Figure 2.

Schematic model of single-stranded positive-sense RNA viruses (ssRNA(+)) virus replication organelle biogenesis in the endoplasmic reticulum. After entry of the virus via the endocytosis pathway, its positive-stranded RNA genome is released into the cytoplasm by membrane fusion. Viral non-structural proteins are directly or indirectly interacted with lipid modifiers, which deform the endoplasmic reticulum (ER) membranes to create vesicle packets (VPs) for the replication of their genomic RNA. Newly synthesized ssRNA(+) is transported outside the VP to be used as a template for further viral protein synthesis or, alternatively, to the site of progeny virus particle assembly. The site of virus particle assembly is generally close to a VP pore. Reticulon (RTN) family proteins are involved in VP formation, and endosomal sorting complex required for transport (ESCRT) proteins can function in VP or virus particle formation. Progeny virus particles are sorted into coat protein complex II (COP II) vesicles and released via the conventional secretion pathway. Apart from this pathway, autophagosomes or EDEMosomes have been proposed to be involved in the formation of the ssRNA(+) virus replication compartment.