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
Mentions: To investigate further how condensin regulates DSB processing, we generated an artificial DSB at the rDNA using the I-SceI system (Figure 7A). Artificial DSBs by the I-SceI site-specific endonuclease appear to be processed as endogenous Spo11-mediated DSBs (Fukuda et al., 2008) but would simplify our assay of condensin function in DSB repair. We abolished the formation of endogenous DSBs by the spo11Δ allele and then inserted one copy of the recognition sequence of I-SceI into the 25S rRNA gene where the URA3 marker was incorporated (Figure 2A). On the induction of I-SceI by the meiosis-specific REC8 promoter, I-SceI cut its recognition sequence with ∼80% efficiency, as determined by a PCR-based assay of chromosome breakage (Figure 7B). By fluorescence microscopy, we observed both Rad51 and Rad52 focus formation at the rDNA region (Figure 7C and Supplemental Figure S4, A–C), indicating the formation of rDNA breaks.
Affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370.