Condensin suppresses recombination and regulates double-strand break processing at the repetitive ribosomal DNA array to ensure proper chromosome segregation during meiosis in budding yeast.
Bottom Line: Condensin is highly enriched at the rDNA region during prophase I, released at the prophase I/metaphase I transition, and reassociates with rDNA before anaphase I onset.We show that condensin plays a dual role in maintaining rDNA stability: it suppresses the formation of Spo11-mediated rDNA breaks, and it promotes DSB processing to ensure proper chromosome segregation.Our work reveals that condensin coordinates meiotic recombination with chromosome segregation at the repetitive rDNA sequence, thereby maintaining genome integrity.
Affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370.Show MeSH
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Mentions: To address the timing of condensin function that is required for meiotic recombination and chromosome segregation, we determined the execution point of condensin using the ycg1-2 allele (Lavoie et al., 2004) because of its reversibility in inactivation and reactivation of the Ycg1 protein with temperature shift (Figure 6). We used the GAL4.ER PGAL-NDT80 allele (Carlile and Amon, 2008) to stage yeast cells at pachytene, which is permissible for DSB formation. On the addition of estradiol and activation of NDT80 gene expression, yeast cells resumed meiosis (Figure 6A). We found that the total number of Rad51 foci formed was comparable in arrested yeast cells at pachytene, but >60% of ycg1-2 cells showed Rad51 focus formation at the rDNA when meiosis was induced at the nonpermissive temperature (Figure 6, B–D). Furthermore, Rad51 foci persisted at the rDNA region at anaphase if ycg1-2 cells were induced to undergo meiosis at the nonpermissive temperature (Figure 6, E and F). Similarly, ∼50% of ycg1-2 cells retained Rad51 foci at rDNA even at anaphase if these cells were shifted from the permissive to the nonpermissive temperature before being released from pachytene (Figure 6, E–G). In contrast, there was little Rad51 focus formation on anaphase chromosomes when cells were switched from the nonpermissive to the permissive temperature (Figure 6, E–G), demonstrating that upon the reactivation of Ycg1 at the permissive temperature, DSBs can be repaired.
Affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370.