Untranslated region

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As untranslated region (also untranslated region - English region untranslated abbreviated UTR ) is in the molecular biology an edge region of the mRNA called who did not for the actual protein coded.

An mRNA codes for a specific protein when, during translation by ribosomes, the amino acid sequence of its polypeptide chain is synthesized from the base sequence presented in the transcript . However, the nucleotide sequence of an mRNA usually also contains regions that are not translated in the process.

In the mRNA of prokaryotes , these are two transcribed but untranslated border areas of an mRNA at their ends: at the 5 'end a region as a 5' UTR , and at the 3 'end a region as a 3' UTR . The 5'-UTR extends from the transcription start point to before the translation start codon , the 3'-UTR begins behind the translation stop codon and extends to the transcription end point.

These two regions are also found in the mRNA of eukaryotic cells, whereby the 5'-UTR can be a few hundred nucleotides long, the 3'-UTR even over a thousand. In addition to these, an mRNA in eukaryotes still has the 5 'cap in front of it and the poly-A tail behind it as (non-transcribed) untranslated areas (see figure).

Schematic representation of a human mRNA. On average, a 5 'UTR is around 170 nucleotides and a 3' UTR around 700 nucleotides long.

5′-UTR

The 5'-UTR ( 5 'untranslated region , that is 5-prime UTR ; English five prime untranslated region ), as a leader sequence referred to, is a specific region of the mRNA transcript - or also that DNA -Abschnitts which for encodes this mRNA. This region begins at the transcription start point (position +1) and ends before the translation start codon of the protein-coding region. Usually this sequence contains a ribosomal binding site (RBS), also known in bacteria as the Shine-Dalgarno sequence .

Various regulatory sequences can lie in the 5′-UTR:

  • Binding sites for proteins that can influence the stability of the mRNA or its translation.
  • Regulatory elements that work independently of proteins, such as riboswitches .
  • Sequences that initiate translation initiation.

3′-UTR

The 3'-UTR ( 3 'untranslated area , i.e. 3-stroke UTR ; English three prime untranslated region ) is a region of the mRNA transcript that adjoins the area coding for protein. It begins behind the stop codon and extends - in eukaryotic cells - to the start of polyadenylation .

Various regulatory sequences can be found in the 3′-UTR:

Individual evidence

  1. ↑ Lodish et al. : Molecular Cell Biology, 5th edition.
  2. ↑ BM Pickering, AE Willis: The implications of structured 5 'untranslated regions on translation and disease. In: Semin Cell Dev Biol. Vol. 16, 2004, pp. 39-47, PMID 15659338 .
  3. ↑ B. Mazumder, et al. : Translational control by the 3'-UTR: the ends specify the means. In: Trends Biochem. Sci. Vol. 28, 2003, pp. 91-98. PMID 12575997 doi: 10.1016 / S0968-0004 (03) 00002-1

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