FIG 6.

The effect of the P4 residue is abolished if P123 polyprotein processing is blocked. (A) Illustration of Gly-to-Val substitutions at the P2 positions which prevent cleavage at the respective cleavage sites. Corresponding replicases with mutations at the 1/2 and 2/3 sites are designated P1*2*34. (B and C) U2OS WT or ΔΔ cells were cotransfected with indicated SFV (B) or CHIKV (C) trans-replicases and corresponding templates. Fluc (replication) and Gluc (transcription) activities were measured at 18 h posttransfection, normalized to signals obtained from control cells transfected with catalytic-inactive replicases and corresponding templates, and plotted as the fold change. Data are the means of the results from three independent experiments. Error bars indicate the SD. Statistical differences are as follows: ns, P > 0.05; *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001; ****, P ≤ 0.0001.