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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.

Li P, Jin H, Yu HG - Mol. Biol. Cell (2014)

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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370.

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Requirement of condensin for rDNA segregation at anaphase I. (A) Live-cell microscopy showing rDNA dynamics in wild type (WT, HY1829) and condensin mutants, PCLB2-BRN1 (HY2257) and ycg1-2 (HY2847). Both rDNA homologues are marked by tetO/tetR-GFP; α-tubulin (Tub1) was tagged with RFP. Time zero was defined as the onset of anaphase I when the spindle elongates. Microscopy temperature was set at 30°C for PCLB2-BRN1. To inactivate ycg1-2, microscopy was performed at 34°C. (B) Schematic diagram showing the positions of GFP-marked loci on chromosomes IV and XII. (C) Representative images showing the segregation of GFP-marked rDNA during meiosis I. Segregation of GFP-marked loci in meiosis I was determined in cells upon spindle disassembly. (D) Segregation of GFP-marked loci on chromosome XII (HY1829, HY2257, HY2804, HY2805, HY2810, and HY2813). Note that rDNA failed to segregate in PCLB2-BRN1 cells. (E) Segregation of GFP-marked loci on chromosome IV during meiosis I (HY2852, HY2853, HY2858, HY2859, HY2864, and HY2865). (F) Segregation of rDNA and centromere XII in wild-type (HY2810) and ycg1-2 cells during meiosis I (HY3116). (G) Representative images showing sir2Δ and PCLB2-BRN1 cells during meiosis. (H) Segregation of rDNA in sir2Δ and pch2Δ cells during meiosis I (HY3544 and HY3524). For D–F and H, at least 200 cells with disassembled spindles were scored. Bars, 2 μm.
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Figure 3: Requirement of condensin for rDNA segregation at anaphase I. (A) Live-cell microscopy showing rDNA dynamics in wild type (WT, HY1829) and condensin mutants, PCLB2-BRN1 (HY2257) and ycg1-2 (HY2847). Both rDNA homologues are marked by tetO/tetR-GFP; α-tubulin (Tub1) was tagged with RFP. Time zero was defined as the onset of anaphase I when the spindle elongates. Microscopy temperature was set at 30°C for PCLB2-BRN1. To inactivate ycg1-2, microscopy was performed at 34°C. (B) Schematic diagram showing the positions of GFP-marked loci on chromosomes IV and XII. (C) Representative images showing the segregation of GFP-marked rDNA during meiosis I. Segregation of GFP-marked loci in meiosis I was determined in cells upon spindle disassembly. (D) Segregation of GFP-marked loci on chromosome XII (HY1829, HY2257, HY2804, HY2805, HY2810, and HY2813). Note that rDNA failed to segregate in PCLB2-BRN1 cells. (E) Segregation of GFP-marked loci on chromosome IV during meiosis I (HY2852, HY2853, HY2858, HY2859, HY2864, and HY2865). (F) Segregation of rDNA and centromere XII in wild-type (HY2810) and ycg1-2 cells during meiosis I (HY3116). (G) Representative images showing sir2Δ and PCLB2-BRN1 cells during meiosis. (H) Segregation of rDNA in sir2Δ and pch2Δ cells during meiosis I (HY3544 and HY3524). For D–F and H, at least 200 cells with disassembled spindles were scored. Bars, 2 μm.

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.


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.

Li P, Jin H, Yu HG - Mol. Biol. Cell (2014)

Requirement of condensin for rDNA segregation at anaphase I. (A) Live-cell microscopy showing rDNA dynamics in wild type (WT, HY1829) and condensin mutants, PCLB2-BRN1 (HY2257) and ycg1-2 (HY2847). Both rDNA homologues are marked by tetO/tetR-GFP; α-tubulin (Tub1) was tagged with RFP. Time zero was defined as the onset of anaphase I when the spindle elongates. Microscopy temperature was set at 30°C for PCLB2-BRN1. To inactivate ycg1-2, microscopy was performed at 34°C. (B) Schematic diagram showing the positions of GFP-marked loci on chromosomes IV and XII. (C) Representative images showing the segregation of GFP-marked rDNA during meiosis I. Segregation of GFP-marked loci in meiosis I was determined in cells upon spindle disassembly. (D) Segregation of GFP-marked loci on chromosome XII (HY1829, HY2257, HY2804, HY2805, HY2810, and HY2813). Note that rDNA failed to segregate in PCLB2-BRN1 cells. (E) Segregation of GFP-marked loci on chromosome IV during meiosis I (HY2852, HY2853, HY2858, HY2859, HY2864, and HY2865). (F) Segregation of rDNA and centromere XII in wild-type (HY2810) and ycg1-2 cells during meiosis I (HY3116). (G) Representative images showing sir2Δ and PCLB2-BRN1 cells during meiosis. (H) Segregation of rDNA in sir2Δ and pch2Δ cells during meiosis I (HY3544 and HY3524). For D–F and H, at least 200 cells with disassembled spindles were scored. Bars, 2 μm.
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Figure 3: Requirement of condensin for rDNA segregation at anaphase I. (A) Live-cell microscopy showing rDNA dynamics in wild type (WT, HY1829) and condensin mutants, PCLB2-BRN1 (HY2257) and ycg1-2 (HY2847). Both rDNA homologues are marked by tetO/tetR-GFP; α-tubulin (Tub1) was tagged with RFP. Time zero was defined as the onset of anaphase I when the spindle elongates. Microscopy temperature was set at 30°C for PCLB2-BRN1. To inactivate ycg1-2, microscopy was performed at 34°C. (B) Schematic diagram showing the positions of GFP-marked loci on chromosomes IV and XII. (C) Representative images showing the segregation of GFP-marked rDNA during meiosis I. Segregation of GFP-marked loci in meiosis I was determined in cells upon spindle disassembly. (D) Segregation of GFP-marked loci on chromosome XII (HY1829, HY2257, HY2804, HY2805, HY2810, and HY2813). Note that rDNA failed to segregate in PCLB2-BRN1 cells. (E) Segregation of GFP-marked loci on chromosome IV during meiosis I (HY2852, HY2853, HY2858, HY2859, HY2864, and HY2865). (F) Segregation of rDNA and centromere XII in wild-type (HY2810) and ycg1-2 cells during meiosis I (HY3116). (G) Representative images showing sir2Δ and PCLB2-BRN1 cells during meiosis. (H) Segregation of rDNA in sir2Δ and pch2Δ cells during meiosis I (HY3544 and HY3524). For D–F and H, at least 200 cells with disassembled spindles were scored. Bars, 2 μm.
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.

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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370.

Show MeSH
Related in: MedlinePlus