The Ran decathlon: multiple roles of Ran

The Ran GTPase system affects many cellular processes, including the regula tion of cell cycle progression, nuclear envelope structure and function, an d nucleocytoplasmic transport. The biochemical basis for the involvement of Ran in nuclear import and export has been well documented, but the direct targets of Ran in other cellular processes have not yet been identified. Th ere is, however, mounting evidence that Ran directly affects at least some of these other cellular processes by mechanisms independent of its role in transport. In this Commentary we discuss evidence linking Ran to different aspects of cell function, and how these multiple facets of Ran's activity m ay relate to each other.