Taxonomic distribution of proteins containing ZnF_RBZ domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing ZnF_RBZ domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Nup153 is an M9-containing mobile nucleoporin with a novel Ran-binding domain.

Nakielny S, Shaikh S, Burke B, Dreyfuss G
EMBO J. 1999; 18: 1982-95

We employed a phage display system to search for proteins that interact with transportin 1 (TRN1), the import receptor for shuttling hnRNP proteins with an M9 nuclear localization sequence (NLS), and identified a short region within the N-terminus of the nucleoporin Nup153 which binds TRN1. Nup153 is located at the nucleoplasmic face of the nuclear pore complex (NPC), in the distal basket structure, and functions in mRNA export. We show that this Nup153 TRN1-interacting region is an M9 NLS. We found that both import and export receptors interact with several regions of Nup153, in a RanGTP-regulated fashion. RanGTP dissociates Nup153-import receptor complexes, but is required for Nup153-export receptor interactions. We also show that Nup153 is a RanGDP-binding protein, and that the interaction is mediated by the zinc finger region of Nup153. This represents a novel Ran-binding domain, which we term the zinc finger Ran-binding motif. We provide evidence that Nup153 shuttles between the nuclear and cytoplasmic faces of the NPC. The presence of an M9 shuttling domain in Nup153, together with its ability to move within the NPC and to interact with export receptors, suggests that this nucleoporin is a mobile component of the pore which carries export cargos towards the cytoplasm.

Two distinct classes of Ran-binding sites on the nucleoporin Nup-358.

Yaseen NR, Blobel G
Proc Natl Acad Sci U S A. 1999; 96: 5516-21

Nup-358 is a giant nucleoporin located at the tips of the cytoplasmic fibrils of the nuclear pore complex (NPC). Its contains four RBH (RanBP1-homologous) domains and a zinc finger domain with eight zinc finger motifs. Using three recombinant fragments of Nup-358 that comprise two of the RBH domains and the zinc finger domain, we show that both RanGDP and RanGTP bind to Nup-358 in vitro. The RBH domains bound either RanGDP or RanGTP. Interestingly, the zinc finger domain was found to bind RanGDP exclusively. Zinc chelation by EDTA treatment abolished the binding of RanGDP to the zinc finger domain without affecting the binding of Ran to the RBH domain. Ultrastructural studies with RanGDP-conjugated colloidal gold in digitonin-permeabilized cells showed a large number of Ran-binding sites on the cytoplasmic fibrils of the NPC. Of those, only a portion that is closer to the central axis of the NPC was sensitive to RanBP1 competition, suggesting that most of the RBH domains of Nup-358 are situated closer to the central axis of the NPC than the zinc finger domain. Thus, the RBH and the zinc finger domains of Nup-358 were identified as two different classes of Ran-binding sites with distinct, ultrastructural locations at the NPC.