Structure–function relationships of the influenza virus RNA polymerase

Influenza virus RNA polymerase is composed of three viral P proteins (PB1, PB2 and PA) and involved in both transcription and replication of the viral RNA genome. Using recombinant baculoviruses, we constructed the PA–PB1–PB2 (3P) complex and two kinds of 2P complex (PA–PB1 and PB1–PB2). The 3P complex is not fully active but vRNA acts as “RNA effector” for conversion of it into an active form. The cap structure (7mGpppAm) also plays an allosteric effector for RNA polymerase activation. The PB1–PB2 complex carries the catalytic specificity of transcriptase, while the PA–PB1 complex harbours the replicase specificity. We propose that the 3P complex behaves as the PB1–PB2 complex in transcription and the PA–PB1 complex in replication. A host factor(s) seems to be involved in the functional conversion of 3P complex. The candidate host factors have been isolated using yeast two-hybrid screening. [Copyright &y& Elsevier]