FIG. 2.

Stable long-term HSB- and SB-mediated gene transfer. Transgene expression over time in (A) K-562, (B) Jurkat, and (C) primary human CD34⁺ cells isolated from cord blood. Ten micrograms of the transposon plasmid (pT/MNDU3-eGFP-BGH) and 1 μg of either pCMV-SB (solid squares), pCMV-HSB (solid triangles), or pCMV-mutSB (solid circles) transposase-expressing plasmid were coelectroporated into each cell population. Cells were also electroporated with pT/MNDU3-eGFP-BGH alone (open squares) or with Amaxa Nucleoporation solution only, without added DNA (open diamonds), as controls. Aliquots of cells were analyzed by flow cytometry at each time point to determine the percentage of GFP-expressing cells and the percentage of propidium iodide (PI)⁺ cells. Each experiment was repeated three times (n = 3) with two or three replicates per experiment. Error bars represent the standard error of the mean (SEM).