The Membrane Protein of Severe Acute Respiratory Syndrome Coronavirus Functions as a Novel Cytosolic Pathogen-Associated Molecular Pattern To Promote Beta Interferon Induction via a Toll-Like-Receptor-Related TRAF3-Independent Mechanism

Wang, Yi; Liu, Li

To directly compare M-and M-stop-induced IFN-␤ production levels, the increased doses of either M or M-stop constructs were cotransfected with IFN-␤ luciferase reporter into HEK293T cells. Figure 5D clearly demonstrates that M-stop does not induce IFN-␤ production, indicating that protein translation is necessary for M-induced IFN-␤ production. To confirm this result further, the chemical inhibitor cycloheximide (CHX) was used to block the protein biosynthesis in transfected HEK293T cells. Figure 5E shows that addition of CHX significantly inhibited and completely blocked M protein synthesis at 5 g/ml and above 20 g/ ml, respectively, which are directly correlated with the marked reduction and complete inhibition in IFN-␤ expression, indicating that M protein may function as a PAMP to induce IFN-␤ production.