Figure 2. Model for vRNP nuclear import.
Uncoated, cytoplasmic vRNPs with exposed NP NLS motifs associate with IMPα, which in turn associates with IMPβ. The entire complex docks at the NPC and is transported into the nucleus, where Ran-GTP binds IMPβ and facilitates vRNP release into the nucleoplasm to initiate transcription and replication. Whether multiple IMPα and IMPβ molecules associate with each vRNP is unknown, as is the fate of the vRNP-associated IMPα once the vRNP cargo is released into the nucleoplasm.