Some viruses, for example, poliovirus, contain a protease that cleaves one of the eukaryotic initiation factors allowing for cap-independent translational initiation of viral RNAs at internal ribosome entry site (IRES). Which of the following factors is the target of these viral proteases?

Question

Quizplus · Accepted Answer

The viral proteases target eIF-4G, which is part of the eIF-4F complex involved in cap-dependent translation initiation. Cleavage of eIF-4G allows the virus to hijack the host's translational machinery for cap-independent translation via IRES.  Poliovirus is a member of the picornavirus family. The RNAs encoded by the viral genome contain internal ribosome entry sites (IRES) that do not require cap structure recognition for translational initiation. The polio virus carries with it a protease that cleaves the eIF-4E binding site on eIF-4G. Cleavage renders eIF-4E incapable of interaction with eIF-4G and as a consequence no active eIF-4F complex forms preventing cap binding and translational initiation of host mRNAs. Due to the presence of the IRES in the viral RNAs, translations take place with the host translational machinery.

Some Viruses, for Example, Poliovirus, Contain a Protease That Cleaves