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Mol. Cell. Biol., 04 1995, 2117-2124, Vol 15, No. 4
M Ren, A Villamarin, A Shih, E Coutavas, MS Moore, M LoCurcio, V Clarke, JD Oppenheim, P D'Eustachio and MG Rush
The small Ras-related GTP binding and hydrolyzing protein Ran has been
implicated in a variety of processes, including cell cycle progression, DNA
synthesis, RNA processing, and nuclear-cytosolic trafficking of both RNA
and proteins. Like other small GTPases, Ran appears to function as a
switch: Ran-GTP and Ran-GDP levels are regulated both by guanine nucleotide
exchange factors and GTPase activating proteins, and Ran-GTP and Ran-GDP
interact differentially with one or more effectors. One such putative
effector, Ran-binding protein 1 (RanBP1), interacts selectively with
Ran-GTP. Ran proteins contain a diagnostic short, acidic, carboxyl-terminal
domain, DEDDDL, which, at least in the case of human Ran, is required for
its role in cell cycle regulation. We show here that this domain is
required for the interaction between Ran and RanBP1 but not for the
interaction between Ran and a Ran guanine nucleotide exchange factor or
between Ran and a Ran GTPase activating protein. In addition, Ran lacking
this carboxyl-terminal domain functions normally in an in vitro nuclear
protein import assay. We also show that RanBP1 interacts with the mammalian
homolog of yeast protein RNA1, a protein involved in RNA transport and
processing. These results are consistent with the hypothesis that Ran
functions directly in at least two pathways, one, dependent on RanBP1, that
affects cell cycle progression and RNA export, and another, independent of
RanBP1, that affects nuclear protein import.
Copyright © 1995, American Society for Microbiology
Separate domains of the Ran GTPase interact with different factors to regulate nuclear protein import and RNA processing
Department of Cell Biology, New York University Medical Center, New York 10016.
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