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Small tandem DNA duplications result from CST-guided Pol α-primase action at DNA break termini.

ABSTRACT: Small tandem duplications of DNA occur frequently in the human genome and are implicated in the aetiology of certain human cancers. Recent studies have suggested that DNA double-strand breaks are causal to this mutational class, but the underlying mechanism remains elusive. Here, we identify a crucial role for DNA polymerase α (Pol α)-primase in tandem duplication formation at breaks having complementary 3' ssDNA protrusions. By including so-called primase deserts in CRISPR/Cas9-induced DNA break configurations, we reveal that fill-in synthesis preferentially starts at the 3' tip, and find this activity to be dependent on 53BP1, and the CTC1-STN1-TEN1 (CST) and Shieldin complexes. This axis generates near-blunt ends specifically at DNA breaks with 3' overhangs, which are subsequently repaired by non-homologous end-joining. Our study provides a mechanistic explanation for a mutational signature abundantly observed in the genomes of species and cancer cells.

SUBMITTER: Schimmel J

PROVIDER: S-EPMC8355091 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Natural insertions in rice commonly form tandem duplications indicative of patch-mediated double-strand break induction and repair.

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