Crm1 is a mitotic effector of Ran-GTP in somatic cells.
The Ran GTPase controls multiple cellular processes, including nuclear transport, mitotic checkpoints, spindle assembly and post-mitotic nuclear envelope reassembly. Here we examine the mitotic function of Crm1, the Ran-GTP-binding nuclear export receptor for leucine-rich cargo (bearing nuclear export sequence) and Snurportin-1 (ref. 3). We find that Crm1 localizes to kinetochores, and that Crm1 ternary complex assembly is essential for Ran-GTP-dependent recruitment of Ran GTPase-activating protein 1 (Ran-GAP1) and Ran-binding protein 2 (Ran-BP2) to kinetochores. We further show that Crm1 inhibition by leptomycin B disrupts mitotic progression and chromosome segregation. Analysis of spindles within leptomycin B-treated cells shows that their centromeres were under increased tension. In leptomycin B-treated cells, centromeres frequently associated with continuous microtubule bundles that spanned the centromeres, indicating that their kinetochores do not maintain discrete end-on attachments to single kinetochore fibres. Similar spindle defects were observed in temperature-sensitive Ran pathway mutants (tsBN2 cells). Taken together, our findings demonstrate that Crm1 and Ran-GTP are essential for Ran-BP2/Ran-GAP1 recruitment to kinetochores, for definition of kinetochore fibres and for chromosome segregation at anaphase. Thus, Crm1 is a critical Ran-GTP effector for mitotic spindle assembly and function in somatic cells.
Arnaoutov
Alexei
A
Laboratory of Gene Regulation and Development, NICHD, NIH, Building 18, Room 106, Bethesda, MD 20892-5431, USA.
Azuma
Yoshiaki
Y
Ribbeck
Katharina
K
Joseph
Jomon
J
Boyarchuk
Yekaterina
Y
Karpova
Tatiana
T
McNally
James
J
Dasso
Mary
M
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D045744:Cell Line, Tumor; D020090:Chromosome Segregation / Q000502:physiology; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018386:Kinetochores / Q000378:metabolism* / Q000648:ultrastructure; D008870:Microtubules / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D008938:Mitosis / Q000502:physiology*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000502:physiology; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
D020690:GTPase-Activating Proteins; D028884:Karyopherins; D018832:Molecular Chaperones; D028861:Nuclear Pore Complex Proteins; D011500:Protein Synthesis Inhibitors; D018160:Receptors, Cytoplasmic and Nuclear; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein; C092317:RANGAP1 protein, human; C094493:ran-binding protein 2