Figure 7.

Selective inhibition of DNA replication by ph–PNA conjugates. (A) An in vitro replication run-off assay from a mtDNA template containing the MERRF mutation was performed. In the absence of ph–PNA this gave a product of 341 nt. In the presence of 50 or 100-fold molar excess of ph–PNA a truncated product of 245 nt was formed. (B) An in vitro replication run-off assay from a wild-type mtDNA template was performed. This template differed from the MERRF template in (A) at a single nucleotide position in the PNA binding region. In the absence of ph–PNA this gave a full-length product of 350 nt (the MERRF DNA template is shorter due to a 9 bp deletion at the 3′ end, downstream of the replication inhibition site). Even in the presence of a 500-fold molar excess of ph–PNA none of the truncated product of 245 nt was found, in contrast to the positive control using the MERRF template. The binding affinities of PNA and ph–PNA to the MERRF PNA templates were 11.3 ± 2.2 and 37 ± 6 nM, respectively (Paul Smith, University of Newcastle upon Tyne, personal communication).