Structural insights into higher-order natural RNA-only multimers

Area of Science:

• Structural Biology
• RNA Biology
• Biochemistry

Background:

• RNA molecules form complex 3D structures for diverse functions, often independently of proteins.
• Naturally occurring RNA-only complexes are typically monomers or dimers, with higher-order assemblies being less explored.
• Conserved non-coding RNAs like ROOL (rumen-originating, ornate, large) and GOLLD (giant, ornate, lake- and Lactobacillales-derived) possess complex structures, but their high-resolution architectures are unknown.

Purpose of the Study:

• To determine the high-resolution cryo-electron microscopy structures of specific ROOL and GOLLD RNA complexes.
• To elucidate the assembly principles and stabilizing motifs of these higher-order RNA-only structures.
• To expand the understanding of RNA-based architectures and RNA structural biology.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structures.
• High-resolution structural analysis (1.96–2.98 Å) was performed on selected RNA complexes.
• Bioinformatic analysis was employed to identify conserved RNA motifs and assembly principles.

Main Results:

• The study determined the distinct hexameric, decameric, and tetradecameric assemblies of UCC118-Rool RNA, Sag-Golld RNA, and Env38-Golld RNA.
• These higher-order RNA architectures are stabilized by conserved tertiary motifs, including kissing loops and tetraloop-receptor interactions.
• The findings reveal conserved principles governing RNA self-assembly into complex, functional structures.

Conclusions:

• This research elucidates the molecular details of previously uncharacterized higher-order RNA-only assemblies.
• The study expands the known repertoire of RNA-based architectures and highlights the capacity for complex self-assembly in RNA.
• These findings contribute significantly to the field of RNA structural biology and the understanding of RNA's functional versatility.