Question

The corvid-9 virus is an RNA virus, but it is not a retrovirus. Briefly, how does its replication in the host cell differ from a retrovirus?

Answer 1

Retroviruses are a type of virus that have RNA genome. Their mode of replication involves producing a copy of ds DNA from their RNA genome using enzyme reverse transcriptase/ RNA dependant DNA polymerase and integrating the DNA copy into the genome of host cell making it a permanent element of host genome. When the host genome replicates and produces mRNA and proteins, they eventually synthesize viral structural and non-structural proteins. Thereby promoting growth of virus particles inside the cell.

Though Coronavirus is a positive ss RNA containing virus but they do not replicate their genome by integrating into host genome. Instead, the covid-19 consists a 3’ poly A tail and 5’ cap structure at the ends of the RNA genome, which makes them act as mRNA for translating and producing all the required replicase polyproteins. The viral genome consists 14 open reading frame (ORFs). The ORF encodes auto-proteolytic polyproteins that cleaves and produces 16 non-structural proteins. These non-structural proteins form transcriptase-replicase protein consists many enzymes required for replication of viral genome including RNA-dependent RNA polymerase, endo-exo- nucleases and many other. The 3’ end of viral genome encodes 13 ORF that encodes viral structural proteins such as envelope (E), spike (S), membrane (M) and nucleocapsid (N) proteins. They mark their entry into host cell by binding to angiotensin converting enzyme 2 receptor. After entry into host cell they replicate the genome and produces multiple copies of viral particles which further infects different types of cells.