(Top) The Cripavirus family of type IV IRESs is able to capture free 40S sub- units and engage them on a pre-translocation complex by recruiting 60S. This complex is extremely dynamic, with the 40S alternating between non-rotated and rotated configurations with respect to the 60S subunit. IRESs belonging to this family, exemplified by the CrPV-IRES, recruit elongation factors by mimicking a rotated stated of the ribosome with tRNAS. (Bottom), The Aparavirus family of IRESs follows a similar pathway in order to assemble a pre-translocation complex, however, specific structural components of this family allow for additional contacts with the 60S, limiting the rotational freedom of the 40S. Elongation factors engagement and thus effective ribosome hijacking is accomplished by mimicking a ribosome state with tRNAs in hybrid configurations. 