Abstract
We have explored the meiotic roles of cohesin modulators Pds5 and Rad61/Wapl, in relation to one another, and to meiotic kleisin Rec8, for homolog pairing, all physically definable steps of recombination, prophase axis length and S-phase progression, in budding yeast. We show that Pds5 promotes early steps of recombination and thus homolog pairing, and also modulates axis length, with both effects independent of a sister chromatid. [Pds5+Rec8] promotes double-strand break formation, maintains homolog bias for crossover formation and promotes S-phase progression. Oppositely, the unique role of Rad61/Wapl is to promote non-crossover recombination by releasing [Pds5+Rec8]. For this effect, Rad61/Wapl probably acts to maintain homolog bias by preventing channeling into sister interactions. Mysteriously, each analyzed molecule has one role that involves neither of the other two. Overall, the presented findings suggest that Pds5’s role in maintenance of sister chromatid cohesion during the mitotic prophase-analogous stage of G2/M is repurposed during meiosis prophase to promote interactions between homologs.
Highlights
Meiosis is the specialized cellular program by which a diploid progenitor cell gives rise to haploid cells for gametogenesis
Pds5 is required for early stages of meiotic recombination
Cells were arrested at the end of prophase and Pds5 was severely depleted with a meiosis-specific induction of a Pds5 degron (PDS5-AID + IAA)
Summary
Meiosis is the specialized cellular program by which a diploid progenitor cell gives rise to haploid cells for gametogenesis. A single round of DNA replication is followed by two rounds of chromosome segregation; at the first meiotic division (MI), replicated homologous chromosomes (‘homologs’) segregate to opposite poles, a process that is absent from the mitotic program. The central unique feature of meiosis is a highly programmed sequence of interactions between homologs, and cohesins play important roles in this process as well; in addition, cohesins are important for formation of meiotic prophase chromosome axes and for regulation of meiotic S-phase progression [2]. Meiotic recombination occurs preferentially between homolog chromatids rather than between sister chromatids as during mitotic DSB repair. ‘Homolog bias’ is established at this very early step These initiating interactions are differentiated into two types. After CO/NCO differentiation, both types of interactions undergo additional steps by which they are matured to their respective products
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