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: We used the assembly and disassembly of spindle microtubules as an alternative means of further defining the timing of meiotic cell progression (Figure 3A). In wild-type cells, rDNA homologues formed a chromatin fiber along the length of the anaphase spindle (Figure 3A, t = 9–12 min), suggesting that homologous rDNAs are linked and that chromosome XII homologues, where rDNA is located, were pulled apart by forces from the spindle. After spindle disassembly, rDNA homologues segregated into opposite poles and formed two rDNA-GFP foci with similar fluorescence intensity (Figure 3A, t = 18–24 min). Of note, if one copy of the homologous rDNAs was marked, only one GFP focus appeared in one of the two poles, indicating that during meiosis I, homologous rDNAs segregated from each other (Supplemental Figure S1, C and D). In contrast to the wild-type cells, PCLB2-BRN1 cells failed to segregate rDNA during the entire course of meiosis I (Figure 3A). To determine whether condensin subunits other than Brn1 are required for rDNA segregation, we observed rDNA dynamics in ycg1-2 cells that were induced to undergo meiosis at 34°C, a nonpermissive temperature for this allele (Yu and Koshland, 2003). In wild-type cells at that temperature, rDNA homologues segregated just as did those in the cell shown in Figure 3A, top. In contrast, ycg1-2 cells failed to segregate the rDNA homologues (Figure 3A). Therefore we conclude that condensin is required for proper rDNA segregation during yeast meiosis.
Affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370.