Scheme 1.

Coronavirus life cycle. Most Coronaviruses enter the cell after S protein–receptor interaction (1), the viral genome is released in the cytoplasm (2) and translated into the replicase polyprotein (3) to synthetize viral RNA (4). Genomic (progeny) and subgenomic RNAs are produced (5) and the latter are translated to structural and accessory proteins that can be inserted in the endoplasmic reticulum (ER; 6) and moved to the endoplasmic reticulum-Golgi intermediate compartment (ERGIC), while a fraction of S protein is transported directly to the cell surface where it mediates cell–cell fusion (7). In the ERGIC, the viral assembly and the encapsidation of genomic RNA by N protein take place, leading to nucleocapsid formation (8). Mature virions are then transported in smooth-walled vesicles (9) and released via exocytosis (10). N: nucleocapsid, S: spike, M: membrane, E: envelope. The scheme has been created with BioRender.com.