The hairpin ribozyme has been developed and designed to target and cleave efficiently heterologous RNA sequences in atrans-reaction (1 –3 ). Heterologous RNA cleavage has been carried out, targeting rules defined, systems identified, and very effective in vivo downregulation of gene expression obtained using these design rules (4 ,5 ). This chapter describes the rules and steps necessary for designing the hairpin ribozyme to cleave specific target sequences efficiently.
