Hyperactive piggyBac transposase R372A/K375A/D450N (hyPBase R372A/K375A/D450N)
Excision-hyperactive integration-defective piggyBac variant engineered for transgene-free genome editing. Combines hyperactive iPB7/hyPBase backbone with three catalytic domain mutations achieving 5-6-fold higher excision than wild-type PBase while maintaining near-complete integration deficiency, enabling safe transposon removal without reintegration risk.
Origin: Scanning alanine mutagenesis and error-prone PCR from hyperactive piggyBac transposase (iPB7/hyPBase)
Characteristics
Engineered through rational mutagenesis of conserved basic residues in the piggyBac catalytic domain. R372A and K375A mutations eliminate integration activity by disrupting target DNA binding, while D450N suppressor mutation restores excision to hyperactive levels. Achieves 5-6-fold higher excision frequency than wild-type piggyBac in both HEK293 cells and yeast while producing zero blasticidin-resistant colonies in integration assays. Retains hallmark precise excision with <1% footprint frequency. In vitro assays confirm robust double-strand break formation, hairpin opening activity, but near-complete deficiency in target DNA joining. The variant maintains TTAA tetranucleotide target site specificity and functions across diverse mammalian cell types.
Applications: Enables transgene-free iPSC generation by allowing safe excision of reprogramming factor cassettes without genome reintegration risk. Eliminates the 40-60% reintegration frequency observed with wild-type piggyBac during excision-based transient transgenesis workflows. Supports non-viral genome engineering applications requiring reversible transgene insertion including CAR-T cell manufacturing, gene therapy vector development, and functional genomics screens where transposon removal is essential. Applicable to primary cells, ES cells, and established cell lines for applications demanding high excision efficiency without integration burden.
Limitations: Integration deficiency prevents standard transgenesis applications requiring stable genomic insertion. Requires co-delivery of transposase expression plasmid or mRNA alongside transposon donor, adding delivery complexity. Constrained by TTAA target site availability and lacks programmable targeting capability. Integration activity cannot be easily restored through simple modifications; N-terminal zinc finger fusions can partially rescue integration but do not provide site-specific targeting. The D450N suppressor mutation position near catalytic residue D447 may affect long-term enzyme stability in some contexts.