In vitro repair of a defective EGFP transcript and translation into a functional protein

Engineering of hairpin ribozyme variants for RNA recombination and splicing

The hairpin ribozyme is a small, naturally occurring RNA that catalyzes the reversible cleavage of RNA substrates. Among the small endonucleolytic ribozymes, the hairpin ribozyme possesses the unique feature of the internal equilibrium between cleavage and ligation being shifted toward ligation. This allows control of the reaction outcome by structural design: fragments that are strongly bound to the ribozyme are preferentially ligated, whereas substrates that easily dissociate upon cleavage, such that they are not available for religation, are preferentially cleaved. We have made use of this characteristic feature in engineering a number of hairpin ribozyme variants by programmed conformational design that carry out cascades of cleavage and ligation reactions, and as a result mediate more complex RNA processing reactions. Here, we review our work on the engineering of hairpin ribozyme variants for RNA recombination and regular and back-splicing, and discuss the relevance of such activities in early life.

Therapeutic Potential of Ribozymes

Recent advances in RNA engineering during the last two decades have supported the development of RNA-based therapeutics targeting a variety of human diseases. The broad scope of these emerging drugs clearly demonstrates the versatility of RNA. Ribozymes have been seen as promising candidates in this area. However, efficient intracellular application of ribozymes remains challenging, and other strategies appear to have outperformed ribozymes as molecular drugs. Nevertheless, trans-cleaving ribozymes have been applied for specific cleavage of target mRNAs in order to inhibit undesired gene expression. Furthermore, ribozymes have been engineered to allow site-directed RNA sequence alterations, enabling the correction of genetic misinformation at the RNA level. This chapter provides an overview of ribozyme-based strategies, highlighting the promises and pitfalls for potential therapeutic applications.