Mutational effects on viral infectivity and PA polymerase activity.

1Infectivity of viable recombinant virus is defined by viral titers at 20, 28, and 40 hpi time points during viral growth kinetic analyses (Fig. 1C and Fig. 4B). ++++, WT and 2 log; −, no virus. If no viable virus is rescued, infectivity is defined as −.2The level of RNA synthesis is determined by the 5-plasmid assay (Fig. 2 and Fig. 4C). ++++, >20% WT; +++, 2–20% WT; ++, 0.1–2% WT; +, 3Subcellular localization of PA protein in the presence of PB1 and PB2 proteins (Fig. 3). Nuc, nucleus; Cyt, cytoplasm; n/a, data not available.