9BH6

Human DNA polymerase theta helicase domain tetramer in the apo form

Summary for 9BH6

• Entry DOI: 10.2210/pdb9bh6/pdb
• EMDB information: 44534
• Descriptor: DNA polymerase theta (1 entity in total)
• Functional Keywords: dna repair, tmej, mmej, dna binding protein
• Biological source: Homo sapiens (human)
• Total number of polymer chains: 4
• Total formula weight: 398685.38

Authors

Zerio, C.J.,Lander, G.C. (deposition date: 2024-04-19, release date: 2024-05-01, Last modification date: 2025-03-12)

Primary citation

Zerio, C.J.,Bai, Y.,Sosa-Alvarado, B.A.,Guzi, T.,Lander, G.C.
Human polymerase theta helicase positions DNA microhomologies for double-strand break repair.
Nat.Struct.Mol.Biol., 2025

PubMed Abstract: DNA double-strand breaks occur daily in all human cells and must be repaired with high fidelity to minimize genomic instability. Deficiencies in high-fidelity DNA repair by homologous recombination lead to dependence on DNA polymerase θ, which identifies DNA microhomologies in 3' single-stranded DNA overhangs and anneals them to initiate error-prone double-strand break repair. The resulting genomic instability is associated with numerous cancers, thereby making this polymerase an attractive therapeutic target. However, despite the biomedical importance of polymerase θ, the molecular details of how it initiates DNA break repair remain unclear. Here, we present cryo-electron microscopy structures of the polymerase θ helicase domain bound to microhomology-containing DNA, revealing DNA-induced rearrangements of the helicase that enable DNA repair. Our structures show that DNA-bound helicase dimers facilitate a microhomology search that positions 3' single-stranded DNA ends in proximity to align complementary bases and anneal DNA microhomology. We characterize the molecular determinants that enable the helicase domain of polymerase θ to identify and pair DNA microhomologies to initiate mutagenic DNA repair, thereby providing insight into potentially targetable interactions for therapeutic interventions.

PubMed: 40021738
DOI: 10.1038/s41594-025-01514-8

Experimental method

ELECTRON MICROSCOPY (3.3 Å)