Post-replicative ssDNA regions at CPD lesions detected by PCR.

<p>(A) Representative samples of sequence deletions generated by a PCR reaction using the pure pQ-CPDs plasmid as template. (B) A schematic drawing for the generation of deletions at single-stranded gaps. Replication of a lesion-containing strand may produce a gap in the daughter strand (grey). The gapped strand is not suitable as a PCR template, so the PCR reaction initially must proceed across the lesion (dashed line). (C) Dpn I digested untransfected control pQTc and lesion-containing pQ-CPDs plasmid do not serve as PCR templates. The indicated amounts of plasmid were subjected to Dpn I digests (+) or mock digests, amplified by PCR and analysed on an agarose gel. A positive control sample extracted from <i>xpa</i> cells and subjected to the same treatment is shown in the right hand lane. (D) The percentage of deletions amongst the PCR products of pure plasmids containing CPD lesions on both strands (pQ-CPDs) or only one strand (pQ-1CPD). (E) The percentage of deletions amongst PCR products of plasmids recovered from transfected cells of the indicated genotypes. The mean percentage and S.E.M. of 3–7 experiments are shown. (F) A reduction of deletion-bearing PCR products when the plasmid recovered from <i>xpa pcna^K164R</i> cells is pre-treated with the ssDNA specific mung bean nuclease. The mean and S.E.M. of 3 experiments are shown.