Abstract
Interactions between Nup50 and soluble transport factors underlie the efficiency of certain nucleocytoplasmic transport pathways. The platform on which these interactions take place is important to building a complete understanding of nucleocytoplasmic trafficking. Nup153 is the nucleoporin that provides this scaffold for Nup50. Here, we have delineated requirements for the interaction between Nup153 and Nup50, revealing a dual interface. An interaction between Nup50 and a region in the unique N-terminal region of Nup153 is critical for the nuclear pore localization of Nup50. A second site of interaction is at the distal tail of Nup153 and is dependent on importin α. Both of these interactions involve the N-terminal domain of Nup50. The configuration of the Nup153-Nup50 partnership suggests that the Nup153 scaffold provides not just a means of pore targeting for Nup50 but also serves to provide a local environment that facilitates bringing Nup50 and importin α together, as well as other soluble factors involved in transport. Consistent with this, disruption of the Nup153-Nup50 interface decreases efficiency of nuclear import.
Highlights
An interaction network involving soluble factors and nuclear pore proteins underlies nucleocytoplasmic transport
The configuration of the Nup153-Nup50 partnership suggests that the Nup153 scaffold provides not just a means of pore targeting for Nup50 and serves to provide a local environment that facilitates bringing Nup50 and importin ␣ together, as well as other soluble factors involved in transport
Nup153 overlap spatially and participate in similar processes, a fundamental question that has not been addressed is whether this partnership is limited to a subset of Nup50 found in the cell
Summary
An interaction network involving soluble factors and nuclear pore proteins underlies nucleocytoplasmic transport. A broader repertoire of proteins guides the efficiency of transport and provides additional layers of regulation and fidelity to this process One such protein is Nup50/Npap (referred to here as Nup50), which was discovered as a nuclear pore-associated protein [2] and first examined in the context of binding and regulating the cell cycle. There is not complete agreement on the precise mechanism by which Nup contributes to import, its interactions with soluble transport factors are well characterized In this regard, Nup has three main functional domains: an N-terminal region that interacts with importin ␣ (N); a central region, with phenylalanine-glycine (FG) motifs shared by many nucleoporins, that provides a docking site for importin  (F); and a C-terminal region that confers binding to the transport regulator Ran (R) (see Fig. 1A) [10]. Characterization of the Nup50-Nup153 Interaction we have characterized the Nup153-Nup partnership to provide critical information about the context of Nup function
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