Fig. 3.

Cap-snatching mechanisms. The endonuclease captures the cellular mRNA from the cell (blue) and snatches (cleaves and transfers) the cap structure followed by seven to eleven bases to the polymerase to start the viral mRNA (green). The residual cellular RNA serves as decoy for the innate immunity. The RNAs capped by viral enzymes are undistinguishable from cellular mRNA and can thus be translated into proteins by the host-cell ribosomal machinery. Below the schematic are listed examples of viruses that acquire their cap structures using the cap snatching mechanism.