PT  - JOURNAL ARTICLE
AU  - Jeffrey B. Woodruff
AU  - Beatriz Ferreira Gomes
AU  - Per O. Widlund
AU  - Julia Mahamid
AU  - Anthony A. Hyman
TI  - The centrosome is a selective phase that nucleates microtubules by concentrating tubulin
AID  - 10.1101/093054
DP  - 2016 Jan 01
TA  - bioRxiv
PG  - 093054
4099  - http://biorxiv.org/content/early/2016/12/10/093054.short
4100  - http://biorxiv.org/content/early/2016/12/10/093054.full
AB  - Centrosomes are non-membrane-bound compartments that nucleate microtubule arrays. They consist of nanometer-scale centrioles surrounded by a micron-scale, dynamic assembly of protein called the pericentriolar material (PCM). To study how PCM forms a spherical compartment that nucleates microtubules, we reconstituted PCM-dependent microtubule nucleation in vitro using recombinant C.elegans proteins. We found that macromolecular crowding drives phase separation of the key PCM scaffold protein SPD-5 into spherical droplets that morphologically and dynamically resemble in vivo PCM. These SPD-5 droplets recruited the microtubule polymerase ZYG-9 (XMAP215 homologue) and the microtubule-stabilizing protein TPXL-1 (TPX2 homologue). Together, these three proteins concentrated tubulin ~4- fold over background, which was sufficient to reconstitute nucleation of microtubule asters in vitro. Our results suggest that in vivo PCM is a selective phase that organizes microtubule arrays through localized concentration of tubulin by microtubule effector proteins.One Sentence Summary Phase separation of C. elegans centrosome proteins drive the formation of micron-sized microtubule organizing centers.