Hammerhead ribozyme cleavage of hamster prion pre-mRNA in complex cell-free model systems

The cleavage properties of a trans-acting hammerhead ribozyme targeted 51 bases upstream of the putative splicing branch point in the hamster prion pre-mRNA intron were investigated in cell-free model systems in vitro. The specificity of cleavage was demonstrated by the inability of this ribozyme to cleave a non-homologous synthetic message encoding part of the beta amyloid peptide precursor, beta APP, and by the inability of the prion pre-mRNA to be cleaved by a ribozyme targeted to beta amyloid peptide precursor mRNA. Also, the addition of total RNA isolated from rat brain had only a minimal effect on the cleavage of the prion substrate pre-mRNA by the ribozyme. Finally neither the presence of 100 ng of nuclear or cytoplasmic proteins were found to affect the rate of cleavage in vitro.