DNA polymerase λ mediates a back-up base excision repair activity in extracts of mouse embryonic fibroblasts

Abstract

Mammalian DNA polymerase (pol) λ is a member of the X-family of DNA polymerases and has striking enzymatic and structural similarities to mammalian DNA pol β. Because pol β provides two important enzymatic activities for base excision repair (BER), we examined whether pol λ might also contribute to BER. We used extracts from mouse embryonic fibroblasts representing wild-type and null genotypes for pol β and pol λ. In combination with neutralizing antibodies against pol β and pol λ, our results show a BER deficiency in the pol λ -/- cell extract compared with extract from isogenic wild-type cells. In addition, the pol λ antibody strongly reduced in vitro BER in the pol β -/- cell extract. These data indicate that pol λ is able to contribute to BER in mouse fibroblast cell extract.