Ran localizes around the microtubule spindle in vivo during mitosis in Drosophila embryos.
The GTPase Ran regulates multiple cellular functions throughout the cell cycle, including nucleocytoplasmic transport, nuclear membrane assembly, and spindle assembly. Ran mediates spindle assembly by affecting multiple spindle assembly pathways: microtubule dynamics, microtubule motor activity, and spindle pole assembly. Ran is predicted to facilitate spindle assembly by remaining in the GTP-bound state around the chromatin in mitosis. Here, we directly test the central tenet of this hypothesis in vivo by determining the cellular localization of Ran pathway components in Drosophila embryos. We find that, during mitosis, RCC1, the nucleotide exchange factor for Ran, is associated with chromatin, while Ran and RanL43E, an allele locked in the GTP-bound state, localize around the spindle. In contrast, nuclear proteins redistribute throughout the embryo upon nuclear envelope breakdown (NEB). Thus, in vivo RanGTP has the correct spatial localization within the cell to modulate spindle assembly.
Trieselmann
Nadia
N
Department of Medical Genetics and Microbiology, University of Toronto, 1 King's College Circle, Ontario M5S 1A8, Canada.
Wilde
Andrew
A
D000818:Animals; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D004330:Drosophila / Q000196:embryology; D029721:Drosophila Proteins / Q000032:analysis; D020690:GTPase-Activating Proteins / Q000032:analysis; D005982:Glutathione Transferase / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000378:metabolism*
D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; C118002:RanGAP protein, Drosophila; D011993:Recombinant Fusion Proteins; D028961:beta Karyopherins; D005982:Glutathione Transferase; D020931:ran GTP-Binding Protein