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. Ferritin regulation Iron levels in cells are maintained by translation regulation of many proteins involved in iron storage and metabolism. The 5′ UTR has the ability to form a hairpin loop secondary structure (known as the iron response element or IRE) that is recognized by iron-regulatory proteins (IRP1 and IRP2). In low levels of iron, the ORF of the target mRNA is blocked as a result of steric hindrance from the binding of IRP1 and IRP2 to the IRE. When iron is high, then the two iron-regulatory proteins do not bind as strongly and allow proteins to be expressed that have a role in iron concentration control. This function has gained some interest after it was revealed that the translation of amyloid precursor protein may be disrupted due to a single-nucleotide polymorphism to the IRE found in the 5′ UTR of its mRNA, leading to a spontaneous increased risk of Alzheimer's disease. uORFs and reinitiation Another form of translational regulation in eukaryotes comes from unique elements on the 5′ UTR called upstream open reading frames (uORF). These elements are fairly common, occurring in 35–49% of all human genes. A uORF is a coding sequence located in the 5′ UTR located upstream of the coding sequences initiation site. These uORFs contain their own initiation codon, known as an upstream AUG (uAUG). This codon can be scanned for by ribosomes and then translated to create a product, which can regulate the translation of the main protein coding sequence or other uORFs that may exist on the same transcript. The translation of the protein within the main ORF after a uORF sequence has been translated is known as reinitiation. The process of reinitiation is known to reduce the translation of the ORF protein. Control of protein regulation is determined by the distance between the uORF and the first codon in the main ORF. A uORF has been found to increase reinitiation with the longer distance between its uAUG and the start codon of the main ORF, which indicates that the ribosome needs to