Fig 6. Schematic illustration of the mechanism of EV-A71 DNA-launched infectious clone.

The viral RNA requires exportation to the cytosol for cap-independent translation by mRNA export complexes. The HH ribozyme removes the m⁷G cap and thus ensures precise 5’ ends of the EV-A71 transcripts. The HDV ribozyme removes the SV40 termination signal and ensures precise 3’ ends of viral RNA. Viral RNA is exported into the cytosol by RNA export complexes. The m⁷G cap is required for nuclear RNA export. Removal of the cap diminishes the RNA exportation efficiency and therefore, reduces overall virus production. In vitro-transcribed infectious RNA is transfected into the cytosol for IRES-dependent translation. All newly synthesized positive-strand viral RNA are VPg-linked. RE indicates restriction enzyme; and IVT indicates in vitro transcription.