In vitro selection of RNAs with increased tertiary structure stability

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• RNA molecules fold into complex three-dimensional structures crucial for their function.
• Understanding the relationship between RNA sequence, structure, and stability is fundamental in molecular biology.
• Existing selection methods often rely on RNA activity, potentially overlooking structure-stabilizing elements.

Purpose of the Study:

• To develop and apply an in vitro selection system to identify RNA sequences that enhance tertiary structural stability.
• To investigate RNA structure-function relationships independently of catalytic activity.
• To probe the P4-P6 domain of the Tetrahymena thermophila group I intron for stability-enhancing mutations.

Main Methods:

• In vitro selection using native gel electrophoresis to assess RNA structural stability.
• Employing decreasing concentrations of magnesium chloride (MgCl2) to select for compact RNA structures.
• Iterative selection over 10 rounds on partially randomized P4-P6 RNA domains.
• Sequence analysis of selected RNA variants.

Main Results:

• A novel in vitro selection system was established, successfully isolating RNAs based on structural stability.
• A single base deletion (C209) in the P4 helix was identified, significantly stabilizing the P4-P6 RNA molecule.
• This stabilizing mutation would not have been detected by activity-based selection methods.
• Evidence suggests that secondary structure stabilization can contribute to overall RNA tertiary stability.

Conclusions:

• The developed selection system effectively identifies RNA structural stabilizing elements independent of function.
• The findings highlight the importance of specific sequence modifications, like the C209 deletion, in enhancing RNA structural integrity.
• This method provides a powerful tool for dissecting RNA structure-function relationships by decoupling folding stability from biological activity.