Figure 7.

Roles of cohesin-related Molecules for Meiotic Recombination. (A) Scheme representing the collaborative action of Pds5, Rec8 and Rad61/Wapl in the maintenance of homolog bias for CO and NCO. The Pds5 gatekeeper collaborates with Rec8 for DSB formation and for maintenance of homolog bias, both for COs and NCOs. Rec8, Pds5 and Rad61/Wapl have distinct roles at distinct stages in the progression of DSB to CO/NCO; Rec8 is specifically required for COs at the DSB-SEI transition, as previously shown (19). By implication, Rad61/Wapl specifically promotes NCO formation by removing [Pds5+Rec8] cohesin complexes. (B) Homolog bias for CO and NCO during meiosis. Partner choice at the dHJ step is determined by which chromatids are engaged in the pre-dHJ. In WT meiosis, this structure forms only between non-sister chromatids and yields and IH-dHJ, and could produce an IH-CO (19,69). However, if the second DSB end is associated with the sister chromatid, and also can undergo tail extension and pre-dHJ formation, the result would be an IS-dHJ and possible, an IS-CO between sisters. In the absence of [Pds5+Rec8], first- and second-end states are now equivalent, with an equal probability of capturing another end. Rad61/Wapl is required for formation of IH-NCOs only if both Rec8 and Pds5 are present. See the ‘Discussion’ section for further details.