PEPTIDE NUCLEIC-ACID (PNA) IS CAPABLE OF ENHANCING HAMMERHEAD RIBOZYME ACTIVITY WITH LONG BUT NOT WITH SHORT RNA SUBSTRATES

Long RNA substrates are inefficiently cleaved by hammerhead ribozymes in trans. Oligonucleotide facilitators capable of affecting the ribozy me activity by interacting with the substrates at the termini of the r ibozyme provide a possibility to improve ribozyme mediated cleavage of long RNA substrates. We have examined the effect of PNA as facilitato r in vitro in order to test if even artificial compounds have facilita ting potential, Effects of 12mer PNA- (peptide nucleic acid), RNA- and DNA-facilitators of identical sequence were measured with three subst rates containing either 942, 452 or 39 nucleotides, The PNA facilitato r enhances the ribozyme activity with both, the 942mer and the 452mer substrate to a slightly smaller extent than RNA and DNA facilitators. This effect was observed up to PNA facilitator:substrate ratios of 200 :1, The enhancement becomes smaller as the PNA facilitator:substrate r atio exceeds 200:1, With the 39mer substrate, the PNA facilitator decr eases the ribozyme activity by more than 100-fold, even at PNA facilit ator:substrate ratios of 1:1. Although with long substrates the effect of the PNA facilitator is slightly smaller than the effect of identic al RNA or DNA facilitators, PNA may be a more practical choice for pot ential applications in vivo because PNA is much more resistant to degr adation tay cellular enzymes.