Efficacy of Hammerhead Ribozymes Targeting α-Lactalbumin Transcripts: Experiments in Cells and Transgenic Mice

Abstract

Ribozymes are small RNA molecules capable of specific catalytic cleavage of RNA (Uhlenbeck 1987). In the natural state, they exist as several different motifs, and catalyze RNA cleavage and RNA splicing reactions (Symons 1989). For the hammerhead and hairpin ribozyme motifs identified in the (+) and (−) strands of the satellite RNA of tobacco ringspot virus, the cleavage reactions are intramolecular. However, dissection of the catalytic motifs has enabled the division of these molecules into a substrate that possesses a GUX tri-nucleotide recognition sequence (GUA, GUU, CUC, UUC, and sometimes AUC in the case of the hammerhead ribozyme), and an enzyme moiety. The later is a chimeric molecule composed of the highly conserved catalytic domain and two flanking sequences complementary to the substrate that governs cleavage specificity (Haseloff and Gerlach 1988). Such ribozymes can perform an enzymatic reaction in which a target substrate is cleaved and the ribozyme itself is not altered during the reaction. Ribozyme-mediated cleavage in vitro was first demonstrated by Uhlenbeck (1987) and subsequently by Haseloff and Gerlach (1988).