Dynamic extended folding: modeling the RNA secondary structures during co-transcriptional folding

Viroid research and its significance for RNA technology and basic biochemistry

Viroids were described 47 years ago as the smallest RNA molecules capable of infecting plants and autonomously self-replicating without an encoded protein. Work on viroids initiated the development of a number of innovative methods. Novel chromatographic and gelelectrophoretic methods were developed for the purification and characterization of viroids; these methods were later used in molecular biology, gene technology and in prion research. Theoretical and experimental studies of RNA folding demonstrated the general biological importance of metastable structures, and nuclear magnetic resonance spectroscopy of viroid RNA showed the partially covalent nature of hydrogen bonds in biological macromolecules. RNA biochemistry and molecular biology profited from viroid research, such as in the detection of RNA as template of DNA-dependent polymerases and in mechanisms of gene silencing. Viroids, the first circular RNA detected in nature, are important for studies on the much wider spectrum of circular RNAs and other non-coding RNAs.

A folding "framework structure" of Tetrahymena group I intron

We have published the dynamic extended folding (DEF) method, which is a RNA secondary structure prediction approach-to simulate the in vivo RNA co-transcriptional folding process. In order to verify the reliability of the method, we selected the X-ray-determined Tetrahymena group I intron as a sample to construct the framework of its folding secondary structure. Our prediction coincides well with the secondary structure predicted by T.R. Cech and the X-ray diffraction crystal structure determined by Lehnert V. Our results show that the DEF framework structure of Tetrahymena group I intron reflects its function sites in a concise and straightforward manner, and the scope of the simulation was expanded.