DNA replication, recombination and repair, all of which are necessary for genomic stability, require the presence of exonucleases. In DNA replication, exonucleases are involved in the processing of Okazaki fragments, whereas in DNA repair, they function to excise damaged DNA fragments and correct recombinational mismatches. These exonucleases include the family of DNA polymerases, namely DNA pol alpha, beta, delta and E. DNA pol delta and DNA pol E are multisubunit enzymes, with DNA pol delta consisting of two subunits which interact with the sliding DNA clamp protein PCNA. DNA pol delta 3, also known as POLD3 or p66, is a 466 amino acid nuclear protein that is required for the proper function of DNA pol delta.