Complex formation among the RNA export proteins Nup98, Rae1/Gle2, and TAP.
Most nucleocytoplasmic traffic through the nuclear pore complex is mediated by soluble receptors of the importin/exportin or karyopherin family. mRNA export is unique in that no receptor of this family has been implicated in trafficking of the bulk of mRNAs. Instead, many diverse proteins have been linked to mRNA export, but an all-encompassing model remains elusive. Understanding how these proteins interact with each other is central to the development of such a model. Here, we have focused on the interactions between three proteins implicated in mRNA export, Nup98, Rae1/Gle2, and TAP. We have defined the binary complexes that form among these proteins. We find that Gle2 requires two sites within TAP for stable interaction. Strikingly, rather than a general affinity for all nucleoporin FG repeats, TAP has highest affinity for a specific region within the GLFG domain of Nup98, indicating that not all repeats are identical in function. We have established that the ternary complex can form through simultaneous binding of both Gle2 and TAP to adjacent sites on Nup98. In contrast, Nup98 competes with TAP for Gle2 binding; when bound to Nup98, Gle2 no longer interacts directly with TAP. From these interactions, we propose that Gle2 may act to deliver TAP to Nup98 and that this may represent the first in a series of interactions between an export complex and a nucleoporin.
Blevins
Melanie B
MB
Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Smith
Ashley M
AM
Phillips
Erica M
EM
Powers
Maureen A
MA
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000378:metabolism*; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D001665:Binding Sites; D003001:Cloning, Molecular; D034521:Nuclear Matrix-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D022022:Nuclear Pore / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D014981:Xenopus
D018528:ATP-Binding Cassette Transporters; D034521:Nuclear Matrix-Associated Proteins; D028861:Nuclear Pore Complex Proteins; D029543:Nucleocytoplasmic Transport Proteins; C490522:RAE1 protein, human; D012333:RNA, Messenger; C093350:nuclear pore complex protein 98