4. Pretend you are a researcher that has just Gray = Wild-type Virus X Black Pro

Question

4. Pretend you are a researcher that has just Gray = Wild-type Virus X Black Protein Y mutant constructed a mutant virus with a deletion in the gene encoding protein "Y" of the virus. You discover that cells infected with the mutant virus now display significantly higher levels of surface MHC class I (refer to the figure to the right). In other words, when protein Y is absent, MHC class I levels at the surface of the cell increase. Provide one possible mechanism that would explain the observed results. Design one experiment to examine your hypothesis. What would you test for and what would you predict to be the outcome of your experiment if your hypothesis is correct? [6 pts.] Surface levels of MHC classI 2

Explanation / Answer

Part 1-One possible mechanism that can explaing the observed results is that,many viruses have evolved proteins that interfere with antigen presentation by MHC class 1.These viruses have various strategies to inhibit the MHC class 1 pathway.Therefore,we can conclude that,the protein Y is one of the proteins that interferes with antigen presentation by MHC class 1.So,the cells infected with Mutant Virus i.e. the virus that cannot produce protein Y shows higher level of surface MHC class 1 in comparision to the cells exposed to Wild type virus.

Part 2-MHC class 1 antigen presentation plays an important role in alerting the immune system of cells of Viral genome,So,we can take Wild type virus and Mutant virus whose genome is tagged with radioactive Phosphorus and expose them to cell cultures A and B respectively.The cell culture A where we can observe radioactive Phosphorus indicates that protein Y was present(i.e the cells were exposed to wild type virus which has the gene encoding for protein Y which deactivated the MHC class 1 pathways).

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