Hammerhead ribozymes reduce central nervous system (CNS)-derived neuronal nitric oxide synthase messenger RNA in a human cell line

Expression and in vitro cleavage activity of anti-caspase-7 hammerhead ribozymes

AIM: To prepare hammerhead ribozymes against mouse caspase-7 and identify their cleavage activity in vitro, in order to select a ribozyme with specific cleavage activity against mouse caspase-7 as a potential gene therapy for apoptosis-related diseases.

METHODS: Anti-caspase-7 ribozymes targeting sites 333 and 394 (named Rz333 and Rz394) were designed by computer software, and their DNA sequences encoding ribozymes were synthesized. Caspase-7 DNA sequence was acquired by RT-PCR. Ribozymes and caspase-7 DNA obtained by in vitro transcription were cloned into pBSKneo U6’ and pGEM-T vectors, respectively. The cleavage activity of ribozymes against mouse caspase-7 was identified by cleavage experiments in vitro.

RESULTS: Rz333 and Rz394 were designed and their DNA sequences were synthesized respectively. The expression vector of caspase-7 and plasmids containing Rz333 and Rz394 were reconstructed successfully. Ribozymes and caspase-7 mRNA were expressed by in vitro transcription. In vitro cleavage experiment showed that 243-nt and 744-nt segments were produced after caspase-7 mRNA was mixed with Rz333 in equivalent, and the cleavage efficiency was 67.98%. No cleaved segment was observed when caspase-7 mRNA was mixed with Rz394.

CONCLUSION: Rz333 can site-specific cleave mouse caspase-7 mRNA, and it shows a potential for gene therapy of apoptosis-related diseases by down-regulating gene expression of caspase-7.

Therapeutic gene silencing in the nervous system

Progress in the understanding of RNA biology has brought into focus the prospect of using RNA-based therapeutics as a novel approach to treat human disease. In particular, following the discovery of the RNA interference (RNAi) pathway, the emergence of technology based on small interfering RNA (siRNA) now offers a powerful and highly specific tool for therapeutic gene silencing. Many neurological diseases, including neurodegenerative disorders, tumours and retinal disease are likely candidates to benefit from such advances. The challenges ahead will be to identify appropriate disease gene targets and, crucially, to understand the biological parameters that determine safe, precise and effective delivery and function of RNA-based therapeutic molecules within the unique environment of the nervous system.