Acetylation regulates monopolar attachment at multiple levels during meiosis I in fission yeast

Abstract Kinetochores are protein complexes on the chromosomes, whose function as linkers between spindle microtubules and chromosomes is crucial for proper cell division. The mechanisms that facilitate kinetochore capture by microtubules are still unclear. In the present study, we combine experiments and theory to explore the mechanisms of kinetochore capture at the onset of meiosis I in fission yeast. We show that kinetochores on homologous chromosomes move together, microtubules are dynamic and pivot around the spindle pole, and the average capture time is 3–4 minutes. Our theory describes paired kinetochores on homologous chromosomes as a single object, as well as angular movement of microtubules and their dynamics. For the experimentally measured parameters, the model reproduces the measured capture kinetics and shows that the paired configuration of kinetochores accelerates capture, whereas microtubule pivoting and dynamics have a smaller contribution. Kinetochore pairing may be a general feature that increases capture efficiency in meiotic cells.

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Nup132 modulates meiotic spindle attachment in fission yeast by regulating kinetochore assembly

The Journal of Cell Biology ◽

10.1083/jcb.201501035 ◽

2015 ◽

Vol 211 (2) ◽

pp. 295-308 ◽

Cited By ~ 8

Author(s):

Hui-Ju Yang ◽

Haruhiko Asakawa ◽

Tokuko Haraguchi ◽

Yasushi Hiraoka

Keyword(s):

Schizosaccharomyces Pombe ◽

Fission Yeast ◽

Meiotic Prophase ◽

Spindle Assembly Checkpoint ◽

Meiotic Spindle ◽

Spindle Attachment ◽

Kinetochore Assembly ◽

Sister Chromatids ◽

Monopolar Spindle ◽

Meiosis I

During meiosis, the kinetochore undergoes substantial reorganization to establish monopolar spindle attachment. In the fission yeast Schizosaccharomyces pombe, the KNL1–Spc7-Mis12-Nuf2 (KMN) complex, which constitutes the outer kinetochore, is disassembled during meiotic prophase and is reassembled before meiosis I. Here, we show that the nucleoporin Nup132 is required for timely assembly of the KMN proteins: In the absence of Nup132, Mis12 and Spc7 are precociously assembled at the centromeres during meiotic prophase. In contrast, Nuf2 shows timely dissociation and reappearance at the meiotic centromeres. We further demonstrate that depletion of Nup132 activates the spindle assembly checkpoint in meiosis I, possibly because of the increased incidence of erroneous spindle attachment at sister chromatids. These results suggest that precocious assembly of the kinetochores leads to the meiosis I defects observed in the nup132-disrupted mutant. Thus, we propose that Nup132 plays an important role in establishing monopolar spindle attachment at meiosis I through outer kinetochore reorganization at meiotic prophase.

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Kinetochore-mediated outward force promotes spindle pole separation in fission yeast

Molecular Biology of the Cell ◽

10.1091/mbc.e19-07-0366 ◽

2019 ◽

Vol 30 (22) ◽

pp. 2802-2813 ◽

Cited By ~ 4

Author(s):

Yutaka Shirasugi ◽

Masamitsu Sato

Keyword(s):

Fission Yeast ◽

Motor Proteins ◽

Spindle Assembly ◽

Spindle Pole ◽

Double Knockout ◽

Bipolar Spindle ◽

Spindle Poles ◽

Bipolar Spindles ◽

Meiosis I

Bipolar spindles are organized by motor proteins that generate microtubule-dependent forces to separate the two spindle poles. The fission yeast Cut7 (kinesin-5) is a plus-end-directed motor that generates the outward force to separate the two spindle poles, whereas the minus-end-directed motor Pkl1 (kinesin-14) generates the inward force. Balanced forces by these antagonizing kinesins are essential for bipolar spindle organization in mitosis. Here, we demonstrate that chromosomes generate another outward force that contributes to the bipolar spindle assembly. First, it was noted that the cut7 pkl1 double knockout failed to separate spindle poles in meiosis I, although the mutant is known to succeed it in mitosis. It was assumed that this might be because meiotic kinetochores of bivalent chromosomes joined by cross-overs generate weaker tensions in meiosis I than the strong tensions in mitosis generated by tightly tethered sister kinetochores. In line with this idea, when meiotic mono-oriented kinetochores were artificially converted to a mitotic bioriented layout, the cut7 pkl1 mutant successfully separated spindle poles in meiosis I. Therefore, we propose that spindle pole separation is promoted by outward forces transmitted from kinetochores to spindle poles through microtubules.

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Spindle checkpoint activation at meiosis I advances anaphase II onset via meiosis-specific APC/C regulation

The Journal of Cell Biology ◽

10.1083/jcb.200802053 ◽

2008 ◽

Vol 182 (2) ◽

pp. 277-288 ◽

Cited By ~ 24

Author(s):

Ayumu Yamamoto ◽

Kenji Kitamura ◽

Daisuke Hihara ◽

Yukinobu Hirose ◽

Satoshi Katsuyama ◽

...

Keyword(s):

Protein Degradation ◽

Fission Yeast ◽

Chromosome Segregation ◽

Spindle Assembly Checkpoint ◽

Related Factor ◽

Anaphase Promoting Complex ◽

Checkpoint Activation ◽

Anaphase Onset ◽

Yeast Meiosis ◽

Meiosis I

During mitosis, the spindle assembly checkpoint (SAC) inhibits the Cdc20-activated anaphase-promoting complex/cyclosome (APC/CCdc20), which promotes protein degradation, and delays anaphase onset to ensure accurate chromosome segregation. However, the SAC function in meiotic anaphase regulation is poorly understood. Here, we examined the SAC function in fission yeast meiosis. As in mitosis, a SAC factor, Mad2, delayed anaphase onset via Slp1 (fission yeast Cdc20) when chromosomes attach to the spindle improperly. However, when the SAC delayed anaphase I, the interval between meiosis I and II shortened. Furthermore, anaphase onset was advanced and the SAC effect was reduced at meiosis II. The advancement of anaphase onset depended on a meiosis-specific, Cdc20-related factor, Fzr1/Mfr1, which contributed to anaphase cyclin decline and anaphase onset and was inefficiently inhibited by the SAC. Our findings show that impacts of SAC activation are not confined to a single division at meiosis due to meiosis-specific APC/C regulation, which has probably been evolved for execution of two meiotic divisions.

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Rec8p, a Meiotic Recombination and Sister Chromatid Cohesion Phosphoprotein of the Rad21p Family Conserved from Fission Yeast to Humans

Molecular and Cellular Biology ◽

10.1128/mcb.19.5.3515 ◽

1999 ◽

Vol 19 (5) ◽

pp. 3515-3528 ◽

Cited By ~ 144

Author(s):

Sandro Parisi ◽

Michael J. McKay ◽

Monika Molnar ◽

M. Anne Thompson ◽

Peter J. van der Spek ◽

...

Keyword(s):

Fission Yeast ◽

Sister Chromatid ◽

Germ Line ◽

Sequence Similarity ◽

Sister Chromatid Cohesion ◽

Specific Expression ◽

Chromatid Cohesion ◽

Prophase Nucleus ◽

Chromosome Iii ◽

Meiosis I

ABSTRACT Our work and that of others defined mitosis-specific (Rad21 subfamily) and meiosis-specific (Rec8 subfamily) proteins involved in sister chromatid cohesion in several eukaryotes, including humans. Mutation of the fission yeast Schizosaccharomyces pombe rec8 gene was previously shown to confer a number of meiotic phenotypes, including strong reduction of recombination frequencies in the central region of chromosome III, absence of linear element polymerization, reduced pairing of homologous chromosomes, reduced sister chromatid cohesion, aberrant chromosome segregation, defects in spore formation, and reduced spore viability. Here we extend the description of recombination reduction to the central regions of chromosomes I and II. We show at the protein level that expression ofrec8 is meiosis specific and that Rec8p localizes to approximately 100 foci per prophase nucleus. Rec8p was present in an unphosphorylated form early in meiotic prophase but was phosphorylated prior to meiosis I, as demonstrated by analysis of the mei4mutant blocked before meiosis I. Evidence for the persistence of Rec8p beyond meiosis I was obtained by analysis of the mutantmes1 blocked before meiosis II. A human gene, which we designate hrec8, showed significant primary sequence similarity to rec8 and was mapped to chromosome 14. High mRNA expression of mouse and human rec8 genes was found only in germ line cells, specifically in testes and, interestingly, in spermatids. hrec8 was also expressed at a low level in the thymus. Sequence similarity and testis-specific expression indicate evolutionarily conserved functions of Rec8p in meiosis. Possible roles of Rec8p in the integration of different meiotic events are discussed.

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Cohesins Determine the Attachment Manner of Kinetochores to Spindle Microtubules at Meiosis I in Fission Yeast

Molecular and Cellular Biology ◽

10.1128/mcb.23.11.3965-3973.2003 ◽

2003 ◽

Vol 23 (11) ◽

pp. 3965-3973 ◽

Cited By ~ 76

Author(s):

Shihori Yokobayashi ◽

Masayuki Yamamoto ◽

Yoshinori Watanabe

Keyword(s):

Fission Yeast ◽

Chromosome Segregation ◽

Sister Chromatid ◽

Specific Requirement ◽

Spindle Poles ◽

Chromatid Cohesion ◽

Spindle Microtubules ◽

Yeast Meiosis ◽

Meiosis I ◽

Random Division

ABSTRACT During mitosis, sister kinetochores attach to microtubules that extend to opposite spindle poles (bipolar attachment) and pull the chromatids apart at anaphase (equational segregation). A multisubunit complex called cohesin, including Rad21/Scc1, plays a crucial role in sister chromatid cohesion and equational segregation at mitosis. Meiosis I differs from mitosis in having a reductional pattern of chromosome segregation, in which sister kinetochores are attached to the same spindle (monopolar attachment). During meiosis, Rad21/Scc1 is largely replaced by its meiotic counterpart, Rec8. If Rec8 is inactivated in fission yeast, meiosis I is shifted from reductional to equational division. However, the reason rec8Δ cells undergo equational rather than random division has not been clarified; therefore, it has been unclear whether equational segregation is due to a loss of cohesin in general or to a loss of a specific requirement for Rec8. We report here that the equational segregation at meiosis I depends on substitutive Rad21, which relocates to the centromeres if Rec8 is absent. Moreover, we demonstrate that even if sufficient amounts of Rad21 are transferred to the centromeres at meiosis I, thereby establishing cohesion at the centromeres, rec8Δ cells never recover monopolar attachment but instead secure bipolar attachment. Thus, Rec8 and Rad21 define monopolar and bipolar attachment, respectively, at meiosis I. We conclude that cohesin is a crucial determinant of the attachment manner of kinetochores to the spindle microtubules at meiosis I in fission yeast.

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Shugoshin 2 Regulates Localization of the Chromosomal Passenger Proteins in Fission Yeast Mitosis

Molecular Biology of the Cell ◽

10.1091/mbc.e06-10-0890 ◽

2007 ◽

Vol 18 (5) ◽

pp. 1657-1669 ◽

Cited By ~ 64

Author(s):

Vincent Vanoosthuyse ◽

Sergey Prykhozhij ◽

Kevin G. Hardwick

Keyword(s):

Fission Yeast ◽

Spindle Checkpoint ◽

Aurora B ◽

Checkpoint Activation ◽

C Terminus ◽

Chromosomal Passenger ◽

Chromosomal Passenger Proteins ◽

Passenger Proteins ◽

Meiosis I ◽

Mitotic Cells

Fission yeast has two members of the Shugoshin family, Sgo1 and Sgo2. Although Sgo1 has clearly been established as a protector of centromere cohesion in meiosis I, the roles of Sgo2 remain elusive. Here we show that Sgo2 is required to ensure proper chromosome biorientation upon recovery from a prolonged spindle checkpoint arrest. Consistent with this, Sgo2 is essential for maintaining the Passenger proteins on centromeres upon checkpoint activation. Interestingly, lack of Sgo2 has a more penetrant effect on the localization of Survivin than on the two other Passenger proteins INCENP and Aurora B, and the Survivin-INCENP complex but not the INCENP-Aurora B complex is destabilized in the absence of Sgo2. Finally we show that the conserved C-terminus of Sgo2 is crucial to maintain Sgo2 and Passenger proteins localization on centromeres upon prolonged checkpoint activation. Taken together, our results demonstrate that Sgo2 is important for chromosome biorientation and that it controls docking of the Passenger proteins on chromosomes in early mitotic cells.

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The Fission Yeast Meiotic Regulator Mei2p Forms a Dot Structure in the Horse-Tail Nucleus in Association with the sme2 Locus on Chromosome II

Molecular Biology of the Cell ◽

10.1091/mbc.e02-11-0738 ◽

2003 ◽

Vol 14 (6) ◽

pp. 2461-2469 ◽

Cited By ~ 47

Author(s):

Tadayuki Shimada ◽

Akira Yamashita ◽

Masayuki Yamamoto

Keyword(s):

Fission Yeast ◽

Dna Sequence ◽

Chromosome Segregation ◽

Rna Binding ◽

Rna Binding Protein ◽

Fixed Position ◽

Gene Translocation ◽

Specialized Structure ◽

Chromosome Ii ◽

Meiosis I

Fission yeast Mei2p is an RNA-binding protein essential for induction of both premeiotic DNA synthesis and first meiotic division. Mei2p forms a dot structure at an apparently fixed position in the horse-tail nucleus during meiotic prophase. This dot formation requires a meiosis-specific RNA species, meiRNA, which is indispensable for meiosis I, and the emergence of the dot is an indicator of the ability of the cell to perform meiosis I. Herein, we have sought the identity of this dot. Analyses using chromosome segregation in haploid meiosis, reciprocal translocation of chromosomes, and gene translocation have led us to conclude that the Mei2p dot is in association with the sme2 gene on the short arm of chromosome II, which encodes meiRNA. Transcripts of sme2, rather than the DNA sequence of the gene, seem to be the determinant of the localization of the Mei2p dot. However, evidence suggests that the dot may not be a simple reflection of the attachment of Mei2p to meiRNA undergoing transcription. We speculate that the Mei2p dot is a specialized structure, either to foster the assembly of Mei2p and meiRNA or to perform some unidentified function indispensable for meiosis I.

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Live observation of fission yeast meiosis in recombination-deficient mutants

Journal of Cell Science ◽

10.1242/jcs.114.15.2843 ◽

2001 ◽

Vol 114 (15) ◽

pp. 2843-2853 ◽

Cited By ~ 7

Author(s):

Monika Molnar ◽

Jürg Bähler ◽

Jürg Kohli ◽

Yasushi Hiraoka

Keyword(s):

Fission Yeast ◽

Chromosome Segregation ◽

Meiotic Division ◽

Chiasma Formation ◽

Homologous Chromosomes ◽

Yeast Meiosis ◽

Mutant Cells ◽

Random Level ◽

Meiosis I ◽

Chromosome Disjunction

Regular segregation of homologous chromosomes during meiotic divisions is essential for the generation of viable progeny. In recombination-proficient organisms, chromosome disjunction at meiosis I generally occurs by chiasma formation between the homologs (chiasmate meiosis). We have studied meiotic stages in living rec8 and rec7 mutant cells of fission yeast, with special attention to prophase and the first meiotic division. Both rec8 and rec7 are early recombination mutants, and in rec7 mutants, chromosome segregation at meiosis I occurs without any recombination (achiasmate meiosis). Both mutants showed distinct irregularities in nuclear prophase movements. Additionally, rec7 showed an extended first division of variable length and with single chromosomes changing back and forth between the cell poles. Two other early recombination deficient mutants (rec14 and rec15) showed very similar phenotypes to rec7 during the first meiotic division, and the fidelity of achiasmate chromosome segregation slightly exceeded the expected random level. We discuss possible regulatory mechanisms of fission yeast to deal with achiasmate chromosome segregation.

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