AtREC8 and AtSCC3 are essential to the monopolar orientation of the kinetochores during meiosis (original) (raw)
Related papers
The EMBO Journal, 2021
Genome haploidization involves sequential loss of cohesin from chromosome arms and centromeres during two meiotic divisions. At centromeres, cohesin's Rec8 subunit is protected from separase cleavage at meiosis I and then deprotected to allow its cleavage at meiosis II. Protection of centromeric cohesin by shugoshin-PP2A seems evolutionarily conserved. However, deprotection has been proposed to rely on spindle forces separating the Rec8 protector from cohesin at metaphase II in mammalian oocytes and on APC/ C-dependent destruction of the protector at anaphase II in yeast. Here, we have activated APC/C in the absence of sister kinetochore biorientation at meiosis II in yeast and mouse oocytes, and find that bipolar spindle forces are dispensable for sister centromere separation in both systems. Furthermore, we show that at least in yeast, protection of Rec8 by shugoshin and inhibition of separase by securin are both required for the stability of centromeric cohesin at metaphase II. Our data imply that related mechanisms preserve the integrity of dyad chromosomes during the short metaphase II of yeast and the prolonged metaphase II arrest of mammalian oocytes.
Evidence of kinesin motors involved in stable kinetochore assembly during early meiosis
The characteristic ‘bi-lobed’ organization of the kinetochores observed during mitotic metaphase is a result of separation of the sister kinetochores into two clusters upon their stable end-on attachment to the microtubules emanating from opposite spindle poles. In contrast, during metaphase I of meiosis despite bi-orientation of the homologs, we observe that the kinetochores are linearly dispersed between the two spindle poles indicating that pole-distal and pole-proximal kinetochores are attached laterally and end-on, respectively to the microtubules. Colocalization studies of kinetochores and kinesin motors suggest that budding yeast kinesin 5, Cin8 and Kip1 perhaps localize to the end-on attached kinetochores while kinesin 8, Kip3 resides at all the kinetochores. Unlike mitosis in budding yeast, in meiosis, the outer kinetochores assemble much later after prophase I. From the findings including co-appearance of kinesin 5 and the outer kinetochore protein Ndc80 at the centromeres...
Cell, 1999
Rennweg 14 Scc3p (Losada et al., 1998; Toth et al., 1999). Smc1 and Smc3 are thought to form a heterodimer in which the † I.M.P. Research Institute of Molecular Pathology Dr. Bohrgasse 7 proteins are joined by two long stretches of antiparallel coiled coil that are separated by a hinge region forming A-1030 Vienna Austria a V-shaped molecule (Melby et al., 1998; Hirano, 1999; Nasmyth, 1999). Cohesion between sister chromatids is established during S phase, possibly at replication forks where sisters are in close proximity (Uhlmann and Na-Summary smyth, 1998). In yeast, cohesin remains associated with chromosomes from S phase until metaphase. Two of A multisubunit complex, called cohesin, containing its subunits, Scc1p and Scc3p, dissociate from chromo-Smc1p, Smc3p, Scc1p, and Scc3p, is required for sissomes as sister chromatids separate at the onset of ter chromatid cohesion in mitotic cells. We show here anaphase (Michaelis et al., 1997). In animal cells, howthat Smc3p and a meiotic version of Scc1p called Rec8p are required for cohesion between sister chro-ever, most cohesin dissociates from chromosomes durmatids, for formation of axial elements, for reciprocal ing prophase (Losada et al., 1998) even though cohesion recombination, and for preventing hyperresection of persists until anaphase. What holds sister centromeres double-strand breaks during meiosis. Both Rec8p and together during metaphase in animal cells and whether Smc3p colocalize with chromosome cores indepenit involves residual cohesin is not known. dently of synapsis during prophase I and largely disap-Sister chromatid cohesion and its dissolution is expear from chromosome arms after pachytene but perpected to have key roles during both meiotic divisions. sist in the neighborhood of centromeres until the onset Premeiotic DNA replication produces sister chromatids of anaphase II. The eukaryotic cell's cohesion apparathat are held tightly together. Homolog chromosomes tus is required both for the repair of recombinogenic then pair along their entire length and during pachytene lesions and for chromosome segregation and thereform double, synapsed chromosomes that are associfore appears to lie at the heart of the meiotic process. ated with a proteinaceous scaffold called the synaptonemal complex (SC) (Moses, 1958; Kleckner, 1996; Roeder, 1997). This structure consists of two axial ele-Introduction ments running along the longitudinal axes of sister chromatid pairs and a central element composed of proteins During meiosis, chromosome number is halved because like Zip1 or Scp1 (Sym et al., 1993; Schmekel et al., two successive rounds of chromosome segregation oc-1996), which connect axial elements. DNA doublecur without an intervening round of chromosome duplistrand breaks (DSBs) induced by the Spo11 endonuclecation. This enables the production of haploid gametes ase (Bergerat et al., 1997; Keeney et al., 1997) lead to from diploid cells. Chromosome segregation during the recombination between chromatids from homologous second meiotic "equational" division resembles that chromosomes and the formation of chiasmata, which during mitosis in that sister centromeres are segregated become visible in many organisms after the synaptoneto opposite poles of the cell. During the first "reducmal complex has been destroyed. Chiasmata connect tional" division, sister centromeres remain attached to homologous chromosomes, and it has been proposed each other as they are separated from their homologs that sister chromatid cohesion along chromosome arms (reviewed in Miyazaki and Orr-Weaver, 1994). holds the homologs together (Maguire, 1974; Carpenter, During mitosis, sister chromatids segregate away 1994). from each other because their kinetochores attach to During meiosis I, sister kinetochores attach to spinmicrotubules that extend to opposite poles (Rieder and dles emanating from the same pole, while homolog ki-Salmon, 1998). During the early phases of mitosis, from netochore pairs connect to the opposite pole. As a conprophase until metaphase, the tendency of microtubules sequence, homologs and not sister chromatids come to move sisters apart is counteracted by cohesion holdunder tension from the meiosis I spindle apparatus. ing sisters together. Cohesion not only generates the Chromosome segregation at the first meiotic division tension by which cells align sister chromatids on the therefore requires destruction of sister chromatid cohemetaphase plate but possibly also ensures that sister sion along chromosome arms. Meanwhile, cohesion bekinetochores attach to spindles emanating from oppotween sister centromeres persists throughout the first site poles. The sudden loss of cohesion both at centromeiotic division and permits alignment of sister chromameres and along chromosome arms, rather than an intids on the meiosis II mitotic spindle. Its subsequent crease in the exertion of microtubules, is thought to destruction is thought to trigger sister separation at anaphase II. ‡ To whom correspondence should be addressed (e-mail: fklein@ s1.botanik.univie.ac.at). Genetic and biochemical analyses have identified Cell 92 both axial element constituents and proteins needed for sporulates with high efficiency and does so even at 35ЊC. Diploid scc1-73 cells produced four spored asci with an sister chromatid cohesion. In yeast, Red1p is necessary for axial element formation and for efficient sister chro-efficiency comparable to wild type (at both 25ЊC and at 35ЊC), but only 50% of their spores were viable. Diploid matid cohesion (Smith and Roeder, 1997). Red1p and its protein kinase Mek1p (Bailis and Roeder, 1998) are smc3-42 cells, in contrast, failed to sporulate at either temperature. Even at 30ЊC, smc3-42 cells failed to un-distributed in a patchy manner along pachytene chromosomes. However, neither of these proteins nor Hop1p dergo any meiotic divisions and arrested with a single nucleus, which often degenerated (not shown). (Hollingsworth et al., 1990), which has a similar distribution, persists at centromeres after the first meiotic divi-To observe chromosome cohesion and segregation, we integrated multiple tandem operators for the bacte-sion. In mammals, Scp3p (Cor1), which is found along the entire length of axial elements (Dobson et al., 1994; rial Tet repressor in the vicinity of the chromosome V centromere. These Tet operators were visualized by ex-Lammers et al., 1995), does persist in the neighborhood of centromeres until anaphase II. Drosophila melano-pressing a Tet repressor protein fused to green fluorescent protein (GFP) (Michaelis et al., 1997). Upon transfer gaster MeiS332p, which has been characterized both genetically and cytologically, associates with centro-of wild-type cells to sporulation medium, the centromere V (cenV)-GFP dots from each homolog were paired in meric regions only during metaphase I and persists there until the onset of anaphase II (Moore et al., 1998). It about 85% of cells (due presumably to centromere clustering), but they temporarily separated before reassoci-prevents precocious loss of cohesion between sister centromeres (Kerrebrock et al., 1995). ating prior to segregation at the first meiotic division (Figure 1). In mutants that cannot undergo recombina-We began this study by asking whether two cohesin subunits known to be required for sister chromatid cohe-tion and fail to synapse homologs, the fraction of uninucleate cells with paired cenV-GFP dots steadily declined sion during mitosis were also essential during meiosis. We investigated the roles of Scc1p (also called Mcd1p (P. M. et al., unpublished), indicating that recombinationmediated pairing of homologs is responsible for the later or Rhc21p) (Guacci et al., 1997; Michaelis et al., 1997; Heo et al., 1998) and Smc3p (Michaelis et al., 1997). We associations. In wild type, binucleate cells usually contained two very closely juxtaposed cenV-GFP dots per found that Scc1p is expressed at very low levels in meiotic cells and that the scc1-73 allele, which is condi-nucleus (Table 1 and Figure 1), which then split into two at the onset of anaphase II. Tetranucleate cells always tionally lethal in mitosis, has only a modest influence on spore formation and viability. Smc3p, on the other hand, contained one GFP dot per nucleus (Table 1B and Figure 1). is expressed at high levels and, like mammalian Scp3 (Schalk et al., 1998), is found continuously along chro-The presence of three or four GFP dots in a uninucleate cell indicates separation of sister chromatids before mosome cores. Smc3p is furthermore essential both for the formation of axial elements and for meiotic sister the first meiotic division. Such cells were never seen in wild type or in spo11 mutants (not shown) and only chromatid cohesion, showing that the processes of chromosome axis formation and sister chromatid cohe-rarely in scc1-73 mutants. In contrast, the fraction of uninucleate cells with three or four GFP dots rose to sion are intimately related in meiosis. The budding yeast genome contains a second Scc1-50% in smc3-42 mutants (Figure 1). This suggests that Smc3p but possibly not Scc1p is essential for sister like protein that, because of its weak homology to the Rec8 protein in Schizosaccharomyces pombe (DeVeaux chromatid cohesion prior to the first meiotic division. Analysis of the pattern of GFP dots in binucleate cells and Smith, 1994; Molnar et al., 1995; Michaelis et al., 1997), we call Rec8p. Rec8p is expressed exclusively confirmed this conclusion (Table 1A). Wild-type (WT) and scc1-73 binucleate cells usually had a pair of closely during meiosis. Like Smc3p, Rec8p colocalizes with chromosome cores containing either axial elements or juxtaposed dots in each nucleus and produced four spored asci with a single GFP dot in each spore (Table synaptonemal complexes and is necessary for their formation. Neither Rec8p nor Smc3p is required for the 1B). In contrast, spo11 mutants showed a pattern...
Journal of Cell Science, 2003
The faithful transmission of chromosomes during mitosis and meiosis is essential for the survival of eukaryotic organisms. A critical aspect of chromosome segregation is sister chromatid cohesion, which is required for proper attachment of chromosomes to the spindle and the faithful segregation of sister chromatids to opposite poles of the cell during anaphase (reviewed by . Sister chromatid cohesion is mediated, in part, by a group of highly conserved proteins, referred to as the cohesin complex. Four proteins (SMC1, SMC3, SCC1 and SCC3) form the core of the mitotic cohesin complex, which is utilized by a wide range of organisms. In S. cerevisiae, the cohesion complex is found on chromosomes from S phase to anaphase, with preferential binding in centromeric regions . The release of chromosome cohesion at the metaphase to anaphase transition and the subsequent separation of sister chromatids is triggered in most organisms by separase, a cysteine protease, which specifically cleaves SCC1 .
Complex regulation of sister kinetochore orientation in meiosis-I
Journal of Biosciences, 2010
Kinetochores mediate chromosome movement during cell division by interacting with the spindle microtubules. Sexual reproduction necessitates the daunting task of reducing ploidy (number of chromosome sets) in the gametes, which depends upon the specialized properties of meiosis. Kinetochores have a central role in the reduction process. In this review, we discuss the complexity of this role of kinetochores in meiosis-I.
… and cellular biology, 2001
The behavior of meiotic chromosomes differs in several respects from that of their mitotic counterparts, resulting in the generation of genetically distinct haploid cells. This has been attributed in part to a meiosisspecific chromatin-associated protein structure, the synaptonemal complex. This complex consist of two parallel axial elements, each one associated with a pair of sister chromatids, and a transverse filament located between the synapsed homologous chromosomes. Recently, a different protein structure, the cohesin complex, was shown to be associated with meiotic chromosomes and to be required for chromosome segregation. To explore the functions of the two different protein structures, the synaptonemal complex and the cohesin complex, in mammalian male meiotic cells, we have analyzed how absence of the axial element affects early meiotic chromosome behavior. We find that the synaptonemal complex protein 3 (SCP3) is a main determinant of axial-element assembly and is required for attachment of this structure to meiotic chromosomes, whereas SCP2 helps shape the in vivo structure of the axial element. We also show that formation of a cohesincontaining chromosomal core in meiotic nuclei does not require SCP3 or SCP2. Our results also suggest that the cohesin core recruits recombination proteins and promotes synapsis between homologous chromosomes in the absence of an axial element. A model for early meiotic chromosome pairing and synapsis is proposed.
Kinesin motors provide the molecular forces at the kinetochore-microtubule interface and along the spindle to control chromosome segregation. During meiosis with the two rounds of microtubule assembly-disassembly, the roles of motor proteins remain unexplored. We observed that in contrast to mitosis Cin8 (kinesin 5) and Kip3 (kinesin 8) together are indispensable in meiosis. Examining the meiosis in cin8∆ kip3∆ cells, we detected chromosome breakage in the meiosis II cells. The double mutant exhibits delay in the cohesin removal and spindle elongation during anaphase I. Consequently, some cells abrogate meiosis II and form dyads while some, as they progress through meiosis II, cause defect in chromosome integrity. We believe that in the latter cells, an imbalance of spindle mediated force and simultaneous persistent cohesin on the chromosomes cause their breakage. We provide evidence that tension generated by Cin8 and Kip3 through microtubule cross-linking is essential for signaling...
The centromere geometry essential for keeping mitosis error free is controlled by spindle forces
Nature, 2007
Accurate segregation of chromosomes, essential for the stability of genome, depends on 'biorientation'-simultaneous attachment of each individual chromosome to both poles of the mitotic spindle 1. On bioriented chromosomes, kinetochores (macromolecular complexes that attach the chromosome to the spindle) reside on the opposite sides of chromosome's centromere 2. In contrast, sister kinetochores shift toward one side of the centromere on 'syntelic' chromosomes that erroneously attach to one spindle pole with both sister kinetochores. Syntelic attachments often arise during spindle assembly and must be corrected to prevent chromosome loss 3. It is assumed that restoration of proper centromere architecture occurs automatically due to elastic properties of the centromere 1, 2. Here we test this assumption by combining laser microsurgery and chemical biology assays. We find that kinetochores of syntelic chromosomes remain juxtaposed upon detachment from spindle microtubules. These findings reveal that correction of syntelic attachments involves an extra step that has previously been overlooked: external forces must be applied to move sister kinetochores to the opposite sides of the centromere. Further, we demonstrate that shape of the centromere is important for spindle assembly, as bipolar spindles do not form is cells lacking centrosomes when multiple chromosomes with juxtaposed kinetochores are present. Thus, proper architecture of the centromere makes an important contribution to achieving high fidelity of chromosome segregation. Kinetochores on bioriented chromosomes are positioned on the opposite sides of the centromere 2. However, during mitotic spindle formation both sister kinetochores sometimes attach to the same spindle pole becoming 'syntelic'. Under this condition, microtubuledependent forces shift sister kinetochores to the same side of the centromere. As syntelic attachment would lead to aneuploidy, this configuration is not stable 4,5. Kinetochore fibres (K-fibres) on syntelic chromosomes depolymerize so that the chromosome moves to the spindle pole where at least one of the two kinetochores detaches from microtubules 6-8. Detached kinetochores can then connect to microtubules from the opposite spindle pole to achieve proper bi-orientation. However, for this mechanism to work properly the shape of the centromere must be restored such that sister kinetochores return to opposite sides of the centromere. It is