Ran is an abundant GTPase that is highly conserved in eukaryotic cells and has been implicated in many aspects of nuclear structure and function, especially determining the directionality of nucleocytoplasmic transport during interphase.

Cell-free systems have recently shown that Ran plays distinct roles in mitotic spindle assembly and nuclear envelope (NE) formation in vitro.

During spindle assembly, Ran controls the formation of complexes with importins, the same effectors that control nucleocytoplasmic transport.

References

 Clarke PR, Zhang C. Ran GTPase: a master regulator of nuclear structure and function during the eukaryotic cell division cycle? Trends Cell Biol. 2001 Sep;11(9):366-71. PMID: #11514190#