m RNA Untranslated Regions ( UTRs )

Abstract 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. Untranslated regions are involved in the post‐transcriptional regulation of gene expression by modulating mRNA stability, nucleo‐cytoplasm transport, subcellular localisation and translation efficiency thus allowing a fine control of the protein product. This regulatory activity is mediated by cis ‐acting oligonucleotide elements that interact with binding proteins and noncoding RNAs 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, nucleo‐cytoplasm transport, subcellular localisation and translation efficiency. Alternative splicing can result in mRNAs encoding the same protein under the control of different UTRs.