The Ran GTPase regulates kinetochore function.
The Ran GTPase is required for nuclear assembly, nuclear transport, spindle assembly, and mitotic regulation. While the first three processes are relatively well understood, details of Ran's role in mitotic progression remain obscure. We have found that elevated levels of Ran's exchange factor (RCC1) abrogate the spindle assembly checkpoint in Xenopus egg extracts, restore APC/C activity, and disrupt the kinetochore localization of checkpoint regulators, including Mad2, CENP-E, Bub1, and Bub3. Depletion of Ran's GTPase activating protein (RanGAP1) and its accessory factor (RanBP1) similarly abrogates checkpoint arrest. By contrast, the addition of RanGAP1 and RanBP1 to extracts with exogenous RCC1 restores the spindle checkpoint. Together, these observations suggest that the spindle checkpoint is directly responsive to Ran-GTP levels. Finally, we observe a clear wave of RCC1 association to mitotic chromosomes at the metaphase-anaphase transition in normal cycling extracts, suggesting that this mechanism has an important role in unperturbed cell cycles.
Arnaoutov
Alexei
A
Laboratory of Gene Regulation and Development, NICHD, NIH, Building 18, Room 106, 20892, Bethesda, MD, USA
Dasso
Mary
M
D000818:Animals; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D002875:Chromosomes / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D008941:Spindle Apparatus / Q000502:physiology; D014981:Xenopus; D029867:Xenopus Proteins; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; C499304:RCC1 protein, Xenopus; C062521:RCC1 protein, human; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D020558:GTP Phosphohydrolases; D020931:ran GTP-Binding Protein