Dual role of 3' UTR length in modulating translation termination efficiency.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The 3' untranslated region (UTR) of messenger RNAs (mRNAs) regulates crucial post-transcriptional events like stability and translation.
• Unusual genetic codes and short 3' UTRs in some protozoa suggest a link between 3' UTR structure and translation termination efficiency.

Purpose of the Study:

• To investigate how 3' UTR length and secondary structure influence translation termination efficiency across species.
• To explore the role of 3' UTRs in alternative genetic codes and stop codon reassignment.

Main Methods:

• Analysis of translation termination efficiency with varying 3' UTR lengths and structures.
• Biochemical assays using purified pre-termination complexes.
• Investigating stop codon reassignment mechanisms.

Main Results:

• Shortened structured 3' UTRs provide a translational advantage for mRNAs with UAA stop codons.
• 3' UTR secondary structures enhance termination rates by promoting poly(A)-binding protein (PABP) and eukaryotic release factor 3a (eRF3a) proximity to the ribosome.
• Termination rates at UGA stop codons are sensitive to 3' UTR length with different release factors.

Conclusions:

• 3' UTR length is a critical cis-regulatory factor controlling translation termination.
• A dual mechanism exists: long, structured 3' UTRs can hinder stop codon recognition but also facilitate release factor recruitment via eRF3a-PABP interactions.