CRM1 Is an Export Receptor for Leucine-Rich Nuclear Export Signals

Abstract

CRM1 is distantly related to receptors that mediate nuclear protein import and was previously shown to interact with the nuclear pore complex. Overexpression of CRM1 in Xenopus oocytes stimulates Rev and U snRNA export from the nucleus. Conversely, leptomycin B, a cytotoxin that is shown to bind to CRM1 protein, specifically inhibits the nuclear export of Rev and U snRNAs. In vitro, CRM1 forms a leptomycin B-sensitive complex involving cooperative binding of both RanGTP and the nuclear export signal (NES) from either the Rev or PKI proteins. We conclude that CRM1 is an export receptor for leucine-rich nuclear export signals and discuss a model for the role of RanGTP in CRM1 function and in nuclear export in general.

The adenovirus type 5 E1B-55K oncoprotein is a highly active shuttle protein and shuttling is independent of E4orf6, p53 and Mdm2

“…The same localization and tra cking pattern was observed in the p53 negative cell line H1299 (e,f) or the p53 and Mdm2 negative cell line X174 (g,h). The presence of p21Rex-BFP in the same cell was veri®ed using the appropriate ®lter to detect BFP and mediated by the CRM1 export pathway (Fornerod et al, 1997;Heger et al, 1999;Stauber et al, 1998a). To understand how adenoviral or retroviral shuttle proteins exploit this export pathway, we reasoned that a shuttle protein with a high a nity for common export factors should be able to a ect the tra cking of a shuttle protein with a lower a nity in trans.…”

“…To function as a RNA-transporter these proteins need, besides an RNA-binding domain, a nuclear localization signal (NLS) and a nuclear export signal (NES) (for detailed reviews see: GoÈ rlich, 1997GoÈ rlich, , 1998. Especially, the mechanism of nuclear export is currently actively studied and several candidate protein-transport mediators have been identi®ed (Bevec and Hauber, 1997;Fornerod et al, 1997).…”

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).…”