| Topic | Key points | Best supporting source(s) with DOI/URL and publication date | Evidence notes/quantitative data |
|---|---|---|---|
| Complex role | Human POLD2 (p50; UniProt P49005) is an accessory subunit of the heterotetrameric DNA polymerase δ (Polδ) complex with POLD1, POLD3, and POLD4. It has a central structural role, mediating interactions within the complex, especially with POLD3, rather than providing catalytic polymerase or exonuclease activity. (pqac-00000005, pqac-00000007, pqac-00000000) | Conde et al., *J Clin Invest* (2019), doi:10.1172/JCI128903, https://doi.org/10.1172/jci128903, Aug 2019; Gola et al., *Cancers* (2023), doi:10.3390/cancers15061905, https://doi.org/10.3390/cancers15061905, Mar 2023; Alli et al., *Int J Mol Sci* (2024), doi:10.3390/ijms252212417, https://doi.org/10.3390/ijms252212417, Nov 2024 | Conde et al. describe POLD2 as central to POLD1/POLD3 interactions; Alli et al. note the POLD2–POLD3 interaction is essential for normal Polδ function. (pqac-00000005, pqac-00000000) |
| Interactions | POLD2 directly participates in protein-interaction networks relevant to replication and damage tolerance. It interacts functionally with POLD3 in Polδ, is shared with Polζ4, and can bind translesion polymerase η (Polη), supporting polymerase switching at damaged DNA. (pqac-00000006, pqac-00000001, pqac-00000000) | Baldeck et al., *Nucleic Acids Res* (2015), doi:10.1093/nar/gkv076, https://doi.org/10.1093/nar/gkv076, Feb 2015; Wu et al., *Nat Commun* (2023), doi:10.1038/s41467-023-35992-5, https://doi.org/10.1038/s41467-023-35992-5, Feb 2023; Alli et al., *Int J Mol Sci* (2024), doi:10.3390/ijms252212417, https://doi.org/10.3390/ijms252212417, Nov 2024 | Baldeck et al. showed the FF483–484 motif of human Polη is required for Polη–POLD2 interaction in vitro and in vivo, and that disrupting this interaction impairs lesion bypass and UV survival. Wu et al. note POLD2 and POLD3 are shared subunits of Polδ and Polζ4 in replication-stress responses. (pqac-00000006, pqac-00000001) |
| Domains/structure | POLD2 contains a phosphodiesterase-like (PDE) domain and structurally important CysA/CysB motifs; the CysB iron–sulfur cluster has been proposed to influence POLD1 catalytic function through the subunit interface. The disease-associated Asp293 residue lies in the PDE domain at the POLD2–POLD3 interface. (pqac-00000002, pqac-00000000) | Conde et al., *J Clin Invest* (2019), doi:10.1172/JCI128903, https://doi.org/10.1172/jci128903, Aug 2019; Alli et al., *Int J Mol Sci* (2024), doi:10.3390/ijms252212417, https://doi.org/10.3390/ijms252212417, Nov 2024 | Structural modeling predicted POLD2 Asp293Asn disrupts local electrostatic interactions, including loss of a contact with Arg240, weakening the POLD2–POLD3 interface. Alli et al. highlight CysA/CysB motifs and propose Fe–S-dependent regulation within Polδ. (pqac-00000002, pqac-00000000) |
| Pathways | POLD2 functions in core genome duplication as part of Polδ and also contributes to DNA repair-associated DNA synthesis. Recent work links Polδ subunits to mitotic DNA synthesis (MiDAS) after replication stress, and POLD2/POLD3 are also incorporated into Polζ4, connecting POLD2 to translesion synthesis and repair pathway switching. (pqac-00000001, pqac-00000005, pqac-00000006) | Wu et al., *Nat Commun* (2023), doi:10.1038/s41467-023-35992-5, https://doi.org/10.1038/s41467-023-35992-5, Feb 2023; Conde et al., *J Clin Invest* (2019), doi:10.1172/JCI128903, https://doi.org/10.1172/jci128903, Aug 2019; Baldeck et al., *Nucleic Acids Res* (2015), doi:10.1093/nar/gkv076, https://doi.org/10.1093/nar/gkv076, Feb 2015 | Wu et al. report MiDAS requires sequential action of Polζ and Polδ and that POLD2/POLD3 are essential for this synthesis. Conde et al. connect POLD2 loss to replication-associated DNA lesions and impaired cell-cycle progression reversible by Polδ overexpression. (pqac-00000001, pqac-00000005) |
| Localization | The available gathered evidence supports POLD2 action in nuclear DNA replication/repair complexes rather than a non-nuclear role, based on its participation in Polδ/Polζ and its association with replication-stress and DNA-damage phenotypes in patient cells. A specific dedicated subcellular-localization experiment for POLD2 was not captured in the gathered evidence set. (pqac-00000005, pqac-00000003) | Conde et al., *J Clin Invest* (2019), doi:10.1172/JCI128903, https://doi.org/10.1172/jci128903, Aug 2019 | Evidence is inferential from nuclear genome maintenance phenotypes (replication stress, 53BP1 nuclear bodies, DNA-damage-associated rescue by WT POLD2) rather than from direct microscopy/localization mapping in the gathered excerpts. (pqac-00000003) |
| Disease variants | A homozygous human POLD2 missense variant, p.Asp293Asn, causes an autosomal-recessive polymerase δ deficiency syndrome with replicative stress, neurodevelopmental abnormalities, and immunodeficiency. Mechanistically, the variant reduces POLD2 stability and weakens interaction with POLD1/POLD3, destabilizing the whole Polδ complex. (pqac-00000002, pqac-00000003, pqac-00000004) | Conde et al., *J Clin Invest* (2019), doi:10.1172/JCI128903, https://doi.org/10.1172/jci128903, Aug 2019; Yamaguchi & Cotterill, *Int J Mol Sci* (2023), doi:10.3390/ijms24098078, https://doi.org/10.3390/ijms24098078, Apr 2023 | In the JCI study, 2 patients from 2 pedigrees had biallelic Polδ deficiency involving POLD1 or POLD2. POLD2 p.Asp293Asn had CADD 28.1, was absent from ExAC/1000 Genomes, reduced POLD2/POLD1/POLD3 protein despite similar mRNA, and WT POLD2 rescue reduced elevated G1/S-G2 53BP1 nuclear bodies; cells with >2 53BP1 foci were 42.5% (S phase) and 28.2% (G1) in P1 versus 18.3% and 10.6% in healthy donor cells. (pqac-00000002, pqac-00000003) |
| Clinical/prognostic associations | POLD2 has emerging biomarker relevance in cancer, especially multiple myeloma treated with autologous stem cell transplant (ASCT), where higher expression is associated with worse overall survival. The effect appears treatment-context dependent, as it was not significant in non-transplant myeloma cohorts. (pqac-00000009, pqac-00000010, pqac-00000011) | Thomas et al., *Haematologica* (2023), doi:10.3324/haematol.2022.282399, https://doi.org/10.3324/haematol.2022.282399, Mar 2023 | BER-pathway expression was assessed across 450 clinical samples and 6 disease stages and was broadly upregulated during MM development; POLD2 was among genes significantly upregulated in MM versus MGUS. In ASCT-treated MM, high POLD2 expression associated with worse OS in GSE2658 (n=559; HR 1.47, 95% CI 0.99–2.17, P=0.06) and was significant in an independent ASCT validation cohort (n=356; HR 1.67, 95% CI 1.03/1.04–2.71/2.68, P=0.04/0.03 as reported across excerpts). In non-transplant MM (n=319), POLD2 was not associated with OS (HR 1.06, 95% CI 0.75–1.48, P=0.75). (pqac-00000009, pqac-00000010, pqac-00000011) |


*Table: This table summarizes evidence-supported facts about human POLD2, including its role in the Polδ complex, structural features, pathway involvement, disease variants, and emerging clinical associations. It is designed as a compact reference for functional annotation with direct source and quantitative evidence.*