Figure 3. GAr suppresses antigen presentation by targeting the mRNA translation initiation process.

A) Cartoon illustrating the c-myc Internal Ribosomal Entry Sites (IRES) constructs. IRESs offer alternative cap-independent mechanisms of mRNA translation initiation. B) Autoradiograph of ³⁵S-methionine metabolic pulse labelling. Insertion of the c-myc IRES in the 5′UTR of the GAr-Ova mRNA (c-myc-GAr-Ova) restores translation in H1299 cells but does not affect translation when inserted in the 5′UTR of Ova alone (left panel). Western blot shows that the effect of the c-myc IRES is restricted to the GAr alone (right panel). C) Autoradiograph of a 30 minutes ³⁵S-metabolic pulse label experiment of the endogenous protein (actin) and the exogenous GFP protein in H1299 cells in the presence of the c-myc IRES and the GAr constructs. D) The c-myc IRES stimulates SL8 presentation in the context of the GAr from the main open reading frame as well as cryptic translated products (see Fig. 2A). Data are representative of three or more independent experiments plus SD.