Orbit, a Novel Microtubule-Associated Protein Essential for Mitosis in<i>Drosophila melanogaster</i>

Inoué, Yoshihiro; Avides, Maria do Carmo; Shiraki, Michina; Deák, Péter; Yamaguchi, Masamitsu; Nishimoto, Yoshio; Matsukage, Akio; Glover, David M.

doi:10.1083/jcb.149.1.153

Cited by 122 publications

(155 citation statements)

References 57 publications

Supporting

Mentioning

146

Contrasting

Order By: Relevance

“…The second flux component to be identified is the CLASP protein, Mast/Orbit (Mast), which induces microtubule polymerization and can be found on kinetochore-associated plus ends (Inoue et al, 2000;Lemos et al, 2000). The inhibition of Mast also perturbs flux but causes spindles to shorten or collapse, consistent with the hypothesis that this protein actively incorporates tubulin subunits into the plus ends of kinetochore microtubules (Maiato et al, 2005).…”

Section: Introductionmentioning

confidence: 62%

Poleward Tubulin Flux in Spindles: Regulation and Function in Mitotic Cells

Buster

Zhang

Sharp

2007

MBoC

View full text Add to dashboard Cite

The poleward flux of tubulin subunits through spindle microtubules is a striking and conserved phenomenon whose function and molecular components remain poorly understood. To screen for novel components of the flux machinery, we utilized RNA interference to deplete regulators of microtubule dynamics, individually and in various combinations, from S2 cells and examined the resulting impact on flux rate. This led to the identification of two previously unknown flux inhibitors, KLP59C and KLP67A, and a flux promoter, Mini-spindles. Furthermore, we find that flux rate is regulated by functional antagonism among microtubule stabilizers and destabilizers specifically at plus ends. Finally, by examining mitosis on spindles in which flux has been up-or down-regulated or restored after the codepletion of antagonistic flux regulators, we show that flux is an integral contributor to anaphase A but is not responsible for chromosome congression, interkinetochore tension, or the establishment of normal spindle length during prometaphase/metaphase.

show abstract

Section: Introductionmentioning

confidence: 62%

Poleward Tubulin Flux in Spindles: Regulation and Function in Mitotic Cells

Buster

Zhang

Sharp

2007

MBoC

View full text Add to dashboard Cite

show abstract

“…In addition to its function in the regulation of interphase microtubule dynamics, CLASP also controls the architecture of the bipolar mitotic spindle (Walczak, 2005) and the central spindle (Inoue et al, 2000;Inoue et al, 2004). The central spindle localisation of CLASP depends upon its interaction with PRC1 (Liu et al, 2009), similarly to its Schizosaccharomyces pombe orthologue cls1p (also called peg1p) (Bratman and Chang, 2007).…”

Section: Claspmentioning

confidence: 99%

Cytokinesis microtubule organisers at a glance

Lee

Davies

Mishima

2012

Journal of Cell Science

View full text Add to dashboard Cite

“…By performing a high copy suppressor (HCS) screen, we have identified 10 genes that when overexpressed rescue the HU sensitivity and spindle expansion defect of the spc24-9 mutant strain. We characterized the rescue function of two of these genes-Stu1, a MT-associated protein that shares a region of similarity to the CLASP/Mast/Orbit subfamily of MT plus-end tracking proteins, and Stu2, a member of the conserved Dis1/XMAP215 family of MT plus-end binding proteins (Inoue et al, 2000;Yin et al, 2002;Gard et al, 2004). We demonstrate that both Stu1 and Stu2 are localized to the kinetochore early in the cell cycle and that Stu2 kinetochore binding depends on Spc24.…”

mentioning

confidence: 99%

Spc24 and Stu2 Promote Spindle Integrity When DNA Replication Is Stalled

McQueen

Cuschieri²,

Vogel

et al. 2007

MBoC

View full text Add to dashboard Cite

The kinetochore, a protein complex that links chromosomes to microtubules (MTs), is required to prevent spindle expansion during S phase in budding yeast, but the mechanism of how the kinetochore maintains integrity of the bipolar spindle before mitosis is not well understood. Here, we demonstrate that a mutation of Spc24, a component of the conserved Ndc80 kinetochore complex, causes lethality when cells are exposed to the DNA replication inhibitor hydroxyurea (HU) due to premature spindle expansion and segregation of incompletely replicated DNA. Overexpression of Stu1, a CLASP-related MT-associated protein or a truncated form of the XMAP215 orthologue Stu2 rescues spc24-9 HU lethality and prevents spindle expansion. Truncated Stu2 likely acts in a dominant-negative manner, because overexpression of full-length STU2 does not rescue spc24-9 HU lethality, and spindle expansion in spc24-9 HU-treated cells requires active Stu2. Stu1 and Stu2 localize to the kinetochore early in the cell cycle and Stu2 kinetochore localization depends on Spc24. We propose that mislocalization of Stu2 results in premature spindle expansion in S phase stalled spc24-9 mutants. Identifying factors that restrain spindle expansion upon inhibition of DNA replication is likely applicable to the mechanism by which spindle elongation is regulated during a normal cell cycle. INTRODUCTIONPreserving the integrity of the genome is a fundamental requirement for eukaryotic cell viability. DNA replication must be completed before segregation of the chromosomes to prevent the transmission of partially replicated chromosomes to daughter cells. In the budding yeast Saccharomyces cerevisiae, cells undergo a closed mitosis and the microtubule (MT) organizing centers, or spindle pole bodies (SPBs), are imbedded in the nuclear envelope. SPB duplication begins at the end of anaphase and spindle formation begins during S phase when duplicated SPBs separate from each other (Adams and Kilmartin, 1999;Jaspersen and Winey, 2004). Because chromosomes remain attached to kinetochore MTs throughout the cell cycle, spindle expansion must be restrained until all 16 chromosomes have duplicated and kinetochores on sister chromatids have formed bipolar MT attachments. When DNA replication is stalled by hydroxyurea (HU) treatment, cells arrest with a large bud, an undivided nucleus positioned at the mother-bud neck and a short bipolar spindle (Allen et al., 1994). Maintaining a short spindle is crucial for cell survival during HU-induced arrest, which activates the DNA replication checkpoint effectors Mec1 and Rad53 (Kolodner et al., 2002). When mec1 and rad53 mutants are treated with HU, the DNA replication checkpoint is not activated, and, as a result, replication forks are not stabilized, the spindle expands, and unequal division of incompletely replicated nuclear material occurs-all of these events contribute to cell lethality (Allen et al., 1994;Weinert et al., 1994;Lopes et al., 2001).In human cells, stalled replication forks activate the ataxia telangiectasia mutat...

show abstract

Orbit, a Novel Microtubule-Associated Protein Essential for Mitosis inDrosophila melanogaster

Cited by 122 publications

References 57 publications

Poleward Tubulin Flux in Spindles: Regulation and Function in Mitotic Cells

Poleward Tubulin Flux in Spindles: Regulation and Function in Mitotic Cells

Cytokinesis microtubule organisers at a glance

Spc24 and Stu2 Promote Spindle Integrity When DNA Replication Is Stalled

Contact Info

Product

Resources

About