DNA polymerases are required in every process that requires DNA synthesis: DNA replication, DNA repair and DNA recombination. Each of the six DNA polymerase has specific functions but most of them depend on each other. The DNA polymerase δ is involved in DNA replication, DNA recombination and DNA repair processes. Its association with the proliferating cell nuclear antigen (PCNA) confers to the DNA polymerase δ a high processivity (Bruning and Shamoo, 2004). It is therefore not surprising that the DNA polymerase δ synthetizes the lagging strand from elongated RNA primers at DNA replication forks (Burgers, 2009). The DNA polymerase δ is composed of four subunits: the DNA polymerase δ subunits 1 (POLD1), 2 (POLD2), 3 (POLD3) and 4 (POLD4). The third subunit of the DNA polymerase δ (POLD3) is required for cell cycle progression and DNA repair during DNA replication stress. The structure of the N-terminal domain (1-144) of POLD3 in complex with POLD2 (Baranovskiy et al., 2008) has been determined as well as the structure of the C- terminal part (452-466) in association with PCNA (Bruning and Shamoo, 2004). However the function and the interacting partners of POLD3 remain unknown. Moreover this domain has not been structurally determined yet. In this project, we identified different region within the core domain of POLD3 but did not obtain any crystal of this region. We confirmed that POLD3 is an intrinsically disordered protein and we suggest that PTMs mainly regulate POLD3 function in presence or absence of DNA replication stress. We finally identified proteins interacting with the core domain of POLD3 in absence of DNA replication stress.