“…A cap-independent mechanism involving an internal ribosome entry site (IRES) has been identified in picornavirus messengers, which are uncapped and present a long 5Ј UTR (20,41). The presence of an IRES has also been reported for many viral (cardiovirus, rhinovirus, and aphthovirus) (21) and some cellular human (Bip, FGF-2, IGF-II, eIF4G, PDGF, and c-Myc) (2,13,33,37,50,51,53) messengers and in Drosophila antennapedia and ultrabithorax mRNAs (39,59).…”