mRNA Untranslated Regions (UTRs)


Eukaryotic messenger ribonucleic acids (mRNAs) possess a tripartite structure that comprises a 5′ untranslated region, a coding region made up of the amino acid coding triplet codons and a 3′ untranslated region. During nuclear maturation of primary transcripts, both ends of mRNA are post‐transcriptionally modified through the addition of a 7‐methyl‐guanosine cap structure at the 5′ end and a polyadenosine tail at the 3′ end. mRNA untranslated regions – UTRs – are involved in the post‐transcriptional regulation of gene expression by modulating the mRNA stability, nucleocytoplasm transport, subcellular localisation and translation efficiency, thus allowing a fine control of the protein product. This regulatory activity is mediated by ‐acting oligonucleotide elements that interact with binding proteins and noncoding RNAs (micro ribonucleic acids – miRNAs and long noncoding ribonucleic acids – lncRNAs) through a combination of primary and secondary structures.

Key Concepts

  • UTRs are involved in the post‐transcriptional regulation of gene expression.
  • UTRs regulate mRNA stability, nucleocytoplasm transport, subcellular localisation and translation efficiency.
  • Alternative splicing can result in mRNAs encoding the same protein under the control of different UTRs.
  • UTRs regulate translation during physiological stress conditions.
  • UTRs are miRNA targets to repress translation or destabilise mRNA.

Keywords: post‐transcriptional regulation; RNA‐binding proteins; translation; mRNA stability; mRNA localisation; miRNA target

Figure 1. Examples of untranslated (UTR) elements with a known secondary structure: (a) human basic fibroblast growth factor (GenBank accession number J04513) IRES element; (b) IRE structure of human transferrin (GenBank accession number M11507); (c) selenocysteine insertion sequence from human SelZ mRNA (GenBank accession number AF166127). Nucleotides that are conserved among the same elements from different transcripts are highlighted by filled circles.
Figure 2. Structure of a eukaryotic mRNA (messenger ribonucleic acid) that depicts some post‐transcriptional regulatory elements. Factors influencing message stability include uAUGs, uORFs, antisense noncoding ribonucleic acids (ncRNAs) and elements embedded in both the 5′ and 3′ UTRs. Modulation of translation may be mediated by the secondary structure of the 5′ UTR, uAUGs or uORFs, as well as by protein‐mediated poly(A) tail interaction with the 7 mG cap. Subcellular localisation of mRNA is often mediated by miRNA elements located in the 3′ UTR.


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Mignone, Flavio, and Pesole, Graziano(Jan 2018) mRNA Untranslated Regions (UTRs). In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0005009.pub3]