Five prime untranslated region
5′ untranslated region | |
---|---|
transcript in eukaryotic organism (specifically humans) | |
Identifiers | |
MeSH | D020121 |
Anatomical terminology] |
The 5′ untranslated region (also known as 5′ UTR, leader sequence, transcript leader, or leader RNA) is the region of a
The 5′ UTR has been found to interact with proteins relating to metabolism, and proteins translate sequences[clarification needed] within the 5′ UTR. In addition, this region has been involved in transcription regulation, such as the sex-lethal gene in Drosophila.[1] Regulatory elements within 5′ UTRs have also been linked to mRNA export.[2]
General structure
Length
The 5′ UTR begins at the
The 5′ UTR can also be completely missing, in the case of leaderless mRNAs.
Elements
The elements of a eukaryotic and prokaryotic 5′ UTR differ greatly. The prokaryotic 5′ UTR contains a
Secondary structure
As the 5′ UTR has high
Role in translational regulation
Prokaryotes
In
Initiation in Archaea is less understood. SD sequences are much rarer, and the initiation factors have more in common with eukaryotic ones. There is no homolog of bacterial IF3.[10] Some mRNAs are leaderless.[11]
In both domains, genes without Shine–Dalgarno sequences are also translated in a less understood manner. A requirement seems to be a lack of secondary structure near the initiation codon.[12]
Eukaryotes
Pre-initiation complex regulation
The regulation of translation in eukaryotes is more complex than in prokaryotes. Initially, the
Closed-loop regulation
Another important regulator of translation is the interaction between 3′ UTR and the 5′ UTR.
The closed-loop structure inhibits translation. This has been observed in
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
uORFs and reinitiation
Another form of translational regulation in eukaryotes comes from unique elements on the 5′ UTR called upstream
The translation of the protein within the main ORF after a uORF sequence has been translated is known as reinitiation.
Other mechanisms
In addition to reinitiation, uORFs contribute to translation initiation based on:
- The nucleotides of an uORF may code for a codon that leads to a highly structured mRNA, causing the ribosome to stall.[19]
- cis- and trans- regulation on translation of the main protein coding sequence.[19]
- Interactions with IRES sites.[19]
Internal ribosome entry sites and viruses
Role in transcriptional regulation
msl-2 transcript
Transcription of the msl-2 transcript is regulated by multiple binding sites for fly Sxl at the 5′ UTR.[1] In particular, these poly-uracil sites are located close to a small intron that is spliced in males, but kept in females through splicing inhibition. This splicing inhibition is maintained by Sxl.[1] When present, Sxl will repress the translation of msl2 by increasing translation of a start codon located in a uORF in the 5′ UTR (see above for more information on uORFs). Also, Sxl outcompetes TIA-1 to a poly(U) region and prevents snRNP (a step in alternative splicing) recruitment to the 5′ splice site.[1]
See also
- Three prime untranslated region
- UORF
- Iron-responsive element-binding protein
- Iron response element
- Trans-splicing
- UTRdb
References
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