Cell cycle-dependent kinetochore localization of condensin complex in Saccharomyces cerevisiae.
ABSTRACT In budding yeast mitosis is endonuclear and associated with a very limited condensation of the chromosomes. Despite this partial chromosomal condensation, condensin is conserved and essential for the Saccharomyces cerevisiae mitotic cycle. Here, we investigate the localization of condensin during the mitotic cycle. In addition to a constitutive association with rDNA, we have discovered that condensin is localized to the kinetochore in a cell cycle-dependent manner. Shortly after duplication of the spindle pole body, the yeast equivalent of the centrosome, we observed a local enrichment of condensin colocalizing with kinetochore components. This specific association is consistent with mutant phenotypes of chromosome loss and defective sister chromatid separation at anaphase. During a short period of the cell cycle, we observed, at the single cell level, a spatial proximity of condensin and a cohesin rosette, without colocalization. Furthermore, using a genetic screen we demonstrated that condensin localization at kinetochores is specifically impaired in a mutant for ulp2/smt4, an abundant SUMO protease. In conclusion, during chromosome segregation, we established a SUMO-dependent cell cycle-specific condensin concentration colocalizing with kinetochores.
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ABSTRACT: To protect against aneuploidy, chromosomes must attach to microtubules from opposite poles ('biorientation') prior to their segregation during mitosis. Biorientation relies on the correction of erroneous attachments by the aurora B kinase, which destabilizes kinetochore-microtubule attachments that lack tension. Incorrect attachments are also avoided because sister kinetochores are intrinsically biased towards capture by microtubules from opposite poles. Here, we show that shugoshin acts as a pericentromeric adaptor that plays dual roles in biorientation in budding yeast. Shugoshin maintains the aurora B kinase at kinetochores that lack tension, thereby engaging the error correction machinery. Shugoshin also recruits the chromosome-organizing complex, condensin, to the pericentromere. Pericentromeric condensin biases sister kinetochores towards capture by microtubules from opposite poles. Our findings uncover the molecular basis of the bias to sister kinetochore capture and expose shugoshin as a pericentromeric hub controlling chromosome biorientation. DOI: http://dx.doi.org/10.7554/eLife.01374.001.eLife Sciences 02/2014; 3:e01374. DOI:10.7554/eLife.01374 · 8.52 Impact Factor
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ABSTRACT: During meiosis, homologues are linked by crossover, which is required for bipolar chromosome orientation before chromosome segregation at anaphase I. The repetitive ribosomal DNA array, however, undergoes little or no meiotic recombination. Hyper-recombination can cause chromosome mis-segregation and rDNA copy number instability. We report here that condensin, a conserved protein complex required for chromosome organization, regulates double-strand break (DSB) formation and repair at the rDNA gene cluster during meiosis in budding yeast. Condensin is highly enriched at the rDNA region during prophase I, released at the prophase-I-to-metaphase-I transition, and reassociates with rDNA prior to 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. Condensin is unnecessary for the export of rDNA breaks outside the nucleolus but required for timely repair of meiotic DSBs. Our work reveals that condensin coordinates meiotic recombination with chromosome segregation at the repetitive rDNA sequence, thereby maintaining genome integrity.Molecular Biology of the Cell 08/2014; 25(19). DOI:10.1091/mbc.E14-05-0957 · 4.55 Impact Factor
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ABSTRACT: Meiosis is a specialised cell division essential for sexual reproduction. During meiosis the chromosomes are highly organised and correct chromosome architecture is required for faithful segregation of chromosomes at anaphase I and II. Condensin is involved in chromosome organisation during meiotic and mitotic cell divisions. Three condensin subunits, AtSMC4 and the condensin I and II specific subunits AtCAP-D2 and AtCAP-D3 respectively, have been studied for their role in meiosis. This has revealed that both the condensin I and condensin II complexes are required to maintain normal structural integrity of the meiotic chromosomes during the two nuclear divisions. Their roles appear functionally distinct in that condensin I is required to maintain normal compaction of the centromeric repeats and 45S rDNA, whereas loss of condensin II was associated with extensive inter-chromosome connections at metaphase I. Depletion of condensin is also associated with a slight reduction in crossover formation suggesting a role during meiotic prophase I.This article is protected by copyright. All rights reserved.The Plant Journal 07/2014; 80(2). DOI:10.1111/tpj.12628 · 6.82 Impact Factor