ABSTRACT
The two major pathways of DNA double strand break (DSB) repair, non-homologous end-joining (NHEJ) and homologous recombination (HR), are highly conserved from yeast to mammals. Regulated 5’ DNA end resection is important for repair pathway choice and repair outcomes. Nej1 was first identified as a canonical NHEJ factor involved in stimulating the ligation of broken DNA ends and, more recently, it was shown to be important for DNA end-bridging and inhibiting Dna2-Sgs1 mediated 5’ resection. Dna2 localizes to DSBs in the absence of Sgs1 through interactions with Mre11 and Sae2 and DNA damage sensitivity is greater in cells lacking Dna2 nuclease activity compared to sgs1Δ mutants. Dna2-Sae2 mediated 5’ resection is down-regulated by Nej1, which itself interacts with Sae2. The resection defect of sae2Δ and the synthetic lethality of sae2Δ sgs1Δ are reversed by deletion of NEJ1 and dependent on Dna2 nuclease activity. Our work demonstrates the importance of Nej1 in inhibiting short-range resection at a DSB by Dna2-Sae2, a critical regulatory mechanism that prevents the formation of genomic deletions at the break site.
AUTHOR SUMMARY Nej1 regulates double-strand break (DSB) repair pathway choice through the inhibition of 5’ DNA resection. Nej1 not only inhibits resection mediated by Dna2-Sgs1, but it inhibits Dna2 localization to the DSB through Sgs1-independent mechanisms involving Sae2 and Mre11. Nej1 interactions with Sae2 promote genome stability by inhibiting the initiation 5’ DNA resection by Sae2-Dna2.
Competing Interest Statement
The authors have declared no competing interest.