As accessory component of the DNA polymerase epsilon (DNA polymerase II) participates in chromosomal DNA replication. It is required during synthesis of the leading and lagging DNA strands at the replication fork and binds at/or near replication origins and moves along DNA with the replication fork. It has 3'-5' proofreading exonuclease activity that correct errors arising during DNA replication. It is also involved in DNA synthesis during DNA repair (By similarity). The dpb3-dpb4 dimer associates with histone deacetylases, chromatin remodelers, and histones and plays a crucial role in the inheritance of histone hypoacetylation and H3K9 methylation in heterochromatin (PubMed:29109278). The dpb3-dpb4 dimer is also required for the recruitment of sir2 to heterochromatin (PubMed:29109278). DNA polymerase epsilon is a heterotetramer consisting of cdc20/Pol2, dpb2, dpb3, and dpb4 (By similarity). Heterodimer consisting dpb3 and dpb4 (PubMed:29109278). Interacts with the replication factor dpb3, cdc20, PCNA and rfc5; the replication licensing factors mcm3 and mcm4; the FACT complex subunits spt16 and pob3; the CHD1-type remodeler hrp3; the SWI/SNF chromatin remodeling complex subunits snf22, arp9, arp42, ssr1, ssr3, and ssr4; the histones H4 and H2B; the histone chaperones Nap1 and h; and the histone deacetylases sir2 and clr6 (PubMed:29109278). Interacts with dri1 (PubMed:33693625). Decreases H3K9 methylation and impairs heterochromatin silencing; simultaneous disruption of dri1 exacerbates the effect.