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Nat Cell Biol. 2014 Aug;16(8):770-8. doi: 10.1038/ncb2996. Epub 2014 Jun 29.

The dynamics of microtubule minus ends in the human mitotic spindle.


During mitotic spindle assembly, γ-tubulin ring complexes (γTuRCs) nucleate microtubules at centrosomes, around chromosomes, and, by interaction with augmin, from pre-existing microtubules. How different populations of microtubules are organized to form a bipolar spindle is poorly understood, in part because we lack information on the dynamics of microtubule minus ends. Here we show that γTuRC is associated with minus ends of non-centrosomal spindle microtubules. Recruitment of γTuRC to spindles occurs preferentially at pole-distal regions, requires nucleation and/or interaction with minus ends, and is followed by sorting of minus-end-bound γTuRC towards the poles. Poleward movement of γTuRC exceeds k-fibre flux, involves the motors dynein, HSET (also known as KIFC1; a kinesin-14 family member) and Eg5 (also known as KIF11; a kinesin-5 family member), and slows down in pole-proximal regions, resulting in the accumulation of minus ends. Thus, in addition to nucleation, γTuRC actively contributes to spindle architecture by organizing microtubule minus ends.

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