Fig. 5.

The effect of heterology at lss ends on strand exchange. (A) Schematic of the D-loop assay using lss with heterology (70 bp) at its end(s). (B) lss was preincubated with Dmc1, then mixed with auxiliary factor(s), RPA, and lds. The reaction was then incubated at 30 °C for 1 h. Dmc1, 5 µM; Hop2-Mnd1, 0.25 µM; lds, 5 µM; lss, 5 µM; RPA, 1 µM; Swi5-Sfr1, 0.5 µM. (C) Quantification of results shown in B. Yield is expressed as the percentage of the signal for the products to the sum of the lds and products. Mean values ± SD from three independent experiments are shown. (D) Stepwise involvement of two auxiliary factors in the establishment of Dmc1-driven synapsis. (a) Following meiotic DSB formation and end-resection, RPA binds to the ssDNA exposed at a DSB end. (b) Swi5-Sfr1 functions as a canonical “mediator” and facilitates the replacement of RPA with Dmc1, which forms a nucleoprotein filament. (c) Hop2-Mnd1 executes its role as an initiator of strand exchange by allowing the Dmc1 filament to invade a donor dsDNA duplex, which constitutes initiation of the synaptic phase. (d) Swi5-Sfr1 and Hop2-Mnd1 may then promote further strand transfer within the synaptic phase, leading to heteroduplex extension. See text for more details.