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

Norris SR, Jung S, Singh P, Strothman CE, Erwin AL, Ohi MD, Zanic M, Ohi R
Nat Commun. 2018 9 (1): 2659

PMID: 29985404 · PMCID: PMC6037785 · 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.

MeSH Terms (12)

Animals Cell Tracking Green Fluorescent Proteins HeLa Cells Humans Kinesin Microscopy, Fluorescence Microtubules Molecular Motor Proteins Protein Binding Time-Lapse Imaging Tubulin

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