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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Insect Behavior and Biocontrol Research » Research » Publications at this Location » Publication #188916
Title: SCHISTOSOME RETROTRANSPOSONS

Author
item BRINDLEY, P - TULANE, NEW ORLEANS, LA
item Copeland, Claudia
item KALINNA, B - HUMBOLDT UNIV., GERMANY

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 5/15/2004
Publication Date: 1/1/2005
Citation: Brindley, P.J., Copeland, C.S., Kalinna, B.H. 2005. Schistosome retrotransposons. In: Secor, W.E., Colley, D.G., editors. Schistosomiasis, World Class Parasites Series. New York:Springer. p. 13-26.

Interpretive Summary: Schistosomiasis, caused by flatworms of the Schistosoma genus (schistosomes), is the most serious of the parasitic worm diseases, with more than 200 million people infected worldwide. At this point in time, there is no vaccine against schistosomiasis. While at Tulane University, a scientist now at the Center for Medical, Agricultural and Veterinary Entomology (Gainesville, Fl) worked on an enhanced understanding of the genomes of schistosomes, that might help lead to the development of a vaccine against this disease. Up to half of the genome of Schistosoma is composed of semi-autonomous stretches of DNA known as mobile genetic elements. Some of these elements, known as Class II elements or DNA transposons, move around the genome by “cutting” themselves out and then “pasting” themselves into a new location. Other elements, known as Class I elements or retrotransposons, make RNA copies of themselves which are then copied back into DNA (reverse transcribed) using a protein called reverse transcriptase, and these DNA copies are then inserted into new locations in the genome. The retrotransposons, in turn, include two distinct types, one type that is similar to retroviruses like HIV (the LTR retrotransposons) and one type that is not similar to retroviruses (the non-LTR retrotransposons). This chapter describes the seven retrotransposons (five non-LTR retrotransposons and two LTR retrotransposons) of the two major schistosome parasites of humans, Schistosoma mansoni and Schistosoma japonicum. The genetic structures of the retrotransposons are described and compared to the genetic structures of similar elements. In addition, the DNA sequences are used to place the elements in an evolutionary context, showing their relationships to similar retrotransposons from very different host species.

Technical Abstract: Eukaryotic genomes include substantial proportions made up of mobile genetic elements (MGEs). Up to half of the relatively large schistosome genome (~270 megabase pairs) may be composed of such elements. MGEs can either transpose through a DNA-mediated (Class II) or RNA-mediated (Class I) pathway. Class II elements are known as transposons and Class I elements are known as retrotransposons. Retrotransposons in turn can be divided into two groups based on their genetic structure and mode of transposition. These are the retroviral-like LTR retrotransposons, which use direct repeats to prime their reverse transcription, and the non-LTR retrotransposons, which replicate via target-site primed reverse transcription. This chapter describes the structure and phylogeny of the LTR- and non-LTR retrotransposons from the genomes of Schistosoma mansoni and Schistosoma japonicum that had been described at the time of submission of this chapter (2004). These included the non-LTR retrotransposons SR1 and SR2 from S. mansoni and SjR1, SjR2, and pido from S. japonicum. The SR1 and SjR1 elements are related to the CR (Chicken Repeat) elements of Gallus gallus, the SR2 and SjR2 elements are related to the human L1 elements and RTE elements of C. elegans, and the pido element appears to occupy a unique clade. The LTR elements described in this chapter are Gulliver from S. japonicum and Boudicca from S. mansoni. Gulliver is closely related to the Mag element of the silkworm moth Bombyx mori. Boudicca is closely related to Kabuki of Bombyx mori and to CsRn1, a newly described element of another platyhelminth parasite, the Chinese liver fluke Chlonorchis sinensis.