Fig 4.

In vitro polymerase activities of different viral RNP gene combinations. Four expression plasmids (PB2, PB1, PA, and NP) were used to yield the 16 RNP gene combinations of CT-Sw/1204 and Sw/1130, together with pHW72-Luci_M, which carried the reporter luciferase gene. The transfected 293 cells were assayed for luciferase activity after 24 h of incubation at 33°C (upper respiratory tract temperature; solid bars) or 37°C (lower respiratory tract temperature; hatched bars). The values shown are means and standard errors of the mean of the results of 3 independent experiments performed in triplicate, which are standardized to the activity of the expression plasmids for the CT-Sw/1204 vRNP complex proteins (100%). Segments derived from CT-Sw/1204 are shown in italics. “r” denotes reconstituted. *, P < 0.05, and **, P < 0.01 compared to polymerase activities relative to the homologous CT-Sw/1204 vRNP (r1) complex (two-tailed unpaired t test).