Microtubule Nucleation in Mitosis by a RanGTP-Dependent Protein Complex

Scrofani, Jacopo; Sardón, Teresa; Meunier, Sylvain; Vernos, Isabelle

doi:10.1016/j.cub.2014.11.025

Cited by 91 publications

(110 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consistent with this notion, the regulatory factors NEDD1 and CDK5RAP2 have a significantly higher turnover rate compared to the γTuRC structural core subunits γ-tubulin, GCP2, GCP3, GCP4, GCP5 and GCP6 (Jakobsen et al, 2011). Moreover, NEDD1 is phosphorylated at multiple sites to specifically control γTuRC function in distinct mitotic nucleation pathways (Gomez-Ferreria et al, 2012;Haren et al, 2009;Johmura et al, 2011;Lüders et al, 2006;Pinyol et al, 2013;Scrofani et al, 2015;Sdelci et al, 2012;Teixidó-Travesa et al, 2010. Future work will show whether human MZT1 is subject to similar regulation.…”

Section: Discussionmentioning

confidence: 89%

MZT1 regulates microtubule nucleation by linking γTuRC assembly to adapter-mediated targeting and activation

Cota

Teixidó-Travesa

Ezquerra

et al. 2017

Journal of Cell Science

135

View full text Add to dashboard Cite

Regulation of the γ-tubulin ring complex (γTuRC) through targeting and activation restricts nucleation of microtubules to microtubuleorganizing centers (MTOCs), aiding in the assembly of ordered microtubule arrays. However, the mechanistic basis of this important regulation remains poorly understood. Here, we show that, in human cells, γTuRC integrity, determined by the presence of γ-tubulin complex proteins (GCPs; also known as TUBGCPs) 2-6, is a prerequisite for interaction with the targeting factor NEDD1, impacting on essentially all γ-tubulin-dependent functions. Recognition of γTuRC integrity is mediated by MZT1, which binds not only to the GCP3 subunit as previously shown, but cooperatively also to other GCPs through a conserved hydrophobic motif present in the N-termini of GCP2, GCP3, GCP5 and GCP6. MZT1 knockdown causes severe cellular defects under conditions that leave γTuRC intact, suggesting that the essential function of MZT1 is not in γTuRC assembly. Instead, MZT1 specifically binds fully assembled γTuRC to enable interaction with NEDD1 for targeting, and with the CM1 domain of CDK5RAP2 for stimulating nucleation activity. Thus, MZT1 is a 'priming factor' for γTuRC that allows spatial regulation of nucleation.

show abstract

Section: Discussionmentioning

confidence: 89%

MZT1 regulates microtubule nucleation by linking γTuRC assembly to adapter-mediated targeting and activation

Cota

Teixidó-Travesa

Ezquerra

et al. 2017

Journal of Cell Science

135

View full text Add to dashboard Cite

show abstract

“…We speculate that because TPX2 has been reported to have two domains that can bind to microtubules (Trieselmann et al, 2003;Vos et al, 2008), it can perhaps bind to two tubulin dimers simultaneously to strengthen the bond between them. Alternatively, oligomerization of TPX2 could allow for binding of two tubulin dimers simultaneously, thereby strengthening the bond between the tubulin dimers (Drechsler et al, 2014;Scrofani et al, 2015). We note that microtubule-associated proteins that exclusively bind to a single subunit in the microtubule lattice, such as a kinesin motor domain, might be less likely to stabilize the bonds between two adjacent tubulin subunits in the lattice, and would thus lack the ability to suppress the off-rate of tubulin subunits from the microtubule tip, even if the protein were to coat the entire microtubule.…”

Section: Discussionmentioning

confidence: 99%

“…1D) is that TPX2 reduces the effective tubulin concentration in solution by sequestering free tubulin into multi-subunit complexes (Gruss et al, 2002;Roostalu et al, 2015;Scrofani et al, 2015). If this is the case, suppressed tubulin subunit on-rates could be an indirect consequence of enhanced formation of tubulin-TPX2 nucleation complexes (Fygenson et al, 1995;Schek et al, 2007;Scrofani et al, 2015). To test this idea, reaction mixtures with and without 50 nM of TPX2, each containing 10 μM of Alexa-Fluor-488-conjugated tubulin with 0.6 mM GTP, were incubated in a tube at 37°C, and then small samples were removed after 5, 20 and 60 min.…”

Section: Tpx2 Slows Tubulin Subunit Off-rates During Microtubule Assementioning

confidence: 99%

Suppression of microtubule assembly kinetics by the mitotic protein TPX2

Reid

Schuster

Mann

et al. 2016

Journal of Cell Science

View full text Add to dashboard Cite

TPX2 is a widely conserved microtubule-associated protein that is required for mitotic spindle formation and function. Previous studies have demonstrated that TPX2 is required for the nucleation of microtubules around chromosomes; however, the molecular mechanism by which TPX2 promotes microtubule nucleation remains a mystery. In this study, we found that TPX2 acts to suppress tubulin subunit off-rates during microtubule assembly and disassembly, thus allowing for the support of unprecedentedly slow rates of plus-end microtubule growth, and also leading to a dramatically reduced microtubule shortening rate. These changes in microtubule dynamics can be explained in computational simulations by a moderate increase in tubulin-tubulin bond strength upon TPX2 association with the microtubule lattice, which in turn acts to reduce the departure rate of tubulin subunits from the microtubule ends. Thus, the direct suppression of tubulin subunit off-rates by TPX2 during microtubule growth and shortening could provide a molecular mechanism to explain the nucleation of new microtubules in the presence of TPX2.

show abstract

“…This startling discovery made symmetrical sense from a nucleation point of view in that γ-TuRC ring complexes were first discovered at the poles of the spindle and act there as the microtubule-nucleating components of the centrosomes. RanGTP has also been found to be present at both kinetochores and centrosomes [34,36,42,45,46]. Importantly, the presence of RanGTP at the kinetochore is vital for Nup107–160/γ-TuRC-microtubule nucleation and counteracts the effects of importin beta (Figure 2A) [42,45,47].…”

Section: Nuclear Pore Proteins Act In Spindle Microtubule Nucleationmentioning

confidence: 99%

Nuclear transport factors: global regulation of mitosis

Forbes

Travesa

Nord

et al. 2015

Current Opinion in Cell Biology

110

View full text Add to dashboard Cite

The unexpected repurposing of nuclear transport proteins from their function in interphase to an equally vital and very different set of functions in mitosis was very surprising. The multi-talented cast when first revealed included the import receptors, importin alpha and beta, the small regulatory GTPase RanGTP, and a subset of nuclear pore proteins. In this review, we report that recent years have revealed new discoveries in each area of this expanding story in vertebrates: (a) The cast of nuclear transport receptors playing a role in mitotic spindle regulation has expanded: both transportin, a nuclear import receptor, and Crm1/Xpo1, an export receptor, are involved in different aspects of spindle assembly. Importin beta and transportin also regulate nuclear envelope and pore assembly. (b) The role of nucleoporins has grown to include recruiting the key microtubule nucleator the γ-TuRC complex and the exportin Crm1 to the mitotic kinetochores of humans. Together they nucleate microtubule formation from the kinetochores towards the centrosomes. (c) New research finds that the original importin beta/RanGTP team have been further co-opted by evolution to help regulate other cellular and organismal activities, ranging from the actual positioning of the spindle within the cell perimeter, to regulation of a newly discovered spindle microtubule branching activity, to regulation of the interaction of microtubule structures with specific actin structures. (d) Lastly, because of the multitudinous roles of karyopherins throughout the cell cycle, a recent large push toward testing their potential as chemotherapeutic targets has begun to yield burgeoning progress in the clinic.

show abstract

Microtubule Nucleation in Mitosis by a RanGTP-Dependent Protein Complex

Cited by 91 publications

References 49 publications

MZT1 regulates microtubule nucleation by linking γTuRC assembly to adapter-mediated targeting and activation

MZT1 regulates microtubule nucleation by linking γTuRC assembly to adapter-mediated targeting and activation

Suppression of microtubule assembly kinetics by the mitotic protein TPX2

Nuclear transport factors: global regulation of mitosis

Contact Info

Product

Resources

About