FIG. 4.

Primer extension analysis of transduced vector proviruses with putative insulators. Genomic DNA from G418-selected populations of F9 and NIH 3T3 cells transduced in parallel with vectors as indicated above each lane were employed for PCRs with primers specifically amplifying the transduced provirus. Amplified fragments were subjected to primer extension dideoxy termination analysis with an end-labeled primer as shown in Fig. 3 to analyze the presence of Pro PBS and B2 PBS proviruses. Extension products were resolved by denaturing polyacrylamide gel electrophoresis, visualized after exposure in a Personal Molecular Imager Fx, and quantified by using Quantity One software. The ratio of B2 PBS to Pro PBS band intensities is given below each lane. Panels A and B are from two independent experiments.