Fig. 1

Detailed schematic of plasmids. All four plasmids contained a ZsGreen reporter gene driven by a cytomegalovirus (CMV) promoter. Functional retroviral sequences required for virus production (indicated by the line designated RV) are present in plasmids A, B, and C. Control plasmid D lacked the 5′ LTR and the packaging sequence (Ψ) and therefore was not able to generate virus, but expressed ZsGreen. In hybrid plasmid C the retroviral sequence was imbedded into the minimal piggyBac vector (line designated as minPB). The reporter gene, RFP (turboRFP—Red Fluorescent Protein) is driven by the EF1α promoter. PiggyBac transposase and truncated piggyBac terminal domains are required for minimal piggyBac integration, but these sequences do not integrate into target chromatin. Arrows indicate the orientation of the operons. Prokaryotic origin of replication and ampicillin resistance gene are not shown. (Vectors are aligned for easier comparison, but distances are not drawn to scale). LTR full-length wild type gamma-retroviral long terminal repeat, CMV/MSV/5′LTR hybrid 5′ LTR consists of the CMV type I enhancer, MSV the mouse sarcoma virus promoter linked to the truncated part of the retroviral long terminal repeat, 3′LTR(SIN) self-inactivated retroviral long terminal repeat, TRmin minimal piggyBac terminal repeat, pA SV40 polyadenylation signal, BPase piggyBac transposase gene driven by the PGK promoter, TD(trunc.) truncated piggyBac terminal domain