Practice question

IRES elements circumvent the requirement for the 7-methylguanosine cap and the eIF4E component of eIF4F complex. Instead of 5' end scanning, the IRES tertiary fold creates a landing pad mimicking initiator tRNA or eIF4G binding surfaces, allowing direct 40S and eIF3 recruitment near the initiation codon without scanning from the terminus. This independence permits protein synthesis when viral proteases cleave eIF4G or when cellular stress depletes cap-binding capacity. Poly(A) tail, functional ribosomes, initiator tRNA, and elongation factors remain essential for translation, yet the cap structure becomes dispensable for internal entry driven initiation pathways.