Ran, a GTPase involved in nuclear processes: its regulators and effectors

Ran is a small GTPase that has been implicated in a variety of nuclear processes, including the maintainance of nuclear structure, protein import, mRNA processing and export, and cell cycle regulation. There has been significant progress in determining the role of Ran in nuclear protein import. However, it has been unclear whether this role is sufficient to account for the diverse effects of disrupting Ran functions. Recently, several proteins have been identified that bind specifically to Ran and are, therefore, possible effectors. Other experiments using dominant mutants of Ran that block its GTP/GDP cycle have suggested that Ran may have multiple roles. Here, these results are summarised and discussed with respect to the action of Ran.