Translational control is an important mechanism to ensure mRNA transcripts are accurately translated into functional protein products.
eIF4A, eIF4E, and eIF4G form the cap-binding complex at the 5’ terminal of the mRNA. eIF4A removes structures from the mRNA, with a helicase activity. eIF4E recruits ribosomes, initiating translation. eIF4G interacts with the poly(A) binding protein, linking the 5’ cap structure to the 3’ UTR. This forms a sort-of circular mRNA molecule, enabling ribosomes to end translation near the start site (leading to an increase in transcription).
PABP, poly(A) binding protein, binds to the 3’ UTR multiple times, providing a binding site for eIF4G. By having a circular molecule, ribosomes end translation near the start site, increasing protein yield. Breaking this circular structure, such as with 4EBP, can be used to downregulate transcription.