FIG. 2.

Comparison of replication efficiencies of KUN replicon RNAs with different cell-adaptive mutations in transient transfections. BHK21 cells were electroporated with replicon RNAs with different cell-adaptive mutations. (A) Forty-eight hours after electroporation, the cells were stained with X-Gal to detect cells positive for expression of β-galactosidase from KUN replicon RNA. (B) Total RNA (∼10 μg) isolated from electroporated cells was used for analysis of the accumulation of replicating RNA by Northern blotting with ³²P-labeled probes specific for KUN replicon RNA (top) or for β-actin mRNA (bottom). The arrows indicate positions in the gel of RNAs of 12.5 (top row) and 1.1 (bottom row) kb determined relative to migration in the same gel of the ethidium bromide-stained 1-kb Plus ladder (Invitrogen). Normalized KUN RNA levels show percentages of RNA levels from the wt RNA (100%) normalized to the levels of β-actin mRNA.