The regulation of translation in eukaryotes is more complex than in prokaryotes. Initially, the eIF4F complex is recruited to the 5′ cap, which in turn recruits the ribosomal complex to the 5′ UTR. Both eIF4E and eIF4G bind the 5′ UTR, which limits the rate at which translational initiation can occur. However, this is not the only regulatory step of translation that involves the 5′ UTR.
RNA-binding proteins sometimes serve to prevent the pre-initiation complex from forming. An example is regulation of the msl2 gene. The protein SXL attaches to an intron segment located within the 5′ UTR segment of the primary transcript, which leads to the inclusion of the intron after processing. This sequence allows the recruitment of proteins that bind simultaneously to both the 5′ and 3′ UTR, not allowing translation proteins to assemble. However, it has also been noted that SXL can also repress translation of RNAs that do not contain a poly(A) tail, or more generally, 3′ UTR.