The role of nuclear import and export in influenza virus infection.

Infection with influenza virus involves a complex series of nuclear import and export events. Early in infection, incoming viral ribonucleoproteins (vRNPs) are imported into the nucleus. Later, viral transcripts are exported from the nucleus, newly synthesized structural proteins are transported back into the nucleus and, finally, newly assembled vRNPs are exported. All these import and export steps, and, in particular, the bidirectional traffic of vRNPs rely on the transport machinery of the cell, but are regulated both by viral and cellular factors. The viral MI protein serves as the master organizer in determining the directionality of vRNP transport.