Figure 7.

Schematic diagram of the complexes that are thought to assemble at the GAL2 UAS region at the time of meiotic DSB formation. (A) Spo11 does not self-interact during premeiosis, but Spo11-3FLAG is meiotically recruited to the GAL2 UAS site, at which Gal4BD–Spo11 already exists, as shown in Figure 2D. This association was not detected in rec102Δ, rec104Δ or rec114Δ cells by ChIP assay. (B) In the cells co-expressing Gal4BD-fused protein and Spo11-3FLAG, four types of Spo11 complex may assemble at the GAL2 UAS regions: homocomplexes consisting of either Gal4BD-fused protein alone or heterocomplexes consisting of both Gal4BD-fused protein and Spo11-3FLAG. The homocomplexes of Gal4BD–spo11Y135F cannot introduce DSBs in the GAL2 UAS regions, but the heterocomplex of Gal4BD–spo11Y135F/Spo11-3FLAG is expected to catalyze DSB formation at least partly. However, neither DSBs nor SSBs were detected in cells harboring such heterocomplexes (upper diagram). In cells expressing both Gal4BD–Spo11 and spo11Y135F-3FLAG, the heterocomplex of Gal4BD–Spo11/spo11Y135F-3FLAG formed in the GAL2 UAS regions is inactive (lower diagram).