Abstract
DNA polymerase theta (Polθ) has been identified as a crucial alternative non-homologous end-joining factor in mammalian cells. Polθ is upregulated in a range of cancer cell types defective in homologous recombination, and knockdown has been shown to inhibit cell survival in a subset of these, making it an attractive target for cancer treatment. We present crystal structures of the helicase domain of human Polθ in the presence and absence of bound nucleotides, and a characterization of its DNA-binding and DNA-stimulated ATPase activities. Comparisons with related helicases from the Hel308 family identify several unique features. Polθ exists as a tetramer both in the crystals and in solution. We propose a model for DNA binding to the Polθ helicase domain in the context of the Polθ tetramer, which suggests a role for the helicase domain in strand annealing of DNA templates for subsequent processing by the polymerase domain.
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•DNA polymerase theta (Polθ) is unique in having a DNA helicase-like domain•Polθ has a role in the repair of DNA double-strand breaks and in cancer cell survival•We solved the structure of the tetrameric helicase-like domain•The tetramer may align broken DNA ends for microhomology-mediated end joining
We describe a structure of an unusual helicase domain of DNA polymerase theta (Polθ). The helicase-like domain of Polθ forms tetramers and this tetrameric structure might bring together broken DNA ends for microhomology-mediated end joining.
