FIG. 6.

Efficient transcriptional activation from an oriP plasmid does not promote its precipitous loss. The level of replicated oriP test plasmid (oriP) and oriP test plasmid lacking the thymidine kinase promoter (ΔTKp) was monitored over 16 days posttransfection in 293/EBNA-1 cells as described in the legend to Fig. 3A. The replication level of these plasmids was plotted versus the days posttransfection. For each independent experiment, the level of replicated test plasmid detected at 6 days posttransfection was set to 100%, and the replication level at later time points was set relative to this point (100% = 403 oriP and 318 ± 175 ΔTKp molecules per transfected cell). The loss of the ΔTKp plasmid is representative of three independent experiments conducted in parallel to the oriP test plasmid. The 4% rate-of-loss curve, depicted by black cross-hatched boxes, is theoretical and is based on previous studies of established, drug-resistant cell clones (29, 56).