scholarly journals Multiple pools of PP2A regulate spindle assembly, kinetochore attachments, and cohesion in Drosophila oocytes

2021 ◽  
Author(s):  
Janet K. Jang ◽  
Amy C. Gladstein ◽  
Arunika Das ◽  
Joanatta G. Shapiro ◽  
Zachary L. Sisco ◽  
...  
Keyword(s):  
Spindle Assembly ◽  
Meiotic Spindle ◽  
Aurora B ◽  
Microtubule Organizing Center ◽  
Oocyte Meiosis ◽  
Chromatid Cohesion ◽  
Chromosomal Passenger ◽  
Organizing Center ◽  
Phosphatase 2A ◽  
Meiosis I

Meiosis in female oocytes lacks centrosomes, the microtubule-organizing center. In Drosophila oocytes, meiotic spindle assembly depends on the chromosomal passenger complex (CPC). To investigate the mechanisms that regulate Aurora B activity, we examined the role of Protein Phosphatase 2A (PP2A) in oocyte meiosis. We found that both forms of PP2A, B55 and B56, antagonize the Aurora B spindle assembly function, suggesting that a balance between Aurora B and PP2A activity maintains the oocyte spindle during meiosis I. PP2A-B56, which is encoded by two partially redundant paralogs, wdb and wrd, is also required for maintaining sister chromatid cohesion, establishing end-on microtubule attachments, and the metaphase I arrest in oocytes. WDB recruitment to the centromeres depends on BUBR1, MEI-S332, and kinetochore protein SPC105R. While BUBR1 stabilizes microtubule attachments in Drosophila oocytes, it is not required for cohesion maintenance during meiosis I. We propose at least three populations of PP2A-B56 regulate meiosis, two of which depend on SPC105R and a third that is associated with the spindle.

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 Cdc55 coordinates spindle assembly and chromosome disjunction during meiosis

2011 ◽  
Vol 193 (7) ◽  
pp. 1213-1228 ◽  
Author(s):  
Farid Bizzari ◽  
Adele L. Marston
Keyword(s):  
Protein Phosphatase ◽  
Deoxyribonucleic Acid ◽  
Nuclear Division ◽  
Spindle Assembly ◽  
Regulatory Subunit ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Phosphatase 2A ◽  
Meiosis I ◽  
Sequential Assembly

During meiosis, two consecutive nuclear divisions follow a single round of deoxyribonucleic acid replication. In meiosis I, homologues are segregated, whereas in meiosis II, sister chromatids are segregated. This requires that the sequential assembly and dissolution of specialized chromosomal factors are coordinated with two rounds of spindle assembly and disassembly. How these events are coupled is unknown. In this paper, we show, in budding yeast, that the protein phosphatase 2A regulatory subunit Cdc55 couples the loss of linkages between chromosomes with nuclear division by restraining two other phosphatases, Cdc14 and PP2ARts1. Cdc55 maintains Cdc14 sequestration in the nucleolus during early meiosis, and this is essential for the assembly of the meiosis I spindle but not for chromosomes to separate. Cdc55 also limits the formation of PP2A holocomplexes containing the alternative regulatory subunit Rts1, which is crucial for the timely dissolution of sister chromatid cohesion. Therefore, Cdc55 orders passage through the meiotic divisions by ensuring a balance of phosphatases.

subito Encodes a Kinesin-like Protein Required for Meiotic Spindle Pole Formation in Drosophila melanogaster

Genetics ◽  
2002 ◽  
Vol 160 (4) ◽  
pp. 1489-1501 ◽  
Author(s):  
Kelly L Giunta ◽  
Janet K Jang ◽  
Elizabeth A Manheim ◽  
Gayathri Subramanian ◽  
Kim S McKim
Keyword(s):  
Drosophila Melanogaster ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Microtubule Organizing Center ◽  
Bipolar Spindle ◽  
Microtubule Associated Proteins ◽  
Organizing Center ◽  
Associated Proteins ◽  
Similar Phenotype ◽  
Meiosis I

Abstract The female meiotic spindle lacks a centrosome or microtubule-organizing center in many organisms. During cell division, these spindles are organized by the chromosomes and microtubule-associated proteins. Previous studies in Drosophila melanogaster implicated at least one kinesin motor protein, NCD, in tapering the microtubules into a bipolar spindle. We have identified a second Drosophila kinesin-like protein, SUB, that is required for meiotic spindle function. At meiosis I in males and females, sub mutations affect only the segregation of homologous chromosomes. In female meiosis, sub mutations have a similar phenotype to ncd; even though chromosomes are joined by chiasmata they fail to segregate at meiosis I. Cytological analyses have revealed that sub is required for bipolar spindle formation. In sub mutations, we observed spindles that were unipolar, multipolar, or frayed with no defined poles. On the basis of these phenotypes and the observation that sub mutations genetically interact with ncd, we propose that SUB is one member of a group of microtubule-associated proteins required for bipolar spindle assembly in the absence of the centrosomes. sub is also required for the early embryonic divisions but is otherwise dispensable for most mitotic divisions.

scholarly journals Phosphorylation of the synaptonemal complex protein SYP-1 promotes meiotic chromosome segregation

2017 ◽  
Author(s):  
Aya Sato-Carlton ◽  
Chihiro Nakamura-Tabuchi ◽  
Stephane Kazuki Chartrand ◽  
Tomoki Uchino ◽  
Peter Mark Carlton
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Chromosome ◽  
C Elegans ◽  
Chromosome Domains ◽  
Chromatid Cohesion ◽  
Complex Protein ◽  
Chromosomal Passenger ◽  
Synaptonemal Complex Protein ◽  
A Site ◽  
Meiosis I

AbstractChromosomes that have undergone crossing-over in meiotic prophase must maintain sister chromatid cohesion somewhere along their length between the first and second meiotic divisions. While many eukaryotes use the centromere as a site to maintain cohesion, the holocentric organism C. elegans instead creates two chromosome domains of unequal length termed the short arm and long arm, which become the first and second site of cohesion loss at meiosis I and II. The mechanisms that confer distinct functions to the short and long arm domains remain poorly understood. Here, we show that phosphorylation of the synaptonemal complex protein SYP-1 is required to create these domains. Once crossovers are made, phosphorylated SYP-1 and PLK-2 become cooperatively confined to short arms and guide phosphorylated histone H3 and the chromosomal passenger complex to the site of meiosis I cohesion loss. Our results show that PLK-2 and phosphorylated SYP-1 ensure creation of the short arm subdomain, promoting disjunction of chromosomes in meiosis I.

scholarly journals Reorganization of actin filaments by ADF/cofilin is involved in formation of microtubule structures during Xenopus oocyte maturation

2015 ◽  
Vol 26 (24) ◽  
pp. 4387-4400 ◽  
Author(s):  
Yuka Yamagishi ◽  
Hiroshi Abe
Keyword(s):  
Oocyte Maturation ◽  
Actin Filament ◽  
Actin Filaments ◽  
Xenopus Oocyte ◽  
Germinal Vesicle ◽  
Meiotic Spindle ◽  
Base Region ◽  
Microtubule Organizing Center ◽  
Cytoplasmic Actin ◽  
Organizing Center

We examined the reorganization of actin filaments and microtubules during Xenopus oocyte maturation. Surrounding the germinal vesicle (GV) in immature oocytes, the cytoplasmic actin filaments reorganized to accumulate beneath the vegetal side of the GV, where the microtubule-organizing center and transient microtubule array (MTOC-TMA) assembled, just before GV breakdown (GVBD). Immediately after GVBD, both Xenopus ADF/cofilin (XAC) and its phosphatase Slingshot (XSSH) accumulated into the nuclei and intranuclear actin filaments disassembled from the vegetal side with the shrinkage of the GV. As the MTOC-TMA developed well, cytoplasmic actin filaments were retained at the MTOC-TMA base region. Suppression of XAC dephosphorylation by anti-XSSH antibody injection inhibited both actin filament reorganization and proper formation and localization of both the MTOC-TMA and meiotic spindles. Stabilization of actin filaments by phalloidin also inhibited formation of the MTOC-TMA and disassembly of intranuclear actin filaments without affecting nuclear shrinkage. Nocodazole also caused the MTOC-TMA and the cytoplasmic actin filaments at its base region to disappear, which further impeded disassembly of intranuclear actin filaments from the vegetal side. XAC appears to reorganize cytoplasmic actin filaments required for precise assembly of the MTOC and, together with the MTOC-TMA, regulate the intranuclear actin filament disassembly essential for meiotic spindle formation.

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.

scholarly journals The Borealin dimerization domain interacts with Sgo1 to drive Aurora B–mediated spindle assembly

2020 ◽  
Vol 31 (20) ◽  
pp. 2207-2218 ◽  
Author(s):  
Mary Kate Bonner ◽  
Julian Haase ◽  
Hayden Saunders ◽  
Hindol Gupta ◽  
Biyun Iris Li ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Spindle Assembly ◽  
Specific Role ◽  
Aurora B ◽  
Dimerization Domain ◽  
Chromosomal Passenger Complex ◽  
Chromosomal Passenger ◽  
Segregation Of Chromosomes

This study provides the molecular mechanism for the interaction of Sgo1 with the chromosomal passenger complex and explores the specific role of Sgo1 in regulating Aurora B functions that ensure the equal segregation of chromosomes.

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