FIGURE 3.

(A) Schematic representation of the SARS-CoV-2 virus structure. Together with membrane (M), envelope (E) transmembrane proteins, the spike (S) glycoprotein projects from a host cell-derived lipid bilayer. The positive-sense viral genomic RNA is associated with the nucleocapsid proteins forming the ribonucleoprotein (Mandala et al., 2020; Yao et al., 2020; Zhao et al., 2020). (B) The coronavirus life cycle. The coronavirus binds to the specific receptor (for SARS-CoV-2 the ACE2) together with the host factor TMPRSS2. Following entry, from the viral genomic RNA a translation of the two large open reading frames (ORF1a and ORF1b) occur. The resulting polyproteins are processed into individual non-structural proteins (16nsps) that form the replication and transcription complex (RTC). Formation of nuclear double membrane spherules (DMVs) associated with RTC allows viral genomic RNA replication and transcription of subgenomic mRNAs (sg mRNA). Produced structural proteins translocate into endoplasmic reticulum (ER) membranes and transit through the ER to the Golgi intermediate compartment (ERGIC) where nucleocapsid proteins (N) interact with newly produced genomic RNA resulting in the budding into the lumen of vesicular compartments. Finally, virions are secreted by exocytosis from the infected cell.