Figure 2.

Complete life cycle of SARS-CoV-2. SARS-CoV-2 lifecycle begins with primary binding of the Spike protein to its specific receptors (ACE2). Mostly host cell entry depends on several steps: (i) Initial cleavage of S1/S2 specific sites by surface transmembrane protease serine-2 (TMPRSS2) and furine, (ii) followed by virus–cell membrane fusion and endocytosis. (iii) Continuing from endocytosis, m-RNA genome is mainly released into the cytosol and translated into the polyproteins. Mostly polyproteins (pp1a and pp1ab) are cleaved by specific viral-encoded protease (VEP) into the several nonstructural proteins (nsps) (mostly including RNA-dependent RNA polymerase: RdRp) which is responsible for replication transcription complex (RTC) in the cells. (iv) Viral replication begins with virus-induced double membrane vesicles mainly derived from the endoplasmic reticulum (ER). (v) Positive-strand of genome serves as a main template for full-length negative-strand RNA and sub genomic (sg)RNA and sgRNA translation results in both structural proteins and accessory proteins are inserted into the ER–Golgi intermediate compartment (ERGIC) for virion assembly, respectively. (vi) RNA genomes with specific nucleocapsid proteins are incorporated into newly synthesized virions, which are secreted by exocytosis. DMV—double-membrane vesicle.