9AU8

Ternary complex of human DNA polymerase theta polymerase domain with a mismatched T:T base pair

Summary for 9AU8

• Entry DOI: 10.2210/pdb9au8/pdb
• EMDB information: 43874
• Descriptor: DNA polymerase theta, DNA (5'-D(P*CP*GP*TP*AP*GP*(DOC))-3'), DNA (5'-D(P*AP*GP*TP*GP*CP*TP*AP*CP*G)-3'), ... (5 entities in total)
• Functional Keywords: dna translesion synthesis, theta-mediated end joining, a-family dna polymerase, dna binding protein-dna complex, dna binding protein/dna
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 3
• Total formula weight: 105146.74

Authors

Li, C.,Gao, Y. (deposition date: 2024-02-28, release date: 2025-03-05, Last modification date: 2025-05-28)

Primary citation

Li, C.,Maksoud, L.M.,Gao, Y.
Structural basis of error-prone DNA synthesis by DNA polymerase theta.
Nat Commun, 16:2063-2063, 2025

PubMed Abstract: DNA polymerase θ (Pol θ) is an A-family DNA polymerase specialized in DNA double-strand breaks repair and translesion synthesis. Distinct from its high-fidelity homologs in DNA replication, Pol θ catalyzes template-dependent DNA synthesis with an inherent propensity for error incorporation. However, the structural basis of Pol θ's low-fidelity DNA synthesis is not clear. Here, we present cryo-electron microscopy structures detailing the polymerase domain of human Pol θ in complex with a cognate C:G base pair (bp), a mismatched T:G bp, or a mismatched T:T bp. Our structures illustrate that Pol θ snugly accommodates the mismatched nascent base pairs within its active site with the finger domain well-closed, consistent with our in-solution fluorescence measurement but in contrast to its high-fidelity homologs. In addition, structural examination and mutagenesis study show that unique residues surrounding the active site contribute to the stabilization of the mismatched nascent base pair. Furthermore, Pol θ can efficiently extend from the misincorporated T:G or T:T mismatches, yet with a preference for template or primer looping-out, resulting in insertions and deletions. Collectively, our results elucidate how an A-family polymerase is adapted for error-prone DNA synthesis.

PubMed: 40021647
DOI: 10.1038/s41467-025-57269-9

Experimental method

ELECTRON MICROSCOPY (3.44 Å)