Ribozyme-mediated cleavage of an HIV-1 gag RNA: the effects of nontargeted sequences and secondary structure on ribozyme cleavage activity.

Catalytic antisense RNAs, or ribozymes, have great potential as inhibitors of gene expression and as antiviral therapeutic agents. The major advantage of ribozymes versus standard antisense RNAs is their catalytic capability, enabling these RNAs to cleave multiple substrates. We have been investigating the antiviral activity of ribozymes targeted to the HIV-1 genome. The successful use of these antisense agents in an intracellular milieu requires stabilization of the ribozymes by flanking, non-base-pairing sequences, or some modification of the sugar-phosphate backbone. We describe a systematic investigation of the effects of flanking, non-base-pairing sequences on the catalytic activity of an anti-HIV-1 gag ribozyme embedded in radically different transcripts. Amazingly, these complex ribozyme-containing transcripts maintain substantial catalytic activity. Finally, we describe a bacterial gene fusion system that has potential for the large scale production of catalytically active ribozymes.