FIG. 2.

Plasmid containing only the DS of oriP replicates within C33A/EBNA-1 cells but is lost precipitously during 2 weeks posttransfection, as is the oriP plasmid. Equimolar amounts of an oriP test plasmid (oriP), a test plasmid containing only the DS of oriP (DS), and a test plasmid containing only the FR of oriP (FR) were introduced independently into C33A/EBNA-1 cells together with a prokaryotic backbone plasmid (Backbone). At the indicated times posttransfection, plasmid DNA was isolated by Hirt extraction and digested with XhoI and DpnI, and the level of replicated, DpnI-resistant DNA was determined by quantitative competitive PCR. PCRs were performed using 10⁵ cell equivalents and a competitor DNA standard curve (9 pg, 3 pg, 600 fg, 120 fg, and 24 fg). Numbers below each gel refer to the average number of molecules present per transfected cell.6d., day 6 posttransfection.