Defining the peptide nucleic acids (PNA) length requirement for PNA binding-induced transcription and gene expression

Induction of gene expression has great potential in the treatment of many h uman diseases. Peptide nucleic acid (PNA) as a novel DNA-binding reagent pr ovides an ideal system to induce gene-specific expression. In our recent st udies, we have demonstrated that PNA bound to double-stranded DNA targets a nd, therefore, generated single-stranded D-loops and induced transcription of target genes both in vitro and in vivo. Most importantly, we have demons trated that treatment of cultured human cells with PNAs led to expression o f an endogenous target gene. Therefore, the study of the molecular mechanis m of PNA binding-induced gene expression will have great implications for t he gene therapy of many human diseases. In the current study, we have inves tigated the PNA length requirement for PNA binding-induced transcription in itiation. Using a series of PNAs with different lengths, we have determined that PNAs with lengths of 16 similar to 18 nt induce very high levels of t ranscription in a HeLa nuclear extract in vitro transcription system. Trans fection of the PNA-bound GFP reporter gene plasmid into human normal fibrob last (NF) cells led to a similar result. Gel-mobility shift assays revealed very strong binding affinities of these PNAs. DNA footprinting analysis fu rther demonstrated the specificity of PNAs binding to the targets. These re sults lead to important understanding of the molecular mechanism of transcr iption initiation and highly valuable information in PNA design, especially for PNA binding-induced, gene-specific expression. (C) 2001 Academic Press .