A-to-I RNA editing remodels 5'-UTR initiation codons to tune translational output

Area of Science:

• Molecular Biology
• Genetics
• Post-transcriptional Regulation

Background:

• A-to-I RNA editing is a common post-transcriptional modification in eukaryotes.
• This process converts adenosine to inosine, altering codon identity during translation.
• Inosine is read as guanosine, potentially affecting translation initiation.

Purpose of the Study:

• Investigate if A-to-I editing in the 5 -UTR can remodel upstream initiation codons.
• Determine how this remodeling influences downstream translation.
• Explore the impact of editing on upstream open reading frame (uORF)-mediated repression.

Main Methods:

• Utilized luciferase-based reporter systems to assess translation.
• Performed quantitative in vitro and cellular assays to establish initiation codon hierarchy.
• Conducted transcriptome-wide bioinformatic analysis to identify endogenous targets.
• Validated findings using native 5 -UTR sequences.

Main Results:

• AUA-to-AUI editing creates an initiation-competent codon.
• AUG-to-IUG editing significantly reduces initiation and can relieve uORF repression.
• Established initiation hierarchy: AUA < AUI < AUG, with IUG showing low efficiency.
• AUI-mediated upstream initiation had modest, context-dependent effects on downstream translation.

Conclusions:

• A-to-I editing can remodel 5 -UTR initiation codons, impacting translational output.
• Editing-dependent remodeling, especially AUG-to-IUG, can derepress translation.
• Reporter systems provide a framework for studying this phenomenon.
• Further validation at the endogenous protein and native locus level is needed to confirm physiological relevance.