Polymerase DNA Directed Gamma 2 (POLg2)

POLg2 is a 55 kDa accessory subunit protein that imparts high processivity and salt tolerance to the catalytic subunit of DNA polymerase gamma. The deduced 372-amino acid POLG2 protein shares 31% amino acid identity with the 361-amino acid Drosophila homolog; a leucine zipper motif in the POLG2 C terminus shares 55% identity. In its middle portion, however, the human POLG2 protein has a zinc-binding signature sequence rather than a zinc finger motif like the Drosophila protein.Titration experiments using bacteria-produced POLG2 showed that a slight excess of POLG2 is required for maximal stimulation of POLG1 activity. Immunoblot analysis demonstrated that recombinant and mitochondrial POLG2 copurify with POLG1 and that POLG2 is expressed as an approximately 54-kD protein