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J Cell Biol. 2019 Oct 21. pii: jcb.201902069. doi: 10.1083/jcb.201902069. [Epub ahead of print]

Soluble tubulin is significantly enriched at mitotic centrosomes.

Author information

Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.
Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
Center for Membrane and Cell Physiology and Department of Molecular Physiology and Biological Physics, University of Virginia, School of Medicine, Charlottesville, VA.
Department of Cell Biology and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX.
Centre for Systems Biology Dresden, Dresden, Germany.
Cluster of Excellence Physics of Life, Technische Universität Dresden, Dresden, Germany.
Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
Contributed equally


During mitosis, the centrosome expands its capacity to nucleate microtubules. Understanding the mechanisms of centrosomal microtubule nucleation is, however, constrained by a lack of knowledge of the amount of soluble and polymeric tubulin at mitotic centrosomes. Here we combined light microscopy and serial-section electron tomography to measure the amount of dimeric and polymeric tubulin at mitotic centrosomes in early C. elegans embryos. We show that a C. elegans one-cell stage centrosome at metaphase contains >10,000 microtubules with a total polymer concentration of 230 µM. Centrosomes concentrate soluble α/β tubulin by about 10-fold over the cytoplasm, reaching peak values of 470 µM, giving a combined total monomer and polymer tubulin concentration at centrosomes of up to 660 µM. These findings support in vitro data suggesting that microtubule nucleation in C. elegans centrosomes is driven in part by concentrating soluble tubulin.


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