Substrate determinants for RNA editing and editing complex interactions at a site for full-round U insertion.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Multisubunit RNA editing complexes catalyze uridylate insertion/deletion RNA editing guided by guide RNAs (gRNAs).
• RNA editing in trypanosome mitochondria is transcript-specific and developmentally controlled, but the molecular mechanisms of substrate specificity are not fully understood.

Purpose of the Study:

• To define functional determinants for full-round insertion and editing complex interactions at editing site 2 (ES2) using a minimal A6 pre-mRNA/gRNA substrate.
• To investigate the role of secondary structure and specific ribose moieties in substrate recognition and editing complex activity.

Main Methods:

• Utilized a minimal A6 pre-mRNA/gRNA substrate to study RNA editing at editing site 2 (ES2).
• Employed site-specific ribose 2' substitutions to probe the function of hydroxyl groups.
• Investigated editing complex cross-linking interactions at insertion and deletion editing sites (ES).

Main Results:

• Substrate recognition around the internal loop is sequence-independent, with artificial duplexes being functional.
• Demonstrated editing complex contacts at an insertion editing site (ES) for the first time.
• Identified specific 2'-hydroxyl groups in gRNA loop and flanking helices that stimulate pre-mRNA cleavage and editing complex interactions.
• A single 2'-hydroxyl at ES2 is essential for cleavage but not for editing complex cross-linking.

Conclusions:

• RNA secondary structure and specific ribose interactions are crucial for substrate recognition and editing complex activity.
• Provided the first functional association of specific pre-mRNA and gRNA riboses with endonuclease cleavage and cross-linking activities.
• Observed conserved and stable cross-linking interactions at editing sites, with transient contacts in non-edited transcripts.