151
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Pearson CG, Gardner MK, Paliulis LV, Salmon ED, Odde DJ, Bloom K. Measuring nanometer scale gradients in spindle microtubule dynamics using model convolution microscopy. Mol Biol Cell 2006; 17:4069-79. [PMID: 16807354 PMCID: PMC1593174 DOI: 10.1091/mbc.e06-04-0312] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2006] [Revised: 06/09/2006] [Accepted: 06/20/2006] [Indexed: 11/11/2022] Open
Abstract
A computational model for the budding yeast mitotic spindle predicts a spatial gradient in tubulin turnover that is produced by kinetochore-attached microtubule (kMT) plus-end polymerization and depolymerization dynamics. However, kMTs in yeast are often much shorter than the resolution limit of the light microscope, making visualization of this gradient difficult. To overcome this limitation, we combined digital imaging of fluorescence redistribution after photobleaching (FRAP) with model convolution methods to compare computer simulations at nanometer scale resolution to microscopic data. We measured a gradient in microtubule dynamics in yeast spindles at approximately 65-nm spatial intervals. Tubulin turnover is greatest near kinetochores and lowest near the spindle poles. A beta-tubulin mutant with decreased plus-end dynamics preserves the spatial gradient in tubulin turnover at a slower time scale, increases average kinetochore microtubule length approximately 14%, and decreases tension at kinetochores. The beta-tubulin mutant cells have an increased frequency of chromosome loss, suggesting that the accuracy of chromosome segregation is linked to robust kMT plus-end dynamics.
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Affiliation(s)
- Chad G. Pearson
- *Department of Molecular, Cellular, and Developmental Biology, University of Colorado at Boulder, Boulder, CO 80309-0347
| | - Melissa K. Gardner
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455; and
| | - Leocadia V. Paliulis
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280
| | - E. D. Salmon
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280
| | - David J. Odde
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455; and
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280
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152
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Zhang T, Lim HH, Cheng CS, Surana U. Deficiency of centromere-associated protein Slk19 causes premature nuclear migration and loss of centromeric elasticity. J Cell Sci 2006; 119:519-31. [PMID: 16443750 DOI: 10.1242/jcs.02757] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
The cohesin complex prevents premature segregation of duplicated chromosomes by providing resistance to the pole-ward pull by spindle microtubules. The centromeric region (or sister kinetochores) bears the majority of this force and undergoes transient separation prior to anaphase, indicative of its elastic nature. A cysteine protease, separase, cleaves the cohesin subunit Scc1 and dissolves cohesion between sister chromatids, initiating their separation. Separase also cleaves the kinetochore protein Slk19 during anaphase. Slk19 has been implicated in stabilization of the mitotic spindle and regulation of mitotic exit, but it is not known what role it plays at the kinetochores. We show that during pre-anaphase arrest, the spindle in slk19Delta cells is excessively dynamic and the nuclei move into mother-daughter junction prematurely. As a result, the chromatin mass undergoes partial division that requires neither anaphase promoting complex (APC) activity nor Scc1 cleavage. Partial division of the chromatin mass is accompanied by the loss of the centromeric region's ability to resist pole-ward pull by the spindle. Slk19 physically associates with Scc1 and this association appears necessary for efficient cleavage of Slk19 by separase. Our results suggest that Slk19 participates in regulating nuclear migration and, in conjunction with cohesin complex, may be involved in the maintenance of centromeric tensile strength to resist the pole-ward pull.
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Affiliation(s)
- Tao Zhang
- Institute of Molecular and Cell Biology, Proteos, 61 Biopolis Drive, Singapore 138673
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153
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Abstract
Accurate chromosome segregation during mitosis requires biorientation of sister chromatids on the microtubules (MT) of the mitotic spindle. Chromosome–MT binding is mediated by kinetochores, which are multiprotein structures that assemble on centromeric (CEN) DNA. The simple CENs of budding yeast are among the best understood, but the roles of kinesin motor proteins at yeast kinetochores have yet to be determined, despite evidence of their importance in higher eukaryotes. We show that all four nuclear kinesins in Saccharomyces cerevisiae localize to kinetochores and function in three distinct processes. Kip1p and Cin8p, which are kinesin-5/BimC family members, cluster kinetochores into their characteristic bilobed metaphase configuration. Kip3p, a kinesin-8,-13/KinI kinesin, synchronizes poleward kinetochore movement during anaphase A. The kinesin-14 motor Kar3p appears to function at the subset of kinetochores that become detached from spindle MTs. These data demonstrate roles for structurally diverse motors in the complex processes of chromosome segregation and reveal important similarities and intriguing differences between higher and lower eukaryotes.
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Affiliation(s)
- Jessica D Tytell
- Department of Biology and 2Biological Engineering Division Massachusetts Institute of Technology Cambridge MA 02139, USA
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154
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Wirth KG, Wutz G, Kudo NR, Desdouets C, Zetterberg A, Taghybeeglu S, Seznec J, Ducos GM, Ricci R, Firnberg N, Peters JM, Nasmyth K. Separase: a universal trigger for sister chromatid disjunction but not chromosome cycle progression. J Cell Biol 2006; 172:847-60. [PMID: 16533945 PMCID: PMC2063729 DOI: 10.1083/jcb.200506119] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Accepted: 02/14/2006] [Indexed: 12/30/2022] Open
Abstract
Separase is a protease whose liberation from its inhibitory chaperone Securin triggers sister chromatid disjunction at anaphase onset in yeast by cleaving cohesin's kleisin subunit. We have created conditional knockout alleles of the mouse Separase and Securin genes. Deletion of both copies of Separase but not Securin causes embryonic lethality. Loss of Securin reduces Separase activity because deletion of just one copy of the Separase gene is lethal to embryos lacking Securin. In embryonic fibroblasts, Separase depletion blocks sister chromatid separation but does not prevent other aspects of mitosis, cytokinesis, or chromosome replication. Thus, fibroblasts lacking Separase become highly polyploid. Hepatocytes stimulated to proliferate in vivo by hepatectomy also become unusually large and polyploid in the absence of Separase but are able to regenerate functional livers. Separase depletion in bone marrow causes aplasia and the presumed death of hematopoietic cells other than erythrocytes. Destruction of sister chromatid cohesion by Separase may be a universal feature of mitosis in eukaryotic cells.
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Affiliation(s)
- Karin G Wirth
- Research Institute of Molecular Pathology, A-1030 Vienna, Austria
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155
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Abstract
When a cell prepares to divide, the chromosomes need to separate at just the right moment. Regulating the cohesion of chromosomes is key to achieving this
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156
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Asakawa K, Kume K, Kanai M, Goshima T, Miyahara K, Dhut S, Tee WW, Hirata D, Toda T. The V260I mutation in fission yeast alpha-tubulin Atb2 affects microtubule dynamics and EB1-Mal3 localization and activates the Bub1 branch of the spindle checkpoint. Mol Biol Cell 2006; 17:1421-35. [PMID: 16394105 PMCID: PMC1382329 DOI: 10.1091/mbc.e05-08-0802] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Revised: 12/13/2005] [Accepted: 12/27/2005] [Indexed: 11/11/2022] Open
Abstract
We have identified a novel temperature-sensitive mutant of fission yeast alpha-tubulin Atb2 (atb2-983) that contains a single amino acid substitution (V260I). Atb2-983 is incorporated into the microtubules, and their overall structures are not altered noticeably, but microtubule dynamics is compromised during interphase. atb2-983 displays a high rate of chromosome missegregation and is synthetically lethal with deletions in a subset of spindle checkpoint genes including bub1, bub3, and mph1, but not with mad1, mad2, and mad3. During early mitosis in this mutant, Bub1, but not Mad2, remains for a prolonged period in the kinetochores that are situated in proximity to one of the two SPBs (spindle pole bodies). High dosage mal3(+), encoding EB1 homologue, rescues atb2-983, suggesting that Mal3 function is compromised. Consistently, Mal3 localization and binding between Mal3 and Atb2-983 are impaired significantly, and a mal3 single mutant, such as atb2-983, displays prolonged Bub1 kinetochore localization. Furthermore in atb2-983 back-and-forth centromere oscillation during prometaphase is abolished. Intriguingly, this oscillation still occurs in the mal3 mutant, indicating that there is another defect independent of Mal3. These results show that microtubule dynamics is important for coordinated execution of mitotic events, in which Mal3 plays a vital role.
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Affiliation(s)
- Kazuhide Asakawa
- Laboratory of Cell Regulation, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3PX, UK
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157
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Kiburz BM, Reynolds DB, Megee PC, Marston AL, Lee BH, Lee TI, Levine SS, Young RA, Amon A. The core centromere and Sgo1 establish a 50-kb cohesin-protected domain around centromeres during meiosis I. Genes Dev 2005; 19:3017-30. [PMID: 16357219 PMCID: PMC1315405 DOI: 10.1101/gad.1373005] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Accepted: 11/07/2005] [Indexed: 11/25/2022]
Abstract
The stepwise loss of cohesins, the complexes that hold sister chromatids together, is required for faithful meiotic chromosome segregation. Cohesins are removed from chromosome arms during meiosis I but are maintained around centromeres until meiosis II. Here we show that Sgo1, a protein required for protecting centromeric cohesins from removal during meiosis I, localizes to cohesin-associated regions (CARs) at the centromere and the 50-kb region surrounding it. Establishment of this Sgo1-binding domain requires the 120-base-pair (bp) core centromere, the kinetochore component Bub1, and the meiosis-specific factor Spo13. Interestingly, cohesins and the kinetochore proteins Iml3 and Chl4 are necessary for Sgo1 to associate with pericentric regions but less so for Sgo1 to associate with the core centromeric regions. Finally, we show that the 50-kb Sgo1-binding domain is the chromosomal region where cohesins are protected from removal during meiosis I. Our results identify the portions of chromosomes where cohesins are protected from removal during meiosis I and show that kinetochore components and cohesins themselves are required to establish this cohesin protective domain.
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Affiliation(s)
- Brendan M Kiburz
- Center for Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, 02139, USA
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158
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Oliveira RA, Coelho PA, Sunkel CE. The condensin I subunit Barren/CAP-H is essential for the structural integrity of centromeric heterochromatin during mitosis. Mol Cell Biol 2005; 25:8971-84. [PMID: 16199875 PMCID: PMC1265781 DOI: 10.1128/mcb.25.20.8971-8984.2005] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During cell division, chromatin undergoes structural changes essential to ensure faithful segregation of the genome. Condensins, abundant components of mitotic chromosomes, are known to form two different complexes, condensins I and II. To further examine the role of condensin I in chromosome structure and in particular in centromere organization, we depleted from S2 cells the Drosophila CAP-H homologue Barren, a subunit exclusively associated with condensin I. In the absence of Barren/CAP-H the condensin core subunits DmSMC4/2 still associate with chromatin, while the other condensin I non-structural maintenance of chromosomes family proteins do not. Immunofluorescence and in vivo analysis of Barren/CAP-H-depleted cells showed that mitotic chromosomes are able to condense but fail to resolve sister chromatids. Additionally, Barren/CAP-H-depleted cells show chromosome congression defects that do not appear to be due to abnormal kinetochore-microtubule interaction. Instead, the centromeric and pericentromeric heterochromatin of Barren/CAP-H-depleted chromosomes shows structural problems. After bipolar attachment, the centromeric heterochromatin organized in the absence of Barren/CAP-H cannot withstand the forces exerted by the mitotic spindle and undergoes irreversible distortion. Taken together, our data suggest that the condensin I complex is required not only to promote sister chromatid resolution but also to maintain the structural integrity of centromeric heterochromatin during mitosis.
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Affiliation(s)
- Raquel A Oliveira
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Portugal
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159
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Blow JJ, Tanaka TU. The chromosome cycle: coordinating replication and segregation. Second in the cycles review series. EMBO Rep 2005; 6:1028-34. [PMID: 16264427 PMCID: PMC1371039 DOI: 10.1038/sj.embor.7400557] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Accepted: 08/25/2005] [Indexed: 11/08/2022] Open
Abstract
During the cell-division cycle, chromosomal DNA must initially be precisely duplicated and then correctly segregated to daughter cells. The accuracy of these two events is maintained by two interlinked cycles: the replication licensing cycle, which ensures precise duplication of DNA, and the cohesion cycle, which ensures correct segregation. Here we provide a general overview of how these two systems are coordinated to maintain genetic stability during the cell cycle.
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Affiliation(s)
- J Julian Blow
- University of Dundee, Wellcome Trust Biocentre, Dow Street, Dundee DD1 5EH, UK.
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160
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Ivanov D, Nasmyth K. A topological interaction between cohesin rings and a circular minichromosome. Cell 2005; 122:849-60. [PMID: 16179255 DOI: 10.1016/j.cell.2005.07.018] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Revised: 07/06/2005] [Accepted: 07/18/2005] [Indexed: 01/26/2023]
Abstract
Sister chromatid cohesion depends on a multiprotein cohesin complex containing two SMC subunits, Smc1 and Smc3, that dimerize to form V-shaped molecules with ABC-like ATPase heads at the tips of their two arms. Cohesin's Smc1 and Smc3 "heads" are connected by an alpha kleisin subunit called Scc1, forming a tripartite ring with a diameter around 40 nm. We show here that some cohesin remains tightly bound to circular minichromosomes after their purification from yeast cells and that cleavage either of cohesin's ring or of the minichromosome's DNA destroys their association. This suggests that the stable association between cohesin and chromatin detected here is topological rather than physical, which is consistent with the notion that DNA is trapped inside cohesin rings.
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Affiliation(s)
- Dmitri Ivanov
- Research Institute of Molecular Pathology, Vienna, Austria
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161
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Wang BD, Eyre D, Basrai M, Lichten M, Strunnikov A. Condensin binding at distinct and specific chromosomal sites in the Saccharomyces cerevisiae genome. Mol Cell Biol 2005; 25:7216-25. [PMID: 16055730 PMCID: PMC1190225 DOI: 10.1128/mcb.25.16.7216-7225.2005] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mitotic chromosome condensation is chiefly driven by the condensin complex. The specific recognition (targeting) of chromosomal sites by condensin is an important component of its in vivo activity. We previously identified the rRNA gene cluster in Saccharomyces cerevisiae as an important condensin-binding site, but both genetic and cell biology data suggested that condensin also acts elsewhere. In order to characterize the genomic distribution of condensin-binding sites and to assess the specificity of condensin targeting, we analyzed condensin-bound sites using chromatin immunoprecipitation and hybridization to whole-genome microarrays. The genomic condensin-binding map shows preferential binding sites over the length of every chromosome. This analysis and quantitative PCR validation confirmed condensin-occupied sites across the genome and in the specialized chromatin regions: near centromeres and telomeres and in heterochromatic regions. Condensin sites were also enriched in the zones of converging DNA replication. Comparison of condensin binding in cells arrested in G(1) and mitosis revealed a cell cycle dependence of condensin binding at some sites. In mitotic cells, condensin was depleted at some sites while enriched at rRNA gene cluster, subtelomeric, and pericentromeric regions.
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Affiliation(s)
- Bi-Dar Wang
- Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Cancer Institute, Bethesda, MD 20892, USA
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162
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Kline-Smith SL, Sandall S, Desai A. Kinetochore-spindle microtubule interactions during mitosis. Curr Opin Cell Biol 2005; 17:35-46. [PMID: 15661517 PMCID: PMC8184134 DOI: 10.1016/j.ceb.2004.12.009] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The kinetochore is a proteinaceous structure that assembles onto centromeric DNA and mediates chromosome attachment to microtubules during mitosis. This description is deceivingly simple: recent proteomic studies suggest that the diminutive kinetochores of Saccharomyces cerevisiae are comprised of at least 60 proteins organized into as many as 14 different subcomplexes. Many of these proteins, such as the centromeric histone variant CENP-A, and entire subcomplexes, such as the Ndc80(Hec1) complex, are conserved from yeast to humans despite the diverse nature of the DNA sequences on which they assemble. There have recently been advances in our understanding of the molecular basis of how kinetochores establish dynamic attachments to spindle microtubules, and how these attachments are correctly oriented to ensure segregation of sister chromatids to daughter cells.
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Affiliation(s)
- Susan L Kline-Smith
- Ludwig Institute for Cancer Research, Department of Cellular & Molecular Medicine, University of California, San Diego, 9500 Gilman Dr, CMM-East, Rm 3080, La Jolla, California 92093, USA
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163
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Gardner MK, Pearson CG, Sprague BL, Zarzar TR, Bloom K, Salmon ED, Odde DJ. Tension-dependent regulation of microtubule dynamics at kinetochores can explain metaphase congression in yeast. Mol Biol Cell 2005; 16:3764-75. [PMID: 15930123 PMCID: PMC1182314 DOI: 10.1091/mbc.e05-04-0275] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
During metaphase in budding yeast mitosis, sister kinetochores are tethered to opposite poles and separated, stretching their intervening chromatin, by singly attached kinetochore microtubules (kMTs). Kinetochore movements are coupled to single microtubule plus-end polymerization/depolymerization at kinetochore attachment sites. Here, we use computer modeling to test possible mechanisms controlling chromosome alignment during yeast metaphase by simulating experiments that determine the 1) mean positions of kinetochore Cse4-GFP, 2) extent of oscillation of kinetochores during metaphase as measured by fluorescence recovery after photobleaching (FRAP) of kinetochore Cse4-GFP, 3) dynamics of kMTs as measured by FRAP of GFP-tubulin, and 4) mean positions of unreplicated chromosome kinetochores that lack pulling forces from a sister kinetochore. We rule out a number of possible models and find the best fit between theory and experiment when it is assumed that kinetochores sense both a spatial gradient that suppresses kMT catastrophe near the poles and attachment site tension that promotes kMT rescue at higher amounts of chromatin stretch.
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Affiliation(s)
- Melissa K Gardner
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
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164
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Machín F, Torres-Rosell J, Jarmuz A, Aragón L. Spindle-independent condensation-mediated segregation of yeast ribosomal DNA in late anaphase. ACTA ACUST UNITED AC 2005; 168:209-19. [PMID: 15657393 PMCID: PMC2171579 DOI: 10.1083/jcb.200408087] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mitotic cell division involves the equal segregation of all chromosomes during anaphase. The presence of ribosomal DNA (rDNA) repeats on the right arm of chromosome XII makes it the longest in the budding yeast genome. Previously, we identified a stage during yeast anaphase when rDNA is stretched across the mother and daughter cells. Here, we show that resolution of sister rDNAs is achieved by unzipping of the locus from its centromere-proximal to centromere-distal regions. We then demonstrate that during this stretched stage sister rDNA arrays are neither compacted nor segregated despite being largely resolved from each other. Surprisingly, we find that rDNA segregation after this period no longer requires spindles but instead involves Cdc14-dependent rDNA axial compaction. These results demonstrate that chromosome resolution is not simply a consequence of compacting chromosome arms and that overall rDNA compaction is necessary to mediate the segregation of the long arm of chromosome XII.
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Affiliation(s)
- Félix Machín
- Cell Cycle Group, Clinical Sciences Centre, Medical Research Council, Imperial College London, London W12 0NN, England, UK
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165
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Korolev AV, Chan J, Naldrett MJ, Doonan JH, Lloyd CW. Identification of a novel family of 70 kDa microtubule-associated proteins in Arabidopsis cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 42:547-55. [PMID: 15860013 DOI: 10.1111/j.1365-313x.2005.02393.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Most plant microtubule-associated proteins (MAPs) have homologues across the phylogenetic spectrum. To find potential plant-specific MAPs that will have evaded bioinformatic searches we devised a low stringency method for isolating proteins from an Arabidopsis cell suspension on endogenous taxol-microtubules. By tryptic peptide mass fingerprinting we identified 55 proteins that were enriched on taxol-microtubules. Amongst a range of known MAPs, such as kinesins, MAP65 isoforms and MOR1, we detected 'unknown' 70 kDa proteins that belong to a family of five closely related Arabidopsis proteins having no known homologues amongst non-plant organisms. To verify that AtMAP70-1 associates with microtubules in vivo, it was expressed as a GFP fusion. This confirmed that the protein decorates all four microtubule arrays in both transiently infected Arabidopsis and stably transformed tobacco BY-2 suspension cells. Microtubule-directed drugs perturbed the localization of AtMAP70-1 but cytochalasin D did not. AtMAP70-1 contains four predicted coiled-coil domains and truncation studies identified a central domain that targets the fusion protein to microtubules in vivo. This study therefore introduces a novel family of plant-specific proteins that interact with microtubules.
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Affiliation(s)
- Andrey V Korolev
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK
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166
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Moore LL, Stanvitch G, Roth MB, Rosen D. HCP-4/CENP-C promotes the prophase timing of centromere resolution by enabling the centromere association of HCP-6 in Caenorhabditis elegans. Mol Cell Biol 2005; 25:2583-92. [PMID: 15767665 PMCID: PMC1061647 DOI: 10.1128/mcb.25.7.2583-2592.2005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prior to microtubule capture, sister centromeres resolve from one another, coming to rest on opposite surfaces of the condensing chromosome. Subsequent assembly of sister kinetochores at each sister centromere generates a geometry favorable for equal levels of segregation of chromatids. The holocentric chromosomes of Caenorhabditis elegans are uniquely suited for the study of centromere resolution and subsequent kinetochore assembly. In C. elegans, only two proteins have been identified as being necessary for centromere resolution, the kinase AIR-2 (prophase only) and the centromere protein HCP-4/CENP-C. Here we found that the loss of proteins involved in chromosome cohesion bypassed the requirement for HCP-4/CENP-C but not for AIR-2. Interestingly, the loss of cohesin proteins also restored the localization of HCP-6 to the kinetochore. The loss of the condensin II protein HCP-6 or MIX-1/SMC2 impaired centromere resolution. Furthermore, the loss of HCP-6 or MIX-1/SMC2 resulted in no centromere resolution when either nocodazole or RNA interference (RNAi) of the kinetochore protein KNL-1 perturbed spindle-kinetochore interactions. This result suggests that normal prophase centromere resolution is mediated by condensin II proteins, which are actively recruited to sister centromeres to mediate the process of resolution.
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Affiliation(s)
- Landon L Moore
- Department of Genetics and Genomics, Boston University School of Medicine, 715 Albany St., E642, Boston, MA 02118, USA.
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167
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Rankin S, Ayad NG, Kirschner MW. Sororin, a substrate of the anaphase-promoting complex, is required for sister chromatid cohesion in vertebrates. Mol Cell 2005; 18:185-200. [PMID: 15837422 DOI: 10.1016/j.molcel.2005.03.017] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2004] [Revised: 03/04/2005] [Accepted: 03/18/2005] [Indexed: 12/17/2022]
Abstract
We have identified a regulator of sister chromatid cohesion in a screen for cell cycle-controlled proteins. This 35 kDa protein is degraded through anaphase-promoting complex (APC)-dependent ubiquitination in G1. The protein is nuclear in interphase cells, dispersed from the chromatin in mitosis, and interacts with the cohesin complex. In Xenopus embryos, overexpression of the protein causes failure to resolve and segregate sister chromatids in mitosis and an increase in the level of cohesin associated with metaphase chromosomes. In cultured cells, depletion of the protein causes mitotic arrest and complete failure of sister chromatid cohesion. This protein is thus an essential, cell cycle-dependent mediator of sister chromatid cohesion. Based on sequence analysis, this protein has no apparent orthologs outside of the vertebrates. We speculate that the protein, which we have named sororin, regulates the ability of the cohesin complex to mediate sister chromatid cohesion, perhaps by altering the nature of the interaction of cohesin with the chromosomes.
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Affiliation(s)
- Susannah Rankin
- Systems Biology Department, Harvard Medical School, Boston, Massachusetts 02115, USA.
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168
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Jones MH, Huneycutt BJ, Pearson CG, Zhang C, Morgan G, Shokat K, Bloom K, Winey M. Chemical genetics reveals a role for Mps1 kinase in kinetochore attachment during mitosis. Curr Biol 2005; 15:160-5. [PMID: 15668173 DOI: 10.1016/j.cub.2005.01.010] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2004] [Revised: 11/11/2004] [Accepted: 11/12/2004] [Indexed: 11/21/2022]
Abstract
Accurate chromosome segregation depends on proper assembly and function of the kinetochore and the mitotic spindle. In the budding yeast, Saccharomyces cerevisiae, the highly conserved protein kinase Mps1 has well-characterized roles in spindle pole body (SPB, yeast centrosome equivalent) duplication and the mitotic checkpoint. However, an additional role for Mps1 is suggested by phenotypes of MPS1 mutations that include genetic interactions with kinetochore mutations and meiotic chromosome segregation defects and also by the localization of Mps1 at the kinetochore, the latter being independent of checkpoint activation. We have developed a new MPS1 allele, mps1-as1, that renders the kinase specifically sensitive to a cell-permeable ATP analog inhibitor, allowing us to perform high-resolution execution point experiments that identify a novel role for Mps1 subsequent to SPB duplication. We demonstrate, by using both fixed- and live-cell fluoresence techniques, that cells lacking Mps1 function show severe defects in mitotic spindle formation, sister kinetochore positioning at metaphase, and chromosome segregation during anaphase. Taken together, our experiments are consistent with an important role for Mps1 at the kinetochore in mitotic spindle assembly and function.
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Affiliation(s)
- Michele H Jones
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, CO 80309-0347, USA
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169
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Bouck DC, Bloom KS. The kinetochore protein Ndc10p is required for spindle stability and cytokinesis in yeast. Proc Natl Acad Sci U S A 2005; 102:5408-13. [PMID: 15809434 PMCID: PMC556225 DOI: 10.1073/pnas.0405925102] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The budding yeast kinetochore is comprised of >60 proteins and associates with 120 bp of centromeric (CEN) DNA. Kinetochore proteins are highly dynamic and exhibit programmed cell cycle changes in localization. The CEN-specific histone, Cse4p, is one of a few stable kinetochore components and remains associated with CEN DNA throughout mitosis. In contrast, several other kinetochore proteins have been observed along interpolar microtubules and at the midzone during anaphase. The inner kinetochore protein, Ndc10p, is enriched at the spindle midzone in late anaphase. We show that Ndc10p is transported to the plus-ends of interpolar microtubules at the midzone during anaphase, a process that requires survivin (Bir1p), a member of the aurora kinase (Ipl1p) complex, and Cdc14p phosphatase. In addition, Ndc10p is required for essential non-kinetochore processes during mitosis. Cells lacking functional Ndc10p show defects in spindle stability during anaphase and failure to split the septin ring during cytokinesis. This latter phenotype leads to a cell separation defect in ndc10-1 cells. We propose that Ndc10p plays a direct role in maintaining spindle stability during anaphase and coordinates the completion of cell division after chromosome segregation.
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Affiliation(s)
- David C Bouck
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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170
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Tanaka K, Mukae N, Dewar H, van Breugel M, James EK, Prescott AR, Antony C, Tanaka TU. Molecular mechanisms of kinetochore capture by spindle microtubules. Nature 2005; 434:987-94. [PMID: 15846338 DOI: 10.1038/nature03483] [Citation(s) in RCA: 219] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2004] [Accepted: 02/18/2005] [Indexed: 11/09/2022]
Abstract
For high-fidelity chromosome segregation, kinetochores must be properly captured by spindle microtubules, but the mechanisms underlying initial kinetochore capture have remained elusive. Here we visualized individual kinetochore-microtubule interactions in Saccharomyces cerevisiae by regulating the activity of a centromere. Kinetochores are captured by the side of microtubules extending from spindle poles, and are subsequently transported poleward along them. The microtubule extension from spindle poles requires microtubule plus-end-tracking proteins and the Ran GDP/GTP exchange factor. Distinct kinetochore components are used for kinetochore capture by microtubules and for ensuring subsequent sister kinetochore bi-orientation on the spindle. Kar3, a kinesin-14 family member, is one of the regulators that promote transport of captured kinetochores along microtubules. During such transport, kinetochores ensure that they do not slide off their associated microtubules by facilitating the conversion of microtubule dynamics from shrinkage to growth at the plus ends. This conversion is promoted by the transport of Stu2 from the captured kinetochores to the plus ends of microtubules.
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Affiliation(s)
- Kozo Tanaka
- School of Life Sciences, University of Dundee, Wellcome Trust Biocentre, Dundee DD1 5EH, UK
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171
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Abstract
For proper chromosome segregation, sister kinetochores must attach to microtubules extending from opposite spindle poles prior to anaphase onset. This state is called sister kinetochore bi-orientation or chromosome bi-orientation. The mechanism ensuring chromosome bi-orientation lies at the heart of chromosome segregation, but is still poorly understood. Recent evidence suggests that mal-oriented kinetochore-to-pole connections are corrected in a tension-dependent mechanism. The cohesin complex and the Ipl1/Aurora B protein kinase seem to be key regulators for this correction. In this article, I discuss how cells ensure sister kinetochore bi-orientation for all chromosomes, mainly focusing on our recent findings in budding yeast.
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Affiliation(s)
- Tomoyuki U Tanaka
- School of Life Sciences, University of Dundee, Wellcome Trust Biocentre, Dow Street, Dundee DD1 5EH, Scotland, UK.
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172
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Abstract
The sister chromatid cohesion essential for the bi-orientation of chromosomes on mitotic spindles depends on a multi-subunit complex called cohesin. This paper reviews the evidence that cohesin is directly responsible for holding sister DNAs together and considers how it might perform this function in the light of recent data on its structure.
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Affiliation(s)
- Kim Nasmyth
- IMP (Research Institute of Molecular Pathology), Dr Bohr-Gasse 7, A-1030 Vienna, Austria.
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173
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McGuinness BE, Hirota T, Kudo NR, Peters JM, Nasmyth K. Shugoshin prevents dissociation of cohesin from centromeres during mitosis in vertebrate cells. PLoS Biol 2005; 3:e86. [PMID: 15737064 PMCID: PMC1054882 DOI: 10.1371/journal.pbio.0030086] [Citation(s) in RCA: 272] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Accepted: 12/20/2004] [Indexed: 11/19/2022] Open
Abstract
Cohesion between sister chromatids is essential for their bi-orientation on mitotic spindles. It is mediated by a multisubunit complex called cohesin. In yeast, proteolytic cleavage of cohesin's alpha kleisin subunit at the onset of anaphase removes cohesin from both centromeres and chromosome arms and thus triggers sister chromatid separation. In animal cells, most cohesin is removed from chromosome arms during prophase via a separase-independent pathway involving phosphorylation of its Scc3-SA1/2 subunits. Cohesin at centromeres is refractory to this process and persists until metaphase, whereupon its alpha kleisin subunit is cleaved by separase, which is thought to trigger anaphase. What protects centromeric cohesin from the prophase pathway? Potential candidates are proteins, known as shugoshins, that are homologous to Drosophila MEI-S332 and yeast Sgo1 proteins, which prevent removal of meiotic cohesin complexes from centromeres at the first meiotic division. A vertebrate shugoshin-like protein associates with centromeres during prophase and disappears at the onset of anaphase. Its depletion by RNA interference causes HeLa cells to arrest in mitosis. Most chromosomes bi-orient on a metaphase plate, but precocious loss of centromeric cohesin from chromosomes is accompanied by loss of all sister chromatid cohesion, the departure of individual chromatids from the metaphase plate, and a permanent cell cycle arrest, presumably due to activation of the spindle checkpoint. Remarkably, expression of a version of Scc3-SA2 whose mitotic phosphorylation sites have been mutated to alanine alleviates the precocious loss of sister chromatid cohesion and the mitotic arrest of cells lacking shugoshin. These data suggest that shugoshin prevents phosphorylation of cohesin's Scc3-SA2 subunit at centromeres during mitosis. This ensures that cohesin persists at centromeres until activation of separase causes cleavage of its alpha kleisin subunit. Centromeric cohesion is one of the hallmarks of mitotic chromosomes. Our results imply that it is not an intrinsically stable property, because it can easily be destroyed by mitotic kinases, which are kept in check by shugoshin.
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Affiliation(s)
| | - Toru Hirota
- 1Research Institute of Molecular PathologyViennaAustria
| | | | | | - Kim Nasmyth
- 1Research Institute of Molecular PathologyViennaAustria
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174
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Abstract
In addition to the role in the spindle apparatus and associated motors, the chromosome themselves play an important role in facilitating chromosome segregation. Sister chromatids are joined at the centromere through a protein complex called cohesin. Chromatids separation requires the degradation by separase of specific proteins acting as a glue to form the cohesin complex. This evolutionally complex is required for the establishment and maintenance of sister chromatids in a ring like structure. It is therefore a key question whether cohesin is indeed a main component of active centromere. Cohesin is insufficient to resist the splitting force exerted by microtubules until anaphase and must be renforced by cohesion provided by flanking DNA. The ring model suggests that cohesine might possess a considerable mobility when associated with chromatin. Observations demonstrate that the interior region of the centromere behaves as an elastic element. Chromosomes display remarkable elasticity, returning to their initial shape after being extended by up to 10 times. For larger deformations the thick filament is converted in thin filament which can be stretched six times before breaking. This article suggests an additional and novel role for the protein titin on chromosome structure and dynamic. Titine was identified as a chromosomal component and it was hypothesised that titin may provide elasticity to chromosome and resistance to chromosome breakages during mitosis. The elastic properties of purified titin correspond well to the elastic properties of chromosome in living cells. The deformability and bending rigidity are consistent with a model developed for titin elasticity. The association of the presence of cohesine ring and the activity of titin could be necessary for segregation.
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Affiliation(s)
- Jean-Pierre Labbé
- Groupe d'études des transcriptomes, Institut de génétique humaine du CNRS, 141, rue de la Cardonille, 34396 Montpellier Cedex 5, France.
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175
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Pearson CG, Yeh E, Gardner M, Odde D, Salmon ED, Bloom K. Stable kinetochore-microtubule attachment constrains centromere positioning in metaphase. Curr Biol 2005; 14:1962-7. [PMID: 15530400 DOI: 10.1016/j.cub.2004.09.086] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 08/16/2004] [Accepted: 08/17/2004] [Indexed: 10/26/2022]
Abstract
With a single microtubule attachment, budding-yeast kinetochores provide an excellent system for understanding the coordinated linkage to dynamic microtubule plus ends for chromosome oscillation and positioning. Fluorescent tagging of kinetochore proteins indicates that, on average, all centromeres are clustered, distinctly separated from their sisters, and positioned equidistant from their respective spindle poles during metaphase. However, individual fluorescent chromosome markers near the centromere transiently reassociate with their sisters and oscillate from one spindle half to the other. To reconcile the apparent disparity between the average centromere position and individual centromere proximal markers, we utilized fluorescence recovery after photobleaching to measure stability of the histone-H3 variant Cse4p/CENP-A. Newly synthesized Cse4p replaces old protein during DNA replication. Once assembled, Cse4-GFP is a physically stable component of centromeres during mitosis. This allowed us to follow centromere dynamics within each spindle half. Kinetochores remain stably attached to dynamic microtubules and exhibit a low incidence of switching orientation or position between the spindle halves. Switching of sister chromatid attachment may be contemporaneous with Cse4p exchange and early kinetochore assembly during S phase; this would promote mixing of chromosome attachment to each spindle pole. Once biorientation is attained, centromeres rarely make excursions beyond their proximal half spindle.
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Affiliation(s)
- Chad G Pearson
- Department of Biology, University of North Carolina at Chapel Hill, Coker Hall Call Box #3280, Chapel Hill, NC 27599, USA
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176
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Gygax SE, Semighini CP, Goldman GH, Harris SD. SepBCTF4 is required for the formation of DNA-damage-induced UvsCRAD51 foci in Aspergillus nidulans. Genetics 2005; 169:1391-402. [PMID: 15654119 PMCID: PMC1449558 DOI: 10.1534/genetics.104.030817] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
SepB is an essential, conserved protein required for chromosomal DNA metabolism in Aspergillus nidulans. Homologs of SepB include yeast Ctf4p and human hAnd-1. Molecular and bioinformatic characterization of these proteins suggests that they act as molecular scaffolds. Furthermore, recent observations implicate the yeast family members in lagging-strand replication and the establishment of sister-chromatid cohesion. Here, we demonstrate that SepB functions in the A. nidulans DNA damage response. In particular, analysis of double mutants reveals that SepB is a member of the UvsC(RAD51) epistasis group. In accord with this prediction, we show that UvsC(RAD51) forms DNA-damage-induced nuclear foci in a manner that requires SepB function. We also provide evidence that implicates SepB in sister-chromatid cohesion, thereby suggesting that cohesion may play a role in regulating the localization and/or assembly of UvsC(RAD51) complexes.
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Affiliation(s)
- Scott E Gygax
- Department of Microbiology, University of Connecticut Health Center, Farmington, 06030-3205, USA.
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177
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Higuchi T, Uhlmann F. Stabilization of microtubule dynamics at anaphase onset promotes chromosome segregation. Nature 2005; 433:171-6. [PMID: 15650742 PMCID: PMC2586334 DOI: 10.1038/nature03240] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Accepted: 11/29/2004] [Indexed: 11/09/2022]
Abstract
Microtubules of the mitotic spindle form the structural basis for chromosome segregation. In metaphase, microtubules show high dynamic instability, which is thought to aid the 'search and capture' of chromosomes for bipolar alignment on the spindle. Microtubules suddenly become more stable at the onset of anaphase, but how this change in microtubule behaviour is regulated and how important it is for the ensuing chromosome segregation are unknown. Here we show that in the budding yeast Saccharomyces cerevisiae, activation of the phosphatase Cdc14 at anaphase onset is both necessary and sufficient for silencing microtubule dynamics. Cdc14 is activated by separase, the protease that triggers sister chromatid separation, linking the onset of anaphase to microtubule stabilization. If sister chromatids separate in the absence of Cdc14 activity, microtubules maintain high dynamic instability; this correlates with defects in both the movement of chromosomes to the spindle poles (anaphase A) and the elongation of the anaphase spindle (anaphase B). Cdc14 promotes localization of microtubule-stabilizing proteins to the anaphase spindle, and dephosphorylation of the kinetochore component Ask1 contributes to both the silencing of microtubule turnover and successful anaphase A.
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Affiliation(s)
- Toru Higuchi
- Chromosome Segregation Laboratory, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, UK
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178
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Abstract
Kinetochores are the major point of contact between spindle microtubules and chromosomes. They are assemblies of more than 50 different proteins and take part in regulating and controlling their own interaction with the spindle. We review recent advance in understanding how kinetochores are properly placed onto the chromosome, and how their interaction with the microtubules of the spindle is regulated. Kinetochore orientation in meiosis I shows some particular features, and we also discuss similarities and differences between mitosis and meiosis I.
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Affiliation(s)
- Silke Hauf
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi, Bunkyo-Ku, Tokyo 113-0032, Japan.
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179
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Affiliation(s)
- Randy Strich
- Program for Cell and Developmental Biology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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180
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Uzawa S, Li F, Jin Y, McDonald KL, Braunfeld MB, Agard DA, Cande WZ. Spindle pole body duplication in fission yeast occurs at the G1/S boundary but maturation is blocked until exit from S by an event downstream of cdc10+. Mol Biol Cell 2004; 15:5219-30. [PMID: 15385623 PMCID: PMC532005 DOI: 10.1091/mbc.e04-03-0255] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The regulation and timing of spindle pole body (SPB) duplication and maturation in fission yeast was examined by transmission electron microscopy. When cells are arrested at G1 by nitrogen starvation, the SPB is unduplicated. On release from G1, the SPBs were duplicated after 1-2 h. In cells arrested at S by hydroxyurea, SPBs are duplicated but not mature. In G1 arrest/release experiments with cdc2.33 cells at the restrictive temperature, SPBs remained single, whereas in cells at the permissive temperature, SPBs were duplicated. In cdc10 mutant cells, the SPBs seem not only to be duplicated but also to undergo partial maturation, including invagination of the nuclear envelope underneath the SPB. There may be an S-phase-specific inhibitor of SPB maturation whose expression is under control of cdc10(+). This model was examined by induction of overreplication of the genome by overexpression of rum1p or cdc18p. In cdc18p-overexpressing cells, the SPBs are duplicated but not mature, suggesting that cdc18p is one component of this feedback mechanism. In contrast, cells overexpressing rum1p have large, deformed SPBs accompanied by other features of maturation and duplication. We propose a feedback mechanism for maturation of the SPB that is coupled with exit from S to trigger morphological changes.
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Affiliation(s)
- Satoru Uzawa
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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181
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Glynn EF, Megee PC, Yu HG, Mistrot C, Unal E, Koshland DE, DeRisi JL, Gerton JL. Genome-wide mapping of the cohesin complex in the yeast Saccharomyces cerevisiae. PLoS Biol 2004; 2:E259. [PMID: 15309048 PMCID: PMC490026 DOI: 10.1371/journal.pbio.0020259] [Citation(s) in RCA: 334] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Accepted: 05/14/2004] [Indexed: 11/19/2022] Open
Abstract
In eukaryotic cells, cohesin holds sister chromatids together until they separate into daughter cells during mitosis. We have used chromatin immunoprecipitation coupled with microarray analysis (ChIP chip) to produce a genome-wide description of cohesin binding to meiotic and mitotic chromosomes of Saccharomyces cerevisiae. A computer program, PeakFinder, enables flexible, automated identification and annotation of cohesin binding peaks in ChIP chip data. Cohesin sites are highly conserved in meiosis and mitosis, suggesting that chromosomes share a common underlying structure during different developmental programs. These sites occur with a semiperiodic spacing of 11 kb that correlates with AT content. The number of sites correlates with chromosome size; however, binding to neighboring sites does not appear to be cooperative. We observed a very strong correlation between cohesin sites and regions between convergent transcription units. The apparent incompatibility between transcription and cohesin binding exists in both meiosis and mitosis. Further experiments reveal that transcript elongation into a cohesin-binding site removes cohesin. A negative correlation between cohesin sites and meiotic recombination sites suggests meiotic exchange is sensitive to the chromosome structure provided by cohesin. The genome-wide view of mitotic and meiotic cohesin binding provides an important framework for the exploration of cohesins and cohesion in other genomes.
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Affiliation(s)
- Earl F Glynn
- 1Stowers Institute for Medical Research, Kansas CityMissouri, United States of America
| | - Paul C Megee
- 2Department of Biochemistry and Molecular Genetics, University of ColoradoDenver, Colorado, United States of America
| | - Hong-Guo Yu
- 3Howard Hughes Medical Institute, Department of EmbryologyCarnegie Institution of Washington, Baltimore, Maryland, United States of America
| | - Cathy Mistrot
- 3Howard Hughes Medical Institute, Department of EmbryologyCarnegie Institution of Washington, Baltimore, Maryland, United States of America
| | - Elcin Unal
- 3Howard Hughes Medical Institute, Department of EmbryologyCarnegie Institution of Washington, Baltimore, Maryland, United States of America
| | - Douglas E Koshland
- 3Howard Hughes Medical Institute, Department of EmbryologyCarnegie Institution of Washington, Baltimore, Maryland, United States of America
| | - Joseph L DeRisi
- 4Department of Biochemistry and Biophysics, University of CaliforniaSan Francisco, CaliforniaUnited States of America
| | - Jennifer L Gerton
- 1Stowers Institute for Medical Research, Kansas CityMissouri, United States of America
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182
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Weber SA, Gerton JL, Polancic JE, DeRisi JL, Koshland D, Megee PC. The kinetochore is an enhancer of pericentric cohesin binding. PLoS Biol 2004; 2:E260. [PMID: 15309047 PMCID: PMC490027 DOI: 10.1371/journal.pbio.0020260] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Accepted: 05/14/2004] [Indexed: 11/18/2022] Open
Abstract
The recruitment of cohesins to pericentric chromatin in some organisms appears to require heterochromatin associated with repetitive DNA. However, neocentromeres and budding yeast centromeres lack flanking repetitive DNA, indicating that cohesin recruitment occurs through an alternative pathway. Here, we demonstrate that all budding yeast chromosomes assemble cohesin domains that extend over 20-50 kb of unique pericentric sequences flanking the conserved 120-bp centromeric DNA. The assembly of these cohesin domains requires the presence of a functional kinetochore in every cell cycle. A similar enhancement of cohesin binding was also observed in regions flanking an ectopic centromere. At both endogenous and ectopic locations, the centromeric enhancer amplified the inherent levels of cohesin binding that are unique to each region. Thus, kinetochores are enhancers of cohesin association that act over tens of kilobases to assemble pericentric cohesin domains. These domains are larger than the pericentric regions stretched by microtubule attachments, and thus are likely to counter microtubule-dependent forces. Kinetochores mediate two essential segregation functions: chromosome movement through microtubule attachment and biorientation of sister chromatids through the recruitment of high levels of cohesin to pericentric regions. We suggest that the coordination of chromosome movement and biorientation makes the kinetochore an autonomous segregation unit.
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Affiliation(s)
- Stewart A Weber
- 1Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center at FitzsimonsAurora, Colorado, United States of America
| | | | - Joan E Polancic
- 1Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center at FitzsimonsAurora, Colorado, United States of America
| | - Joseph L DeRisi
- 3Department of Biochemistry and Biophysics, University of CaliforniaSan Francisco, California, United States of America
| | - Douglas Koshland
- 4Howard Hughes Medical Institute, Department of EmbryologyCarnegie Institution of Washington, Baltimore, MarylandUnited States of America
| | - Paul C Megee
- 1Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center at FitzsimonsAurora, Colorado, United States of America
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183
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De La Fuente R, Viveiros MM, Wigglesworth K, Eppig JJ. ATRX, a member of the SNF2 family of helicase/ATPases, is required for chromosome alignment and meiotic spindle organization in metaphase II stage mouse oocytes. Dev Biol 2004; 272:1-14. [PMID: 15242786 DOI: 10.1016/j.ydbio.2003.12.012] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2003] [Revised: 11/21/2003] [Accepted: 12/03/2003] [Indexed: 10/26/2022]
Abstract
ATRX is a centromeric heterochromatin binding protein belonging to the SNF2 family of helicase/ATPases with chromatin remodeling activity. Mutations in the human ATRX gene result in X-linked alpha-thalassaemia with mental retardation (ATRX) syndrome and correlate with changes in methylation of repetitive DNA sequences. We show here that ATRX also functions to regulate key stages of meiosis in mouse oocytes. At the germinal vesicle (GV) stage, ATRX was found associated with the perinucleolar heterochromatin rim in transcriptionally quiescent oocytes. Phosphorylation of ATRX during meiotic maturation is dependent upon calcium calmodulin kinase (CamKII) activity. Meiotic resumption also coincides with deacetylation of histone H4 at lysine 5 (H4K5 Ac) while ATRX and histone H3 methylated on lysine 9 (H3K9) remained bound to the centromeres and interstitial regions of condensing chromosomes, respectively. Inhibition of histone deacetylases (HDACs) with trichostatin A (TSA) disrupted ATRX binding to the centromeres of hyperacetylated chromosomes resulting in abnormal chromosome alignments at metaphase II (MII). Similarly, while selective ablation of ATRX by antibody microinjection and RNA interference (RNAi) had no effect on the progression of meiosis, it had severe consequences for the alignment of chromosomes on the metaphase II spindle. These results suggest that genome-wide epigenetic modifications such as global histone deacetylation are essential for the binding of ATRX to centromeric heterochromatin. Moreover, centromeric ATRX is required for correct chromosome alignment and organization of a bipolar meiotic metaphase II spindle.
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184
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Lengronne A, Katou Y, Mori S, Yokobayashi S, Kelly GP, Itoh T, Watanabe Y, Shirahige K, Uhlmann F. Cohesin relocation from sites of chromosomal loading to places of convergent transcription. Nature 2004; 430:573-8. [PMID: 15229615 PMCID: PMC2610358 DOI: 10.1038/nature02742] [Citation(s) in RCA: 451] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Accepted: 06/11/2004] [Indexed: 11/08/2022]
Abstract
Sister chromatids, the products of eukaryotic DNA replication, are held together by the chromosomal cohesin complex after their synthesis. This allows the spindle in mitosis to recognize pairs of replication products for segregation into opposite directions. Cohesin forms large protein rings that may bind DNA strands by encircling them, but the characterization of cohesin binding to chromosomes in vivo has remained vague. We have performed high resolution analysis of cohesin association along budding yeast chromosomes III-VI. Cohesin localizes almost exclusively between genes that are transcribed in converging directions. We find that active transcription positions cohesin at these sites, not the underlying DNA sequence. Cohesin is initially loaded onto chromosomes at separate places, marked by the Scc2/Scc4 cohesin loading complex, from where it appears to slide to its more permanent locations. But even after sister chromatid cohesion is established, changes in transcription lead to repositioning of cohesin. Thus the sites of cohesin binding and therefore probably sister chromatid cohesion, a key architectural feature of mitotic chromosomes, display surprising flexibility. Cohesin localization to places of convergent transcription is conserved in fission yeast, suggesting that it is a common feature of eukaryotic chromosomes.
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Affiliation(s)
- Armelle Lengronne
- Chromosome Segregation Laboratory, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, UK
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185
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Petronczki M, Chwalla B, Siomos MF, Yokobayashi S, Helmhart W, Deutschbauer AM, Davis RW, Watanabe Y, Nasmyth K. Sister-chromatid cohesion mediated by the alternative RF-CCtf18/Dcc1/Ctf8, the helicase Chl1 and the polymerase-α-associated protein Ctf4 is essential for chromatid disjunction during meiosis II. J Cell Sci 2004; 117:3547-59. [PMID: 15226378 DOI: 10.1242/jcs.01231] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Cohesion between sister chromatids mediated by a multisubunit complex called cohesin is established during DNA replication and is essential for the orderly segregation of chromatids during anaphase. In budding yeast, a specialized replication factor C called RF-CCtf18/Dcc1/Ctf8 and the DNA-polymerase-α-associated protein Ctf4 are required to maintain sister-chromatid cohesion in cells arrested for long periods in mitosis. We show here that CTF8, CTF4 and a helicase encoded by CHL1 are required for efficient sister chromatid cohesion in unperturbed mitotic cells, and provide evidence that Chl1 functions during S-phase. We also show that, in contrast to mitosis, RF-CCtf18/Dcc1/Cft8, Ctf4 and Chl1 are essential for chromosome segregation during meiosis and for the viability of meiotic products. Our finding that cells deleted for CTF8, CTF4 or CHL1 undergo massive meiosis II non-disjunction suggests that the second meiotic division is particularly sensitive to cohesion defects. Using a functional as well as a cytological assay, we demonstrate that CTF8, CHL1 and CTF4 are essential for cohesion between sister centromeres during meiosis but dispensable for cohesin's association with centromeric DNA. Our finding that mutants in fission yeast ctf18 and dcc1 have similar defects suggests that the involvement of the alternative RF-CCtf18/Dcc1/Ctf8 complex in sister chromatid cohesion might be highly conserved.
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Affiliation(s)
- Mark Petronczki
- Research Institute of Molecular Pathology, Dr. Bohrgasse 7, A-1030 Vienna, Austria
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186
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Huang J, Hsu JM, Laurent BC. The RSC nucleosome-remodeling complex is required for Cohesin's association with chromosome arms. Mol Cell 2004; 13:739-50. [PMID: 15023343 DOI: 10.1016/s1097-2765(04)00103-0] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Revised: 01/12/2004] [Accepted: 01/13/2004] [Indexed: 11/17/2022]
Abstract
The fidelity of chromosome segregation requires that the cohesin protein complex bind together newly replicated sister chromatids both at centromeres and at discrete sites along chromosome arms. Segregation of the yeast 2 micro plasmid also requires cohesin, which is recruited to the plasmid partitioning locus. Here we report that the RSC chromatin-remodeling complex regulates the differential association of cohesin with centromeres and chromosome arms. RSC cycles on and off chromosomal arm and plasmid cohesin binding sites in a cell cycle-regulated manner 15 min preceding Mcd1p, the central cohesin subunit. We show that in rsc mutants Mcd1p fails to associate with chromosome arms but still binds to centromeres, and that consequently, the arm regions of mitotic sister chromosomes separate precociously while cohesion at centromeres is unaffected. Our data suggest a role for RSC in facilitating the loading of cohesin specifically onto chromosome arms, thereby ensuring sister chromatid cohesion and proper chromosome segregation.
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Affiliation(s)
- Jian Huang
- Program in Molecular and Cellular Biology, Department of Microbiology and Immunology, Morse Institute of Molecular Biology and Genetics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
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187
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Baetz KK, Krogan NJ, Emili A, Greenblatt J, Hieter P. The ctf13-30/CTF13 genomic haploinsufficiency modifier screen identifies the yeast chromatin remodeling complex RSC, which is required for the establishment of sister chromatid cohesion. Mol Cell Biol 2004; 24:1232-44. [PMID: 14729968 PMCID: PMC321452 DOI: 10.1128/mcb.24.3.1232-1244.2003] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The budding yeast centromere-kinetochore complex ensures high-fidelity chromosome segregation in mitosis and meiosis by mediating the attachment and movement of chromosomes along spindle microtubules. To identify new genes and pathways whose function impinges on chromosome transmission, we developed a genomic haploinsufficiency modifier screen and used ctf13-30, encoding a mutant core kinetochore protein, as the reference point. We demonstrate through a series of secondary screens that the genomic modifier screen is a successful method for identifying genes that encode nonessential proteins required for the fidelity of chromosome segregation. One gene isolated in our screen was RSC2, a nonessential subunit of the RSC chromatin remodeling complex. rsc2 mutants have defects in both chromosome segregation and cohesion, but the localization of kinetochore proteins to centromeres is not affected. We determined that, in the absence of RSC2, cohesin could still associate with chromosomes but fails to achieve proper cohesion between sister chromatids, indicating that RSC has a role in the establishment of cohesion. In addition, numerous subunits of RSC were affinity purified and a new component of RSC, Rtt102, was identified. Our work indicates that only a subset of the nonessential RSC subunits function in maintaining chromosome transmission fidelity.
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Affiliation(s)
- Kristin K Baetz
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4
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188
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Abstract
Kinetochores are multiprotein complexes that assemble on centromeric DNA and mediate the attachment and movement of chromosomes along the microtubules (MTs) of the mitotic spindle. This review focuses on the simplest eukaryotic centromeres and kinetochores, those found in the budding yeast Saccharomyces cerevisiae. Research on kinetochore function and chromosome segregation is focused on four questions of general significance: what specifies the location of centromeres? What are the protein components of kinetochores, and how do they assemble a MT attachment site? How do MT attachments generate force? How do cells sense the state of attachment via the spindle assembly checkpoint?
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Affiliation(s)
- Andrew D McAinsh
- Department of Biology, and Biological Engineering Division, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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189
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Dewar H, Tanaka K, Nasmyth K, Tanaka TU. Tension between two kinetochores suffices for their bi-orientation on the mitotic spindle. Nature 2004; 428:93-7. [PMID: 14961024 DOI: 10.1038/nature02328] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2003] [Accepted: 01/12/2004] [Indexed: 11/09/2022]
Abstract
The movement of sister chromatids to opposite spindle poles during anaphase depends on the prior capture of sister kinetochores by microtubules with opposing orientations (amphitelic attachment or bi-orientation). In addition to proteins necessary for the kinetochore-microtubule attachment, bi-orientation requires the Ipl1 (Aurora B in animal cells) protein kinase and tethering of sister chromatids by cohesin. Syntelic attachments, in which sister kinetochores attach to microtubules with the same orientation, must be either 'avoided' or 'corrected'. Avoidance might be facilitated by the juxtaposition of sister kinetochores such that they face in opposite directions; kinetochore geometry is therefore deemed important. Error correction, by contrast, is thought to stem from the stabilization of kinetochore-spindle pole connections by tension in microtubules, kinetochores, or the surrounding chromatin arising from amphitelic but not syntelic attachment. The tension model predicts that any type of connection between two kinetochores suffices for efficient bi-orientation. Here we show that the two kinetochores of engineered, unreplicated dicentric chromosomes in Saccharomyces cerevisiae bi-orient efficiently, implying that sister kinetochore geometry is dispensable for bi-orientation. We also show that Ipl1 facilitates bi-orientation by promoting the turnover of kinetochore-spindle pole connections in a tension-dependent manner.
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Affiliation(s)
- Hilary Dewar
- School of Life Sciences, University of Dundee, Wellcome Trust Biocentre, Dundee DD1 5EH, UK
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190
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Vagnarelli P, Morrison C, Dodson H, Sonoda E, Takeda S, Earnshaw WC. Analysis of Scc1-deficient cells defines a key metaphase role of vertebrate cohesin in linking sister kinetochores. EMBO Rep 2004; 5:167-71. [PMID: 14749720 PMCID: PMC1298988 DOI: 10.1038/sj.embor.7400077] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2003] [Revised: 11/25/2003] [Accepted: 12/05/2003] [Indexed: 11/09/2022] Open
Abstract
Cleavage of the cohesin subunit Scc1p/Mcd1p/Rad21 permits sister chromatid separation and is considered to trigger anaphase onset. It has also been suggested that the cohesin complex is essential for chromosome condensation and for assembling fully functional kinetochores. Here, we used vertebrate cells conditionally deficient in Scc1 to probe cohesin function in mitosis. Cells lacking cohesin arrest in prometaphase, with many chromosomes failing to align at a metaphase plate and high levels of the spindle assembly checkpoint protein, BubR1, at all kinetochores. We show that the structural integrity of chromosomes is normal in the absence of Scc1. Furthermore, specific inhibition of topoisomerase II, which is required for decatenation of replicated chromosomes, can bypass the cohesin requirement for metaphase chromosome alignment and spindle checkpoint silencing. Since the kinetochore effects of Scc1 deficiency can be compensated for by topoisomerase II inhibition, we conclude that Scc1 is not absolutely required for kinetochore assembly or function, and that its principal role in allowing the onset of anaphase is the establishment of sufficient inter-sister tension to allow biorientation.
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Affiliation(s)
- Paola Vagnarelli
- Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, Swann Building, King's Buildings, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK
- These authors contributed equally to this work
| | - Ciaran Morrison
- Department of Biochemistry/NCBES, National University of Ireland-Galway, Ireland
- These authors contributed equally to this work
| | - Helen Dodson
- Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, Swann Building, King's Buildings, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK
| | - Eiichiro Sonoda
- CREST Research Project, Japan Science and Technology Corporation, Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Shunichi Takeda
- CREST Research Project, Japan Science and Technology Corporation, Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - William C Earnshaw
- Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, Swann Building, King's Buildings, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK
- CREST Research Project, Japan Science and Technology Corporation, Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
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191
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Nasmyth K, Schleiffer A. From a single double helix to paired double helices and back. Philos Trans R Soc Lond B Biol Sci 2004; 359:99-108. [PMID: 15065662 PMCID: PMC1693308 DOI: 10.1098/rstb.2003.1417] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The propagation of our genomes during cell proliferation depends on the movement of sister DNA molecules produced by DNA replication to opposite sides of the cell before it divides. This feat is achieved by microtubules in eukaryotic cells but it has long remained a mystery how cells ensure that sister DNAs attach to microtubules with opposite orientations, known as amphitelic attachment. It is currently thought that sister chromatid cohesion has a crucial role. By resisting the forces exerted by microtubules, sister chromatid cohesion gives rise to tension that is thought essential for stabilizing kinetochore-microtubule attachments. Efficient amphitelic attachment is therefore achieved by an error correction mechanism that selectively eliminates connections that do not give rise to tension. Cohesion between sister chromatids is mediated by a multisubunit complex called cohesin which forms a gigantic ring structure. It has been proposed that sister DNAs are held together owing to their becoming entrapped within a single cohesin ring. Cohesion between sister chromatids is destroyed at the metaphase to anaphase transition by proteolytic cleavage of cohesin's Scc1 subunit by a thiol protease called separase, which severs the ring and thereby releases sister DNAs.
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Affiliation(s)
- Kim Nasmyth
- Research Institute for Molecular Biology (IMP), Dr. Bohr-Gasse 7, A-1030 Vienna, Austria.
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192
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Rajagopalan S, Bimbo A, Balasubramanian MK, Oliferenko S. A Potential Tension-Sensing Mechanism that Ensures Timely Anaphase Onset upon Metaphase Spindle Orientation. Curr Biol 2004; 14:69-74. [PMID: 14711417 DOI: 10.1016/j.cub.2003.12.027] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The spindle orientation checkpoint (SOC) in fission yeast has been proposed to delay metaphase-to-anaphase transition when the spindle poles are misaligned with respect to the long axis of the cell. This checkpoint is activated in the absence of either an actomyosin division ring or astral microtubules. Although the SOC could be overridden in the absence of the transcription factor Atf1p, its mechanistic nature remained unclear. Here, we show that the SOC-triggered metaphase delay depends on a subset of the spindle assembly checkpoint (SAC) components Mph1p and Bub1p. Based on this finding and a detailed imaging of the spindle orientation process, we hypothesized that the spindle pole might contain proteins capable of sensing the achievement of spindle alignment. We identified the kendrin-like spindle pole body resident Pcp1p as a candidate molecule. A targeted mutation in its central domain specifically triggered the SOC in spite of the presence of oriented spindles, causing a metaphase delay that could be relieved in the absence of Mph1p, Bub1p, and Atf1p. Thus, Pcp1p might provide a link between the mechanical process of spindle alignment and the signal transduction that initiates anaphase.
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Affiliation(s)
- Srividya Rajagopalan
- Temasek Life Sciences Laboratory, 1 Research Link, The National University of Singapore, 117604, Republic of, Singapore, Singapore
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193
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Nekrasov VS, Smith MA, Peak-Chew S, Kilmartin JV. Interactions between centromere complexes in Saccharomyces cerevisiae. Mol Biol Cell 2003; 14:4931-46. [PMID: 14565975 PMCID: PMC284796 DOI: 10.1091/mbc.e03-06-0419] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We have purified two new complexes from Saccharomyces cerevisiae, one containing the centromere component Mtw1p together with Nnf1p, Nsl1p, and Dsn1p, which we call the Mtw1p complex, and the other containing Spc105p and Ydr532p, which we call the Spc105p complex. Further purifications using Dsn1p tagged with protein A show, in addition to the other components of the Mtw1p complex, the two components of the Spc105p complex and the four components of the previously described Ndc80p complex, suggesting that all three complexes are closely associated. Fluorescence microscopy and immunoelectron microscopy show that Nnf1p, Nsl1p, Dsn1p, Spc105p, and Ydr532p all localize to the nuclear side of the spindle pole body and along short spindles. Chromatin immunoprecipitation assays show that all five proteins are associated with centromere DNA. Homologues of Nsl1p and Spc105p in Schizosaccharomyces pombe also localize to the centromere. Temperature-sensitive mutations of Nsl1p, Dsn1p, and Spc105p all cause defects in chromosome segregation. Synthetic-lethal interactions are found between temperature-sensitive mutations in proteins from all three complexes, in agreement with their close physical association. These results show an increasingly complex structure for the S. cerevisiae centromere and a probable conservation of structure between parts of the centromeres of S. cerevisiae and S. pombe.
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194
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Pasierbek P, Födermayr M, Jantsch V, Jantsch M, Schweizer D, Loidl J. The Caenorhabditis elegans SCC-3 homologue is required for meiotic synapsis and for proper chromosome disjunction in mitosis and meiosis. Exp Cell Res 2003; 289:245-55. [PMID: 14499625 DOI: 10.1016/s0014-4827(03)00266-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The product of the Caenorhabditis elegans ORF F18E2.3 is homologous to the cohesin component Scc3p. By antibody staining the product of F18E2.3 is found in interphase and early meiotic nuclei. At pachytene it localizes to the axes of meiotic chromosomes but is no longer detectable on chromatin later in meiosis or in mitoses. Depletion of the gene product by RNAi results in aberrant mitoses and meioses. In meiosis, homologous pairing is defective during early meiotic prophase and at diakinesis there occur univalents consisting of loosely connected sister chromatids or completely separated sisters. The recombination protein RAD-51 accumulates in nuclear foci at higher numbers during meiotic prophase and disappears later than in wild-type worms, suggesting a defect in the repair of meiotic double-stranded DNA breaks. Embryos showing nuclei of variable size and anaphase bridges, indicative of mitotic segregation defects, are frequently observed. In the most severely affected gonads, nuclear morphology cannot be related to any specific stage. The cytological localization and the consequences of the lack of the protein indicate that C. elegans SCC-3 is essential for sister chromatid cohesion both in mitosis and in meiosis.
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Affiliation(s)
- Pawel Pasierbek
- Institute of Botany, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
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195
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Pearson CG, Maddox PS, Zarzar TR, Salmon ED, Bloom K. Yeast kinetochores do not stabilize Stu2p-dependent spindle microtubule dynamics. Mol Biol Cell 2003; 14:4181-95. [PMID: 14517328 PMCID: PMC207010 DOI: 10.1091/mbc.e03-03-0180] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The interaction of kinetochores with dynamic microtubules during mitosis is essential for proper centromere motility, congression to the metaphase plate, and subsequent anaphase chromosome segregation. Budding yeast has been critical in the discovery of proteins necessary for this interaction. However, the molecular mechanism for microtubule-kinetochore interactions remains poorly understood. Using live cell imaging and mutations affecting microtubule binding proteins and kinetochore function, we identify a regulatory mechanism for spindle microtubule dynamics involving Stu2p and the core kinetochore component, Ndc10p. Depleting cells of the microtubule binding protein Stu2p reduces kinetochore microtubule dynamics. Centromeres remain under tension but lack motility. Thus, normal microtubule dynamics are not required to maintain tension at the centromere. Loss of the kinetochore (ndc10-1, ndc10-2, and ctf13-30) does not drastically affect spindle microtubule turnover, indicating that Stu2p, not the kinetochore, is the foremost governor of microtubule dynamics. Disruption of kinetochore function with ndc10-1 does not affect the decrease in microtubule turnover in stu2 mutants, suggesting that the kinetochore is not required for microtubule stabilization. Remarkably, a partial kinetochore defect (ndc10-2) suppresses the decreased spindle microtubule turnover in the absence of Stu2p. These results indicate that Stu2p and Ndc10p differentially function in controlling kinetochore microtubule dynamics necessary for centromere movements.
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Affiliation(s)
- Chad G Pearson
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280, USA.
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196
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Abstract
Two related protein complexes, cohesin and condensin, are essential for separating identical copies of the genome into daughter cells during cell division. Cohesin glues replicated sister chromatids together until they split at anaphase, whereas condensin reorganizes chromosomes into their highly compact mitotic structure. Unexpectedly, mutations in the subunits of these complexes have been uncovered in genetic screens that target completely different processes. Exciting new evidence is emerging that cohesin and condensin influence crucial processes during interphase, and unforeseen aspects of mitosis. Each complex can perform several roles, and individual subunits can associate with different sets of proteins to achieve diverse functions, including the regulation of gene expression, DNA repair, cell-cycle checkpoints and centromere organization.
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Affiliation(s)
- Kirsten A Hagstrom
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720-3204, USA.
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197
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Loidl J. Chromosomes of the budding yeast Saccharomyces cerevisiae. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 222:141-96. [PMID: 12503849 DOI: 10.1016/s0074-7696(02)22014-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The mitotic chromosomes of the baker's yeast, Saccharomyces cerevisiae, cannot be visualized by standard cytological methods. Only the study of meiotic bivalents and the synaptonemal complex and the visualization of chromosome-sized DNA molecules on pulsed-field gels have provided some insight into chromosome structure and behavior. More recently, advanced techniques such as in situ hybridization, the illumination of chromosomal loci by GFP-tagged DNA-binding proteins, and immunostaining of chromosomal proteins have promoted our knowledge about yeast chromosomes. These novel cytological approaches in combination with the yeast's advanced biochemistry and genetics have produced a great wealth of information on the interplay between molecular and cytological processes and have strengthened the role of yeast as a leading cell biological model organism. Recent cytological studies have revealed much about the chromosomal organization in interphase nuclei and have contributed significantly to our current understanding of chromosome condensation, sister chromatid cohesion, and centromere orientation in mitosis. Moreover, important details about the biochemistry and ultrastructure of meiotic pairing and recombination have been revealed by combined cytological and molecular approaches. This article covers several aspects of yeast chromosome structure, including their organization within interphase nuclei and their behavior during mitosis and meiosis.
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Affiliation(s)
- Josef Loidl
- Institute of Botany, University of Vienna, A-1030 Vienna, Austria
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198
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Sprague BL, Pearson CG, Maddox PS, Bloom KS, Salmon ED, Odde DJ. Mechanisms of microtubule-based kinetochore positioning in the yeast metaphase spindle. Biophys J 2003; 84:3529-46. [PMID: 12770865 PMCID: PMC1302941 DOI: 10.1016/s0006-3495(03)75087-5] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
It has been hypothesized that spatial gradients in kMT dynamic instability facilitate mitotic spindle formation and chromosome movement. To test this hypothesis requires the analysis of kMT dynamics, which have not been resolved at the single kMT level in living cells. The budding yeast spindle offers an attractive system in which to study kMT dynamics because, in contrast to animal cells, there is only one kMT per kinetochore. To visualize metaphase kMT plus-end dynamics in yeast, a strain containing a green fluorescent protein fusion to the kinetochore protein, Cse4, was imaged by fluorescence microscopy. Although individual kinetochores were not resolvable, we found that models of kMT dynamics could be evaluated by simulating the stochastic kMT dynamics and then simulating the fluorescence imaging of kMT plus-end-associated kinetochores. Statistical comparison of model-predicted images to experimentally observed images demonstrated that a pure dynamic instability model for kMT dynamics in the yeast metaphase spindle was unacceptable. However, when a temporally stable spatial gradient in the catastrophe or rescue frequency was added to the model, there was reasonable agreement between the model and the experiment. These results provide the first evidence of temporally stable spatial gradients of kMT catastrophe and/or rescue frequency in living cells.
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Affiliation(s)
- Brian L Sprague
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
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199
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Abstract
Spindle microtubules interact with mitotic chromosomes, binding to their kinetochores to generate forces that are important for accurate chromosome segregation. Motor enzymes localized both at kinetochores and spindle poles help to form the biologically significant attachments between spindle fibers and their cargo, but microtubule-associated proteins without motor activity contribute to these junctions in important ways. This review examines the molecules necessary for chromosome-microtubule interaction in a range of well-studied organisms, using biological diversity to identify the factors that are essential for organized chromosome movement. We conclude that microtubule dynamics and the proteins that control them are likely to be more important for mitosis than the current enthusiasm for motor enzymes would suggest.
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Affiliation(s)
- J Richard McIntosh
- Department of Molecular Cellular and Developmental Biology, University of Colorado, Boulder 80309-0347, USA.
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200
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Abstract
Accurate chromosome segregation is essential to ensure genomic stability because the aneuploidy that results from segregation errors leads to birth defects and contributes to the development of cancer. Chromosome segregation is directed by the kinetochore, the chromosomal site of attachment to dynamic polymers called microtubules (MTs). Although the fidelity of chromosome segregation depends on precise interactions between kinetochores and MTs, it is still unclear how this interaction is mediated and regulated. Here we discuss current progress in determining how kinetochores assemble and attach to MTs during mitosis as well as how they correct errors.
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Affiliation(s)
- Sue Biggins
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, PO Box 19024, 1100 Fairview Ave. North, A2-168, Seattle, WA 98109-1024, USA.
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