The novel coronavirus (COVID-19) known as Severe Acute Respiratory Syndrome coronavirus - 2 (SARS-CoV 2) declared as a pandemic on 11th March 2020. The Symptoms of infection are same as Severe Acute Respiratory Syndrome coronavirus (SARS-CoV). The genomic sequence of novel coronavirus has about 79.6% sequence identity with (SARS-CoV). Random mutations and recombination are the main causes for the genetic diversity of this virus. Coronaviruses have large positive, single stranded RNA genomes with 5′ end capped and 3′ end polyadenylated. The genome is about 30 Kb in length encoding 9860 amino acids. The 5’ end of the genome consists of two large replicase open reading frames like ORF1a and ORF1b that encodes polyproteins PP1ab and PP1a. The polyproteins are then breakdown to yield 16 non-structural proteins which include RNA-dependent RNA polymerase, papain-like proteinase protein, 2'-O-Ribose-Methyltransferase etc., which are involved in viral RNA synthesis. The 3′ end one-third of the genome encode many structural and accessory protein like spike (S) glycoprotein, matrix (M) glycoprotein, envelope (E) protein, nucleocapsid(N) phosphoprotein, they are expressed by a discontinuous transcription process from a set of 5′ leader-containing subgenomic mRNAs. Coronavirus protein synthesis occurs as cap-dependent translation mechanisms and other regulatory mechanisms, like ribosomal frame shifting mechanism. Coronavirus replication affects the process of cellular translation, like activation of stress-induced signalling pathways, releasing viral proteins that inhibit cellular mRNA translation and stability of RNA. More cytokines are produced from highly inflammatory cells which leads to cytokine storm. Cytokine storm and accelerated host immunity response makes disease symptoms more severe during SARS-CoV2 infection. Ribose 2′-O-methylated viral RNA cap supports the virus to escape from host immunity barrier. This topic depicts current scenario of understanding the mechanism of coronavirus mRNA translation, changes in host mRNA translation, induction of Cytokine storm, how the virus escape from host immunity barrier that is observed in corona virus-infected cells.
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