biostudies-literatureShimada KNovartis Research FoundationSwiss National Science FoundationSwiss Cancer Leaguee202101138https://www.ebi.ac.uk/biostudies/studies/S-EPMC8321694biostudies-literatureUnknown4(9)DNA polymerase δ, which contains the catalytic subunit, Pol3, Pol31, and Pol32, contributes both to DNA replication and repair. The deletion of pol31 is lethal, and compromising the Pol3-Pol31 interaction domains confers hypersensitivity to cold, hydroxyurea (HU), and methyl methanesulfonate, phenocopying pol32Δ. We have identified alanine-substitutions in pol31 that suppress these deficiencies in pol32Δ cells. We characterize two mutants, pol31-T415A and pol31-W417A, which map to a solvent-exposed loop that mediates Pol31-Pol3 and Pol31-Rev3 interactions. The pol31-T415A substitution compromises binding to the Pol3 CysB domain, whereas Pol31-W417A improves it. Importantly, loss of Pol32, such as pol31-T415A, leads to reduced Pol3 and Pol31 protein levels, which are restored by pol31-W417ALife science allianceThe stabilized Pol31-Pol3 interface counteracts Pol32 ablation with differential effects on repair.PMC83216944167-02-201731003A-176286176286Vijeh Motlagh NDGut HTsai-Pflugfelder MFuchs JGasser SMDelgoshaie NShimada KfalseThe stabilized Pol31-Pol3 interface counteracts Pol32 ablation with differential effects on repair.DNA polymerase δ, which contains the catalytic subunit, Pol3, Pol31, and Pol32, contributes both to DNA replication and repair. The deletion of pol31 is lethal, and compromising the Pol3-Pol31 interaction domains confers hypersensitivity to cold, hydroxyurea (HU), and methyl methanesulfonate, phenocopying pol32Δ. We have identified alanine-substitutions in pol31 that suppress these deficiencies in pol32Δ cells. We characterize two mutants, pol31-T415A and pol31-W417A, which map to a solvent-exposed loop that mediates Pol31-Pol3 and Pol31-Rev3 interactions. The pol31-T415A substitution compromises binding to the Pol3 CysB domain, whereas Pol31-W417A improves it. Importantly, loss of Pol32, such as pol31-T415A, leads to reduced Pol3 and Pol31 protein levels, which are restored by pol31-W417A2021-01-01T00:00:00Z2021 Sep2025-05-31T23:33:28.155Z2025-05-31T23:33:28.155ZS-EPMC83216943422627810.26508/lsa.202101138