The NP-mPB showed a 3- to 4-fold increase in transposon integration efficiency.

<p>The <i>UGm</i> transposon, alone or mixed with the mPB or NP-mPB expression vector, was co-electroporated into mouse or human embryonic stem (ES) cells and then selected for G418 resistance. Surviving colonies were stained by crystal violet and counted. There were more colonies in the NP-mPB group than in the mPB group in mouse ES (A), human ES (B), and Hela cells (C). (D–F) Transposition events were quantified by counting the colonies on culture plates. The transposition efficiency mediated by NP-mPB was increased 3- to 4-fold in mouse ES cells (D), 3-fold in human ES cells (E), and approximately 3-fold in Hela cells (F). n = 3 for each condition; bars indicate mean ± standard error; ** <i>P</i><0.01, *** <i>P</i><0.001.