Nucleotide excision repair DNA synthesis by excess DNA polymerase β: a potential source of genetic instability in cancer cells

Abstract

The nucleotide excision repair pathway contributes to genetic stability by removing a wide range of DNA damage through an error-free reaction. When the lesion is located, the altered strand is incised on both sides of the lesion and a damaged oligonucleotide excised. A repair patch is then synthesized and the repaired strand is ligated. It is assumed that only DNA polymerases δ and/or ε participate to the repair DNA synthesis step. Using UV and cisplatin-modified DNA templates, we measured in vitro that extracts from cells overexpressing the error-prone DNA polymerase β exhibited a five-to sixfold increase of the ultimate DNA synthesis activity compared with control extracts and demonstrated the specific involvement of Pol β in this step. By using a 28 nt gapped, double-stranded DNA substrate mimicking the product of the incision step, we showed that Pol β is able to catalyze strand displacement downstream of the gap. We discuss these data within the scope of a hypothesis previously presented proposing that excess error-prone Pol β in cancer cells could perturb the well-defined specific functions of DNA polymerases during error-free DNA transactions.—Canitrot, Y., Hoffmann, J.-S., Calsou, P., Hayakawa, H., Salles, B., Cazaux, C. Nucleotide excision repair DNA synthesis by excess DNA polymerase β: a potential source of genetic instability in cancer cells. FASEB J. 14, 1765–1774 (2000)