EVIDENCE FOR A ROLE OF CRM1 IN SIGNAL-MEDIATED NUCLEAR-PROTEIN EXPORT

Chromosome maintenance region 1 (CRM1), a protein that shares sequence similarities with the karyopherin beta family of proteins involved in nuclear import pathway, was shown to form a complex with the leucine- rich nuclear export signal (NES), This interaction was inhibited by le ptomycin B, a drug that prevents the function of the CRM1 protein in y east, To analyze the role of the CRM1-NES interaction in nuclear expor t, a transport assay based on semipermeabilized cells was developed. I n this system, which reconstituted NES-, cytosol-, and energy-dependen t nuclear export, leptomycin B specifically blocked export of NES-cont aining proteins, Thus, the CRM1 protein could act as a NES receptor in volved in nuclear protein export.