Complex formation between Tap and p15 affects binding to FG-repeat nucleoporins and nucleocytoplasmic shuttling.
Mammalian Tap-p15 and yeast Mex67p-Mtr2p are conserved and essential mRNA export factor complexes that transport mRNPs through the nuclear pore. Here, we report that the small subunit p15 affects the binding of the large subunit Tap to repeat nucleoporins. BIAcore measurements revealed that recombinant Tap binds with high affinity (K(d) in the nm range) to repeat nucleoporins and dissociates from them very slowly. In contrast, when recombinant Tap was bound to p15, the derived heterodimeric complex exhibited a significant lower affinity to FG-repeat nucleoporins (K(d) in the microm range). Furthermore, when recombinant Tap lacking the N-terminal nuclear localization sequences (TapDeltaNLS) was microinjected in mammalian cells, it did not shuttle; however, TapDeltaNLS with bound p15 efficiently shuttles between nucleus and cytoplasm. We conclude that heterodimerization of Tap and p15 is required for shuttling of the functional Tap-p15 mRNA exporter complex.
Katahira
Jun
J
Division of Immunology, Section of Cellular Interactions and Morphogenesis, Institute for Molecular and Cellular Biology, Osaka University, 1-3 Yamadaoka Suita, Osaka 565-0871, Japan.
Straesser
Katja
K
Saiwaki
Takuya
T
Yoneda
Yoshihiro
Y
Hurt
Ed
E
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism*; D050762:Cyclin-Dependent Kinase Inhibitor p15; D003593:Cytoplasm / Q000378:metabolism*; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D028861:Nuclear Pore Complex Proteins / Q000737:chemistry / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D020449:Repetitive Sequences, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; C493966:CDKN2B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; C498546:NXT1 protein, human; D028861:Nuclear Pore Complex Proteins; D029543:Nucleocytoplasmic Transport Proteins; C073119:TAP1 protein, human; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins