Zebedee: a novel copia-Ty1 family of transposable elements in the genome of the medically important mosquito Aedes aegypti.

Abstract

We have utilised PCR to directly identify a novel family of copia-Ty1 retrotransposable elements (RTPs) in the genome of the mosquito Aedes aegypti. Two members of the family have been sequenced in their entirety and their structural characteristics determined. ZebedeeI is 3505 bp long and appears to be flanked by 21bp direct repeat sequences. A single open reading frame (ORF) of 972 amino acids has the coding potential for a polyprotein with homology corresponding to the conserved amino acid motifs of Long Terminal Repeat (LTR) retrotransposon protease, integrase and reverse transcriptase. ZebedeeII likewise shares significant homology with these regions and also appears to be flanked by short direct terminal repeat sequences of 22 bp. Fifty copies of the 22 bp repeat sequence are present abutting the 5' end of ZebedeeII, with two (partial) representatives of this repeat sequence being present at the 3' end. The Zebedee family appears to have a low middle repetitive copy number in different strains of Ae. aegypti; and transcripts of the elements have been detected in cultured mosquito cells by RT-PCR. Despite the lack of a gag homologue or the LTR hallmarks of previously characterised copia-Ty1 RTPs, phylogenetic analyses place Zebedee within this group, showing considerable homology to copia from Drosophila melanogaster.