Development of Peptide Nucleic Acid Based Artificial Ribonucleases, PNAzymes

Abstract: Since mRNA plays such a vital role in the transfer of genetic code from DNA to proteins, approaches involving interference with mRNA are of great interest for use in therapeutics. Amongst these, peptide nucleic acid based nuclease systems (PNAzymes) are being developed for in vivo gene silencing in future. The PNAzymes hybridize to the RNA, bringing a catalytic group to the phosphodiester bond and inducing the cleavage. A study on PNAzymes has shownhigh site- and sequence-specificity in the cleavage of target RNA sequences and this also occurs at a faster rate than previously reported oligonucleotide-based artificial ribonucleases. However, anincrease in rate is still needed for gene silencing applications to be useful therapeutically.This previous study used 2,9-dimethyl-5-aminophenanthroline conjugated to a PNA strand in order to cleave target RNA. The aim of this project was to synthesize 2,5,9-triaminophenanthroline with tert-butyloxycarbonyl groups (Boc-groups) in the 2- and 9-positions, activate the amino group in the 5-position with phenyl chloroformate and conjugate it to PNA and then compare the cleavage efficiency of the resulting PNAzyme with those carrying the 5-aminophenanthroline and 2,9-dimethyl-5-aminophenanthroline derivatives. In the suggested reaction pathway to produce the Boc-protected 2,5,9-triaminophenanthroline, 5 steps out of 7 were successfully achieved. Cleavage studies on all three phenanthroline derivatives will be performed when the final derivatives are synthesized.