1. The virus you isolated is an enveloped RNA virus. RNA isolated from this viru
ID: 212770 • Letter: 1
Question
1. The virus you isolated is an enveloped RNA virus. RNA isolated from this virus is capable of supporting translation in a rabbit reticulocyte cellfree translation system or in any other such system. Further analysis indicates that this virus replication is not inhibited by actinomycin D, a strong inhibitor of DNA-dependent RNA polymerase. Based on this information, discuss the mechanism by which this virus replicates in infected HeLa cells in culture.
2. The virus you isolated recently is a naked icosahedral RNA virus. RNA isolated from this virus is capable of supporting translation in a rabbit reticulocyte cellfree translation system or in any other such system. Further analysis indicates that this virus replication is inhibited if infected cells are incubated with protease inhibitor such as trypsin inhibitor. Based on this information, discuss the mechanism by which this virus replicates in infected cells.
Explanation / Answer
1- There are two types of single-stranded virus(ssRNA).
A- Positive-strand RNA virus - This virus is same as mRNA that can be directly translated into protein.
B- Negative-strand RNA virus- This virus has antisense-RNA which need to be converted into positive-strand RNA (mRNA) for translation.
RNA virus replicates inside the host cell by the protein which is encoded by its own genome. This enzyme is called as RNA-dependent RNA polymerase because it uses viral RNA as the template and replicates its genome.
Given that the RNA isolated from the virus is capable of translation in the rabbit reticulocyte cellfree translation system. So virus the genome of the virus is Positive-strand RNA.
2- Generally ssRNA virus translate its whole genome by the single ribosome and the translated protein is cleaved by the virus protein into functional enzymes. These enzymes help in viral replication and viral infection to the other cells as well.
Given that, upon treatment with the protease inhibitor, the virus cannot replicate which means that RNA virus is producing the protein which is being cleaved by the proteases into functional enzyme which helps in the replication of the virus. The virus is dependent on the viral protein for its replication.
So the mechanism of viral replication inside the host cell is as follow:
The virus enters into the host cell and translates its own RNA into the protein. This long protein is cleaved by the viral protease into functional enzymes. These enzymes help in the replication of the viral ssRNA.
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