DNA polymerase delta catalytic subunit (POLD1) is a ~123 kDa protein. As the catalytic component of the trimeric (Pol-delta3 complex) and tetrameric DNA polymerase delta complexes (Pol-delta4 complex), plays a crucial role in high fidelity genome replication, including in lagging strand synthesis, and repair. Exhibits both DNA polymerase and 3'- to 5'-exonuclease activities. Requires the presence of accessory proteins POLD2, POLD3 and POLD4 for full activity. Depending upon the absence (Pol-delta3) or the presence of POLD4 (Pol-delta4), displays differences in catalytic activity. Most notably, expresses higher proofreading activity in the context of Pol-delta3 compared with that of Pol-delta4. 1. Li, H. et al. (2006) The Journal of biological chemistry 281, 14748-55. PMID: 165104482. Meng, X. et al. (2009) Nucleic acids research 37, 647-57. PMID: 190741964. Terai, K. et al. (2013) The Journal of biological chemistry 288, 30509-30514. PMID: 240224806. Conde, CD. et al. (2019) The Journal of clinical investigation 129, 4194-4206. PMID: 314490588. Costantino, L. et al. (2014) Science (New York, N.Y.) 343, 88-91. PMID: 243106119. Maga, G. et al. (2013) Proceedings of the National Academy of Sciences of the United States of America 110, 18850-5. PMID: 24191025 | 
