Chromosome region maintenance 1 protein homolog (CRM1) is the Ran-GTP-binding nuclear export receptor for proteins bearing a leucine rich nuclear export signal and RNAs. CRM1 also possesses a mitotic function as it localizes to kinetochores, and withRan-GTP, recruits Ran-GTPase-activating protein (Ran-GAP1) and Ran-binding protein (Ran-BP2) for proper mitotic spindle assembly and chromosome segregation. Additionally, CRM1 is suggested to function as a loading dock of various cell cycle and checkpoint factors such as cyclins, Cdks, p53 and BRCA1, to regulate proper chromosome duplication and genomic stability.