Abstract: Two ribozymes, ribozyme N-1 and ribozyme N-2, were chemically synthesized, which are designed for blocking the expression of polyhedrin gene of Autographa californica nuclear polyhedrosis virus (AcNPV). In vitro, they are able to specifically and effectively cleave the target mRNA fragments which were transcripted from part of polyhedrin gene. Results showed that the percentage of cleavage was increased when the temperature or time of incubation was increased or higher concentration of ribozyme was used. Ca²⁺, Mn²⁺ can substitute Mg²⁺ as the neces sary divalent cation for the cleavage reaction by ribozyme.

Key words: Autographa californica——NPV——ribozyme