FIG. 5.

Models for switching between influenza A viral transcription and replication. (A) Classical model. Early in infection, vRNA is transcribed to mRNA (primary transcription). Expression of NP switches primary transcription to replication (synthesis of cRNA and vRNA) and subsequent secondary transcription. (B) Proposed “stabilization” model. Early in infection, mRNA and cRNA are synthesized, but cRNA is degraded. Later in infection, once PB1, PB2, PA, and NP are synthesized, cRNA is stabilized as a cRNP complex that can be replicated to vRNA. See the text for further details.