The influenza virus contains a segmented RNA genome with
eight negative-sense segments encoding 11 proteins. The influenza
virus polymerase is a heterotrimeric 250-kDa complex
with the following three protein subunits: PA, PB1, and PB2. It
plays central roles in the viral life cycle and is directly responsible
for RNA synthesis for both viral replication and transcription.
However, the mechanisms by which these two different RNA
synthesis functions are regulated within the large polymerase
complex remain unclear.