RCC1 plays a crucial role in the regulation of the small Ras-related protein Ran, which is essential for various cellular processes, including DNA replication and the transport of RNA and proteins through the nuclear pore complex. RCC1 functions as a guanine nucleotide exchange factor, facilitating the conversion of inactive Ran GDP to active Ran GTP, thereby influencing the dynamics of mitosis and nuclear transport. This regulation is particularly important because the balance between Ran GTP and Ran GDP is critical for maintaining proper cellular function and ensuring accurate cell division. The interaction of RCC1 with other proteins, such as Ran GAP1 and Ran BP1, highlights RCC1′s role in a complex regulatory network that governs cellular processes.