The Nup107-160 complex and gamma-TuRC regulate microtubule polymerization at kinetochores.
The metazoan nuclear pore complex (NPC) disassembles during mitosis, and many of its constituents distribute onto spindles and kinetochores, including the Nup107-160 sub-complex. We have found that Nup107-160 interacts with the gamma-tubulin ring complex (gamma-TuRC), an essential and conserved microtubule nucleator, and recruits gamma-TuRC to unattached kinetochores. The unattached kinetochores nucleate microtubules in a manner that is regulated by Ran GTPase; such microtubules contribute to the formation of kinetochore fibres (k-fibres), microtubule bundles connecting kinetochores to spindle poles. Our data indicate that Nup107-160 and gamma-TuRC act cooperatively to promote spindle assembly through microtubule nucleation at kinetochores: HeLa cells lacking Nup107-160 or gamma-TuRC were profoundly deficient in kinetochore-associated microtubule nucleation. Moreover, co-precipitated Nup107-160- gamma-TuRC complexes nucleated microtubule formation in assays using purified tubulin. Although Ran did not regulate microtubule nucleation by gamma-TuRC alone, Nup107-160-gamma-TuRC complexes required Ran-GTP for microtubule nucleation. Collectively, our observations show that Nup107-160 promotes spindle assembly through Ran-GTP-regulated nucleation of microtubules by gamma-TuRC at kinetochores, and reveal a relationship between nucleoporins and the microtubule cytoskeleton.
Mishra
Ram Kumar
RK
Laboratory of Gene Regulation and Development, NICHD/NIH, Bethesda, MD 20892, USA.
Chakraborty
Papia
P
Arnaoutov
Alexei
A
Fontoura
Beatriz M A
BM
Dasso
Mary
M
D000818:Animals; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D018386:Kinetochores / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism*; D022022:Nuclear Pore / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D008941:Spindle Apparatus; D014404:Tubulin / Q000378:metabolism*; D014981:Xenopus; D020931:ran GTP-Binding Protein / Q000378:metabolism
C512772:NUP107 protein, human; C440251:NUP160 protein, human; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D014404:Tubulin; D020931:ran GTP-Binding Protein