XMAP215 is a microtubule nucleation factor that functions synergistically with the ?-tubulin ring complex.

ABSTRACT: How microtubules (MTs) are generated in the cell is a major question in understanding how the cytoskeleton is assembled. For several decades, ?-tubulin has been accepted as the universal MT nucleator of the cell. Although there is evidence that ?-tubulin complexes are not the sole MT nucleators, identification of other nucleation factors has proven difficult. Here, we report that the well-characterized MT polymerase XMAP215 (chTOG/Msps/Stu2p/Alp14/Dis1 homologue) is essential for MT nucleation in Xenopus egg extracts. The concentration of XMAP215 determines the extent of MT nucleation. Even though XMAP215 and the ?-tubulin ring complex (?-TuRC) possess minimal nucleation activity individually, together, these factors synergistically stimulate MT nucleation in vitro. The amino-terminal TOG domains 1-5 of XMAP215 bind to ??-tubulin and promote MT polymerization, whereas the conserved carboxy terminus is required for efficient MT nucleation and directly binds to ?-tubulin. In summary, XMAP215 and ?-TuRC together function as the principal nucleation module that generates MTs in cells.

SUBMITTER: Thawani A 

PROVIDER: S-EPMC5926803 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature