Microtubule minus-end aster organization is driven by processive HSET-tubulin clusters

• Published in: Nature communications Vol. 9; no. 1; pp. 2659 - 14
• Main Authors: Norris, Stephen R., Jung, Seungyeon, Singh, Prashant, Strothman, Claire E., Erwin, Amanda L., Ohi, Melanie D., Zanic, Marija, Ohi, Ryoma
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09.07.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 14/35; 14/63; 631/80/128; 631/80/128/1653; 631/80/128/1923; 631/80/128/2343; 631/80/641/1656; 82/80; 82/83; Adenosine triphosphatase; Animals; Cell cycle; Cell Tracking - methods; Clusters; Cytoskeleton; Developmental biology; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; HeLa Cells; Humanities and Social Sciences; Humans; Kinesin; Kinesin - genetics; Kinesin - metabolism; Microscopy, Fluorescence - methods; Microtubules - metabolism; Mitosis; Molecular chains; Molecular Motor Proteins - metabolism; Motility; Motors; multidisciplinary; Protein Binding; Science; Science (multidisciplinary); Time-Lapse Imaging - methods; Tubulin; Tubulin - metabolism
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-04991-2

Higher-order structures of the microtubule (MT) cytoskeleton are comprised of two architectures: bundles and asters. Although both architectures are critical for cellular function, the molecular pathways that drive aster formation are poorly understood. Here, we study aster formation by human minus-end-directed kinesin-14 (HSET/ KIFC1 ). We show that HSET is incapable of forming asters from preformed, nongrowing MTs, but rapidly forms MT asters in the presence of soluble (non-MT) tubulin. HSET binds soluble (non-MT) tubulin via its N-terminal tail domain to form heterogeneous HSET-tubulin clusters containing multiple motors. Cluster formation induces motor processivity and rescues the formation of asters from nongrowing MTs. We then show that excess soluble (non-MT) tubulin stimulates aster formation in HeLa cells overexpressing HSET during mitosis. We propose a model where HSET can toggle between MT bundle and aster formation in a manner governed by the availability of soluble (non-MT) tubulin. Microtubules (MT) form higher-order structures such as asters, but the molecular pathway underlying aster formation remains unclear. Here authors demonstrate that the kinesin-14, HSET, clusters with soluble (nonMT) tubulin via its N-terminal tail domain and thereby promotes MT aster formation.