Nej1(XLF) inhibits Sae2(CTIP)-Dna2(DNA2) mediated resection at DNA double strand breaks

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. The regulation of 5 DNA resection controls repair pathway choice and influences 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 5 resection mediated by Dna2-Sgs1. Nej1 interacts with Sae2 and this impacts DSB repair in three ways. First, Nej1 inhibits MRX-Sae2 interactions and Sae2 localization to a DSB. Second, Nej1 inhibits Sae2-dependent recruitment of Dna2 in the absence of Sgs1. Third, NEJ1 and SAE2 showed an epistatic relationship for DNA end-bridging, an event that restrains the broken ends and reduces the frequency of genomic deletions from developing at the DSB. Deletion of NEJ1 suppressed the synthetic lethality of sae2{Delta} sgs1{Delta} and was dependent on the nuclease activity of Dna2. These Nej1 functions promote end-joining DSB repair, but could also be relevant for controlling resection initiation during HR repair. HighlightsO_LINej1 physically interacts with Sae2 and inhibits end-resection at a DSB. C_LIO_LINej1 inhibits Sae2 interactions with the MRX complex. C_LIO_LINej1 inhibits Sae2-dependent recruitment of Dna2 to a DSB. C_LIO_LINEJ1 and SAE2 are epistatic for DNA end-bridging. C_LIO_LIDeletion of NEJ1 suppresses the synthetic lethality of sae2{Delta} sgs1{Delta}, which is dependent on Dna2 nuclease activity. C_LI