Role of centrosomal adaptor proteins of the TACC family in the regulation of microtubule dynamics during mitotic cell division

Abstract During the mitotic division cycle, cells pass through an extensive microtubule rearrangement process where microtubules forming the mitotic spindle apparatus are dynamically instable. Several centrosomal- and microtubule-associated proteins are involved in the regulation of microtubule dynamics and stability during mitosis. Here, we focus on members of the transforming acidic coiled coil (TACC) family of centrosomal adaptor proteins, in particular TACC3, in which their subcellular localization at the mitotic spindle apparatus is controlled by Aurora-A kinase-mediated phosphorylation. At the effector level, several TACC-binding partners have been identified and characterized in greater detail, in particular, the microtubule polymerase XMAP215/ch-TOG/CKAP5 and clathrin heavy chain (CHC). We summarize the recent progress in the molecular understanding of these TACC3 protein complexes, which are crucial for proper mitotic spindle assembly and dynamics to prevent faulty cell division and aneuploidy. In this regard, the (patho)biological role of TACC3 in development and cancer will be discussed.

Download Full-text

The mitotic spindle protein CKAP2 potently increases formation and stability of microtubules

eLife ◽

10.7554/elife.72202 ◽

2022 ◽

Vol 11 ◽

Author(s):

Thomas S McAlear ◽

Susanne Bechstedt

Keyword(s):

Cell Division ◽

Growth Factor ◽

Mitotic Spindle ◽

Apparent Rate Constant ◽

Microtubule Dynamics ◽

Proliferation Marker ◽

Microtubule Growth ◽

Large Rearrangements ◽

And Function

Cells increase microtubule dynamics to make large rearrangements to their microtubule cytoskeleton during cell division. Changes in microtubule dynamics are essential for the formation and function of the mitotic spindle, and misregulation can lead to aneuploidy and cancer. Using in vitro reconstitution assays we show that the mitotic spindle protein Cytoskeleton-Associated Protein 2 (CKAP2) has a strong effect on nucleation of microtubules by lowering the critical tubulin concentration 100-fold. CKAP2 increases the apparent rate constant ka of microtubule growth by 50-fold and increases microtubule growth rates. In addition, CKAP2 strongly suppresses catastrophes. Our results identify CKAP2 as the most potent microtubule growth factor to date. These finding help explain CKAP2's role as an important spindle protein, proliferation marker, and oncogene.

Download Full-text

Abnormal Micronuclear Telomeres Lead to an Unusual Cell Cycle Checkpoint and Defects in Tetrahymena Oral Morphogenesis

Eukaryotic Cell ◽

10.1128/ec.00393-07 ◽

2008 ◽

Vol 7 (10) ◽

pp. 1712-1723 ◽

Cited By ~ 3

Author(s):

Karen E. Kirk ◽

Christina Christ ◽

Jennifer M. McGuire ◽

Arun G. Paul ◽

Mithaq Vahedi ◽

...

Keyword(s):

Cell Cycle ◽

Mitotic Spindle ◽

Tetrahymena Thermophila ◽

Germ Line ◽

Cell Cycle Checkpoint ◽

Dna Damage Checkpoint ◽

Telomeric Dna ◽

Spindle Apparatus ◽

Cycle Checkpoint

ABSTRACT Telomere mutants have been well studied with respect to telomerase and the role of telomere binding proteins, but they have not been used to explore how a downstream morphogenic event is related to the mutated telomeric DNA. We report that alterations at the telomeres can have profound consequences on organellar morphogenesis. Specifically, a telomerase RNA mutation termed ter1-43AA results in the loss of germ line micronuclear telomeres in the binucleate protozoan Tetrahymena thermophila. These cells also display a micronuclear mitotic arrest, characterized by an extreme delay in anaphase with an elongated, condensed chromatin and a mitotic spindle apparatus. This anaphase defect suggests telomere fusions and consequently a spindle rather than a DNA damage checkpoint. Most surprisingly, these mutants exhibit unique, dramatic defects in the formation of the cell's oral apparatus. We suggest that micronuclear telomere loss leads to a “dynamic pause” in the program of cortical development, which may reveal an unusual cell cycle checkpoint.

Download Full-text

Aurora a kinase (AURKA) is required for male germline maintenance and regulates sperm motility in the mouse

Biology of Reproduction ◽

10.1093/biolre/ioab168 ◽

2021 ◽

Author(s):

William C Lester ◽

Taylor Johnson ◽

Ben Hale ◽

Nicholas Serra ◽

Brian Elgart ◽

...

Keyword(s):

Cell Division ◽

Sperm Count ◽

Mitotic Cell ◽

Vital Role ◽

Conditional Knockout ◽

Testis Size ◽

Aurora A Kinase ◽

Aurora A ◽

Mitotic Kinase ◽

Knockout Animals

Abstract Aurora A kinase (AURKA) is an important regulator of cell division and is required for assembly of the mitotic spindle. We recently reported the unusual finding that this mitotic kinase is also found on the sperm flagellum. To determine its requirement in spermatogenesis, we generated conditional knockout animals with deletion of the Aurka gene in either spermatogonia or spermatocytes to assess its role in mitotic and postmitotic cells, respectively. Deletion of Aurka in spermatogonia resulted in disappearance of all developing germ cells in the testis, as expected given its vital role in mitotic cell division. Deletion of Aurka in spermatocytes reduced testis size, sperm count, and fertility, indicating disruption of meiosis or an effect on spermiogenesis in developing mice. Interestingly, deletion of Aurka in spermatocytes increased apoptosis in spermatocytes along with an increase in the percentage of sperm with abnormal morphology. Despite the increase in abnormal sperm, sperm from spermatocyte Aurka knockout mice displayed increased progressive motility. In addition, sperm lysate prepared from Aurka knockout animals had decreased protein phosphatase 1 (PP1) activity. Together, our results show that AURKA plays multiple roles in spermatogenesis, from mitotic divisions of spermatogonia to sperm morphology and motility.

Download Full-text

The autophagy protein Ambra1 regulates gene expression by supporting novel transcriptional complexes

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.012565 ◽

2020 ◽

Vol 295 (34) ◽

pp. 12045-12057

Author(s):

Christina Schoenherr ◽

Adam Byron ◽

Billie Griffith ◽

Alexander Loftus ◽

Jimi C. Wills ◽

...

Keyword(s):

Gene Expression ◽

Cancer Cell ◽

Cell Invasion ◽

Cell Biology ◽

Protein Complexes ◽

Transcriptional Regulators ◽

Adaptor Proteins ◽

Nuclear Pore ◽

Biochemical Fractionation

Ambra1 is considered an autophagy and trafficking protein with roles in neurogenesis and cancer cell invasion. Here, we report that Ambra1 also localizes to the nucleus of cancer cells, where it has a novel nuclear scaffolding function that controls gene expression. Using biochemical fractionation and proteomics, we found that Ambra1 binds to multiple classes of proteins in the nucleus, including nuclear pore proteins, adaptor proteins such as FAK and Akap8, chromatin-modifying proteins, and transcriptional regulators like Brg1 and Atf2. We identified biologically important genes, such as Angpt1, Tgfb2, Tgfb3, Itga8, and Itgb7, whose transcription is regulated by Ambra1-scaffolded complexes, likely by altering histone modifications and Atf2 activity. Therefore, in addition to its recognized roles in autophagy and trafficking, Ambra1 scaffolds protein complexes at chromatin, regulating transcriptional signaling in the nucleus. This novel function for Ambra1, and the specific genes impacted, may help to explain the wider role of Ambra1 in cancer cell biology.

Download Full-text

The Sin3p PAH Domains Provide Separate Functions Repressing Meiotic Gene Transcription in Saccharomyces cerevisiae

Eukaryotic Cell ◽

10.1128/ec.00143-10 ◽

2010 ◽

Vol 9 (12) ◽

pp. 1835-1844 ◽

Cited By ~ 4

Author(s):

Michael J. Mallory ◽

Michael J. Law ◽

Lela E. Buckingham ◽

Randy Strich

Keyword(s):

Cell Division ◽

Vegetative Growth ◽

Mitotic Cell ◽

Amphipathic Helix ◽

Mobility Shift ◽

Mitotic Cell Division ◽

Meiotic Gene ◽

Electrophoretic Mobility Shift Assays ◽

Promoter Interaction

ABSTRACT Meiotic genes in budding yeast are repressed during vegetative growth but are transiently induced during specific stages of meiosis. Sin3p represses the early meiotic gene (EMG) by bridging the DNA binding protein Ume6p to the histone deacetylase Rpd3p. Sin3p contains four paired amphipathic helix (PAH) domains, one of which (PAH3) is required for repressing several genes expressed during mitotic cell division. This report examines the roles of the PAH domains in mediating EMG repression during mitotic cell division and following meiotic induction. PAH2 and PAH3 are required for mitotic EMG repression, while electrophoretic mobility shift assays indicate that only PAH2 is required for stable Ume6p-promoter interaction. Unlike mitotic repression, reestablishing EMG repression following transient meiotic induction requires PAH3 and PAH4. In addition, the role of Sin3p in reestablishing repression is expanded to include additional loci that it does not control during vegetative growth. These findings indicate that mitotic and postinduction EMG repressions are mediated by two separate systems that utilize different Sin3p domains.

Download Full-text

Combined effect of cell geometry and polarity domains determines the orientation of unequal division

eLife ◽

10.7554/elife.75639 ◽

2021 ◽

Vol 10 ◽

Author(s):

Benoit G Godard ◽

Remi Dumollard ◽

Carl-Philipp Heisenberg ◽

Alex McDougall

Keyword(s):

Cell Division ◽

Mitotic Spindle ◽

Cell Shape ◽

Daughter Cell ◽

Cleavage Plane ◽

Mitotic Cell ◽

Cell Geometry ◽

Daughter Cells ◽

Ascidian Embryos ◽

Spindle Position

Cell division orientation is thought to result from a competition between cell geometry and polarity domains controlling the position of the mitotic spindle during mitosis. Depending on the level of cell shape anisotropy or the strength of the polarity domain, one dominates the other and determines the orientation of the spindle. Whether and how such competition is also at work to determine unequal cell division (UCD), producing daughter cells of different size, remains unclear. Here, we show that cell geometry and polarity domains cooperate, rather than compete, in positioning the cleavage plane during UCDs in early ascidian embryos. We found that the UCDs and their orientation at the ascidian third cleavage rely on the spindle tilting in an anisotropic cell shape, and cortical polarity domains exerting different effects on spindle astral microtubules. By systematically varying mitotic cell shape, we could modulate the effect of attractive and repulsive polarity domains and consequently generate predicted daughter cell size asymmetries and position. We therefore propose that the spindle position during UCD is set by the combined activities of cell geometry and polarity domains, where cell geometry modulates the effect of cortical polarity domain(s).

Download Full-text

The Role of Mitotic Cell-Substrate Adhesion Re-modeling in Animal Cell Division

Developmental Cell ◽

10.1016/j.devcel.2018.03.009 ◽

2018 ◽

Vol 45 (1) ◽

pp. 132-145.e3 ◽

Cited By ~ 42

Author(s):

Christina L. Dix ◽

Helen K. Matthews ◽

Marina Uroz ◽

Susannah McLaren ◽

Lucie Wolf ◽

...

Keyword(s):

Cell Division ◽

Animal Cell ◽

Mitotic Cell ◽

Substrate Adhesion ◽

Cell Substrate ◽

Cell Substrate Adhesion

Download Full-text

Pachytene arrest and other meiotic effects of the start mutations in Saccharomyces cerevisiae.

Genetics ◽

10.1093/genetics/123.1.29 ◽

1989 ◽

Vol 123 (1) ◽

pp. 29-43 ◽

Cited By ~ 1

Author(s):

E O Shuster ◽

B Byers

Keyword(s):

Cell Division ◽

Nuclear Division ◽

Spindle Pole Body ◽

Mitotic Cell ◽

Spindle Pole ◽

Mitotic Cell Cycle ◽

Chromosomal Dna ◽

Pole Body ◽

Vegetative Cycle

Abstract Mutations in the Start class of cell division cycle genes (CDC28, CDC36 and CDC39) define the point in the G1 phase of the vegetative cycle at which the cell becomes committed to completing another round of cell division. Genetic, cytological and biochemical data demonstrate that these mutations cause meiotic cells to become arrested at pachytene following completion of both chromosomal DNA replication and spindle pole body (SPB) duplication. In contrast these mutations have previously been found to cause arrest of the mitotic cell cycle prior to either of these landmark events, so the role of the Start genes in these events during vegetative growth must be indirect. Our observations are consistent with the hypothesis that CDC28, CDC36 and CDC39 are required for irreversible commitment to nuclear division in both the mitotic and meiotic pathways. CDC28 was additionally found to be required for the SPB separation that precedes spindle formation in preparation for the second meiotic division. Cytological and genetic analyses of this requirement revealed both that such separation may fail independently at either SPB and that ascospore formation can proceed independently of SPB separation.

Download Full-text

Thirty years of search and capture: The complex simplicity of mitotic spindle assembly

The Journal of Cell Biology ◽

10.1083/jcb.201510015 ◽

2015 ◽

Vol 211 (6) ◽

pp. 1103-1111 ◽

Cited By ~ 90

Author(s):

Rebecca Heald ◽

Alexey Khodjakov

Keyword(s):

Cell Division ◽

Mitotic Spindle ◽

Spindle Assembly ◽

Microtubule Dynamics ◽

Adaptive Changes ◽

Bipolar Spindle ◽

Chromosome Architecture ◽

Self Assembling ◽

Motor Activities ◽

Mitotic Spindle Assembly

Cell division is enacted by a microtubule-based, self-assembling macromolecular machine known as the mitotic spindle. In 1986, Kirschner and Mitchison proposed that by undergoing dynamic cycles of growth and disassembly, microtubules search for chromosomes. Capture of microtubules by the kinetochores progressively connects chromosomes to the bipolar spindle. 30 years later, “search and capture” remains the cornerstone of spindle assembly. However, a variety of facilitating mechanisms such as regulation of microtubule dynamics by diffusible gradients, spatially selective motor activities, and adaptive changes in chromosome architecture have been discovered. We discuss how these mechanisms ensure that the spindle assembles rapidly and with a minimal number of errors.

Download Full-text