FIG. 3.

Cell-adaptive mutations confer an advantage in establishing persistent replication of KUN replicon RNA in BHK21 cells. BHK21 cells were electroporated with replicon RNAs containing different cell-adaptive mutations (as in Fig. 2). Forty-eight hours after electroporation, medium with 5 μg of puromycin/ml was added, and the cells were propagated for an additional 7 days. Puromycin-resistant cell colonies were fixed in 4% formaldehyde and stained by crystal violet in phosphate-buffered saline.