Significance of DNA Polymerase I in processing of clustered DNA damage

Shikazono, Naoya; Akamatsu, Ken; Takahashi, Momoko*; Noguchi, Miho; Urushibara, Ayumi; O'Neill, P.*; Yokoya, Akinari

We examined the biological consequences of bi-stranded clustered damage sites, consisting of a combination of DNA lesions using a bacterial plasmid-based assay. The transformation efficiencies were significantly lower for the bi-stranded clustered GAP/AP lesions than for either a single GAP or a single AP site. When the two lesions were separated by 10-20 bp, the transformation efficiencies were comparable with those of the single lesions. This recovery of transformation efficiency for separated lesions requires DNA polymerase I (Pol I) activity. Analogously, the mutation frequency was enhanced in a bi-stranded cluster containing a GAP and an 8-oxoG, and Pol I was found to play an important role in minimising mutations induced as a result of clustered lesions. These results indicate that the biological consequences of clustered DNA damage strongly depend on Pol I activity.