Model for rad52-Y66A hyper-recombination. (A) Genetic requirements for C × C versus C × P recombination. Centromere regions are tethered to the spindle-pole body (SPB) at the nuclear envelope (NE) thereby restricting the mobility of the plasmid-borne ade2-n allele and reducing its availability for heteroallelic recombination. Loss of centromere function in the ctf4Δ mutant mobilizes the plasmid to become available for heteroallelic recombination. The mre11Δ and rad52-Y66A mutants show defects in DNA damage-induced cohesion or a failure to complete recombination before cohesion is disassembled, respectively, leading to increased C × C recombination. The spatial restriction of the plasmid-borne heteroallele to the SPB is not releaved in mre11Δ and rad52-Y66A mutants. (B) Transient cohesion model. Mre11 facilitates damage-induced cohesion (dashed lines) which favors the sister chromatid as a template for DSB repair (in grey, i and ii). After approximately 20 min, Mre11 dissociates from the DSB, which may be followed by a gradual loss of cohesion. If repair is not accomplished before loss of cohesion, the DSB may be released to interact with the homologue (in black, iii and vi).