Figure 2.

Quantification of gene transfer rates by Southern-blot analysis. Southern-blot analysis was performed on genomic DNA from sorted GFP⁺ and GFP⁻ cells transduced with uninsulated and insulated vectors. DNA was digested with EcoRV restriction enzyme, which cuts once in each viral long terminal repeat, and the blot was hybridized contemporarily with specific the proviral probe (NEO sequence) and the specific mouse endogenous εy globin probe. The DNA from untransduced cells was used as negative control. The band intensities were quantified with a phosphoimager, and provirus signals normalized with the εy endogenous globin gene. DNAs from two clones bearing two copies (K1) and four copies (K2) of the provirus were loaded as a control for probe-binding efficiency. Vector copy number per cell (VCN/cell) is indicated at the bottom of each line.