Selection of efficient cleavage sites in target RNAs by using a ribozyme expression library

Area of Science:

• Molecular Biology
• Gene Regulation
• Biotechnology

Background:

• Antisense mechanisms, particularly ribozymes, offer a potent method for studying gene function by inactivating gene expression.
• Developing efficient ribozyme-based gene silencing requires strategies for expression, target site selection, and isolation of active ribozymes.

Purpose of the Study:

• To design a versatile strategy for expressing ribozymes and selecting specific cleavage sites on target RNAs.
• To isolate functional ribozymes from a library for gene inactivation applications.
• To demonstrate the efficacy of this strategy using human growth hormone mRNA as a model.

Main Methods:

• Designed an expression cassette for ribozyme genes utilizing adenovirus-associated RNA, polymerase III, or T7 phage transcription.
• Generated a library of ribozyme genes with flanking random sequences around a hammerhead motif.
• Selected and identified ribozymes targeting specific sites within human growth hormone mRNA and nuclear RNA.
• Validated ribozyme efficacy in a cellular assay for gene repression.

Main Results:

• Successfully designed and selected ribozymes targeting seven sites within human growth hormone mRNA/nuclear RNA.
• Sequencing confirmed predicted cleavage sites and identified diverse ribozyme variants.
• A specific ribozyme variant achieved over 99% inhibition of growth hormone synthesis.
• The most effective ribozyme possessed the shortest complementarity stretch to the target RNA.

Conclusions:

• The developed strategy is effective for selecting target sites and isolating corresponding ribozymes for any mRNA of interest.
• This approach provides a powerful tool for gene function studies through targeted gene silencing.
• The findings highlight the potential of ribozymes in precise gene expression control.