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

Area of Science:

• Virology
• Cell Biology
• Structural Biology

Background:

• Flaviviruses replicate within replication organelles (ROs) on the endoplasmic reticulum, which also serve as assembly sites.
• The coordination between viral membrane remodeling, genome replication, virion assembly, and maturation within ROs remains poorly understood.

Purpose of the Study:

• To investigate the spatial and temporal coordination of tick-borne flavivirus genome replication, budding, and maturation.
• To elucidate the mechanisms of membrane remodeling and virion formation within ROs.

Main Methods:

• Cryo-electron tomography was used to image flavivirus replication in human cells.
• Cryo-electron tomography was also employed to visualize flavivirus replication in mouse brain tissue.

Main Results:

• The RO membrane bud is shaped by membrane modifications and intraluminal RNA pressure.
• A protein complex links the RO base to an adjacent membrane for immature virus budding.
• Furin site variants influence whether virus particles mature near ROs.
• Close spatial coupling of flavivirus genome replication, budding, and maturation was observed.

Conclusions:

• Flavivirus replication, budding, and maturation are spatially coupled processes.
• Membrane remodeling and RNA pressure are key factors in RO formation and function.
• Understanding these processes provides insights into flavivirus lifecycle and pathogenesis.