Table 1.

Comparison of Sleeping Beauty, piggyBac, and Tol2 characteristics, associated technologies and applications.

	Sleeping Beauty (SB)	piggyBac (PB)	Tol2
Species of origin	Salmonid fish [21]	Cabbage looper moth	Medaka fish [29]
Classification	Tc1/mariner superfamily [21]	PB superfamily	hAT superfamily [30]
Transposable element	~1.6 kb long	~2.5 kb long	~4.7 kb long
Terminal regions	IR/DRs of ~ 230 bp	35–63 bp with outer TIRs and inner subterminal IRs	150–200 bp containing the TIRs and subterminal regions
Transposase	340 aa	594 aa	649 aa (most active isoform)
Footprint	CAG [13]	None [84]	Variable [29]
Target site preference	TA [36]	TTAA [84]	Weak consensus sequence TNA(C/G)TTATAA(G/C)TNA [101]
Target site duplication	TA [13]	TTAA [84]	8 bp [101]
Activity in species	Various vertebrates	Vertebrates, insects, plants, yeast	Various vertebrates
Efficiency in human cells	Comparable to retroviral vectors [44]	Comparable to retroviral vectors [85]	Lower than PB and SB [107]
Cargo capacity	>100 kb [83]	>100 kb [83]	>100 kb [114]
Overproduction inhibition	Yes [107]	To some extent [107]	Lower than PB and SB [107]
Integration profile	Close-to-random [107]	Biased towards TSSs, CpG islands and DNaseI hypersensitivity sites [107]	Biased towards TSSs, CpG islands and DNaseI hypersensitivity sites [107]
Most common parental plasmid	pT2	pXL-BacII	pTol2, miniTol2
Most hyperactive transposase	hySB100X [45]	hyPB [85]	hTol2-M [101]
Vectors for transposon delivery	Plasmid DNA, pFAR, MC, non-integrative viral vectors, nanoparticles	Plasmid DNA, dbDNA, non-integrative viral vectors, nanoparticles	Plasmid DNA
Vectors for transposase delivery	Plasmid DNA, mRNA, SNIM RNA, recombinant protein (hsSB), non-integrative viral vectors, nanoparticles	Plasmid DNA, mRNA, non-integrative viral vectors, nanoparticles	Plasmid DNA, mRNA, recombinant protein (His-Tol2)
Clinical trials	Yes	Yes	No