Question

What are the ways that influenza virus (a) conforms to the principle of genetic economy, (b) manages to have all cistrons expressed, (c) controls the level of gene product that it generated and (d) interacts with and takes over the host gene expression machinery? Explain each of these.

Answer 1

a. Influenza virus has negative stranded (-) RNA genome. So after entry into host it has to produce + strand of RNA for protein synthesis. this virion has 8 RNA segments with a total of about 14,000 nucleotides and codes for 10. To overcome the low number of codons they have evolved genetic economy policy to maximize the utilization of all the codes present in these RNA segments. Through genetic economy virus overcome their small genome to encode multiple proteins. Influenza virus folds their mRNA strand to produce multiple open reading frames. Multiple open reading frames on one strand produces proteins with overlapping sequences.

b. It also manages expression of all its cistrons which is another example of its genetic economy. Given that the influenza A virus only encodes for 10 proteins, it has generated many sophisticated methods of utilizing the host cell’s machinery for its own purposes.

d. Influenza virus uses the host cellular machinery for their own mRNA translation. Influenza virus infection shuts off host protein synthesis, thereby enhancing translation of viral mRNAs .It takes advantage of host cells by processes such as “cap-snatching” and inhibition of cellular mRNA splicing and export.