Figure 1.

Schematic models for the assembly of cohesin and associated factors at double-strand breaks (DSBs), and ATR- and Eco1 (Ctf7)-dependent reactivation of cohesin in G₂ phase. a: In response to DNA DSB damage, cohesin is recruited to the damage site in a S/G₂ phase-specific manner. This is dependent on the Mre11 complex (Mre11–Rad50–Nbs1), the cohesion-loading factor (Scc2–Scc4), and γH2A. In the case of human cells, the Smc5–Smc6 complex is also required for cohesin recruitment to DSBs. For establishment of sister chromatid cohesion, cohesin requires additional factors, including Eco1 (Ctf7), the Smc5–Smc6 complex, and ATR (see b). b: In G₂ phase, DSBs induce ATR activation, which leads to reactivation of cohesin by Eco1 (Ctf7). Mre11 and the Smc5–Smc6 complex may be involved in the same pathway. This process requires the acetyltransferase activity of Eco1 (Ctf7). The targets of ATR-mediated phosphorylation and Eco1 (Ctf7)-mediated acetylation are unknown.