Activity of a Drosophila teissieri I-element retrotransposon in Drosophila melanogaster

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University of New Brunswick


Transposable elements play an important role in evolution, affecting genome structure and gene regulation. A retrotransposon reverse transcribes its own RNA to create a cDNA copy that is inserted in the genome, and its machinery can reverse transcribe other RNAs to produce retroduplications. The human L1 retrotransposon gene product ORF1 protein (ORF1p) has RNA-binding activity, while the ORF2 protein (ORF2p) is a reverse transcriptase and has endonuclease activity. The transposition of the I-element, an L1-related retrotransposon in Drosophila species, has been studied in vivo. In this study, a cloned D. teissieri I-element was designed to explore binding preferences of ORF1p to cellular transcripts in the germline to contribute to understanding the process of retroduplication. To determine the types of RNA that are associating with ORF1p, three transgenic D. melanogaster strains were constructed. One transgenic strain expresses an epitope-tagged HA-ORF1p. Expression of HA-ORF1p in ovaries, followed by immunoprecipitation to isolate ribonucleoprotein particles (RNPs) bound to HA-ORF1p, would allow for the ORF1p-bound RNAs to be isolated. The other two transgenic strains were used to assess the full-length I-element clone for its ability to transpose, and to determine if the HA epitope tag in ORF1p affects this transposition. I determined that there is RNA expression of the I-element transgenes while using a GAL4 driver; however, assays used to detect new DNA copies of the I-element were negative, as were assays to detect female sterility induced by I-element activity, suggesting that this I-element has little to no transposition activity.