FIG 3.

Identification of viral genes and amino acids that contribute to the difference in the polymerase activities of QT1728 and QT1480 viruses. (A) 293T cells were transfected with four protein expression plasmids for PB2, PB1, NP, and wild-type or mutant PA proteins, with a plasmid for the expression of a virus-like RNA encoding the firefly luciferase gene, and with a control plasmid encoding Renilla luciferase, and assayed after a 24-h incubation at 33°C and 37°C. (B and C) Minireplicon assays as described in panel A were carried out with the indicated mutant QT1480 (B) and QT1728 (C) PA proteins. (D to L) Minireplicon assays of QT1480, QT1728, and TY31 PA proteins possessing mutations at positions 343 and/or 347 in 293T (D to F), A549 (G to I), and DF-1 (J to L) cells. Data shown are mean values plus standard deviations for the results of three independent experiments. P values were calculated by one-way ANOVA, followed by Dunnett's test (*, P < 0.05; **, P < 0.01). In experiments carried out in parallel, cells were transfected as described above and processed for Western blot analysis.