Significance DNA transposons that translocate by excision from a donor site and insertion into a target site are often used for genome engineering by insertional mutagenesis and transgenesis. The piggyBac element is especially useful because it can excise precisely from an insertion site, restoring the site to its pretransposon state. Precise excision is particularly useful when transient transgenesis is needed, for example, in the transient introduction of transcription factors for induced pluripotent stem cell production. We have used mutagenesis to generate an Excision + Integration − transposase that allows piggyBac excision without potentially harmful reintegration. These mutations likely lie in a target DNA-binding domain.
