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Publication
Nonrandom ?-TuNA-dependent spatial pattern of microtubule nucleation at the
Golgi.
Authors Sanders AAWM, Chang K, Zhu X, Thoppil RJ, Holmes WR, Kaverina I
Submitted By Submitted Externally on 11/27/2017
Status Published
Journal Molecular biology of the cell
Year 2017
Date Published 11/1/2017
Volume : Pages 28 : 3181 - 3192
PubMed Reference 28931596
Abstract Noncentrosomal microtubule (MT) nucleation at the Golgi generates MT network
asymmetry in motile vertebrate cells. Investigating the Golgi-derived MT (GDMT)
distribution, we find that MT asymmetry arises from nonrandom nucleation sites
at the Golgi (hotspots). Using computational simulations, we propose two
plausible mechanistic models of GDMT nucleation leading to this phenotype. In
the "cooperativity" model, formation of a single GDMT promotes further
nucleation at the same site. In the "heterogeneous Golgi" model, MT nucleation
is dramatically up-regulated at discrete and sparse locations within the Golgi.
While MT clustering in hotspots is equally well described by both models,
simulating MT length distributions within the cooperativity model fits the data
better. Investigating the molecular mechanism underlying hotspot formation, we
have found that hotspots are significantly smaller than a Golgi subdomain
positive for scaffolding protein AKAP450, which is thought to recruit GDMT
nucleation factors. We have further probed potential roles of known
GDMT-promoting molecules, including ?-TuRC-mediated nucleation activator
(?-TuNA) domain-containing proteins and MT stabilizer CLASPs. While both ?-TuNA
inhibition and lack of CLASPs resulted in drastically decreased GDMT nucleation,
computational modeling revealed that only ?-TuNA inhibition suppressed hotspot
formation. We conclude that hotspots require ?-TuNA activity, which facilitates
clustered GDMT nucleation at distinct Golgi sites.




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