P66, or Polymerase (DNA-directed), delta 3, accessory subunit, is a human gene encoded by POLD3. It may also be known as: DNA polymerase delta subunit 3; DNA polymerase delta subunit p66; Pol delta C subunit (p66); protein phosphatase 1, regulatory subunit 128; P68; PPP1R128. The encoded protein has an amino acid length of 466 and a mass of 51.4 kDa. Other isoforms may exist. Homologs of this gene exist in other organisms, including: Mouse, Rat, Arabidopsis, Zebrafish, Frog, Chicken.