Ran(T24N) promotes both RCC1 bindings to DNA and histones in vitro. The effects of Ran(T24N) require the RCC1 tail. (A) RCC1 binding to DNA is promoted by Ran(T24N). (B) RCC1 binding to core histones is increased by Ran(T24N). (C) Ran(T24N) has no effect on RCC1(Δ1–20) binding to core histones. (D) Core histone binding of RCC1 is increased by Impα3. (E) Conformational switch model. The N-terminal tail of RCC1 is essential for DNA binding but allosterically inhibits association with histones. In its closed state, RCC1 has a low affinity for both DNA and histones. Binding of Ran causes the tail to undergo a conformational switch to an open state, exposing the histone-binding surface and enabling the tail to interact efficiently with DNA. This interaction is enhanced by α-N-methylation. Error bars represent ±SD.