Peptide nucleic acids (PNAs) are synthetic polynucleobase molecules, which
bind to DNA and RNA with high affinity and specificity. Although PNAs have
enormous potential as anti-sense agents, the success of PNA-mediated gene t
herapy will require efficient cellular uptake and sub-cellular trafficking.
At present these mechanisms are poorly understood To address this, we have
studied the uptake of biotinylated PNAs into cultured cell lines using flu
orescence confocal microscopy. In human myoblasts, initial punctate stainin
g was followed by the release of PNAs into the cytosol and subsequent local
isation and concentration in the nucleus. To determine whether PNAs could a
lso be used as therapeutic agents for mtDNA disease, we attempted to locali
se PNAs to the mitochondrial matrix. When attached to the presequence pepti
de of the nuclear-encoded human cytochrome c oxidase (COX) subunit VIII the
biotinylated PNA was successfully imported into isolated organelles in vit
ro. Furthermore, delivery of the biotinylated peptide-PNA to mitochondria i
n intact cells was confirmed by confocal microscopy. These studies demonstr
ate that biotinylated PNAs can be directed across cell membranes and to a s
pecific sub-cellular compartment within human cells highlighting the import
ance of these novel molecules for human gene therapy.