Catalytic component of the DNA polymerase epsilon complex (PubMed:15135399). Participates in chromosomal DNA replication (PubMed:15135399). Required during synthesis of the leading DNA strands at the replication fork, binds at/or near replication origins and moves along DNA with the replication fork (By similarity). Has 3'-5' proofreading exonuclease activity that corrects errors arising during DNA replication (PubMed:15135399). Has a role in the G1-S transition and/or S-phase progression of the mitotic cycle and endocycle progression (PubMed:11054539, PubMed:15135399, PubMed:21898761). Involved in DNA synthesis during DNA repair (By similarity). Plays roles in larval tissue development (PubMed:22245183, PubMed:21898761). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Binds 1 [4Fe-4S] cluster. Inhibited by the small molecule aphidicolin (PubMed:15135399). Activity is markedly inhibited by manganese ions (PubMed:15135399). Optimum pH is 7.5. Component of the DNA polymerase epsilon complex consisting of four subunits: the catalytic subunit PolE1/DNApol-epsilon255 and the accessory subunits PolE2/DNApol-epsilon58, Chrac-14/DNApolE3 and PolE4. Expressed in salivary glands (at protein level). Expressed in embryos (at protein level) (PubMed:11054539). Expressed at various developmental stages (PubMed:11054539). The DNA polymerase activity domain resides in the N-terminal half of the protein, while the C-terminus is necessary for maintenance of the complex. The C-terminal domain (1001-2236 aa) is required for mitotic DNA replication in the eye but not for DNA endoreplication in salivary glands. The CysA-type zinc finger is required for PCNA-binding. The CysB motif binds 1 4Fe-4S cluster and is required for the formation of polymerase complexes. RNAi-mediated knockdown in the eye disks induces a small eye phenotype and inhibits DNA synthesis (PubMed:22245183). RNAi-mediated knockdown in the salivary glands results in a reduction of salivary glands size together with decreased number and size of nuclei in the tissue (PubMed:22245183). Also causes endoreplication defects (PubMed:22245183). Belongs to the DNA polymerase type-B family.