Figure 4.

Adenovirus-producing foci after transfection of 293 cells. PacI-digested pAdEasy-GFP-GAL was transfected into 293 cells and GFP expression was visualized by fluorescence microscopy at the indicated times thereafter. Comet-like adenovirus-producing foci became apparent at 4–5 days. No such foci were observed in the cells transfected with circular (i.e., not PacI-digested) pAdEasy-GFP-Gal.