Fig. 1.

The scanning model of translation initiation. The scanning model of translation initiation predicts that the 48S preinitiation complex moves along the mRNA in a 5′–3′ direction until it encounters an AUG codon that is in a good context. Many viruses produce proteases that cleave protein components of this complex to inhibit cap-dependent scanning. Thus the cleavage of eIF4G dissociates the ribosome binding ability of the complex from cap recognition. The cleavage of PABP by viral proteases will prevent the interaction of the 5′ and 3′ ends of the mRNA and also reduce the stability of the complex.