RNA G-quadruplex structure and function in plants

RNA folds into fascinating structures that govern almost every biological process. One distinctive structural motif, the G-quadruplex, is of particular interest given its potential relevance in regulation of biological processes. Our research describes a stable G-quadruplex structure within the 5’ UTR of Arabidopsis thaliana ATR mRNA that can inhibit translation, offering new insights into translational regulation in plants.

HFSP Program Grant holders Philip Bevilacqua and Sarah Assmann and colleagues
authored on Tue, 12 May 2015

Understanding RNA structure helps to reveal RNA’s biological functions. G-Quadruplex Structures (GQS) are nucleic acid motifs that are formed by G-quartets, consisting of sets of four interacting guanines that are stabilized by potassium ions (K+) (figure A).  These structures have been demonstrated to be of biological significance in mammalian systems. The formation and function of GQSs in plants is largely unexplored.

Figure: Model for RNA GQS-mediated translational regulation in Arabidopsis thaliana ATR mRNA. A) Structure of a G-quartet. B) Presence of a stable RNA GQS in the 5’ UTR of A. thaliana ATR mRNA inhibits translation of a reporter gene, suggesting a translational repressor role in vivo.

Using a combination of biophysical and biochemical assays, we structurally characterized a stable GQS in the 5’ UTR of Arabidopsis thaliana ATR mRNA, which encodes a protein kinase that is activated upon DNA damage and repair.  Using a reporter gene assay, we demonstrated that this GQS inhibits translation in living plant cells suggesting a repressor role in translational regulation (Figure B). We also identified GQSs in ATR homologs of other plant species including closely related plant species such as Arabidopsis lyrata (lyre-leaved rock-cress), and more evolutionarily distant species such as Oryza sativa (rice), implying that GQS-mediated gene regulation may be prevalent and of functional importance in the plant kingdom.

Our study represents the first experimental demonstration of formation and function of a GQS in any plant species. These findings provide new insights towards understanding the roles of GQSs in plants and other organisms.

Reference

A stable RNA G-quadruplex within the 5'-UTR of Arabidopsis thaliana ATR mRNA inhibits translation. Kwok CK, Ding Y, Shahid S, Assmann SM, Bevilacqua PC. (2015). Biochem J. 467, 91-102.

Pubmed link