Cellular requirements for CRM1 import and export.

We studied the cellular requirements for the translocation of CRM1 (exportin 1) between the nucleus and the cytoplasm. CRM1 import requires neither ATP, Ran, Ran-dependent GTP hydrolysis, nor a particular temperature. CRM1 and importin beta compete with each other during their import. Thus, CRM1 is able to enter the nucleus in a manner similar to importinbeta. In contrast, the in vivo export of CRM1 involves ATP-consuming step(s).