 During prophase, the steep gradient in RanGTP-RanGDP ratio at the nuclear pores breaks down as the nuclear envelope becomes leaky and disassembles.RanGTP concentration stays high around the chromosomes as RCC1, a nucleotide exchange factor, stays attached to chromatin.RanBP2 (Nup358) and RanGAP move to the kinetochores where they facilitate the attachment of spindle fibers to chromosomes.