Baranovskiy, A.G.Babayeva, N.D.Lisova, A.E.Morstadt, L.M.Tahirov, T.H.2025-08-042025-08-042022Proceedings of the National Academy of Sciences of USA, 2022; 119(17):e2111744119-1-e2111744119-70027-84241091-6490https://hdl.handle.net/2440/146472Human DNA polymerase α (Polα) does not possess proofreading ability and plays an important role in genome replication and mutagenesis. Polα extends the RNA primers generated by primase and provides a springboard for loading other replication factors. Here we provide the structural and functional analysis of the human Polα interaction with a mismatched template:primer. The structure of the human Polα catalytic domain in the complex with an incoming deoxycytidine triphosphate (dCTP) and the template: primer containing a T-C mismatch at the growing primer terminus was solved at a 2.9 Å resolution. It revealed the absence of significant distortions in the active site and in the conformation of the substrates, except the primer 3′-end. The T-C mismatch acquired a planar geometry where both nucleotides moved toward each other by 0.4 Å and 0.7 Å, respectively, and made one hydrogen bond. The binding studies conducted at a physiological salt concentration revealed that Polα has a low affinity to DNA and is not able to discriminate against a mispaired template:primer in the absence of deoxynucleotide triphosphate (dNTP). Strikingly, in the presence of cognate dNTP, Polα showed a more than 10-fold higher selectivity for a correct duplex versus a mismatched one. According to pre-steady-state kinetic studies, human Polα extends the T-C mismatch with a 249-fold lower efficiency due to reduction of the polymerization rate constant by 38-fold and reduced affinity to the incoming nucleotide by 6.6-fold. Thus, a mismatch at the postinsertion site affects all factors important for primer extension: affinity to both substrates and the rate of DNA polymerization.en© 2022 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).DNA polymerase α; DNA replication; crystal structure; mismatch; kinetic studiesHumansDNA Polymerase IDNA PrimersDNA ReplicationCatalytic DomainKineticsJournal article10.1073/pnas.2111744119693303Lisova, A.E. [0000-0002-3647-6460]