''Hairpin'' and ''Hammerhead'' ribozymes directed towards the Mumps virus nucleocapsid RNA: Specific cleavage of a small synthetic RNA substrate and full-length mRNA

In an attempt to develop efficient antiviral agents against Mumps virus, we designed ribozymes targeting the nucleocapsid (NP) mRNA. Transacting catalytic RNAs of the hammerhead and hairpin types were synthesized; they contained specific motifs, shared similar flanking regions and were directed against a 5'GUC3' target immediately downstream to the initiation codon of NP mRNA. Both ribozymes were first assayed on a synthetic 16 bases target RNA and found to catalytically and efficiently cleave the substrate in a sequence specific way. No cleavage, however, occurred when mutated forms of the ribozymes were used. In addition, both ribozyme types, when tested on the full length NP mRNA, were also able to cleave the substrate although turnover could not be demonstrated. As a rule, the hammerhead ribozyme proved more efficient than its hairpin counterpart, as well on the synthetic RNA substrate as on the full length NP mRNA target.