Excision of the piggyBac transposable element in vitro is a precise event that is enhanced by the expression of its encoded transposase.

The piggyBac Lepidopteran transposable elementmoves from the cellular genome into infecting baculovirus genomes during passage of the virus in cultured TN-368 cells. We have constructed genetically tagged piggyBac elements that permit analysis of excisionwhen transiently introduced on plasmidsinto the piggyBac-deficient Spodopterafrugiperda IPLB-SF21AE cell line. Precise excisionof the element from these plasmidsoccurs at a higher frequency in the presence of a helper plasmidthat presumably supplies the piggyBac transposase. The results suggest that the piggyBac transposon encodes a protein that functions to facilitate not only insertion, but precise excisionas well. This is the first demonstration of piggyBac mobility from plasmidsources in uninfected Lepidopteran cells.