title: The nucleoporin MEL-28 promotes RanGTP-dependent γ-tubulin recruitment and microtubule nucleation in mitotic spindle formation.
abstract: The GTP-bound form of the Ran GTPase (RanGTP), produced around chromosomes, drives nuclear envelope and nuclear pore complex (NPC) re-assembly after mitosis. The nucleoporin MEL-28/ELYS binds chromatin in a RanGTP-regulated manner and acts to seed NPC assembly. Here we show that, upon mitotic NPC disassembly, MEL-28 dissociates from chromatin and re-localizes to spindle microtubules and kinetochores. MEL-28 directly binds microtubules in a RanGTP-regulated way via its C-terminal chromatin-binding domain. Using Xenopus egg extracts, we demonstrate that MEL-28 is essential for RanGTP-dependent microtubule nucleation and spindle assembly, independent of its function in NPC assembly. Specifically, MEL-28 interacts with the γ-tubulin ring complex and recruits it to microtubule nucleation sites. Our data identify MEL-28 as a RanGTP target that functions throughout the cell cycle. Its cell cycle-dependent binding to chromatin or microtubules discriminates MEL-28 functions in interphase and mitosis, and ensures that spindle assembly occurs only after NPC breakdown.
authors: 1] Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany [2] European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors: Hideki
authors: H
authors: Yokoyama
authors: European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors: Birgit
authors: B
authors: Koch
authors: European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors: Rudolf
authors: R
authors: Walczak
authors: Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
authors: Fulya
authors: F
authors: Ciray-Duygu
authors: Centre for Organismal Studies (COS), Im Neuenheimer Feld 230, 69120 Heidelberg, Germany.
authors: Juan Carlos
authors: JC
authors: González-Sánchez
authors: Centre for Organismal Studies (COS), Im Neuenheimer Feld 230, 69120 Heidelberg, Germany.
authors: Damien P
authors: DP
authors: Devos
authors: European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors: Iain W
authors: IW
authors: Mattaj
authors: Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
authors: Oliver J
authors: OJ
authors: Gruss
mesh_terms: D000818:Animals; D002843:Chromatin / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008938:Mitosis; D022022:Nuclear Pore / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000378:metabolism*
chemical_list: C525081:AHCTF1 protein, Xenopus; D002843:Chromatin; D004268:DNA-Binding Proteins; D008869:Microtubule-Associated Proteins; D014157:Transcription Factors; D014404:Tubulin; D029867:Xenopus Proteins; D020931:ran GTP-Binding Protein