 IRESs are often used by viruses as a means to ensure that viral translation is active when host translation is inhibited.These mechanisms of host translation inhibition are varied, and can be initiated by both virus and host, depending on the type of virus.However, in the case of most picornaviruses, such as poliovirus, this is accomplished by viral proteolytic cleavage of eIF4G so that it cannot interact with the 5'cap binding protein eIF4E.