Nucleocytoplasmic transport is mediated by large supramolecular structures
that span the nuclear envelope called nuclear pore complexes (NPC). The export
as well as the import pathway require three major component, the substrate, an
adaptor complex and a receptor. The adaptor complex and the receptor pass
through the NPC with the substrate. The nuclear transport is also dependent on
the GTPase cycle of the small GTPase protein Ran and a number of Ran-binding
proteins (RanBP) [1,2].
RanBP2 is one of these proteins located in the NPC on the cytoplasmic side of
the ring. The function of RanBP2 is not yet well understood. It could function
in coupling RanGTP hydrolysis to NPC translocation through its Ran binding
domain (RanBD1) (see <PDOC50196>) [3,4]. RanBP2 contains also a cluster of
zinc fingers, the RanBP2 zinc fingers. It has been shown that these zinc
fingers bind RanGDP (but not RanGTP)  and the exportin-1 protein (a
receptor of the export pathway) .
The RanBP2 zinc finger is also found in different proteins that are mainly
involved in nuclear transport or localized to the nuclear envelope. Some of
the proteins containing such a domain are listed below.
Mammalian RanBP2/Nup358 protein. Implicated in nuclear import and export
processes (8 copies).
Human MDM2, play a central role in P53 regulation. MDM2 binds to P53 in the
nucleus and the complexe is transported to the cytoplasm via a signal in
MDM2 (1 copy).
Human EWS protein. May play a role in the tumorigenic process. It may
disturb gene expression by mimicking, or interfering with the normal
function of CTD-polII within the transcription initiation complex (1 copy).
FUS, probable RNA-binding protein. Exhibits diffuse staining throughout the
nucleus (excluding nucleoli), together with a small number of intensely
stained focal points, or granules, and punctate staining along the nuclear
envelope (1 copy).
Human nuclear pore complex protein Nup153. Possible DNA-binding subunit of
the nuclear pore complex (NPC). Located to the terminal ring structure
of nucleoplasmic cage (4 copies).
Yeast asparagine-rich protein 1 (ARP1). Protein of unknown function
The RanBP2 zinc finger contains 4 cysteines and a conserved tryptophan
upstream of the zinc finger. Our pattern starts with this tryptophan and
includes the 4 cysteines. We have also developed a profile that covers a
region slightly bigger than the zinc finger.
May 2002 / Text revised.
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