A role for nucleosome remodellers during resection of deprotected telomeres in yeast.

Abstract

DNA double-strand break (DSB) repair pathway choice is strongly influenced by DNA end resection, a process in which the 5' DNA strand is degraded to generate 3' single-stranded DNA required for homologous recombination. Although the enzymatic mechanisms of resection have been well defined, its regulation by the dynamic chromatin environment surrounding the DNA break remains less clear. Here, we used the budding yeast cdc13-1 system to analyse DNA end resection after telomere deprotection. Inactivation of Cdc13, a component of the CST (Cdc13-Stn1-Ten1) telomere-capping complex, exposes telomeric DNA ends and triggers a DNA damage response. Using this system, we examined the contribution of long-range resection nucleases and chromatin regulators. Analysis of long-range resection nucleases revealed that the Dna2 nuclease contributes to telomeric processing, particularly in the absence of the exonuclease Exo1. Genetic removal of chromatin regulatory factors showed that H2A.Z, a histone H2A variant incorporated by the SWR1 complex, did not significantly affect resection, whereas depletion of the major nucleosome eviction complexes RSC and SWI/SNF impaired resection after telomere deprotection. Together, these results indicate that nucleosome eviction allows for efficient resection at deprotected telomeres and the analogies to long-range resection at DSBs illustrate the utility of the cdc13-1 system for studying long-range resection in broader context.