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

2007 ◽  
Vol 18 (5) ◽  
pp. 1657-1669 ◽  
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.

Megakaryocytes express functional Aurora-B kinase in endomitosis

Blood ◽  
2004 ◽  
Vol 104 (4) ◽  
pp. 1017-1024 ◽  
Author(s):  
Amy E. Geddis ◽  
Kenneth Kaushansky
Keyword(s):  
Aurora Kinase ◽  
Aurora B ◽  
Aurora A Kinase ◽  
Aurora B Kinase ◽  
Late Anaphase ◽  
Chromosomal Passenger ◽  
Early Anaphase ◽  
Chromosomal Passenger Proteins ◽  
Diploid Cells ◽  
Passenger Proteins

AbstractEndomitosis (EnM) in megakaryocytes (MKs) is characterized by abortion of mitosis in late anaphase and failure of cytokinesis; subsequent reinitiation of DNA synthesis results in polyploidy. Ablation of chromosomal passenger proteins including Aurora-B kinase causes defects in late anaphase and cytokinesis in diploid cells; thus one hypothesis is that the expression or function of these proteins in polyploid MKs is abnormal. It has been reported that Aurora-B kinase mRNA is decreased in polyploid megakaryocytic cells, suggesting that deficiency of Aurora-B kinase is responsible for EnM. We examined the localization of Aurora-B kinase and additional members of the chromosomal passenger protein and aurora kinase families in MKs. We found that in EnM MKs (1) Aurora-B kinase is present and appropriately localized to centromeres in early EnM; (2) in low-ploidy human MKs, centromeric localization of survivin and inner centromere protein (INCENP) can also be demonstrated; (3) the function of Aurora-B kinase, as measured by Ser10 phosphorylation of histone H3, is intact; and (4) aurora-A kinase localizes appropriately to centrosomes in EnM. These results suggest that EnM MKs appropriately express functional Aurora-B kinase and related proteins in early anaphase, making a simple deficiency of this protein an unlikely explanation for polyploidy in this cell type.

scholarly journals Uncoupling the Central Spindle-associated Function of the Chromosomal Passenger Complex from Its Role at Centromeres

2006 ◽  
Vol 17 (4) ◽  
pp. 1897-1909 ◽  
Author(s):  
Susanne M.A. Lens ◽  
Jose A. Rodriguez ◽  
Gerben Vader ◽  
Simone W. Span ◽  
Giuseppe Giaccone ◽  
...  
Keyword(s):  
Spindle Checkpoint ◽  
Aurora B ◽  
Deletion Mutants ◽  
Chromosomal Passenger Complex ◽  
Central Spindle ◽  
Survivin Protein ◽  
C Terminus ◽  
Chromosomal Passenger ◽  
Associated Function ◽  
Bir Domain

Survivin is a component of the chromosomal passenger complex (CPC) that plays a role in maintenance of an active spindle checkpoint and in cytokinesis. To study whether these different functions can be attributed to distinct domains within the Survivin protein, we complemented Survivin-depleted cells with a variety of point- and deletion-mutants of Survivin. We show that an intact baculovirus IAP repeat (BIR) domain is required for proper spindle checkpoint functioning, but dispensable for cytokinesis. In line with this, mutants lacking an intact BIR domain localized normally to the central spindle, but their localization to inner centromeres was severely perturbed. Consequently, these mutants failed to recruit Aurora B, Borealin/Dasra B, and BubR1 to centromeres and kinetochores, but they had retained the ability to recruit Aurora B and Borealin/Dasra B to the midzone and midbody. Thus, the C terminus of Survivin is sufficient for central spindle localization and execution of cytokinesis, but the additional presence of a functional BIR domain is essential for centromere targeting and spindle checkpoint function. Importantly, our data show that the function of the CPC at the centromere can be separated from its function at the central spindle and that execution of cytokinesis does not require prior concentration of the CPC at centromeres.

scholarly journals Bir1 Is Required for the Tension Checkpoint

2009 ◽  
Vol 20 (3) ◽  
pp. 915-923 ◽  
Author(s):  
Michelle M. Shimogawa ◽  
Per O. Widlund ◽  
Michael Riffle ◽  
Michael Ess ◽  
Trisha N. Davis
Keyword(s):  
Aurora B ◽  
Temperature Sensitive ◽  
Sensitive Mutant ◽  
Checkpoint Response ◽  
Temperature Sensitive Mutant ◽  
The Third ◽  
Chromosomal Passenger ◽  
Chromosomal Passenger Proteins ◽  
Passenger Proteins

The Saccharomyces cerevisiae chromosomal passenger proteins Ipl1 (Aurora B) and Sli15 (INCENP) are required for the tension checkpoint, but the role of the third passenger, Bir1, is controversial. We have isolated a temperature-sensitive mutant (bir1-107) in the essential C-terminal region of Bir1 known to be required for binding to Sli15. This allele reveals a checkpoint function for Bir1. The mutant displays a biorientation defect, a defective checkpoint response to lack of tension, and an inability to detach mutant kinetochores. Ipl1 localizes to aberrant foci when Bir1 localization is disrupted in the bir1-107 mutant. Thus, one checkpoint role of Bir1 is to properly localize Ipl1 and allow detachment of kinetochores. Quantitative analysis indicates that the chromosomal passengers colocalize with kinetochores in G1 but localize between kinetochores that are under tension. Bir1 localization to kinetochores is maintained in an mcd1-1 mutant in the absence of tension. Our results suggest that the establishment of tension removes Ipl1, Bir1, and Sli15, and their kinetochore detachment activity, from the vicinity of kinetochores and allows cells to proceed through the tension checkpoint.

Aurora-B Kinase Translocates to the Midzone in Endomitotic Megakaryocytes.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1263-1263
Author(s):  
Amy E. Geddis ◽  
Kenneth Kaushansky
Keyword(s):  
Actin Dynamics ◽  
Aurora B ◽  
Cleavage Furrow ◽  
Aurora B Kinase ◽  
Metaphase Chromosomes ◽  
Late Anaphase ◽  
Chromosomal Passenger ◽  
Chromosomal Passenger Proteins ◽  
Spindle Midzone ◽  
Passenger Proteins

Abstract Megakaryocyte (MK) differentiation is marked by the development of progressive polyploidy, facilitating platelet production by the creation of a large cytoplasmic volume. MKs become polyploid through repeated cycles of endomitosis (EnM), in which mitosis is initiated but subsequently aborted in late anaphase with failure to complete karyokinesis and cytokinesis. However, the mechanisms underlying EnM remain poorly understood. Recent hypotheses explored in the literature have focused on the possible absence or mislocalization of the chromosomal passenger protein Aurora-B kinase, as it has a pivotal role in many aspects of cytokinesis. Along with the other passenger proteins, Aurora-B kinase transits from the centromeres of metaphase chromosomes to the bundled microtubules of the spindle midzone and overlying cortex between separating chromosomes in anaphase. The midzone and its associated proteins, are thought to be critical for determining the position of the cleavage furrow. One of these proteins, the kinesin MKLP-2, is required for the translocation of Aurora-B kinase to the midzone, where it co-localizes with the GTPase MgcRacGAP and stimulates its activity towards RhoA, potentially regulating actin dynamics at the cleavage furrow. We have previously demonstrated that several chromosomal passenger proteins including Aurora-B kinase are normally expressed and localized to centromeres in EnM MKs. In this work, we use deconvolution microscopy in primary murine and human MKs to extend those findings and demonstrate that EnM MKs form midzone structures that are characteristic of late anaphase; in addition, Aurora-B kinase is clearly present on the spindle midzone, as are MKLP-2 and MgcRacGAP. Although we found images suggestive of initial cleavage furrow formation with cortical localization of Aurora-B kinase in late phase cells, we were unable to demonstrate enhanced localization of actin or anillin to the furrow in EnM cells, despite their normal localization in diploid control cells. Therefore, many of the components of the central spindle are intact during MK EnM, but the formation of the cleavage furrow appears to be incomplete. These data add to our understanding of the possible mechanisms underlying EnM and offer an alternative hypothesis to that of failed expression or localization of the chromosomal passenger proteins. Ongoing studies will focus on the assembly and function of the cleavage furrow in this enigmatic process.

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

2008 ◽  
Vol 182 (2) ◽  
pp. 277-288 ◽  
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.

scholarly journals A Link between Aurora Kinase and Clp1/Cdc14 Regulation Uncovered by the Identification of a Fission Yeast Borealin-Like Protein

2009 ◽  
Vol 20 (16) ◽  
pp. 3646-3659 ◽  
Author(s):  
K. Adam Bohnert ◽  
Jun-Song Chen ◽  
Dawn M. Clifford ◽  
Craig W. Vander Kooi ◽  
Kathleen L. Gould
Keyword(s):  
Cell Division ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Kinase Activity ◽  
Sequence Similarity ◽  
Aurora Kinase ◽  
Genetic Interactions ◽  
Aurora B ◽  
Contractile Ring ◽  
Chromosomal Passenger

The chromosomal passenger complex (CPC) regulates various events in cell division. This complex is composed of a catalytic subunit, Aurora B kinase, and three nonenzymatic subunits, INCENP, Survivin, and Borealin. Together, these four subunits interdependently regulate CPC function, and they are highly conserved among eukaryotes. However, a Borealin homologue has never been characterized in the fission yeast, Schizosaccharomyces pombe . Here, we isolate a previously uncharacterized S. pombe protein through association with the Cdc14 phosphatase homologue, Clp1/Flp1, and identify it as a Borealin-like member of the CPC. Nbl1 (novel Borealin-like 1) physically associates with known CPC components, affects the kinase activity and stability of the S. pombe Aurora B homologue, Ark1, colocalizes with known CPC subunits during mitosis, and shows sequence similarity to human Borealin. Further analysis of the Clp1–Nbl1 interaction indicates that Clp1 requires CPC activity for proper accumulation at the contractile ring (CR). Consistent with this, we describe negative genetic interactions between mutant alleles of CPC and CR components. Thus, this study characterizes a fission yeast Borealin homologue and reveals a previously unrecognized connection between the CPC and the process of cytokinesis in S. pombe .

Analysis of the distribution of the INCENPs throughout mitosis reveals the existence of a pathway of structural changes in the chromosomes during metaphase and early events in cleavage furrow formation

1991 ◽  
Vol 98 (4) ◽  
pp. 443-461 ◽  
Author(s):  
W.C. Earnshaw ◽  
C.A. Cooke
Keyword(s):  
Structural Changes ◽  
Metaphase Plate ◽  
Maximum Diameter ◽  
Cell Cortex ◽  
Cleavage Furrow ◽  
Intracellular Location ◽  
Chromosomal Passenger ◽  
Early Anaphase ◽  
Chromosomal Passenger Proteins ◽  
Passenger Proteins

The INCENPs are two polypeptides of 135 × 10(3) and 150 × 10(3) Mr that enter mitosis as tightly bound chromosomal proteins, but subsequently leave the chromosomes altogether and become associated with the central spindle and cell cortex at the contractile ring. In the experiments reported here we have used confocal microscopy and immunoelectron microscopy to provide a detailed picture of the intracellular location of these proteins during mitosis. The experiments have not only revealed a number of new details concerning the properties of the INCENPs in mitosis, but have revealed a number of novel aspects of the mitotic process itself. The first of these is the existence of a sequential pathway of structural changes in the chromosomes that occurs during metaphase. This pathway is revealed by the existence of four distinct INCENP staining patterns in mitotic cells. In ‘early’ and ‘early/mid’ metaphase, the INCENPs gradually become concentrated at the centromeres, forming a ring at the center of the metaphase plate. During ‘mid/late’ metaphase they exit from the chromosomes, so that by late metaphase they are found solely in streaks that traverse the plate parallel to the spindle axis. The streaks probably correspond to INCENPs closely associated with microtubule bundles, perhaps as part of the stem body material. Examination of transverse optical sections of the spindle interzone during early anaphase reveals an unexpectedly high degree of order. The INCENP antigens are localized on fibers that are organized into a hollow ring 8 microns in diameter and approximately 4 microns beneath the cell cortex. Measurement of cellular dimensions in the confocal microscope reveals that the maximum diameter of early anaphase cells lies across the spindle equator, so that when the cleavage furrow forms, it does so around the maximum circumference of the cell. During anaphase, a subpopulation of the INCENP antigen becomes localized to the cortex where the furrow will subsequently form. This occurs prior to any other evidence of furrowing. Thus, binding of the INCENPs to this region may represent an early step in furrow formation. Together, these results suggest that the INCENPs may represent a new class of ‘chromosomal passenger’ proteins that are carried to the spindle equator by the chromosomes and subsequently perform a cytoskeletal role following their release from the chromosomes at the metaphase:anaphase transition.

scholarly journals Multiple pools of Protein Phosphatase 2A-B56 function to antagonize spindle assembly, promote kinetochore attachments and maintain cohesion in Drosophila Oocytes

2020 ◽  
Author(s):  
Janet K. Jang ◽  
Amy C. Gladstein ◽  
Arunika Das ◽  
Zachary L. Sisco ◽  
Kim S. McKim
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Spindle Assembly ◽  
Meiotic Spindle ◽  
Aurora B ◽  
Microtubule Organizing Center ◽  
Chromosomal Passenger ◽  
Organizing Center ◽  
Phosphatase 2A ◽  
Meiosis I

AbstractMeiosis in female oocytes lack centrosomes, the major microtubule-organizing center, which makes them especially vulnerable to aneuploidy. In the acentrosomal oocytes of Drosophila, meiotic spindle assembly depends on the chromosomal passenger complex (CPC). Aurora B is the catalytic component of the CPC while the remaining subunits regulate its localization. Using an inhibitor of Aurora B activity, Binucleine 2, we found that continuous Aurora B activity is required to maintain the oocyte spindle during meiosis I, and this activity is antagonized by phosphatases acting on spindle associated proteins such as kinesins. Protein Phosphatase 2A (PP2A) exists in two varieties, B55 and B56. While both antagonize Aurora B, B55 has only minor roles in meiosis I spindle function. The B56 subunit is encoded by two partially redundant paralogs in the Drosophila genome, wdb and wrd. Knocking down both paralogs showed that the B56 subunit is critical for maintaining sister chromatid cohesion, establishing end-on microtubule attachments, and the metaphase I arrest in oocytes. We found that WDB recruitment to the centromeres depends on BUBR1, MEI-S332, and kinetochore protein SPC105R. While BUBR1 has been shown previously to stabilize microtubule attachments in Drosophila oocytes, only SPC105R is required for cohesion maintenance during meiosis I. We propose that SPC105R promotes cohesion maintenance by recruiting two proteins that recruit PP2A, MEI-S332, and the Soronin homolog Dalmatian.

scholarly journals The COMA complex interacts with Cse4 and positions Sli15/Ipl1 at the budding yeast inner kinetochore

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Josef Fischböck-Halwachs ◽  
Sylvia Singh ◽  
Mia Potocnjak ◽  
Götz Hagemann ◽  
Victor Solis-Mezarino ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Synthetic Lethality ◽  
Protein Complexes ◽  
Budding Yeast ◽  
Molecular Characteristics ◽  
Aurora B ◽  
C Terminus ◽  
Chromosomal Passenger ◽  
Macromolecular Protein

Kinetochores are macromolecular protein complexes at centromeres that ensure accurate chromosome segregation by attaching chromosomes to spindle microtubules and integrating safeguard mechanisms. The inner kinetochore is assembled on CENP-A nucleosomes and has been implicated in establishing a kinetochore-associated pool of Aurora B kinase, a chromosomal passenger complex (CPC) subunit, which is essential for chromosome biorientation. By performing crosslink-guided in vitro reconstitution of budding yeast kinetochore complexes we showed that the Ame1/Okp1CENP-U/Q heterodimer, which forms the COMA complex with Ctf19/Mcm21CENP-P/O, selectively bound Cse4CENP-A nucleosomes through the Cse4 N-terminus. The Sli15/Ipl1INCENP/Aurora-B core-CPC interacted with COMA in vitro through the Ctf19 C-terminus whose deletion affected chromosome segregation fidelity in Sli15 wild-type cells. Tethering Sli15 to Ame1/Okp1 rescued synthetic lethality upon Ctf19 depletion in a Sli15 centromere-targeting deficient mutant. This study shows molecular characteristics of the point-centromere kinetochore architecture and suggests a role for the Ctf19 C-terminus in mediating CPC-binding and accurate chromosome segregation.

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