Another important regulator of translation is the interaction between 3′ UTR and the 5′ UTR.
The closed-loop structure inhibits translation. This has been observed in Xenopus laevis, in which eIF4E bound to the 5′ cap interacts with Maskin bound to CPEB on the 3′ UTR, creating translationally inactive transcripts. This translational inhibition is lifted once CPEB is phosphorylated, displacing the Maskin binding site, allowing for the polymerization of the PolyA tail, which can recruit the translational machinery by means of PABP. However, it is important to note that this mechanism has been under great scrutiny.