Abstract
AbstractA DNA double strand break (DSB) is one of the most dangerous types of DNA damage that is repaired largely by homologous recombination (HR) or non-homologous end-joining (NHEJ). The interplay of repair factors at the break directs which pathway is used, and a subset of these factors also function in more mutagenic alternative (alt) repair pathways. Resection is a key event in repair pathway choice and extensive resection, which is a hallmark of HR, is mediated by two nucleases, Exo1 and Dna2. We observed differences in resection and repair outcomes in cells harbouring nuclease deaddna2-1 compared todna2Δpif1-m2 that could be attributed to the level of Exo1 recovered at DSBs. Cells harbouringdna2-1 showed reduced Exo1 localization, increased NHEJ, and a greater defect in resection compared to cells whereDNA2was deleted. Both the decreased level of resection and the increased rate of NHEJ indna2-1 mutants were reversed upon deletion ofKU70or ectopic expression of Exo1. By contrast, whenDNA2was deleted, Exo1 and Ku70 recovery levels did not change, however Nej1 increased as did the frequency of alt-EJ/ MMEJ repair. Our findings demonstrate that decreased Exo1 at DSBs contributed to the resection defect in cells expressing inactive Dna2 and highlight the complexity of understanding how functionally redundant factors are regulatedin vivoto promote genome stability.Graphical Abstract
Publisher
Cold Spring Harbor Laboratory