Involved in the replication of mitochondrial DNA. Associates with mitochondrial DNA (By similarity). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Heterotrimer composed of a catalytic subunit and a homodimer of accessory subunits (By similarity). Interacts with TTC3 (By similarity). Belongs to the DNA polymerase type-A family.