Ran and nuclear transport

The last several years have witnessed an explosion in our understanding of how proteins and RNAs traffic into and out of the nucleus. Although an increasing number of proteins have been implicated in different nuclear transport pathways, the small GTPase Ran appears to play a central role in coordinating and driving much of this nuclear traffic. Recently there have been several excellent reviews describing the multiple pathways of nuclear transport (1-5); consequently this review will focus on what is currently known about Ran and its biochemical properties and what is presently understood of the role of the Ran GTPase cycle during nuclear transport.