Catalytic component of DNA polymerase delta (DNA polymerase III) which participates in chromosomal DNA replication (PubMed:31488849). Required during synthesis of the lagging DNA strands at the replication fork, binds at/or near replication origins and moves along DNA with the replication fork (PubMed:31488849). Participates in leading strand synthesis during replication initiation and termination (PubMed:31488849). Has 3'-5' proofreading exonuclease activity that corrects errors arising during DNA replication (By similarity). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Binds 1 [4Fe-4S] cluster. Heterotetramer that consist of the pol3, cdc1, cdc27 and cdm1 subunits. The pol3 subunit contains the polymerase active site and most likely the active site for the 3'-5' exonuclease activity. The CysB motif binds 1 4Fe-4S cluster and is required for the formation of polymerase complexes. In eukaryotes there are five DNA polymerases: alpha, beta, gamma, delta, and epsilon which are responsible for different reactions of DNA synthesis. Belongs to the DNA polymerase type-B family.