Untranslated region

The untranslated regions of mRNA became a subject of study as early as the late 1970s, after the first mRNA molecule was fully sequenced. In 1978, the 5' UTR of the human gamma-globin mRNA was fully sequenced. In 1980, a study was conducted on the 3' UTR of the duplicated human alpha-globin genes. == Evolution ==

The untranslated region is seen in prokaryotes and eukaryotes, although the length and composition may vary. In prokaryotes, the 5' UTR is typically between 3 and 10 nucleotides long. In eukaryotes, the 5' UTR can be hundreds to thousands of nucleotides long. This is consistent with the higher complexity of the genomes of eukaryotes compared to prokaryotes. The 3' UTR varies in length as well. The poly-A tail is essential for keeping the mRNA from being degraded. Although there is variation in lengths of both the 5' and 3' UTR, it has been seen that the 5' UTR length is more highly conserved in evolution than the 3' UTR length. Prokaryotes The 5' UTR of prokaryotes consists of the Shine–Dalgarno sequence (5'-AGGAGGU-3'). This sequence is found 3-10 base pairs upstream from the initiation codon, the start site of the translation into protein. Eukaryotes The 5' UTR of eukaryotes is more complex than that of prokaryotes. It contains a Kozak consensus sequence (ACCAUGG) including the initiation codon (AUG), the start site of the translation into protein. == Links to disease ==

The importance of these untranslated regions of mRNA is just beginning to be understood. Various medical studies are being conducted that have found connections between mutations in untranslated regions and increased risk for developing a particular disease, such as cancer. For example, associations between polymorphisms in the HLA-G 3′UTR region and development of colorectal cancer have been discovered. Single Nucleotide Polymorphisms in the 3' UTR of another gene have also been associated with susceptibility to preterm birth. Mutations in the 3' UTR of the APP gene are related to development of cerebral amyloid angiopathy. == Further study ==

Through the recent study of untranslated regions, general information has been gathered about the nature and function of these elements. However, there is still much that is unknown about these regions of mRNA. Since the regulation of gene expression is critical in the proper function of cells, this is an area of study that needs to be investigated further. It is important to consider that mutations in 3' untranslated regions have the potential to alter the expression of several genes that may appear unrelated. We are only beginning to understand the links between proper untranslated region function, and disease states of cells. ==See also==