Transposon-independent increase of transcription by the Sleeping Beauty transposase

When a plasmid encoding the Sleeping Beauty (SB) transposase (pCMV-SB) was cointroduced with luciferase expression plasmid DNA into mouse skeletal muscle at a molar ratio of 4:1, luciferase gene expression was 5 times higher than the expression without pCMV-SB on day 28. This enhancement was not dependent on the presence of transposon (Tn) sequence in luciferase expression plasmid. Southern blot analysis failed to detect luciferase gene insertion into the host genome. Then, expression, a luciferase expression plasmid without Tn, was cointroduced into HeLa cells with or without pCMV-SB. With pCMV-SB, the mRNA amount and the luciferase activity were 1.5 times and 2 times higher, respectively, than without pCMV-SB, even though the cells with pCMV-SB had a smaller copy number of luciferase plasmids than the cells without pCMV-SB. These results suggest that SB transposase enhances the transcription of an exogenous gene regardless of the presence of the Tn sequence.