Orchestrated and dynamic nucleotide addition cycle during respiratory syncytial virus early-stage elongation.

Summary

High-resolution cryo-EM captures RSV polymerase across four nucleotide addition cycle states, revealing large-scale domain rearrangements and micro-motif interactions that coordinate catalysis. These structural insights identify conserved interaction networks as potential antiviral targets against RSV and related mononegavirales.

Key Findings

• Captured four discrete NAC states (NTP-bound, pre-reaction, pre-translocation, post-translocation) of the RSV L:P polymerase during early elongation.
• Observed all five L domains in NTP-bound and post-translocation states, versus only two domains in pre-reaction and pre-translocation.
• Revealed dynamic interaction networks among catalytic residues/motifs, RNA template/product, incoming NTP, and metal ions across states.
• Provides structural basis to target conserved motifs and interfaces for antiviral drug design.

Clinical Implications

Although preclinical, the defined NAC-state interaction hotspots can guide small-molecule or nucleotide analog inhibitor development, with potential translation to broad antivirals against RSV and other nonsegmented negative-sense RNA viruses.

Limitations

• In vitro structural snapshots without in vivo validation.
• Drug inhibition or resistance mutations were not experimentally tested in this study.

Future Directions

Integrate structure-guided medicinal chemistry to target NAC-state interfaces; validate inhibitory mechanisms in cell and animal models; assess conservation of targetable motifs across mononegavirales for pan-family antivirals.