The 5S rRNA loop E: chemical probing and phylogenetic data versus crystal structure

Area of Science:

• Structural Biology
• Computational Biology
• Molecular Biology

Background:

• Folded RNA molecules utilize noncanonical base pairs in internal and junction loops.
• High-resolution RNA structures are crucial for understanding and predicting RNA 3D architecture.
• The crystal structure of bacterial 5S ribosomal RNA Loop E provides new insights into noncanonical pairings.

Purpose of the Study:

• To improve RNA structure prediction accuracy using chemical probing and phylogenetic analysis.
• To interpret chemical probing data in the context of known RNA structures.
• To identify geometrically compatible alternative base pairings using phylogenetic data.

Main Methods:

• Analysis of existing chemical probing data for RNA structure.
• High-resolution crystal structure analysis of bacterial 5S ribosomal RNA Loop E.
• Phylogenetic analysis of conserved RNA sequences to infer base pairing possibilities.

Main Results:

• The study identified two new purine-purine and one new GU base pairing in Loop E.
• Phylogenetic analysis revealed isosteric pairings (A/A, A/C, A/U, C/A, C/C, C/U) compatible with sheared A/G pairs.
• Identified A/A and A/C pairings as isosteric with G/U and G/G bifurcated pairings.
• Non-Watson-Crick pairs can be characterized by a phylogenetic signature of isosteric variations.
• Concerted base pair changes suggest transitions between distinct structural motifs.

Conclusions:

• Chemical probing and phylogenetic analysis can be combined to enhance RNA structure prediction.
• The identified phylogenetic signatures offer a dictionary of isosterically compatible base pairings.
• Covariation analysis highlights potential dynamic structural transitions within RNA loops.