Peptide nucleic acids (PNAs) are synthetic homologs of nucleic acids with the sugar-phosphate backbone replaced by an uncharged mimic of repeating 2-aminoethyl-glycine units. PNAs bind tightly to single-stranded complementary DNAs to form PNA–DNA hybrids, and would be promising anti-gene agents were it not for their limited ability to reach the cell nucleus. To address this problem, Boffa and colleagues examined whether fusion of a PNA to a nuclear localization signal (NLS) could potentiate their anti-gene effects. They show that an anti-myc PNA–NLS chimera was localized efficiently to the nucleus of cells derived from Burkitt's lymphoma that overexpress c-myc, and that expression of the latter was downregulated. These effects were associated with both inhibition of cell cycle progression and apoptosis (see pp. 304–304 ).