DNA strand breaks are repaired by DNA synthesis from an exposed DNA end paired with a homologous DNA template. DNA polymerase delta (Pol δ) catalyses DNA synthesis in multiple eukaryotic DNA break repair pathways but triggers genome instability unless its activity is restrained. We show that human HelQ halts DNA synthesis by isolated Pol δ and Pol δ-PCNA-RPA holoenzyme. Using novel HelQ mutant proteins we identify that inhibition of Pol δ is independent of DNA binding, and maps to a 70 amino acid intrinsically disordered region of HelQ. Pol δ and its POLD3 subunit robustly stimulated DNA single-strand annealing by HelQ, and POLD3 and HelQ interact physically via the intrinsically disordered HelQ region. This data, and inability of HelQ to inhibit DNA synthesis by the POLD1 catalytic subunit of Pol δ, reveal a mechanism for limiting DNA synthesis and promoting DNA strand annealing during human DNA break repair, which centres on POLD3.
|Original language||English (US)|
|Journal||Nucleic acids research|
|State||Published - Jan 31 2023|
Bibliographical noteKAUST Repository Item: Exported on 2023-02-08
Acknowledged KAUST grant number(s): BAS/1/1002-01-01
Acknowledgements: Nanna Therapeutics, Cambridge, U.K. (to E.L.B.); BBSRC [BB/T006625/1 to E.L.B., BB/R013357/1 to P.S.]; King Abdullah University of Science and Technology (KAUST) Baseline Funding [BAS/1/1002-01-01 to S.M.H.]; PhD studentships from the BBSRC DTP; University of Nottingham School of Chemistry. Funding for open access charge: University of Nottingham Gold. We thank Stuart Wood, Aurelio Reyes, Christopher Cooper and Stan Jozwiakowski for comments, and Michell Hawkins for gifting E. coli polymerase enzymes.
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