Cryo-electron tomography reveals coupled flavivirus replication, budding and maturation.

Area of Science:

• Virology
• Cell Biology
• Structural Biology

Background:

• Flaviviruses replicate and assemble within replication organelles (ROs) on the endoplasmic reticulum (ER) membrane.
• The coordination between viral genome replication, membrane remodeling, and virion maturation within ROs remains unclear.

Purpose of the Study:

• To investigate the spatial and temporal coordination of flavivirus replication, budding, and maturation processes.
• To elucidate the structural mechanisms underlying RO formation and virion production.

Main Methods:

• Cryo-electron tomography (cryo-ET) was used to image tick-borne flavivirus replication in human cells.
• Cryo-ET was also applied to visualize flavivirus replication in mouse brain tissue.

Main Results:

• RO membrane buds are shaped by coat proteins and intraluminal viral RNA pressure.
• A protein complex links ROs to adjacent membranes for immature virion budding.
• Furin site variants influence virion maturation proximity to ROs.

Conclusions:

• Flavivirus genome replication, virion budding, and maturation are spatially coupled processes.
• Structural insights into ROs and their associated protein complexes are crucial for understanding flavivirus lifecycle.