Armênio Uzunian
J. Bras. Patol. Med. Lab. 2020;56(1):1-4
DOI: 10.5935/1676-2444.20200053
ABSTRACT
The causative agent of Covid-19, the severe acute respiratory syndrome (SARS), is a virus belonging to the Coronaviridae family, named SARS-CoV-2, which shows high homology with the virus that caused the SARS outbreak in 2003, SARS-CoV(1). SARS-CoV-2 is a ribonucleic acid (RNA) virus, whose genetic material is a single positive RNA molecule (+RNA). Its entire genome contains less than 30,000 nucleotides, each one formed by a sugar molecule (ribose), a phosphoric acid and a nitrogenous base. Because it is an RNA virus, the nitrogenous bases are adenine, cytosine, guanine, and uracil. Approximately 29 different viral proteins are identified; among them, the most relevant are the spike (S) glycoprotein, and the nucleocapsid (N) protein(2). The spike glycoprotein enables the virus entry into the host cell via binding to cell receptor and membrane fusion. The nucleocapsid protein, in its turn, regulates the process of viral replication.
SARS-CoV-2 is classified as +RNA because of its 5’-3’ direction, meaning it can be directly read by cell structures. It is regarded as a type of messenger RNA that, when translated by cellular ribosomes, induces the production of viral proteins. Another characteristic of this type of RNA is the presence of the replicase enzyme (RNA polymerase), which accompanies the virus or is produced by the infected cells, when then the production of a negative (-) RNA molecule occurs from the +RNA molecule, typical of the virus. The -RNA molecule is transient, and based on it, innumerable +RNA molecules are produced that are identical to the original +RNA. Therefore, the transient -RNA molecule serves as a template for the production of +RNA molecules; each of them will descend from the virus that infected the cell; these descendants will parasitize the cell and reproduce inside it. Read More…
