Change in miRNA levels in SH-SY5Y cells after electroporation of peptide nucleic acid (PNA) targeting precursor micro RNA

However, the practical applications of triplex-forming PNAs have been limited by sequence restrictions, as stable base triples are formed only with purines. Hoogsteen recognition of pyrimidines has been a long-standing challenge.

Here, a new approach to improve pyrimidine recognition by enhancing nucleobase stacking in the PNA strand is demonstrated by targeting procursor micro RNA (pre-miRNA). Placing 5-triazolyl uridine adjacent to the modified nucleobases designed for Hoogsteen recognition of pyrimidines in double helical RNA increased the binding affinity while maintaining sequence specificity. The increased binding affinity improved the biological activity of triplex-forming PNAs.