Nuclear export of mRNA by TAP/NXF1 requires two nucleoporin-binding sites but not p15.
Metazoan NXF1/p15 heterodimers promote export of bulk mRNA through nuclear pore complexes (NPC). NXF1 interacts with the NPC via two distinct structural domains, the UBA-like domain and the NTF2-like scaffold, which results from the heterodimerization of the NTF2-like domain of NXF1 with p15. Both domains feature a single nucleoporin-binding site, and they act synergistically to promote NPC translocation. Whether the NTF2-like scaffold (and thereby p15) contributes only to NXF1/NPC association or is also required for other functions, e.g., to impart directionality to the export process by regulating NXF1/NPC or NXF1/cargo interactions, remains unresolved. Here we show that a minimum of two nucleoporin-binding sites is required for NXF1-mediated export of cellular mRNA. These binding sites can be provided by an NTF2-like scaffold followed by a UBA-like domain (as in the wild-type protein) or by two NTF2-like scaffolds or two UBA-like domains in tandem. In the latter case, the export activity of NXF1 is independent of p15. Thus, as for the UBA-like domain, the function of the NTF2-like scaffold is confined to nucleoporin binding. More importantly, two copies of either of these domains are sufficient to promote directional transport of mRNA cargoes across the NPC.
Braun
Isabelle C
IC
European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
Herold
Andrea
A
Rode
Michaela
M
Izaurralde
Elisa
E
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster; D006801:Humans; D016297:Mutagenesis, Site-Directed; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029721:Drosophila Proteins; C122111:NXF1 protein, human; C498546:NXT1 protein, human; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; C498545:Nxt1 protein, Drosophila; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C073119:TAP1 protein, human