Multifaceted down-regulation of the Srs2 helicase by the SUMO-like domain protein Esc2 promotes local recombination at sites of stalled replication

The SUMO-like domains-containing family of proteins to which Saccharomyces cerevisiae Esc2 belongs facilitates DNA damage tolerance (DDT) via elusive mechanisms. Here we report that Esc2 promotes recombination-mediated DDT by engaging in functional and physical interactions with Srs2 and Elg1, two readers of SUMOylated PCNA and modulators of DDT. These interactions depend on the SUMO Interacting Motifs of Elg1 and Srs2, and on the SUMO-like domains of Esc2. Mechanistically, Esc2 promotes Elg1 association to damaged and stalled forks and Srs2 turnover. Elg1 limits the levels of SUMOylated PCNA and subsequently of the anti-recombinase Srs2 at damaged sites, upholding local Rad51 binding. In conjunction with the SUMO–targeted ubiquitin ligase Slx5/Slx8, Esc2 also promotes proteasome-mediated Srs2 turnover, a process further enhanced by CDK-mediated Srs2 phosphorylation. Our results provide mechanistic insights into how SUMO- and DNA damage response-regulated pathways intersect to enable local error-free damage-bypass by recombination in the face of genotoxic stress. Proteins ChIP-chip analyses analysis were carried out as described (Bermejo et al., 2009). Labelled probes were hybridized to Affymetrix S.cerevisiae Tiling 1.0 (P/N 900645) arrays and processed with TAS software.