DNA replication, recombination and repair, all of which are necessary for genome stability, require the presence of exonucleases (1). In DNA replication, these enzymes are involved in the processing of Okazaki fragments, whereas in DNA repair, they function to excise damaged DNA fragments and correct recombinational mismatches (2). Exonucleases involved in these processes include DNA polymerases, including DNA pol ? and é. DNA pol ? consists of two subunits, p125 which interacts directly with the sliding DNA clamp protein PCNA, and p50 (3,4). DNA pol ? can be regulated by cell cycle proteins (5). DNA pol é is a multiple subunit enzyme, the catalytic subunit of which is encoded by the POL2 gene (6,7). The exact reactions catalyzed by DNA pol ? and é on leading and lagging strands have not yet been elucidated.