RNA export mediated by tap involves NXT1-dependent interactions with the nuclear pore complex.
Nuclear export of ribonucleoprotein complexes requires cis-acting signals and recognition by receptors that mediate translocation through the nuclear pore complex. Translocation is likely to involve a series of physical interactions between the ribonucleoprotein complex and nucleoporins within the nuclear pore complex. Here, we have characterized the function of NXT1 in the context of the Tap-dependent RNA export pathway. Tap has been implicated in the nuclear export of RNA transcripts derived from Mason-Pfizer monkey virus that contain the constitutive transport element. We demonstrate that NXT1 stimulates binding of a Tap-RNA complex to nucleoporins in vitro, and we provide mutational analysis that shows these interactions are necessary for nuclear export of an intron-containing viral mRNA in vivo. Tap contains separate domains for binding to nucleoporins and NXT1, both of which are critical for its export function. RNA export is mediated by a heterodimer of Tap and NXT1, and the function of NXT1 on this pathway is to regulate the affinity of the Tap-RNA complex for nucleoporins within the nuclear pore complex. We propose that NXT1-dependent binding of the Tap-RNA complex to the nucleoporin p62, which we have reconstituted in vitro using recombinant proteins, represents a single step of the translocation reaction.
Lévesque
L
L
Center for Cell Signaling, Department of Biochemistry, University of Virginia, Charlottesville, Virginia 22908, USA.
Guzik
B
B
Guan
T
T
Coyle
J
J
Black
B E
BE
Rekosh
D
D
Hammarskjöld
M L
ML
Paschal
B M
BM
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D016093:Mason-Pfizer monkey virus / Q000235:genetics; D008562:Membrane Glycoproteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D009690:Nucleic Acid Conformation; D029543:Nucleocytoplasmic Transport Proteins; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D014158:Transcription, Genetic
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; C498546:NXT1 protein, human; D028861:Nuclear Pore Complex Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012367:RNA, Viral; D011994:Recombinant Proteins; C073119:TAP1 protein, human; C049312:nuclear pore protein p62; D012313:RNA; D005982:Glutathione Transferase