Genome-wide sequencing analysis of Sgs1, Exo1, Rad51 and Srs2 in DNA repair by homologous recombination

Homologous recombination is essential to maintain genome stability in response to DNA damage. Here, we have used genome-wide sequencing to quantitatively analyze at nucleotide resolution the dynamics of DNA end resection, re-synthesis and gene conversion at a double-strand break. Resection initiates asymmetrically in an MRXindependent manner before proceeding steadily in both directions. Sgs1, Exo1, Rad51 and Srs2 differently regulate the rate and symmetry of early and late resection. Exo1 also ensures the coexistence of resection and re-synthesis, while Srs2 guarantees a constant and symmetrical DNA re-polymerization. Gene conversion is MMRindependent, spans only a minor fraction of the resected region and its unidirectionality depends on Srs2. Finally, these repair factors prevent the development of alterations remote from the DNA lesion, such as subtelomeric instability, duplication of genomic regions and over-replication of Ty elements. Altogether, this approach allows a quantitative analysis and a direct genome-wide visualization of DNA repair by homologous recombination.