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Ran is associated with chromosomes during starfish oocyte meiosis and embryonic mitoses

Published online by Cambridge University Press:  16 July 2018

Beth Hinkle ,
Melissa M. Rolls ,
Pascal Stein ,
Tom Rapoport  and
Mark Terasaki
Beth Hinkle
Affiliation:
Marine Biological Laboratory, Woods Hole, MA 02543, USA Department of Physiology, University of Connecticut Health Center, Farmington, CT 06032, USA
Melissa M. Rolls
Affiliation:
Department of Cell Biology and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
Pascal Stein
Affiliation:
Department of Cell Biology and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
Tom Rapoport
Affiliation:
Department of Cell Biology and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
Mark Terasaki
Affiliation:
Marine Biological Laboratory, Woods Hole, MA 02543, USA Department of Physiology, University of Connecticut Health Center, Farmington, CT 06032, USA
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Extract

Ran is an abundant small G protein that has a central role in nuclear transport during interphase. Ran function depends on distinct pools of RanGTP in the nucleus and RanGDP in the cytoplasm, which are maintained by compartmentalisation of the nucleotide exchange and GTPase activating proteins for Ran. RCC1 (Regulator of Chromosome Condensation) is the only known guanine nucleotide exchange factor for Ran and is associated with chromatin. RanGAPl together with RanBPl are the primary GTPase activator proteins and are located in the cytoplasm.

Ran function in nuclear transport is clearly inactivated after the nuclear envelope has disassembled during mitosis. There is now evidence that Ran plays a role in organising the spindle. Experiments using well-characterised cell-free extracts from meiotic metaphase II arrested Xenopus eggs suggest that Ran regulates microtubules involved in spindle assembly (Carazo-Salas et al., 1999; Kalab et al., 1999; Ohba et al., 1999; Wilde & Zheng, 1999). These experiments demonstrate that high levels of RanGTP or GTP-locked forms of Ran result in aster formation and can cause formation of bipolar spindles in the absence of centrosomes or chromosomes. In contrast, reduction of RanGTP blocks centriole- and chromatin-dependent aster formation.

Type
Special Lecture for Citizens
Information
Zygote , Volume 8 , supplement S1: Proceedings of the International Symposium on Fertilization and Development of Sea Urchin and Marine Invertebrates , December 1999 , pp. S91
Copyright
Copyright © Cambridge University Press 1999

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