pao/BEL elements. There are about 50 copies of Sinbad in the S. mansoni genome. ESTs representing transcripts of Sinbad were found in six developmental stages of S. mansoni. The LTRs of Sinbad, but not Boudicca, were able to drive luciferase expression in HeLa cells, indicating that they represent functional promotors. Sinbad's LTRs also appear to function bidirectionally Both Boudicca and Sinbad were shown by Southern hybridization to be present in the genome of the related schistosome, Schistosoma haematobium / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_26668 |
| Date | January 2005 |
| Contributors | Copeland, Claudia S (Author), Brindley, Paul (Thesis advisor) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
Page generated in 0.0032 seconds