Evidence for a Role of CRM1 in Signal-Mediated Nuclear Protein Export

Abstract

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 leptomycin B, a drug that prevents the function of the CRM1 protein in yeast. To analyze the role of the CRM1-NES interaction in nuclear export, a transport assay based on semipermeabilized cells was developed. In this system, which reconstituted NES-, cytosol-, and energy-dependent nuclear export, leptomycin B specifically blocked export of NES-containing proteins. Thus, the CRM1 protein could act as a NES receptor involved in nuclear protein export.

Pyk2 cytonuclear localization: mechanisms and regulation by serine dephosphorylation

“…This double mutation similarly decreased the nuclear accumulation of GFPPyk2 700-841 induced by leptomycin B (LMB) (Fig. 2c) a toxin that blocks the nuclear export by competing with the binding of NES to CRM1 [39,40]. These findings strongly supported the idea that S 747 PT was a bona fide NTS involved in the control of GFP-Pyk2 700-841 nuclear import.…”

Titration of cellular export factors, but not heteromultimerization, is the molecular mechanism of trans-dominant HTLV-1 Rex mutants

“…In analogy to shuttling cytoplasmic Rev mutants (Stauber et al, 1998a) inactivation of the NES resulted in nuclear accumulation of Rexp21IW18-GFP (compare Figures 2c and 3c). Recent reports demonstrated that the Rex and Rev export pathways are mediated by the export factor CRM1 and can be blocked by the drug leptomycin B (LMB) (Fornerod et al, 1997;Fukuda et al, 1997;Ossareh-Nazari et al, 1997;Stade et al, 1997;Wol et al, 1997). Thus, to verify the shuttling of Rexp21-GFP by an independent method, we blocked the CRM1 mediated nuclear export pathway using LMB.…”

“…A leucine-rich nuclear export signal (NES), identi®ed between amino acids 79 and 99, is essential for nucleo-cytoplasmic tra cking and thus Rex function (Bogerd et al, 1996;Kim et al, 1996;Palmeri and Malim, 1996;Weichselbraun et al, 1992b). Factors reported to interact directly with the NES domain include the eukaryotic initiation factor 5A (eIF-5A) (Katahira et al, 1995) and the export factor CRM1 (Fornerod et al, 1997;Fukuda et al, 1997;Ossareh-Nazari et al, 1997;Stade et al, 1997).…”

Regulated nuclear localization of stress-responsive factors: how the nuclear trafficking of protein kinases and transcription factors contributes to cell survival

“…Dissociation of the complex is likely to involve the exchange of GTP for GDP on the Ran moiety. It is unclear whether the returning importins carry a di erent cargo back to the cytoplasm, but nuclear export-speci®c importin b family members have been identi®ed that mediate the transport from the nucleus to the cytoplasm of, for example, tRNA (Arts et al, 1998a,b;Hellmuth et al, 1998;Kutay et al, 1998) or of proteins that contain a leucine-rich Nuclear Export Signal (NES); (Fornerod et al, 1997;Fukuda et al, 1997a;Neville et al, 1997;Ossareh-Nazari et al, 1997;Stade et al, 1997). Again, release of the export cargo at the cytoplasmic face of the nuclear pore is likely to involve the hydrolysis of GTP that is bound to the Ran component of the export complex (Bischo and Schlenstedt et al, 1997;Kehlenbach et al, 1999).…”