Final answer:
The drug's effect on nuclear transport would block the ability of Ran to exchange GDP for GTP, impairing the transport of substances into and out of the nucleus.
Step-by-step explanation:
In certain cancers, the GTPase activity of the RAS G-protein is inhibited, preventing the hydrolysis of GTP into GDP. This inhibition affects downstream cellular events, including nuclear transport. One of the main players in nuclear transport is the protein Ran, which relies on the exchange of GDP for GTP to function properly. When the ability of Ran to make this exchange is blocked, it impairs the transport of molecules into and out of the nucleus.