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.