title: Karyopherin beta 2B participates in mRNA export from the nucleus.
abstract: Transport of macromolecules between the cell nucleus and cytoplasm occurs through the nuclear pores and is mediated by soluble carriers known as karyopherins (Kaps), transportins, importins, or exportins. We report that Kap beta2B (transportin-2) forms complexes with the mRNA export factor TAP in the presence of RanGTP, as shown by coimmunoprecipitation from HeLa cells. The interaction strictly depends on the presence of RanGTP. In digitonin-permeabilized cells, Kap beta2B mediates TAP-GFP export from the nuclei in the presence of RanGTP. A TAP mutant that does not coimmunoprecipitate with Kap beta2B is also not exported by Kap beta2B. In the permeabilized cells assay, TAP is also exported independently of Kap beta2B by direct interaction with nucleoporins, in agreement with previous reports. The export rate is, however, significantly lower than the Kap beta2B-mediated pathway. Both Kap beta2B and TAP are present and enriched in the poly(A)(+) RNA complexes isolated from HeLa cell nuclear lysates. Poly(A)(+) RNA strongly accumulates in the nuclei of HeLa cells treated with Kap beta2B short interfering RNA, indicating that Kap beta2B is involved in the export of at least a large proportion of the mRNA species. The export of beta-actin and GAPDH mRNA is also inhibited, whereas 28S RNA is not affected. The data support the conclusion that Kap beta2B participates directly in the export of a large proportion of cellular mRNAs, and TAP connects Kap beta2B to the mRNAs to be exported.
authors.affiliation: The Carl C. Icahn Institute for Gene Therapy and Molecular Medicine, Mount Sinai School of Medicine, Box 1496, 1425 Madison Avenue, New York, NY 10029, USA.
authors.forename: Monee K
authors.initials: MK
authors.lastname: Shamsher
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ploski
authors.forename: Aurelian
authors.initials: A
authors.lastname: Radu
mesh_terms: D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism*; D015536:Down-Regulation; D020690:GTPase-Activating Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism*; D011061:Poly A / Q000378:metabolism; D039102:Poly(A)-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; C122111:NXF1 protein, human; D029543:Nucleocytoplasmic Transport Proteins; D039102:Poly(A)-Binding Proteins; C092317:RANGAP1 protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; C503621:TNPO2 protein, human; D028961:beta Karyopherins; D011061:Poly A