Ran is a GTPase of the Ras superfamily. Until recently, its primary role was believed to be in interphase, regulating nucleocytoplasmic transport (1). However, recent studies have identified additional roles for Ran in regulating spindle assembly and maintenance in mitosis(2-10).In addition, Ran regulates nuclear-membrane assembly upon exit from mitosis(11,12).This chapter focuses on the regulatory role of Ran in spindle assembly and maintenance, outlining techniques used to study the effects of Ran on the microtubule cytoskeleton.
