RNA Structural Motifs

Chemically, ribonucleic acid (RNA) is a close cousin of deoxyribonucleic acid (DNA). RNA is, however, involved in a wide range of cellular activities (e.g. translating genetic information, serving as a structural scaffold, catalysing biological reactions) that often require the molecule to fold into a specific structure in order to perform its targeted function. Structurally and functionally it is therefore more closely related to proteins than to DNA. An RNA structural motif is defined as a collection of residues that fold into a stable three-dimensional (3D) structure and which can be found in naturally occurring RNAs in unexpected abundance. Owing to the fact that stable 3D structures are associated with RNA structural motifs, these motifs often served as nucleation sites for RNA folding. Key Concepts: RNA motifs can help stabilise a global RNA structure, as well as guide the RNA folding process. Hairpins are essential in constituting RNA tertiary architecture and in forming binding sites for other molecules. Owing to variation of the lengths of loops and stems, as well as the types of interactions between them, pseudoknots represent a structurally diverse group. Triloops and tetraloops with specific sequences are stable and frequently observed hairpin loops. Self-folding RNA structures, including the adenosine platform, ribose zipper, bulge–helix–bulge motif and G-bulge motif, can provide the nucleation sites for RNA folding. Keywords: helix and loop; hairpin; junction; kissing loop; pseudoknot; RNA folding; RNA self-folding structure