In Vitro Assembly of PB2 with a PB1-PA Dimer Supports a New Model of Assembly of Influenza A Virus Polymerase Subunits into a Functional Trimeric Complex.

Deng T, Sharps J, Fodor E, Brownlee GG.

Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom. george.brownlee@path.ox.ac.uk.

Influenza virus RNA-dependent RNA polymerase is a heterotrimeric complex of PB1, PB2, and PA. We show that the individually expressed PB2 subunit can be assembled with the coexpressed PB1-PA dimer in vitro into a transcriptionally active complex. Furthermore, we demonstrate that a model viral RNA promoter can bind to the PB1-PA dimer prior to assembly with PB2. Our results are consistent with a recently proposed model for the sequential assembly of viral RNA polymerase complex in which the PB1-PA dimeric complex and the PB2 monomer are transported into the nucleus separately and then assembled in the nucleus.